Histology and Types of Tissues

Study Notes

A tissue is a group of cells with similar structure and function plus extracellular substance (matrix)
Histology is the study of tissues

ECM helps bind tissues together structurally; it contains collagen, elastin, and glycoproteins.
ECM allows for local communication within a tissue through connection via integrins in plasma membranes.

Cover the body both internally and externally
Examples include skin, kidney, trachea, glands, and more.
Epithelial tissues are composed of cells that are close together with very little extracellular matrix.

Epithelial tissues form most glands and have a free surface called the apical surface.
The basal surface attaches epithelial cells to underlying tissues.

Classified by the number of cell layers (simple or stratified) and the shape of the cells (squamous, cuboidal, columnar, transitional)

Simple Squamous Epithelium: One layer of flat, tile-like cells; function: diffusion and filtration; location: blood vessels, lungs, kidneys
Simple Cuboidal Epithelium: One layer of square-shaped cells; function: secretion; location: glands, ovaries, kidneys
Simple Columnar Epithelium: One layer of tall, narrow cells; function: secrete mucus and absorption; location: stomach, intestines, respiratory tract
Pseudostratified Columnar Epithelium: One layer of tall, narrow cells that appears stratified but is not; function: secrete mucus and propel debris out of respiratory tract (cilia); location: nasal cavity and trachea

Stratified Squamous Epithelium: Many layers of flat, tile-like cells; function: protect and acts as a barrier; location: skin, mouth, throat, esophagus
Transitional Epithelium: Special type of stratified epithelium that changes shape (stretched squamous, not stretched cuboidal); function: hold fluids; location: urinary bladder

Stratified cuboidal: 2-3 layers of cube-shaped cells; line ducts of mammary glands, sweat glands, salivary glands, and the pancreas.
Stratified columnar: Top layer of elongated cells, rare type; found in lining of male urethra and a few other locations.