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In
biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, Developmenta ...
, tissue is a
biological organizational level
biological organizational level
between
cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic cell, a small room, hut, or cave in which a monk or religious recluse lives * Prison cell, a room used to hold peopl ...
and a complete
organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tissues can be broadly cate ...
. A tissue is an ensemble of similar cells and their
extracellular matrix In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, ...
from the same origin that together carry out a specific function. Organs are then formed by the functional grouping together of multiple tissues. The English word "tissue" derives from the French word "tissu", the past participle of the verb tisser, "to weave". The study of tissues is known as
histology Histology, also known as microscopic anatomy or microanatomy, is the branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Mol ...

histology
or, in connection with disease, as
histopathology Histopathology (compound of three Greek language, Greek words: ''histos'' "tissue", πάθος ''pathos'' "suffering", and -λογία ''-logy, -logia'' "study of") refers to the light microscope, microscopic examination of Tissue (biology), tiss ...
.
Xavier Bichat Marie François Xavier Bichat (; ; 14 November 1771 – 22 July 1802) was a French anatomist Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology Biology is the natural science that studies life and living organisms, inclu ...
is considered as the "Father of Histology". Plant histology is studied in both
plant anatomy Plant anatomy or phytotomy is the general term for the study of the internal structure of plants. Originally it included plant morphology, the description of the physical form and external structure of plants, but since the mid-20th century plan ...
and
physiology Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, B ...

physiology
. The classical tools for studying tissues are the
paraffin block
paraffin block
in which tissue is embedded and then sectioned, the histological stain, and the
optical microscope The optical microscope, also referred to as a light microscope, is a type of microscope that commonly uses visible spectrum, visible light and a system of lens (optics), lenses to generate magnified images of small objects. Optical microscopes a ...

optical microscope
. Developments in
electron microscopy An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination. As the wavelength of an electron can be up to 100,000 times shorter than that of visible light photons, electron microscopes have a high ...
,
immunofluorescence of human skin prepared for direct immunofluorescence using an anti-IgA antibody. The skin is from a patient with Henoch–Schönlein purpura: IgA deposits are found in the walls of small superficial capillaries (yellow arrows). The pale wavy green ...

immunofluorescence
, and the use of frozen tissue-sections have enhanced the detail that can be observed in tissues. With these tools, the classical appearances of tissues can be examined in health and
disease A disease is a particular abnormal condition that negatively affects the structure A structure is an arrangement and organization of interrelated elements in a material object or system A system is a group of Interaction, interacting ...
, enabling considerable refinement of
medical diagnosis Medical diagnosis (abbreviated Dx, Dx, or Ds) is the process of determining which disease or condition explains a person's symptoms and medical sign, signs. It is most often referred to as diagnosis with the medicine, medical context being implici ...
and
prognosis Prognosis ( Greek: πρόγνωσις "fore-knowing, foreseeing") is a medical term for predicting the likely or expected development of a disease, including whether the signs and symptom Signs and symptoms are the observed or detectable signs ...
.


Plant tissue

In
plant anatomy Plant anatomy or phytotomy is the general term for the study of the internal structure of plants. Originally it included plant morphology, the description of the physical form and external structure of plants, but since the mid-20th century plan ...
, tissues are categorized broadly into three tissue systems: the
epidermis The epidermis is the outermost of the three layers that comprise the skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Oth ...
, the
ground tissue The ground tissue of plants includes all tissues that are neither dermal nor vascular. It can be divided into three types based on the nature of the cell walls. # Parenchyma cells have thin primary walls and usually remain alive after they bec ...
, and the
vascular tissue stalk, showing vascular bundles, which include both phloem and xylem. Image:BrambleLeaf_CrossPolarisedLight_Diagram.jpg">250px, Detail of the vasculature of a tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells t ...
. * Epidermis – Cells forming the outer surface of the
leaves A leaf (plural leaves) is the principal lateral appendage of the vascular plant plant stem, stem, usually borne above ground and specialized for photosynthesis. The leaves, stem, flower and fruit together form the shoot system. Leaves are ...

