Epithelial Tissues

Question 1

What are the four major tissue types in the body?

Answer 1

Epithelial, connective, muscle, and nervous tissue.

Question 2

What are the two components of epithelial tissues?

Answer 2

Epithelia (cell layers) and glands (secretory structures).
- The glands are attatched to or derived from epithelial tissue.

Question 3

What are the main functions of epithelial tissue?

Answer 3

Physical protection
Control permeability
Provide sensation
Produce specialized secretions

Question 4

What are the characteristics of epithelia?

Answer 4

• Made of cells which are held tightly together to form an effective barrier
• Cells have apical (top) and basal (bottom) surfaces with different structures and functions which are classed as two functional groups.
• Basement memebrane is a specialised from of extracellular matrix as it holds the tissue together.

Question 5

Why are epithelial tissues considered avascular?

Answer 5

They lack blood vessels and rely on diffusion for nutrients.

Question 6

What are the types of intercellular connections in epithelial tissue?

Answer 6

Junctions:
- Gap junctions, tight junctions, desmosomes, and hemidesmosomes.

Cell adhesion molecules (CAMS)
- Connect large areas of plasma membrane of adjacent cells
- Connect basal surface of epithelium with the basement membrane

Question 7

What is the role of gap junctions (connexons)?

Answer 7

• Allow ions and small molecules to move between cells for coordination (e.g., cardiac muscle).
• Coordinate muscle contractions in cardiac and smooth muscle tissue
• Allows diffusions

Question 8

What is the function of tight junctions?

Answer 8

• Prevent passage of water and solutes between cells.
• Protects the basal surface from contents of the extracellular environment by preventing any enzymes, acids, or waste from reaching the basal surface.

Question 9

What do desmosomes do?

Answer 9

• Provide strong cell-to-cell adhesion to resist twisting/stretching (e.g., skin).
• Links two cells by CAM and porteoglycans to the cytoskeleton.
• Maintains strong connections and are found in the superficial layers of our skin.

Question 10

What are hemidesmosomes?

Answer 10

• Anchor epithelial cells to the basement membrane.

Question 11

How is epithelial tissue maintained and repaired?

Answer 11

Through rapid division of stem cells located near the basement membrane.

Question 12

How are epithelial tissues classified?

Answer 12

By cell shape (squamous, cuboidal, columnar) and number of layers (simple, stratified).

Question 13

Where is simple squamous epithelium found and what is its function?

Answer 13

Lining of blood vessels (endothelium) and body cavities (mesothelium); allows diffusion and reduces friction.
- key function is difusion.

Question 14

What is the function of stratified squamous epithelium and where is it found?

Answer 14

• Provides protection against abrasion; found in skin, mouth, esophagus.
• key function is protection.

Question 15

Where is transitional epithelium found and what is its function?

Answer 15

Bladder and ureters; tolerates stretching and changes shape.

Question 16

What is pseudostratified columnar epithelium and where is it found?

Answer 16

Appears layered but all cells touch basement membrane; found in respiratory tract.

Question 17

What is the role of columnar epithelium with microvilli?

Answer 17

Increases surface area for absorption; found in intestines.

Question 18

What is the difference between endocrine and exocrine glands?

Answer 18

Endocrine: release hormones into interstitial fluid
Exocrine: release secretions onto epithelial surfaces, e.g. sweat glands release water onto the skin.

Question 19

What is a goblet cell?

Answer 19

• A type of cell in exocrine, unicellular glands which make and secrete mucous to protect the epithelium from pathogens.

Question 20

What are the three methods of exocrine secretion?

Answer 20

Merocrine (eccrine): via exocytosis (e.g., sweat glands)
Apocrine: apex of cell pinches off (e.g., mammary glands)
Holocrine: cell bursts (e.g., sebaceous glands)

Question 21

What are the three types of glandular secretions?

Answer 21

Serous: watery solution (e.g., parotid)
Mucous: mucin (forms mucus)
Mixed: both serous and mucous

Question 22

What determines the type of epithelium?

Answer 22

The number of layers and the shape of the cells at the apical surface.

Question 23

How does structure relate to function in epithelial tissues?

Answer 23

Cell shape and layering are adapted to specific roles such as protection, absorption, or secretion.

Question 24

What are tissues?

Answer 24

Collections of cells and cell products that perform specific, limited functions.

Question 25

What are the functional reigions of epthelia?

Answer 25

- Have different specialised structures: - Microvilli to increase the surface area to transport substances - cilia in the lungs which moves mucous to the throat. These are projections of the plasma membrane in gastrointestinal tracts and the cytoskeleton in other areas.

Question 26

How does the epithelia form a complete lining?

Answer 26

- Strong connections between cells - Attacthment to the basement membrane (basal surface) - maintenance and repair of the epithelium

Question 27

What is the function of simple cuboidal epithelium?

Answer 27

- Lines the glands, ducts, portions of kidney tubules, and thyroid glands - Offers limited portection, secretion and absorption of materials.

Question 28

What is the function of stratified cuboidal epithelium?

Answer 28

- rare - line some ducts of sweat glands - involved in protection, secretion, and absorbtion

Question 29

What is the role of simple columnar epithelium?

Answer 29

- Lining of stomach, intestine, gallbladder, collecting ducts of kidneys - Presence of microvili to increase surface area - Protection secretion and absorbtion

Question 30

What is the role of pseudostratified ciliated columnar epithelium?

Answer 30

- Lining of nasal cavity, trachea and bronchi, male reproductive tract - They are columnar epithelium with the presence of cilia to increase protection, secretion, and absorption.

Question 31

What is the role of stratified columnar epithelium?

Answer 31

- rare - small areas of the pharynx, epiglottis, anus, mammary glands, salivary duct - involved in protection

Question 32

Where is an exocrine unicellular gland located?

Answer 32

- located within the airways and intestines of the body - located WITHIN an epithelieum

Question 33

Where are exocrine multicellular glands located?

Answer 33

- Found in pockets and secreate into ducts before reaching the epithelial surface.

Question 34

How are epithelial tissue attatched to underlying connective tissue?

Answer 34

- The basement membrane

Question 35

Describe the role of each four major tissue types in the body.

Answer 35

- Epithelial: covers exposed surfaces, lines internal passageways and chambers, forms glands. - Connective tissue: fills internal spaces, provides structural support, transports materials, stores energy. - Muscle tisse: contracts for muscle action - Neural: carries information via electrical impulses