Human Physiology: Blood Clotting and Disorders

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Questions and Answers

What is the role of thrombin in the clotting process?

It activates prothrombin.

It catalyzes the polymerization of fibrinogen into fibrin fibers. (correct)

It forms prothrombin activator.

It breaks down fibrinogen.

Which pathway is triggered by trauma to the vascular wall?

Intrinsic pathway

Common pathway

Extrinsic pathway (correct)

Fibrinogen pathway

What initiates the intrinsic pathway of clotting?

Activation of blood-clotting factors by thrombin

Exposure to external tissue damage

Ingestion of prothrombin

Trauma to blood cells or exposure to collagen (correct)

What is primarily involved in the clotting process?

Blood-clotting factors Signup and view all the answers

What is the result of thrombin's action on fibrinogen?

Polymerization into insoluble fibrin Signup and view all the answers

What role do eosinophils play in allergic reactions?

They attach to parasites and release substances that kill them. Signup and view all the answers

Which type of lymphocyte is responsible for producing antibodies?

B lymphocytes Signup and view all the answers

What is leukocytosis?

An increase in white blood cells in response to infection. Signup and view all the answers

Which process prevents blood loss?

Hemostasis Signup and view all the answers

What characterizes leukemia?

An excessive increase in white blood cells with no apparent reason. Signup and view all the answers

What is the primary characteristic of polycythemia vera?

Increase in WBC count above 24,000/cu mm Signup and view all the answers

Which of the following is NOT a cause of secondary polycythemia?

Aplastic anemia Signup and view all the answers

What condition is characterized by a decrease in hemoglobin content?

Hemolytic anemia Signup and view all the answers

Which of the following is a physiologic condition leading to secondary polycythemia?

Exercise Signup and view all the answers

What type of anemia is caused by malnutrition related to low vitamin B12 levels?

Pernicious anemia Signup and view all the answers

In respiratory disorders, what does hypoxia stimulate the secretion of?

Erythropoietin Signup and view all the answers

Which type of anemia results from rapid hemorrhage, leading to a low concentration of RBCs?

Blood loss anemia Signup and view all the answers

What is a common cause of pulmonary emphysema?

Nicotine consumption Signup and view all the answers

What type of anemia is characterized by RBCs that are smaller than normal and have little hemoglobin?

Microcytic hypochromic anemia Signup and view all the answers

Which deficiency is NOT associated with microcytic anemia?

Vitamin B12 deficiency Signup and view all the answers

Sickle cell anemia is characterized by RBCs that:

Contain hemoglobin S Signup and view all the answers

What happens to Rh-positive RBCs in erythroblastosis fetalis?

They are attacked by the mother's antibodies Signup and view all the answers

Which of the following is NOT a type of hemolytic anemia?

Iron deficiency anemia Signup and view all the answers

In hereditary spherocytosis, what is the ratio of surface to volume of RBCs?

Smaller than 1 Signup and view all the answers

What characterizes megaloblastic anemia?

Deficiency of vitamin B12 and folic acid Signup and view all the answers

What is the diameter range of megakaryocytes?

35-160 μm Signup and view all the answers

What is the primary site for storage of Ca2+ within platelets?

Dense tubular system Signup and view all the answers

What is the typical platelet survival time?

8-12 days Signup and view all the answers

What role does von Willebrand factor (vWF) play in platelet function?

It serves as an adhesion bridge Signup and view all the answers

How many platelets are typically found in a cubic millimeter of blood?

150,000-450,000 Signup and view all the answers

What happens when there is endothelial injury in a blood vessel?

Platelet adhesion and activation increase Signup and view all the answers

What factors are released by activated platelets to recruit additional platelets?

Adenosine diphosphate (ADP) and thromboxane A2 (TXA2) Signup and view all the answers

What can occur if a person has a low platelet count?

Development of petechiae Signup and view all the answers

What is the first step in the process of blood hemostasis?

Vascular spasms Signup and view all the answers

Which factor is NOT required for the formation of a platelet plug?

Prothrombin Signup and view all the answers

Which sequence correctly describes the phases of coagulation?

Formation of prothrombinase, conversion of prothrombin to thrombin, conversion of fibrinogen to fibrin Signup and view all the answers

What compound is released by platelets during the aggregation process?

Serotonin Signup and view all the answers

What is the origin of platelets?

Megakaryocyte Signup and view all the answers

Which of the following is the final product of the coagulation cascade?

Fibrin Signup and view all the answers

What happens to the fibrin clot after it has formed?

It is slowly dissolved by plasmin. Signup and view all the answers

Which of the following factors is involved in the formation of prothrombinase?

Tissue factor Signup and view all the answers

Study Notes

Blood Physiology Overview

Blood is a connective tissue in fluid form, considered the "fluid of life" due to its role in transporting oxygen and carbon dioxide throughout the body.

Blood Properties

Color: Arterial blood is scarlet red (due to oxygenated hemoglobin), and venous blood is purple-red (due to higher carbon dioxide levels).
Volume: An average adult has 5 liters of blood, while a newborn has 450mL. Blood volume increases during growth and reaches adult levels around puberty. In females, the average volume is slightly lower (around 4.5 liters). The volume is approximately 8% of body weight in a healthy adult.

Blood Composition

Cellular Components: Erythrocytes (red blood cells), leukocytes (white blood cells), and thrombocytes (platelets).
Plasma: Composed primarily of water (about 98%), ions, and plasma proteins (e.g., albumin, globulins, fibrinogen). It has a similar ionic composition to interstitial fluid.

Functions of Blood

Transport: Oxygen, carbon dioxide, nutrients, hormones, and waste products.
Homeostasis: Regulation of body temperature and extracellular fluid (ECF) pH.
Protection: Defense against infections by white blood cells and antibodies.
Clot Formation: Prevents blood loss.

