Structure of the skin

Question 1

Describe the functions of the skin

Answer 1

Acts as a protective barrier to pathogens
Water proof: Waxy keratin layer
Sensation: For touch, feeling pressure
Metabolism: Synthesis of vitamin D3
Thermoregulation: Maintaining warmth, heat loss by sweat and vasodilation

Question 2

Describe the structure of the skin

Answer 2

Epidermis: Stratified keratinised squamous epithelium.
Dermis: A dense irregular connective tissue
Hypodermis: Adipose tissue and main blood supply

Question 3

Describe the detailed structure and the cell types of the epidermis of skin

Answer 3

Epidermis - Formed from 5 keratinocyte layers: stratum corneum, stratum lucidum, stratum granulosum (lots of keratin), stratum spinosum (lots of desmosomes) and the stratum basale.
Basale layers divide and give rise to the layers above, becoming more specialised. Intermediate cells produce keratin. Eventually lose this function and becomes squamous cells.
Within the Epidermis there are multiple cell types: Keratinocytes, melanocytes (cause skin pigmentation), langerhaus cells (DCs) and Merkel cells

Question 4

Explain the purpose and structure of skin appendages

Answer 4

Found in the dermis and hypodermis.
Hair: Hair shaft. Hair follicles produce growth. Arrector pili muscle. .
Sweat glands:
a.) Eccrine: Dermal-hypodermal junction. Ducts open onto the skin surface.
b.) Apocrine: Localised (axilla/groin) scent production.
Sebaceous glands: Mostly associated with hair follicles. Secrete a lipid mixture, sebum, into the hair follicle.

Question 5

Detailed structure of the dermis

Answer 5

Dermis: There are two types of dermis, papillary (richly vascularised, lymph and nerve) and reticulum.

• Contains hair and gland structures
• Contains the vascular supply to the skin. Maintains skin nutrition and alters flow for heat loss/conservation.

Question 6

Epidermal junction - the basement membrane

Answer 6

• Sheets of matrix between the parenchyma tissue and stromal tissue.
• Composed of: Type IV collagen, glycoproteins (e.g. fibronectin from fibroblasts) and GAGs
• Function as a barrier, adhesion and for cell organisation
• Connected to the epidermis via hemidesmosomes

Question 7

Outline some possible pathologies arising from defects in this structure: Basement membrane pathology

Answer 7

Epidermolysis Bullosa

• Rare and inherited
• Sees the separation of the epidermis from the dermis.
• Simplex (cytoskeleton),junctional (hemidesmosomes), dystrophic (collagen)

Question 8

Outline some possible pathologies arising from defects in this structure: Melanocyte pathology

Answer 8

Albinism: Lack of melanin due to lack of enzyme required for the production of melanin.
Malignant melanoma: Rapidly progressive and metastatic. Arise from nevi. Most common on intermittently exposed area.s

Question 9

Innervation of the skin

Answer 9

Sensory (afferent) nerve endings:
1.) Pacinian corpuscle: Hypodermis. Deep pressure
2.) Meissners corpuscle: Papillary dermis. Rapidly adapting mechanoreceptors.
3.) Ruffini corpuscle: Mechanoreceptors
4.) Free nerve endings: Papillary dermis. Pain, itching, temperature.
Efferent nerve endings:
- Control vessel diameter
- Communication with the sweat glands arrector pili

Question 10

Outline some possible pathologies arising from defects in this structure: SLE (Lupus)

Answer 10

Symptoms: Butterfly rash, photosensitivity.
Aetiology: Diabetes, malignancy, AIDs, adverse drug reactions

Question 11

Bacterial infections of the skin

Answer 11

Impetigo: Subcorneal blisters. Staph/strepts. Blisters. Contagious.
Cellulitis: Strept. p./staph. Dermis.
Boil: Infection of a hair follicle.
Acne: Follicle blocked with keratin plug