Epithelial Tissues Overview (Grade A)

Summary:

Epithelial tissues come in three primary shapes: squamous (thin and flat), cuboidal (box-like), and columnar (elongated rectangles). These can be single-layered (simple) or multi-layered (stratified). Simple squamous is located in blood vessels and the heart, functioning in absorption or secretion, and appears as a single flattened layer. Simple cuboidal, found in glands and kidneys, serves the same function with a cube-like, single-layer appearance, highlighted by a circular nucleus. The simple columnar, lining the stomach and intestines, features an oval-shaped nucleus with some showing microvilli structures. Stratified tissues are predominantly protective. Stratified squamous is on the skin’s surface, cuboidal lines some ducts and is rare, while columnar can be found in mammary and salivary glands. Transitional tissue in the urinary system changes form based on the bladder’s state, often appearing inconsistent. Pseudostratified tissue, recognizable by its cilia resembling messy hair, is located in the trachea and nasal cavities, offering protection and secretion. Generally, simple epithelial tissues are for absorption and secretion, while stratified are for protection, with stratified cuboidal being an exception.

Excerpt:

Epithelial Tissues Overview

3 Shapes:
1. Squamous (thin and flat)
2. Cuboidal (small boxes)
3. Columnar (slender rectangles)

Can be different layers
● Single layer (simple)
● Several layers (stratified)

Simple Squamous
● Location: Lining of blood vessels, heart, ventral body cavity, etc
● Function: Absorption or Secretion
● Looks squished, only 1 layer

Simple Cuboidal
● Location: Glands, ducts, kidney tubules
● Function: Absorption or Secretion
● 1 layer of cubes
● Nucleus is a circle

Simple Columnar
● Location: Lining of the stomach, intestines, gallbladder, uterine tubes, and kidney ducts
● Function: Absorption or Secretion
● Nucleus is oval shaped
● Easily differentiated because of how much space is between the nucleus and the membrane
● Top pink part (ribbon-like structure) is microvilli
● Not all have it, but intestines do have it

Stratified Squamous
● Location: Surface of the skin
● Function: Protection

Stratified Cuboidal
● Location: Lining of some ducts
● Function: All 3 functions
● Rarest Epithelial