TissuesTissues

TissueTissue

A group of similar cells, usually of A group of similar cells, usually of similar embryonic origin, that similar embryonic origin, that function together to carry out function together to carry out specialized activitiesspecialized activities

HistologyHistology

The science that deals with the study The science that deals with the study of tissuesof tissues

Pathologist – a scientist who Pathologist – a scientist who specializes in laboratory studies of specializes in laboratory studies of cells and tissues to make accurate cells and tissues to make accurate diagnoses. A pathologist examines diagnoses. A pathologist examines tissues for any changes that might tissues for any changes that might indicate disease.indicate disease.

Types of TissuesTypes of Tissues Epithelial TissueEpithelial Tissue

Covers body surfaces; lines body cavities, Covers body surfaces; lines body cavities, hollow organs and ducts; forms glandshollow organs and ducts; forms glands

Connective TissueConnective Tissue protect and supports the body and its organs, protect and supports the body and its organs,

binds organs together, stores energy reserves binds organs together, stores energy reserves as fat, provides immunityas fat, provides immunity

Muscular TissueMuscular Tissue Generates the force needed to make body Generates the force needed to make body

structures movestructures move Nervous TissueNervous Tissue

Detects changes inside and outside the body Detects changes inside and outside the body and initiates and transmits nerve impulses that and initiates and transmits nerve impulses that coordinate body activities to help maintain coordinate body activities to help maintain homeostasishomeostasis

Cell JunctionsCell Junctions

Points of contact between plasma Points of contact between plasma membranes of different cells that membranes of different cells that join them into functional units.join them into functional units.

Epithelial TissueEpithelial Tissue

AKA EpitheliumAKA Epithelium 2 types:2 types:

Covering and Lining EpitheliumCovering and Lining Epithelium Forms the outer covering of the skin and Forms the outer covering of the skin and

some internal organs. It also lines body some internal organs. It also lines body cavities, blood vessels, ducts, and the cavities, blood vessels, ducts, and the interiors of many of the body systems.interiors of many of the body systems.

Glandular EpitheliumGlandular Epithelium Makes the secreting portion of glandsMakes the secreting portion of glands

General Features of General Features of EpitheliumEpithelium

1. Closely packed cells with little 1. Closely packed cells with little extracellular material between them extracellular material between them arranged in sheetsarranged in sheets

2. Surfaces:2. Surfaces: Apical Surface – exposed to a body cavity, Apical Surface – exposed to a body cavity,

the outside of the body or lining an the outside of the body or lining an internal organinternal organ

Lateral Surface – Face adjacent cellsLateral Surface – Face adjacent cells Basal Surface – bottom layer attached to Basal Surface – bottom layer attached to

a basement membrane (extracellular a basement membrane (extracellular structure composed mainly of fibers structure composed mainly of fibers located between epithelium and located between epithelium and underlying connective tissue)underlying connective tissue)

General Features of General Features of EpitheliumEpithelium

3. Avascular – no blood vessels. 3. Avascular – no blood vessels. Epithelial cells must get their Epithelial cells must get their nutrients from underlying connective nutrients from underlying connective tissue through diffusiontissue through diffusion

4. Innervated (have a nerve supply)4. Innervated (have a nerve supply) 5. High mitotic rate – high capacity 5. High mitotic rate – high capacity

for cell division because of wear and for cell division because of wear and tear and injurytear and injury

Covering and Lining Covering and Lining Epithelium – Cell ShapesEpithelium – Cell Shapes

Squamous – flat cells that attach to each Squamous – flat cells that attach to each other like tilesother like tiles Allows for rapid passage of substances through Allows for rapid passage of substances through

themthem Cuboidal – cells are as tall as they are wide, Cuboidal – cells are as tall as they are wide,

sometimes contain microvillisometimes contain microvilli Function in Secretion and AbsorptionFunction in Secretion and Absorption

Columnar – Taller than they are wide, Columnar – Taller than they are wide, sometimes contain microvilli or ciliasometimes contain microvilli or cilia Function in Secretion, Absorption and ProtectionFunction in Secretion, Absorption and Protection

Transitional – Cells that have the ability to Transitional – Cells that have the ability to change shape from Cuboidal to Squamous change shape from Cuboidal to Squamous and back as organs stretchand back as organs stretch

Simple EpitheliumSimple Epithelium

A single layer of cells found in areas A single layer of cells found in areas where diffusion, osmosis, filtration, where diffusion, osmosis, filtration, secretions and absorption occursecretions and absorption occur

Simple Squamous Simple Squamous EpitheliumEpithelium

A single layer of flat cells that A single layer of flat cells that resembles a tile floor when viewed resembles a tile floor when viewed from the apical surfacefrom the apical surface

Nucleus is a flattened oval found in Nucleus is a flattened oval found in the center of the cellthe center of the cell

Found where filtration or diffusion Found where filtration or diffusion take place, not found in areas of high take place, not found in areas of high wear and tearwear and tear

Simple Squamous Simple Squamous EpitheliumEpithelium

Endothelium – simple squamous that Endothelium – simple squamous that lines the heart, blood vessels and lines the heart, blood vessels and lymphatic vessleslymphatic vessles

