Chapter 3 Human Anatomy Study Guide

What are the four main categories of tissue?

Nervous, epithelial, muscle, and connective.

What is epithelial tissue?

A sheet of cells that covers or lines a body surface or cavity.

What are the two forms of epithelium?

(1) Epithelia that cover and line cavities, walls, and surfaces.
(2) Epithelia that form glands.

Where can epithelial cell layers be found?

Outer skin, walls of body cavities, linings of gastrointestinal and urinary tracts.

What role does epithelium play as a barrier?

Substances must pass through it to enter or exit the body.

What is an example of epithelium in action?

Kidney tubules, where sodium is absorbed and hydrogen is excreted.

What are glands in relation to epithelium?

Single cells or layers of epithelial cells that form folded structures and secrete specific products.

What are some secretions produced by glandular epithelia?

Sebum, insulin, sweat, and saliva.

What are the key functions of epithelial tissues?

Protection, absorption, secretion, and excretion.

What are some additional functions of epithelial tissues?

Filtration and sensory reception.

How are epithelial cells arranged?

They are tightly packed with little space in between.

What does this tight arrangement help with?

It enables barrier and absorptive/secretive functions.

What prevents most transport between epithelial cells?

Intercellular junctions.

What are the most common intercellular junctions?

Tight junctions, hemidesmosomes, and desmosomes.

What do hemidesmosomes do?

Form adhesions between cells and the basement membrane.

What do desmosomes do?

Form direct cell-to-cell adhesions.

What two surfaces are formed by epithelial cells?

Apical surface and basolateral surface.

Where is the apical surface located?

It is exposed to the external body cavity or the lumen of a hollow organ.

Where is the basolateral surface located?

It is tethered to the basement membrane.

What is the basement membrane made of?

Connective tissue.

What is the role of the basement membrane?

It establishes the epithelial boundary, resists tears, and reinforces tissue.

What special features can the apical surface have?

Microvilli (increase absorption area) and cilia (propel molecules along the surface).

What is the organization of epithelial cells into distinct sidedness called?

Polarity (or polarization).

Why is polarity important in epithelial cells?

It allows selective movement of substances between the apical surface (openings/lumens) and the basolateral surface (bloodstream).

What is an example of polarity in action?

Nutrients absorbed across the small intestine lining into the blood.

Why is movement of nutrients through the epithelium into the bloodstream important?

Because epithelial tissue is avascular and depends on diffusion from blood vessels in underlying connective tissue.

Where are the blood vessels located that nourish epithelial cells?

In the underlying connective tissue.

Why do epithelial linings face damage?

Because of friction and exposure to pathogens or chemical toxins.

How do epithelial cells repair themselves when damaged?

They undergo mitosis to regenerate.

What is an important characteristic of the epithelium?

High capacity for regeneration.

How are epithelial tissues classified?

By the number of cell layers and by cell shape.

What does the first part of an epithelial tissue’s name indicate?

The number of cell layers.

What does the second part of an epithelial tissue’s name indicate?

The shape of the cells.

What is a single layer of epithelial cells called?

Simple tissue.

What is a tissue with more than one layer of cells called?

Stratified tissue.

What are the possible shapes of epithelial cells?

Squamous, cuboidal, columnar, or transitional.

What is a simple epithelial tissue?

A single layer of cells found in locations where a thin tissue layer is needed for absorption, secretion, and filtration.

What is a stratified epithelial tissue?

Two or more layers of cells stacked to provide protection in areas of high friction and exposure.

What is a pseudostratified epithelial tissue?

A single layer of columnar cells that looks like multiple layers because the nuclei are at different heights.

What is a squamous epithelial cell?

Flat and scale-like.

What is a cuboidal epithelial cell?

Height is about equal to width; box-like.

What is a columnar epithelial cell?

Tall and rectangular-shaped.

How can the nucleus help identify epithelial cell shape?

The nucleus usually takes the shape of the cell: oval and elongated in columnar cells, spherical in cuboidal cells.

In stratified epithelia, which cells determine the classification?

The shape of the cells in the top layer.

What do simple epithelial tissues most often do?

They function in absorption, secretion, and filtration.

What is simple squamous epithelium made of?

Flattened cells assembled into a dense pattern with other squamous cells.

What do individual simple squamous cells look like?

They often resemble fried eggs with flat nuclei and little cytoplasm.

Why is the flat, thin surface of simple squamous epithelium important?

It allows diffusion, secretion, absorption, and filtration.

Where is simple squamous epithelium commonly found?

