Human Body and Organ System Science Notes

Human Body and Organ System Science Notes

Important Points:

→ Life processes: For the survival of living being, some vital processes are essential. These processes along with the specific properties of living beings are known as life processes.
→ Organ system: Some organs work together to perform a specific function. All such organs together form an organ system.
→ Different systems: Digestive system, respiratory system, circulatory system, nervous system, excretory system, reproductive system, skeletal system, muscular system are different systems present in out body.

→ Every animal needs energy for movements. For this energy, respiration is necessary. If there is no energy in the body, the life processes will not operate normally.
Human Body and Organ System Science Notes 1

Respiration: 3 steps

Human Body and Organ System Science Notes 2

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Respiratory system

Organ Location and Structure Function
Nose Beginning of the respiratory system. Tiny hair, cilia and mucus in the nose. To inhale the air in and to exhale it out. The air is filtered here. The dust particles are trapped in the mucus. The air is made warm due to elongated path.            ‘
Pharynx Beginning of trachea (wind pipe) and oesophagus (food pipe). Epiglottis covering the opening. Due to epiglottis the food particles do not enter the trachea. Air is pushed forwards through pharyngeal region.
Trachea At the upper end there is larynx (sound box). The trachea bifurcates into right and left branch called bronchi. To transport the inhaled and exhaled air to and fro, from the lungs.
Lungs Paired. Present in thoracic cavity on right and left side of the heart. Lungs are covered by double layered protective pleura. Bronchi divide and subdivide into many bronchioles. At the end of each bronchiole there is alveolus. Elastic and spongy structures. Provides place for gaseous exchange. (02 and C02)
Alveoli Rich network of capillaries surround every alveolus. Their walls are extremely thin. Gaseous exchange takes place in alveoli.
Diaphragm Muscular partition dividing thoracic region and abdominal cavity. Movement of air in and out of the body caused due to upward and downward movements of the diaphragm.

→ Exchange of gases during respiration

Human Body and Organ System Science Notes 3

Movements of diaphragm

Human Body and Organ System Science Notes 4

Blood circulatory system

  • Organs in blood circulatory system: heart, blood vessels and capillaries.
  • Transport of various substances by blood: Water, hormones, oxygen, soluble nutrients and waste materials.


Criteria Description
Location In the thoracic cavity slightly inclined on left side. Behind the ribs. Between two lungs
Size Equal to one’s own fist
Weight 360 gram
Coverings A double-layered pericardial * membrane called pericardium. Protective fluid is present between two membranes.
[Note: in textbook it is given as peritoneal membrane. The peritoneal membrane is the term used for serous membrane that surrounds several organs in the abdominopelvic cavity and not the heart.]
Structure Muscular organ formed of involuntary cardiac muscles. Four compartments.
Compartments Upper: Right and left atria or auricles.
Lower: Right and left ventricles
Functions Contraction and relaxation rhythmically. Also called beating of the heart.

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Blood vessels

Three types : (a) Artery (b) Veins (c) Capillaries.

(a) Artery (b) Veins
1. Transporting blood body. from the heart to the 1. Transporting blood heart.from the body to the
2. Deeply located in the body. 2. Superficially located in the body.
3. Walls are thick. 3. Walls are thin.
4. No valves inside 4. Provided with valves.
5. Transporting oxygenated blood (exception: Pulmonary artery) 5. Transporting deoxygenated blood (exception: Pulmonary vein)


  • Arteries keep on branching out to form their branches and sub-branches, ultimately forming capillaries. Capillaries in turn join to form veins.
  • Capillaries are fine hair-like vessels with extremely thin single-celled layered walls.
  • Every important vital organ has network of capillaries.
  • The oxygen, nutrients, hormones, vitamins, etc. are transported to the cells and waste materials of the cells are removed from the cells through capillaries.
  • Thus capillaries carry out exchange of materials in and out of the cell.

