SA:V + Gas Exchange Flashcards
(20 cards)
What is ficks law?
rate of diffusion is proportional to SA x ∆conc/distance
What is the relationship between size, SA:V and rate of diffusion?
as size increases, SA:V decreases and rate of diffusion decreases
What is the relationship between SA:V and metabolic rate?
as SA:V decreases, metabolic rate decreases because rate of heat loss decreases
What. are the features of specialised exchange surfaces?
short distance
transport system
selectively permeable
movement of environmental medium
large SA
Why are most exchange surfaces internal to body?
protection from damage (thin) air is not dense, so they are not supported
reduce water and heat loss
What is specialised around the lungs in human gas exchange?
pleural membrane and fluid around lungs reduce friction
How are the alveoli specialised as a gas exchange surface?
walls contain elastic tissue -> recoil for exhalation
lots of alveoli->large SA
1 cell thick
squamous endothelium in capillary + squamous epithelium in alveoli
surfactant fluid inside alveoli
-> prevents alveoli from collapsing and sticking together
capillary network
Why is a capillary network good for gas exchange?
constant blood flow
maintain large concentration gradient
What happens when you exhale?
external intercostals relax and ribs fall
diaphragm relaxes and pushed up by displaced organs underneath
vol. of chest cavity decreases
recoil of elastic tissue between alveoli decreases lung vol.
pressure in lungs increases and rises above atmospheric pressure
air moves out
What happens when you inhale?
external intercostals contract to raise ribs
diaphragm contracts to become flatter and pushes digestive organs down
vol. of chest cavity increases
elastic tissue between alveoli is stretched, increasing lung vol.
pressure in chest cavity drops below atmospheric pressure
air moves in
How is greater inhalation and expulsion of air achieved during strenuous conditions?
Stronger diaphragm contraction
increases depth and rate of breathing
How do different structures enable mass flow of air to be maintained?
c-shaped cartilage rings in trachea prevent airways collapsing due to pressure changes
Smooth muscle + elastic tissue control diameter of airway -> increases ventilation during exercise
How are the lungs specialised to protect the alveoli from damage?
trachea + bronchi lining
goblet cells produce mucus which trap particles + bacteria + viruses
cilia move to push mucus up + out of airways
How do you measure pulmonary ventilation rate?
tidal volume x breathing rate
What is pulmonary ventilation?
total volume of air that is moved into the lungs per minute
How can pulmonary ventilation be increased?
increase breathing depth and rate
How is the structure of gills specialised for gas exchange?
lots of filaments with lamellae (large SA)
Thin lamellae walls (short diffusion distance)
network of capillaries (maintains conc. gradient)
Why isn’t it possible for fish to have lungs to replace environmental medium (to maintain conc. gradient)
water is more dense than air
too much energy required to expel medium (exhale)
movement could damage gas exchange surface
How is conc. gradient maintained across gills?
water into mouth and out of operculum
countercurrent mechanism:
blood and water flow in opposite directions
so conc. gradient maintained along whole length of gill
What are the steps to fish gas exchange?
fish opens mouth
- buccul + operculum cavities expand increasing V and decreasing P
Water flows into opercular cavity down pressure gradient, moves over gills
opercular flaps open + cavity shrinks causing water to flow out
