{"history":[{"id":"1023062f-f3a1-496a-9a2d-a31c4951da9a","wordChanged":"assembly","newWord":":::summary\n:::\n\n# \nIn [biology](https://bliptext.com/articles/biology), **tissue** is an kleenex of similar cells and their [extracellular matrix](https://bliptext.com/articles/extracellular-matrix) from the same [embryonic](https://bliptext.com/articles/embryo) origin that together carry out a specific function.\nTissues occupy a [biological organizational level](https://bliptext.com/articles/biological-[organ](https://bliptext.com/articles/organ-biology)isation) between [cells](https://bliptext.com/articles/cell-biology) and a complete [organ](https://bliptext.com/articles/organ-biology).\nAccordingly, organs are formed by the functional grouping together of multiple tissues.\n[Biological](https://bliptext.com/articles/biological) organisms follow this [hierarchy](https://bliptext.com/articles/hierarchy):\n[Cells](https://bliptext.com/articles/cell-biology) < Tissue < [Organ](https://bliptext.com/articles/organ-biology) < [Organ](https://bliptext.com/articles/organ-biology) System < [Organ](https://bliptext.com/articles/organ-biology)ism\nThe English word \"tissue\" [derives](https://bliptext.com/articles/morphological-derivation) from the French word \"\", the past participle of the verb tisser, \"to weave\".\nThe study of tissues is known as [histology](https://bliptext.com/articles/histology) or, in connection with disease, as [histopathology](https://bliptext.com/articles/histopathology).\n[Xavier Bichat](https://bliptext.com/articles/xavier-bichat) is considered as the \"Father of Histology\".\nPlant histology is [studied](https://bliptext.com/articles/studied-space-shuttle-designs) in both [plant anatomy](https://bliptext.com/articles/plant-anatomy) and [physiology](https://bliptext.com/articles/plant-physiology).\nThe classical tools for studying tissues are the [paraffin block](https://bliptext.com/articles/microtome) in which tissue is embedded and then sectioned, the [histological stain](https://bliptext.com/articles/staining), and the [optical microscope](https://bliptext.com/articles/microscope).\nDevelopments in [electron microscopy](https://bliptext.com/articles/electron-microscopy), [immunofluorescence](https://bliptext.com/articles/immunofluorescence), and the use of [frozen tissue-sections](https://bliptext.com/articles/microtome) have enhanced the detail that can be observed in tissues.\nWith these tools, the classical appearances of tissues can be examined in health and [disease](https://bliptext.com/articles/disease), enabling considerable refinement of [medical diagnosis](https://bliptext.com/articles/medical-diagnosis) and [prognosis](https://bliptext.com/articles/prognosis).\n# [Microscopic view of a histologic specimen of human lung, consisting of various tissues: blood, connective tissue, vascular endothelium and respiratory epithelium, stained with hematoxylin and eosin. | upload.wikimedia.org/wikipedia/commons/8/86/Emphysema///H///and///E.jpg]\n\n# Plant tissue\nIn [plant anatomy](https://bliptext.com/articles/plant-anatomy), tissues are categorized broadly into three tissue systems: the [epidermis](https://bliptext.com/articles/epidermis-botany), the [ground tissue](https://bliptext.com/articles/ground-tissue), and the [vascular tissue](https://bliptext.com/articles/vascular-tissue).\nPlant tissues can also be divided differently into two types:\n# [Cross-section of a flax plant stem with several layers of different tissue types: | upload.wikimedia.org/wikipedia/commons/9/92/Stem-histology-cross-section-tag.svg]\n\n## Meristematic tissue\n[Meristematic tissue](https://bliptext.com/articles/meristem) consists of actively dividing cells and leads to increase in length and thickness of the plant.\nThe primary growth of a plant occurs only in certain specific regions, such as in the tips of stems or roots.\nIt is in these regions that meristematic tissue is present.\nCells of this type of tissue are roughly spherical or polyhedral to rectangular in shape, with thin [cell walls](https://bliptext.com/articles/cell-wall).\nNew cells produced by meristem are initially those of meristem itself, but as the new cells grow and mature, their characteristics slowly change and they become differentiated as components of meristematic tissue, being classified as:\nThere are two types of meristematic Tissue\n1.Primary meristem.\n2.Secondary meristem.\nThe cells of meristematic tissue are similar in structure and have a thin and elastic primary cell wall made of [cellulose](https://bliptext.com/articles/cellulose).\nThey are compactly arranged without inter-cellular spaces between them.\nEach cell contains a dense [cytoplasm](https://bliptext.com/articles/cytoplasm) and a prominent [cell nucleus](https://bliptext.com/articles/cell-nucleus).\nThe dense [protoplasm](https://bliptext.com/articles/protoplasm) of meristematic cells contains very few [vacuoles](https://bliptext.com/articles/vacuole).\nNormally the meristematic cells are oval, [polygonal](https://bliptext.com/articles/polygon), or [rectangular](https://bliptext.com/articles/rectangular) in shape.\nMeristematic tissue cells have a large nucleus with small or no vacuoles because they have no need to store anything, as opposed to their function of multiplying and increasing the girth and length of the plant, with no intercellular spaces.\n\n## Permanent tissues\nPermanent tissues may be defined as a group of living or dead cells formed by meristematic tissue and have lost their ability to divide and have permanently placed at fixed positions in the plant body.\nMeristematic tissues that take up a specific role lose the ability to divide.\nThis process of taking up a permanent shape, size and a function is called [cellular differentiation](https://bliptext.com/articles/cellular-differentiation).\nCells of meristematic tissue differentiate to form different types of permanent tissues.\nThere are 2 types of permanent tissues:\n\n### Simple permanent tissue\nSimple permanent tissue is a group of cells which are similar in origin, structure, and function.\nThey are of three types:\n\n#### Parenchyma\n[Parenchyma](https://bliptext.com/articles/parenchyma) (Greek, para – 'beside'; enchyma– infusion – 'tissue') is the bulk of a substance.\nIn plants, it consists of relatively unspecialized living cells with thin cell walls that are usually loosely packed so that intercellular spaces are found between cells of this tissue.\nThese are generally isodiametric, in shape.\nThey contain small number of vacuoles or sometimes they even may not contain any vacuole.\nEven if they do so the vacuole is of much smaller size than of normal animal cells.\nThis tissue provides support to plants and also stores food.\n[Chlorenchyma](https://bliptext.com/articles/chlorenchyma) is a special type of parenchyma that contains [chlorophyll](https://bliptext.com/articles/chlorophyll) and performs photosynthesis.\nIn aquatic plants, [aerenchyma](https://bliptext.com/articles/aerenchyma) tissues, or large air cavities, give support to float on water by making them buoyant.\nParenchyma cells called idioblasts have metabolic waste.\nSpindle shaped fibers are also present in this cell to support them and known as prosenchyma, succulent parenchyma also noted.\nIn [xerophytes](https://bliptext.com/articles/xerophytes), parenchyma tissues store water.\n\n#### Collenchyma\n[Collenchyma](https://bliptext.com/articles/collenchyma) (Greek, 'Colla' means gum and 'enchyma' means infusion) is a living tissue of primary body like [Parenchyma](https://bliptext.com/articles/parenchyma).\nCells are thin-walled but possess thickening of [cellulose](https://bliptext.com/articles/cellulose), water and [pectin](https://bliptext.com/articles/pectin) substances (pecto[cellulose](https://bliptext.com/articles/cellulose)) at the corners where a number of cells join.\nThis tissue gives tensile strength to the plant and the cells are compactly arranged and have very little inter-cellular spaces.\nIt occurs chiefly in [hypodermis](https://bliptext.com/articles/hypodermis) of stems and leaves.\nIt is absent in [monocots](https://bliptext.com/articles/monocots) and in roots.\nCollenchymatous tissue acts as a supporting tissue in stems of young plants.