Chapter 4 objectives

Q: Characteristics of epithelial cells

Tightly packed, polarity (apical/basal), avascular, rest on basement membrane, high regeneration

Functions of cell junctions in epithelial cells

Tight: prevent leakage; Desmosomes: strength; Gap junctions: communication; Adherens: tissue stability.

Q: Functions of epithelial cell types

A: Squamous: diffusion/filtration; Cuboidal: secretion/absorption; Columnar: absorption/secretion; Transitional: stretch.

Q: Locations of epithelial tissue

A: Skin, organ linings, glands, blood vessels.

Q: Exocrine gland

A: Secretes substances into ducts or onto surfaces (e.g., sweat, oil).

Q: Types of exocrine secretion

A: Merocrine (exocytosis), Apocrine (cytoplasm pinched), Holocrine (cell ruptures).

Q: Examples of exocrine secretions

A: Sweat, oil, milk, saliva, digestive enzymes.

Q: Types of connective tissue & functions

A: Loose: cushioning; Dense: strength; Cartilage: support/flexibility; Bone: support/protection; Blood: transport.

Q: Specialized cells in connective tissue

A: Fibroblasts, adipocytes, chondrocytes, osteocytes, RBCs/WBCs.

Q: Steps of tissue repair

A: (1) Inflammation/clotting (2) Regeneration + fibrosis.

What does polarity mean in epithelial cells?

A: They have an apical (top) surface and basal (bottom) surface.

Q: Why are epithelial cells avascular?

• A: They rely on diffusion from underlying tissues for nutrients.

Q: What allows epithelial cells to regenerate quickly?

• A: High rate of stem cell division in the basal layer.

Q: What are the functions of cell junctions in epithelial cells?

A: Tight: prevent leakage; Desmosomes: strength; Gap junctions: communication; Adherens: stability.

Q: Which junction prevents substances from passing between cells?

• A: Tight junctions.

Q: Which junction provides mechanical strength?

Desmosomes

Q: Which junction allows ion/signal exchange?

A: Gap junctions.

Q: Which junction helps hold epithelial sheets together?

• A: Adherens junctions.

• A: They lack blood vessels; nutrients diffuse from underlying tissues.

Q: Why are epithelial cells avascular?

Q: What structure supports epithelial cells?

• A: The basement membrane.

Q: Why do epithelial cells regenerate quickly?

• A: High rate of stem cell division in the basal layer.

Q: Which junction prevents substances from slipping between cells?

• A: Tight junctions.

Q: Which junction provides mechanical strength by anchoring cells?

• A: Desmosomes.

Q: Which junction allows ions and signals to pass between cells?

• A: Gap junctions.

Q: Which junction links actin filaments for stability?

• A: Adherens junctions.

Q: What is an exocrine gland?

A: A gland that secretes substances into ducts or onto surfaces.

Q: What is the difference between exocrine and endocrine glands?

• A: Exocrine secrete into ducts/surfaces; endocrine secrete hormones into blood.

Q: What are examples of exocrine glands?

• A: Sweat glands, sebaceous (oil) glands, salivary glands, mammary glands.

Q: What are the three types of exocrine secretion?

A: Merocrine, Apocrine, Holocrine.

Q: How does merocrine secretion work?

• A: By exocytosis (e.g., sweat, saliva).

Q: How does apocrine secretion work?

• A: A portion of the cell’s cytoplasm is pinched off (e.g., milk, armpit sweat).

Q: How does holocrine secretion work?

• A: The entire cell ruptures and dies (e.g., sebaceous oil glands).

Q: What are the five main connective tissue types?

A: Loose, Dense, Cartilage, Bone, Blood.

Q: Function of loose connective tissue?

• A: Cushions, supports, stores fat.

Q: Function of dense connective tissue?

• A: Provides strength and attachment (e.g., tendons/ligaments).

Q: Function of cartilage?

• A: Support, flexibility, shock absorption.

Q: Function of bone?

• A: Structural support, protection, mineral storage, blood cell production.

Q: Function of blood?

• A: Transport gases, nutrients, immune defense.

Q: What are the specialized cells of connective tissue?

A: Fibroblasts, adipocytes, chondrocytes, osteocytes, RBCs, WBCs.

Q: What happens in inflammation/clotting?

• A: Damaged tissue releases signals, clot forms, prevents infection.

Q: What happens in regeneration/fibrosis?

• A: New cells replace damaged ones; scar tissue forms if severe.

• Fibroblasts →

• produce fibers (collagen, elastin).

• Adipocytes →

• store fat

• Chondrocytes →

• maintain cartilage.

• Osteocytes →

maintain bone 

• RBCs/WBCs/platelets →

• transport + immunity.

Exocrine glands

→ secrete into ducts or onto surfaces (sweat, oil, saliva). Function = localized effect

Endocrine glands →

secrete hormones into bloodstream (thyroid, pituitary). Function = systemic effect.

Loose connective (areolar, adipose, reticular)

→ support, cushion, fat storage.

Dense connective (regular, irregular, elastic)

→ strength and attachment (tendons, ligaments, dermis)

Simple squamous →

thin, flat; allows rapid diffusion & filtration (lungs, capillaries).

Stratified squamous →

multiple layers; protection from abrasion (skin, esophagus).

Simple cuboidal →

cube-shaped; secretion/absorption (kidney tubules, glands).

Simple columnar →

tall cells; absorption/secretion (intestines, stomach

Pseudostratified columnar →

cilia + mucus; trap & move particles (respiratory tract