AQA AS Biology Chapter 5.1 - HEART STRUCTURE

Revision notes on chapter 5.1 of the AQA AS Biology textbook concerning the structure of the heart.

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Chapter 5.1 ­ The Structure of the Heart ­ Notes
Structure of the Human Heart:
Two separate pumps, side by side. The left pump deals with oxygenated blood from
the lungs. The right pump deals with deoxygenated blood from the body. Each pump
has two chambers:
The atrium is thin-walled and elasticated as it stretches when it collects blood.
It only has to pump blood a short distance to the ventricle, so has a thin
muscular wall.
The ventricle has a much thicker muscular wall as it has to pump blood to
either the lungs or the rest of the body.
Because the right ventricle pumps blood to the lungs, a short distance, it has a
thinner muscular wall than the left ventricle, which needs more pressure to pump
blood to the rest of the body. Although the pumps are separate, they both work at
the same time ­ both atria contract together, and both ventricles contract together.
Between each atrium and ventricle are valves to prevent backflow of blood into the
atria as the ventricles contract. There are two sets of valves, the left atrioventricular
valves (bicuspid) formed by two cup-shaped flaps on the left side of the heart, and
the right atrioventricular valves (tricuspid) formed by three cup-shaped flaps on the
right side of the heart. Each of the four chambers is served by large blood vessels
that carry blood towards or away from the heart. The ventricles pump blood away
from the heart, into the arteries. The atria receive blood from the veins.
Vessels connecting the heart to the lungs are called pulmonary vessels. There
are four vessels in the heart. The aorta is connected to the left ventricle and carries
oxygenated blood to all parts of the body except the lungs. The vena cava is
connected to the right atrium and brings deoxygenated blood back from the body's
tissues. The pulmonary artery is connected to the right ventricle and carries
deoxygenated blood to the lungs, where its oxygen is replenished and its carbon
dioxide is removed. The pulmonary vein is connected to the left atrium and brings
oxygenated blood back from the lungs.
Supplying the Heart Muscle with Oxygen:
Although oxygenated blood passes through the left side of the heart, the heart
doesn't use this oxygen for its respiratory needs. Instead, the heart muscle is
supplied by its own blood vessels, called the coronary arteries, which branch from the
aorta after it leaves the heart. Blockage of these arteries (for example by a blood
clot) leads to myocardial infarction, or heart attack, as an area of the heart muscle is
deprived of oxygen and dies.


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