\nIt provides mechanical support, elasticity, and tensile strength to the plant body.\nIt helps in manufacturing sugar and storing it as starch.\nIt is present in the margin of leaves and resists tearing effect of the wind.\n# [Cross section of collenchyma cells | upload.wikimedia.org/wikipedia/commons/9/97/Plant///cell///type///collenchyma.png]\n\n#### Sclerenchyma\n[Sclerenchyma](https://bliptext.com/articles/ground-tissue) (Greek, Sclerous means hard and enchyma means infusion) consists of thick-walled, dead cells and protoplasm is negligible.\nThese cells have hard and extremely thick secondary walls due to uniform distribution and high secretion of [lignin](https://bliptext.com/articles/lignin) and have a function of providing mechanical support.\nThey do not have inter-cellular spaces between them.\nLignin deposition is so thick that the cell walls become stronger, rigid and impermeable to water, which are also known as a stone cells or sclereids.\nThese tissues are mainly of two types: sclerenchyma fiber and sclereids.\nSclerenchyma fiber cells have a narrow lumen and are long, narrow and unicellular.\nFibers are elongated cells that are strong and flexible, often used in ropes.\nSclereids have extremely thick cell walls and are brittle, and are found in nutshells and legumes.\n\n#### Epidermis\nThe entire surface of the plant consists of a single layer of cells called epidermis or surface tissue.\nThe entire surface of the plant has this outer layer of the epidermis.\nHence it is also called surface tissue.\nMost of the epidermal cells are relatively flat.\nThe outer and lateral walls of the cell are often thicker than the inner walls.\nThe cells form a continuous sheet without intercellular spaces.\nIt protects all parts of the plant.\nThe outer epidermis is coated with a waxy thick layer called cutin which prevents loss of water.\nThe epidermis also consists of [stomata](https://bliptext.com/articles/stomata) (singular:stoma) which helps in [transpiration](https://bliptext.com/articles/transpiration).\n\n### Complex permanent tissue\nThe complex permanent tissue consists of more than one type of cells having a common origin which work together as a unit.\nComplex tissues are mainly concerned with the transportation of mineral nutrients, organic solutes (food materials), and water.\nThat's why it is also known as conducting and vascular tissue.\nThe common types of complex permanent tissue are:\nXylem and phloem together form vascular bundles.\n\n#### Xylem\n[Xylem](https://bliptext.com/articles/xylem) (Greek, xylos = wood) serves as a chief conducting tissue of vascular plants.\nIt is responsible for the conduction of water and inorganic solutes.\nXylem consists of four kinds of cells:\nXylem tissue is organised in a tube-like fashion along the main axes of stems and roots.\nIt consists of a combination of parenchyma cells, fibers, vessels, tracheids, and ray cells.\nLonger tubes made up of individual cellssels tracheids, while vessel members are open at each end.\nInternally, there may be bars of wall material extending across the open space.\nThese cells are joined end to end to form long tubes.\nVessel members and tracheids are dead at maturity.\nTracheids have thick secondary cell walls and are tapered at the ends.\nThey do not have end openings such as the vessels.\nThe end overlap with each other, with pairs of pits present.\nThe pit pairs allow water to pass from cell to cell.\nThough most conduction in xylem tissue is vertical, lateral conduction along the diameter of a stem is facilitated via rays.\nRays are horizontal rows of long-living parenchyma cells that arise out of the vascular cambium.\n# [Cross section of 2-year-old Tilia americana, highlighting xylem ray shape and orientation | upload.wikimedia.org/wikipedia/commons/4/4e/Xylem///rays///%28Tilia///Americana%29.jpg]\n\n#### Phloem\n[Phloem](https://bliptext.com/articles/phloem) consists of:\nPhloem is an equally important plant tissue as it also is part of the 'plumbing system' of a plant.\nPrimarily, phloem carries dissolved food substances throughout the plant.\nThis conduction system is composed of sieve-tube member and companion cells, that are without secondary walls.\nThe parent cells of the vascular cambium produce both xylem and phloem.\nThis usually also includes fibers, parenchyma and ray cells.\nSieve tubes are formed from sieve-tube members laid end to end.\nThe end walls, unlike vessel members in xylem, do not have openings.\nThe end walls, however, are full of small pores where cytoplasm extends from cell to cell.\nThese porous connections are called sieve plates.\nIn spite of the fact that their cytoplasm is actively involved in the conduction of food materials, sieve-tube members do not have nuclei at maturity.\nIt is the companion cells that are nestled between sieve-tube members that function in some manner bringing about the conduction of food.\nSieve-tube members that are alive contain a polymer called callose, a carbohydrate polymer, forming the callus pad/callus, the colourless substance that covers the sieve plate.\nCallose stays in solution as long as the cell contents are under pressure.\nPhloem transports food and materials in plants upwards and downwards as required.\n\n# Animal tissue\nAnimal tissues are grouped into four basic types: [connective](https://bliptext.com/articles/connective-tissue), [muscle](https://bliptext.com/articles/muscle-tissue), [nervous](https://bliptext.com/articles/nervous-tissue), and [epithelial](https://bliptext.com/articles/epithelium).\nCollections of tissues joined in units to serve a common function compose organs.\nWhile most animals can generally be considered to contain the four tissue types, the manifestation of these tissues can differ depending on the type of organism.\nFor example, the origin of the cells comprising a particular tissue type may differ developmentally for different classifications of animals.\nTissue appeared for the first time in the [diploblasts](https://bliptext.com/articles/eumetazoa), but modern forms only appeared in [triploblasts](https://bliptext.com/articles/triploblasts).\nThe epithelium in all animals is derived from the [ectoderm](https://bliptext.com/articles/ectoderm) and [endoderm](https://bliptext.com/articles/endoderm) (or their precursor in [sponges](https://bliptext.com/articles/sponges)), with a small contribution from the [mesoderm](https://bliptext.com/articles/mesoderm), forming the [endothelium](https://bliptext.com/articles/endothelium), a specialized type of epithelium that composes the [vasculature](https://bliptext.com/articles/blood-vessels).\nBy contrast, a true [epithelial tissue](https://bliptext.com/articles/epithelial-tissue) is present only in a single layer of cells held together via occluding junctions called [tight junctions](https://bliptext.com/articles/tight-junctions), to create a selectively permeable barrier.\nThis tissue covers all organismal surfaces that come in contact with the external environment such as the [skin](https://bliptext.com/articles/skin), the airways, and the digestive tract.\nIt serves functions of protection, [secretion](https://bliptext.com/articles/secretion), and absorption, and is separated from other tissues below by a [basal lamina](https://bliptext.com/articles/basal-lamina).\nThe connective tissue and the muscular are derived from the mesoderm.\nThe nervous tissue is derived from the ectoderm.\n\n## Epithelial tissues\nThe epithelial tissues are formed by cells that cover the organ surfaces, such as the surface of [skin](https://bliptext.com/articles/skin), the [airways](https://bliptext.com/articles/airway), surfaces of soft organs, the [reproductive tract](https://bliptext.com/articles/reproductive-tract), and the inner lining of the [digestive tract](https://bliptext.com/articles/digestive-tract).\nThe cells comprising an epithelial layer are linked via semi-permeable, [tight junctions](https://bliptext.com/articles/tight-junctions); hence, this tissue provides a barrier between the external environment and the organ it covers.\nIn addition to this protective function, epithelial tissue may also be specialized to function in [secretion](https://bliptext.com/articles/secretion), [excretion](https://bliptext.com/articles/excretion) and [absorption](https://bliptext.com/articles/digestion).