Heart of Birds (Pigeon) - Structure, Function, Diagram & MCQs

December 22, 2025

Heart of Birds (Pigeon) - Structure, Function, Diagram & MCQs

Heart of Birds ( Pigeon) - Anatomy, Physiology with Diagrams

To support the intense demand for Oxygen and nutrients needed for flight, birds have developed the largest hearts related to the body mass of all vertebrates.

Only a true four chambered heart is efficient enough to satisfy the metabolic oxygen demand produced by homoiothermy/ homeothermy ( constant body temperature independent of external environment).

Flapping of wing for flight may be the most strenuous activity other than running, swimming and climbing, in which an vertebrate engage.

This makes the circulatory system of birds more energy consuming system.

Labelled Diagram of Heart of pigeon (bird) in dorsal and ventral view

Pigeon heart in dorsal (A) and ventral (B) view.

The four chamber avian heart is similar, in most of the structural details to that of mammalian heart.

The avian heart pumps blood more efficiently and is proportionately 40% larger than mammalian heart and moves comparatively more blood per beat (Lasiewski and Calder 1971).

( Exception: In birds- the aortic arch bends to the right. In mammals- to the left and is also smaller.
The sinus venous or a conus arteriosus is absent . It is said to be incorporated into the right auricle.)

The birds show advancement then their ancestors reptiles, in having a completely four chamber heart with two atria or auricles and two ventricles, as in mammal.

( The heart rate ranges around 600 beats per minute during flight for pigeon and is less in rest.)

Anatomy

External Features of Bird heart

The Avian heart is much similar to that of mammals but it is comparatively larger than in other vertebrates. The most distinctive feature is that of the rightward orientation of the aortic arch.

The heart lies in the thoracic cavity, mid-ventrally, ventral to oesophagus and partially surrounded by lobes of the liver.
It is reddish, conical with apex directed backwards with a broad base.
It is enclosed in a thin transparent membranous sack called the pericardium with outer parietal layer and inner visceral layer.
In between these two layers is the pericardial cavity filled with watery serous pericardial fluid.
This fluid protects the heart from shocks and injuries and permits a movement during beating.
The anterior two auricles ( right and left) are darker, smaller and thin walled, faintly separated by inter-auricilar groove.
The posterior ventricles (right and left) are comparatively lighter, bigger and thick-walled. They are separated from the auricles by hollow transverse groove called coronary sulcus or auricula-ventricular groove.
Most of the apex of the heart is composed of the muscular walls of the left ventricle. The right ventricle is much smaller and less muscular than the left ventricle.
The coronary arteries are visible on the dorsal inventor surface of the ventricles.

Internal Structure of Bird Heart

Labelled Diagram of Internal structure of pigeons heart in ventral dissection

Internal Structure of Heart of Bird (pigeon) in ventral dissection

The internal structure of the Avian heart is almost similar to that of mammalian heart, four- chambered that seperate the circulation of oxygenated and deoxygenated blood, with the prominent exception of the right oriented aortic arch.

1. Chambers

The avian (pigeon) heart is divided into four distinct chambers, just like the mammals, ensuring a double circulatory system.

Right Atrium or Auricle
Left Atrium or Auricle
Right Ventricle
Left Ventricle

Atrium or auricle

Internally, a thin membranous partition called inter-auricular septum separates the two comparatively thin walled auricles.

In the middle, there is a small oval area called fossa ovalis (representing position of the foramen ovale in the embryo).

Right Auricle:

Blood from the anterior and posterior body flows into the right auricle via the precaval and postcaval veins.

The right auricle is larger and receives three large caval veins in the dorsal wall, i.e.

the large,

Left precaval
Right precaval, and
Postcaval whose opening is guarded by muscular eustachian valve.

The right auricle opens into the right ventricle via a crescentic aperture called right auriculo-ventricular aperture with a pair of strong muscular flaps, without chordae tendineae, forming the right auriculo-ventricular valve (just like the tricuspid valve in mammals)

Left Auricle:

The Left auricle is smaller and recieves four pulmonary veins from lungs.

It opens into the left ventricle by a circular left auriculo-ventricular aperture guarded by two membranous flaps forming left auricula-ventricular valve. These flaps, via two chorda tendineae are attached to the thick papillary muscles arising from wall of the left ventricle.

