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Class 10, Science, Chapter-5, Lecture-5, Circulation (Notes)

Components of the transport system in human beings: 

  1. The heart: Pumps oxygenated blood throughout the body. 
    Receives deoxygenated blood from the various body parts and sends this to the lungs for oxygenation.
  2. Blood: Helps in the transport of oxygen, Nutrients, CO2 and nitrogenous wastes.
  3. Blood vessels: 
    (i) Arteries- Carry blood either away from the heart to various organs. 
    (ii) Capillaries- Facilitates exchange of oxygen CO2 between the blood and the cells. 
    (iii) Veins - Bring blood from various organs back to the heart

DEFINITION OF BLOOD:

Blood is a connective tissue which helps in transportation of various material and gases in animals.

COMPOSITION OF BLOOD:

Blood consists of –

  1. Red Blood Corpuscle (RBC) contains HAEMOGLOBIN , does not contain Nucleus
  2. White Blood Corpuscle (WBC) contains Nucleus
  3. Blood Platelet does not contain Nucleus
  4. Plasma is colourless and contains water and proteins

WBC Are Called “Soldiers” of Body:

Reason:

WBC manufactures antibodies which maintain immunity and protects the body from infections by destroying foreign materials which enter our body.
Therefore, white blood cells are called “soldiers” of body.

STRUCTURE OF HUMAN HEART:

Human heart is four chambered –
Upper two chambers are called ATRIA (Auricles)
Lower two chambers are called VENTRICLES

AORTA originates from Left Ventricle
PULMONARY ARTERY originates from Right Ventricle.

VENA CAVA opens in the Right Auricle
PULMONARY VEIN opens in the Left Auricle

Left part and right part are separated by SEPTUM

BICUSPID VALVES are present between left auricle and left ventricle
TRICUSPID VALVES are present between right auricle and right ventricle.
SEMILUNAR VALVES are present at the beginning of Aorta and Pulmonary Artery.

MECHANISM OF BLOOD CIRCULATION SYSTEM:

  1. The muscles of all four chambers of the heart relax and
    Pulmonary vein from lungs pour oxygenated blood into left atrium
    Vena cava pours deoxygenated blood into right atrium.
  2. The atria contract and – Oxygenated blood from left atrium goes into left ventricles
    Deoxygenated blood from right atrium goes into right ventricle.
  3. The ventricles contract and – Oxygenated blood from left ventricle goes into aorta and to all parts of body.
    Deoxygenated blood from right ventricle goes into pulmonary artery and to the lungs.
  4. The oxygen rich blood from aorta goes to different parts through capillaries and supplies oxygen and receives carbon dioxide from cells and is recollected in veins and goes to vena cava and finally to the right atrium.
  5. The deoxygenated blood from pulmonary artery goes to lungs and loses CO2 , receives O2 and is recollected in veins and goes to pulmonary veins and finally to the left atrium

DIFFERENCES BETWEEN:

Artery

Vein

Capillary

1. Have thick walls

1. Have thin walls

1. Have very thin walls

2. Carry blood from heart to different organs.

2. Carry blood from organs to heart

2. Carry blood from artery to vein

3. Do not have valves

3. Have valves

3. Are extremely narrow and do not have valves.

4. Carry oxygenated blood (except pulmonary artery)

4. Carry deoxygenated blood (except pulmonary vein)

4. Exchange of food, gases and waste takes place.

DOUBLE CIRCULATION:

The circulatory system in which the blood flows through the heart twice to complete one cycle is termed as the ‘double circulation’.

Blood Circulation in Human Beings Is Called Double Circulation.

Reason:

The oxygenated blood from heart goes to all parts of body through aorta, absorbs CO2 and comes in to the heart through vena cava.
The deoxygenated blood from heart goes to lungs through pulmonary artery, absorbs oxygen and comes in to the heart through pulmonary vein.

Thus, the blood passes through the heart twice for completing one cycle.
Therefore, blood circulation in human beings is called “Double Circulation”.

FORMATION OF LYMPH: 

Through the pores present in the walls of capillaries, some amount of plasma, proteins and nitrogenous substances escape into intercellular spaces in the tissues to form the tissue fluid called LYMPH. 
From intercellular spaces, it enters lymphatic capillaries, which join to form lymph vessels, which open into subclavian vein. Lymph carries digested and absorbed fat from intestine and drains excess fluid from extra cellular space back into blood.

ROLE OF LYMPH:

  1. It returns proteins and fluid from circulation to tissues.
  2. Lymph also carries digested fat.
  3. Lymphocytes present in the lymph fight against infection.

It is necessary to separate oxygenated and deoxygenated blood in mammals and birds.

Reason: 

Birds and mammals are warm blooded animals and maintain constant body temperature which require more energy.
To obtain energy, they respire, and a large amount of CO2 is produced.
Mixing of deoxygenated blood with oxygenated one will reduce Oxygen carrying capacity of the blood.
Separation of oxygenated and de-oxygenated blood makes their circulatory system more efficient and helps in maintaining constant body temperature.