SKIN Flashcards
What are the 6 functions of the skin
- Protection against fluid loss, abrasion, and chemical attack
- Excretion of salt
- Temperature control
- Melanin protection
- Vitamin D3 synthesis which is converted to calcitriol for Ca metabolism.
- Lipid storage
What are the three key layers of the skin
- Epidermis
- Dermis
- Hypodermis
Types of epithelial tissue
- Simple epithelia – singular layer
- Stratified epithelia – Multiple layers
- Squamous
- Cuboidal
- Columnar
What makes up the epidermis. Function?
- Mostly made of stratified squamous epithelial tissue.
- Function: Protection from abrasion
- Primarily made from keratinocytes but also contains other cell types.
- Has no circulation/blood vessels.
What are the 5 layers of the epidermis?
- Stratum corneum
- Stratum lucidum
- Stratum granulosum
- Stratum spinosum
- Stratum Basale
What makes up the dermis
- Made of dense irregular connective tissue
- Papillary layer and reticular layer.
- Contains protein fibres for strength.
- Contains blood vessels, nerves, and lymphatics.
- Also contains accessory structures like hair follicle.
What makes up the hypodermis
- Made of loose connective tissue
- Constant thickness
- Functions: connects the skin to the rest of the body, provides cushioning, energy storage.
- Contains large blood vessels.
What does hair consist of? How does acne occur?
- Consists of the hair shaft, follicle, arrector pili muscle, and sebaceous gland.
- Acne occurs when there is a blockage of hair follicles and subsequent infection.
What are the two types of sweat glands? And what do they do?
- Eccrine glands – main types present everywhere which secrete a watery, electrolyte rich substance for thermoregulation.
- Apocrine glands – Specialized glands present in the axillae, groin, and nipples. Secrete a viscous solution into the hair follicles which open on the skin surface.
What its a mole?
Cluster of melanocytes which can be caused by sun exposure
What is melanin?
pigment produced in melanocytes which absorbs UV light to prevent cell DNA damage.
- Melanin is transferred to epidermal cell via melanosomes (vesicles containing melanin).
- Melanocytes are located in the stratum Basale while melanosomes are throughout the epidermis.
Vitamin D deficiency. Who is effected more? What are the effects?
- Highly pigmented people are more susceptible to vitamin D deficiency due to their decrease in UV exposure.
- Vitamin D synthesis occurs with UV exposure. Vitamin D is converted to calcitriol which plays an important role in Ca metabolism and bone strengthening.
- Low vitamin D can cause rickets (soft bones).
What are tattoos?
- Permanent, artificial pigmentation usually deposited deep within the dermal skin layer an captured within immune cells
What is skin aging? And what effect does it have?
- Thinning and drier epidermis
- Thin dermis - wrinkling
- Slower skin repair.
- Impaired cooling (less sweat production).
- Less pigmentation.
- Smoking and sun exposure speeds up skin aging.
What are the 5 types of skin receptors?
- Free nerve endings
- Tactile Discs
- Tactile corpuscles
- Lamellar corpuscles
- Bulbous corpuscles
What are free nerve endings? What is their function? their Structure, and location.
Location; epidermis
- Most common type of skin receptors
Structure: Consists mostly of small diameter unmyelinated C group fibres (slow signals carrying dull pain) and small diameter group A delta myelinated fibres (fast signals carrying sharp pain).
Sensory terminals are swellings at the distal nerve ending that receive the sensation.
Function: Receptors such as TRPV1 (cation channel) are on the terminal which cause depolarization of the nerve ending and action potential firing, and interpretation of stimulus at the somatosensory cortex).
Tactile discs. Location, Structure, and what are they stimulated by?
Location: Deepest layer of the epidermis
- Abundant in the fingertips and have small receptive fields (good two-point discrimination).
Structure: Consists of a large disc shaped epidermal cell and a free nerve ending made of myelinated, medium diameter group A-beta cells.
