Human gas exchange Flashcards
Why do mammals need a specialised gas exchange system/the lungs?
in mammals there is a high volume of oxygen and carbon dioxide that has to be absorbed and removed respectively, and large mammals have a small SA: volume ratio
they also maintain a high body temperature which is linked to them having high metabolic rates
What is the trachea?
a flexible airway supported by rings of cartilage to stop it from collapsing
What are the bronchi?
two divisions of the trachea, each leading to a lung
What are the bronchioles?
further branches of the bronchi, have muscles to allow them to constrict to control the flow of air in and out
What are the alveoli?
minute air-sacs at the end of the bronchioles, and the alveolar membrane is the gas-exchange surface. they have elastic fibres to allow them to stretch as they fill with air, and also can spring back
What is ventilation?
the constant movement of air into and out of the lungs
What happens during inspiration?
external intercostal muscles contract and internal ones relax
ribs are pulled upwards and outwards and the diaphragm muscles contract, which causes it to move down and flatten, which increases the volume of the thorax
lung/alveoli pressure decreases
air is forced into the lungs, as the pulmonary pressure is less than the atmospheric pressure
Where do gases move?
from an area of high pressure to an area of low pressure
What happens when volume increases?
pressure decreases
What happens during expiration?
external intercostal muscles relax
ribs move downwards and inwards, and the diaphragm muscles relax, moving upwards, which decreases the volume of the thorax
lung/alveoli pressure increases
air is forced out of the lungs as the pulmonary pressure is more than the atmospheric pressure
When do internal intercostal muscles contract?
during vigorous exercise, as at rest air is forced out by the elastic recoil of the lungs
What is the pathway travelled by oxygen?
-down the trachea, then the bronchi, then the bronchioles into the alveoli
-across the epithelial cell layer of the alveoli
-across the endothelium cell layer of a capillary
-into the blood
Why are the alveoli efficient at gas exchange?
there are over 300 million in each lung- large surface area
walls of the capillary and the alveoli are one cell thick- short diffusion distance
constant ventilation and circulation- maintenance of concentration gradient
red blood cells are slowed as they pass through the capillaries which allows more time for diffusion
Considering SA: volume ratios, how are animals adapted to living in hot and cold countries?
hot countries- have a longer, flatter shape that means more surface area so more heat loss
cold countries- have a shape that reduces surface area so less heat loss, like a sphere
What are the key features of the human gas exchange system?
cartilage rings- to stop the trachea from collapsing
muscle and elastic tissue- to allow for some movement
cilia and mucus-secreting cells like goblet cells- to trap pathogens to prevent harm to the alveoli