\nEpithelial tissue helps to protect organs from microorganisms, injury, and fluid loss.\nFunctions of epithelial tissue:\nThere are many kinds of epithelium, and nomenclature is somewhat variable.\nMost classification schemes combine a description of the cell-shape in the upper layer of the epithelium with a word denoting the number of layers: either simple (one layer of cells) or stratified (multiple layers of cells).\nHowever, other cellular features such as cilia may also be described in the classification system.\nSome common kinds of epithelium are listed below:\n\n## Connective tissue\nConnective tissues are made up of cells separated by non-living material, which is called an [extracellular matrix](https://bliptext.com/articles/extracellular-matrix).\nThis matrix can be liquid or rigid.\nFor example, blood contains plasma as its matrix and bone's matrix is rigid.\nConnective tissue gives shape to organs and holds them in place.\nBlood, bone, tendon, ligament, adipose, and areolar tissues are examples of connective tissues.\nOne method of classifying connective tissues is to divide them into three types: fibrous connective tissue, skeletal connective tissue, and fluid connective tissue.\n\n## Muscle tissue\n[Muscle cells](https://bliptext.com/articles/muscle-cell) (myocytes) form the active contractile tissue of the body.\n[Muscle tissue](https://bliptext.com/articles/muscle-tissue) functions to produce force and cause motion, either [locomotion](https://bliptext.com/articles/animal-locomotion) or movement within internal organs.\nMuscle is formed of contractile [filaments](https://bliptext.com/articles/myofilament) and is separated into three main types; [smooth muscle](https://bliptext.com/articles/smooth-muscle), [skeletal muscle](https://bliptext.com/articles/skeletal-muscle) and [cardiac muscle](https://bliptext.com/articles/cardiac-muscle).\nSmooth muscle has no [striations](https://bliptext.com/articles/striated-muscle-tissue) when examined microscopically.\nIt contracts slowly but maintains contractibility over a wide range of stretch lengths.\nIt is found in such organs as [sea anemone](https://bliptext.com/articles/sea-anemone) tentacles and the body wall of [sea cucumbers](https://bliptext.com/articles/sea-cucumber).\nSkeletal muscle contracts rapidly but has a limited range of extension.\nIt is found in the movement of appendages and jaws.\nObliquely striated muscle is intermediate between the other two.\nThe filaments are staggered and this is the type of muscle found in [earthworms](https://bliptext.com/articles/earthworm) that can extend slowly or make rapid contractions.\nIn higher animals striated muscles occur in bundles attached to bone to provide movement and are often arranged in antagonistic sets.\nSmooth muscle is found in the walls of the [uterus](https://bliptext.com/articles/uterus), [bladder](https://bliptext.com/articles/bladder), [intestines](https://bliptext.com/articles/intestines), [stomach](https://bliptext.com/articles/stomach), [oesophagus](https://bliptext.com/articles/oesophagus), [respiratory airways](https://bliptext.com/articles/respiratory-airways), and [blood vessels](https://bliptext.com/articles/blood-vessel).\nCardiac muscle is found only in the [heart](https://bliptext.com/articles/heart), allowing it to contract and pump blood through the body.\n# [Cross section through skeletal muscle and a small nerve at high magnification (H&E stain) | upload.wikimedia.org/wikipedia/commons/c/c3/Skeletal///muscle///-///cross///section%2C///nerve///bundle.jpg]\n\n## Nervous tissue\nCells comprising the [central nervous system](https://bliptext.com/articles/central-nervous-system) and [peripheral nervous system](https://bliptext.com/articles/peripheral-nervous-system) are classified as nervous (or neural) tissue.\nIn the central nervous system, neural tissues form the [brain](https://bliptext.com/articles/brain) and [spinal cord](https://bliptext.com/articles/spinal-cord).\nIn the peripheral nervous system, neural tissues form the [cranial nerves](https://bliptext.com/articles/cranial-nerves) and [spinal nerves](https://bliptext.com/articles/spinal-nerve), inclusive of the [motor neurons](https://bliptext.com/articles/motor-neuron).\n\n## Mineralized tissues\nMineralized tissues are biological tissues that incorporate minerals into soft matrices.\nSuch tissues may be found in both plants and animals.\n\n# History\n[Xavier Bichat](https://bliptext.com/articles/xavier-bichat) introduced the word tissue into the study of [anatomy](https://bliptext.com/articles/anatomy) by 1801.\nHe was \"the first to propose that tissue is a central element in [human anatomy](https://bliptext.com/articles/human-anatomy), and he considered [organs](https://bliptext.com/articles/organ-anatomy) as collections of often disparate tissues, rather than as entities in themselves\".\nAlthough he worked without a [microscope](https://bliptext.com/articles/microscope), Bichat distinguished 21 types of elementary tissues from which the organs of the human body are composed, a number later reduced by other authors.\n# [Xavier Bichat (1771–1802) | upload.wikimedia.org/wikipedia/commons/7/7f/Pierre-Maximilien///Delafontaine///-///Portrait///of///Marie///Fran%C3%A7ois///Xavier///Bichat.jpg]\n\n# Sources","wordIndex":7,"createdAt":"2025-06-02T11:14:38.078Z","user":{"id":"Sod1RgkFJjoA8Kmcd4MQdosFQFkJkA5h","name":"nunya bussiness","image":"https://lh3.googleusercontent.com/a/ACg8ocKsNYjuvoMypB_YErOMobChE-Vy-6gXZ2tfxVRJrhNYnyVvkg=s96-c"}}],"article":{"id":"5ac7433a-1834-4430-8b5e-00dbecc2040a","title":"Tissue (biology)","slug":"tissue-biology","content":":::summary\n:::\n\n# \nIn [biology](https://bliptext.com/articles/biology), **tissue** is an kleenex of similar cells and their [extracellular matrix](https://bliptext.com/articles/extracellular-matrix) from the same [embryonic](https://bliptext.com/articles/embryo) origin that together carry out a specific function.\nTissues occupy a [biological organizational level](https://bliptext.com/articles/biological-[organ](https://bliptext.com/articles/organ-biology)isation) between [cells](https://bliptext.com/articles/cell-biology) and a complete [organ](https://bliptext.com/articles/organ-biology).\nAccordingly, organs are formed by the functional grouping together of multiple tissues.\n[Biological](https://bliptext.com/articles/biological) organisms follow this [hierarchy](https://bliptext.com/articles/hierarchy):\n[Cells](https://bliptext.com/articles/cell-biology) < Tissue < [Organ](https://bliptext.com/articles/organ-biology) < [Organ](https://bliptext.com/articles/organ-biology) System < [Organ](https://bliptext.com/articles/organ-biology)ism\nThe English word \"tissue\" [derives](https://bliptext.com/articles/morphological-derivation) from the French word \"\", the past participle of the verb tisser, \"to weave\".\nThe study of tissues is known as [histology](https://bliptext.com/articles/histology) or, in connection with disease, as [histopathology](https://bliptext.com/articles/histopathology).\n[Xavier Bichat](https://bliptext.com/articles/xavier-bichat) is considered as the \"Father of Histology\".\nPlant histology is [studied](https://bliptext.com/articles/studied-space-shuttle-designs) in both [plant anatomy](https://bliptext.com/articles/plant-anatomy) and [physiology](https://bliptext.com/articles/plant-physiology).\nThe classical tools for studying tissues are the [paraffin block](https://bliptext.com/articles/microtome) in which tissue is embedded and then sectioned, the [histological stain](https://bliptext.com/articles/staining), and the [optical microscope](https://bliptext.com/articles/microscope).\nDevelopments in [electron microscopy](https://bliptext.com/articles/electron-microscopy), [immunofluorescence](https://bliptext.com/articles/immunofluorescence), and the use of [frozen tissue-sections](https://bliptext.com/articles/microtome) have enhanced the detail that can be observed in tissues.\nWith these tools, the classical appearances of tissues can be examined in health and [disease](https://bliptext.com/articles/disease), enabling considerable refinement of [medical diagnosis](https://bliptext.com/articles/medical-diagnosis) and [prognosis](https://bliptext.com/articles/prognosis).