( This valve is corresponds to the bicuspid or mitral valve in mammals)

Ventricles:

The two ventricles are also completely seperated by a thick muscular inter-ventricular septum.

Right Ventricle:

The right ventricle is less muscular than the left, although the volume may equal, such that the blood flowing from the right ventricle into the pulmonary arteries does not damage the lungs, if in high pressure.

Left Ventricle:

The left ventricle has thicker walls and most muscular chamber which is partially surrounded by right ventricle having thinner walls.

From the left Ventricle arises the only right systemic or aortic arch, continuing with dorsal aorta. The opening of the arch is guarded by three semilunar valves.

( The left systemic arch is absent in birds but are present in frog and lizard)

In T.S., right ventricle appears crescentic, while the left appears circular.

Muscles called trabeculae or columnar carnea traverse the cavities of the ventricles.

Valves:

1. Right Atrioventricular or auriculo-ventricular valve (A-V valve):

Location: Between right atrium and right ventricle.

Structure:

Thick, muscular.

Function:

Prevention of backflow of the deoxygenated blood from right ventricle to right atrium during ventricular systole (contraction).

2. Left Atrioventricular Valve (A-V valve):

Location:

Between left atrium and left ventricle.

Structure:

They are pocket-like valves ( two cusps usually) .

Function:

Prevention of backflow of oxygenated blood from left ventricle to left auricle during ventricular systole.

3. Semilunar Valves:

Location:

At the opening of large arteries i.e. pulmonary artery ( exiting the right ventricle) and right systemic arch (exiting the left ventricle).

Structure:

They are pocket-like valves (three cusps usually).

Function:

Prevention of backflow of blood from the major arteries back into the ventricles during ventricular relaxation (diastole).

Physiology

The heart works as pump to force the blood to all parts of the body.

The birds show complete double circulation of blood as in mammals.

The right half of the heart receives and gives only venous blood and the left heart, only the arterial blood.

The double circulation involves pulmonary (lung) circulation and systemic(body) circulation.

Pulmonary (lung) circulation:

The venous blood is pumped by the right ventricle into the pulmonary aorta which divides into the right and left pulmonary arteries going to right and left lungs, respectively. From here this oxygenated blood is returned to left auricle via four pulmonary veins.

Systemic (body) circulation:

Via the pulmonary circulation, oxygenated blood from lungs is returned to the left auricles by 4 pulmonary veins. From here, through the left auriculo-ventricular valve it reaches the left ventricle. Next via aorta into smaller arteries and then via capillaries to tissues of the body to nourish them.

The capillaries unite to form veins, which finally form the three main vena cevae to return impure deoxygenated blood to the right auricle. From here to right ventricle via right auriculo-ventricular valve, where the pulmonary circulation begins.

Question:

Differentiate between atria and ventricles in bird heart.

Answer:

There are few clear structural and functional points of differentiation between atria and ventricles. which are,

Position and shape:

Atria:

The two upper chambers, usually smaller, thin walled, forming the base of heart.

Ventricles:

The two lower chambers, larger and more muscular, forming the pointed apex region of the heart.

Wall thickness and muscle:

Atria:

Thinner walls as they only have to receive the blood and push it to the ventricles which is at short distance.

Ventricules:

Thicker and muscular specially the left ventricle, which is 2-3 times thicker than the right to pump blood to the whole body.

Valves and blood flow direction

Atria:

Atria are located above the atrio-ventricular valve (Av valves) and are entry chambers i.e. right atrium receives deoxygenated blood and left atrium receives oxygenated blood.

Ventricles:

Ventricles lie below the AV valve and connect to outflow tracts: right ventricle to pulmonary artery (lungs), left ventricle to systemic aorta (body).

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Heart of Birds (Pigeon) - Structure, Function, Diagram & MCQs

Heart of Birds ( Pigeon) - Anatomy, Physiology with Diagrams

Anatomy

External Features of Bird heart

Internal Structure of Bird Heart

Physiology

Pulmonary (lung) circulation:

Systemic (body) circulation:

Differentiate between atria and ventricles in bird heart.

Position and shape:

Wall thickness and muscle:

Valves and blood flow direction

Related short questions and MCQs.

Short Questions

Multiple Choice Questions (MCQs):

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