Process of blood circulation - Biological processes in human body

Process of blood circulation

Glucose and oxygen are the main components to produce energy in the body. Blood is the transport medium of both the above components to the cells and the waste out of the cells.

Blood corpuscles and plasma

Blood is a special connective tissue. It is a red colour fluid. When blood is centrifuged and kept aside, there will be two different layers. The dark red layer consists of blood corpuscles while the pale yellow layer contains the plasma. On this basis, blood which is seen as a homogenous fluid, contains a plasma and a suspension of corpuscles. When a slide with a blood smear observed under the microscope there will be several types of corpuscles in it.

Red Blood cells (Erythrocytes)
One cubic milimetre of human blood contain about five million of red blood cells. These red
coloured and biconcave disc-like cells are clearly visible among the other corpuscles. They form in
red bone marrow.The life span of RBC is about four months. Absence of nucleus in red blood
cells provides a large surface area to absorb more oxygen. A pigment called haemoglobin is present
in red blood cells. Haemoglobin absorbs oxygen and form oxyhaemoglobin to transport oxygen to

cells.

Red blood cells under electron microswpe

White Blood cells (WBC)
A type of corpuscle, larger than the size of red blood cells, but smaller in number is present in blood. They are with nuclei and form in bone marrow. They are colourless and known as white blood cells. The ratio between red blood cells to white blood cells is 600:1
Two Types of WBC present in blood

Granulocytes
Non-granulocytes

Granulocytes are further divided into three types,

Neutrophils
Eosinophils
Basophils

Non-Granulocytes are in two types,

Lymphocytes
Monocytes

One cubic milimeter (1 mm3) of human blood contains 4 000-11 000 number of WBC.

The following table shows the percentages of WBC in a healthy person.

WBC destroy infectious particles that entered the body by phagocytosis. Therefore percentages of WBC increase above normal levels. Invertigation of WBC counts in blood helps to diagnose diseases.

The function of WBC is to protect the body from infectious particles entered the body. This is done by phagocytosis and by producing antibodies.

Platelets

In addtion to RBC and WBC there are fragments of cells that cannot be considered as cells in human blood. These corpuscles without nuclei are known as platelels. One cubic milimeter of blood contains 150 000-400 000 platelels. They form in marrow bone. Life span of platelets is approximately 5-7 days. Due to diseases like Dengue and Leptospirosis, platelet count drops drastically. Platelels contain

thromboplastin which help in coagulation of blood.

Blood plasma

92% of blood plasma is water. Other than it the second most abundant compound is protein. Nutrients, nitrogenous waste, hormones, enzymes, gases and ions are present in blood plasma.

Function of blood

Transportation of materials (digested end products respiratory gases, excretory byproducts, hormones, platelets, mineral ions and proteins)
Protect body against pathogenic microbes
Maintenance of chemical coordination and homeostatis among tissues and organs

Blood Circulation

Do the following activity to observe blood circulation of cappillaries.

Activity 01

Observation of blood circulation in blood cappillaries

Materials required:- A small live fish or tadpole, A glass slide, Wet cotton, A microscope

Method :-

Place the small live fish or tadpole on the slide and cover the gills with wet cotton
Observe the blood capillaries in tail area under light microscope
Change the specimen in 10 minutes time to keep it live

You have observed the flow of blood within the blood vessels in the above activity. The force generated by the heart helps to distribute blood through the body. Carry out the activity below to understand the structure of the heart.

Activity

Observe the structure of the heart

Materials required:- A specimen or a model of a heart

Method :-

Observe the external struture of the heart
Observe it's internal chambers, connected arteries and veins, bicuspid and tricuspid valves.
Observe that the atrial walls are thinner than vetricular walls and the thickest wall in the left ventricle.
Use the below diagram to identify the parts.

A longitudinal section of the human heart

Blood circulation of human

Double blood circulation

The circulation where blood flows through lungs is known as pulmonary circulation. The circulation where blood flows through the rest of other organs is known as Systemic circulation. Right ventricle of the heart acts as the pump for the pulmonary circulation, and left ventricle for the systemic circulation. So it is clear that blood flows twice through heart before entering into systemic artery. In

human, when the blood circulates once through the body it flows twice through the heart. This is called as double blood circulation.

Double blood circulation

Heart beat and Cardiac cycle

Atria and Ventricles of heart contract to pump blood out of the heart. These contractions and dialations of heart muscle are known as heart beat. The heart beat rate of a healthy person at rest, is 72 beats per minute. Pulse rate is also similar to heart beat rate. In one heart beat atria contract when ventricles dialate. Next ventricles contract, atria dialate. Contraction of atria is known as diostole whereas contracion of ventricles is known as systole. After that atria and ventricles are in relax mode and it is known as intervening.

