Lesson 13 - countercurrent, concurrent, crosscurrent

who else has spiracles?

Rays and skates -> capillaries line the spiracle and assist with oxygenated water from dorsal to ventral

Who uses counter current exchange?

a) all fish using gills (bony fish) b) chondrichthyans

What does Ram Ventilation do for the chondrythyans?

a) helps to increase rate of flow of gases across the ventilatory/respiratory surface b) speeds up the delivery of the respiratory medium (water)

What kind of air flow do birds exhibit?

a) in the lungs: unidirectional b) upper airways: bidirectinoal

The shark doesn't have what like most fish?

an Opercular cavity

where is the counter current exchange happening

at the filaments of repetitive gill arches

Who uses a cross current flow?

birds

What is an opercular cavity?

bony/cartilaginous protective shield over the gill region

why is the maintenance of the gradient important?

endotherms battle the problem of having a very low oxygen available to them when they go to great altitudes

what do chondrythyans rely on for counter current exchange?

gill arrangement

what do the blood capillaries do?

it communicates with the air capillary through the *crosscurrent flow*

How does the right angle to the air capillaries help?

it helps to maintain GRADIENT

What is the spiracle?

it is a hole that is posterior to each eye but now vestigial (does not have a real function- no capillary beds)

what happens to the air within the air capillaries?

it shows a double way because depending upon where the bird is in flight, the air capillaries go through a significant fluctuation (*doesn't have a significant influence on the unidirectional flow through the major channels of each parabronchi though)

How many of the parabronchial channels do the birds have?

numerous

What do the chondrythyans use for ventilation?

only some use the dual pump but most use RAM VENTILATION

In concurrent exchange what happens?

oxygen that is present in the water diffuses at a very fast rate into the capillary blood flow and the gradient is lost. -> results in an equilibrium at a 50% to 50% (suboptimal)

What is Ram Ventilation?

the forward movement of the animal with their mouths partially open (not enough to lose their fusiform shape and hydrodynamic design) so that the oxygenated water comes in unidirectionally and through the gill curtains to the external gills

how many types of capillary beds coming off of the parabronchial channel do birds have?

two! a) air capillaries (vertical) b) blood capillaries (horizontal at the right angle)

history of the spiracle?

was part of the first 6 external gill slits; could have been used to oxygenated water from dorsal to ventral

What is a counter current exchange?

water through the gill curtains and capillary blood flow are in opposite directions

in counter current exchange what happens?

when you follow the water's path, at each point there is slightly more oxygen in the water rather than in the same location of the blood stream. -> potential for optimal O2 loading due to no equilibrium