BIOL122 blood homeostasis

What are the three primary categories of functions of blood?

• Distribution: Gases ($O_2$ and $CO_2$), nutrients, and waste products.

• Regulation: Body temperature, pH, and fluid volume.

• Protection: Against infection (via white blood cells) and hemorrhage/blood loss.

What percentage of total body mass does blood make up, and what is its average volume?

Blood accounts for roughly 8% of total body mass, which equates to approximately 5 liters

When blood is centrifuged with an anticoagulant, what three distinct layers form?

• Top: Plasma fluid (~55% of volume).

• Middle: Buffy coat (composed of White Blood Cells and platelets).

• Bottom: Red Blood Cells (~45% of volume)

What is the difference between blood plasma and blood serum?

Plasma is the liquid portion of whole blood containing soluble proteins like fibrinogen (obtained when an anticoagulant is used).

• Serum is the liquid left over after blood has clotted, meaning it is depleted of fibrinogen.

What are the three main types of plasma proteins, and what are their functions?

Albumins (54%): Often involved in transport.

Globulins (38%): Involved in transport and protection from infection (specifically immunoglobulins/antibodies).

Fibrinogen (7%): A soluble protein crucial for blood clotting

What are the scientific terms for Red Blood Cells, White Blood Cells, and Platelets?

• Red Blood Cells = Erythrocytes

• White Blood Cells = Leukocytes

• Platelets = Thrombocytes

What is haemopoiesis, and where does it occur?

It is the production of the formed elements of blood. All formed elements develop from pluripotent stem cells located in the red bone marrow of long bones (e.g., hips, ribs, tibia, femur)

What hormone stimulates erythropoiesis (RBC formation), where is it produced, and what triggers it?

It is stimulated by erythropoietin (a glycoprotein hormone), which is produced in the kidneys in response to a low Red Blood Cell count.

What are the key structural and physiological characteristics of an erythrocyte (RBC)?

Shape: Biconcave disk (increases surface area for gas exchange).

• Nucleus: Anuclear (lacks a nucleus).

• Composition: Hemoglobin makes up about 33% of its weight.

• Lifespan: Approximately 120 days (produced at a rate of ~2 million per second).

What two components make up Wright’s stain, and what do they target?

Eosin: Stains basic/alkali components red (like the basic proteins in eosinophil granules).

Methylene Blue: Stains acidic components blue (like the DNA in the cell nucleus).

Which White Blood Cells are classified as Granulocytes, and what are their visual markers?

Neutrophils: Multi-lobed nucleus with very few granules.

Eosinophils: Bi-lobed nucleus with red-staining granules.

Basophils: Bi-lobed nucleus with blue-staining granules.

Which White Blood Cells are classified as Agranulocytes, and what are their visual markers?

Lymphocytes: Large, round nucleus surrounded by a very thin layer of cytoplasm.

Monocytes: Very large cells with a characteristic horseshoe-shaped nucleus.

What are the primary immune functions of Neutrophils, Eosinophils, and Basophils?

Neutrophils: Phagocytes that migrate to infection sites to engulf pathogens.

Eosinophils: Involved in allergic responses and combating parasitic invasions.

Basophils: Drive allergic and inflammatory responses by releasing histamine to dilate blood vessels and increase capillary permeability

What are the functions of Lymphocytes and Monocytes?

Lymphocytes: Responsible for the specific immune response; split into T-cells and B-cells (which differentiate into antibody-producing plasma cells).

Monocytes: Differentiate into macrophages to phagocytose pathogens and recruit other immune system elements.

What are platelets, and what cell do they originate from?

Platelets are small (2-3 $\mu m$), anuclear pieces of cytoplasm surrounded by a cell membrane. They are pinched off from large cells called Megakaryocytes in the bone marrow.

What are the three chronological phases of haemostasis?

1) Vascular phase: The damaged vessel undergoes a vascular spasm to constrict and minimize blood loss.

2) Platelet phase: Platelets adhere to exposed collagen, activate, and aggregate to form a temporary platelet plug.

3) Coagulation phase: Soluble fibrinogen is converted into insoluble fibrin threads, creating a mesh network that seals the vessel.

In the coagulation cascade, what triggers the Extrinsic, Intrinsic, and Common pathways?

Extrinsic Pathway: Begins outside the bloodstream when damaged endothelial cells release Factor III (thromboplastin).

Intrinsic Pathway: Begins inside the bloodstream when proenzymes are activated by exposure to collagen.

Common Pathway: Where the extrinsic and intrinsic pathways converge after activating Factor X, leading to the conversion of fibrinogen to fibrin.

Define the three processes that move materials across capillary walls.

Diffusion: Net movement of ions/molecules down a concentration gradient (high to low).

Filtration: Movement of water and solutes across a porous membrane driven by hydrostatic pressure.

Reabsorption: Movement of water via osmosis from areas of low solute concentration to high solute concentration.

What two opposing physical forces determine Net Filtration Pressure (NFP)?

Capillary Hydrostatic Pressure (CHP): Pushes water and solutes out of the capillaries (generated by the heartbeat).

Blood Colloid Osmotic Pressure (BCOP): Pulls water and solutes into the capillaries (generated by trapped plasma proteins)

How does fluid movement change from the arterial end to the venous end of a capillary?

At the arterial end, CHP is high (35 mmHg), making NFP positive, which drives filtration out into the tissue.

At the venous end, CHP drops (18 mmHg), making NFP negative, which drives reabsorption back into the blood vessel.

How is lymph formed, and how does it return to the bloodstream?

• Roughly 24 liters of fluid are filtered into tissues daily, but only 20.4 liters are reabsorbed.

• The remaining 3.6 liters becomes lymph.

• It is gathered by lymphatic vessels and drained back into the circulatory system via lymphatic ducts located in veins near the heart.