Integumentary System

Question 1

Layers of skin

Answer 1

1. epidermis: outermost, thinnest layer of epithelial cells

2. dermis: deeper, thicker, made of dense connective tissue, vascularised

Question 2

Development of the integumentary layer

Answer 2

Epidermis from ectoderm

dermis & hypodermis (superficial fascia) from mesoderm

Question 3

Epidermis

Answer 3

1. Stratum basale = deepest
2. Stratum spinosum = prickly
3. Stratum granulosum = granular (1-5 layers of flattened cells), when organelles start deteriorating
4. Stratum lucidum = clear
5. Stratum corneum = horny (20-30 layers of ead cells)

Question 4

Skin Pigmentation

Answer 4

melanocytes in basal layer produce melanin which is transferred to overlying keranocytes

no. of melanocytes = same in everyone, but the amount of melanin they produce is different

Question 5

Variations in epidermal thickness

Answer 5

Thin Skin = hairy (absent stratum lucidum, and all other strata are thinner)

Thick skin = no hair

• covers areas subject to abrasions
• thicker stratum corneum due to increased mechanical stress

Question 6

Dermis

Answer 6

composed of:

• dense, irregular connective tissue (collagen and elastic fibres)
• has high tensile stregnth and can stretch and recoil
• supply of vasculature and nerve fibres

1. Papillary layer
   - 1/5 of thickness
   - contains capillaries and sensory receptors
   - forms dermal ridges in regions fo thick skin (makes finger prints)
2. Reticular
   - deepest layer that is attached to subcutaneous tissue/hypodermis
   - collagen fibres run in specific planes –> tension lines
   - contains blood vessels, nerves, hair follicles, sebaceous and sweat glands

Question 7

Blood supply

Answer 7

vessels = from mesoderm
- transmitted to skin via subcut. tissue

epidermis receives nutrients via DIFFUSION through ISF (has no vessels)

Question 8

Cleavage/Tension Lines in reticular dermis

Answer 8

formed by separations/less dense regions of collagen fibre bundles due to natural tension

Longitudinal in head and limbs
circular in neck and trunk

Incisions should be made PARALLEL to tension lines to

• gape less
• reduce scarring
• heal faster

Question 9

Subcutaneous Tissue/hypodermis

Answer 9

loose, connective tissue that has variable amounts of adipose tissue

Septa (fibrous strands) bind sucut. tissue –> underlying dense con. tissue

• has muscles in face, neck, palm, scrotum

Question 10

Cutaneous Nerves and Sensory Receptors

Answer 10

only in dermis

1. Tactile disk receptor: detects fine touch, pressure, vibration, itch and tickle (most superficial)
2. Ruffini Corpuscule: crude touch, stretch of skin (middle)
3. Hair Root Plexus: wrapped around root –> crude touch
4. Lamellated Corpuscle: senses pressure and fast vibration

Question 11

Dermatomes

Answer 11

area of skin supplied by one spinal cord segment

Question 12

Burns

Answer 12

1st deg: injures only epidermis

2nd: both epidermis and first layer of dermis
3. full thickness of skin

Question 13

Stretch Marks

Answer 13

dermis = collagenous and highly vascular, therefore when skin is overstretched, lateral bonding b/w collagen is disrupted and small blood vessels rupture = red marks which turn silver when scar tissue appears