\n# [Microscopic view of a histologic specimen of human lung, consisting of various tissues: blood, connective tissue, vascular endothelium and respiratory epithelium, stained with hematoxylin and eosin. | upload.wikimedia.org/wikipedia/commons/8/86/Emphysema///H///and///E.jpg]\n\n# Plant tissue\nIn [plant anatomy](https://bliptext.com/articles/plant-anatomy), tissues are categorized broadly into three tissue systems: the [epidermis](https://bliptext.com/articles/epidermis-botany), the [ground tissue](https://bliptext.com/articles/ground-tissue), and the [vascular tissue](https://bliptext.com/articles/vascular-tissue).\nPlant tissues can also be divided differently into two types:\n# [Cross-section of a flax plant stem with several layers of different tissue types: | upload.wikimedia.org/wikipedia/commons/9/92/Stem-histology-cross-section-tag.svg]\n\n## Meristematic tissue\n[Meristematic tissue](https://bliptext.com/articles/meristem) consists of actively dividing cells and leads to increase in length and thickness of the plant.\nThe primary growth of a plant occurs only in certain specific regions, such as in the tips of stems or roots.\nIt is in these regions that meristematic tissue is present.\nCells of this type of tissue are roughly spherical or polyhedral to rectangular in shape, with thin [cell walls](https://bliptext.com/articles/cell-wall).\nNew cells produced by meristem are initially those of meristem itself, but as the new cells grow and mature, their characteristics slowly change and they become differentiated as components of meristematic tissue, being classified as:\nThere are two types of meristematic Tissue\n1.Primary meristem.\n2.Secondary meristem.\nThe cells of meristematic tissue are similar in structure and have a thin and elastic primary cell wall made of [cellulose](https://bliptext.com/articles/cellulose).\nThey are compactly arranged without inter-cellular spaces between them.\nEach cell contains a dense [cytoplasm](https://bliptext.com/articles/cytoplasm) and a prominent [cell nucleus](https://bliptext.com/articles/cell-nucleus).\nThe dense [protoplasm](https://bliptext.com/articles/protoplasm) of meristematic cells contains very few [vacuoles](https://bliptext.com/articles/vacuole).\nNormally the meristematic cells are oval, [polygonal](https://bliptext.com/articles/polygon), or [rectangular](https://bliptext.com/articles/rectangular) in shape.\nMeristematic tissue cells have a large nucleus with small or no vacuoles because they have no need to store anything, as opposed to their function of multiplying and increasing the girth and length of the plant, with no intercellular spaces.\n\n## Permanent tissues\nPermanent tissues may be defined as a group of living or dead cells formed by meristematic tissue and have lost their ability to divide and have permanently placed at fixed positions in the plant body.\nMeristematic tissues that take up a specific role lose the ability to divide.\nThis process of taking up a permanent shape, size and a function is called [cellular differentiation](https://bliptext.com/articles/cellular-differentiation).\nCells of meristematic tissue differentiate to form different types of permanent tissues.\nThere are 2 types of permanent tissues:\n\n### Simple permanent tissue\nSimple permanent tissue is a group of cells which are similar in origin, structure, and function.\nThey are of three types:\n\n#### Parenchyma\n[Parenchyma](https://bliptext.com/articles/parenchyma) (Greek, para – 'beside'; enchyma– infusion – 'tissue') is the bulk of a substance.\nIn plants, it consists of relatively unspecialized living cells with thin cell walls that are usually loosely packed so that intercellular spaces are found between cells of this tissue.\nThese are generally isodiametric, in shape.\nThey contain small number of vacuoles or sometimes they even may not contain any vacuole.\nEven if they do so the vacuole is of much smaller size than of normal animal cells.\nThis tissue provides support to plants and also stores food.\n[Chlorenchyma](https://bliptext.com/articles/chlorenchyma) is a special type of parenchyma that contains [chlorophyll](https://bliptext.com/articles/chlorophyll) and performs photosynthesis.\nIn aquatic plants, [aerenchyma](https://bliptext.com/articles/aerenchyma) tissues, or large air cavities, give support to float on water by making them buoyant.\nParenchyma cells called idioblasts have metabolic waste.\nSpindle shaped fibers are also present in this cell to support them and known as prosenchyma, succulent parenchyma also noted.\nIn [xerophytes](https://bliptext.com/articles/xerophytes), parenchyma tissues store water.\n\n#### Collenchyma\n[Collenchyma](https://bliptext.com/articles/collenchyma) (Greek, 'Colla' means gum and 'enchyma' means infusion) is a living tissue of primary body like [Parenchyma](https://bliptext.com/articles/parenchyma).\nCells are thin-walled but possess thickening of [cellulose](https://bliptext.com/articles/cellulose), water and [pectin](https://bliptext.com/articles/pectin) substances (pecto[cellulose](https://bliptext.com/articles/cellulose)) at the corners where a number of cells join.\nThis tissue gives tensile strength to the plant and the cells are compactly arranged and have very little inter-cellular spaces.\nIt occurs chiefly in [hypodermis](https://bliptext.com/articles/hypodermis) of stems and leaves.\nIt is absent in [monocots](https://bliptext.com/articles/monocots) and in roots.\nCollenchymatous tissue acts as a supporting tissue in stems of young plants.\nIt provides mechanical support, elasticity, and tensile strength to the plant body.\nIt helps in manufacturing sugar and storing it as starch.\nIt is present in the margin of leaves and resists tearing effect of the wind.\n# [Cross section of collenchyma cells | upload.wikimedia.org/wikipedia/commons/9/97/Plant///cell///type///collenchyma.png]\n\n#### Sclerenchyma\n[Sclerenchyma](https://bliptext.com/articles/ground-tissue) (Greek, Sclerous means hard and enchyma means infusion) consists of thick-walled, dead cells and protoplasm is negligible.\nThese cells have hard and extremely thick secondary walls due to uniform distribution and high secretion of [lignin](https://bliptext.com/articles/lignin) and have a function of providing mechanical support.\nThey do not have inter-cellular spaces between them.\nLignin deposition is so thick that the cell walls become stronger, rigid and impermeable to water, which are also known as a stone cells or sclereids.\nThese tissues are mainly of two types: sclerenchyma fiber and sclereids.\nSclerenchyma fiber cells have a narrow lumen and are long, narrow and unicellular.\nFibers are elongated cells that are strong and flexible, often used in ropes.\nSclereids have extremely thick cell walls and are brittle, and are found in nutshells and legumes.\n\n#### Epidermis\nThe entire surface of the plant consists of a single layer of cells called epidermis or surface tissue.\nThe entire surface of the plant has this outer layer of the epidermis.\nHence it is also called surface tissue.\nMost of the epidermal cells are relatively flat.\nThe outer and lateral walls of the cell are often thicker than the inner walls.\nThe cells form a continuous sheet without intercellular spaces.\nIt protects all parts of the plant.\nThe outer epidermis is coated with a waxy thick layer called cutin which prevents loss of water.\nThe epidermis also consists of [stomata](https://bliptext.com/articles/stomata) (singular:stoma) which helps in [transpiration](https://bliptext.com/articles/transpiration).\n\n### Complex permanent tissue\nThe complex permanent tissue consists of more than one type of cells having a common origin which work together as a unit.\nComplex tissues are mainly concerned with the transportation of mineral nutrients, organic solutes (food materials), and water.\nThat's why it is also known as conducting and vascular tissue.\nThe common types of complex permanent tissue are:\nXylem and phloem together form vascular bundles.\n\n#### Xylem\n[Xylem](https://bliptext.com/articles/xylem) (Greek, xylos = wood) serves as a chief conducting tissue of vascular plants.\nIt is responsible for the conduction of water and inorganic solutes.