In the walls of air sacs (alveoli) and kidney tubule glomeruli.

What is endothelium?

A specialized type of simple squamous epithelium lining lymphatic and blood vessels.

Why is the endothelium lining important?

It minimizes friction, allowing lymph or blood to pass through vessels easily.

How thick is a capillary?

One cell thick, made entirely of endothelium.

Why is a capillary being one cell thick important?

It maximizes efficient exchange of gases and nutrients between blood and tissues.

What is simple cuboidal epithelium made of?

Cube-shaped cells that are equally tall and wide.

What is simple cuboidal epithelium good for?

Secretion and absorption.

Where is simple cuboidal epithelium found?

In glands and kidney tubules.

What is simple columnar epithelium made of?

A layer of tall, tightly packed cells.

What special features can simple columnar cells have?

Cilia (for propulsion) or microvilli (for absorption).

Where is simple columnar epithelium commonly found?

Lining the digestive system.

What do microvilli in the digestive system do?

They enhance absorption of nutrients.

What additional structures do columnar cells form in the stomach and small intestine?

Folds with deep tubular pits.

What is the function of these folds and pits?

To secrete mucus and intestinal juice.

What is pseudostratified columnar epithelium?

A type of columnar epithelium where cells have different heights and thicknesses, making it look like multiple layers.

Are the cells in pseudostratified columnar epithelium actually at different heights?

No, only the nuclei are at different levels, creating the appearance of layers.

Where is pseudostratified columnar epithelium commonly found?

In the respiratory tract.

What special feature do these cells have on their apical surface?

Cilia, which help move dust and microbes away.

What are goblet cells, and what do they do?

Cells that secrete mucus to trap particles and prevent invasion or irritation.

What characteristic does the simple columnar epithelium that forms absorptive cells of the digestive tract have?

Dense microvilli.

What does pseudostratified columnar epithelium, ciliated variety, do?

It lines most of the respiratory tract.

What do multiple layers of epithelial cells provide?

Greater durability and protection.

How does stratified epithelium regenerate?

Basal cells divide and move toward the apical surface to replace the top layer.

What is much of the dust in our homes made of?

Sloughed-off human skin cells.

What is the most common stratified epithelial tissue?

Stratified squamous epithelium.

Why is stratified squamous epithelium thick?

It provides protection in areas exposed to deterioration.

What do basal and surface cells look like in stratified squamous epithelium?

Basal cells are cube-like, and surface cells are flattened and squamous.

How do stratified layers of cells get nutrients?

By diffusion from underlying connective tissue.

What does it mean if the top layer is keratinized?

It is enriched with tough keratin protein, giving strength and integrity.

Where is keratinized epithelium commonly found?

In the epidermis of the skin and tissues subject to abrasion.

Where are stratified epithelia usually located?

In areas transitioning from an outside opening to an internal cavity or orifice.

Where are stratified cuboidal and columnar epithelia enriched?

In glandular tissues.

Where is stratified cuboidal epithelium found?

In sweat and mammary ducts.

Where is stratified columnar epithelium found?

In some glandular ducts, the pharynx, and the male urethra.

Where else can stratified columnar epithelium be found?

In areas where tissues transition between two types of epithelia, such as at the junctions between the pharynx and trachea.

How common are stratified cuboidal and stratified columnar epithelia?

They are relatively rare.

What is transitional epithelium?

A special type of stratified epithelium where cells change shape in response to stretch.

What shape are the cells in the basal levels of transitional epithelium?

Cuboidal or columnar.

What shape are the cells in the top layers of transitional epithelium?

Rounded or squamous, depending on the degree of stretch.

Where is transitional epithelium found?

Along the lining of urinary tubes such as the ureter and urethra.

Why does transitional epithelium need to stretch?

Because it carries urine to and from the bladder.

What happens to the top layers of transitional epithelium when the bladder expands?

They flatten and thin out.

What are glands made of?

One or more epithelial cells.

What process do glands use to release a product?

Secretion.

How are glands classified?

By the number of cells (unicellular or multicellular) and where they release their product.

What are endocrine glands?

Glands that secrete their product into localized capillaries.

What are exocrine glands?

Glands that secrete their product into a duct.

Where are unicellular glands found?

Interspersed throughout epithelial tissue.

What are multicellular glands like?

They are more complex and form deeper invaginations within the epithelial sheet.

What do these invaginations, or ducts, do?

They form tube-like connections to the surface of the skin or organ.

What are endocrine glands also called?

Ductless glands.

What do endocrine glands produce?

Hormones.