Week 10 - Integumentary system

Question 1

List the components and functions of the integumentary system

Answer 1

Components:
Cutaneous membrane
Accessory structure

Functions:
Protection
Excretion
Maintenance of body temp
Production of melanin and keratin
Synthesis of vit D
Sensation: touch, pain, pressure, temp.

Question 2

Describe the structure of the Epidermis

Answer 2

Surface - Cells shed
Stratum Corneum - Dead flat keratinocytes lacking organelles
Stratum Lucidum - Flattened clear cells only present in thick skin.
Stratum granulosum - Keratin produced: cells start apoptosis
Stratum Spinosum - Keratinocytes shrunken and dehydrated
Stratum Basale - Basal Keratinocytes divide
Basement membrane - Epidermal growth factor (EGF) stimulates cell division, keratin production and glandular secretion.
Dermis

Question 3

Compare thick skin vs thin skin

Answer 3

T-Thick
t - thin

Location: T - Fingertips, palms, soles
t - Everywhere else

Epidermal Thickness: T - 0.6-4.5mm
t - 0.10-0.15mm

Epidermal Strata: T - Thicker strata lucidum, spinosum and corneum.
t- No strata lucidum, thinner strata spinosum and corneum

Epidermal ridges: T - present, well developed dermal papillae
t - absent, fewer and less developed dermal papillae

Hair follicles: T - Absent
t - Present

Sweat glands: T- more numerous
t - fewer
Sensory receptors: T - more numerous
t - Sparser

Question 4

How does the skin get its pigment and colouration?

Answer 4

Carotene - Yellowish
Melanin - Brown, protects from UV radiation, contributes to freckles and tan
Blood - Contributes to pink (or blue) colouration

Question 5

Describe the structure of the Dermis

Answer 5

Supports the epidermis - collagen and elastin fibres
Papillary layer - areolar tissue
Reticular layer - Fibrous network
Blood vessels - Papillary plexus, Cutaneous plexus
Sensory Receptors

Question 6

Describe structure of hypodermis

Answer 6

Layer under integument
Loose connective tissue (areolar and adipose tissue)
Connective tissue fibres interwoven with reticular layer of dermis.

Question 7

List features of the cutaneous membrane

Answer 7

Epidermis
Dermis - papillary layer, reticular layer
Hypodermis

Question 8

List the accesory structures

Answer 8

Hair shaft
Pore of sweat gland duct
Tactile corpuscle
sebaceous gland
arrector pili muscle
sweat gland duct
hair follicle
lamellated corpuscle
nerve fibers
sweat gland
Cutaneous plexus - artery, vein.
Fat

Question 9

Describe the structure of the Fasciae

Answer 9

Superficial Fascia - Between skin and underlying organs. Areolar tissue and adipose tissue. Also known as subcutaneous layer or hypodermis.
Deep fascia - Forms a strong, fibrous internal framework. Dense connective tissue. Bound to capsules, tendons and ligaments.
Subserous fascia - Between serous membranes and deep fascia. Areolar tissue.

Question 10

list the components of a hair follicle and its functions

Answer 10

Exposed shaft of hair
Sebaceous gland
Arrector pilli muscle
Hair root in connective tissue sheath
Root hair plexus
F: Protection, Insulation, Sensation.

Question 11

Describe the internal hair structure and follicle structure

Answer 11

Hair: Medulla (core) - contains a flexible soft keratin
Cortex - Thick layers of hard keratin, which provide stiffness.
Cuticle - thin but tough, contains hard keratin.

Follicle: Internal root sheath - surrounds the hair root and deeper portion of the shaft.
External root sheath
Glassy membrane - Thickened, clear layer wrapped in the dense connective tissue sheath.
Connective tissue sheath

Question 12

How does hair growth occur?

Answer 12

During growth cycle (up to 5y):
Basal cells in hair matrix divide. Daughter cells pushed towards surface at approx 0.33mm/day. Increasingly keratinised.
End of growth cycle: Follicle becomes inactive. Connections between hair matrix and root break down.
New growth cycle;
new hair produced, old hair shed.

Question 13

What is the function of a sebaceous gland?

Answer 13

To secrete sebum

Question 14

List the structure of a nail and its functions

Answer 14

free edge
lateral nail fold
Nail body: keratinised epithelial cells
Lunula
Proximal Nail fold
Eponychium(cuticle) stratum corneum
Phalanx (bone of fingertip)

Question 15

What are the differences between apocrine and merocrine sweat glands?

Answer 15

Apocrine - Secrete a thick, odorous fluid into hair follicles in axillae/pubic region.
Merocrine- discharge watery fluid onto skin surface.
Functions - Skin surface cooling, excretion, protection

Question 16

Summarise the injuries and diseases in the integumentary system

Answer 16

Skin cancer - uncontrolled cell replication. 78% are basal cell carcinomas. 2% are maligmant melanomas which are more likely to metastasise.

Burns:
First degree affect epidermis - produce reddening
Second degree involve some dermis damage - Blisters may form, some scar tissue.
third degree extend to hypodermis - sensory nerves destroyed. May disrupt fluid and electrolyte balance, thermoregulation, protection, from infection.

Question 17

What are the steps to repair injury to the integument?

Answer 17

1. Bleeding occurs, mast cells triger an inflammatory response
2. after several hours a clot (scab) with fibrin network is formed. Cells of stratum basale migrate. Phagocytic cells arrive and remove debris
3. One week after injury, Mesh is produced by fibroblasts underlying wound. Scab undermined by epidermal cells. Phagocytic activity almost ended. Fibrin clot breaking up.
4. After several weeks, epidermis is complete. Shallow depression at the injury site initially. Fibroblast activity continues. Scar tissue contains more collagen and less accessory structures.