SS1 Animal Husbandry Lesson Note on The Heart

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TOPIC: THE HEART

The heart is the most powerful organ in the circulatory system. It helps to pump blood round the body. Each pumping action is called Heartbeat.

Sub Topic 1

The Heartbeat

The heart is made up of muscles called the cardiac muscles which contract and relax continuously, making the heart to beat ceaselessly. It is covered by a thick membrane called, pericardium which keeps the heart in a good position in the thoracic cavity.

The heart consists of four chambers upper auricle (right and left auricle) the lower ventricles (right ventricle and left ventricles). A central wall called the septum divides the heart into the right and left halves.

Between the left auricle and the left ventricle is an aperture guarded by a bicuspid/mitral valve and another valve, the tricuspid valve is found between the right auricle and the right ventricles. These valves only permit one direct flow of blood.

Heartbeat occurs in two stages.

• Diastole
• Systole

Diastole:-

The two auricles contract, creating high pressure in the blood which causes bicuspid and tricuspid valves to fold downward thus allowing blood to flow from the auricles into the ventricles. Deoxygenated blood enters the right ventricles from the right auricle while oxygenated blood enters the left ventricle from the left auricle.

Systole:-

The ventricles contract, creating high pressure in the blood which causes the two valves to close. Deoxygenated blood from the right ventricle passes into the pulmonary artery while oxygenated blood from the left ventricle passes into the aorta.

Aorta is the largest blood vessel in the body.

Sub Topic 2

THE BLOOD VESSEL

Blood vessels are networks of paths/space in the body through which materials are moved from one part of the body to the other with the aid of blood.

Three Types of Blood Vessels

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