7.2 The mammalian gaseous exchange system Flashcards
the need for humans
They’re big and have a small SA:V ratio
Active and maintain own body temperature so high metabolic rate
nasal cavity
a large surface area with a good blood supply, which warms the air to body temperature
a hair lining which secretes mucus to trap dust and bacteria protecting lung tissue from irritation and infection
moist surfaces, which increase the humidity of incoming air, reducing evaporation from exchange surfaces
Trachea
wide tube supported by incomplete rings of strong flexible cartilage, preventing collapse.
Rings incomplete so food can move easily down the oesophagus
ciliated epithelium and goblet cells, which secrete mucus to trap dust and dead micro organsims. Cilia beat to move mucus away from lungs
bronchus
smaller supporting rings of cartilage
split in two to form the left and right bronchus
bronchioles
no cartilage rings.
smooth muscle which contract and the bronchioles constrict and relaxes and the bronchioles dilate
flattened epithelium
alveoli
tiny air sacs
200-300 micrometers in diameter
flattened epithelial cells, collagen and elastic fibres
elastic recoil- alveoli stretch as air is drawn in. when returning to original size, they help squeeze air out.
adaptions of the alveoli
large surface area- millions of them
walls only one epithelial cell thick, short diffusion distance
good blood supply- network of many capillaries
good ventilation
lung surfactant enables the alveoli to reman inflated
rib cage
semi rigid case within which pressure can be lowered with respect ot the air outside it
diaphragm
broad domed sheet of muscle, forming the floor of the thoraz
intercostal muscles
in between the ribs
pleural membranes
line the thorax and surround the lungs. the space between them is the pleural cavity and is filled with a thin layer of lubricating liquid so membranes slide easily over each other as you breath
inspiration
diaphragm contracts, flattening and lowering
external intercostal muscles contract, moving rib cage up and out
vol of thorax increases so pressure decreases, lower than the atmospheric air
air drawn in, equalising pressure
expiration
passive
diaphragm relax, moves up to its resting dome shape
external intercostal muscles relax, ribs move down and in
elastic fibres return to normal lengh
vol of thorax decreases, pressure increases to above atmospheric air pressure
air moves out until pressure is equal
exhaling forcibly
using energy
internal intercostal muscles contact, ribs pulled down hard and fast
abdominal muscles contracting helps force diaphragm up to rapidly increase lung pressure
