Blood Composition and Hemostasis | Physiology

Summary

The blood is composed of plasma, red blood cells, white blood cells, and platelets, each with specific roles in maintaining homeostasis. Plasma, which makes up 55% of the blood, transports substances and regulates osmotic pressure. Red blood cells, lacking a nucleus, are efficient at gas exchange. White blood cells defend the body by consuming bacteria and producing antibodies. Platelets play a crucial role in clotting by forming a platelet plug and triggering the fibrin formation cascade to seal wounds. Together, these components work to protect and sustain the body’s internal balance.

Takeaways

• 😀 Blood is composed of plasma, red blood cells, white blood cells, and platelets.
• 😀 Plasma makes up 55% of the blood and is composed of 90% water, along with proteins like albumin, globulin, and fibrinogen.
• 😀 Plasma helps maintain osmotic pressure, transport liquids and ions, and forms blood clots.
• 😀 Osmotic pressure is the force needed to stop the flow of solvent molecules from a dilute solution to a concentrated solution across a semi-permeable membrane.
• 😀 Plasma acts as a medium for transporting soluble food substances, minerals, waste products, and hormones, while also distributing heat throughout the body.
• 😀 Red blood cells (erythrocytes) are biconcave, lack a nucleus, and are highly flexible, allowing them to squeeze through tiny capillaries.
• 😀 The biconcave shape of red blood cells increases their surface area for better gas exchange, and their lack of a nucleus creates space for hemoglobin.
• 😀 Red blood cells are formed in the bone marrow and are broken down after 120 days in the spleen and liver, with iron being salvaged and stored in the liver.
• 😀 White blood cells (leukocytes) are larger than red blood cells, have irregular shapes, and are essential for the immune system by fighting infections and producing antibodies.
• 😀 Platelets are small cell fragments that help form blood clots by adhering to each other and creating a platelet plug at the site of injury.
• 😀 A cascade of reactions is triggered during clot formation, with prothrombin being converted to thrombin, which in turn converts fibrinogen to fibrin to form a clot.

Q & A

What are the main components of blood?

Blood is composed of plasma, red blood cells, white blood cells, and platelets.

What is the function of plasma in the blood?

Plasma helps maintain osmotic pressure, transports liquids, ions, hormones, soluble food substances, minerals, waste products, and distributes heat around the body.

What makes up the majority of plasma?

Plasma is composed of 90% water and contains proteins like albumin, globulin, and fibrinogen.

What role does osmotic pressure play in blood?

Osmotic pressure helps maintain the balance between blood and tissue fluid by preventing the flow of solvent molecules from a dilute solution to a concentrated solution through a semi-permeable membrane.

What are red blood cells, and how are they structured?

Red blood cells (erythrocytes) are biconcave discs without a nucleus, allowing them to have a high surface area-to-volume ratio for improved gas exchange and space for hemoglobin.

Where are red blood cells formed, and how long do they live?

Red blood cells are formed in the bone marrow and live for about 120 days before being broken down in the spleen and liver.

What happens to the components of red blood cells after they are broken down?

The iron from broken down red blood cells is stored in the liver, while the remaining hemoglobin forms bile pigments.

What are the key functions of white blood cells (leukocytes)?

White blood cells are part of the body's defense system. They actively seek and digest bacteria, produce antibodies to destroy bacteria, and neutralize their toxins.

How do white blood cells respond to an infection?

White blood cells use amoeboid movement, forming pseudopodia to engulf bacteria. This leads to inflammation at the site of infection, and the formation of pus, which consists of dead tissue, bacteria, and white blood cells.

What role do platelets play in blood clotting?

Platelets form a platelet plug when they encounter a break in the epithelium. They become activated and sticky, helping form a clot by triggering a cascade that converts fibrinogen into fibrin, which strengthens the clot.