Epithelial tissue study guide

Keratinized epithelial tissue
Dead tissue layers that pile up on top of each other for more protection

Functions of epithelia
. Physical protection
. Permeability control
. Sensation trigger
. Specialized secretions

Characteristics of epithelia
. Cells closely packed
. Apical cells exposed to external or internal surface
. Cells attached to basement membrane
. Lack blood cells
. Cells continuously replaced
. Can form pockets and function as glands

Glands
Secretory structures derived from epithelia

Epithelium
An avascular (without blood vessels) layer of cells that forms a barrier that covers internal or external surfaces

Epithelial surface
The 2 classes of the epithelial surface are microvilli and cilia

Microvilli
. Abundant on transport cells
. Dramatically increase surface area
. Found in intestinal lining, kidney tubules

Cilia
. Beat in coordinated fashion
. Move fluid along surface
. Found in airways, oviduct

Classifying epithelia
Layers
. Simple- one cell thick
. Stratified- multiple cells thick
Shape
. Squamous- flat
. Cuboidal- cubic
. Columnar- tall columns

Basement membrane
. Noncellular mesh work anchors basal cells
. Underlies all epithelia
. Hemidesmosomes attach basal cells
. Resists passage of large molecules
. Strengthens against distortion
. Nourishes the cells in the epithelium by the diffusion of nutrients

Endocrine secretion
Secretion (of hormones) into neighboring tissues and blood

Exocrine secretion
Secretion onto a body surface

Ciliated epithelial tissue
Catches foreign particles and moves them away from the lungs

Stratified cuboidal epithelium
Description
Arranged in 2 or more layers of cuboidal cells
Function: protection
Location: ducts of mammary glands, sweat glands, and salivary glands

Simple squamous epithelium description
Description: single layer of cells that are flat with sparse cytoplasm and a disc-shaped nuclei

Simple squamous epithelium function
Function: passage of materials by diffusion and allows filtration in areas where protection isn’t important, secretes lubricating substances in serosae

Simple squamous epithelium location
Location: kidney glomeruli, air sacs of lungs, lining of heart, blood vessels, lymphatic vessels, lining of ventral body cavity (serosae)

Stratified squamous epithelium description
Description: thick membrane composed of several cell layers, basal cells are cuboidal or columnar and metabolically active, surface cells are flattened, surface cells are full of dead keratin, basal cells are active in mitosis and produce the cells of the more superficial layers

Stratified squamous epithelium function
Function: protects underlying tissues in areas subjected to abrasion

Stratified squamous epithelium location
Location: nonkeratinized- moistnlinings of esophagus, mouth, vagina
Keratinized- forms epidermis of the skin, a dry membrane

Transitional epithelium description
Description: transitioning from one cell shape to another, resembles both stratified squamous and stratified cuboidal, basal cells are columnar, surface cells dome shaped or squamous like, depending on degree of organ stretch

Transitional epithelium function
Function: stretches, permits distention of urinary organ by contained urnine

Transitional epithelium location
Location: Lines the ureters, bladder, and part of the urethra

Simple cuboidal epithelium description
Description: Single layer of cube like cells with large, spherical nuclei

Simple cuboidal epithelium function
Function: secretion and absorption

Simple cuboidal epithelium location
Location: kidney tubles, ducts, secretory portions of small glands, ovary surface

Stratified columnar epithelium description
Description: arranged in two or more layers of columnar cells

Stratified columnar epithelium function
Function: secretion and protection

Stratified columnar epithelium location
Location: ocular conjunctiva of the eye, anus, pharynx, uterus, urethra, vas deferens, salivary glands

Simple columnar epithelium description
Description: single layer of tall cells with round to oval nuclei, some cells bear cilia, layer may contain mucus secreting unicellular glands (goblet glands)

Simple columnar epithelium function
Function: absorption, secretion of mucus, enzymes, and other substances, ciliated type propels mucus (or reproductive cells) by ciliary action

Simple columnar epithelium location
Location: digestive tract, gallbladder, excretory ducts of some glands, ciliated variety Lines small bronchi, uterine tubes, some regions of uterus

Pseudostratified columnar epithelium description
Description: one layer of cells but location of nuclei makes it look stratified, single layer of cells of different heights, Sam don’t reach free surface, nuclei seen at different levels, may contain mucus secreting goblet cells and bear cilia

Pseudostratified columnar epithelium function
Function: secretion (particularly of mucus), propulsion of mucus by ciliary action

Pseudostratified columnar epithelium location
Location: non ciliated type in males sperm carrying ducts and ducts of large glands, ciliated variety lines in trachea, most of the upper respiratory tract

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