Skin and body membranes

Question 1

What do body membranes do?

Answer 1

line or cover, protect and lubricate body surfaces

Question 2

What makes up the membranes?

Answer 2

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

Question 3

Describe the mucous membrane

Answer 3

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

Question 4

Describe the serous membranes

Answer 4

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

Question 5

describe the synovial membrane

Answer 5

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

Question 6

Describe the structure of the skin

Answer 6

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).

Question 7

Describe the epidermis

Answer 7

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

Question 8

What is melanin?

Answer 8

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

Question 9

What does melanin do?

Answer 9

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

Question 10

How is white skin pink?

Answer 10

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

Question 11

What can give skin a yellow colour?

Answer 11

excessive levels of bile pigments in the bluff and subcuntaneous fat

Question 12

What are the two types of sweat glands?

Answer 12

eccrine

apocrine

Question 13

describe the eccrine sweat glands

Answer 13

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

Question 14

decsribe apocrine sweat glands

Answer 14

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

Question 15

Where does heir grow from ?

Answer 15

bottom of hair follicles situated in epidermal cells in the dermis

Question 16

What are arrector pili?

Answer 16

bundles of muscle fibres attached to the hair follicles

Question 17

what causes good bumps?

Answer 17

contraction makes the hair stand up and raises the skin

Question 18

Describe sebaceous glands

Answer 18

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

Question 19

what are the functions of the skin?

Answer 19

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

Question 20

What is radiation?

Answer 20

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

Question 21

What is evaporation?

Answer 21

body heat converts water in sweat to water vapour

Question 22

What is conduction?

Answer 22

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

Question 23

What is convection?

Answer 23

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

Question 24

describe the control of body temp

Answer 24

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

Question 25

What happens with a fever?

Answer 25

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

Question 26

Describe hypothermia

Answer 26

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

Question 27

What happens in the formation of vitamin D?

Answer 27

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

Question 28

What are the most common skin imbalances?

Answer 28

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

Question 29

What are the changes in skin pigmentation in pregnancy?

Answer 29

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

Question 30

What is facial chloasma (melasma)?

Answer 30

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

Question 31

What are other changes in pregnancy?

Answer 31

• hair: thicker and glossier
• Skin conditions eg eczema may worsen or improve
• puritus (localised itching usually abdomen) occurs in 20% of women in 3rd trimester
• Breasts- dilation of superficial veins, pigmentation of areola and nipples change
• legs: oedema may be oresent around the ankles; varicose vceins may develop