Human Transportation System and Circulatory System

 When a person falls or gets cut by a sharp object such as a knife or nail, the injured part of the body releases a fluid called blood.

 

Components of Blood

 

 

1. Red Blood Cells (Erythrocytes)

• Erythrocytes are biconcave in shape (flat and concave in the center).

• They do not have a nucleus.

• Their main function is to transport oxygen from the lungs to cells throughout the body.

• The red color of blood is caused by hemoglobin (Hb), a protein containing iron.

• Hemoglobin binds oxygen to form oxyhemoglobin (bright red), and when carrying carbon dioxide, the blood appears dark red or purplish.

2. White Blood Cells (Leukocytes)

• Leukocytes have irregular shapes (amoeboid) and contain a nucleus.

• Their number is fewer than red blood cells, around 8,000 per cubic millimeter of blood.

• The main function of white blood cells is to fight diseases and form antibodies.

3. Platelets (Thrombocytes)

• Platelets have various shapes: round, oval, or elongated.

• They do not have a nucleus but contain granules.

• In adults, the number of platelets ranges from 200,000–500,000 per cubic millimeter.

• Platelets contain enzymes such as thromboplastin, which are essential in blood clotting.

4. Blood Plasma

• Plasma is the liquid component of blood, mostly composed of water (92%).

• It contains plasma proteins such as albumin, fibrinogen, and globulin.

• It also carries nutrients, minerals, hormones, antibodies, and metabolic wastes such as urea and carbon dioxide.

   

  Human Circulatory System

   

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• Systemic Circulation: Blood rich in oxygen flows from the left ventricle of the heart to all body tissues. Oxygen is exchanged with carbon dioxide in body cells, and the carbon dioxide-rich blood is carried back through the veins to the right atrium of the heart.

• Pulmonary Circulation: Carbon dioxide-rich blood from the right ventricle flows to the lungs through the pulmonary artery. In the alveoli of the lungs, gas exchange occurs, and oxygen-rich blood is then carried back to the left atrium through the pulmonary veins. 

 

summary of the human circulatory system pathway

Right Atrium → Right Ventricle → Pulmonary Artery → Lungs → Pulmonary Vein → Left Atrium → Left Ventricle → Aorta → Body → Vena Cava → Right Atrium (again)

 

 

Disorders of the Circulatory System

1. Heart Attack

   • Occurs when the coronary arteries are blocked by fat or cholesterol, reducing blood supply to heart cells.

   • Symptoms include chest pain, pain in the arm or back, shortness of breath, and dizziness.

2. Stroke

   • Caused by blocked or ruptured blood vessels in the brain, leading to oxygen deficiency.

   • It can result in memory loss, loss of muscle control, or nervous system damage.

Other disorders include: Hemophilia, Leukemia, Thrombosis and Embolus, Sclerosis, Varicose veins, and Anemia.

 

Blood Groups

Blood groups classify individuals based on the presence or absence of inherited antigens on the surface of red blood cell membranes. Differences in carbohydrates and proteins on these membranes create variations.

• The ABO and Rh (Rhesus factor) systems are the most important.

• ABO System: Determined by the presence of antigen A and/or B on red blood cells. Corresponding antibodies (anti-A and anti-B) are found in plasma.

• Rh System: Determined by the presence (Rh positive) or absence (Rh negative) of the Rh antigen.

   

  Role of Blood Groups in Transfusions

• Blood group O was once considered a universal donor, but it is no longer recommended due to possible transfusion reactions, though it may still be used in emergencies.

• Blood group AB is the universal recipient because it has no anti-A or anti-B antibodies, making it possible to receive blood from A, B, AB, or O.

• Rh-negative individuals can donate blood to both Rh-negative and Rh-positive individuals, while Rh-positive donors can only give to Rh-positive recipients.

   

   

   

   

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