leaves
and of the young plant body. * Vascular tissue – The primary components of vascular tissue are the
xylem Xylem is one of the two types of transport tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North Amer ...

xylem
and
phloem Phloem (, ) is the living tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North America * ''Triphosa d ...

phloem
. These transport fluids and nutrients internally. * Ground tissue – Ground tissue is less differentiated than other tissues. Ground tissue manufactures nutrients by
photosynthesis File:Photosynthesis equation.svg, upright=1.8, Overall equation for the type of photosynthesis that occurs in plants Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energ ...

photosynthesis
and stores reserve nutrients. Plant tissues can also be divided differently into two types: # Meristematic tissues # Permanent tissues.


Meristematic tissue

Meristematic tissue consists of actively dividing cells and leads to increase in length and thickness of the plant. The primary growth of a plant occurs only in certain specific regions, such as in the tips of stems or roots. It is in these regions that meristematic tissue is present. Cells of this type of tissue are roughly spherical or polyhedral to rectangular in shape, with thin
cell wall A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane cell membrane vs. Prokaryotes The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to a ...
s. New 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: * Apical meristem : Present at the growing tips of stems and roots, they increase the length of the stem and root. They form growing parts at the apices of roots and stems and are responsible for the increase in length, also called primary growth. This meristem is responsible for the linear growth of an organ. * Lateral meristem: Cells which mainly divide in one
plane Plane or planes may refer to: * Airplane or aeroplane or informally plane, a powered, fixed-wing aircraft Arts, entertainment and media *Plane (Dungeons & Dragons), Plane (''Dungeons & Dragons''), a location in the multiverse *Plane (Magic: Th ...
and cause the organ to increase in diameter and girth. Lateral meristem usually occurs beneath the bark of the tree as
cork cambium Cork cambium (pl. cambia or cambiums) is a tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North Americ ...
and in vascular bundles of
dicotyledon The dicotyledons, also known as dicots (or more rarely dicotyls), are one of the two groups into which all the flowering plant The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of Embryophyte ...
s as
vascular cambium The vascular cambium is the main growth tissue in the stems and roots of many plants, specifically in dicots such as buttercups and oak trees, gymnosperm The gymnosperms, also known as Acrogymnospermae, are a group of seed-producing plants th ...
. The activity of this cambium forms secondary growth. * Intercalary meristem: Located between permanent tissues, it is usually present at the base of the node, internode, and on leaf base. They are responsible for growth in length of the plant and increasing the size of the internode. They result in branch formation and growth. The cells of meristematic tissue are similar in structure and have a thin and elastic primary cell wall made of
cellulose Cellulose is an organic compound , CH4; is among the simplest organic compounds. In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ...

cellulose
. They are compactly arranged without inter-cellular spaces between them. Each cell contains a dense
cytoplasm In cell biology Cell biology (also cellular biology or cytology) is a branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, ...
and a prominent
cell nucleus In cell biology Cell biology (also cellular biology or cytology) is a branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processe ...

cell nucleus
. The dense
protoplasmProtoplasm (/prəʊtə(ʊ)ˌplaz(ə)m/, plural protoplasms) is the living part of a cell that is surrounded by a plasma membrane cell membrane vs. Prokaryotes The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, an ...

protoplasm
of meristematic cells contains very few
vacuole A vacuole () is a membrane-bound organelle In cell biology, an organelle is a specialized subunit, usually within a cell (biology), cell, that has a specific function. The name ''organelle'' comes from the idea that these structures are parts o ...
s. Normally the meristematic cells are oval,
polygon In geometry, a polygon () is a plane (mathematics), plane Shape, figure that is described by a finite number of straight line segments connected to form a closed ''polygonal chain'' (or ''polygonal circuit''). The bounded plane region (mathematic ...

polygon
al, or
rectangular In Euclidean plane geometry, a rectangle is a quadrilateral A quadrilateral is a polygon in Euclidean geometry, Euclidean plane geometry with four Edge (geometry), edges (sides) and four Vertex (geometry), vertices (corners). Other names for ...

rectangular
in shape. Meristematic 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.


