Question

Describe the circulatory system in humans.​

Answer 1

• Explanation:

circulatory system :

circulatory system consists of heart, blood and blood vessels

blood and blood vessels :

when the oxygen we breathe in through the nose passes into the lungs and then into the blood the circulatory system starts its work blood is a red coloured fluid which carries oxygen and nutrients and waste products and moves through tubes called blood vessels .

there are three types of blood vessels

.arteries

.veins

.capillaries

arteries:

these carry blood from the heart to other parts of the body

veins:

these carry blood from other parts of the body back to the heart

capillaries :

these are very fine branches of arteries that join together to from veins

heart:

heart is like a pump the left side of our heart receive blood from our lungs and pumps it to all parts of the body through the blood vessels and the right side of our heart receives blood from the rest of the body and bumps it back to the lungs

the blood flowing from our lungs to the heart is full of oxygen our heart pumps this Oxygen and rich blood along with oxygen rich blood along with nutrients and water to the cells in different parts of the body these cells pass carbon dioxide and other waste back to the blood this blood carrying carbon dioxide and waste goes back to the heart through the veins the heart sends back to the lungs from where the carbon dioxide is released from the body when we breathe out

see how our circulatory system works

1. when we breathe in oxygen rich air enters the blood from the lungs and is carried to the heart
2. heart pumps deoxygenated blood to other parts of the body
3. blood transports oxygen to different body parts it also collects waste and carbon dioxide through the capillaries
4. blood returns to the heart with carbon dioxide
5. heart pumps the carbon dioxide rich blood to the lungs where carbon dioxide is removed and more oxygen is taken

Answer 2

Human circulatory system consists of heart, blood vessels and blood.

Human Heart:

 Protected by double layered membrane called pericardium, enclosing pericardial fluid.

 Heart wall consists of three layers:

• Epicardium is an outermost layer of connective tissue.

• Myocardium is a middle layer of heart muscle.

• Endocardium, an innermost layer, consists of simple squamous epithelium.

 Heart is four chambered: two upper chambers are called atria (singular: atrium) while two lower chambers are called ventricles.  

 A thin muscular wall called inter–atrial septum separates right and left atria whereas inter-ventricular septum separates right and left ventricles.

 The atrium and ventricle of the same side are also separated by a thick fibrous tissue called atrio– ventricular septum.

 Ventricles have thicker muscular wall. The left ventricle has the thickest myocardium as it has to pump blood forcefully to all body parts.

 Ventricular walls have well developed network of ridges called papillary muscles or musculi papillares.

 Chordae tendinae are white elastic threads extending from atrio–ventricular valves to papillary muscles. These elastic threads prevent opening of A–V valves into atria and hence backflow of blood from ventricles to atria during ventricular contraction.

Valves and Major Blood vessels:

 Opening of right atrium into right ventricle is guarded by tricuspid valve.

 Opening of left atrium into left ventricle is guarded by bicuspid or mitral valve.

 Right atrium receives blood from vena cavae (great veins) whereas left atrium receives blood from four pulmonary veins (two from each lung).  

  Right atrium receives blood from three major veins:

• Superior vena cava (Pre caval) collects deoxygenated blood from upper body parts. Its opening into right atrium is devoid of any valve.

• Inferior vena cava (Post caval) collects deoxygenated blood from lower body parts.  

• Coronary sinus collects blood from heart wall.  

 Pulmonary arch carries blood from right ventricle to lungs. Its opening is guarded by three semilunar valves.

Note: Pulmonary arch soon divides into two pulmonary arteries which carry blood to lungs.

 Left ventricle pours blood into aorta. Opening of aorta is guarded by semilunar valves.

Notes: Valves in heart allow flow of blood only in one direction and thus prevent backflow of blood.

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