Blood Cell Formation

Erythropoiesis: Formation of red blood cells (RBCs)
Leucopoiesis: Formation of white blood cells (WBCs)
Thrombopoiesis: Formation of platelets (thrombocytes)

Hematopoiesis

Blood cell formation begins early in embryonic development and continues throughout life.
Locations of red blood cell (RBC) production change during development (yolk sac, liver, spleen, and bone marrow).
In adults, red bone marrow in the axial skeleton, pelvic and pectoral girdles, and proximal epiphyses of long bones is the primary site of RBC production.. Different bones produce RBCs at different ages.

Blood Cell Characteristics

Red Blood Cells (Erythrocytes):
- Biconcave disks 7.5 micrometers across
- Flexible cell membrane
- No mitochondria or ribosomes (anaerobic glycolysis)
- Life span: 120 days.
- Normal count of 4.7–5.2 million per mm³.
- Hemoglobin (Hb) concentration of 14–16 g/dL.
Function: Transport of O2 and CO2, and acts as a buffer.
Platelets:
- Irregular shape, smaller than RBCs.
- 150,000 - 450,000 per mm³,
- Short lifespan 8-12 days
- Formed from the cytoplasm of megakaryocytes.
- Crucial role in blood clotting.
White Blood Cells (Leukocytes):
- Various types with different functions in the immune system and
- protective mechanisms.
- Granulocytes: neutrophils (most common), eosinophils, basophils.
- Agranulocytes: lymphocytes, monocytes (developing to macrophages).
- Normal white blood cell count: 4,000 – 11,000/µL

RBC Development (Erythropoiesis)

RBC development is characterized by:
- Decrease in cell size.
- Disappearance of the nucleus.
- Appearance of hemoglobin (Hb).
Controlled by erythropoietin (EPO), a hormone primarily produced by the kidney in response to low oxygen levels in the blood (hypoxia).

Erythropoietin (EPO)

EPO is a glycoprotein.
Primarily produced by the kidney in response to hypoxia (low oxygen), and to a small degree by the liver.
Stimulates the growth of early stem cells, but does not affect red blood cell (RBC) maturation.
Its level can be measured in plasma and urine.

Hemoglobin

Composed of four globin protein chains, each with a heme group that contains iron.
Iron is important to hemoglobin, myoglobin, and other structures ( ~65% of total iron in hemoglobin).
Normal hemoglobin types include Hb A (most adult form), Hb A2, and Hb F (fetal).

Platelet Formation and Structure

Platelets are fragments of cytoplasm from megakaryocytes.
Megakaryocytes are large cells with multiple DNA copies in the nucleus.
Platelet count (normal) 150,000-450,000/mm³
Platelets have membrane glycoproteins that serve as receptors, mediate adhesion and contraction.
Platelet production is highly regulated.

Hemostasis

A series of mechanisms that stop blood loss from damaged blood vessels.
Three main phases:
- Vasoconstriction: Immediate contraction of the damaged blood vessel to reduce blood flow.
- Platelet plug formation: Platelets stick together to form a temporary plug.
- Coagulation: Formation of a stable blood clot through a series of reactions involving multiple blood clotting factors.

Blood Coagulation

A complex process initiated by the intrinsic or extrinsic pathways.
Involves multiple coagulation factors (proteins) that act in a cascading manner.
The final common pathway leads to the conversion of fibrinogen to fibrin, forming a mesh that traps blood cells and platelets to form a clot.

Anticoagulants

Substances that inhibit blood clotting. Important to prevent clots in undamaged blood vessels.
Important intravascular system factors to prevent clot formation in the normal vascular system include endothelial surface factors like thrombomodulin, prostacyclin and nitric oxide (NO).
Anticoagulants in vitro like EDTA, oxalate, heparin, sodium citrate, and sodium fluoride/potassium oxalate are used to prevent clotting of blood samples for testing purposes.

Clot Retraction

Fibrin fibers shorten, pulling the edges of the damaged vessel together to further reduce further bleeding. Involves the interaction of platelets.

Fibrinolysis

The breakdown of a blood clot following a healing process.
Activated by plasminogen-plasmin sequence.

Jaundice

Condition characterized by a yellowish pigmentation of the skin and eyes.
Occurs when there is excessive bilirubin in the blood (hyperbilirubinemia).
Bilirubin is a byproduct of red blood cell breakdown that is normally processed and excreted by the liver.
Types of jaundice include prehepatic, intrahepatic, and posthepatic, depending on the cause of the bilirubin buildup.

Anemia

A condition characterized by a decrease in the oxygen-carrying capacity of blood due to a deficiency or abnormality in red blood cells (RBCs) or hemoglobin.
Several types of anemia exist, caused by various factors like blood loss, malnutrition, genetic disorders, and bone marrow problems. The result is reduced numbers of RBCs, reduced hemoglobin, and a decreased packed cell volume.

Increased Blood Viscosity and Anemia/Polycythemia

Increased blood viscosity may occur in conditions like polycythemia, causing sluggish blood flow. In anemia, decreased red blood cell count and hemoglobin reduce blood viscosity, possibly increasing blood flow and cardiac output to compensate for the reduced carrying capacity.

WBC Disorders

Leukocytosis: Increased white blood cell count due to infection
Leukemia: Uncontrolled abnormal increase in white blood cell production, causing various complications.

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Description

This quiz focuses on the physiological processes involved in blood clotting, including the role of thrombin and various pathways of clot formation. It also delves into blood disorders such as leukemia and polycythemia, offering insights into their characteristics and impacts on health.