\nXylem consists of four kinds of cells:\nXylem tissue is organised in a tube-like fashion along the main axes of stems and roots.\nIt consists of a combination of parenchyma cells, fibers, vessels, tracheids, and ray cells.\nLonger tubes made up of individual cellssels tracheids, while vessel members are open at each end.\nInternally, there may be bars of wall material extending across the open space.\nThese cells are joined end to end to form long tubes.\nVessel members and tracheids are dead at maturity.\nTracheids have thick secondary cell walls and are tapered at the ends.\nThey do not have end openings such as the vessels.\nThe end overlap with each other, with pairs of pits present.\nThe pit pairs allow water to pass from cell to cell.\nThough most conduction in xylem tissue is vertical, lateral conduction along the diameter of a stem is facilitated via rays.\nRays are horizontal rows of long-living parenchyma cells that arise out of the vascular cambium.\n# [Cross section of 2-year-old Tilia americana, highlighting xylem ray shape and orientation | upload.wikimedia.org/wikipedia/commons/4/4e/Xylem///rays///%28Tilia///Americana%29.jpg]\n\n#### Phloem\n[Phloem](https://bliptext.com/articles/phloem) consists of:\nPhloem is an equally important plant tissue as it also is part of the 'plumbing system' of a plant.\nPrimarily, phloem carries dissolved food substances throughout the plant.\nThis conduction system is composed of sieve-tube member and companion cells, that are without secondary walls.\nThe parent cells of the vascular cambium produce both xylem and phloem.\nThis usually also includes fibers, parenchyma and ray cells.\nSieve tubes are formed from sieve-tube members laid end to end.\nThe end walls, unlike vessel members in xylem, do not have openings.\nThe end walls, however, are full of small pores where cytoplasm extends from cell to cell.\nThese porous connections are called sieve plates.\nIn spite of the fact that their cytoplasm is actively involved in the conduction of food materials, sieve-tube members do not have nuclei at maturity.\nIt is the companion cells that are nestled between sieve-tube members that function in some manner bringing about the conduction of food.\nSieve-tube members that are alive contain a polymer called callose, a carbohydrate polymer, forming the callus pad/callus, the colourless substance that covers the sieve plate.\nCallose stays in solution as long as the cell contents are under pressure.\nPhloem transports food and materials in plants upwards and downwards as required.\n\n# Animal tissue\nAnimal tissues are grouped into four basic types: [connective](https://bliptext.com/articles/connective-tissue), [muscle](https://bliptext.com/articles/muscle-tissue), [nervous](https://bliptext.com/articles/nervous-tissue), and [epithelial](https://bliptext.com/articles/epithelium).\nCollections of tissues joined in units to serve a common function compose organs.\nWhile most animals can generally be considered to contain the four tissue types, the manifestation of these tissues can differ depending on the type of organism.\nFor example, the origin of the cells comprising a particular tissue type may differ developmentally for different classifications of animals.\nTissue appeared for the first time in the [diploblasts](https://bliptext.com/articles/eumetazoa), but modern forms only appeared in [triploblasts](https://bliptext.com/articles/triploblasts).\nThe epithelium in all animals is derived from the [ectoderm](https://bliptext.com/articles/ectoderm) and [endoderm](https://bliptext.com/articles/endoderm) (or their precursor in [sponges](https://bliptext.com/articles/sponges)), with a small contribution from the [mesoderm](https://bliptext.com/articles/mesoderm), forming the [endothelium](https://bliptext.com/articles/endothelium), a specialized type of epithelium that composes the [vasculature](https://bliptext.com/articles/blood-vessels).\nBy contrast, a true [epithelial tissue](https://bliptext.com/articles/epithelial-tissue) is present only in a single layer of cells held together via occluding junctions called [tight junctions](https://bliptext.com/articles/tight-junctions), to create a selectively permeable barrier.\nThis tissue covers all organismal surfaces that come in contact with the external environment such as the [skin](https://bliptext.com/articles/skin), the airways, and the digestive tract.\nIt serves functions of protection, [secretion](https://bliptext.com/articles/secretion), and absorption, and is separated from other tissues below by a [basal lamina](https://bliptext.com/articles/basal-lamina).\nThe connective tissue and the muscular are derived from the mesoderm.\nThe nervous tissue is derived from the ectoderm.\n\n## Epithelial tissues\nThe epithelial tissues are formed by cells that cover the organ surfaces, such as the surface of [skin](https://bliptext.com/articles/skin), the [airways](https://bliptext.com/articles/airway), surfaces of soft organs, the [reproductive tract](https://bliptext.com/articles/reproductive-tract), and the inner lining of the [digestive tract](https://bliptext.com/articles/digestive-tract).\nThe cells comprising an epithelial layer are linked via semi-permeable, [tight junctions](https://bliptext.com/articles/tight-junctions); hence, this tissue provides a barrier between the external environment and the organ it covers.\nIn addition to this protective function, epithelial tissue may also be specialized to function in [secretion](https://bliptext.com/articles/secretion), [excretion](https://bliptext.com/articles/excretion) and [absorption](https://bliptext.com/articles/digestion).\nEpithelial tissue helps to protect organs from microorganisms, injury, and fluid loss.\nFunctions of epithelial tissue:\nThere are many kinds of epithelium, and nomenclature is somewhat variable.\nMost classification schemes combine a description of the cell-shape in the upper layer of the epithelium with a word denoting the number of layers: either simple (one layer of cells) or stratified (multiple layers of cells).\nHowever, other cellular features such as cilia may also be described in the classification system.\nSome common kinds of epithelium are listed below:\n\n## Connective tissue\nConnective tissues are made up of cells separated by non-living material, which is called an [extracellular matrix](https://bliptext.com/articles/extracellular-matrix).\nThis matrix can be liquid or rigid.\nFor example, blood contains plasma as its matrix and bone's matrix is rigid.\nConnective tissue gives shape to organs and holds them in place.\nBlood, bone, tendon, ligament, adipose, and areolar tissues are examples of connective tissues.\nOne method of classifying connective tissues is to divide them into three types: fibrous connective tissue, skeletal connective tissue, and fluid connective tissue.\n\n## Muscle tissue\n[Muscle cells](https://bliptext.com/articles/muscle-cell) (myocytes) form the active contractile tissue of the body.\n[Muscle tissue](https://bliptext.com/articles/muscle-tissue) functions to produce force and cause motion, either [locomotion](https://bliptext.com/articles/animal-locomotion) or movement within internal organs.\nMuscle is formed of contractile [filaments](https://bliptext.com/articles/myofilament) and is separated into three main types; [smooth muscle](https://bliptext.com/articles/smooth-muscle), [skeletal muscle](https://bliptext.com/articles/skeletal-muscle) and [cardiac muscle](https://bliptext.com/articles/cardiac-muscle).\nSmooth muscle has no [striations](https://bliptext.com/articles/striated-muscle-tissue) when examined microscopically.\nIt contracts slowly but maintains contractibility over a wide range of stretch lengths.\nIt is found in such organs as [sea anemone](https://bliptext.com/articles/sea-anemone) tentacles and the body wall of [sea cucumbers](https://bliptext.com/articles/sea-cucumber).\nSkeletal muscle contracts rapidly but has a limited range of extension.\nIt is found in the movement of appendages and jaws.\nObliquely striated muscle is intermediate between the other two.\nThe filaments are staggered and this is the type of muscle found in [earthworms](https://bliptext.com/articles/earthworm) that can extend slowly or make rapid contractions.