4.3 Gas Exchange Flashcards
give features of effective gas exchange
large surface area
thin layer - minimise diffusion distance
rich blood supply
moist + permeable surface
what is the main mammalian gas exchange organ?
the lungs
how are the alveoli adapted for gas exchange?
provide a large surface area
made up of a thin layer of epithelial cells- short diffusion pathway
steep concentration in gradient- capillaries have deoxygenated blood
what is the purpose of having elastic connective tissue in the alveoli?
helps to force air out of the lungs which are stretched when you breathe in- elastic recoil
describe inhalation as fully as possible
- is an active process
- muscles around diaphragm contract so it is lowered
- intercostal muscles between ribs also contract so ribcage moves up + out
- volume of chest cavity increases
- pressure in chest cavity decreases
- pressure is lower than atmosphere so air moves into lungs in order to equalise pressure
describe exhalation as fully as possible
- is a passive process
- muscles around diaphragm relax so it moves in
- intercostal muscles around ribs also relax so ribs move in and elastic fibres return to normal length(in alveoli)
- volume of chest cavity decreases
- pressure in chest cavity increases
- pressure is higher than atmosphere so air moves out of lungs to equalise pressure
name 3 gas exchange organs in insects and explain the function
spiracles - site of entry + exit of respiratory gases
tracheae - large tubes that carry air into body, supported by chitin spirals which make it impremeable to gases
tracheoles - single elongated cells with no chitin (permeable) - where most gas exchange occurs
how does the insect respiratory system work?
- air enters system through spiracles (the spiracles are a site of water loss so spiracle sphincters are kept closed as much as possible)
- air moves along trachea + tracheoles via diffusion
- large network of tiny tracheoles gives large surface area - most gas exchange occurs here
give two features of active insects
have high energy demands
have 2 methods of ventilation; mechanical ventilation and collapsible tracheae
describe mechanical ventilation
air is pumped into tracheal system.
spiracles open and insect makes muscular pumping movement of abdomen
movements change volume and pressure in body so air is drawn in and out
describe collapsible tracheae
increases the volume of air moved through the system
ventilating the movement of abdomen and inflate + deflate the tracheae
what happens if the insect is very active?
needs more oxygen, lactic acid builds up in muscle tissue
this affects osmotic concentration os cells so water moves out of tracheoles + into cells via osmosis
more surface area for gas exchange
describe gas exchange in water
- water is denser than air + contains less O2, so diffusion rates are lower
- gas exchange system of land animals would not work of f fish
- in gills, water only has to flow over them in one direction - ventilation
describe the process of ventilation in fish
- pressure in mouth cavity is reduced by floor of mouth being lowered + operculum moved outwards
- operculum acts as a valve as it is pressed against the body by higher outside pressure so water enters through mouth to equalise pressure
- volume of mouth cavity decreases + pressure increases by raising floor of mouth- valve in mouth prevents water from leaving
- increased pressure opens the operculum + water leaves- passes through gill filaments where gas exchange occurs
- ensures continuous flow of water over gills
adaptations of gills
large surface area rich blood supply thin walls countercurrent exchange system overlapping gill filaments
