Human Blood Circulatory System
Transportation of essential nutrients, waste materials, and other life-saving activities within our body is influenced by the flow of blood from one part to the other. The blood Circulatory System is a collection of the human heart, blood vessels, and blood that perform the activities as mentioned earlier.
- Blood
- Blood Vessels
- Heart
- Blood Circulation
Blood
Blood is a heterogeneous, viscous, and red connective tissue.
Structure of Blood
The blood in human body comprises of two major components: Plasma and Blood corpuscles (cells).
Plasma
Plasma is a hay-colored fluid that constitutes around 55% of the total composition of the blood. The blood corpuscles are free to float on the plasma. It is responsible for the transmission of digested food, waste materials, hormones, and other important or harmful chemicals from the site of production to the site of consumption or excretion. It regulates the body temperature, amount of water, chemical compositions, and pH value of the blood. It contains fibrinogen that helps in blood clotting.
Blood Corpuscles
These are the blood cells present in the blood. They constitute around 45% of the blood.
Red Blood Cells (RBCs)or Erythrocytes
- RBCs are red colored, biconcave, and enucleated(lack the presence of a nucleus)disc like structure present in the plasma.
- They contain hemoglobin that provides them the red-color.
- In the body of a healthy man, number of RBCs ranges from 5 - 5.5 million per cubic mm and in the body of a healthy woman, it ranges from 4.5 - 5 million per cubic mm.
- The life span of RBCs is around 120 days. They are destroyed in the liver.
- The major function of RBCs is to help in the exchange of gases, and maintain the viscosity of blood and ion-balance.
White Blood Cells (WBCs)or Leucocytes
- WBCs are irregular in shape and have a nucleus.
- In the body of a healthy human being, number of WBCs ranges from 4000 to 11000 per cubic mm.
- Their life span is very short, i.e., few days only. They are destroyed in the liver, spleen and at the site of infection.
- Its major function is to protect the human body from foreign bodies. It produces antibodies that functions to kill and/or neutralize the germs, viruses, and bacteria that enter our body and destroy the damaged cells by phagocytosis. It keeps the human body healthy.
Platelets or Thrombocytes
- Platelets are colorless, oval, or round, blood corpuscles that do not have a nucleus.
- In the body of a healthy human being, number of platelets varies from 2.5 lakhs to 4.5 lakhs.
- Their life span is around 5 to 10 days.
- They are destroyed in the spleen.
- Its important function is to help in the coagulation or clotting of blood by releasing a chemical called thromboplastin.
Functions of Blood
We have studied the specific functions of the Blood Cells in this chapter above. Below, we discuss the major functions of the blood in the human body:
- Transportation: Blood transports essential materials like water, nutrients, hormones, and oxygen to the tissues. It also transports waste substances like urea, carbon dioxide, etc. to the site of excretion.
- Protection: It protects the body by fighting against germs and toxic materials. Fibrinogen and prothrombin proteins present in platelets and plasma help in blood clotting.
- Regulation: It maintains body temperature and balances the amount of water to a constant level. It also regulates different chemicals like salt, sodium, potassium, calcium, acidity, alkalinity, etc.
Blood Vessels
The path through which the blood flows in the human body is called blood vessels.
Types of Blood Vessels
In general, the human body has three types of blood vessels. We discuss their major characteristics below:
Arteries
Arteries are the blood vessels that carry pure or oxygenated blood.
Pure blood flows under high pressure in the human body. Therefore, arteries are placed deep under the human skin. They have thicker walls to bear the high pressure of the blood.
As the blood flows under high pressure, there is little to no chance of the backflow of the blood. Hence, arteries do not contain valves.
It is important to note, however, that the Pulmonary Artery carries impure or deoxygenated blood from the heart to the lungs.
Veins
Veins are the blood vessels that carry impure or deoxygenated blood.
Impure blood flows under low pressure in the human body. Therefore, veins are placed superficially on the human skin. Consequently, they have thinner walls.
As the blood flows under low pressure, there is a chance of the backflow of the blood in the veins. Hence, veins contain valves to prevent the backflow of the blood.
It is important to note, however, that the Pulmonary Vein carries pure or oxygenated blood from the lungs to the heart.
Capillaries
Capillaries are extremely narrow and thin-walled blood vessels. They connect arterioles (branches of Arteries) to the venules (branches of Veins). These connections act as the site of transmission of various chemical substances.
Heart
Internal Structure of Heart
Blood Circulation
Blood circulation is the transport of pure blood from the heart to the entire body and back into the heart in the form of impure blood.
The circulation of blood form the left ventricle of the heart into the right auricle of the heart without reaching the lungs is called systemic circulation.
Heart attack
The following information about Heart attack is referenced from the Class 10 Science & Technology Book issued by the Ministry of Education, Nepal.
Risk factors of heart attack
- Age
- Consumption of tobacco products
- High blood pressure or hypertension
- High cholesterol and triglycerides
- Diabetes
- Family history
- Lack of regular exercise and unhealthy diet
- Stressful life
- Consumption of illegal drugs
Symptoms of heart attack
Preventive measures of heart attack
- Maintain healthy lifestyle
- Avoid the consumption of alcohol, tobacco, and tobacco products
- Maintain your body weight
- Consume a healthy and balanced diet
- Exercise regularly
- Maintain mental health and reduce stress
- Avoid high blood pressure and diabetes
- Visit doctors regularly for health check-ups.
Diagnosis of heart attack and treatment
Heartbeat
Heartbeat is defined as the continuous rhythmic beat of the heart caused due to contraction and relaxation of the muscles of the heart. It is measured as pulse rate or heart rate.
Heart beat increases when we face moments such as fear, fright, fight, etc.