Blood Revision Notes

Red blood cells carry oxygen from the lungs to body tissues. They contain hemoglobin, a protein that binds oxygen.

Mature red blood cells do not have a nucleus, allowing more space for hemoglobin.

• Transport oxygen to body cells.
• Contain hemoglobin.
• Lack a nucleus to maximize oxygen carrying capacity.

White blood cells defend the body against infections by identifying and destroying pathogens.

They are part of the immune system and vary in type and function.

• Fight infections and foreign substances.
• Part of the immune system.

Platelets are small cell fragments that help blood clot at injury sites to prevent excessive bleeding.

They gather at wounds and form clots to seal damaged blood vessels.

• Help blood clot to stop bleeding.
• Form clots at injury sites.

Plasma is the liquid part of blood that carries blood cells, nutrients, hormones, and waste products throughout the body.

It makes up about 55% of blood volume and is mostly water.

• Carries cells and dissolved substances.
• Transports nutrients, hormones, and wastes.
• Makes up over half of blood volume.

Red blood cells are small, round cells with a biconcave disc shape, which gives them a pale center in images due to thinner middle areas.

They do not have a nucleus, which makes them distinct from white blood cells.

• Small and round with pale center (biconcave shape).
• No nucleus present.

White blood cells are larger than red blood cells and have a visible nucleus.

They often have an irregular shape and can appear darker in stained images due to the nucleus.

• Larger than red blood cells.
• Have a visible nucleus.
• Often irregular in shape.

In images or diagrams, red blood cells appear smaller, round, and lack a nucleus, while white blood cells are larger, irregular, and have a nucleus.

Staining techniques often color white blood cells darker because of their nucleus.

• Size, shape, and nucleus presence help identification.
• Red blood cells: small, round, no nucleus.
• White blood cells: larger, irregular, nucleus present.

Red blood cells (RBCs) are specialized for oxygen transport. They contain haemoglobin, a protein that binds oxygen in the lungs and releases it in tissues where it is needed.

The biconcave shape of RBCs increases their surface area, enhancing oxygen absorption and release.

• Contain haemoglobin for oxygen transport.
• Biconcave shape increases surface area.

White blood cells (WBCs) are crucial for the immune response. They include lymphocytes and phagocytes, each with specific functions.

Lymphocytes produce antibodies that target specific pathogens, while phagocytes engulf and digest foreign invaders through phagocytosis.

• Lymphocytes produce antibodies.
• Phagocytes perform phagocytosis.

Platelets are small cell fragments that play a key role in blood clotting. They gather at injury sites and release chemicals that initiate clot formation.

This process prevents excessive blood loss and facilitates wound healing.

• Initiate clot formation.
• Prevent excessive blood loss.

Plasma is the liquid component of blood that carries cells and dissolved substances throughout the body.

It transports nutrients, hormones, waste products like urea, and gases such as carbon dioxide.

• Transports nutrients and waste.
• Carries hormones and gases.

When a blood vessel is damaged, platelets adhere to the site and release chemicals that initiate clotting.

These chemicals convert fibrinogen, a soluble plasma protein, into fibrin, an insoluble protein that forms a mesh.

• Platelets adhere to injury site.
• Fibrinogen converts to fibrin.

The fibrin mesh traps blood cells, forming a stable clot that seals the wound.

This prevents further blood loss and allows the vessel to repair.

• Fibrin mesh traps blood cells.
• Clot seals the wound.

The clot acts as a barrier, preventing pathogens from entering the body through the wound.

This reduces the risk of infection and supports the immune response.

• Clot blocks pathogen entry.
• Reduces infection risk.

Lymphocytes have a large, round nucleus that occupies most of the cell's volume, leaving only a thin rim of cytoplasm visible. This makes the nucleus appear dominant and compact.

They are generally smaller cells compared to phagocytes.

In images, lymphocytes appear as cells with a smooth, spherical nucleus and minimal surrounding cytoplasm.

• Large, round nucleus
• Minimal cytoplasm
• Smaller cell size

Phagocytes, such as neutrophils and macrophages, have an irregular or lobed nucleus, often segmented into multiple parts.

They contain more cytoplasm than lymphocytes, which is visible around the nucleus.

Phagocytes are usually larger cells and their cytoplasm may contain granules or vacuoles.

In images, phagocytes appear with a lobed nucleus and abundant cytoplasm.

• Lobed or irregular nucleus
• More cytoplasm visible
• Larger cell size

The large nucleus and small cytoplasm of lymphocytes reflect their role in producing antibodies or killing infected cells, requiring focused genetic activity.

Phagocytes' lobed nucleus and abundant cytoplasm support their function of engulfing and digesting pathogens through phagocytosis.

Recognizing these features in images helps understand how the immune system responds to infection.

• Lymphocytes: specific immune responses
• Phagocytes: engulf and digest pathogens
• Cell structure indicates function

Lymphocytes are white blood cells that produce antibodies, which are specific proteins that recognize and bind to antigens on pathogens.

These antibodies neutralize pathogens or mark them for destruction by other immune cells.

This specific immune response helps the body target particular infections effectively.

• Produce antibodies
• Antibodies bind to pathogen antigens
• Neutralize or mark pathogens for destruction

Phagocytes protect the body by engulfing pathogens in a process called phagocytosis.

During phagocytosis, the phagocyte surrounds the pathogen, encloses it in a vesicle, and digests it using enzymes.

This removes harmful microorganisms and debris from the body.

• Engulf pathogens
• Enclose pathogens in vesicles
• Digest pathogens with enzymes

Antibodies produced by lymphocytes can mark pathogens, making it easier for phagocytes to identify and engulf them.

Together, lymphocytes and phagocytes provide a comprehensive defense against infections.

Understanding their roles helps explain how the immune system fights disease.

• Antibodies assist phagocytes
• Combined action removes pathogens
• Essential for effective immunity

Fibrinogen is a soluble protein found in blood plasma.

When a blood vessel is damaged, fibrinogen is converted into fibrin, an insoluble protein.

This conversion is triggered by enzymes activated during the clotting process.

• Fibrinogen is soluble and circulates in plasma
• Clotting enzymes convert fibrinogen into fibrin
• Fibrin is insoluble and forms solid strands

Fibrin strands weave together to form a mesh or network.

This mesh traps blood cells and platelets at the injury site.

The trapped cells and fibrin mesh create a stable blood clot that seals the wound and prevents further bleeding.

• Fibrin forms a mesh
• Mesh traps blood cells
• Clot seals the wound

Clotting prevents excessive blood loss after injury, which is vital for survival.

The clot also provides a framework for tissue repair and healing.

Without clotting, wounds would continue to bleed and risk infection.

• Prevents blood loss
• Supports tissue repair
• Essential for healing