Blood circulation

  • Supply of blood to every cell by pumping of the heart and bringing it back to the heart is called blood circulation. Blood circulation is carried out due to heartbeats.
  • One contraction followed by one relaxation that occurs consecutively is called a heartbeat.
  • The heart beats 72 times per minute, which means that normal heart rate is 72 per minute.
  • The heart beats depend upon following factors:
    • Exercise
    • Work
    • Mental stress
    • Emotions
    • Sleep
    • Age
    • Sex.
  • 75 ml blood is pumped out of the heart during each heartbeat.
  • There is ‘lubb’ and ‘dub’ heart sound at the time of each beat which is because of closing of heart valves.

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Blood is fluid tissue. The red colour of the blood is due to haemoglobin. The taste of the blood is salty and its pH is 7.4.

Blood components

  • Plasma (the liquid component)
  • Blood corpuscles or cells.

Human Body and Organ System Science Notes 5

Functions of blood

Human Body and Organ System Science Notes 6

Human blood groups

  • There are four types of blood groups : A, B, AB and O.
  • Rh positive and Rh negative are further subtypes.
  • Thus there are total 8 types of blood groups commonly found in humans. [A Rh +ve, A Rh -ve; B Rh +ve, B Rh-ve; AB Rh +ve, AB Rh -ve; O Rh +ve, O Rh -ve]
  • Blood groups are formed due to antigen present on the RBCs and antibody present in the plasma.

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Blood Donation

  • Blood cannot be manufactured artificially, it must be donated from healthy person to a person who is in need.
  • Blood transfusion: Blood transfusion is the process in which the person who is in need of blood is given transfused blood from a healthy donor.
  • Blood bank: In blood bank the blood from the healthy donor is extracted by specific method with proper care and kept in sterile and refrigerated condition.
  • Blood Donor: The person who gives the blood.
  • Recipient of blood: The person to whom blood is given.
  • Universal donor: The persons with 0 blood group.
  • Universal recipient: The persons with AB blood group.

→ Who is in need of blood? : The persons who had haemorrhage (blood loss) such as victims of accidents, persons who have undergone surgery, patients of thalassemia and anaemia or cancer, at the time of delivery.

  • Blood group is decided according to the heredity/childbirth. As per the blood groups of mother and father, the blood group type is formed in children due to genes concerned with type of blood group.
  • The blood type of donor and recipient should be perfectly matched before the transfusion.
  • Blood donation is considered as the best donation as it can save someone’s life.
  • About 350 ml. of blood is taken at the time of donation.
  • Pregnant and nursing mothers cannot donate the blood.
  • Persons in the age group of 18 to 60 can j donate blood for 3-4 times in a year.
  • National Voluntary Blood Donation Day is observed on 1st October every year.

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Blood pressure

  • The force of flowing blood which is exerted on the arterial wall is called blood pressure.
  • Due to contraction of the heart the blood pressure is created on the arteries.
  • Systolic pressure: 120-139 mmHg
  • Diastolic pressure: 80-89 mmHg
  • Systolic pressure is the maximum pressure in blood vessels when heart is contracting.
  • Diastolic pressure is the minimum pressure in blood vessels when heart comes back to normal or relaxes.
  • Blood pressure is described as 120/80 in medical terms.
  • Sphygmomanometer is the instrument that is used for the measurement of the blood pressure.

Hypertension (High Blood Pressure)

Blood pressure values more than 140-90 is hypertension or high blood pressure. In hypertension, there is stress on blood vessels and heart and thus person has to be careful for controlling it. Hypertension can cause variety of damage in the body which may lead to paralysis, heart disorder or death.


Haematology is a branch of medical science. It encompasses the various topics such as study of blood, haematopoietic organs and blood diseases. The research about diagnosis and remedies of blood diseases are also undertaken under haematology.

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Contribution of scientists

Scientist Year Contribution
William Harvey 1628 Blood circulation in the body.
The concept that heart is a muscular organ.
The working of the valves in the heart.
Dr. Carl Landsteiner 1900 Discovery of A,B,0 blood group system.
Decastello and Sturli 1902 Discovery of AB blood group
Wiener and Landsteiner 1940 Discovery of Rh factor

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