The skin

Question 1

What does the integumentary system include?

Answer 1

The skin and its associated structures; nails, hair and glands

Question 2

To carry out its role, what qualities does the skin need?

Answer 2

Tough, pliable, stretchable, waterproof, and self-repairing

Question 3

What are the functions of the skin?

Answer 3

• Protection
• Temperature regulation
• Sensation
• Metabolism
• Waste disposal

Question 4

How does the skin protect?

Answer 4

• Physical barrier - contains keratin making it waterproof
• Chemical barrier - skin releases natural anti-bacteria to prevent bacterial growth on the skin
• Biological barrier - immune cells in the skin recognise foreign bodies and activate immune system

Question 5

How does the skin regulate body temperature?

Answer 5

If too hot - blood flow to the skin increases, heat is lost by radiation, sweat produced and body is cooled by evaporation
If too hot - blood flow to skin decreases, heat retained, sweat glands inn-activated and muscles shiver to generate heat

Question 6

How does the skin act as a blood reservoir?

Answer 6

Can hold 5% of blood volume - during exercise blood distributed to muscles.

Question 7

How does the skin contribute to sensation?

Answer 7

Skin surface has many sensory receptors that respond to various stimulus e.g. temperature and pressure

Question 8

How does the skin act as a metabolic function?

Answer 8

Sunlight acts on skin cells converting them to vitamin d cells.

Question 9

How does the skin contribute to excretion?

Answer 9

Nitrogen containing wastes can be removed from the skin: urea, ammonia and uric acid (in small amounts)
Water and salt also leaves through the skin

Question 10

What are the three layers of the skin?

Answer 10

• Epidermis (outside in contact with atmosphere)
• Dermis (middle layer)
• Subcutaneous layer/hypodermis (inside layer) anchors skin to internal organs

Question 11

What are the five layers of the epidermis?

Answer 11

Outside > in
- Stratum corneum
- Stratum lucidum
- Stratum granulosum
- Stratum spinosum
- Stratum basale

Question 12

What are the four cell types in the epidermis?

Answer 12

• Keratinocytes
• Melanocytes
• Langerhans cells
• Merkel cells

Question 13

Summarise keratinocytes

Answer 13

• Main cells
• Formed by mitosis in basal layers
• Connected tightly to eachother by desmosomes
• As they migrate to surface produce more and more keratin - tough protein which gives skin protection and waterproofing
• When cells reach surface they are dead and flat
• Rubbed of skin everyday

Question 14

Summarise melanocytes

Answer 14

• 10-20% of basal layer
• Produce melanin pigment (dark brown/yellow)
• The melanocyte process is the spreading of melanin to skins surface, the more melanin the darker the skins complexion

Question 15

Summarise langerhans cells

Answer 15

• Bone marrow derived cells
• Type of macrophages - protect from bacterial and viral infections

Question 16

Summarise merkel cells

Answer 16

• Few in numbers
• Found at dermal epidermal surface
• Each cell associated with a nerve ending
• The combination of nerve and cell forms the light touch receptor called a merkel disk

Question 17

Describe the stratum basale

Answer 17

• Single cell layer, deepest epidermal layer, sitting on basement membrane
• Highest level of mitotic division
• Produce keratocytes
• Have melanocytes and occasional merkel cells

Question 18

Describe the stratum spinosum

Answer 18

• Several layers thick
• Fill with intermediate filaments (in form of pre-keratin)
• ‘spine appearnce’

Question 19

Describe the stratum granulosum

Answer 19

• 3-5 layers
• Keratinocytes are flatter

Question 20

Describe the stratum lucidum

Answer 20

• Only in thick skin
• Translucent band
• Dead keratinocytes as they are too far from blood supply

Question 21

Describe stratum corneum

Answer 21

• Outermost layer
• 20-30 cells thick
• Cells are flattened, full of keratin and have thickened plasma membranes
• Contains glycolipid layer making skin waterproof

Question 22

Describe the dermis layer

Answer 22

• Comprised of connective tissue therefore;
  cells
  fibres
  matrix
  Also has sweat glands (sudiferous) and sebaceous (oil) glands
• blood vessels and nerves present

Question 23

Describe eccrine glands

Answer 23

• Each is a simple, coiled, tubular gland
• Abundant on palms, soles of feat and forehead

Question 24

Describe apocrine sweat glands

Answer 24

• Present in axillary and anogenital areas
• Ducts empty contents into hair follicles
• Do not begin secreting until puberty

Question 25

Name two other specialised skin glands

Answer 25

- Ceruminous galnds Inside the ear, prevent insects from entering - Mammary glands Sweat glands in the breasts which secrete milk

Question 26

Summarise sweating

Answer 26

- Prevents overheating - Regulated by sympathetic nervous system (fight or flight system) - Heat induced sweating starts at the forehead and spreads inferiorly - Emotional sweating 'cold sweat' caused by fright, embarrassment or nervousness and begins on palms, soles and axillae (armpits) then spreads over the body

Question 27

Summarise sebaceous (oil) glands

Answer 27

- Everywhere except palms and soles - Secrete sebum - antibacterial - into hair folicul or skin surface - lubricates hair and skin - slows water loss and prevents hair becoming brittle - Regulated by hormones - become active during puberty (cause spots)

Question 28

Summarise the nails

Answer 28

- Hard keratin - Changes in shape can indicate health conditions

Question 29

Summarise skin colour

Answer 29

- Melanin - brown ish - contributes to tan - Carotene - orange/yellow palms and soles - haemoglobin - red