The Ear + The skin Flashcards
2 functions of the ear
hearing
balance
3 parts of a mammalian ear
air-filled outer ear
air-filled middle ear
fluid-filled inner ear
3 parts of the outer ear
pinna
external auditory canal
eardrum
pinna is composed of
cartilage
function of pinna
helps to collect and funnel sound waves into the ear
external auditory canal
lined with hairs and wax-producing cells
function of external auditory canal
wax traps dirt, microbed etc, and protects ear
eardrum
a tightly stretched membrane that separates the outer ear from the middle ear
function of eardrum
transfers sound waves to the middle ear
middle ear contains
3 bones called the malleus, the incus and the stapes (hammer, anvil and stirrup)
function of the bones
carry sound waves from the eardrum to the oval window
function of oval window
transfers sound waves to the inner ear
eustachian tube
connects middle ear with the pharynx
function of eustachian tube
keeps air pressure equal on both sides of the eardrum
inner ear
a coiled tube filled with fluid (lymph)
contains sensory cells
inner ear consists of
the cochlea
the semi-circular canals, utricle and saccule
function of the cochlea
hearing - converts sound waves into nerve impulses
function of the semi-circular canals, utricle and saccule
balance - they detect movement, acceleration and position of head in relation to gravity
sound is caused by
vibrations in the air
first thing that happens to the sound
vibrations pass through the outer ear and ear drum to the middle ear
when sound waves are in middle ear
they pass via the ear bones and oval window the the fluid in the cochlea
when sound has reached cochlea
movement in the fluid of cochlea stimulates sensory hair cells
sensory cells send electrical impulses to the brain via the auditory nerve
brain interprets these as sound
balance
semi-circular canals at right angles to each other filled with lymph, receptors in the canals detect movement in 3 planes
movement of head disturbs fluid in canals and stimulates receptors
balance receptors stimulated
impulses sent to the cerebellum of the brain via the vestibular nerve and muscles are stimulated to contract
3 planes
forward, backward and circular
organs of smell and taste
chemoreceptors
chemoreceptor
stimulated by chemicals dissolved in a watery medium
organ of smell
olfactory surface in the nose
lining of top of inside of nose
epithelium
epithelium consists of
mucus-secreting cells
receptor cells
function of mucus secreting cells
provides water medium
function of receptor cells
stimulated by chemicals dissolved in the watery medium (mucus)
organ of taste
taste buds
taste buds
consist of groups of sensory cells in the skin of the mouth, tongue and pharynx
4 basic tastes in humans
sweet
sour
salty
bitter
2 layers of skin
outer epidermis
inner dermis
3 layers of stratified epidermis
malpighian layer
granular layer
cornified layer
malpighian layer
cells divide by mitosis, replacing dead cells rubbed off
contains melanin, pigment that gives colour to skin
granular layer
a layer of living cells that become filled with grains of keratin as they are moved towards the outside
cornified layer
thick layer of dead, flattened cells, being rubbed off continuously and replaced from underneath
dermis
layer of connective tissue
what does the dermis contain?
protein fibres (collagen), blood and lymph vessels, sensory receptor cells, sweat glands, hair follicles, sebaceous glands and muscles
adipose tissue (sub-cutaneous fat)
layer of fat storing cells under the dermis
3 functions of adipose tissue
insulation
energy store
protects muscles
5 functions of skin
protection excretion vitamin production sense organ temperature regulation
how does the cornified layer protect
the outer layer of dead cells, with keratin, that prevent entry of bacteria, loss of H2O and injury
how does melanin protect
protects body from uv rays of sun
how do sebum and sweat protect
make the skin acidic enough to inhibit harmful bacteria
sebum also prevents the skin from drying out and cracking
excretion
sweat glands produce sweat, which is a watery medium containing small quantities of salt, ammonia and urea
vitamin production
the action of ultraviolet light on fat in the skin produces vitamin D
sense organ
the skin contains receptors to detect heat, cold, pressure, touch and pain
temperature regulation
the body has a constant internal temperature of 37ºC
skin maintains this, with sweat glands, blood vessels and hairs
3 ways in which the skin can reduce body temperature in hot conditions
sweat glands secrete, heat lost by evaporation
arterioles expand, more blood flows the skin capillaries
hairs lie flat, relaxation of erector muscle - less air trapped
2 ways to keep body temperature up by skin
hairs stand up to reduce heat loss - warm air trapped
arterioles narrow, less blood to skin capillaries
2 additional ways of keeping up body temperature
metabolic rate increases (thyroxine secreted)
shivering
ectotherms
animals whose body temperature varies with the temperature of the environment (cold-blooded)
endotherms
animals whose body temperature does not vary with the temperature of the environment