Mesothelium – simple squamous that Mesothelium – simple squamous that lines serous membranes (lines lines serous membranes (lines cavities not open to the outside of cavities not open to the outside of the body, like the abdomen or the body, like the abdomen or thorax)thorax)

Simple Cuboidal EpitheliumSimple Cuboidal Epithelium

Single layer of cube shaped cellsSingle layer of cube shaped cells Found on the surface of the ovary, Found on the surface of the ovary,

the lens of the eye and lining of the lens of the eye and lining of glands as well as the secreting glands as well as the secreting portion of glandsportion of glands

Function in Secretion and AbsorptionFunction in Secretion and Absorption

Simple Columnar EpitheliumSimple Columnar Epithelium

Single Layer of Column Shaped CellsSingle Layer of Column Shaped Cells 2 Forms – cilliated and noncilliated2 Forms – cilliated and noncilliated

Non-cilliated Simple Non-cilliated Simple Columnar EpitheliumColumnar Epithelium

Contains absorptive cells and goblet Contains absorptive cells and goblet cellscells Absorptive Cells – have microvilli to Absorptive Cells – have microvilli to

increase surface areaincrease surface area Goblet Cells – modified Columnar cells Goblet Cells – modified Columnar cells

that secrete mucus at the apical surfacethat secrete mucus at the apical surface Lines most of the GI tract, ducts of Lines most of the GI tract, ducts of

glands and gallbladderglands and gallbladder

Ciliated Simple Columnar Ciliated Simple Columnar EpitheliumEpithelium

Cells with cilia at the apical surface, Cells with cilia at the apical surface, usually interspersed with goblet cellsusually interspersed with goblet cells

Mucus secreted by goblet cells forms Mucus secreted by goblet cells forms a thin layer over the cell surface a thin layer over the cell surface which is moved by the ciliated cells.which is moved by the ciliated cells.

Found in the respiratory tractFound in the respiratory tract

Stratified EpitheliumStratified Epithelium

Contains 2 or more layers of cells Contains 2 or more layers of cells used for protection of underlying used for protection of underlying tissue in area where there is a lot of tissue in area where there is a lot of wear and tearwear and tear

The name of the tissue depends on The name of the tissue depends on the shape of the cell on the apical the shape of the cell on the apical layerlayer

Stratified SStratified S quamous quamous EpitheliumEpithelium

Cells in the apical layer are flatCells in the apical layer are flat Cells in the deep layers vary in shapeCells in the deep layers vary in shape Basal cells continuously undergo Basal cells continuously undergo

mitosismitosis As they move farther from the basal As they move farther from the basal

layer they become dehydrated and layer they become dehydrated and harderharder

Keratinized Stratified Keratinized Stratified Squamous EpitheliumSquamous Epithelium

Tough layer of keratin is deposited Tough layer of keratin is deposited on the top layers to help protect the on the top layers to help protect the skin and underlying tissues from skin and underlying tissues from microbes, heat and chemicalsmicrobes, heat and chemicals

Nonkeratinized Stratified Nonkeratinized Stratified Squamous EpitheliumSquamous Epithelium

Does not contain keratinDoes not contain keratin Found on the lining of the mouth, Found on the lining of the mouth,

esophagus, and tongueesophagus, and tongue

Stratified Cuboidal Stratified Cuboidal EpitheliumEpithelium

Fairly RareFairly Rare 2 or more layers of cells, apical layer 2 or more layers of cells, apical layer

is cuboidalis cuboidal Found in sweat glandsFound in sweat glands

Stratified Columnar Stratified Columnar EpitheliumEpithelium

Fairly RareFairly Rare 2 or more layers of cells, the top 2 or more layers of cells, the top

layer is columnarlayer is columnar Found in excretory ducts of some Found in excretory ducts of some

glands and some mucous glands and some mucous membranesmembranes

Transitional EpitheliumTransitional Epithelium

Varies in appearance depending on Varies in appearance depending on whether the organ it lines is whether the organ it lines is distended or relaxed.distended or relaxed. Looks similar to stratified cuboidal Looks similar to stratified cuboidal

except the top layer is large and except the top layer is large and roundedrounded

Pseudostratified Columnar Pseudostratified Columnar EpitheliumEpithelium

Appears to have several layers Appears to have several layers because the nuclei of the cells are at because the nuclei of the cells are at various depths.various depths.

All of the cells are attached to the All of the cells are attached to the same basement membrane so there same basement membrane so there is only 1 layer of cellsis only 1 layer of cells

Glandular EpitheliumGlandular Epithelium Functions in SecretionFunctions in Secretion A gland consists of one cell or a group A gland consists of one cell or a group

of cellsof cells

Endocrine Glands – secretions enter Endocrine Glands – secretions enter the interstitial fluidthe interstitial fluid HormonesHormones

Exocrine Glands – secrete their Exocrine Glands – secrete their products into ducts (tubes) that empty products into ducts (tubes) that empty at the surface of the covering/lining at the surface of the covering/lining epitheliumepithelium Mucus, oil, earwax, digestive enzymesMucus, oil, earwax, digestive enzymes