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Human Anatomy

Important Facts about Human Anatomy

  • Longest bone​​ in human body is​​ Femur (thigh​​ bone)

  • Smallest bone​​ -​​ Stapes​​ in the middle​​ ear.

  • Hardest material​​ in the human body is​​ Tooth​​ enamel.

  • Strongest muscle -​​ Jaw​​ muscle

  • Largest muscle - gluteus​​ maximus (buttock​​ muscle)

  • Largest external​​ organ is​​ Skin.

  • Largest internal organ is​​ Liver.

  • Smallest gland -​​ Pineal

  • Largest artery -​​ Aorta

  • Smallest blood vessel -​​ Capillary

  • Element most common in human body is​​ Oxygen​​ (65%)

  • Mineral most common in human​​ body is​​ Calcium.

  • Compound most common in human body is​​ Water.

  • Pigment which gives a dark colour to the skin -​​ Melanin.

  • Nails are modification of​​ Epidermis​​ (external layer of​​ skin).

  • Muscles are attached to bones by connective tissues called​​ Tendons.

  • Bones are attached to bones by​​ Ligaments.

  • The volume of blood in an adult is​​ 4.7 to 5​​ litres.

  • The total number of bones in human body is​​ 206.

  • The most common type of blood group is Type​​ O+.

Important Facts about Blood

  • The study of blood is known as​​ Haematology.

  • The normal volume of blood in an adult human is​​ 4.7 to 5​​ litres

  • Haemoglobin is a protein in​​ red blood cells​​ that carries oxygen to other cells in your body; it contains iron which combines with oxygen to give our blood, a red​​ color.

  • Blood is purified mainly by lungs which remove gaseous impurities like CO2 and kidneys which​​ remove other​​ impurities.

  • The drug or chemical which prevents blood from clotting is called​​ anticoagulant.

  • William Harvey​​ was the first scientist to describe accurately how blood is pumped around the body by​​ the heart.

  • Karl Landsteiner​​ classified the bloods of human beings into A, B, AB, and O​​ groups.

  • Rh​​ blood​​ group​​ system​​ was​​ discovered​​ by​​ Karl​​ Landsteiner​​ and​​ A.S.​​ Weiner.​​ Each​​ blood​​ group​​ type​​ may be Rh positive or​​ negative.

  • The most common blood group type is​​ O+ or O​​ positive

  • The normal blood pressure range is​​ 120/80.​​ The top number (120) is known as the systolic number while the bottom number (80) is known as the diastolic​​ number.

  • Blood pressure is measured by an​​ instrument known as​​ sphygmomanometer.

Blood Group - Relation between Parents and Child



Father's Blood Group







Mothers's Blood Group


A or O

A, B, AB, O

A, Bor AB

A or O


A, B, AB, O

B or O

A, B or AB

B or O


A, B or AB

A, B or AB

A, B​​ or AB

A or B


A or O

B or O

A or B



Child's Blood Group





Types of Blood Vessels and Functions

  • Arteries​​ : Artery carry oxygenated blood under high pressure from the heart to other parts of the​​ body.

  • Veins​​ : Veins carry deoxygenated blood​​ from the organs and tissues back to the​​ heart.

  • Capillary​​ : Capillaries connect arteries and​​ veins.

Main Blood Vessels and Functions


Type of Blood Vessel

Name of Blood Vessel











Largest and principal artery which​​ circulates oxygenated blood to all parts of the body through its branches.

Coronary Artery

A branch of Aorta which supplies oxygenated blood to the heart tissues.


Pulmonary Artery

Only artery which

carries​​ deoxygenated​​ blood. It carries blood from​​ the heart to the lungs for purification.

Carotid Artery

The artery which supplies oxygenated blood to the head and neck.










Superior Vena Cava

This vein returns deoxygenated blood from the head, arms and thorax to the heart.

Inferior​​ Vena Cava

This vein returns deoxygenated blood from the abdomen and legs to the heart.

Coronary Vein

This vein returns deoxygenated blood from the heart muscles to the heart.

Pulmonary Veins

Four pulmonary veins, two from each lung carry​​ oxygenated​​ blood from lungs to the heart.


Jugular Veins

The vein that brings back deoxygenated blood from the head via the superior vena cava to the heart.


Blood Components and Functions

  • Red Blood Cells or​​ Erythrocytes

They carry the protein​​ hemoglobin, which transports oxygen from the lungs to the rest of the body.

  • White Blood Cells or​​ Leukocytes

They are primarily responsible​​ for​​ protecting the body from infection.Platelets or​​ Thrombocytes

They help the blood clotting process (or coagulation) by gathering at the site of an injury.

  • Plasma

It is the liquid component of blood and transports blood cells throughout the body along with nutrients, waste products, antibodies, clotting proteins, chemical messengers such as hormones, and​​ proteins that help maintain the body's fluid balance.

Types of White Blood Cells (Leukocytes)

  • Basophil

Normal white blood cell which increase with bone marrow damage, parasitic infections, or allergic reactions.

  • Eosinophil

A type of white blood cell that controls mechanism associated with allergies and defends the body from infection by parasites and bacteria.

  • Lymphocyte

Two types - T lymphocytes which help regulate the function of other immune cells and directly attacks infected cells and tumors and B lymphocytes which make antibodies.

  • Monocyte

A white blood cell that ingests bacteria and foreign particles.

  • Neutrophil

The most common type of white blood cell, which helps the body fight infection.

Disorders related to blood


Main disorder


Brief​​ details













Iron- deficiency Anaemia

Results from deficiency of iron usually due to blood loss or poor nutrition.


Vitamin- deficiency Anaemia

Results from low levels of Vitamin B12 or folic acid due to poor nutrition.




Aplastic​​ Anaemia

Occurs when the body stops making enough red blood cells. This may be due to viral infections, exposure to toxic chemicals, drugs, and autoimmune diseases.


Hemolytic Anaemia

Occurs when abnormal breakdown of red blood cells takes place.




Sickle Cell Anaemia

It is a hereditary blood disorder, in which red blood cells taking a rigid, sickle shape. This decreases the cells' flexibility and may result in life- threatening complications.


Bleeding Disorders


It is a rare,​​ usually inherited, bleeding disorder characterised by body's inability to control blood clotting or coagulation. It results from a genetic defect in X- chromosome.


von Willebrand Disease

It is the most common hereditary coagulation​​ abnormality that results when the blood lacks von Willebrand factor, a protein that helps the blood to clot.

Blood Cancers


Characterised by rapid production of abnormal white blood cells which cannot fight infection and also impair the​​ ability of the bone marrow to produce red blood cells and platelets.




Lymphoma is a type of blood cancer that occurs when lymphocytes, the white blood cells that form a part of the immune system, divide faster than normal cells or live​​ longer than they are supposed to.


This type of cancer targets the plasma cells which produce antibodies, thus weaken the immune system of the body.





An inherited blood disorder caused when the body doesn't make enough of a​​ protein called haemoglobin, an important part of red blood cells.