Epithelial Tissues

Flashcards covering key concepts from lecture notes on Epithelial Tissues, including functions, characteristics, transport mechanisms, cell shape/layer classification, and glands.

What are the four primary functions of epithelial tissues?

Protection (acting as a barrier between inside and outside), absorption (from outside in), secretion (from inside out), and lining (separating one organ from another).

What does cellularity mean as a characteristic of epithelial tissue?

Cellularity means the tissue is composed entirely of cells with no extracellular material between them.

What does it mean that epithelial tissue is avascular?

It means epithelial tissue contains no blood vessels.

Why do epithelial tissues have a high rate of mitosis?

Because epithelial cells are constantly being lost or shed and must be continuously replaced.

How do active transport and passive diffusion differ in epithelial tissues?

Active transport utilizes transport proteins and requires energy, while passive diffusion requires no energy and relies on random molecular movement.

What are the basic structural layers of epithelial tissue from top to bottom?

Apical side, basal side, basement membrane (protein layer), and underlying connective tissue.

How is simple epithelium defined?

Simple epithelium consists of a single layer of cells where every cell touches both the apical and basal sides.

How is stratified epithelium defined?

Stratified epithelium consists of two or more layers of cells, meaning not all cells touch both the apical and basal sides.

What is pseudostratified epithelium?

Epithelium that falsely appears to have multiple layers due to cells of varying heights, though all cells remain attached to the basement membrane.

What are the physical characteristics of squamous epithelial cells?

They are flat, short, and wide cells containing a flat, oval ("pancake") nucleus.

What are the physical characteristics of cuboidal epithelial cells?

They have equal width and height with a round nucleus positioned in the middle.

What are the physical characteristics of columnar epithelial cells?

They are tall and narrow cells with oval nuclei located toward the basal side.

What are the primary functions and locations of simple squamous epithelium?

Functions: Rapid diffusion across barriers, filtration, and limited secretion. Locations: Lungs, kidneys, inner lining of blood vessels, and membranes of body cavities.

What are the functions and locations of simple cuboidal epithelium?

Functions: Passive diffusion and active transport across barriers, secretion, and absorption. Locations: Kidneys and thyroid gland.

What are the functions and locations of simple columnar epithelium?

Functions: Active transport across barriers, secretion, and absorption. Locations: Stomach, intestines, kidneys, parts of respiratory tract, and uterine tubes.

What threats does stratified squamous epithelium protect against, and where is it located?

Protects underlying layers against abrasion/cuts, chemicals, burns, and infections. Located in the skin, mouth, pharynx, esophagus, vagina, and anus.

Where are stratified cuboidal and stratified columnar epithelial tissues typically found?

They are rare and found in ducts.

What is the function and location of transitional epithelium?

Function: Cells flatten to allow for distension (stretching). Location: Urinary tract.

What features, functions, and locations characterize pseudostratified ciliated columnar epithelium?

Features cilia ("little hairs") on apical side; functions in protection as well as secretion and movement of mucus; located in nasal cavities and parts of the respiratory tract.

What type of cell is a unicellular gland, and what is its function?

Goblet cells, which function to secrete mucus.

What is the structural difference between endocrine and exocrine glands?

Endocrine glands are ductless and secrete directly into fluid, whereas exocrine glands possess ducts.