Permanent tissues

Permanent 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. Meristematic tissues that take up a specific role lose the ability to divide. This process of taking up a permanent shape, size and a function is called
cellular differentiation Cellular differentiation is the process in which a cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic cell, a small room, hut, or cave in which a monk or re ...
. Cells of meristematic tissue differentiate to form different types of permanent tissues. There are 2 types of permanent tissues: # simple permanent tissues # complex permanent tissues


Simple permanent tissue

Simple permanent tissue is a group of cells which are similar in origin, structure, and function . They are of three types: #
Parenchyma Parenchyma () is the bulk of functional substance in an animal organ or structure such as a tumour. In zoology Zoology ()The pronunciation of zoology as is typically regarded as nonstandard, though it is not uncommon. is the branch of biolo ...

Parenchyma
#
Collenchyma The ground tissue of plants includes all tissues that are neither dermal The dermis or corium is a layer of skin between the epidermis (skin), epidermis (with which it makes up the cutis (anatomy), cutis) and subcutaneous tissues, that primarily ...
#
Sclerenchyma The ground tissue of plants includes all tissues that are neither dermal nor vascular. It can be divided into three types based on the nature of the cell walls. # Parenchyma cells have thin primary walls and usually remain alive after they bec ...


= Parenchyma

=
Parenchyma Parenchyma () is the bulk of functional substance in an animal organ or structure such as a tumour. In zoology Zoology ()The pronunciation of zoology as is typically regarded as nonstandard, though it is not uncommon. is the branch of biolo ...

Parenchyma
(Greek, ''para'' – 'beside'; enchyma– ''infusion'' – 'tissue') is the bulk of a substance. In 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. These are generally isodiametric, in shape. They contain small number of vacuoles or sometimes they even may not contain any vacuole. Even if they do so the vacuole is of much smaller size than of normal animal cells. This tissue provides support to plants and also stores food. Chlorenchyma is a special type of parenchyma that contains
chlorophyll Chlorophyll (also chlorophyl) is any of several related green pigments found in the mesosomes of cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Ancient Greek, Greek words , ("pale green") and , ("leaf") ...

chlorophyll
and performs photosynthesis. In aquatic plants,
aerenchyma alt=Aerenchyma of '' Aerenchyma in stem cross section of a typical wetland plant. Aerenchyma or aeriferous parenchyma is a spongy tissue that forms spaces or air channels in the leaves, stems and roots of some plants, which allows exchange of gases ...
tissues, or large air cavities, give support to float on water by making them buoyant. Parenchyma cells called idioblasts have metabolic waste. Spindle shape fiber also contained into this cell to support them and known as prosenchyma, succulent parenchyma also noted. In
xerophytesA xerophyte (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 millio ...
, parenchyma tissues store water.


= Collenchyma

=
Collenchyma The ground tissue of plants includes all tissues that are neither dermal The dermis or corium is a layer of skin between the epidermis (skin), epidermis (with which it makes up the cutis (anatomy), cutis) and subcutaneous tissues, that primarily ...
(Greek, ‘Colla’ means gum and ‘enchyma’ means infusion) is a living tissue of primary body like
Parenchyma Parenchyma () is the bulk of functional substance in an animal organ or structure such as a tumour. In zoology Zoology ()The pronunciation of zoology as is typically regarded as nonstandard, though it is not uncommon. is the branch of biolo ...

Parenchyma
. Cells are thin-walled but possess thickening of
cellulose Cellulose is an organic compound , CH4; is among the simplest organic compounds. In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ...

cellulose
, water and
pectin Commercially produced powder of pectin, extracted from citrus fruits. Pectin (from grc, πηκτικός ', "congealed, curdled") is a structural acidic heteropolysaccharide contained in the primary and middle lamella and cell walls of terrestr ...

pectin
substances (
pectocellulose
pectocellulose
) at the corners where a number of cells join together. This tissue gives tensile strength to the plant and the cells are compactly arranged and have very little inter-cellular spaces. It occurs chiefly in
hypodermis The subcutaneous tissue (), also called the hypodermis, hypoderm (), subcutis, superficial fascia, is the lowermost layer of the integumentary system The integumentary system is the set of organs forming the outermost layer of an animal's body. ...
of stems and leaves. It is absent in
monocots Monocotyledons (), commonly referred to as monocots, (Lilianae ''sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one Embryo#Plant embryos, embryonic leaf, or cotyledon. The ...

monocots
and in roots. Collenchymatous tissue acts as a supporting tissue in stems of young plants. It provides mechanical support, elasticity, and tensile strength to the plant body. It helps in manufacturing sugar and storing it as starch. It is present in the margin of leaves and resists tearing effect of the wind.


