These notes have a neat layout which is colourful, easy to read and understand. Diagrams are included. These notes where made using the lecture slides and it is all the work that was needed for tests/exam.
The Skin
A) Skin structure
- Largest organ
- Surface area = 1.6 – 1.9m2
- Thickness 1-2mm
o Thinnest: eyelids (0.5 – 1mm)
o Thickest: sole + palm (1.5mm)
- Mass = 4kg
- 2 major regions → epidermis + dermis
a. Epidermis
i. Superficial layer → continuously rubbed off & replaced from deeper layers
ii. Stratified squamous epithelium
iii. NO blood vessels
iv. NO lymphatic ducts
v. 5 layers & 4 distinct cell types
1. Layers
a. Stratum corneum
b. Stratum lucidum → in thicker parts of skin
c. Stratum granulosum → where keratin is produced
d. Stratum spinosum → strength + flexibility
e. Stratum germinativum → where keratinocytes + melanocytes are produced
2. Cells of epidermis
a. Keratinocytes
i. Most abundant (95%)
ii. Produce firbrous protein keratin
iii. Protection & waterproof
b. Melanocytes
i. Produce brown pigments → melanin
ii. Responsible for skin colour
iii. Provides protection against UV radiation
iv. Pigmentation
1. Freckles → accumulation of melanin
2. Vitiligo → patched of depigmented skin, contains no/few melanocytes that
CANNOT produce melanin
3. Albinism → depigmented skin, melanocytes present but NO melanin produced
due to absent tyrosine enzyme → can’t convert Tyr → melanin
c. Langerhan’s cells
i. Epidermal macrophages
ii. Immunity system → clears area of debris + pathogens
d. Merkel cells
i. Sensory cells → touch sensation
ii. Makes contact with nerve endings in dermis
, b. Dermis
i. Made of connective tissue
1. Fibroblasts, macrophages, mast cells, WBC
ii. Contains:
1. Blood vessels, lymph vessels, nerve endings
2. Collagen fibers (firmness)
3. Elastic fibers (elasticity)
4. Sebaceous glands
5. Sweat glands
6. Hair
iii. 2 layers: Papillary & reticular layer
iv. Sweat glands
1. Eccrine glands
a. In palms, soles of feet, forehead
b. Secrete sweat (water + salt)
c. Ducts open onto skin surface
2. Apocrine glands
a. Found in genitalia, anus and axillae
b. Secrete a waxy or viscous secretion in
response to fear or sexual excitement
c. Ducts open into hair follicle
d. Modified apocrine glands
i. Ceruminous glands
1. in external ear canal → produce ear wax
ii. Mammary glands
1. in the breast → produce milk
iii. Ciliary glands
1. on margins of the eyelids → produce lipid
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