The document compares the heart structures of various vertebrate groups. It notes that hearts evolve from two longitudinal tubes fusing in the mesoderm. The simplest hearts are found in cephalochordates like Branchiostoma, consisting of a sinus venosus, auricle and ventricle. Lampreys and harks have slightly more complex hearts with these chambers plus a conus arteriosus. Elasmobranch fish hearts are S-shaped tubes with these chambers. Teleost fish hearts are two-chambered with a sinus venosus, auricle, ventricle and bulbus arteriosus. Lungfish have transitional three-chambered hearts. Higher vertebrates evolve four-chamber

1. Comparative account of VERTEBRATE HEARTs
Dr Sutapa Datta
Assistant Professor of Zoology
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2. HEART
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• Heart is the central part of
circulatory system.
• Muscular
• Pumps blood throughout the body
• Vertebrate heart is having a
receiving chamber and a forwarding
chamber
•Two longitudinal tubes in
mesoderm fuse together to
form heart

3. • True heart lacking
• Part of Ventral Aorta below
pharynx becomes muscular and
contractile
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CEPHALOCHORDATA:
Ex: Branchiostoma sp
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4. CYCLOSTOME:
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• Sinus Venosus
• Auricle
• Ventricle
• Conus Arteriosus
Ex: Lamprey, Hagfish
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• Simplest heart
• Consists of the following
chambers in sequence:

5. ELASMOBRANCH FISH:
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Ex: Shark
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• Muscular, dorsoventrally bent
S-shaped tube
• Consisting of following
chambers in sequence:
• Sinus Venosus, Auricle,
Ventricle, Conus Arteriosus
SINUS VENOSUS: Thin walled, acts as a reservoir, opens
to Auricle through sinu-auricular aperture guarded by a
pair of valves
Auricle: large, thin walled, muscular, elastic, opens
ventrally to ventricle by auriculo-ventricular aperture
guarded by a pair of valves, receives venous return of
blood through SV
VENTRICLE: thick walled, muscular, opens to conus
arterious
CONUS ARTERIOUS: narrow, tubular, muscular, having a
series of semilunar valves
Accessory chambers: SV,CA
True chambers: A, V

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TELEOST FISH:
Ex: Bony fish
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• Small, Muscular two chambered with single circuit
of circulation- VENOUS HEART
• Consisting of following chambers in sequence:
Sinus Venosus, Auricle, Ventricle, Bulbus
Arteriosus
CONUS ARTERIOUS: In Amia CA reduced and the
number of valves are less. In Teleost CA is
absent/short with a single pair of valve.
Bulbus Arteriosus: Ventral aorta in contact with
conus becomes enlarged with thick elastic muscular
wall- bulbous arteriosus, no valve present
Accessory chambers: SV,CA
True chambers: A, V

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• Sinus Venosus
• Auricle
• Ventricle
• Conus Arteriosus
• Sinus Venosus
• Auricle
• Ventricle
• Bulbus Arteriosus
• Sinus Venosus
• Auricle
• Ventricle
• Bulbus Arteriosus
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8. DIPNOI FISH:
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• Sinus Venosus is present.
• Heart consists of the following
chambers:
1. Right Auricle and Left Auricle
separated by incomplete interauricular
septum having Foramen ovale.
2. Right Ventricle and Left Ventricle
separated by a partial interventricular
septum
• transitional 3-chambered heart
Ex: Lungfish
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URODELE AMPHIBIA:
1. Right Auricle
2. Left Auricle
3. Ventricle
Ex: Tailed amphibia
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• Sinus Venosus is present receiving
blood from systemic circulation.
• Conus arteriosus is reduced, replaced
by bulbous arteriosus.
•Left and right auricle separated by
incomplete interauricular septum
(Foramen ovale present).
•Ventricle single.
•NO interventricular septum
• Consisting of following three
chambers :

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ANURAN AMPHIBIA:
1. Right Auricle
2. Left Auricle
3. Ventricle
Ex: Tailless amphibia
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• Sinus Venosus opens into RA dorsally.
• The conus arteriosus divides into systemic
and pulmonary vessels by a spiral valve.
• Left and right auricle separated by
complete interauricular septum (Foramen
ovale absent).
• Ventricle single, thick muscular walled,
internally forms trabaculae permitting little
mixing of two bloods.
• NO interventricular septum
• Consisting of following
chambers :
Spiral valve

11. SQAMATAN REPTILE:
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1. Right Auricle
2. Left Auricle
3. Right Ventricle
4. Left Ventricle
• Sinus venosus is prominent ,large in turtles and
small in snakes and lizards
•Complete interauricular septum
•Incomplete interventricular septum
• Conus arteriosus and ventral aorta splits in adult
into 3 distinct trunks: pulmonary trunk and right and
left systemic (aortic) trunks.
Ex: Turtle
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• Consisting of following
chambers :

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CROCODILIAN REPTILE:
1. Right Auricle
2. Left Auricle
3. Right Ventricle
4. Left Ventricle
Ex: Crocodile
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• Sinus venosus is distinct internally
•Complete interauricular septum
•Complete interventricular septum
• Conus arteriosus and ventral aorta splits in adult
into 3 distinct trunks: pulmonary trunk and right and
left systemic (aortic) trunks.
• Foramen of Panizza connects the two aortic trunks
at the base providing maxium usage of oxygen during
diving.
• Consisting of following four
chambers :

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BIRD and MAMMAL:
• Sinus Venosus absent–incorporated
into RA
• Complete interauricular septum
• Complete interventricular septum
1. Pulmonary Circulation
2. Systemic circulation
DOUBLE CIRCULATION
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1. Right Auricle
2. Left Auricle
3. Right Ventricle
4. Left Ventricle
• Consisting of following four
chambers :
Precaval
veins
Postcaval
vein
Pulmonary
veins