= Sclerenchyma

=
Sclerenchyma The ground tissue of plants includes all tissues that are neither dermal nor vascular. It can be divided into three types based on the nature of the cell walls. # Parenchyma cells have thin primary walls and usually remain alive after they bec ...
(Greek, ''Sclerous'' means hard and ''enchyma'' means infusion) consists of thick-walled, dead cells and protoplasm is negligible. These cells have hard and extremely thick secondary walls due to uniform distribution and high secretion of
lignin Lignin is a class of complex organic polymer A polymer (; Greek ''poly- Poly, from the Greek :wikt:πολύς, πολύς meaning "many" or "much", may refer to: Businesses * China Poly Group Corporation, a Chinese business group, and its s ...

lignin
and have a function of providing mechanical support. They do not have inter-molecular space between them. Lignin deposition is so thick that the cell walls become strong, rigid and impermeable to water which is also known as a stone cell or sclereids. These tissues are mainly of two types: sclerenchyma fiber and sclereids. Sclerenchyma fibre cells have a narrow lumen and are long, narrow and unicellular. Fibers are elongated cells that are strong and flexible, often used in ropes. Sclereids have extremely thick cell walls and are brittle, and are found in nutshells and legumes.


= Epidermis

= The entire surface of the plant consists of a single layer of cells called epidermis or surface tissue. The entire surface of the plant has this outer layer of the epidermis. Hence it is also called surface tissue. Most of the epidermal cells are relatively flat. The outer and lateral walls of the cell are often thicker than the inner walls. The cells form a continuous sheet without intercellular spaces. It protects all parts of the plant. The outer epidermis is coated with a waxy thick layer called cutin which prevents loss of water. The epidermis also consists of
stomata File:LeafUndersideWithStomata.jpg, The underside of a leaf. In this species (''Tradescantia zebrina'') the guard cells of the stomata are green because they contain chlorophyll while the epidermal cells are chlorophyll-free and contain red pigme ...

stomata
(singular:stoma) which helps in
transpiration in a tomato The tomato is the edible berry of the plant ''Solanum lycopersicum'', commonly known as a tomato plant. The species originated in western South America South America is a continent entirely in the Western Hemisphere ...

transpiration
.


Complex permanent tissue

The complex permanent tissue consists of more than one type of cells having a common origin which work together as a unit. Complex tissues are mainly concerned with the transportation of mineral nutrients, organic solutes (food materials), and water. That's why it is also known as conducting and vascular tissue. The common types of complex permanent tissue are: *
Xylem Xylem is one of the two types of transport tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North Amer ...

Xylem
(or wood) *
Phloem Phloem (, ) is the living tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North America * ''Triphosa d ...

Phloem
(or bast). Xylem and phloem together form vascular bundles.


= Xylem

=
Xylem Xylem is one of the two types of transport tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North Amer ...

Xylem
(Greek, ''xylos'' = wood) serves as a chief conducting tissue of vascular plants. It is responsible for the conduction of water and inorganic solutes. Xylem consists of four kinds of cells: * Tracheids * Vessels (or tracheae) * Xylem fibres or Xylem sclerenchyma * Xylem parenchyma Xylem tissue is organised in a tube-like fashion along the main axes of stems and roots. It consists of a combination of parenchyma cells, fibers, vessels, tracheids, and ray cells. Longer tubes made up of individual cellssels tracheids, while vessel members are open at each end. Internally, there may be bars of wall material extending across the open space. These cells are joined end to end to form long tubes. Vessel members and tracheids are dead at maturity. Tracheids have thick secondary cell walls and are tapered at the ends. They do not have end openings such as the vessels. The end overlap with each other, with pairs of pits present. The pit pairs allow water to pass from cell to cell. Though most conduction in xylem tissue is vertical, lateral conduction along the diameter of a stem is facilitated via rays. Rays are horizontal rows of long-living parenchyma cells that arise out of the vascular cambium.


