Flashcards in The Integumentary system Deck (30):
What % of our body weight is accredited to the integumentary system?
What are the two major components of the integumentary system?
Cutaneous membrane (skin) and the accessory structures
What are the 2 major structures of the cutaneous membrane?
Epidermis (superficial epithelium)
Dermis (underlying connective tissue)
What is included in the accessory structures?
hair, nails, and multicellular exocrine glands- mainly located in the dermis
What is deep to the dermis and what is its function?
Hypodermis (superficial fascia)- loose connective tissue separates the integument from the deep fascia around other organs e.g. muscles and bones
What are the functions of the skin and hypodermis?
1) PROTECTION of underlying tissues and organs against impact, abrasion, fluid loss and chemical attack
2) EXCRETION of salts, water, and organic wastes by integumentary glands
3) MAINTENANCE of normal body temp through insulation or evaporative cooling
4) PRODUCTION of melanin to protect underlying tissue from ultraviolet radiation
5) PRODUCTION of keratin to protect against abrasion and serves as water repellent
6) SYNTHESIS of vitamin D3, a steroid that is converted to calcitriol a hormone important for normal calcium metabolism
7) STORAGE of lipids in adipocytes in the dermis and in adipose tissue in the subcutaneous layer
8) Detection of touch, pressure, pain and temp stimuli and relaying to nervous system
What is the epidermis dominated by?
Keratinocytes- the body's most abundant epithelial cells
What are basal cells (germinative cells)?
They dominate the stratum basale
They are stem cells whose divisions replace the more superficial keratinocytes that are lost or shed at the epithelial surface
What are tactile cells (merkel cells)?
Specialised epithelial cells are sensitive to touch - when compressed they release chemicals to stimulate sensory nerve endings
they are scattered amount the stratum basale where skin surfaces lack hair
What is the stratum spinosum made up of?
8-10 layers of keratinocytes bound together by desmosomes
The cells look like miniature pincushions
What is the structure of the stratum granulosum?
Consists of 3-5 layers of keratinocytes derived from the stratum spinosum- once these cells have reached this layer they have stopped dividing and have started making large amounts of keratin and keratohyalin
What is keratin and keratohyalin?
Keratin: a tough, fibrous protein - basic structural component of hair and nails - as these fibres develop the cells grow thinner and flatter and their membrane thicken and become less permeable
Keratohyalin: forms dense cytoplasmic granules which promote dehydration of the cell as well as aggregation and cross-linking of the keratin fibres
What is the stratum lucidum?
In the thick skin of the palms and soles - glassy stratum lucidum covers the stratum granulosum
The cells are flattened, densely packed, largely devoid of organelles and filled with keratin
What is the stratum corneum made up of ?
contains 15-30 layers of keratinised cells
formation of protective superficial layers of cells filled with keratin. This process occurs on all exposed skin surfaces except the anterior surface of the eyes
Define insensible perspiration:
loss of about 500 ml of water from the stratum corner per day due to evaporation - you are unable to see or feel the water loss
Define sensible perspiration:
Produced by active sweat glands
What are the two pigments within the epidermis that are present in variable quantities?
Melanin and carotene
- carotene: orange-yellow pigment that is most apparent in the stratum corneum of pale skinned people
- melanin: brown, yellow brown or black pigment produced by melanocytes in the stratum basale
What are freckles?
small pigmented areas on relatively pale skin - these areas are serviced by melanocytes producing larger than average amounts of melanin
What are lentigos?
They are similar to freckles but have regular borders and contain abnormal melanocytes
Senile lentigos (liver spots) are variably pigmented areas that develop on sun-exposed skin in older individuals with pale skin
What is jaundice?
Liver is unable to excrete bile, so a yellowish pigment accumulates in body fluid. In severe cases the skin and whites of the eye can turn yellow
What happens when large amounts of melanocyte stimulating hormone are secreted from the pituitary gland?
This hormone causes the darkening of the skin and an individual can get an extremely deep bronze tan
What is addison's disease?
the pituitary gland secretes large amounts of adrenocorticotropic hormone which is structurally similar to MSH and therefore causes a similar effect
What is vitiligo?
individuals lose their melanocytes (1% of the pop)- tends to be more common in patients with thyroid gland problems, addison's disease and other disorders - it is thought to occur due to the immune defences malfunctioning and antibodies attacking normal melanocytes - main problem is cosmetic particularly in darkly pigmented skin
What happens when the skin is exposed to sunlight?
Epidermal cells in the stratum basale and stratum spinosum convert a cholesterol related steroid in to cholecalciferol or vitamin D3
The liver then converts cholecalciferol into an intermediary product for the kidneys to synthesize the hormone calcitrol
What does calcitrol do?
essential for normal absorption of calcium and phosphorous by the small intestine
What is the function go epidermal growth factor (EGF)?
1) promoting division of basal cells in the stratum basale and stratum spinosum
2) accelerating production og keratin in differentiating keratinocytes
3) stimulating epidermal development and epidermal repair after injury
4) stimulating synthetic activity and secretion by epithelial glands
What does the papillary layer of the dermis consist of?
Consists of areolar tissue, contains capillaries, lymphatics and sensory neurones that supply the surface of the skin
What does the reticular layer of the dermis consist of?
Consists of an interwoven mesh network of dense irregular connective tissue containing both collagen and elastic fibres