6.6 -> 6.8 human gas exchange

Question 1

why lungs located inside body

Answer 1

1. air isnt dense enough to support and protect delicate structure
2. body would lose great deal of water and dry out

Question 2

lungs

Answer 2

lobed structure made up of highly branched tubules(bronchioles) which end in tiny air sacs(alveoli)

Question 3

trachea

Answer 3

flexible airway supported by rings of cartilage
- prevents trachea collapsing as air pressure inside falls when breathing in

tracheal walls made up of muscle, lined with ciliated epithelium and goblet cells

Question 4

bronchi

Answer 4

two divisions of trachea, each leading to one lung

produce mucus to trap dirt particles
have cilia that move mucus towards throat

Question 5

bronchioles

Answer 5

branching subdivisions of bronchi
walls made up of muscle lined with epithelial cells
- allows them to constrict so they can control flow of air in and out of alveoli

Question 6

alveoli

Answer 6

minute air sacs
diameter 100-300 micrometer
between them are collagen and elastic fibres
- allow them to stretch as fill with air when breathing in then spring back during breathing out to expel co2
lined with epithelium

alveolar membrane is gas exchange surface

Question 7

inspiration

Answer 7

external intercostal muscles contract, while internal intercostal muscles relax

ribs pulled upwards and outwards, increasing volume of the thorax

diaphragm muscles contract, causing it to flatten, which also increases volume of thorax

increased volume of thorax results in reduction of pressure in the lungs

atmospheric pressure is now greater than pulmonary pressure, so air is forced into the lungs down concentration gradient

Question 8

expiration

Answer 8

internal muscles contract, while external muscles relax

ribs move downwards and inwards, decreasing volume of the thorax

diaphragm muscles relax and so it is pushed up again by contents of the abdomen that were compressed during inspiration. volume of thorax is therefore further decreased

decreased volume of thorax increases the pressure in the lungs

pulmonary pressure is now greater than that of the atmosphere, and so air is forced out of the lungs(from recoil of elastic tissue)

Question 9

pulmonary ventilation rate

Answer 9

total vol of air moved into the lungs during 1 minute

tidal volume x breathing rate

Question 10

tidal volume

Answer 10

volume of air normally taken in at each breath when the body is at rest

Question 11

6 reasons diffusion of gases between alveoli and blood is rapid

Answer 11

1. red blood cells are slowed as passed through pulmonary capillaries, allowing more time for diffusion
2. distance between alveolar air and red blood cells is reduced as red blood cells are flattened against capillary walls
3. walls of both alveoli and capillaries are very thin and so distance for diffusion is short
4. alveoli and pulmonary capillaries have large total sa
5. blood flow through pulmonary capillaries maintain conc gradient
6. breathing movements constantly ventilate lungs and action of heart constantly circulate blood around alveoli, ensuring steep conc gradient