= Phloem

=
Phloem Phloem (, ) is the living tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North America * ''Triphosa d ...

Phloem
consists of: * Sieve tube * Companion cell * Phloem fibre * Phloem parenchyma. Phloem is an equally important plant tissue as it also is part of the 'plumbing system' of a plant. Primarily, phloem carries dissolved food substances throughout the plant. This conduction system is composed of sieve-tube member and companion cells, that are without secondary walls. The parent cells of the vascular cambium produce both xylem and phloem. This usually also includes fibers, parenchyma and ray cells. Sieve tubes are formed from sieve-tube members laid end to end. The end walls, unlike vessel members in xylem, do not have openings. The end walls, however, are full of small pores where cytoplasm extends from cell to cell. These porous connections are called sieve plates. In 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. It is the companion cells that are nestled between sieve-tube members that function in some manner bringing about the conduction of food. Sieve-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. Callose stays in solution as long as the cell contents are under pressure. Phloem transports food and materials in plants upwards and downwards as required.


Animal tissue

Animal tissues are grouped into four basic types: connective,
muscle Skeletal muscles (commonly referred to as muscles) are organs An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tissues can be broadly cate ...

muscle
, nervous, and
epithelial Epithelium is one of the four basic types of animal Tissue (biology), tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed Cell (biology), cells with little Extr ...
. Collections of tissues joined in units to serve a common function compose organs. While all animals can generally be considered to contain the four tissue types, the manifestation of these tissues can differ depending on the type of organism. For example, the origin of the cells comprising a particular tissue type may differ developmentally for different classifications of animals. Tissue appeared for the first time in members of phylum
Coelenterata Coelenterata is a term encompassing the animal phyla Cnidaria Image:Sea nettles.jpg, Chrysaora fuscescens, Pacific sea nettles, ''Chrysaora fuscescens'' Cnidaria () is a phylum under kingdom Animalia containing over 11,000 species of aquatic a ...
. The epithelium in all animals is derived from the
ectoderm The ectoderm is one of the three primary germ layer A germ layer is a primary layer of cells that forms during embryonic development. The three germ layers in vertebrate Vertebrates () comprise all species of animal Animals (also ...

ectoderm
and
endoderm Endoderm is the innermost of the three primary germ layer A germ layer is a primary layer of cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic cell, a small r ...
, with a small contribution from the
mesoderm The mesoderm is the middle layer of the three germ layer A germ layer is a primary layer of cells that forms during embryonic development. The three germ layers in vertebrate Vertebrates () comprise all species of animal Animals (a ...

mesoderm
, forming the
endothelium Endothelium is a single layer of squamous epithelial cell, squamous endothelial cells that line the interior surface of blood vessels, and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen (anat ...
, a specialized type of epithelium that composes the
vasculature The circulatory system, also called the cardiovascular system or the vascular system, is an organ system that permits blood to circulate and transport nutrients (such as amino acids and electrolytes), oxygen Oxygen is the chemical e ...

vasculature
. By contrast, a true
epithelial tissue Epithelium () is one of the four basic types of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume ...
is present only in a single layer of cells held together via occluding junctions called
tight junctions Tight junctions, also known as occluding junctions or zonulae occludentes (singular, zonula occludens) are multiprotein Cell junction, junctional complexes whose general function is to prevent leakage of transported solutes and water and seals the ...
, to create a selectively permeable barrier. This tissue covers all organismal surfaces that come in contact with the external environment such as the
skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have differe ...

skin
, the airways, and the digestive tract. It serves functions of protection,
secretionSecretion is the movement of material from one point to another, such as a secreted chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up sp ...
, and absorption, and is separated from other tissues below by a
basal lamina The basal lamina is a layer of extracellular matrix In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular ...

basal lamina
. The connective tissue and the muscular are derived from the mesoderm. The neural tissue is derived from the ectoderm.


