Epithelial Tissues Flashcards
Macroscopic vs microscopic anatomy
Macroscopic: (gross anatomy)-study of structures that can be seen with the naked eye. Learning the names, locations of muscles, bone, arteries, veins, and nerves
Microanatomy: Study of microscopic structures and organs - AKA Histology
Tissue types
epithelial, connective, nervous, muscle
Epi tissue is composed of
cells that cover and line other tissues (bladder, mouth, blood vessels, and thorax [all body cavities])
Epi acts as
interface layer that separates and defines the beginning and ending of different tissues
Epi provides _____, has _________ aspects, and _________ things
-Provides protection - often acts as a biochemical filter (skin) and can be absorptive (GI epi - nutrients)
-Has sensory aspect (tongue, eyes, nasal passages) - Touch, temp, and taste
-Secrets things - Glandular epi
Individual glandular epi cells
Goblet cells - found in the intestines (lubrication)(colon mucous)
Grouped glandular epi cells
Pancreas
Make important substances (hormones, enzymes, milk, sweat, and musk)
Excretions vs secretions
Excretions are waste
Secretions are products of that cell (needed by the body)
Characteristics of epi
The size and shape of cells are based on it’s location and function in the body, but all are:
Polar, have junctional complexes, are avascular, and are innervated
Polar
Have a sense of direction
Apical surface - side of the cell that faces the lumen (innermost section of a hollow organ)
Basal Surface - Side of the cell that faces the underlying CT (concretes the organ to its location)
Junctional Complexes
Bring cells into close apposition to one another (close together)
Leave little to no room for extracellular matrix, if one does exist, it is very small
Avascular
No blood supply to the cells
They rely on underlying CT to provide O2 and nutrients
Innervated
Some epi lack nerves (Stomach, intestines, cervix)
Most are innervated (has nerves) and provide valuable sensory input
Basement Membrane (BM): AKA basal lamina
-Foundation of the epi cell - a nonliving meshwork of fiber - acts as cement to the underlying CT (strong and elastic)
-Made and laid down by epi cells in varying degrees of thickness
-Nutrients and excremet diffuse across the BM to either be absorbed & used by epi (nutrients) or excreted in the blood stream for waste disposal (excrement)
Surface specializations :
Vary depending on location and role it plays
Some have a smooth surface
Others have an irregular surface
Smooth Surface
Blood vessels
Allow for easy passage of red blood cells (prevents clots)
Irregular surfaces
Microvilli
Cilia
Microvilli
Fingerlike projections
Brush border
-The surface area of the cell is covered in microvilli
-Greatly increases SA (20X)
-Increase absorptive ability of the cell (involved with secretions or absorptions)
-Found in intestines and urinary tracts
Cilia
Thousands of tiny hairs
Found on the free surface (apical surface) of cells
-Resp tract - Trachea - Propel mucus and debris away from lungs
-Urogenital tract (repro) - Oviduct (infundibulum) - Cilia gently move new ova into the oviduct
Classify Epi based on 3 criteria
Number of cell layers
Shape of the cells
Presence of surface specialization
Single layer of cells
Simple
Provides little protection to the underlying CT
Found in protected areas of the body (Ducts, vessels etc.)
Miltiple layers of cells
Stratified
Thicker and stronger
Found in areas that undergo mechanical and chemical stress
Shapes of cells
Squamous, Cuboidal, and Columnar
In stratified epi - Many diff shapes are visible within the same tissue
Classified based on the shape of the luminal surface
Simple Squamous Epi
-Delicate and thin
-Lining surfaces involved with the passage of gas or liquids - the inner lining of lungs (O2/CO2 exchange)- Filtration membrane of kidneys (Water and molecules excreted as urine)
- Flat and smooth - Reduces friction (blood vessels and lymphatics)
-Special named depending on location - Mesothelium (lines the pleural, pericardial, and peritoneal) - Endothelium (Line vessels and lymphatics)
Simple cuboidal
Single layer of cubic cells
Dark nuclei are in a single row (Like a string of pearls)
Little protection
Secretion and absorption - Ovary surface, thyroid gland, ducts (of liver, pancreas, kidney [has microvilli], and salivary glands)
Simple Columnar epi
-Elongated and tightly packed - Makes them tougher than simple squamous or cuboidal
-Nucleus at the base of the cell near the basement membrane
-Found in the GI tract - From stomach to the rectum - Associated w/ absorption and secretion - found in many excretory ducts
- Two types of cells make up gut lining - Absorptive (Most numerous, apical surface, dense microvilli) - Goblet (Wine glass shape, make and store mucus)
- Simple Ciliated columnar - uterine tubes, resp tract
Stratified Squamous Epi (Stratified Squamous Keratinized Epi)
Various cell layer
in areas that undergo chemical and mechanical stress - Mouth, esophagus, vagina, rectum
Outer layer always being worn or shed off - replace at an equal rate from deeper layer
** Stratified Squamous Keratinized Epi is found on skin **
Stratified Cuboidal Epi
Salivary ducts/glands and mouth
Stratified Columnar Epi
Rare
Found in repro, resp, digestive, excretory ducts
Pseudostratified Ciliated Columnar Epithelium
False Stratified - nuclei area found at diff levels across length of tissue layer - not all cells reach lumen (Appears to have multiple layers ) - all are attached to the BM
-is considered a simple epi
-Most ciliated - resp, some in male repro
Transitional Epi
-Stretches
-Found in areas that need to expand and contract - Urinary tract (bladder, ureters, urethra)
- Can change the appearance of the cells - Empty urinary bladder (Thick, multilayers, domelike on the luminal surface) - Filled urinary bladder (go from 6 layers to 3 layers) - Forms a leak-proof membrane that prevents diffusion (Don’t want urine in the abdomen)
