Body Fluids and Circulation Class 11 Biology Notes and Questions

Notes Class 11 Revision Notes

Please refer to Body Fluids and Circulation Class 11 Biology notes and questions with solutions below. These revision notes and important examination questions have been prepared based on the latest Biology books for Class 11. You can go through the questions and solutions below which will help you to get better marks in your examinations.

Class 11 Biology Body Fluids and Circulation Notes and Questions

PointsTo Remember

Blood : A special connective tissue that circulates in principal vascular system of man and other vertebrates consisting of fluid matrix, plasma and formed elements (Blood= Plasma+ All blood cells).

Plasma : (Blood-All blood cells =Plasma) The liquid part of blood which is straw coloured, viscous fluid and contains about 90-92% of water and 6-8% proteins.

Lymph : A clear yellowish, slightly alkaline, coagulable tissue fluid, containing white blood cells (Only lymphocytes), a liquid resembling blood plasma.

Serum : Blood plasma from which fibrinogen and other clotting factors have been removed. (Plasma- (fibrinogen & other clotting factor)= blood serum.

Heart Beat : The rhythmic contraction and relaxation of the heart, which includes one systole (contraction phase) and one diastole (relaxation phase) of the heart. Heart beat count of healthy person is 72 times per minute.

Stroke Volume : The volume of blood pumped out by the heart during a systole. If is approximately 70 ml.

Cardiac output : The amount of blood pumped by heart per minute is called cardiac or heart output. The value of cardiac output of a normal person is about 72 x 70 = 5040 mL or about 5L per minutes.

Cardiac Cycle : The rhythmic contraction and dilation of different parts of heart in one beat.

Systole : Contraction of heart muscles.

Diastole : Relaxation of heart muscle


Body Fluids and Circulation

Blood Pressure-The resistance offered by the lumen of the artery to the flow of Blood.

Hypertension : The condition when blood pressure is higher than normal (120/80 mmHg)

Electrocardiograph :(ECG) the machine used to record electrocardiogram.

Electrocardiogram ECG : The print out of pattern of heart beat taken on a graph paper from Electrocardiograph. (EGC machine)


The colourless mobile fluid connective tissue drains into the lymphatic capillaries from the intercellular spaces. It is formed by squeezing of blood through capillaries, within tissues. Its flow is unidirectional i.e., from tissues to heart.

Composition :It is composed of fluid matrix, plasma having only lymphocytes of white blood corpuscles or leucocytes.

Functions : (i) It drains excess of tissue fluid from extra cellular spaces back into the blood.
(ii) It contain lymphocytes and antibodies.
(iii) It transport digested fats.

Blood Clotting : Coagulation of Blood:

Body Fluids and Circulation

Functions of Blood

Transport, of food, respiratory gases (02 and C02), hormones, metabolic intermediates, waste products, supply of raw materials, regulation of water balance, regulation of pH and body temperature, and provides immunity.

Blood Groups :Based on presence of Antigens and Antibodies in blood.

Body Fluids and Circulation

Rh (Rhesus) Group :

Discovered by Landsteiner and Wiener in 1940 the antigen found on the surface ofRBCs. The presence of this antigen is termed as Rh-positive (Rh+) and its absence as (Rh-). It plays a crucial role in childs birth born out of a marriage between Rh- woman and Rh+ man, causing to produce anti Rh antibodies.

→SAN (Sino-artrial node) : A patch of tissues present in the right upper comer of the right atrium, acts are pacemaker due to having a unique property of self exitation.

→AVN (Atrio Ventricular Node) : A mass of tissues seen in the lower left comer of the right atrium close to the atrio-ventricular septum. Fresh wave of contraction generated here, passes over both the ventricles simultaneously along the bundle of his.

Body Fluids and Circulation

Human Heart

  • It is the mesodermally derived organ situated in thoracic cavity in between the two lungs. Protected by a double membrane covering called Pericardium.
  • Four chambers-two (left and right) atria, and two ventricels (left and right)
  • Inner-artrial septum separates the two atria and inter ventricular septum separates the two ventricles, while the atria and ventricles are separated by atrioventricular septum.
  • The valves between right atrium and right ventricle is tricuspid while between left atrium and ventricle is bicuspid or mitral value.
  • The opening of the right ventricle into the pulmonary artery and the opening of left ventricle in to aorta are guarded by semilunar values.
  • The valves allow the flow of blood only in one direction, i.e., from atria to ventricles and from ventricles to pulmonary artery or aorta.

Heart Valves

Tricuspid Valve: The valves formed of three muscular flaps or cups, which guard the opening between the right atrium and the right ventricle.

Bicuspid Valve (Mitral Valve): The valves which guard the opening between the left atrium and the left ventricle, made up of two flaps.

Semilunar Valves : The valves present at the opening of the right and the left ventricles and allow the entry of blood into pulmonary artery and the aorta respectively.

Standat·d ECG Reading of ECG : ‘P’ Wave represents the electrical excitation (or depolarisation) of the atria and leads to the contraction of both the atria.

Electrocardiogram ECG : The graphic record of the electric current produced by the excitation of the cardiac muscles. It is composed of a ‘P’ wave, ‘QRS’ wave. (complex) and ‘T’ wave (for a standard ECG)

Body Fluids and Circulation Class 11 Biology

‘QRS’ complex : represents the depolarisation of the ventricles, which initiates the ventricular contraction.

‘T’ Wave : represents the return of the ventricles from excited to normal state (repolarisation). The end ofT-wave marks the end of sytole.

Double circulation :

The passage of same blood twice through heart in order to complete one cycle. i.e. It is completed in following two steps.

(i) Pulmonary Circulation : The blood pumped by the right ventricle (deoxygenated blood) is transported through pulmonary artery to lungs where C02 is exchanged with 02 through diffusion and returns back to the heart through pulmonary vein. It is called pulmonary circulation.

(ii) Systemic Circulation : The oxygenated blood from left ventricle is transported through aorta to different body parts (cells and tissues) where 02 is exchanged with C02 through diffusion and then returned back to the heart through vena-cava. It is called systemic circulation.

Disorders of circulatory System

Hypertension (High blood Pressure) : It results from narrowing of arterial lumen and reduced elasticity of arterial walls in old age. It can cause rupturing of capillaries. It is a silent killer.

Cor·onaryArtery Disease: (CAD) Atherosclerosis. The supply of the blood to heart muscles is affected. It is “caused by deposits of Calcium, fat, cholesterol and fibrous tissues to make the lumen of arteries narrower.

Angina Pectoris : Caused due to arteriosclerosis, when no enough oxygen is reaching the heart muscle due to which the person experiences acute chest pain.

Heart attack : Caused when the heart muscle is suddenly damaged by an inadequate blood supply.

Cardiac arrest : The state in which the heart stops beating.

Arteriosclerosis : The state of hardening of arteries and arterioles due to thickening of the fibrous tissue and consequent loss of elasticity. It causes hypertension.

Body Fluids and Circulation Class 11 Biology

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