Epithelial tissue

The epithelial tissues are formed by cells that cover the organ surfaces, such as the surface of
skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have differe ...

skin
, the
airway The respiratory tract is the subdivision of the respiratory system The respiratory system (also respiratory apparatus, ventilatory system) is a biological system A biological system is a complex network which connects several biologically re ...
s, surfaces of soft organs, the reproductive tract, and the inner lining of the
digestive tract The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organ (biology), organs of the digestive syste ...
. The cells comprising an epithelial layer are linked via semi-permeable,
tight junctions Tight junctions, also known as occluding junctions or zonulae occludentes (singular, zonula occludens) are multiprotein Cell junction, junctional complexes whose general function is to prevent leakage of transported solutes and water and seals the ...
; hence, this tissue provides a barrier between the external environment and the organ it covers. In addition to this protective function, epithelial tissue may also be specialized to function in
secretionSecretion is the movement of material from one point to another, such as a secreted chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up sp ...
,
excretion Excretion is a process in which metabolic waste Metabolic wastes or excrements are Chemical substance, substances left over from metabolism, metabolic processes (such as cellular respiration) which cannot be used by the organism (they are surplus ...
and
absorption Absorption may refer to: Chemistry and biology *Absorption (chemistry), diffusion of particles of gas or liquid into liquid or solid materials *Absorption (skin), a route by which substances enter the body through the skin *Absorption (pharmacolo ...
. Epithelial tissue helps to protect organs from microorganisms, injury, and fluid loss. Functions of epithelial tissue: * The principle function of epithelial tissues are covering and lining of free surface * The cells of the body's surface form the outer layer of skin. * Inside the body, epithelial cells form the lining of the mouth and alimentary canal and protect these organs. * Epithelial tissues help in the elimination of waste. * Epithelial tissues secrete enzymes and/or hormones in the form of
gland In animals, a gland is a group of cells in an animal's body that synthesizes substances (such as hormone A hormone (from the Greek participle , "setting in motion") is any member of a class of signaling molecules in multicellular organisms, ...

gland
s. * Some epithelial tissue perform secretory functions. They secrete a variety of substances including sweat, saliva, mucus, enzymes. There are many kinds of epithelium, and nomenclature is somewhat variable. Most 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). However, other cellular features such as cilia may also be described in the classification system. Some common kinds of epithelium are listed below: * Simple squamous (pavement) epithelium * Simple cuboidal epithelium * Simple Columnar epithelium * Simple ciliated (pseudostratified) columnar epithelium * Simple glandular columnar epithelium * Stratified non-keratinized squamous epithelium * Stratified keratinized epithelium * Stratified transitional epithelium


Connective tissue

Connective tissues are fibrous tissues made up of cells separated by non-living material, which is called an
extracellular matrix In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, ...
. This matrix can be liquid or rigid. For example, blood contains plasma as its matrix and bone's matrix is rigid. Connective tissue gives shape to organs and holds them in place. Blood, bone, tendon, ligament, adipose, and areolar tissues are examples of connective tissues. One method of classifying connective tissues is to divide them into three types: fibrous connective tissue, skeletal connective tissue, and fluid connective tissue.


Muscular tissue

Muscle cell A muscle cell is also known as a myocyte when referring to either a cardiac muscle cell Cardiac muscle cells or cardiomyocytes (also known as myocardiocytes or cardiac myocytes) are the muscle cells (myocyte A myocyte is a muscle cell of the ...
s form the active contractile tissue of the
body Body may refer to: In science * Physical body, an object in physics that represents a large amount, has mass or takes up space * Body (biology), the physical material of an organism * Body plan, the physical features shared by a group of animals ...

body
known as
muscle tissue Muscle tissues are soft tissue of a tendon A tendon or sinew is a tough band of fibrous connective tissue that connects muscle to bone A bone is a Stiffness, rigid tissue (anatomy), tissue that constitutes part of the vertebrate skeleton i ...

muscle tissue
or muscular tissue. Muscle tissue functions to produce
force In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities of energy and force ...

