Tissues Epithelial Tissue

Four Main Types of Tissue: Tissue: mass of specialized cells that work together to perform a specific function Four Main Types of Tissue: Connective Epithelial Muscle Nervous

Epithelial Tissue Includes : Epithelia: layer of cells on the outside of EVERYTHING (not just skin, but lines intestinal and respiratory tracts, stomach lining, etc) Exocrine Glands: produce fluid secretions Sweat, oil

Characteristics of Epithelium Attached to underlying connective tissue by a basement membrane Usually has no vascular tissue, which means there is no blood supply Epithelial cells reproduce rapidly which allows them to also heal quickly Cells packed tightly together

Epithelial cells = firmly attached to one another Cell Junctions: attachment sites Tight Junctions: allows no passage of water or solutes ex: stomach 2. Gap Junctions: narrow passageways that allow diffusion ex: muscles 3. Desmosomes: many bands and interconnections ex: skin

Functions of Epithelia 1. Provide Protection 2. Control Permeability (what comes in and goes out) 3. Provide Sensation 4. Produce Specialized Secretions

Classifications of Epithelia Classified by cell shape and number of cells in layers 3 Shapes: (1) Squamous (thin, flat cells) (2) Cuboidal (boxy) (3) Columnar (long,thin rectangular) Number of Cells in Layer Simple (1) Stratified (>1)

Types of Epithelia Six Main Types of Epithelial Tissue: Simple Squamous Simple Cuboidal Simple Columnar Stratified Squamous Pseudostratified Columnar Transitional Epithelial

Simple Squamous Single layer (simple) of thin, flattened cells (squamous) Functions to facilitate diffusion of gases and filtration Found in air sacs of lungs and capillary walls

Simple Cuboidal Single layer (simple) cube-shaped cells (cuboidal) Functions to secrete and absorb Found in the lining of kidney tubules, gland ducts, and covers the surface of the ovaries

Microvilli used to aid in absorption – increases surface area Simple Columnar Single layer (simple) rectangular-shaped cells in about the same position in each cell Functions to secrete, absorb, and protect Found in digestive tract and uterus lining Microvilli used to aid in absorption – increases surface area

Stratified Squamous Multiple layers (stratified) of flattened cells (squamous) Functions to protect Found in body cavities like the mouth and outer layer of the skin Why is this good tissue for outer layer of skin?

Stratified Squamous It takes about 27 days for the outer layer of skin to be shed and replaced; that adds up to about 1.5 pounds of skin cells shed per year!! Where does all that dead skin go?

Tattoos If skin is constantly being replaced, where does ink need to be injected so tattoo doesn’t “shed” away? The ink must be injected below the basement membrane

Pseudostratified Columnar “Pseudo” means false, stratified means many layers Psuedostratified looks like many layers but really a single layer with nuclei at different levels, giving appearance of layered cells Functions to secrete and has cilia to aid in the movement of materials like mucus or eggs Found in the lining of trachea and fallopian tubes of the female reproductive system

Pseudostratified Columnar Cilia Goblet Cells Basement Membrane Goblet Cells secrete mucus while the cilia “sweep” the mucus through the respiratory tract

Transitional Epithelium Looks like thick layers of cuboidal cells It is “stretchable” tissue, and forms a barrier to prevent diffusion from occurring Found in the lining of the urinary bladder to prevent “leaking” Notice scalloped edges characteristic of transitional epithelial tissue

Transitional Epithelium Relaxed tissue Contracted tissue

Growing an Ear…

Cuboidal Columnar Simple Stratified Epithelial Tissue Squamous Location: Lungs and blood vessels Functions: Diffusion and filtration Glands, kidneys, ovaries Secretion and absorption of fluids Uterus and digestive organs (stomach and intestines) Absorption/lubrication Stratified Skin, throat, mouth Protection due to layers Lining of glands/ducts including mammary and sweat Protection for glands making fluids Respiratory tract Filtration due to cilia

What type of epithelial tissue is shown below?

What type of epithelial tissue is shown below?

What type of epithelial tissue is shown below?

What type of epithelial tissue is shown below?

What type of epithelial tissue is shown below?