SELINA Solutions for Class 10 Biology Chapter 8 - The Circulatory System

(a) Circulatory system: The circulatory system is responsible for transport of various substances in human beings and is composed of the heart, arteries, veins and blood capillaries.

(b) Blood: Blood is the circulating fluid contained in the heart and in the blood vessels such as arteries, veins and capillaries of the circulatory system.

(c) Heart: Heart is the muscular pumping organ which pushes the blood around the body and has different chambers such as right atrium, left atrium, right ventricle, left ventricle to prevent the mixing of oxygenated blood and carbon dioxide rich blood.

(d) Diapedesis: Diapedesis is the squeezing of leucocytes through the wall of capillaries into the tissues.

(e) Phagocytosis: Phagocytosis is the process in which most WBCs and particularly the neutrophils engulf particle-like solid substances, especially bacteria.

(f) Rh factor: Rh factor is an inherited antigen often found on the blood cells. Some individuals have these antigens and are thus Rh positive (Rh+) while others who do not have this antigen are Rh negative (Rh-)

(a) Differences between systole and diastole:

(b) Differences between arteriole and venule:

(c) Differences between universal donor and universal recipient:

(d) Differences between arteries and veins:

(e) Differences between haemoglobin and chlorophyll:

(a) The left ventricle pumps blood to the farthest points in the body such as the feet, the toes and the brain against the gravity while the right ventricle pumps the blood only up to the lungs. Therefore, the left ventricle has thicker walls than the right ventricle.

(b) The right ventricle pumps blood to the lungs for oxygenation whereas the right auricle receives the blood from vena cavae and passes it to the right ventricle. Therefore, walls of the right ventricle are thicker than those of the right auricle.

(c) The mechanism of blood clotting involves the presence of calcium and other clotting factors. Thrombokinase activates an enzyme called prothrombin activator. The enzyme prothrombin activator then converts plasma protein prothrombin into thrombin. Thrombin is the enzyme which in turn converts fibrinogen into fibrin. Polymerized fibrin together with platelets forms a clot at the wound site. The prothrombin is a plasma protein synthesized in the liver. Vitamin K is essential for the synthesis of prothrombin. Hence, Vitamin K is essential for the process of blood clotting. 

(a) Tonsils: Tonsils are lymph glands located on the sides of the neck. They tend to localize the infection and prevent it from spreading it in the body as a whole.

(b) Spleen: The spleen is a large lymphatic organ. The spleen acts as a blood reservoir in case of emergency such as haemorrhage, stress or poisoning. It produces lymphocytes and destroys worn out RBCs.

(c) Hepatic portal vein: The hepatic portal vein is a blood vessel that carries blood from the gastrointestinal tract, gallbladder, pancreas and spleen to the liver. This blood contains nutrients and toxins extracted from digested contents.

(d) Basophils: They are a type of granular WBCs which release chemicals called histamine for inflammation which dilate blood vessels.

(e) S.A.N.: The sinoatrial node is a group of cells located in the wall of the right atrium of the heart. The action potential required for the rhythmic contractile activity of the heart is generated at the SA node. When the impulse is initiated, it results in the atrial systole.

Double circulation is a process during which blood passes twice through the heart during one complete cycle. The flow of blood in the heart consists of two phases-

1. The short pulmonary (lung) circulation

2. The long systemic (general body) circulation

Difference between pulmonary and systemic circulation:

(a) lymphocytes and monocytes

(b) chest pain due to inadequate supply of oxygen to the heart muscle

(d) destroy pathogens

(a) closure of tricuspid and bicuspid valves

(b) rushing of blood through valves producing turbulence

(c) closure of atrioventricular and semilunar valves

(a) Blood platelets and blood coagulation

(b) Neutrophils and phagocytosis

(c) Erythrocytes and transportation of gases

(d) Lymphocytes and Produce antibodies

(e) Bone marrow and destruction of old and weak RBC's/production of RBCs and WBCs.

(a) The blood vessel that begins and ends in capillaries is the hepatic portal vein.

(b) A blood vessel which has small lumen and thick wall is artery.

(c) The valve which prevents the back flow of blood in the veins and lymph vessels is semilunar valve.

(d) An anticoagulant present in the blood is heparin.

A matured mammalian erythrocyte lacks a nucleus and mitochondria. The lack of a nucleus increases the surface area-volume ratio of RBCs, thus increasing the area for oxygen absorption. Also, the lack of a nucleus reduces the size of the cell, making it easy to flow through the blood vessels and more cells can be accommodated in a small area.