\nIn higher animals striated muscles occur in bundles attached to bone to provide movement and are often arranged in antagonistic sets.\nSmooth muscle is found in the walls of the [uterus](https://bliptext.com/articles/uterus), [bladder](https://bliptext.com/articles/bladder), [intestines](https://bliptext.com/articles/intestines), [stomach](https://bliptext.com/articles/stomach), [oesophagus](https://bliptext.com/articles/oesophagus), [respiratory airways](https://bliptext.com/articles/respiratory-airways), and [blood vessels](https://bliptext.com/articles/blood-vessel).\nCardiac muscle is found only in the [heart](https://bliptext.com/articles/heart), allowing it to contract and pump blood through the body.\n# [Cross section through skeletal muscle and a small nerve at high magnification (H&E stain) | upload.wikimedia.org/wikipedia/commons/c/c3/Skeletal///muscle///-///cross///section%2C///nerve///bundle.jpg]\n\n## Nervous tissue\nCells comprising the [central nervous system](https://bliptext.com/articles/central-nervous-system) and [peripheral nervous system](https://bliptext.com/articles/peripheral-nervous-system) are classified as nervous (or neural) tissue.\nIn the central nervous system, neural tissues form the [brain](https://bliptext.com/articles/brain) and [spinal cord](https://bliptext.com/articles/spinal-cord).\nIn the peripheral nervous system, neural tissues form the [cranial nerves](https://bliptext.com/articles/cranial-nerves) and [spinal nerves](https://bliptext.com/articles/spinal-nerve), inclusive of the [motor neurons](https://bliptext.com/articles/motor-neuron).\n\n## Mineralized tissues\nMineralized tissues are biological tissues that incorporate minerals into soft matrices.\nSuch tissues may be found in both plants and animals.\n\n# History\n[Xavier Bichat](https://bliptext.com/articles/xavier-bichat) introduced the word tissue into the study of [anatomy](https://bliptext.com/articles/anatomy) by 1801.\nHe was \"the first to propose that tissue is a central element in [human anatomy](https://bliptext.com/articles/human-anatomy), and he considered [organs](https://bliptext.com/articles/organ-anatomy) as collections of often disparate tissues, rather than as entities in themselves\".\nAlthough he worked without a [microscope](https://bliptext.com/articles/microscope), Bichat distinguished 21 types of elementary tissues from which the organs of the human body are composed, a number later reduced by other authors.\n# [Xavier Bichat (1771–1802) | upload.wikimedia.org/wikipedia/commons/7/7f/Pierre-Maximilien///Delafontaine///-///Portrait///of///Marie///Fran%C3%A7ois///Xavier///Bichat.jpg]\n\n# Sources","current_revision":"1023062f-f3a1-496a-9a2d-a31c4951da9a","created_by":"kACnuQmH5k9Nr5VNVEpVeg7XpvUmMctD","created_at":"2025-01-25T17:56:10.246Z","updated_at":"2025-06-02T11:14:38.084Z","search_vector":"'biolog':2 'tissu':1","search_content":" \n \n\n# \nIn [biology](https://bliptext.com/articles/biology), **tissue** is an assembly of similar cells and their [extracellular matrix](https://bliptext.com/articles/extracellular-matrix) from the same [embryonic](https://bliptext.com/articles/embryo) origin that together carry out a specific function.\nTissues occupy a [biological [organ](https://bliptext.com/articles/organ-biology)izational level](https://bliptext.com/articles/biological-[organ](https://bliptext.com/articles/organ-biology)isation) between [cells](https://bliptext.com/articles/cell-biology) and a complete [organ](https://bliptext.com/articles/organ-biology).\nAccordingly, organs are formed by the functional grouping together of multiple tissues.\n[Biological](https://bliptext.com/articles/biological) organisms follow this [hierarchy](https://bliptext.com/articles/hierarchy):\n[Cells](https://bliptext.com/articles/cell-biology) < Tissue < [Organ](https://bliptext.com/articles/organ-biology) < [Organ](https://bliptext.com/articles/organ-biology) System < [Organ](https://bliptext.com/articles/organ-biology)ism\nThe English word \"tissue\" [derives](https://bliptext.com/articles/morphological-derivation) from the French word \"\", the past participle of the verb tisser, \"to weave\".\nThe study of tissues is known as [histology](https://bliptext.com/articles/histology) or, in connection with disease, as [histopathology](https://bliptext.com/articles/histopathology).\n[Xavier Bichat](https://bliptext.com/articles/xavier-bichat) is considered as the \"Father of Histology\".\nPlant histology is [studied](https://bliptext.com/articles/studied-space-shuttle-designs) in both [plant anatomy](https://bliptext.com/articles/plant-anatomy) and [physiology](https://bliptext.com/articles/plant-physiology).\nThe classical tools for studying tissues are the [paraffin block](https://bliptext.com/articles/microtome) in which tissue is embedded and then sectioned, the [histological stain](https://bliptext.com/articles/staining), and the [optical microscope](https://bliptext.com/articles/microscope).\nDevelopments in [electron microscopy](https://bliptext.com/articles/electron-microscopy), [immunofluorescence](https://bliptext.com/articles/immunofluorescence), and the use of [frozen tissue-sections](https://bliptext.com/articles/microtome) have enhanced the detail that can be observed in tissues.\nWith these tools, the classical appearances of tissues can be examined in health and [disease](https://bliptext.com/articles/disease), enabling considerable refinement of [medical diagnosis](https://bliptext.com/articles/medical-diagnosis) and [prognosis](https://bliptext.com/articles/prognosis).\n# [Microscopic view of a histologic specimen of human lung, consisting of various tissues: blood, connective tissue, vascular endothelium and respiratory epithelium, stained with hematoxylin and eosin. | upload.wikimedia.org/wikipedia/commons/8/86/Emphysema///H///and///E.jpg]\n\n# Plant tissue\nIn [plant anatomy](https://bliptext.com/articles/plant-anatomy), tissues are categorized broadly into three tissue systems: the [epidermis](https://bliptext.com/articles/epidermis-botany), the [ground tissue](https://bliptext.com/articles/ground-tissue), and the [vascular tissue](https://bliptext.com/articles/vascular-tissue).\nPlant tissues can also be divided differently into two types:\n# [Cross-section of a flax plant stem with several layers of different tissue types: | upload.wikimedia.org/wikipedia/commons/9/92/Stem-histology-cross-section-tag.svg]\n\n## Meristematic tissue\n[Meristematic tissue](https://bliptext.com/articles/meristem) consists of actively dividing cells and leads to increase in length and thickness of the plant.\nThe primary growth of a plant occurs only in certain specific regions, such as in the tips of stems or roots.\nIt is in these regions that meristematic tissue is present.\nCells of this type of tissue are roughly spherical or polyhedral to rectangular in shape, with thin [cell walls](https://bliptext.com/articles/cell-wall).\nNew cells produced by meristem are initially those of meristem itself, but as the new cells grow and mature, their characteristics slowly change and they become differentiated as components of meristematic tissue, being classified as:\nThere are two types of meristematic Tissue\n1.Primary meristem.\n2.Secondary meristem.\nThe cells of meristematic tissue are similar in structure and have a thin and elastic primary cell wall made of [cellulose](https://bliptext.com/articles/cellulose).\nThey are compactly arranged without inter-cellular spaces between them.\nEach cell contains a dense [cytoplasm](https://bliptext.com/articles/cytoplasm) and a prominent [cell nucleus](https://bliptext.com/articles/cell-nucleus).\nThe dense [protoplasm](https://bliptext.com/articles/protoplasm) of meristematic cells contains very few [vacuoles](https://bliptext.com/articles/vacuole).\nNormally the meristematic cells are oval, [polygonal](https://bliptext.com/articles/polygon), or [rectangular](https://bliptext.com/articles/rectangular) in shape.\nMeristematic tissue cells have a large nucleus with small or no vacuoles because they have no need to store anything, as opposed to their function of multiplying and increasing the girth and length of the plant, with no intercellular spaces.