The Evolution of the Aortic Arches Embryonic Human Circulation

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Topic 21: Aortic Arch & Embryonic Circulation Aortic Arch Evolution

What view are we getting here? The evolution of the aortic arches ______ 6-8 gill & aortic arches How do the aortic arches differ among taxa? Heart Ventral aorta What vessels do they become? Afferent branchial aa. Gill capillaries Efferent branchial aa. Lamprey Dorsal aorta Body & Head Embryonic human circulation

Why does it differ from adult circulation? ______ What is the pattern of embryonic circulation Efferent branchial aa. develop collector loops and what structures are involved? Aortic arch I efferent spriacular a. How does it change with adulthood? Aortic arch II modified Aortic arches III-VI Shark unmodified Liem et al. Focus 19-1

Aortic Arches of Aortic Arches of the Shark Actinopterygii

Dorsal view representation Loss of aortic arch ______ Very generalized Loss of aortic arch ______ ______I Aortic arches III-VI serve the ____ I II II ______ How many gill arches do bony III III ______fishes have? IV IV Aortic arches V V I: Efferent spiracular a. Loss of collector loops sensory function More efficient gas exchange at gills VI VI II: Modified gas exchange function Anterior dorsal aortae connect – III-VI: Unmodified gas head circulation exchange function

Anterior ventral aorta contributes to ______

Liem et al. Focus 19-1 Liem et al. Focus 9-1

• Oxygenated • Deoxygenated

Aortic Arches of Dipnoi Aortic Arches of Dipnoi I II III IV V VI

Valves are used to bypass Evolution of ______respiratory structures I Supplied by ______, II To bypass lungs: pulmonary a. III Shut aortic arches Drained by new pulmonary v. ______Gills used to ‘breathe water’ IV

V To bypass gills: Aortic arches III & IV bypass I II III VI Shut aortic arches IV V gills VI ______

Aortic arches serving gills What are shunts? Modified ______

______

Lungs used to breath air

Liem et al. Focus 19-1 Liem et al. Fig. 19-9; tamuk.edu

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Aortic Arches of Larval & Adult Adult Amphibians Amphibians

Loss of circular cranial artery Tadpole

Evolution of “tetrapod” carotid Retains aortic arches III, IV, V VI

artery system Tadpole Loss of aortic arches I & II ______: Gills Loss of dorsal aorta between _____: Bypass lungs aortic arches III & IV Ductus arteriosus ______(arch III) supplies internal & external Adult carotid aa. Typical tetrapod circulation Loss of aortic arch V Aortic arch III: carotid Adult Aortic arch IV becomes Aortic arch IV: systemic ______ Aortic arch VI: Aortic arch VI is pulmocutaneous ______Skin Liem et al. Focus 19-1; Fig. 19-10 Liem et al. Fig. 19-10

Aortic Arches of “Reptiles” Aortic Arches in Birds

How does this differ from How does this differ the adult amphibian? from a turtle? Basics the same Carotid circulation is similar ______division of ventral aorta Subclavian aa. come off common carotid a Slight asymmetry in systemic circulation Left aortic arch IV ______! Carotid duct increases connectivity between Right aortic arch IV is head and body ______ No pulmonary circulation to ______

Liem et al. Focus 19-1; Fig. 19-12 Liem et al. Fig. 19-14

Aortic Arches in Mammals Aortic Arches in Mammals

Aortic arch developmental homology with adult circulation

Similar to birds, but left aortic arch IV is systemic What does this tell us?

Even more asymmetry Left subclavian a. comes off L aortic arch IV Right sublavian a. is right aortic arch IV

Liem et al. Fig. 19-14 Liem et al. Fig. 19-15

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Aortic Arch Lampreys Evolution Sharks

1. 8 aortic arches Ray-finned 2. 6 aortic arches fishes 3. Collector loops 4. Aortic arch I efferent spiracular a. 5. Aortic arches I & II lost Lungfish 6. Circular cranial circulation 7. Aortic arch II modified 8. Aortic arches III & IV shunt past gills 9. Aortic arch VI Pulmonary Amphibians 10. Carotid circulation established 11. Aortic arch IV Systemic 12. Loss of cutaneous a. “Reptiles” 13. Retention of carotid duct 14. Right aortic arch IV Systemic 15. Left aortic arch IV Systemic Birds

Mammals Liem et al. Focus 19-1

Mammalian Embryonic Circulation

Why would embryonic circulatory needs differ from those of the adult?

Human Embryo

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Human Embryonic Circulation Human Embryonic Circulation

______ Blood to placenta ______ ______ Become medial umbilical ligament Oxygenated blood from placenta to body ______ Mixes with deoxygenated blood from Become round ligament of liver tissues ______ ______ Closes and dissapears Shunt to bypass liver Fetal alcohol syndrome All blood from the guts now goes to the liver via hepatic portal v. ______ Shunt from R atrium to L atrium ______ Blood bypasses lungs Closes and becomes fossa ovale ______ ______ Shunt from pulmonary a. to aorta Closes and becomes the Blood bypasses lungs ligamentum arteriosum

Liem et al. Fig. 19-16 Liem et al. Fig. 19-16

Human Embryonic Circulation

FO – fossa ovale