force
and cause
motion Image:Leaving Yongsan Station.jpg, 300px, Motion involves a change in position In physics, motion is the phenomenon in which an object changes its position (mathematics), position over time. Motion is mathematically described in terms of Displacem ...
, either
locomotion Locomotion means the act or ability of an entity or person to transport or move oneself from place to place. Locomotion or Loco-Motion may refer to: Motion * Motion (physics) *Specific types of motion ** Animal locomotion *** Terrestrial locomoti ...
or movement within internal organs. Muscle tissue is separated into three distinct categories: visceral or
smooth muscle Smooth muscle is an involuntary non-striated muscle. It is divided into two subgroups; the single-unit smooth muscle, single-unit (unitary) and multiunit smooth muscle. Within single-unit cells, the whole bundle or sheet Muscle contraction, contra ...

smooth muscle
, found in the inner linings of
organs An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tissues can be broadly categorized as parenchyma Parenchyma () is the bulk of functional ...
;
skeletal muscle Skeletal muscles (commonly referred to as muscles) are Organ (biology), organs of the vertebrate muscular system that are mostly attached by tendons to bones of the skeleton. The muscle cells of skeletal muscles are much longer than in the other ...

skeletal muscle
, typically attached to bones, which generate gross movement; and
cardiac muscle Cardiac muscle (also called heart muscle or myocardium) is one of three types of vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biolo ...

cardiac muscle
, found in the
heart The heart is a cardiac muscle, muscular Organ (biology), organ in most animals, which pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste ...

heart
, where it contracts to pump blood throughout an organism.


Nervous tissue

Cells comprising the
central nervous system The central nervous system (CNS) is the part of the nervous system In Biology, biology, the nervous system is a Complex system, highly complex part of an animal that coordinates its Behavior, actions and Sense, sensory information by transmi ...

central nervous system
and
peripheral nervous system The peripheral nervous system (PNS) is one of two components that make up the nervous system In Biology, biology, the nervous system is a Complex system, highly complex part of an animal that coordinates its Behavior, actions and Sense, sen ...
are classified as nervous (or neural) tissue. In the central nervous system, neural tissues form the
brain A brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as Visual perception, vision. It ...

brain
and
spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column. It encloses the central canal of the spinal cord, which co ...

spinal cord
. In the peripheral nervous system, neural tissues form the
cranial nerves Cranial nerves are the nerve A nerve is an enclosed, cable-like bundle of nerve fibers called axon An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see American and British English spelling differences#-re, ...
and
spinal nerve A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into the c ...

spinal nerve
s, inclusive of the
motor neuron A motor neuron (or motoneuron or efferent neuron) is a neuron whose cell body is located in the motor cortex, brainstem or the spinal cord, and whose axon (fiber) projects to the spinal cord or outside of the spinal cord to directly or indirectly c ...
s.


Mineralized tissues

Mineralized tissues are biological tissues that incorporate minerals into soft matrices. Such tissues may be found in both plants and animals, as well as algae. Typically these tissues form a protective shield against predation or provide structural support.


History

Xavier Bichat Marie François Xavier Bichat (; ; 14 November 1771 – 22 July 1802) was a French anatomist Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology Biology is the natural science that studies life and living organisms, inclu ...
introduced word ''tissue'' into the study of
anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual conti ...

anatomy
by 1801. He was "the first to propose that tissue is a central element in
human anatomy The human body is the structure of a human being Humans (''Homo sapiens'') are the most populous and widespread species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an ...

human anatomy
, and he considered
organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tissues can be broadly cate ...
s as collections of often disparate tissues, rather than as entities in themselves". Although he worked without a
microscope A microscope (from grc, μικρός ''mikrós'' 'small' and ''skopeîn'' 'to look (at); examine, inspect') is a laboratory instrument used to examine objects that are too small to be seen by the naked eye Naked eye, also called bare ...

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.


See also

* * * *


References

* Raven, Peter H., Evert, Ray F., & Eichhorn, Susan E. (1986). ''Biology of Plants'' (4th ed.). New York: Worth Publishers. .


Sources

*


External links

*
List of tissues in ExPASy
{{Authority control Anatomy Tissues (biology)