The Skin

Question 1

What are Merocrine sweat glands associated with?

Answer 1

Thermoregulation

- Directly secrete substances onto the surface of the skin

Question 2

What are the 5 roles of the skin?

Answer 2

Protection - impact, chemical and infection

Temperature maintenance - Regulate heat gain/loss

Synthesis and storage of nutrients - Vit D3

Sensory reception

Excretion and secretion - salt, water, milk

Question 3

What is the structure and function reticular layer of the dermis?

Answer 3

Irregular, dense, connective tissue
Rich in collagen
Shock absorber - protects internal organs

Question 4

What is the process of thermoregulation?

Answer 4

• Increase in CORE temperature
• Thermostat in the hypothalamus - activate the cooling mechanism
• Vasodilation - heat radiated from skin surface
• Sweat glands activated

When decrease- opposite and the skeletal muscles are activated - shiver to produce heat

Question 5

What is the active version of vit D3?

Answer 5

Calcitriol

Question 6

What are the two types of epithelium and how are they different?

Answer 6

Thick
- Has 5 layers
- On the palms of the hands, fingertips (where no hair)
Thin - has 4 layers (doesn’t have the stratum lucidum)

Question 7

What is the layer of the dermis which is close to the epidermis and what is its structure/function?

Answer 7

The Papillary layer
Connective tissue
Interdigtated with the epidermis to maintain its attachment to the dermis

Question 8

What are the 3 cell types in the stratum basale?

Describe them

Answer 8

1) Keratinocytes (skin cells)
- Mitotically active
- The majority

2) Melanocytes (give color to the skin)
- Have two types of melanin:
- Eumelanin
- Phenomelanin

3) Tactile cells (Merkel cells)
- Connected to sensory nerves
- Participate in TOUCH

Question 9

How do keratinocytes behave in the skin?

Answer 9

• They are ‘born’ in the stratum basale, where they are mitotically active
• They divide asymmetrically and become detached from the basement membrane
• As they differentiate, they migrate upwards throughout the skin, becomming less mitotically active and more flattened as they do so
• As they move upwards they produce higher amounts of keratin
• They are fully differentiated in the stratum granulosum (post mitotic)

Question 10

What are the functions of the hypodermis in babies compared to in adults?

Answer 10

Provide protective layer in babies

In adults it is restricted to specific body areas and protects against heat loss

Question 11

What does calcitriol do?

Answer 11

Activates gene that code for a gene essential for re-absorption of Ca2+

• By binding to the VDR
• VDR acts as a transcription factor
• Controls gene expression

Question 12

What are 4 cutaneous gland and what do they do?

Answer 12

• Mammary gland (produce milk)
• Ceriminous gland (produce earwax)
• Sebaceous gland (produce sebum which lubricates skin and hair, protecting against infection)
• Sweat glands

Question 13

Which layer of the epidermis has 15-30 layers of dead keratinized cells?

Answer 13

The stratum corneum

Question 14

What are Apocrine sweat glands associated with?

Answer 14

Hair cells

• Armpits, forehead, beard
• Secrete products into the hair follicles

Question 15

What is the function of keratin?

Answer 15

Forms durable filaments

Question 16

How does the skin act as a biochemical barrier?

Answer 16

Sebum produced by sebaceous glands
- Contains bactericidal substances

Sweat lowers the pH to 4-6 (unfavorable for bacterial growth)

Question 17

Which layer of the epithelium is the last layer to have cells that contain nuclei?

Answer 17

The stratum granulosum

Question 18

Which layer of the epidermis has 3-5 layers of keratinocytes?

Answer 18

The stratum granulosum

Question 19

What structures are contained within the dermis?

Answer 19

Blood vessels
Nerve cells
Accesssory structures - hair, nails, sweat glands, sebaceous glands

Question 20

What is the hypodermis?

Answer 20

Subcutaneous layer (under the skin)
Connective tissue
Contains adipocytes (fat cells)

Question 21

Which layer has keratinocytes which make large amounts of keratin and glycolipids?

Answer 21

The stratum granulosum

Question 22

How does the skin act as a physical barrier?

Answer 22

Keratin provides toughness, prevents the entry of infectious agents

Question 23

Which is the thickest layer of the epidermis?

Answer 23

The stratum spinosum

Question 24

How does the skin act as an immunological barrier?

Answer 24

Dendritic cells in stratum spinosum

Question 25

What does the stratum spinosum contain?

Answer 25

Keratinocytes which have become detached from the basemement membrane and are more flattenes but are still mitotically active. Higher keratin content

Dendritic cells (Langerhans)

Question 26

What are the 5 layers of the skin? (bottom to top)

Answer 26

5) Stratum Basale
4) Stratum Spinosum
3) Stratum Granulosum
2) Stratum Lucidum
1) Stratum Corneum

Question 27

Where is vitamin D3 produced in the skin?

Answer 27

Stratum basale and stratum spinosum

Question 28

What is the structure of the dermis?

Answer 28

Thicker than the epidermis
Irregular structure (no layers)
Connective tissues

Question 29

What is the life cycle of keratinocytes?

Answer 29

2-4 weeks

Question 30

Process of Vitamin D3 production?

Answer 30

1) 7-dehydrocholesterol
2) Pro-vitamin D3
3) Vitamin D3 (cholecalciferol)
4) CalciDIOL
5) CalciTRIOL (active version of vit D3)

Step 1 - 2: Requires UVb exposure
Step 2 - 3: isomerisation
Step 3 - 4 - 5: Hydroxylation

Question 31

What is the function of glycolipids?

Answer 31

Spreads over the keratinocytes
Makes skin water-resistant
Also creates lipid bilayer which separates the upper and lower layers of the skin

Question 32

What is the skin described as?

Answer 32

A self-regenerating, stratisfied squamous, keritinized epithelium