chapter 17

What is hematopoiesis?

the continuous process by which all blood cells are formed from hematopoietic stem cells (hemocytoblasts) in the red bone marrow. It includes the production of erythrocytes, leukocytes, and platelets under the control of hormones and growth factors such as erythropoietin, thrombopoietin, and colony-stimulating factors.

"What is serum?

is the portion of blood plasma that remains after clotting has occurred. It lacks fibrinogen and other clotting factors but retains electrolytes, antibodies, hormones, and proteins that are not involved in coagulation.

What is erythropoietin and what role does it play?

a hormone produced primarily by the kidneys in response to hypoxia. It stimulates the red bone marrow to increase the rate of red blood cell production (erythropoiesis), ensuring adequate oxygen delivery to tissues."

What is plasma and what is it composed of?

the liquid component of blood that makes up about 55% of total blood volume. It is composed of approximately 90% water and contains dissolved substances such as plasma proteins (albumin, globulins, fibrinogen), nutrients, electrolytes, gases, hormones, and metabolic wastes. Plasma helps transport these substances and maintains osmotic and pH balance."What are erythrocytes and what is their function?,"Erythrocytes, or red blood cells, are small biconcave cells that lack a nucleus and most organelles, allowing for maximum hemoglobin storage and gas exchange. Their primary function is to transport oxygen from the lungs to body tissues and carbon dioxide from tissues to the lungs. They live about 100–120 days before being removed by the spleen and liver

What is hemoglobin and how does it function?

the iron-containing protein inside red blood cells that binds and transports oxygen and carbon dioxide. It consists of four globin chains, each with an iron-containing heme group. Each hemoglobin molecule can carry up to four oxygen molecules. It also helps buffer blood pH and contributes to carbon dioxide transport."

What are leukocytes and what is their general function?

or white blood cells, are the body’s defense cells. They protect the body from infectious microorganisms, toxins, and foreign substances. Unlike red blood cells, leukocytes have nuclei and can leave the bloodstream to enter tissues through a process called diapedesis.

What is an antibody?

a protein molecule produced by plasma cells derived from B lymphocytes. Antibodies recognize and bind to specific antigens to neutralize them, tag them for destruction, or activate the complement system, playing a key role in the immune response."

What are platelets and what do they do?

also called thrombocytes, are small cell fragments derived from megakaryocytes in the bone marrow. They play a critical role in hemostasis by forming temporary platelet plugs at sites of blood vessel injury and releasing factors that promote blood clotting

What is hemostasis?,

the physiological process that stops bleeding at the site of injury. It involves three major steps: vascular spasm (vasoconstriction), platelet plug formation, and coagulation, which stabilizes the plug with a fibrin mesh."

What is coagulation?

is the process by which liquid blood is transformed into a gel-like clot. It occurs through a complex cascade involving clotting factors that lead to the conversion of prothrombin to thrombin, which then converts fibrinogen to fibrin. Fibrin strands reinforce the platelet plug and seal the wound."

What is anemia?

a condition in which the blood has a decreased oxygen-carrying capacity, usually due to a reduced number of red blood cells, decreased hemoglobin, or abnormal hemoglobin. Symptoms include fatigue, pallor, shortness of breath, and dizziness. Common causes include iron deficiency, blood loss, and vitamin B12 deficiency."

What is polycythemia?

is a condition characterized by an abnormally high red blood cell count, which increases blood viscosity and can slow circulation. It may occur as a primary bone marrow disorder (polycythemia vera) or as a secondary response to chronic hypoxia or excessive erythropoietin production."

What are leukocytosis and leukopenia?

refers to an elevated white blood cell count, often due to infection or inflammation. Leukopenia refers to a decreased white blood cell count, which can result from bone marrow suppression, chemotherapy, or certain viral infections, and increases the risk of infection.

"How does blood help regulate the body?

Blood regulates body temperature by distributing heat, maintains normal pH through buffers like bicarbonate, and preserves fluid volume through plasma proteins that maintain osmotic pressure.

"How does blood provide protection for the body?

by preventing blood loss through clot formation and defending against infection through white blood cells, antibodies, and complement proteins."

What is the composition of blood?

"Blood consists of plasma (55%) and formed elements (45%), which include erythrocytes, leukocytes, and platelets. The pH of blood ranges from 7.35 to 7.45, and total blood volume averages about 5 liters in adults.

"Describe the structure and function of erythrocytes

are biconcave, flexible cells lacking nuclei and mitochondria. Their shape increases surface area for gas exchange and allows them to squeeze through capillaries. They rely on anaerobic metabolism to avoid using the oxygen they carry, and their primary function is oxygen and carbon dioxide transport."

