Body Fluids And Circulation Class 11 Notes Biology Chapter 18 - CBSE

Chapter : 18

What Are Body Fluids And Circulation ?

Composition of Blood

Plasma (55%)
  • 90% Water
  • 10% Solid
    • Inorganic
      • Sodium Chloride
      • Bicarbonates
      • Sodium Phosphate
      • Potassium Phosphate
      • Calcium
      • Iron
      • Magnesium
    • Organic
      • Glucose
      • Amino Acid
      • Fats
      • Urea
      • Hormones
      • Enzymes

Corpuscles (45%)

  • R.B.C.
  • W.B.C.
    • Granulocytes
      • Neutrophils
      • Eosinophils
      • Basophils
  • Platelets
    • Agranulocytes
      • Lymphocytes
      • Monocytes

Blood Groups

There are four types of blood groups in human beings. These are A, B, AB and O.

Antigen and Antibody in Different Blood Groups

Blood Group Antigen on RBC Antibody in Plasma
A A Antibody B
B B Antibody A
AB AB None
O None Antibody-A and Antibody-B

The four different blood groups in the ABO system are A, B, AB and O. A person's blood group is determined by a pair of genes - one gene inherited from each parent. Each blood group is identified by its own set of molecules (called antigens), which are located on the surface of red blood cells. When a person needs a blood transfusion, the donated blood must match the recipient's blood or complications will occur.

Blood Clotting

Ca2+ is necessary for blood clotting.

Injury in blood vessels → Platelets clump at the wound → Platelets and injured tissue cells release thrombokinase

Thrombin ← Prothrombin ← Vitamin K

Fibrin → Fibrinogen

Form clot to prevent further blood loss

RH Factor

It was discovered by Landsteiner (1940) in Rhesus monkey. The persons bearing this factor are Rh+ve and persons who do not possess this factor are Rh–ve. The Rhesus factor is an important characteristic of blood cells. It indicates whether the blood of two different people is compatible when mixed such as the blood of a mother and her baby at birth. If they have different blood group characteristics, it may cause problems.

Blood Pressure

The pressure exerted by blood on the walls of blood vessels is known as blood pressure.

  • The normal blood pressure of a man is 120/80.
  • The pulse rate of a man at rest is about 72 beats per minute.
  • The time of the cardiac cycle is 0·8 seconds.

Circulatory System

A system which transports food, water, electrolytes, enzymes, hormones, antibodies and respiratory gases to or away from the body tissues is called the circulatory system.

Main Components

Blood and lymph tissues, heart and blood vessels. (Arteries, veins, capillaries, lymphatic ducts, etc.).

Types Of Circulatory System

Two types of circulatory systems are found in animals :

Circulatory System

  • Open (Blood Circulates in large

    Circulatory System Open Spaces)

Ex.-Molluses, Arthropods

  • Closed (Blood is enclosed within tubular vessels)

Ex.-Vertebrates Human beings

William Harvey (1628) was the first who discovered the function of the heart and the circulation of blood.

Lymphatic System

Complex network of lymphatic vessels, tissues, and organs.

  • Transport lymph throughout the body.
  • Maintain the fluid balance in the body, wherein it collects excess fluid and other particulate matter from the tissues and deposits in the bloodstream.
  • Defends the body against infections with the disease-fighting cells called the lymphocytes.
  • Spleen is the largest lymphatic organ.

Blood Vessels

  • Arteries carry blood away from the heart.
  • Veins carry blood back towards the heart.
  • Capillaries, the smallest blood vessels, connect arteries and veins.

Cardiac Cycle

The cardiac cycle is a series of pressure changes that take place within the heart. These pressure changes result in the movement of blood through different chambers of the heart and the body as a whole.

Cardiac Output

Cardiac output (CO) is the amount of blood pumped by the heart per minute and is the mechanism whereby blood flows around the body, especially providing blood flow to the brain and other vital organs.

Double Circulation

A mechanism in which blood circulates twice through the heart in one complete cycle is known as double circulation. Systemic circulation and pulmonary circulation are two pathways in which the blood flows in double circulation. Double circulation is present in birds and mammals.

Regulation Of Cardiac Activity

The principal functions of the heart are regulated by the sympathetic and parasympathetic divisions of the autonomic nervous system. In general, the sympathetic nerves to the heart are facilitatory, whereas the parasympathetic (vagus) nerves are inhibitory.

ECG (Electrocardiograph)

Graphical representation of electrical activity of heart during cardiac cycle. The P-wave represents the electrical excitation of atria (depolarisation) which leads to contraction of atria. The QRS-wave represents the depolarisation of ventricles, which initiates the ventricular contraction. The T-wave represents the return of ventricle from exited to normal state (repolarization). The end of T-wave marks the end of systole. Counting the number of QRS complex in given period of time determine the heartbeat rate.


Disorders Of Circulatory System

  • Hypertension: Resting arterial pressure over a prolonged period of time.
  • Heart block: Impulses are interrupted at any point of the heart.
  • Haemorrhage: Excessive loss of blood.
  • Coronary thrombosis: It is a kind of heart attack in which the clot is formed in the coronary artery which supply blood to the heart muscles.