3.2.4: Gas exchange in humans Flashcards
state the name of the specialised gas exchange surface in the lungs
the alveoli
explain how the lungs are adapted to provide a large surface area
the alveoli is folded providing a large surface area, there are many alveoli, there is a dense network of capillaries over each alveolus
explain how the lungs are adapted to provide a short diffusion pathway
capillary wall is one squamous endothelial cell thick, capillaries are really close to alveoli, alveolus wall is 1 squamous epithelial cell thick. The capillaries are so narrow that the RBCs touch the walls as the blood flows through the capillaries
explain how the lungs are adapted to maintain a steep concentration gradient
Blood flows away from the gas exchange site taking oxygen with it, deoxygenated blood flow towards alveoli, therefore the conc. of oxygen in the alveoli is always much higher than in the blood due to inhalation (ventilation)
What is the film of moisture lining the inside of the alveolus called?
the surfactant
what is the role of the surfactant
to keep the alveoli open
suggest one medical use for a similar artificial surfactant
to assist breathing in premature babies as the surfactant keeps the alveoli open
state the function of the epiglottis
to close over the entrance to the trachea when we swallow
with reference to the trachea, bronchi and bronchioles, explain the importance of the rings of cartilage
they allow the bronchioles to both expands and contract easily during ventilation, in turn allowing the bronchi to move and flex easily and in turn supporting the trachea to move and flex easily during breathing
with reference to the trachea, bronchi and bronchioles, explain the importance of the ciliated epithelium lining
they secrete mucus, which traps bacteria and dust particles, they beat upwards and sweep the mucus to the throat, thereby removing the mucus and making sure the airway is clear and free from any mucus to make breathing easier
Describe the relationship between volume and pressure
as volume increases, pressure decreases
Why is the process of ventilation in humans important?
ventilation maintains a steep concentration gradient as respiratory medium always flows down a pressure gradient, meaning we have to make the pressure in our body lower than the pressure outside when inhaling, and the opposite for when exhaling
describe the process and the steps of inhalation
external intercostal muscles contract, rib cage moves up and out, diaphragm muscles contract, diaphragm flattens. Volume of thorax increases, outer pleural membrane gets pulled outwards. Pressure in pleural cavity decreases. Inner pleural membrane pulls outwards pulling on surface of lungs, alveoli expand, pressure in alveoli decreases below atmospheric pressure and so air is pulled into alveoli down a pressure gradient
describe the process and the steps of exhalation
external intercostal muscles relax, rib cage moves down and in, diaphragm muscles relax, diaphragm returns to dome shape. Volume of thorax decreases, no pull applied to outer pleural membrane, pressure in pleural cavity increases. No pull on inner pleural membrane so no pull on surface of lungs. Alveoli compress, pressure in alveoli increases above atmospheric pressure, air forced out of alveoli down a pressure gradient
explain the importance of elastic tissue during normal expiration in humans
makes it easier to expand and contract the diaphragm/intercostal muscles
