Body Fluid and its Circulation Class 11 Notes

Two types of body fluid are found in humans:

Extra-cellular body fluids: The body fluids are situated outside the cell. Example: Cerebrospinal fluid, synovial fluid, interstitial fluid, blood, and lymph.
Intracellular body fluids: The body fluids are situated within the cell. Example: Cytoplasm and cellular protein remain in colloidal nature.

Two body fluids are in a continuous circulatory motion- blood and lymph.

Blood and its components:

Blood is a liquid connective tissue whose main function is to transport and provide a defense. An adult human being has 5.5l of blood, pH-7.4, which consists of the following components.

Plasma:

It is the liquid component of the blood that contains 90-92 % of water and 8-10% of other substances.

Other substances include:

Plasma protein: It includes fibrinogen thromboplastin that helps in blood clotting and globulin that provides immunity.
Nutrients: Plasma contains digested nutrients like monosaccharides, amino acids, and fats.
Vitamins: All the vitamins are transported through plasma from one cell to another.
Minerals: Minerals like Sodium, Potassium, calcium, Phosphorus, chlorine are all present in the blood plasma in an ionic state.
Hormones: All the hormones are transported through plasma.
Excretory product: Products like urea, uric acid, and ammonia is transported from the liver to the kidney through plasma where it is filtered out and carbon dioxide in the form of bicarbonate ion is transported through the plasma from each and every cell to the lungs.
Dissolved gases: Dissolved gases like carbon dioxide are transported through plasma.

Formed elements

They are of three types RBC, WBC, and platelets.

RBC or erythrocytes:

They are biconcave cells without having a nucleus (except camel) and cell organelle. It is the smallest cell of the human body, 6-8 micrometers in diameter. RBC contains only cytoplasm and a red color pigment called hemoglobin.
Each RBC has 280 million hemoglobin molecules. Hemoglobin is made up of iron-containing four Heme rings.
RBC is formed in the bone marrow of long bones and in the liver and Yolk during the fetal stage, dies in the spleen, and gets digested in the liver.
It has a lifespan of 120 days.
The total RBC count is 4.5 to 5.5 million per mm3 of blood. If the number increases then its normal value the condition is called polycythemia and if decreases the condition is called erythrocytopenia.
The process by which RBC is formed is called erythropoiesis.

Function: It helps in the transport of Oxygen and Carbon dioxide.

WBC or leukocytes:

These are spherical cells containing nucleus, cytoplasm, and cell organelle. WBC is formed in the bone marrow or in a gland called the thymus gland situated near the heart.
The normal value ranges from 6000-8000 per mm3 of blood which increases during infection to up to 12000 and if it remains above 17000 per mm3 of blood then we suffer from a disease called leukemia or blood cancer.

WBC is of two types:

1. Agranulocyte: These cells do not contain granules. They are of two types:

a. Monocytes: These are the largest cell of all WBC having a kidney-shaped nucleus. It accounts for 2-10% of total WBC. It has the property of diapedesis (movement by squeezing out of blood vessel) and kills pathogen by phagocytosis.

b. Lymphocytes: These are spherical-shaped nuclei. They account for 20 to 40% of the total WBC. It is of two types:

B Lymphocytes or bone marrow lymphocytes
T Lymphocytes or thymus gland lymphocytes.

It provides immunity.

2. Granulocytes: These are cells having cytoplasmic granules, it is of three types:

Esinophyll: These cells have bilobed nuclei, which account for 1-6 % of total WBC. An increase in the number cause allergy in humans.
Basophils: These cells have a three-lobed nucleus, the normal count is a 0 to 1% increase in number causing the allergy.
Neutrophils: They have multilobed nucleus normal count is 42-70% of total WBC and they have the property of diapedesis and kill pathogen by phagocytosis.

Platelets or thrombocytes:

These are formed from broken fragments of RBC and are not considered true cells.
Its number ranges from 1.5 to 2.5 lakh per mm3 of blood.
The process of formation of platelets is called thrombopoiesis. An increase in the number of thrombocytes is called thrombocytosis whereas a decrease in number is called thrombocytopenia.
These are formed from broken fragments of RBC and are not considered true cells.
Its number ranges from 1.5 to 2.5 lakh per mm3 of blood.
The process of formation of platelets is called thrombopoiesis. An increase in the number of thrombocytes is called thrombocytosis whereas a decrease in number is called thrombocytopenia.

Functions: It helps in blood clotting.

Blood Clotting:

The process of stopping bleeding from the site of injury is called blood clotting or coagulation.

It takes place as follow:

The injured cell releases a factor called thromboplastin and the blood platelets release a factor called platelet factor 3 or platelet thromboplastin.
Both in presence of calcium ions activate an enzyme prothrombinase which inactivates heparin an anticoagulant that does not allow blood to clot. Prothrombinase activates prothrombin to thrombin.
Thrombin converts inactive fibrinogen to fibrin which is a net-like protein that does not allow blood to come out and hence clotting takes place.

Role of Vitamin K In blood clotting:

Vitamin K is essential for blood clotting since it is necessary for the synthesis of prothrombin in the liver. If Vitamin K is inadequate in the diet or is not absorbed in the intestine, blood clotting becomes inefficient.

