11.1 Gas exchange in humans Flashcards
function of gas exchange system
responsible for getting oxygen into the blood and removing carbon dioxide as a person breathes
features of gas exchange surfaces
-large surface area
-thin epithelium
-good blood supply
-good ventilation
why large surface area
millions of alveoli that cluster at the tips of the bronchioles increase the surface area for gases to diffuse. this gives more space for diffusion to take place thereby speeding up the rate of gas exchange
why thin epithelium
the alveoli walls are very thin as they are only one cell thick. it reduces the distance across which the gases must diffuse to ensure rapid diffusion
why good blood supply
the alveoli have a large capillary network that are very close to they alveoli so that transport of gases to and form respiratory surfaces is fast and efficient. this maintains the concentration gradient by rapid transport of oxygen away by blood
why good ventilation with air
ventilation mechanism such as breathing, moves a good supply of oxygen over respiratory surfaces to increase the rate of gaseous exchange. the thin film of moisture on the wall of alveolus helps oxygen to dissolve in it before diffusing into blood capillaries. this ensures that the concentration gradients are maintained
identify these parts on diagram:
-larynx
-trachea
-lungs
-bronchi
-bronchioles
-alveoli
-capillaries
-diaphragm
-ribs
-intercostal muscles (external & internal)
function of cartilage in trachea
-trachea is lined with C-shaped rings of cartilage
-these rings of cartilage strengthen and support the trachea. they keep the trachea open during breathing and prevent it from collapsing during inspiration when air pressure falls below atmospheric pressure
what is ventilation
the act of moving air into and out of the lungs to allow gas exchange to occur
what happens during inspiration
-external intercostal muscles contract
-this pulls the rib cage upwards and outwards
-diaphragm contracts and moves downwards
-the volume of the thoracic cavity increase
-the pressure of the thoracic cavity decrease
-lungs expand (volume increases, pressure decreases)
-high pressure in atmosphere forces air into lungs with low pressure
what happens during expiration
-the external intercostal muscles relax
-this lowers rib cage downwards and inwards
-diaphragm relaxes and moves back upwards
-volume of thoracic cavity decreases
-pressure of thoracic cavity increases
-high pressure in the lungs forces air out of the lungs
investigation with limewater about differences in composition of inspired and expired air
-during inspiration, bubbles appear at left tube
-during expiration, bubbles appear at right tube
-left tube does not show any visible changes as inspired air has very little carbon dioxide
-right tube shows cloudy limewater as expired air contains a high concentration of carbon dioxide
-with hydrogencarbonate indicator, left tube is red (alkali) and right tube changes to yellow (acidic)
difference in oxygen in inspired and expired air
-inspired air 21%
-expired air 16%
-the inhaled oxygen diffuses through the walls of the alveoli and enters the bloodstream since the concentration of oxygen in the blood is lower
difference in carbon dioxide in inspired and expired air
-inspired air 0.04%
-expired air 4%
-respiration produces carbon dioxide and is carried by the bloodstream to be released at the alveolar surface of the lungs
difference in water vapour in inspired and expired air
-inspired air - varies and never saturated (less)
-expired air - saturated (more)
-lining of the alveoli is coated with a film of moisture in which oxygen dissolves. some of this moisture evaporates into alveoli and saturates the air with water vapour. the air breathed out therefore always contains more water vapour than the air breathed in
investigation on the effects of physical activity on rate and depth of breathing
- count number of breaths taken during 1 min at rest
- measure how much the chest expands during each breath using measuring tape. find the average chest expansion over 5 breaths
- exercise for 3 minutes
- immediately after exercise, count the number of breaths taken in 1 min and measure the average chest expansion over 5 breaths
effects of physical activity on rate and depth of breathing
-exercise increases the rate and depth of breathing
effects of physical activity on rate and depth of breathing
-exercise increases the rate and depth of breathing
-exercise causing the body cells to respire faster to release more energy
-more carbon dioxide is produced so there’s an increased carbon dioxide concentration in the blood
-this is detected by the brain, which signals the body to increases the rate and depth of breathing
-this in turn allows gas exchange to happen more rapidly. therefore carbon dioxide is removed faster from the body and also there’s an increased intake of oxygen which is supplied to respiring cells faster
how is the breathing system protected
-thin layer of mucus lines the respiratory tract
-this mucus is produced by cells called goblet cells
-the respiratory tract is also lined with ciliated epithelial cells
-these cells have tiny hairs on them called cilia
-the mucus produced by goblet cells trap pathogens and particles.
-the cilia beat and push the mucus away from the lungs towards the throat where it can be swallowed
