Epithelial Tissue

Question 1

Location of epithelial tissue

Answer 1

Lining of external surfaces
Lining of internal cavities
glandular tissue

Question 2

Functions (Exam)

Answer 2

Protection
Secretion
Absorption

Selective barrier
Transportation (cilia)
Receptor functions

Question 3

Classification (Exam)

Answer 3

Nr. of layers

• simple (1 layer)
• stratified (more than 1 layer)
• pseudostratified (1 layer but looks like more)

Shape of cell in contact with surface

• Squamous (flat)
• Columnar (tall, thin)
• Cuboidal (squares

Specialization of the apical cell

• Keratinized (accumulation of keratin filaments)
• Ciliated (presence of cilia)

Question 4

Structure

Answer 4

Little to no ECM.
Highly cellular tissue.
Avascular.
Cells have polarity with differences in structure and function between the different surface domains (basal lamina vs. surface).
-Apical domain
-Lateral domain
-Basal domain

Question 5

Apical domain

Answer 5

Exposed to the surface.

• Microvilli: Finger like cell structures that increase surface in apical region to increase cells absorptive capacity.
• Cilia: 9 pairs of microtubules arranged in a circle. Allow the movements of substrates across the surface

Question 6

Lateral Domain

Answer 6

Cell to cell adhesion.
Tight junctions
Anchoring junctions
Gap junctions

Question 7

Tight junctions

Answer 7

Lateral domain
Allow Epithelia to be a selective barrier.
Seal intercellular space between adjacent cells.
Substrates can cross by transcellular pathway or paracellular.
Tightness of junctions can be modulated.

Question 8

Anchoring Junctions

Answer 8

Lateral domain
Provide mechanical stability to epithelial cells.
-Adherens junctions
Connect microfilaments from neighboring cells
-Cadherins: Homophilic binding proteins that connect the filaments
cell to cell adhesion
-Desmosomes
Connect intermediate filaments from neighboring cells.
Great mechanical resistance, stability.

Question 9

Gap junctions (Exam)

Answer 9

Lateral domain
Allow direct passage small molecules from one cell to another.
Cytoplasm connected to each other.
Formed by clusters of intercellular channels.
Allow for cell to cell communication . Spread signal through tissue.

Question 10

Basal Domain

Answer 10

Cell to matrix adhesion
-Basal lamina: Structural attachment site for overlying epithelial cells and underlying connective tissue.
Sheet of proteins: collagen 4, proteoglycans (most), laminins (have binding sites for integrins), glycoproteins.
-Focal adhesion
Integrins connect the microfilaments to the basal lamina.
-Hemidesmosomes: Provide resistance to mechanical shearing forces. Integrins connect the intermediate filaments to the basal lamina.

Question 11

Glandular tissue

Answer 11

Mode of secretion:
Merocrine
Apocrine
Holocrine

Destination of product
Endocrine
Exocrine

Question 12

Merocrine - Glandular tissue

Answer 12

Exocytosis.

Question 13

Apocrine - Glandular tissue

Answer 13

Product contained in secretory vesicles.

Question 14

Holocrine - Glandular tissue

Answer 14

Cell ruptures and releases the accumulated product.

Question 15

Endocrine - Glandular tissue (Exam)

Answer 15

Hormones secreted into the bloodstream.

Question 16

Exocrine - Glandular tissue (Exam)

Answer 16

Product secreted onto a surface, outside the body.

Question 17

Glandular tissue classification

Answer 17

Nr. of cells:
Unicellular
Multicellular 
- Simple: unbranched duct
-Compund: .branched duct

Type of secretion
Mucous: viscous and slimy
Serous: watery solution

Question 18

Epidermis (Exam)

Answer 18

Keratinized stratified squamous epithelium

Question 19

Skin functions

Answer 19

Protection
Homeostasis: temperature regulation
Sensory information
Vitamin D production
Excretion

Question 20

Epidermis structure

Answer 20

From Top layer:
-Stratum corneum: dead cells packed with keratin.
-Stratum granulosum: Most superficial layer of non-keratinized portion. Thin layer. Accumulation of granules.
-Stratum spinosum: Keratinization begins. Keratinocytes tightly connected. Langerhans cells.
Stratum Basale: Stem cells for keratinocytes. Melanocytes. Merkel’s cells. Bottom layer.

Question 21

Dermis

Answer 21

Reticular dermis: Dense irregular connective tissue providing mechanical support, strength and thickness.

Papillary dermis: loose connective tissue.

Question 22

Hypodermis

Answer 22

Loose connective tissue / adipose tissue

Question 23

Skin cells

Answer 23

-Keratinocytes: primary cell. Accumulate keratin for protection.
-Melanocytes: Produce melanin. Protect keratinocytes from UV damage.
- Langerhans cells: macrophages - phagocytosis and antigen presentation.
Merkel’s cells: Sensory information

Question 24

Glands

Answer 24

Sebaceous glands: Secretion of sebum, associated with hair follicles.

Sweat glands: Regulate body temp.
Apocrine sweat gland secretion can be used by bacteria on surface. Stinky smell. Secrete pheromones.
Eccrine sweat glands secrete onto epidermal surface.