Lecture 1 & 2 Flashcards
- Describe the layers of the skin - Describe the functions of the skin - Describe accessory structures of the skin and their function - Understand how skin anatomy relates to skin aging, pigmentation, tattoo and melanoma
Skin (surface area)
Largest and most visible organ of the body, 16% of body weight, 1.5-2 m2 of surface area, bare makes us unique.
Functions of skin + accessory structures.
- Detect touch, pain, pressure, temp stimuli and relay information to nervous system.
- Excrete salts, water, organic waste by integumentary glands
- Maintain normal core body temperature through insulation or evaporative cooling.
- Protect underlying tissue or organs from impact, abrasions, fluid loss, and chemical attack
- Produce melanin to protect underlying tissue from UV radiation
- Produce Keratin to protect against abrasions and serve as a water repellent.
- Synthesise Vitamin D3 (steroid converts to Calcitriol-hormone) important for normal calcium metabolism (homeostasis).
- Store Lipids in Adipocytes (in Dermis) and Adipose tissue (in Subcutaneous layer).
3 Primary Layers in Skin are
Epidermis, Dermis, Hypodermis
Epidermis (what layer inside, outside, middle)
3 things
outside layer, stratified barrier (made of different layers), mostly keratinocytes (cells with high amount of keratin-protein eg nails & hair, provides skin strength), Avascular (no blood vessels no circulation).
Dermis (what layer inside, outside, middle)
4 things
Directly under epidermis and above hypodermis. Protein fibres for strength, provides structure, Vascular (blood supply) to nourish epidermis layers that are still alive.
Hypodermis
1 thing
Adipose tissue for insulation
Cutaneous layer
Epidermis and Dermis
Subcutaneous layer
Hypodermis
Epidermis layers are
Stratum Corneum, Stratum Lucidum (only in thick skin), Stratum granulosum, Stratum Spinosum, Stratum Basale.
Stratum Corneum
Type of cells
outside, horny layer, made of dead dried flat cells (no nuclei), can be completely removed
Stratum Lucidum
Type of cells
(only in thick skin) - clear layer, palms hands, soles feet
Stratum granulosum
Type of cells
Granular layer, granules within that dries out cell, provides crosslinking of keratin fibres, secretion of waxy material into intercellular spaces to waterproof cells
Stratum Spinosum
Type of cells
spiny layer, desmosomes (intercellular bridges) link cells together, begins process of cells flattening as they move upwards
Stratum Basale
Type of cells
Base, basal layer, Columnar (tall) regenerative cells which migrates upwards to replenish layer above
Epithelial cell types are
Squamous (scales), Cuboidal, Columnar
Epidermis epithelial cell type is
stratified (layered) squamous epithelium.
Dermis does Not
shed, Protein (collagen and elastic) fibres (cross links) provide strength, Vascular (nourishes epidermis), connective tissue.
why do people have Saggy skin
As you age you lose strength as the protein fibres are not that rigid.
Hypodermis contains
adipose tissue (made of adipocytes), Insulation, Subcutaneous.
Hair (incl location, consists of,)
All over body
Hair shaft, hair follicle, arrector pili muscle, sebaceous gland
Where is the sebaceous gland and what does it produce
on skin where there is hair
Produces sebum a Natural moisturiser/water repellent
Lanolin = sheep sebum (skincare)
Acne cause
Blockage of hair follicles + infection
Sweat glands
Eccrine (everywhere, thermoregulation)
Apocrine (specialised)
Nails function
Protect fingertips, enhance sensation
Accessory structures Receptors
Tactile
lamellar
Bulbous
Skin accesories
Hair, Acne, sweat glands, nails, receptors
Melanin pigment (What it does, Produced, Transported by)
absorb UV light and protects cells from UV damage
Made in melanocytes
Transferred by melanosomes
Melanosomes (incl what it can do)
*
Vesicles containing melanin
able to proliferate (move along basement membrane)
shed with keratinocytes
Melanocytes location why it’s found there
deep within epidermis to be protected from UV light as UV damages DNA and can cause cancer
Highly pigmented areas
Mole and Freckle
Mole
deep cluster of melanocytes within stratum basali. Overproliferation caused by sun exposure.
Freckle
melanocytes overproducing melanosomes.
Overproduction Caused by sun exposure
Melanocytes location
stratum basale only (mainly at the base). Not shed.
Melanosomes location
throughout the epidermis
Melanocytes density varies
through body not race
why is human skin pigmentation so variable?
Different rates of production of melanosomes, keratins, sun exposure, vascularisation
Skin pigmentation matches
UV exposure (in indigenous populations)
Pigmentations correlate with UV exposure. describe pigmentation, skin colour, and UV exposure at each location
At equador
Northern latitudes
Southern latitudes
- high p, darker skin, high UV
- low p, fairer skin, low UV exposure
- high p, darker skin, high UV
Why is skin pigmentation important?
protection against UV by degrading chemicals (folate) which is important for evolution of pigmentation.
Vitamin D essential for (incl effects when deficient)
normal calcium metabolism and strong bones
deficiency affects mood, cause rickets
what is required for vitamin D synthesis?
UV exposure in skin
2 types of skin cancer
Basal cell Carcinoma, Malignant melanoma
Basal cell carcinoma
common
benign
Stratum basale
Metastasis rare
Malignant melanoma
Rare Deadly Melanocytes (pigmented) Highly metastatic Mortality rate depends on tumour size
Metastasis
Tumour transplants into another site
Tattoo
Artificial pigmentation deposited deep in skin Dermal layer (not shed) Captured (not broken down) inside immune cells (forms scar tissue to preserve tattoo)
lena tattoo pigmentation of lymph nodes
broken down - faded
body has limited capacity to deal with pigmentation moves through lymphatic system to lymphnodes.
Tattoo types
Trauma, decorative
cosmetic (eg brows)
Polynesian - Ta moko (maori), Pe’a (samoan)
Skin age
thin epidermis and dermis (saggy-wrinkly - lose protein connective tissue lose rigidity)
slower skin repair
drier epidermis (sebaceous gland make less sebum)
Impaired cooling (less sweat)
Less pigmentation (pale skin, grey hair)