\n\n## Permanent tissues\nPermanent tissues may be defined as a group of living or dead cells formed by meristematic tissue and have lost their ability to divide and have permanently placed at fixed positions in the plant body.\nMeristematic tissues that take up a specific role lose the ability to divide.\nThis process of taking up a permanent shape, size and a function is called [cellular differentiation](https://bliptext.com/articles/cellular-differentiation).\nCells of meristematic tissue differentiate to form different types of permanent tissues.\nThere are 2 types of permanent tissues:\n\n### Simple permanent tissue\nSimple permanent tissue is a group of cells which are similar in origin, structure, and function.\nThey are of three types:\n\n#### Parenchyma\n[Parenchyma](https://bliptext.com/articles/parenchyma) (Greek, para – 'beside'; enchyma– infusion – 'tissue') is the bulk of a substance.\nIn plants, it consists of relatively unspecialized living cells with thin cell walls that are usually loosely packed so that intercellular spaces are found between cells of this tissue.\nThese are generally isodiametric, in shape.\nThey contain small number of vacuoles or sometimes they even may not contain any vacuole.\nEven if they do so the vacuole is of much smaller size than of normal animal cells.\nThis tissue provides support to plants and also stores food.\n[Chlorenchyma](https://bliptext.com/articles/chlorenchyma) is a special type of parenchyma that contains [chlorophyll](https://bliptext.com/articles/chlorophyll) and performs photosynthesis.\nIn aquatic plants, [aerenchyma](https://bliptext.com/articles/aerenchyma) tissues, or large air cavities, give support to float on water by making them buoyant.\nParenchyma cells called idioblasts have metabolic waste.\nSpindle shaped fibers are also present in this cell to support them and known as prosenchyma, succulent parenchyma also noted.\nIn [xerophytes](https://bliptext.com/articles/xerophytes), parenchyma tissues store water.\n\n#### Collenchyma\n[Collenchyma](https://bliptext.com/articles/collenchyma) (Greek, 'Colla' means gum and 'enchyma' means infusion) is a living tissue of primary body like [Parenchyma](https://bliptext.com/articles/parenchyma).\nCells are thin-walled but possess thickening of [cellulose](https://bliptext.com/articles/cellulose), water and [pectin](https://bliptext.com/articles/pectin) substances (pecto[cellulose](https://bliptext.com/articles/cellulose)) at the corners where a number of cells join.\nThis tissue gives tensile strength to the plant and the cells are compactly arranged and have very little inter-cellular spaces.\nIt occurs chiefly in [hypodermis](https://bliptext.com/articles/hypodermis) of stems and leaves.\nIt is absent in [monocots](https://bliptext.com/articles/monocots) and in roots.\nCollenchymatous tissue acts as a supporting tissue in stems of young plants.\nIt provides mechanical support, elasticity, and tensile strength to the plant body.\nIt helps in manufacturing sugar and storing it as starch.\nIt is present in the margin of leaves and resists tearing effect of the wind.\n# [Cross section of collenchyma cells | upload.wikimedia.org/wikipedia/commons/9/97/Plant///cell///type///collenchyma.png]\n\n#### Sclerenchyma\n[Sclerenchyma](https://bliptext.com/articles/ground-tissue) (Greek, Sclerous means hard and enchyma means infusion) consists of thick-walled, dead cells and protoplasm is negligible.\nThese cells have hard and extremely thick secondary walls due to uniform distribution and high secretion of [lignin](https://bliptext.com/articles/lignin) and have a function of providing mechanical support.\nThey do not have inter-cellular spaces between them.\nLignin deposition is so thick that the cell walls become stronger, rigid and impermeable to water, which are also known as a stone cells or sclereids.\nThese tissues are mainly of two types: sclerenchyma fiber and sclereids.\nSclerenchyma fiber cells have a narrow lumen and are long, narrow and unicellular.\nFibers are elongated cells that are strong and flexible, often used in ropes.\nSclereids have extremely thick cell walls and are brittle, and are found in nutshells and legumes.\n\n#### Epidermis\nThe entire surface of the plant consists of a single layer of cells called epidermis or surface tissue.\nThe entire surface of the plant has this outer layer of the epidermis.\nHence it is also called surface tissue.\nMost of the epidermal cells are relatively flat.\nThe outer and lateral walls of the cell are often thicker than the inner walls.\nThe cells form a continuous sheet without intercellular spaces.\nIt protects all parts of the plant.\nThe outer epidermis is coated with a waxy thick layer called cutin which prevents loss of water.\nThe epidermis also consists of [stomata](https://bliptext.com/articles/stomata) (singular:stoma) which helps in [transpiration](https://bliptext.com/articles/transpiration).\n\n### Complex permanent tissue\nThe complex permanent tissue consists of more than one type of cells having a common origin which work together as a unit.\nComplex tissues are mainly concerned with the transportation of mineral nutrients, organic solutes (food materials), and water.\nThat's why it is also known as conducting and vascular tissue.\nThe common types of complex permanent tissue are:\nXylem and phloem together form vascular bundles.\n\n#### Xylem\n[Xylem](https://bliptext.com/articles/xylem) (Greek, xylos = wood) serves as a chief conducting tissue of vascular plants.\nIt is responsible for the conduction of water and inorganic solutes.\nXylem consists of four kinds of cells:\nXylem tissue is organised in a tube-like fashion along the main axes of stems and roots.\nIt consists of a combination of parenchyma cells, fibers, vessels, tracheids, and ray cells.\nLonger tubes made up of individual cellssels tracheids, while vessel members are open at each end.\nInternally, there may be bars of wall material extending across the open space.\nThese cells are joined end to end to form long tubes.\nVessel members and tracheids are dead at maturity.\nTracheids have thick secondary cell walls and are tapered at the ends.\nThey do not have end openings such as the vessels.\nThe end overlap with each other, with pairs of pits present.\nThe pit pairs allow water to pass from cell to cell.\nThough most conduction in xylem tissue is vertical, lateral conduction along the diameter of a stem is facilitated via rays.\nRays are horizontal rows of long-living parenchyma cells that arise out of the vascular cambium.\n# [Cross section of 2-year-old Tilia americana, highlighting xylem ray shape and orientation | upload.wikimedia.org/wikipedia/commons/4/4e/Xylem///rays///%28Tilia///Americana%29.jpg]\n\n#### Phloem\n[Phloem](https://bliptext.com/articles/phloem) consists of:\nPhloem is an equally important plant tissue as it also is part of the 'plumbing system' of a plant.\nPrimarily, phloem carries dissolved food substances throughout the plant.\nThis conduction system is composed of sieve-tube member and companion cells, that are without secondary walls.\nThe parent cells of the vascular cambium produce both xylem and phloem.\nThis usually also includes fibers, parenchyma and ray cells.\nSieve tubes are formed from sieve-tube members laid end to end.\nThe end walls, unlike vessel members in xylem, do not have openings.\nThe end walls, however, are full of small pores where cytoplasm extends from cell to cell.\nThese porous connections are called sieve plates.\nIn spite of the fact that their cytoplasm is actively involved in the conduction of food materials, sieve-tube members do not have nuclei at maturity.\nIt is the companion cells that are nestled between sieve-tube members that function in some manner bringing about the conduction of food.\nSieve-tube members that are alive contain a polymer called callose, a carbohydrate polymer, forming the callus pad/callus, the colourless substance that covers the sieve plate.\nCallose stays in solution as long as the cell contents are under pressure.\nPhloem transports food and materials in plants upwards and downwards as required.