Describe erythropoiesis

the process of red blood cell formation that occurs in the red bone marrow. It involves differentiation from a hematopoietic stem cell to a reticulocyte over about 15 days. Reticulocytes enter the bloodstream and mature into erythrocytes within two days.

How does erythropoietin maintain red blood cell levels?

maintains adequate red blood cell levels through a negative feedback mechanism. When oxygen levels drop, kidneys release EPO, stimulating the bone marrow to produce more RBCs. Once oxygen levels normalize, EPO secretion decreases."

What are the five types of leukocytes and their functions?

"Neutrophils (phagocytize bacteria), Lymphocytes (B cells produce antibodies, T cells attack infected cells), Monocytes (become macrophages that engulf debris), Eosinophils (defend against parasites and modulate allergies), and Basophils (release histamine and promote inflammation)."

What is the composition and function of blood plasma?

about 90% water and contains proteins (albumin, globulins, fibrinogen), nutrients, hormones, gases, and wastes. It maintains osmotic pressure, transports materials, buffers pH, and carries immune and clotting proteins."

What are the three major steps of hemostasis?

1) vascular spasm, where blood vessels constrict to reduce blood loss; 2) platelet plug formation, where platelets adhere to exposed collagen and release chemicals that attract more platelets; and 3) coagulation, where fibrin threads reinforce the plug."

What is the difference between the intrinsic and extrinsic clotting pathways?

The intrinsic pathway is initiated by damage within the blood vessel and uses clotting factors already present in the blood. The extrinsic pathway is triggered by external trauma that exposes tissue factor (factor III). Both pathways converge at factor X activation to form the common pathway leading to fibrin formation.

Why are the liver and calcium ions important in hemostasis?

The liver produces most plasma proteins, including clotting factors that are necessary for coagulation. Many of these factors require vitamin K for synthesis. Calcium ions (Ca²⁺) act as essential cofactors for several steps in the clotting cascade."

Explain ABO and Rh blood typing

determined by antigens on red blood cell membranes. Type A has A antigens, type B has B antigens, type AB has both, and type O has neither. Plasma contains antibodies against absent antigens. Rh factor (D antigen) determines positive or negative type. Mixing incompatible blood types can cause agglutination and hemolysis."

What is the role of baroreceptors in blood pressure control?

Baroreceptors in the carotid sinuses and aortic arch detect changes in arterial pressure. When blood pressure rises, they increase firing to the medulla, reducing sympathetic activity and increasing parasympathetic tone, which lowers heart rate and promotes vasodilation to decrease blood pressure."

How do pressure and concentration gradients affect capillary exchange?

Capillary exchange depends on hydrostatic pressure pushing fluid out of capillaries and osmotic pressure pulling it back in. At the arterial end, filtration dominates; at the venous end, reabsorption occurs. These gradients allow nutrients, gases, and wastes to move between blood and tissues."

What mechanisms return blood to the right ventricle?

Venous return to the heart is aided by the skeletal muscle pump (muscle contractions push blood toward the heart), the respiratory pump (pressure changes during breathing move blood upward), venous valves preventing backflow, and sympathetic venoconstriction increasing venous tone."

How does blood volume influence blood pressure?

Increased blood volume raises venous return, stroke volume, and cardiac output, leading to higher blood pressure. Conversely, decreased volume lowers pressure. The kidneys regulate long-term volume via water and sodium balance under hormonal control by ADH, aldosterone, and ANP."

What is the difference between short-term and long-term blood pressure control?

"Short-term blood pressure control involves neural and hormonal mechanisms, such as the baroreceptor reflex and sympathetic activation, that adjust heart rate and vessel diameter. Long-term control depends on renal regulation of blood volume through the renin-angiotensin-aldosterone system, ADH, and atrial natriuretic peptide."

"What are thrombocytosis and thrombocytopenia?

an abnormally high platelet count, which may lead to excessive clotting. Thrombocytopenia is a low platelet count, which increases the risk of bleeding and bruising and may result from bone marrow failure, autoimmune diseases, or certain medications

What are erythrocytes and what is their function?

or red blood cells, are small biconcave cells that lack a nucleus and most organelles, allowing for maximum hemoglobin storage and gas exchange. Their primary function is to transport oxygen from the lungs to body tissues and carbon dioxide from tissues to the lungs. They live about 100–120 days before being removed by the spleen and liver."

What are the main transport functions of blood?

transports oxygen from the lungs to tissues, carbon dioxide from tissues to the lungs, nutrients from the digestive tract to cells, hormones from endocrine glands to target organs, and metabolic wastes to the kidneys for excretion."

How does erythropoietin maintain red blood cell levels?

maintains adequate red blood cell levels through a negative feedback mechanism. When oxygen levels drop, kidneys release EPO, stimulating the bone marrow to produce more RBCs. Once oxygen levels normalize, EPO secretion decreases."