Class 8 SELINA Solutions Biology Chapter 6: The Circulatory System

(iii) Pulmonary vein

(i) RA ® RV ® Pulmonary arteries ® Lungs ® Pulmonary veins ® LA

(a) Septum

(b) SA node (Sinoatrial Node)

(c) Karl Landsteiner

(a) Three components of circulatory system:

1.      Heart

2.      Blood vessels

3.      Blood

(b) Four blood groups on the basis of antigens:

1.      A (A antigen)

2.      B (B antigen)

3.      AB (A and B antigens)

4.      (No antigens)

(c) Two phases of double circulation:

1.      Systemic circulation

2.      Pulmonary circulation

(d) Three principal fluids of human body:

1.      Blood

2.      Lymph

3.      Tissue fluid

(e) Three kinds of blood vessels:

1.      Arteries

2.      Veins

3.      Capillaries

(f) Two types of blood circulation in the human body:

1.      Pulmonary circulation

2.      Systemic circulation

(a) Circulatory system: The circulatory system comprises of the heart, blood and blood vessels which circulate blood throughout the body, thereby helping in the transport of nutrients, oxygen, and carbon dioxide.

(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) Lymph: Lymph is the fluid contained within the lymph vessels and lymphatic organs. It is also a part of the immune system, and its main function is defence against germs.

(d) Artificial pacemaker: Artificial pacemaker is a mechanical device which is placed surgically in humans if their SA node is damaged or if the electrical conduction system of the heart has problems.

The blood gets oxygenated in the lungs.

The left side of the heart contains oxygenated blood.

(a) Pericardial fluid: Pericardial fluid protects the heart from shocks, jerks, or any mechanical stress.

(b) Aorta: Aorta carries oxygenated blood from the heart to all parts of the body through its branches.

(c) Vena cavae: The two vena cavae veins (superior vena cava and inferior vena cava) bring deoxygenated blood from the different parts of the body to the right auricle of the heart.

Functions of lymph:

1.      Drainage — The lymph drains away excess tissue fluid and metabolites and returns proteins to the blood from tissue spaces.

2.      Absorption — Fats in the intestine are absorbed through lymph vessels (or lymphatics).

3.      Defence — Lymphocytes and monocytes of the lymph function to defend the body. The lymphatics also remove bacteria from the tissues.

4.      Nutritive: The lymph supplies nutrition and oxygen to those parts of the body where blood cannot reach.

(a) Differences between pulmonary artery and pulmonary vein (kind of blood):

(b) Differences between artery and vein (direction of blood flow):

(c) Differences between closed and open vascular system (definition):

(d) Differences between bicuspid and tricuspid valve (location):

(e) Differences between blood and lymph (composition):

The four common heart related conditions in humans along with their causes and symptoms are stated below:

1. Palpitations — When the heart beats too hard or too fast or sometimes even skips a beat, it is called a palpitation. Palpitations are often caused due to stress or anxiety. Sometimes, certain types of food may also cause palpitations.
2. Hypertension — This is a condition which occurs when blood flows through the blood vessels with a force greater than normal. This is also called high blood pressure. Hypertension can also strain the heart, damage blood vessels, and increase the risk of a heart attack or stroke.
3. Heart attack — A heart attack is a sudden interruption of blood supply to the heart. It usually occurs due to a blood clot that prevents the flow of oxygen-rich blood to the cardiac muscle. As a result, a part of the cardiac muscle dies and causes permanent damage to the heart. Some common symptoms of a heart attack include uncomfortable pressure, tightness or squeezing pain in the centre of the chest, discomfort or pain spreading beyond the chest to the shoulders, neck, jaw, teeth or one or both arms, shortness of breath, dizziness, sweating and nausea.
4. Cardiac arrest — A cardiac arrest occurs when the heart suddenly stops pumping blood around the body. In cardiac arrest, a person suddenly loses consciousness and stops breathing or may have abnormal breathing. Some people experience chest pain, shortness of breath, or nausea before a cardiac arrest occurs. The common cause of cardiac arrest is coronary artery disease wherein the walls of the arteries thicken as a result of fat or plaque deposition. Less common causes include major blood loss, lack of oxygen, low potassium levels, heart failure and intense physical exercise.

(a) Universal donor: The blood of O group can be given to all the blood groups. Hence, a person with O blood group is called a universal donor.

(b) Universal recipient: The blood of AB group can only be given to AB group, but a person with AB type of blood can receive blood from all blood types and is therefore called a universal recipient.

The process of giving blood from outside to a patient during surgical operations or during accidents to save his life is known as blood transfusion.

The following precautions are to be observed for blood transfusion:

• Check the compatibility of the donor's blood group with that of the recipient.
• Ensure clinically that the blood of the donor is free from any infections.
• Check for the donor's hemoglobin level.

The parts marked 1 to 6 are labelled below:

1 ® Left pulmonary artery

2 ® Superior vena cava

3 ® Left pulmonary vein

4 ® Right auricle

5 ® Left ventricle

6 ® Right ventricle

(a) Deoxygenated blood is carried by the blood vessel marked 2 (superior vena cava).

(b) Aorta

(c) Right auricle