\n\n# Animal tissue\nAnimal tissues are grouped into four basic types: [connective](https://bliptext.com/articles/connective-tissue), [muscle](https://bliptext.com/articles/muscle-tissue), [nervous](https://bliptext.com/articles/nervous-tissue), and [epithelial](https://bliptext.com/articles/epithelium).\nCollections of tissues joined in units to serve a common function compose organs.\nWhile most animals can generally be considered to contain the four tissue types, the manifestation of these tissues can differ depending on the type of organism.\nFor example, the origin of the cells comprising a particular tissue type may differ developmentally for different classifications of animals.\nTissue appeared for the first time in the [diploblasts](https://bliptext.com/articles/eumetazoa), but modern forms only appeared in [triploblasts](https://bliptext.com/articles/triploblasts).\nThe epithelium in all animals is derived from the [ectoderm](https://bliptext.com/articles/ectoderm) and [endoderm](https://bliptext.com/articles/endoderm) (or their precursor in [sponges](https://bliptext.com/articles/sponges)), with a small contribution from the [mesoderm](https://bliptext.com/articles/mesoderm), forming the [endothelium](https://bliptext.com/articles/endothelium), a specialized type of epithelium that composes the [vasculature](https://bliptext.com/articles/blood-vessels).\nBy contrast, a true [epithelial tissue](https://bliptext.com/articles/epithelial-tissue) is present only in a single layer of cells held together via occluding junctions called [tight junctions](https://bliptext.com/articles/tight-junctions), to create a selectively permeable barrier.\nThis tissue covers all organismal surfaces that come in contact with the external environment such as the [skin](https://bliptext.com/articles/skin), the airways, and the digestive tract.\nIt serves functions of protection, [secretion](https://bliptext.com/articles/secretion), and absorption, and is separated from other tissues below by a [basal lamina](https://bliptext.com/articles/basal-lamina).\nThe connective tissue and the muscular are derived from the mesoderm.\nThe nervous tissue is derived from the ectoderm.\n\n## Epithelial tissues\nThe epithelial tissues are formed by cells that cover the organ surfaces, such as the surface of [skin](https://bliptext.com/articles/skin), the [airways](https://bliptext.com/articles/airway), surfaces of soft organs, the [reproductive tract](https://bliptext.com/articles/reproductive-tract), and the inner lining of the [digestive tract](https://bliptext.com/articles/digestive-tract).\nThe cells comprising an epithelial layer are linked via semi-permeable, [tight junctions](https://bliptext.com/articles/tight-junctions); hence, this tissue provides a barrier between the external environment and the organ it covers.\nIn addition to this protective function, epithelial tissue may also be specialized to function in [secretion](https://bliptext.com/articles/secretion), [excretion](https://bliptext.com/articles/excretion) and [absorption](https://bliptext.com/articles/digestion).\nEpithelial tissue helps to protect organs from microorganisms, injury, and fluid loss.\nFunctions of epithelial tissue:\nThere are many kinds of epithelium, and nomenclature is somewhat variable.\nMost classification schemes combine a description of the cell-shape in the upper layer of the epithelium with a word denoting the number of layers: either simple (one layer of cells) or stratified (multiple layers of cells).\nHowever, other cellular features such as cilia may also be described in the classification system.\nSome common kinds of epithelium are listed below:\n\n## Connective tissue\nConnective tissues are made up of cells separated by non-living material, which is called an [extracellular matrix](https://bliptext.com/articles/extracellular-matrix).\nThis matrix can be liquid or rigid.\nFor example, blood contains plasma as its matrix and bone's matrix is rigid.\nConnective tissue gives shape to organs and holds them in place.\nBlood, bone, tendon, ligament, adipose, and areolar tissues are examples of connective tissues.\nOne method of classifying connective tissues is to divide them into three types: fibrous connective tissue, skeletal connective tissue, and fluid connective tissue.\n\n## Muscle tissue\n[Muscle cells](https://bliptext.com/articles/muscle-cell) (myocytes) form the active contractile tissue of the body.\n[Muscle tissue](https://bliptext.com/articles/muscle-tissue) functions to produce force and cause motion, either [locomotion](https://bliptext.com/articles/animal-locomotion) or movement within internal organs.\nMuscle is formed of contractile [filaments](https://bliptext.com/articles/myofilament) and is separated into three main types; [smooth muscle](https://bliptext.com/articles/smooth-muscle), [skeletal muscle](https://bliptext.com/articles/skeletal-muscle) and [cardiac muscle](https://bliptext.com/articles/cardiac-muscle).\nSmooth muscle has no [striations](https://bliptext.com/articles/striated-muscle-tissue) when examined microscopically.\nIt contracts slowly but maintains contractibility over a wide range of stretch lengths.\nIt is found in such organs as [sea anemone](https://bliptext.com/articles/sea-anemone) tentacles and the body wall of [sea cucumbers](https://bliptext.com/articles/sea-cucumber).\nSkeletal muscle contracts rapidly but has a limited range of extension.\nIt is found in the movement of appendages and jaws.\nObliquely striated muscle is intermediate between the other two.\nThe filaments are staggered and this is the type of muscle found in [earthworms](https://bliptext.com/articles/earthworm) that can extend slowly or make rapid contractions.\nIn higher animals striated muscles occur in bundles attached to bone to provide movement and are often arranged in antagonistic sets.\nSmooth muscle is found in the walls of the [uterus](https://bliptext.com/articles/uterus), [bladder](https://bliptext.com/articles/bladder), [intestines](https://bliptext.com/articles/intestines), [stomach](https://bliptext.com/articles/stomach), [oesophagus](https://bliptext.com/articles/oesophagus), [respiratory airways](https://bliptext.com/articles/respiratory-airways), and [blood vessels](https://bliptext.com/articles/blood-vessel).\nCardiac muscle is found only in the [heart](https://bliptext.com/articles/heart), allowing it to contract and pump blood through the body.\n# [Cross section through skeletal muscle and a small nerve at high magnification (H&E stain) | upload.wikimedia.org/wikipedia/commons/c/c3/Skeletal///muscle///-///cross///section%2C///nerve///bundle.jpg]\n\n## Nervous tissue\nCells comprising the [central nervous system](https://bliptext.com/articles/central-nervous-system) and [peripheral nervous system](https://bliptext.com/articles/peripheral-nervous-system) are classified as nervous (or neural) tissue.\nIn the central nervous system, neural tissues form the [brain](https://bliptext.com/articles/brain) and [spinal cord](https://bliptext.com/articles/spinal-cord).\nIn the peripheral nervous system, neural tissues form the [cranial nerves](https://bliptext.com/articles/cranial-nerves) and [spinal nerves](https://bliptext.com/articles/spinal-nerve), inclusive of the [motor neurons](https://bliptext.com/articles/motor-neuron).\n\n## Mineralized tissues\nMineralized tissues are biological tissues that incorporate minerals into soft matrices.\nSuch tissues may be found in both plants and animals.\n\n# History\n[Xavier Bichat](https://bliptext.com/articles/xavier-bichat) introduced the word tissue into the study of [anatomy](https://bliptext.com/articles/anatomy) by 1801.\nHe was \"the first to propose that tissue is a central element in [human anatomy](https://bliptext.com/articles/human-anatomy), and he considered [organs](https://bliptext.com/articles/organ-anatomy) as collections of often disparate tissues, rather than as entities in themselves\".\nAlthough he worked without a [microscope](https://bliptext.com/articles/microscope), Bichat distinguished 21 types of elementary tissues from which the organs of the human body are composed, a number later reduced by other authors.\n# [Xavier Bichat (1771–1802) | upload.wikimedia.org/wikipedia/commons/7/7f/Pierre-Maximilien///Delafontaine///-///Portrait///of///Marie///Fran%C3%A7ois///Xavier///Bichat.jpg]\n\n# 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