Histology: Body Tissues
Where are the General Locations of Epithelia?
1. Covers body surface: Skin/Cutaneous membrane,
2. Lines hollow organs: Mucous membrane *inside organ
3. lines internal cavities: Serous membrane/Serosa(on top of the organ)
*Double-layered sac in thoracic & peritoneal cavities (abdomino pelvic)
What are the General purposes for Epithelia?
1. Controls permeability: limits what can come in & out of the tissue, good at controling what enters & exits an orgain or cabity/space.
EX; *means epithelia helps hold water in body.
2. Provides protection: protects against damage & abrasion
What are Epithelium Special Features?
a. Tightly packed cells: *one reason why epithelia is good at controlling permeability
b. Rapid mitosis/Cell division: cells in organs are replaced every 4 days (every 15 days in skin)-->Means epithelia is good at growth and repair
c. Avascular: blood is supplied by tissue underneath epithelia
What are the Cell Shapes?
a. Squamous: scale like; thinnest cell type (things can move pass this b/c it's so thin)
b. Cuboidal: Square
c. Columnar: Tallest
What are the names of the Cell Layers & how many layers are there?
a. Simple: One layer of cells *Acutally not designed to control what enters and exits --> Very thin, allows things to pass in/out quickly.
b. Stratified: Multiple layers of cells *Very thick, so protective, and good at controlling permeability
Major Types & Locations
What's the purpose of Simple Squamous Epithelia, Give an Example?
Purpose: Allow substances to pass in/out quickly
EX: 1) Tissues used for gas(Oxygen) exchange: *In lungs-->Alveoli ALSO-->Blood vessels
2) Serous membranes (Serosa): Lines closed body cavities (No natural openings);
a. Pericardial cavity(HEART)
b. pleural cavities(LUNGS)
c. Peritoneal cavity(ABDOMINAL ORGANS) *Covers the organs
Stratified Squamous Epithelia
Thick tissue that is very protective (resists tearing). EX:
2. Buccal cavity
6. Eye--> Cornea(clear covering of the eye)
What's the purpose of Simple Cuboidal Epithelia?
Purpose: Forms glands
1) Liver glands (Bile glands)
2) Pancreas glands (digestive glands)
Stratified Cuboidal Epithelia
Purpose: In major glands; reproductive organs
1) Mammary glands (breast)
2) Ovarion follicle (makes eggs)
3) Vas deferens (contains sperm) spermatic duct
What's the purpose of Simple Columnar Epithelia, Give an Example?
Purpose: Absorption pulling something in-> (in to organ or blood)
1) Digestive organs:(Inside) Lining stomach, intestines
2) Bronchioles of lungs: Tubes in the lungs * have Cilia on top of the cells -->Cilia sweeps dirt, bacteria away from lungs.
What special feature does Pseudostratified Columnar have, Give an Example?
Special features: *Looks like multiple layers of cells, but only 1 layer
EX: Major respiratory air passageways;
*Pharynx (inner throat)