Study Notes On “BLOOD” For SSC & Railway Exams

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• Blood is a fluid connective tissue.
• The quantity of blood in the human’s body is 7% of the total weight.
• pH value of blood is 7.4.
• There is an average of 5-6 litres of blood in human body.
• Female contains half litre of blood less in comparison to male.
• It also fights infection and regulates temperature.

Blood cells are produced in BONE MARROW

Red cells, white cells and platelets are made in the marrow of bones, especially the vertebrae, ribs, hips, skull and sternum. These essential blood cells fight infection, carry oxygen and help control bleeding.

Blood has four components:
1. Plasma
2. Red blood cells
3. White blood cells
4. Platelets

PLASMA -> Liquid portion of Blood

It contains 92 percent water, constitutes 55 percent of blood volume.

• maintaining a satisfactory blood pressure
• volume to supplying critical proteins for blood clotting and immunity.
• medium for exchange of vital minerals such as sodium and potassium
• helps to maintain a proper pH (acid-base) balance in the body, which is critical to cell function.

RED BLOOD CELLS -> Carry oxygen

•Red blood cells are disc-shaped cells containing haemoglobin,
•haemoglobin (haem=iron-containing)
•Haemoglobin enables the cells to pick up and deliver oxygen to all parts of the body, then pick up carbon dioxide and remove it from tissues.
•Its life span is from 20 days to 120 days and are then broken down into pigments called bilirubin and biliverdin in the liver.
•Its destruction takes place in liver & spleen. Therefore, liver is called grave of RBC.
•they are made in the bone marrow,
•they have no nucleus,
•N.B. oxyhaemoglobin =oxygen rich haemoglobin,
•deoxyhaemoglobin=low oxygen haemoglobin

WHITE BLOOD CELLS -> Defend Body (Fighter)

•White blood cells, also called leukocytes
•White cells are the body’s primary defense against infection.
•They can move out of the blood stream and reach tissues to fight infection.
•They are essential for good health.
•Its life span is from 1 to 2 days.
•White blood cells have nuclei and are also made in the bone marrow.

PLATELETS-> Responsible for clotting

Platelets are the cells that circulate within our blood and bind together when they recognize damaged blood vessels.

Study of blood = HEMATOLOGY

The main functions of blood are to transport oxygen, carbon dioxide, water, nutrients, hormones and waste around the body. Blood also fights infection and regulates temperature.

Composition of blood:
1. Plasma constitutes for about 54% of our blood. 92% of it is water.
2. White blood cells and platelets constitute for about 1% of our blood.
3. Red blood cells constitute for about 45% of our blood.

Circulatory System

Circulation of Blood through the heart:

Systemic Vein ⇨ Sinus Venosus ⇨ Right Auricle ⇨ Right Ventricle ⇨ Pulmonary Artery ⇨ Lungs ⇨ Pulmonary Vein ⇨ Left Auricle ⇨ Left Ventricle ⇨ Trunchus Arteriosus ⇨ Systemic Circulation

  • Open circulatory systems allow the blood flow out of the vessels before returning to the heart via ostia. (no veins involved)E.g. insects
  • Closed circulatory systems don’t allow the blood to leave the blood vessels E.g. humans advantages include faster and controlled delivery of oxygen and nutrients which allow for longer periods of activity.

Important Points:

