CLASS 6TH | THE CIRCULATORY SYSTEM | REVISION NOTES

The transport system in the body is called as circulatory system.

Circulatory system in Human Begins:

The human circulatory is consist of heart, blood and blood vessels and lymphatic system.
It is also called as circulatory system.

Human Heart:

The human heart is pinkish coloured about size of fist. It is located in between two lungs in
rib cage. It has four hollow chambers with two thin walled auricles and two thick walled
ventricles. These chambers mean to prevent the mixing of pure and impure blood. There
interventricular septum which separates right and left ventricles.

1. Auricles:
   Also termed as atrium. Theses arte upper chambers of the heart with thin walls and receive
   blood from different parts of body. The right auricle revives impure blood while left auricle
   receives pure blood.
2. Ventricles:
   These are lower chambers of heart with thick walls as they have to pump the blood to outside.
   The right ventricle pumps impure blood while left ventricle pumps pure blood. The septum
   divided the heart into left and right sides.
   The Blood:
   Blood is red coloured fluid which as as connective tissue which supply nutrient as well remove
   waste from all body parts.
   Human body contain on average 5 litre of blood.
   ➢ Components of blood:
   Plasma : (60% In blood)
   It is liquid part of blood contains 90-92% of water , 7% protein 1% inorganic salts and about
   0.1%glucose and traces of other substances.
   ➢ Blood cells: (40%)
   This is cellular part of blood. There are three types of cells in human blood such as red cells,
   white blood cells and blood platelets.
   

Red Blood Cells
• Also called as erythrocytes. They are minute, biconcave circular structure, found about
5.5million/mm3
.
• They contain more haemoglobin as they get mature and loses nucleus, ribosomes and
mitochondria.
• Oxygen combines with haemoglobin to form oxyhaemoglobin and when carbon
dioxide combines with it forms carbaminohaemoglobin.
• Red cells transport whole absorbed oxygen as they lack in mitochondria.
• They are produce in long bone’s marrow and having the life span about 120 days
White Blood Cells:
• Called as leucocytes
• They are large , irregular or oval colourless nucleated structure. They are found to be
7000/mm3
in an adult.
• They are produced in red bone marrow and lymph nodes.
• Leucocytes are of two types:
(A)Granulocytes are subdivided into acidophil, Basophils and Neutrophils.
(B)Agranulocytes : without granules and contain unlobed nuclei. Divided into lymphocytes
and monocytes. Lymphocytes performed phagocytic action against infection causative
agents. They have lifespan of about two weeks.
• The lifespan of WBC’s ranges from 12 hours to 12 days
Blood platelets:
• They are termed as thrombocytes, found about 2,50,000/mm3 of blood.
• They are oval, round or rod like cytoplasmic structure with only granules.
• Blood clotting is the main function of platelets in order to prevent excessive blood loss
Blood Groups:
Karl Landsteiner discovered the blood grouping system
Blood group are distinguished on the basis of presence of antigen and antibody.
Antigens are foregn bodies which are capable of generating an immune responsein the body
where as Antibodies are proteins that are produced by the body, as they work fight against
the antigens.
Four types of blood groups: A, B , AB, O in human beings on presence or absence of antigen
and antibodies.

Blood vessels:

Blood vessels form network of tubes which carry blood away from the heart and towards
heart.

They perform transportation and divided into following:
o Arteries:
Carries oxygenated blood from heart and transported to all body tissues (Except pulmonary
artery which carries deoxygenated blood)
They have thick and muscular wall and elastic to withstand the blood pressure
Lumen of arteries is small and lack valves
Smallest artery called as arterioles.

o Ventricles:
Carries deoxygenated blood to heart (except pulmonary vein which carry oxygenated blood)
The walls of veins are thin less muscular and non-elastic. They do possess valve and blood
flows through it with little pressure.
Small veins are called as venules .
Vein collapse when empty..

o Capillaries:
They are microscopic vessels
They are terminal branches of artery and re-join to give rise to vein.
Thin layer of it, enables for exchanging nutrients oxygen and carbon dioxide along with
tissues.

Blood circulation:

• The pumping action of heart starts by initiation of heart contraction of its muscular
walls
• Alternate contraction and relaxation continues regularly
• The right auricle receives blood rich in carbon dioxide from two major veins , vein lie
in back and front of heart.
• The blood the flows from right auricle to the right ventricle and then to the lungs
through the pulmonary artery.
• The gaseous exchange in the lungs turns the deoxygenated blood to pure blood
,makes it rich in oxygen.
• This blood reaches to left auricle through the pulmonary veins. It then passes to the
left ventricles
• From the left ventricles, the oxygenated blood is pumped into aorta , which is largest
artery in the body and is supplied to all the body parts.

Blood pressure:

The pressure exerted on wall of blood vessels is called as blood pressure.
▪ Upper limit of blood pressure is called systolic pressure , which ranges from
100-140 mm of Hg
▪ Lower limit of blood pressure called as diastolic pressure, which ranges from
60-80 mm of Hg
When person having more than 140 mm systolic and 90mm diastolic is consider to be
suffering from Hypertension or high blood pressure.
Blood pressure is measured by Sphygmomanometer.
The Heart Beat:
The contraction of auricle and ventricles produce a sound called as Heart-beat
The sequence of events taking place during one complete heartbeat is known as cardiac cycle.
The contraction phase is systole followed by relaxation phase is diastole.
Heart beat last for 0.85 seconds.
During each heartbeat, two sounds are produced. The contraction of auricles produces weak
sound which is followed by string sound produced by contraction of ventricles.
Heartbeat can by listen by stethoscope.

Pulse:

The rhythmic beating of the arteries due to beating of the heart is called pulse.
This rhythm or simply wave can be felt anf counted in the superfacial and radial arteries near
wrist. This count represent the count of heart beat.