Integumentary system Flashcards
(24 cards)
The body must be able to:
Determine the change is occurring
Know in which direction & how far from normal the change is
Cause functional changes to restore (negative feedback) or enhance (positive feedback) the original change
Homeostasis
When the bodies organs function together to maintain a stable internal environment
Positive feedback
Amplifies the change by acting in the same direction as the change. Eg childbirth, blood clotting and inflammation.
Negative feedback
Reverses the change, returning it to normal. Eg maintaining blood sugar and body temp
Skin structure
3 layers. Epidermis, dermis and hypodermis or subcutaneous.
Epidermis layer
4-5 layers of closely packed cells. Stratum basale Stratum spinosum Stratum granulosum Stratum lucidum Stratum corneum Contains keratinocytes and melanocytes, merkel cells and langerhans (denteitic) cells.
Dermis
2 layers
Papillary and reticular
Contains hair follicles, sweat (sudoriferous) glands, oil (sebaceous) glands, touch receptors and a good blood supply.
CT with lots of collagen and elastic fibres made my fibroblasts.
Hypodermis, subcutaneous
Subcutaneous or superficial fascia attach skin to muscle. Contains fat
Integumentary key functions
Provides external protections, regulates body temperature, sensory organ, excretion, vitamin D synthesis, immunity
Regulation of body temperature
By sweating and changing superficial vein diameter and blood flow.
(37*C)
Thermoreceptors are located
Skin, mouth, superficial pharynx, oesophagus, stomach, and intra abdominal veins.
Keeps hypothalamus informed (temp regulatory centre)
Heat conservation
Under cold stress Sympathetic activity, adrenaline & metabolic rates increase.
Vasoconstriction of superficial veins re-routes warm blood deeper into the body.
Involuntary muscle movement produces shivering.
Hair raises to trap warm air
Cooling occurs when
(a) Vasodilation of superficial veins brings blood to the body surface and heat is lost to the environment by radiation convection & conduction.
Radiation: Infrared heat moves from warm to cool
Conduction : Heat movement during direct contact
Convection : Warm air around body rises & is replaced by cooler air which body heats.
(b) An increase in perspiration results in increased evaporation, cooling the skin but effectiveness is dependent on the humidity. Can lose 0 -12 L/day
Perspiration is produced by Sudoriferous glands:
Eccrine or Merocrine glands
Simple coiled tube under sympathetic control produce hypotonic, acidic sweat b
Apocrine glands
Mostly in axillary and anogenital areas. Produce sweat with additional fatty substances and proteins (pheromones).
Modified glands produce cerumen.
Protection
Chemical, biological, and mechanical barriers
Chemical barriers
acid mantel & melanin (from UV radiation). Sebum from Sebaceous glands soften & lubricates skin, is antimicrobial & slows water loss.
Mechanical barrier
keratin, including hair & nails, protect from abrasion & dehydration.
Biological barrier
dendritic cells, macrophages protect from microbial invasion
Sensations from sensory receptors
Free nerve endings: temperature, touch, pressure & pain
Hair receptors : hair movement
Merkels disc: Light pressure
Meissner’s corpuscle: Light pressure
Ruffini’s endings: Deep pressure, stretch
Pacinian corpuscle:Deep pressure, stretch
Excretion
For loss of some ions, water and nitrogen containing waste
Blood reservoir
carrying 8-10% of total blood flow and is highly variable.
Synthesis of vitamin D
when UV rays from sun promote production of a Vitamin D precursor by the epidermis
Stores
Fat and far soluble vitamins (A, D, E & K
