Ventilation Flashcards
Ventilation
= breathing: movement of respiratory medium across a gas exchange surface
usually involves muscular contraction
external respiration
exchange between medium and blood (gas exchange surface) - happens via simple diffusion
internal respiration
exchange between blood and tissues
cell respiration
tissue needs oxygen for aerobic cell respiration - production of ATP
passive diffusion
movement of gases across a semi-permeable membrane from high concentration to low concentration - no ATP required
more surface area, more diffusion
unidirectional vs bidirectional or tidal
unidirectional = more efficient = breathing water
bidirectional/tidal = not as efficient as it could be = breathing air
movement of medium across a gill current - countercurrent flow
blood flowing one way through lamellae and water flowing opposite direction between lamellae
sending blood to gills to pick up oxygen
diffusion occurs in secondary lamella
afferent branchial arteries = oxygen poor, delivers blood to secondary lamellae
efferent branchial arteries = oxygen rich
concurrent flow
movement in the same direction
less efficiency of transfer
types of vertebrate ventilation
ram ventilation water ventilation pulse pump/buccal pump frog ventilation aspiration pump
ram ventilation
forward motion of swimming; mouth open; water forced over gill curtain
in many species, occasional - bass, catfish
in some species, almost always - tuna, mackerel, sharks, billfishes
water ventilation: dual pump
“water-breathing fishes” - most ray-fins
water forced over gill curtain using buccal and opercular pumps
oral valve, buccal cavity, gill curtain, opercular cavity, opercular valve
muscular contraction/suction phase: pressure in chamber decreases as pump drops
muscular relaxation/force phase: increased pressure in chambers, water forced out
pulse pump or buccal pump
“air-breathing fishes” - lungfishes (clade dipnoids)
Exhalation Phase:
- transfer air from lungs to buccal chamber, buccal chamber expands, glottis opens, close oral valve
- expulsion of spent air, buccal cavity compresses, glottis closes, oral valve opens, spent air removed from body
Inhalation Phase:
- intake of fresh air, buccal cavity expands, open oral valve, glottis closed, pressure in buccal cavity decreases
- compression, buccal chamber compresses, glottis opens, oral valve closes, fresh air enters lungs
frog ventilation
modified buccal pump
no ribs, no diaphragm
- nares open, glottis closes, floor of buccal chamber lowers, fresh air enters buccal cavity
- glottis and nares open, flank muscles compress forcing spent air from the lungs past the air held in the buccal cavity and expelling it
- nares close, glottis opens, floor of buccal cavity elevates, air enters lungs
**What is modified in pulse pump of frogs compared to other amphibians and air-breathing fishes? No transfer of spent air to buccal cavity
vocal sac not involved; separated from buccal cavity by slits that open/close via muscle contraction
aspiration pump in amniotes
buccal pump has no role; air “sucked” in by creation of low pressure around lungs
when thoracic cavity expands (almost always involves rib movements), negative pressure draws air into lungs
when thoracic cavity compressed (almost always involves rib movements), positive pressure forces air out of lungs
mammal aspiration pump: diaphragm and rib movements
inhalation:
- active –> muscle contraction
- diaphragm contracts, moves caudally
- ribs move laterally and cranially
- volume of thoracic cavity increases; pressure decreases; air enters lungs
exhalation
- passive –> muscles relax
- diaphragm and intercostals relax
- thoracic volume decreases and lung pressure increases; air exits
forced exhalation is active
-internal intercostal muscles contract, rectus abdominis contracts
crocodylians: rib and liver movements
important components: diaphragmatic muscles: sort of act like a diaphragm but not homologous to the diaphragm, origin - pubis, insertion - posthepatic spetum posthepatic spetum liver intercostal muscles and ribs
Inhalation:
- intercostal muscles contract - ribs move cranially and laterally
- diaphragmatic muscles contract and pull liver caudally
- volume of thoracic cavity increases, pressure decreases
- air enters lungs
Exhalation:
- diaphragmatic muscles relax, liver moves cranially
- intercostal muscles relax, ribs move caudally and medially
- volume of thoracic cavity decreases, pressure in lungs increases
- air leaves lungs
liver acts like piston
ventilation in turtles
- ribs fused with dermal elements in carapace
- do not have diaphragm (mammal trait)
within the rigid shell, (anterior and posterior) limiting membranes alter their position under muscle contraction
inhalation:
- contraction of serratus and obliques abdominis
- space expands, pressure decreases
- air rushes in
exhalation:
- relaxation of transverse abdominis, pectoralis
- space decreases, pressure increases
- air forced out
forced exhalation:
- contraction of transverse abdominis and pectoralis
- air squeezed out of lungs
- active
snakes
ribs and associated muscles extend entire length of thorax to pelvis
regional compression and expansion of body wall inflates/deflates lungs
glottis opens/closes in conjunction with rib movements
glottis extends to anterior margin of oral cavity during feeding; “snorkel”
snake lungs:
- left lung reduced/absent in most species
- right lung is very elongated and has 2 regions to accomodate for eating whole prey; anterior respiratory region (faveoli; faveolar region) vs posterior saccular region (has nothing to do with gas exchange)
when swallowing prey: anterior thorax is expanded and can’t compress/expand lung… posterior ribs compress/expands saccular lung thus air moves across faveolar region and respiratory surfaces
birds
paired lungs with air sacs that lie among the viscera and extend into the cores of adjacent bones filling them with air instead of marrow
movement of rib changes shape of air sacs not lungs and air is then drawn into lungs
lowering sternum results in expansion of rib cage and inhalation; elevation of sternum compresses air sacs and air is expelled