The lack of mitochondria implies that the cell does not use any oxygen absorbed for respiration, thus increasing the efficiency of the cell to transport oxygen as all the oxygen absorbed is transported without any loss.

(a) Differences between antibodies and antibiotics based on their source:

(b) Differences between serum and vaccine based on their composition:

(c) Differences between erythrocytes and leucocytes based on their function:

(d) Differences between tricuspid valve and bicuspid valve based on their location:

People have a common belief that the heart is located on the left side of the chest because the narrow end of the roughly triangular heart is pointed to the left side and during its working the contraction of the heart is more powerful on the left side which can be felt.

The functions of blood plasma are:

(a) Transports of digested food from the alimentary canal to tissues.

(b) Transports excretory materials from tissues to excretory organs.

(c) Distributes hormones from the glands to their target site.

(d) Distributes heat in the body to maintain the body temperature.

Blood clotting or coagulation occurs in a series of the following steps:

(a) The injured tissue cells and the platelets disintegrate at the site of wound to release thromboplastin.

(b) The thromboplastin with the help of calcium ions converts inactive prothrombin into active thrombin.

(c) Thrombin in the presence of calcium ions converts soluble fibrinogen into insoluble fibrin which forms a mesh or network at the site of wound.

(d) The blood cells trapped in this network shrink and squeeze out the plasma to leave behind a solid mass known as the clot.

The functions of the blood are:

(a) Transport of digested food from the alimentary canal to tissues. These substances are simple sugars like glucose, amino acids, vitamins, mineral salts, etc.

(b) Transport of oxygen in the form of an unstable compound 'oxyhaemoglobin' from the lungs to the tissues.

(c) Transport of carbon dioxide from the tissues to the lungs.

(d) Transport of excretory materials from the tissues to the liver, kidney or the skin for elimination.

(e) Distribution of hormones from glands to the target sites.

(f) Distribution of heat to keep the body temperature uniform.

(Any five)

Blood flows twice in the heart before it completes one full cycle. This process of blood circulation in the human body is called double circulation.

The expansion or relaxation phase of the atria is called a diastole.

(a) 1 → Red Blood Cell (RBC),

2 → White Blood Cell (WBC),

3 → Blood Platelet

4 → Blood Plasma.

(b) The red blood cells are minute biconcave disc-like structures whereas the white blood cells are amoeboid.

(c) Function of part 1 (RBC): Transport of respiratory gases to the tissues and from the tissues, transport of nutrients from the alimentary canal to the tissues.

Function of part 2 (WBC): WBCs play major role in defense mechanism and immunity of the body.

Function of part 3 (Blood Platelet): Blood platelets are the initiator of blood clotting.

(d) The average life span of a red blood cell (RBC) is about 120 days.

(e) Thromboplastin

(a) The structure 3 represents the heart. It forms the centre of double circulation and is located between the liver and the head (as per the diagram). Also the blood circulation (indicated by 1) begins from heart to lungs.

(b)

(a) Tissue Fluid

(b) Red blood cells

(c) Lymph

(d) The lymph supplies nutrition and oxygen to those parts where blood cannot reach. The lymph drains away excess tissue fluids and metabolites and returns proteins to the blood from tissue spaces.

(a) A- Artery, B-Vein, C-Capillary

(b) 1 - External layer made of connective tissue

2 - Lumen

3 - Middle layer of smooth muscles and elastic fibres

4 - Endothelium

(c) An artery has thick muscular walls and a narrow lumen. It does not have any valve. A vein on the other hand has thin muscular walls and a wider lumen. It has valves to prevent backflow of blood.

(d) A (Artery)- Oxygenated blood, B (Vein)- Deoxygenated blood

(e) At the capillary level the actual exchange of gases takes place.

(a) Atrial Diastole and Ventricular Systole

(b) Ventricular muscles are contracting during this phase because the valves between the two ventricles and pulmonary artery and aorta are open while the atrio-ventricular valves are closed.

(c)

a.  1 - Red blood cell

b. Diapedesis

c.  

d. The process which occurs in B and C is phagocytosis. In this process, the WBCs engulf the foreign particles and destroy them, thus preventing the occurrence of disease.

a.  

1 - Arteriole

2 - Artery

3 - Venule

4 - Capillaries

5 - Vein

b. Such an arrangement can be observed in the lungs.