The largest artery in the body. It carries oxygen-rich blood away from the heart to vessels that reach the rest of the body.
The chambers of the heart, to which the blood returns from the circulation.
The smallest of the body’s blood vessels. Oxygen and glucose pass through capillary walls and enter the cells. Waste products such as carbon dioxide pass back from the cells into the blood through capillaries.
➧Cardiac Valves (Heart Valves)
Any of the four heart valves that regulate the flow of blood through the chambers of the heart.
➧Deoxygenated Blood -> Oxygen-poor blood.
➧Heart Ventricles
The lower right and left chambers of the heart.
➧Interventricular Septum
Interventricular septum is the stout wall separating the lower chambers (the ventricles) of the heart from one another.
One of a pair of organs in the chest that supplies the body with oxygen, and removes carbon dioxide from the body.
The muscular substance of the heart; the middle of the three layers forming the outer wall of the human heart.
➧Oxygenated Blood -> Oxygen-rich blood.
➧Pulmonary Artery
The pulmonary artery and its branches deliver blood rich in carbon dioxide (and lacking in oxygen) to the capillaries that surround the air sacs.
➧Pulmonary Circulation
The circulation of the blood through the lungs.
➧Pulmonary Veins
The veins that return the oxygenated blood from the lungs to the left atrium of the heart.
➧Superior Vena Cava
The large vein that carries blood from the head, neck, arms, and chest to the heart.
➧Vena Cava
A large vein which returns blood from the head, neck and extremities to the heart.
Endothelium is the innermost layer of blood vessels that consists of just a single layer of cells.
➧Veins are blood vessels that carry blood to the heart in an even flow. They have thin walls large lumens and valves.
• The human circulatory system consists of two circuits systemic and pulmonary.
• The coronary artery carries blood to the heart muscle from the aorta. (coronary vein)
• The hepatic artery carries blood to the liver. (hepatic vein)
• The renal arteries carry blood to the kidneys. (renal veins)
• The mesenteric arteries carry blood to the small and large intestines.
• The carotid arteries supply blood to the head. (jugular veins)
• The subclavian arteries supply blood to the arms. (subclavian veins)
• The iliac arteries carry blood to the legs. (iliac veins)
• A portal system is a network of capillaries in one organ or tissue joined to another network of capillaries in another organ or tissue via a vein or veins.
• A pulse is the alternate contraction and relaxation of an artery as blood passes through it.
• Blood pressure is the force blood exerts on the walls of blood vessels.
• A sphygmomanometer is used for measuring blood pressure(normally 120/80 mmHg)
• Atherosclerosis is the hardening of artery walls due to a build-up of fatty deposits.
• Smoking causes heart rate and blood pressure to increase. Diet high in saturated fats increase blood pressure and atherosclerosis. Exercise helps lower blood pressure.



➧Blood Groupings
• Father of Blood Grouping : Karl Landsteiner
• He discovered A, B and O blood groups
Decastello and Sturle discovered AB blood groups

Blood Group                      Can donate to                                 Can receive from
A                                      A,AB                                               A,O
B                                      B,AB                                                B,O
AB                                     AB                                                  A,B,AB,O
O                                    A, B, AB, O                                          O

➧RH factor
• It is a blood antigen found in RBC
• A person can be Rh+ or Rh- depending upon the presence of Rh factor in RBC
• Rh+ can receive blood from both Rh+ and Rh- but Rh- can receive blood only from Rh- only

Blood transfusion techniques was developed by Dr. James Blundell.


Hematoma: A collection of blood inside the body tissues. Internal bleeding often causes a hematoma.

Leukemia: A form of blood cancer, in which white blood cells multiply abnormally and circulate through the blood. The excessive large numbers of white cells deposit in the body’s tissues, causing damage.

Multiple myeloma: A form of blood cancer of plasma cells similar to leukemia. Anemia, kidney failure and high blood calcium levels are common in multiple myeloma.

Lymphoma: A form of blood cancer, in which white blood cells multiply abnormally inside lymph nodes and other tissues. The enlarging tissues, and disruption of blood’s functions, can eventually cause organ failure.

Anemia: An abnormally low number of red blood cells in the blood. Fatigue and breathlessness can result, although anemia often causes no noticeable symptoms.

Hemochromatosis: A disorder causing excessive levels of iron in the blood. The iron deposits in the liver, pancreas and other organs, causing liver problems and diabetes.

Sickle cell disease: A genetic condition in which red blood cells periodically lose their proper shape (appearing like sickles, rather than discs). The deformed blood cells deposit in tissues, causing pain and organ damage.

Bacteremia: Bacterial infection of the blood. Blood infections are serious, and often require hospitalization and continuous antibiotic infusion into the veins.

Malaria: Infection of red blood cells by Plasmodium, a parasite transmitted by mosquitos. Malaria causes episodic fevers, chills, and potentially organ damage.

Thrombocytopenia: Abnormally low numbers of platelets in the blood. Severe thrombocytopenia may lead to bleeding.

Leukopenia: Abnormally low numbers of white blood cells in the blood. Leukopenia can result in difficulty fighting infections.

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