Communication between the Merkel discs and tactile disc is serotonergic (neurotransmitter releases serotonin).
Stimulated by: Texture, shape and edges, fine touch and light pressure.
- Sensitive to the physical features of objects.
Tactile corpuscles?
Location: Dermal papillae
- Dense in areas of skin without hair
Structure: Branched/spiraled unmyelinated sensory nerve terminals encapsulated by modified Schwann cells and then a thin oval sheet of FCT which forms the outer capsule.
Function: When the corpuscle is deformed, it triggers the release of Na+ ions into the nerve terminal causing an action potential firing.
Stimulated by: Mainly fine or discriminative touch – sensitive to the shape and textural changes and movement of objects over there surface of the skin.
- Also stimulated by light pressure and low frequency vibrations.
Lamellar Corpuscles?
Location: Deep dermis and hypodermis
- Also found in a variety of other organs.
Structure: Consists of a single dendrite lying within concentric layers of collagen and specialized fibroblasts.
- The layers of collagen are separated by gelatinous interstitial fluid, meaning the dendrite is isolated from other stimuli because of position and structure.
Function: Deformation of the capsule open pressure sensitive Na+ channels in the sensory axon. The inner layers covering the axon terminal relax quickly so that Ap’s are discontinued.
Stimulated by: Deep pressure and vibration.
Bulbous corpuscles
Location: deep dermis and subcutaneous tissue, joint capsules and fingernails.
Structure: Formed of a network of dendrites intertwined with a core of collagen fibres that are continuous with that of the surrounding dermis, all surrounded by a capsule.
Function: Important for signaling continuous states of deformation of tissues. E.g., heavy, prolonged touch.
- In joint capsules they have a role in proprioception of joint movement, in the fingernails they may have some role in monitoring the slippage of objects across the surface of the skin.
Stimulated by: Sustained deep pressure and stretching/distortion of skin.
How is blood flow controlled in the skin?
- Smooth muscle in the artery wall Is under control of the sympathetic nervous system.
- Precapillary sphincters are located at the junction between arteries and capillaries, these are also under sympathetic control.
- Noradrenaline acts on the alpha 1 adrenergic receptors to cause constriction of the capillaries and reduced skin blood flow.
What are the four main mechanisms for heat transfer?
Radiation – infra-red rays from our body to environment.
Evaporation – moisture on body is evaporated by heat energy.
Conduction – when our body is in contact with another cooler object heat transfer will occur down a gradient.
Convection – When there is flow of air/water surrounding the body, meaning there in no decrease in the heat flow gradient and heat is constantly passed.
What are eccrine sweat glands
- Allow us to decrease our body temperature by evaporation.
- They produce sweat in the cells of the gland, and this is then released by exocytosis into the ducts.
- The secretion is watery and contains electrolytes and antibacterial.
- Innervated by the sympathetic nervous system.
First degree burns. What parts of the skin do they affect? How long do they take to heal? Features.
- Superficial – only involving outer layer of epidermis.
- Red/pink in colour, dry and painful (as skin receptors are still functioning), with no blisters.
- Skin is still intact and retains its barrier properties.
- 3-10 days to heal.
Second degree burns. What parts of the skin do they affect? How long do they take to heal? Features.
- Can be partial or full thickness of the dermis.
- Partial second degree burns are painful, moist, red and blistered, healing in 1-2 weeks.
- Full thickness burns are pink/red/white mottled with blisters and oedema, healing in ~1 month.
- In a full thickness second degree burn, some receptors may be lost but hair follicles ans sweat glands remain.
Third degree burns. What parts of the skin do they affect? How long do they take to heal? Features.
- Full thickness of the skin
- Can be black/white/red.
- All receptors have been destroyed so no pain.
- Weeks or even months to regenerate.
Complications of burns
- Dehydration and hypovolemic shock
- Infection/sepsis
- Hypothermia
- Hyperkalemia
