2. Scope of lectures
• Microanatomy of the skin (Structure)
• Derivatives of the skin
• Functions
• Terminology of skin lesions
• History/exam
• Basic medical therapy
• Common diseases
3. Skin structure
• It is the largest organ in the body with a surface area of 1.8m2 and
consists of 16% of the body weight.
• It consists of 3 main layers
1. Epidermis – stratified squamous epithelium – keratinocyte with 4
maturation levels – basale, spinosum, granulosum and corneum
2. Dermis - it’s a tough connective tissue matrix containing specialized
structures- collagen fibers 70%, elastin and glycosamides
3. Subcutaneous layer- loose connective tissue and fat
4.
5.
6.
7. Derivatives of the skin or specialized units
• Hair is found on all skin except glaborous skin i.e. palms, soles, glans
penis, and vulval introitus.
• There are 3 types of hair
• Lanugo – fine hair found in utero between 16 and 20 weeks in premature
babies
• Vellus – short, fine, light-colored hair all over the body surface
• Terminal hairs – long thick dark hairs found on the scalp, axillae, beard…
stimulated at puberty by androgens
8.
9. • Hair follicle – is a tube-like
structure that surrounds the root
and strand of the hair. Usually
found in the epidermis and
dermis.
• Function
• Help repair skin after injury
• Angiogenesis (blood vessels)
• Neurogenesis (nerves)
• Damaged hair follicles lead to
hair loss or reduced hair growth
10. Hair
Cycles
• Anagen – hair grows 1cm/month –
best seen between 2 to 7 years
• Catagen – this is a resting phase
and takes two weeks. Hair
detaches from the blood supply
• Telogen – inactive phase, hair
sheds or falls out of the hair
follicle. This takes up to 4 months
Common conditions affecting the
hair follicle
1. Alopecia areata
2. Folliculitis
3. Hidradenitis suppurativa
4. Stress
5. Telogen effluvium
11. Nails
• Nails – remnants of mammalian claw, consists of dense packed
keratin
• Nail matrix – base dividing cells – mature to keratinize and move to
the nail plate
• Nails grows - finger 0.1mm/24 hours
• Nail bed adherent to the nail plate
• Hyponychium – thick epidermis at free margin
12.
13. Sweat glands
• Tube like coiled structures within the dermis and produce watery
secretions
• Eccrine sweat glands – universally found all over the skin, profuse on
palms, soles, axillae, forehead. They are under thermal and
psychological control. Innervated by sympathetic cholinergic fibers.
• Apocrine sweat glands – remnant of mammalian sexual scent gland,
open into hair follicles, larger than eccrine glands. Populous in axillae
perineum, areolae. Controlled by sympathetic adrenergic nerves
14. Nerve supply
• Hand, face and genitalia have the highest supply
• All skin nerves have their cell body in the dorsal root ganglia. Both
myelinated and demyelinated. They contain substance p
(neuropeptide)
• Free nerve endings abut merkel cells which detect pain, itch and
temperature
• Corpuscular receptors – Pacinian corpuscles – detect touch and
vibration
• Meissners corpuscles are found in the palms and soles
15. Others
• Blood vessels and lymphatics
• Cutaneous vasculature is complex and is limited to the dermis while the
epidermis has no blood vessels
• Blood vessels provide nutrients and oxygen to the skin and play a major role
in temperature regulation
• Lymphatics transport particulate and liquid materials from the extravascular
compartment of the dermis
• Sebaceous glands are associated with hair and are androgen sensitive
16. Functions of the skin
1. barrier to physical agents
2. protects from mechanical injury
3. prevents loss of body fluids proteins and minerals
4. Protects from UV radiation – melanocytes
5. Regulates body temp
6. Sensory nerve organ
7. Affords surface for grip
8. Vit D production
9. Outpost immune surveillance
10. Cosmetic association
17. Terminologies of skin lesions
• a lesion is a general term for an area of disease usually small
• an eruption or rash is more widespread skin involvement.
they are either primary pathology or due to secondary factors scratch or infection. Lesions
• primary
macules, papules, plaque, nodule, papilloma, vesicle, bulla, pustules, wheal, telangiectasia, petechiae,
purpura, ecchymosis, haematoma, poikiloderma, erythema, burrow, comedo
• secondary lesions
scale, crust, excoriation, lichenification, fissure, erosion, ulcer, sinus, scar, keloid scar, atrophy, striae
