6T: Integumentary System

Question 1

6 cell types in the epidermis

Answer 1

1. Keratinocytes: epidermal skin cells
2. Merkel cells: tactile receptors. derived from the neural crest cells. in fingers and hands
3. Langerhans cells: macrophages/APCs
4. Ruffini: senses stretch
5. Meissner Corpuscle: Tactile receptor. dermal papillae. in fingertips, hand, foot, front of forearm, lips, and tongue
6. Melanocytes: have melanin in them. first cell to arrive in the epidermis
   note: not all cells that have melanin are melanocytes, but all melanocytes have melanin

Question 2

3 layers of the dermis

Answer 2

1. papillary dermis (loosely packed connective tissue)
2. reticular dermis (densely packed connective tissue)
3. hypodermis (subcutaneous fat)

Question 3

5 layers of epidermis

Answer 3

1. stratum corneum: part of the assembled cell envelope
2. stratum lucidum: part of the assembled cell envelope
3. stratum granulosum: major product is filaggrin
4. stratum spinosum: contains keratins 1 and 10
5. stratum basale: contains keratins 5 and 14

Question 4

Psoriasis

Answer 4

cause: infiltrating immune cells synthesize and release cytokines that signal keratinocytes to increase cell proliferation, and thus reduce the length of the cell cycle. The extra skin cells cause the epidermis to thicken and the dead cells pile up to create a white, flaky layer.
- normally cells in the stratum corneum don’t have nuclei, but in psoriasis sometimes they do

Question 5

How does our skin keep water in/out?

Answer 5

Filaggrin is secreted in the stratum granulosum. Filaggrin is a non-intermediate filament that aggregates with keratins. This aggregate makes a “sandwich” with 3 proteins in the middle, and a lipid layer on top. Transglutaminase K (TGK) is the enzyme that crosslinks these three proteins

Question 6

Diseases related to the transglutaminase family

Answer 6

Lamellar Ichthyosis: fish scaley looking skin

Dermatitis herpetiformis: deposition of IgA

Question 7

What are the spinelike structures of the keratinocytes?

Answer 7

desmosomes

Question 8

2 Types of Pemphigus

Answer 8

Pemphigus Vulgaris
- autoantibodies to desmoglein 3
- mucous membrane dominant: antibody to DSG3
- mucocutaneous: antibody to DSG3 and DSG1
Pemphigus Foliaceus
- autoantibodies to desmoglein 1

Question 9

Contents of the hair follicle

Answer 9

• external root sheath: continuous with the stratum basale of the epidermis
• internal root sheath: surrounds the hair shaft
• dermal papillae: are a reservoir of stem cells
• sebaceous gland
• cells of the outer root sheath “bulge” are stem cells capable of regenerating the hair follicle

Question 10

3 stages of hair growth

Answer 10

1. Anagen: growth phase
2. Catagen: intermediate/regression
3. Telogen: rest/shedding

Question 11

Type of secretion of the sebaceous gland

Answer 11

holocrine

Question 12

Two general types of sweat glands

Answer 12

1. Eccrine (merocrine): long tubular extension which coil into a ball-shaped mass
2. Apocrine: in the axilla, perianal and pubic areas, scrotum, labia majora, and around the nipples

Question 13

Sensory receptor cells

Answer 13

Tactile:
- Meissner's Corpuscle (dermis)
- Merkel Cell (epidermis)
Stretch:
- Ruffini (dermis)
Pressure: 
- Pacinian Corpuscle (hypodermis)
    * detects deep pressure and vibration
Pain and Temperature: 
- Free nerve endings

Question 14

Define:

a. first intention healing

b. second intention healing

Answer 14

a. smaller, almost stab wound. Tissue on the surface is close to each other (or has been brought close by stitches etc.)
b. extensive damage. edges can’t be brought together. ex: bed sores
- fibroblasts —-> myofibroblasts

Question 15

Dupuytren’s contracture

Answer 15

thickening of the palmar aponeurosis leading to the progressive flexion contraction of the fourth and fifth digits of the hand

Question 16

Skin Grafting

Answer 16

where a patch of skin is surgically removed from one part of the body and is transplanted to another.

• can come from the same person or a different person
• color and texture are chosen to match the new site, because the skin will keep the texture of where it came from.