D3.2 - Blood and Circulation

Blood and Circulation

• Blood is a connective tissue, linking all body cells and organs.
• Connective tissue supports and connects different parts of the body (e.g., blood, bones).

Plasma

• Plasma is the liquid component of blood (55% of blood volume).
• Plasma contains fluids, proteins, glucose, gases, wastes, vitamins, and minerals.
• Plasma carries all blood cells.
• Plasma helps transport carbon dioxide (CO2) in the blood.

Remaining Blood Volume

• The remaining 45% of blood volume consists of:
  • Erythrocytes (red blood cells): 44% of blood volume
  • Leukocytes (white blood cells): 1% of blood volume
  • Platelets: Involved in blood clotting.

Erythrocytes (Red Blood Cells)

• Erythrocytes are also known as red blood cells.
• They make up 44% of blood volume.
• They are specially designed to carry oxygen.
• They lack a nucleus.
• Their folded disk shape maximizes surface area to carry more oxygen.
• Packed with hemoglobin, an iron-containing molecule that carries oxygen.
• Anemia occurs when a person has too few red blood cells or too little hemoglobin, reducing oxygen flow.

Leukocytes (White Blood Cells)

• Leukocytes are also known as white blood cells.
• They make up 1% of blood volume.
• They are responsible for immune system responses.
• They contain nuclei.
• Three types of granulocytes: neutrophils, basophils, and eosinophils
• Monocytes can leave the bloodstream to destroy bacteria.
• Lymphocytes produce antibodies to fight pathogens.

Platelets

• Platelets are formed when larger bone marrow cells break apart.
• They do not contain a nucleus.
• They break down quickly in blood.
• They play a key role in blood clotting, preventing excessive blood loss.

Functions of Blood

• Transport: Carries cells and materials (nutrients, waste, hormones).
• Homeostatic Regulation:
  • Vasodilation: Body heats up; blood transports heat from respiration and activity to skin; blood vessels widen to increase heat loss. Sweat/Perspiration helps as well.
  • Vasoconstriction: Body cools down; blood vessels narrow to reduce heat loss; shivering increases heat production by cellular metabolism.

Circulation and Action of Capillaries

• Combined surface area of capillaries is about 6300 m².
• Capillaries exchange materials between blood and cells.

Capillary Exchange

• Capillaries prevent resource waste when cells don't need servicing.
  • They use arteriovenous shunts/sphincters to regulate blood flow.
• Cells are surrounded by interstitial fluid (extracellular fluid).
• Blood moves slowly through capillaries, allowing more time for diffusion.
• Exchange of materials between blood and interstitial fluid happens at the arterial end and midsection of the capillaries.
• Blood is bright red at the arterial end because it's oxygenated.
• Oxygen and nutrients are high in blood but low in tissue fluid/interstitial fluid.
• Diffusion occurs between the blood and tissue fluid.
• At the venous end, osmotic pressure is higher than blood pressure, causing tissue fluid to be reabsorbed and returning to the blood.

Blood Disorders

• Hemophilia: Inherited blood disorder with insufficient clotting protein. Those with severe hemophilia have less than 1% of clotting protein and bleeding can be dangerous. Factor VIII injections can help.
• Leukemia: Cancer of white blood cells. Two types: myeloid (too many immature leukocytes, impairing infection fighting, leading to anemia) and lymphoid (cancer of lymphocytes). Leukemia can be acute or chronic.

Test your knowledge on blood composition and circulation. This quiz covers various components of blood, including plasma, erythrocytes, and their roles in the body. Understand how blood links cells and organs and the importance of its cellular components.