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Flashcards in Skin and body membranes Deck (31)
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What do body membranes do?

line or cover, protect and lubricate body surfaces


What makes up the membranes?

epithelial cells, these are sheets of epithelial tissue and supported by connective tissue that line internal structures or cavities


Describe the mucous membrane

also known as mucosa. Moist lining of the alimentary respiratory and genitourinary tracts. Covers surface of body cavities open to exterior


Describe the serous membranes

they secrete serous watery fluid
pleura lines the thoracic cavity and lungs
pericardium lines the pericardial cavity and surrounds the heart
peritoneum line the abdominal cavity and surrounding organs


describe the synovial membrane

Lines cavities of moveable joints and surrounds tendons that could be injured rubbing against bones. It consists of areolar connective tissue and elastic fibres. Secrets clear, sticky, oily synovial fluid that nourishes the joints


Describe the structure of the skin

largest organ in the body has a surface area of about 1.5-2 m2. In some areas there are accessory structures like glands, hair, nails. Two main layers : the epidermis which cover the dermis. Between the skin and the underlying structures there is a subcantaneous layer composed of areolar tissue and adipose (fat).


Describe the epidermis

most superficial layer, varies in thickness, thickest being on the palms of hands and soles of feet. No blood vessels or nerve ending.
Surface cells are constantly rubbed off and replaced by those underneath- complete replacement takes about a month


What is melanin?

a natural skin pigment in the deep germinative layer (inner most layer of the epidermis)


What does melanin do?

protects the skin from UV rays in sunlight, exposure to sunlight promotes synthesis of melanin


How is white skin pink?

saturation of haemoglobin and the amount of blood circulating in the dermis.


What can give skin a yellow colour?

excessive levels of bile pigments in the bluff and subcuntaneous fat


What are the two types of sweat glands?



describe the eccrine sweat glands

major sweat glands open onto skin surface secreting clear watery fluid important in temp regulation


decsribe apocrine sweat glands

open at hair follicles and become active at puberty. Bacterial decomposition of their secretion causes body odour


Where does heir grow from ?

bottom of hair follicles situated in epidermal cells in the dermis


What are arrector pili?

bundles of muscle fibres attached to the hair follicles


what causes good bumps?

contraction makes the hair stand up and raises the skin


Describe sebaceous glands

secretes an oily antimicrobial substance called sebum, into hair follicles. present all over the skin except palms and soles of feet

provides some waterproofing and acts as a bactericidal and fungicidal agent, preventing infection. Also prevents drying and cracking, especially on exposure to heat and sunlight


what are the functions of the skin?

- invasion of micro- organisms
- chemicals
Physical agents - mild trauma, UV light
- dehydration
regulation of body temp


What is radiation?

the main mechanism, exposed parts of the body radiate heat away from the bosy


What is evaporation?

body heat converts water in sweat to water vapour


What is conduction?

clothes and other objects in direct contact with the skin take up heat


What is convection?

air passing over exposed parts of the body is heated and rises, cool air replaces it and convection currents are set up


describe the control of body temp

regulated by the hypothalamus and is sensitive to the temp of circulating blood. Responds to decreasing temp by sending nerve impulses:
- arterioles in the dermis which constrict decreasing blood flow to the skin
- skeletal muscles stimulating shivering

as body temp rises and in normal range, the negative feedback system switched off


What happens with a fever?

often a result of infection
chemical from inflammatory act on the hypothalamus resetting the thermostat to.a higher temp
Body responds by activating heat promoting mechanisms, eg shivering until the new high temp is reached
there is profuse sweating and vasodilation with flushed skin until body falls within normal range


Describe hypothermia

core temp below 35C
below 32 mechanisms that normally restore temp fail. shivering is replaced by muscle rigidity and cramps, vasoconstriction fails and BP, P and RR fall
confusion and disorientation
death usually occurs when temp falls below 25
individuals at extreme age eg neonates are prone as temp regulation is less effective


What happens in the formation of vitamin D?

7- Dehydrocholesterol is a lipid based substance converted to vitamin D by sunlight

used with calcium and phosphate in the formation and maintenance of bone


What are the most common skin imbalances?

infections- measles, cold cores
allergies - burns/ scalds classifies according to depth and/ or amount of surface are affected
loss of skin leads to loss of protection against infection, loss of water


What are the changes in skin pigmentation in pregnancy?

increase in MSH- progressive increase in skin pigmentation especially in women with dark hair and complection
a dark line develops from navel to pubis called linea nigra


What is facial chloasma (melasma)?

irregular, blotchy pigmentation usually in the shape of a butterfly can be common