Cardicac cycle refers to a complete heart beat from its generation to the beginning of the next beat. The stages of cardiac cycle are as follows;

1) Diastole - Atrial contraction

2) Systole - Ventricular contraction

3) Intervening - Atrial and Ventricular relaxation (complete cardiac diastole)

Electro cardio gram (E .C .G) is used to get information about heart function. This tracing denote the potential changes take place in cardiac muscle cells during heart funtion. Three stages of cardiac cycle can be identified in ECG

Electro cardio gram of a healthy person

P - Atrial contraction
QRS - Ventricular contraction
T - Intervening
ECG wave patterns deviate from normal patterns due to disfunction of heart. Lub - Dup sound in heart beat can be heard by keeping ear or stethescope on chest. Lub sound is longer than Dup sound. Lub sound is produced when bicuspid and tricuspid valves close in atrial contraction. Next produce lup sound and it is shorter. This lub sound is resulted when semi lunar valves close.

Blood pressure
When heart beats, it contracts and pushes blood through the arteries to the rest of the body. This force creates pressure on the ateries. This is called systolic blood pressure.

A normal systolic blood pressure is 110-120 mmHg. Diastolic blood pressure is the pressure in the arteries when heart rests between beats. A normal diastolic blood pressure is between 70-80 mmHg.
Blood presure is measured in millimeters of mercury (mmHg).

Measuring of blood pressure

Normal resting blood pressure is mentioned as follows

Ageing, stressful mentality, sex, diseases of a human are the factors that can increase blood pressure.
Another transportation system closely linked with blood circulatory system is present in human body and it is known as Lymphatic system.

Lymphatic system

Relationship between blood circulation and lymph circulation

Blood capillaries transport blood through cells in the tissues. Blood capillary cell walls are very thin but only WBC and blood plasma can move through the capillary wall. RBC and some plasma proteins cannot move through capillary wall. This fluid moved to tissue is known as tissue fluid. Materials exchanged within body cells and blood occurs through this tissue fluid.

Human lymphatic system

Tissue fluid is absorbed back to capillaries while 1/10 th of it remain within intercellular spaces. This remaining tissue fluid connect with blood circulatory system through a special tubular system known as lymphatic system.

The tissue fluid flowing in the lymphatics is called lymph.

Lymphatic system consists of lacteals, Lumph capillaries and lymph nodes. Lymph is flowing due to pressure caused by muscles around lymph vessels. All the lymph vessels in the body form two main vessels. They are,Thoracic duct and right lymphatic duct. Lymph empties into venous circulation at the junction of internal jugular vein and sub clavian vein.

Main function of lymphatic system is destruction of infectious organisms like bacteria. WBC in lymph nodes destroy them by phagocytosis. Then these lymph nodes become more active and swollen. These swollen lymph nodes are known as kuddeti. Lymph nodes can be found mostly around lungs, heart like organs, skin, arm pits and throat.

Diseases associted with blood circulatory system

Artherosclerosis

Cholesterol is an essential lipid compound produced by the liver. As cholesterol is insoluble in water it is transported as lipo proteins by combining with proteins. Lipo proteins are of two types. Low density lipo proteins ^LDL& and High density lipo proteins ^HDL&. Excessive amount of low density lipo proteins deposit in coronary arteries and other arteries. Thereby the size of the lumen in arteries reduces. The lipid deposits like this in arteries are called Arthero and the condition that occur is called Artherosclerosis.

Due to blocking of coronary arteries, the blood supply to heart is affected. Some parts of the cardiac muscle will be failed to function causing angina (Chest pain). Due to blockage of coronary arteries the region of the cardiac muscle will not recieve blood and that region is failed. This condition is called heart failure.

The reason to increase LDL is consumption of food containg high amount of saturated fatty acids (beef, pork, mutton, full cream milk, egg yolk, prawns, and liver). By controlling such food types and regular exercises can control artherosclerosis.

Hypertention and hypotention

Due to deposition of cholesterol inside arteries, the size of the lumen reduces. Therefore blood supply to different organs get lowered. So to supply required amount of blood, heart has to excert more pressure. The higher pressure excerted onto the arterial wall is called hypertention pressure. Reduction of elasticity of the artery or arterile wall also a reason for hypertention.

Reduction of consumption of saturated fatty acid is important to control this condition. One has to avoid smoking, consumption of alcohol, mental stress, obesity to control hypertension.

Hypotension is the low blood pressure. The blood become less than the normal. Low blood pressure occurs mostly due to nurient deficiencies. During this condition one has to get treatments to increase blood pressure to normal quickly.

Thrombosis

When blood supply to a certain organ is affected due to a blood clot in a blood vessel is called thrombosis. If blood supply to a part of the brain is affected due to a blood clot, the organs that are controlled by that part of the brain fail. This condition is normally called paralysis. If the function of heart is affected due to a blood clot in the coronary artery it is called coronary thrombosis. Due to this, heart attack may occur.

Thrombosis can be controlled by steps taken from child hood. They are as follows,