1. SHARK RESPIRATORY SYSTEM

2. Respiratory Evolution
respiration requires large amounts of oxygen
adapted to the limited supply of oxygen and high density medium
myoglobin
evolved efficient structures to minimize energy consumption
move water steadily in a one direction
pump water through a spiracle
evolved as a reduced branchial pouch
advantageous because opening avoids inspired water over delicate gill surfaces

3. Shark Respiration water passes into the mouth and spiracles
through the 5 gill slits
the gill slits close and the pharyngeal chamber expands to suck in water
when pharynx is filled, the mouth closes and gill chambers expand and fill with water
then the gill slits open and the chambers constrict to flush out the water

4. Inspiration inspiration
spiracle opens and reduces the pressure within the shark
allows water to be sucked in without much energy loss
branchial chambers close their external gill slits
reduces pressure and allows water to flow into the branchial chambers thus bathing the gills

5. Inspiration water passes over the gills in one direction
second lamellae
obtain efficient gas exchange through counter current flow
blood and water flow in opposite directions
water contains more oxygen than blood
creates a gradient for absorption of more oxygen into the blood along the secondary lamellae
diffusion

6. Fish Gills
Bony fish respiration

11. Expiration conserves energy through expiration
mouth and spiracle both close
causes pressure to build
increased pressure will cause the visceral skeleton to bend
the stored energy helps to force the septum open
flap which covers the external gill slits

12. Gill Slits
when looking down the gill slits you will see one half of a gill
demibranch
holobranch
2 demibranchs, internal septum, blood vessels, nerves and muscles
at the base of the holobranch are the gill rakers
prevent food from escaping through the gill slits

13. Gill Slits demibranchs
consist of primary lamellae and secondary lamelle which branch off the primary
radially folded
highly vascularized tissue