Skin and its diseases Flashcards
what is the function of the skin
- Self-repairing barrier
- Skin permits terrestrial life by preventing the ingress of microorganisms and chemicals whilst regulating heat and water loss from the body – 500ml off water loss
What is the integumentary system:
Your integumentary system is your body’s outer layer. It’s made up of your skin, nails, hair and the glands and nerves on your skin. Your integumentary system acts as a physical barrier — protecting your body from bacteria, infection, injury and sunlight.
what is the function of Integumentary system
- Thermal insulation
- Cutaneous sensation
- Metabolic functions
- Blood reservoir
what are the layers of the skin
- Subcutaneous
- Dermis
- Epidermis (outer layer)
where is stratum corenum thickened on?
Stratum corenum – thickened on load-bearing areas of the body and thinner on the other areas
What is the process of the skin being replaced?
At the innermost layer of the epidermis- Basal cells divide and they migrate outwards, flatten, and form the stratum corneum (SC).
Takes 14 days to form basale to SC, then another 14 days through SC, skin replaces every 28 days.
Cell types within the epidermis:
what are their functions
Keratinocytes: produce keratin, fibrous protein that helps give epidermis its protective properties. Arise in deepest part of epidermis from cells in stratum basale (basal layer) that undergo continuous division. Cells are pushed upward as new cells form in layers beneath. By time cells reach free surface of skin, they are dead, keratin filled scale-like structures.
In body areas where get regular friction (e.g. hands and feet) cell turnover and keratin production is increased.
Melanocytes: synthesise the pigment, melanin. Found in deepest layer of epidermis. Melanin taken up by surrounding keratinocytes to form pigment shield that protects nucleus from damaging effects of UV radiation.
Merkel cells: low abundance cells linked with disc-like sensory nerve endings (combination called a Merkel disc). Functions as a sensory receptor for touch.
Langerhan’s cells: Dendritic cells that arise from bone marrow and migrate to epidermis. Process microbial antigens to become antigen-presenting cells
what is the Structure of the skin dermis
- Makes up bulk of skin. Comprised of fibrous connective tissue (corresponds to animal hides used to make leather products).
- Richly supplied with nerve fibres, blood vessels and lymphatic vessels.
- Two layers: papillary layer (thin superficial) and reticular layer.
Papillary layer forms dermal papillae to produce structures like nipples and ridges e.g. finger prints.
Reticular layer is deepest layer accounting for ~80% of thickness of dermis. Comprised of dense irregular connective tissue. Collagen fibres in dermis provide strength and resiliency.
what is the two layers of the dermis and what are their features
- Two layers: papillary layer (thin superficial) and reticular layer.
Papillary layer forms dermal papillae to produce structures like nipples and ridges e.g. finger prints.
Reticular layer is deepest layer accounting for ~80% of thickness of dermis. Comprised of dense irregular connective tissue. Collagen fibres in dermis provide strength and resiliency.
what are the appendages in the skin
Appendages in skin
-* sweat glands
* sebaceous (oil) glands
* nails
* hair follicles
* hair
Sweat (Sudoriferous) Glands –
Have >2.5 million per person.
Two types: eccrine and apocrine.
Eccrine sweat glands:
Simple, coiled, tubular gland.
Ducts empty into pores that lead to surface of skin.
Regulated by sympathetic autonomic nervous system.
Prevents over heating of body.
Apocrine sweat glands: larger than eccrine glands and ducts.
Empty into hair follicles.
In humans, apocrine sweat glands are found only in certain locations of the body:
the axillae (armpits), areola and nipples of the breast, ear canal, eyelids, wings of the nostril, perianal region, and some parts of the external genitalia
Secretions contain sweat plus fatty substances and proteins.
Odourless but when mixes with bacteria on skin (that decompose organic molecules in secretion) get body odour.
Modified apocrine glands include the ciliary glands in the eyelids; the ceruminous glands, which produce ear wax; and the mammary glands, which produce milk.
Sebaceous (Oil) Glands – found all over the body except on palms of hands and soles of feet. Secrete sebum that softens and lubricates hair and skin and has bactericidal activity. Sebum secretion is under hormonal control (androgens). (site for acne)
what is the difference between apocrine and eccrine sweat glands
Eccrine sweat glands:
Simple, coiled, tubular gland.
Ducts empty into pores that lead to surface of skin.
Regulated by sympathetic autonomic nervous system.
Prevents over heating of body.
apocrine:
larger than eccrine glands and ducts. Empty into hair follicles.
only found in certain parts
what is sebaceous glands
Sebaceous (Oil) Glands – found all over the body except on palms of hands and soles of feet. Secrete sebum that softens and lubricates hair and skin and has bactericidal activity. Sebum secretion is under hormonal control (androgens).
what are nails and their functions
Tough keratinised layer, with lower lipid levels than stratum corneum
Finger nails grow from nail bed @ ~ 3 mm / month, toenails ~1 mm / month
V. difficult to deliver drugs through intact nail plate to treat diseases on nail bed
E.g. onychomycosis (fungal infection)
Easier if nail damaged
e.g. psoriasis