Heart:

It is a hollow muscular organ that is narrow at the base and broad at the apex situated in between both the lungs, 250-280 grams in weight which is made up of specialized muscles called cardiac muscle.
The heart is externally protected by Rib cage and internally by a membrane called the pericardium. It is of two layers parietal pericardium and inner visceral pericardium. In between them, there is a cavity called the parietal cavity which is filled with pericardial fluid.
The human heart is four-chambered the upper two atrium- right and left respectively and the lower two ventricle- right and left respectively. The wall of the ventricle is much more muscular than the wall of the Atrium.
In between both the Atrium, there is a muscular wall called the interatrial septum. In between both the ventricle, there is a partition wall called the interventricular septum. In between the atrium and ventricle, there is a partition wall called the atrial ventricular septum.
Both the Atrium has a groove-like structure, dog's ear-shaped called auricle. the left atrium receives oxygenated blood from the lungs and the right atrium receives deoxygenated blood from the whole body by three main veins- superior Vena cava, inferior Vena cava, and coronary sinus. The inferior Vena cava is guarded by the Eustachian valve and the coronary sinus is guarded by the Thebacian valve prevents backflow of blood.
In between the right atrium and ventricle, it is guarded by the tricuspid valve and in between the left Atrium and ventricle by the bicuspid or mitral valve. To these valves, some elongated muscle filament remains attached called chordae tendineae that remains connected with muscles of ventricles called papillary muscles.
From the right ventricle Pulmonary artery arises that carries deoxygenated blood to the lungs and from the left ventricle aorta arises, it carries oxygenated blood to the whole body and both are guarded by semilunar valves.

Important Question Answers

What is systole and diastole? 

The contraction of the heart muscle is called systole and the relaxation of the heart muscle is called diastole.

What is a heartbeat? 

The rhythmic contraction and expansion of heart muscle are called heartbeat. It is 72 times per minute.

What is heart rate? 

The number of heartbeats per minute is called heart rate.

What is a cardiac cycle? 

A single heartbeat is also known as the cardiac cycle. The cardiac cycle is complete in the following events:    

1. Atrial systole: when both the atrium is filled with blood, both the atrium contracts this is called atrial systole. It takes 0.1 seconds, the area of the atrium decreases, pressure increases, and both the bicuspid and tricuspid valve get opened, blood passes to the ventricles.
    
2. Ventricular systole: contraction of both the ventricles takes place, the chordae tendanae muscles get pulled which causes the closing of the bicuspid and tricuspid valve and heart first sound or “lub” is heard. The area of the ventricle decreases, blood pressure increases, and blood from the left ventricle passes to the aorta and from the right ventricle to the pulmonary artery by the opening of the semilunar valve. It is completed in 0.3 seconds.                                                     
                                                                         3. Joint diastole: In this phase relaxation of the atrium and ventricles takes place, the semilunar valve gets closed and the heart's second sound or ‘’dub’’ is heard. It takes 0.4 seconds.

What is stroke volume? 

The amount of blood pumped by a heart in a single heartbeat is called stroke volume. It is 70ml/heartbeat.

What is cardiac output? 

The cardiac output is the quantity of blood pumped by the heart every minute.                                              
Cardiac output= stroke volume x heart rate= (70x72) ml= 5040ml= 5.4 l

Differentiate between artery and vein.

artery	Vein
The artery has a relatively thick wall and a small lumen.	Veins have a relatively thin wall and large lumen.
They are usually deep-seated.	They are superficially situated.
Arteries have no valves.	Veins have valves that prevent the backward flow of blood.
Arteries distribute blood from the heart to the different parts of the body	veins collect blood from different parts of the body and pour it into the heart.
In arteries, blood flows through jerks.	In veins, blood flows smoothly.
Carries oxygenated blood except for the pulmonary artery.	Carries deoxygenated blood except for pulmonary veins.

What is a pulse? 

Rhythmic contraction and relaxation of the aorta and its and its main artery is called a pulse.
Or the wall of the artery also undergoes rhythmic contraction and relaxation due to which blood flows in arteries in jerk which is called a pulse.

What is blood pressure?

It is the force exerted by the blood on the walls of blood vessels while it is moving through them.
It is of two types:

1. Systolic: It is the upper or higher pressure of blood exerted on the walls of blood vessels while traveling. It is the contraction of the heart. It is 120mm/Hg in normal adults.

2. Diastolic: it is the lower pressure of blood while traveling. It is during the relaxation of the heart. It is 80mm/Hg in normal adults.

Nervous Control of Heartbeat

The human heart is myogenic means it is controlled by muscles but the contraction and expansion of muscles in nervously controlled.
The right atrium has a muscular region called the sinoatrial node or SA node or pacemaker. Below the SA node, there is another neuromuscular junction called AV node or atrioventricular node or pace shutter.
The SA node is connected with the cardioinhibitory and cardio acceleratory center of the media region of the brain by the sympathetic and parasympathetic nerves. From the SA node nerve passes to both the atrium and to the AV node, from the AV node a bunch of neurons arises called a bundle of HIS that branches to both the ventricle called Purkinje fiber.
Nervous stimulus from the cardio accessory center is brought by sympathetic nerves to the SA node which passes to both the atrium causes its contraction and then to the AV node which through the bundle of HIS and Purkinje fiber passes to the ventricle which causes its contraction.
Nervous stimulus from the cardioinhibitory center through parasympathetic nerve cause relaxation of heart muscles.