Human Physiology: Vascular Response Quiz

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Questions and Answers

What is the primary immediate physiological response of a blood vessel once it has been severed?

Formation of a blood clot

Vascular constriction (correct)

Release of thromboxane A2

Increased blood flow through the vessel

Which factor contributes to vascular constriction after vessel trauma?

Epinephrine release

Increase in blood pH

Local myogenic spasm (correct)

Vasodilator chemicals

What role do platelets play in the process of hemostasis following a smaller vessel injury?

Inducing vasodilation

Production of clotting factors

Release of thromboxane A2 (correct)

Encapsulation of damaged tissue

What is one of the consequences of the smooth muscle contraction in a cut vessel?

Reduction of blood flow from the ruptured vessel Signup and view all the answers

Which of the following best describes the duration of the vascular spasm that occurs after vessel rupture?

It can last for several hours. Signup and view all the answers

What percentage of white blood cells are typically neutrophils?

60% Signup and view all the answers

Which type of white blood cell is most effective at engulfing large particles, such as malarial parasites?

Monocytes Signup and view all the answers

The process where white blood cells move toward an infection site due to chemical signals is called what?

Chemotaxis Signup and view all the answers

Which of the following types of white blood cells has the shortest lifespan in blood?

Neutrophils Signup and view all the answers

What is the main function of neutrophils and macrophages in the immune response?

Engulf and destroy pathogens Signup and view all the answers

Which characteristic best describes a basophil?

They release histamine and prevent blood coagulation. Signup and view all the answers

Which white blood cells are primarily responsible for the first line of defense against bacterial infections?

Neutrophils Signup and view all the answers

Diapedesis in white blood cells refers to which of the following processes?

The squeezing through the capillary walls Signup and view all the answers

What characterizes primary polycythemia?

RBC count above 14 millions/cu mm Signup and view all the answers

Which of the following is a physiological cause of secondary polycythemia?

Excessive exercise Signup and view all the answers

Which anemia is characterized by a low concentration of RBCs after rapid hemorrhage?

Blood loss anemia Signup and view all the answers

What is a common factor contributing to iron deficiency anemia?

Inadequate absorption of iron from the intestines Signup and view all the answers

Which type of anemia results from abnormal hemoglobin structures?

Sickle cell anemia Signup and view all the answers

Which factor can lead to primary polycythemia?

Bone marrow malignancy Signup and view all the answers

What blood disorder is characterized by a reduction in hemoglobin content?

Anemia Signup and view all the answers

Which condition is considered a pathological cause of secondary polycythemia?

Congenital heart disease Signup and view all the answers

What is the purpose of bilirubin binding to albumin?

To increase the solubility of the whole molecule Signup and view all the answers

What bilirubin level is associated with the onset of jaundice?

2 mg/dl Signup and view all the answers

Which type of cell is a megakaryocyte responsible for producing?

Platelets Signup and view all the answers

What is the normal range of bilirubin in blood?

1 to 16 µmol/l Signup and view all the answers

What type of cells are represented by CFUs in the blood film?

Proenitor cells Signup and view all the answers

What is the primary function of red blood cells?

Carrying oxygen and carbon dioxide Signup and view all the answers

Which blood component does not belong to the granular leukocytes category?

Monocyte Signup and view all the answers

Which cell type is a precursor to erythrocytes?

Colony-forming unit-erythrocyte (CFU-E) Signup and view all the answers

What initiates the formation of a blood clot following vessel damage?

Activator substances from the traumatized vascular wall Signup and view all the answers

How quickly does a clot begin to develop if the trauma to the vascular wall is severe?

15 to 20 seconds Signup and view all the answers

Which substances are primarily responsible for promoting blood coagulation?

Procoagulants Signup and view all the answers

Which step occurs last in the process of blood coagulation?

Joining of fibrinogen into a fibrin mesh Signup and view all the answers

What effect do anticoagulants generally have on blood in circulation?

They prevent blood from coagulating Signup and view all the answers

After how long does a clot typically retract to close a vessel further?

20 to 60 minutes Signup and view all the answers

What occurs when procoagulants are activated following vessel rupture?

A clot begins to form Signup and view all the answers

What role do platelets play in clot retraction?

They facilitate the sealing of the vessel Signup and view all the answers

What is the survival time of platelets in circulation?

8-12 days Signup and view all the answers

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

It acts as an adhesion bridge between collagen and platelets. Signup and view all the answers

Which of the following structures are majorly involved in platelet shape change and contraction?

Actin and myosin molecules Signup and view all the answers

Where are platelets mainly destroyed in the body?

Spleen Signup and view all the answers

What is the diameter of a platelet?

2-3 μm Signup and view all the answers

What is the primary function of the dense tubular system within platelets?

Storage of calcium ions (Ca2+) Signup and view all the answers

How does endothelial injury affect platelet activity?

It allows for aggregation and shape change. Signup and view all the answers

What condition can lead to the phenomenon of petechiae in individuals?

Low platelet count Signup and view all the answers

Study Notes

Blood Physiology

Blood is a connective tissue in fluid form; considered the fluid of life due to its role in transporting oxygen from the lungs to the body and carbon dioxide from the body to the lungs.
Blood volume:
- Average adult: 5 liters
- Newborn: 450 ml
- Increases during growth to reach 5 liters at puberty.
- In females, slightly less (about 4.5 liters).
- Approximately 8% of total body weight in a healthy young adult (about 70 kg).
Blood composition:
- Cellular components:
  - Red blood cells (erythrocytes)
  - White blood cells (leukocytes)
  - Platelets (thrombocytes)
- Plasma (ECF):
  - Primarily water (98%)
  - Contains ions and plasma proteins (e.g., albumin, globulin, fibrinogen).
  - Same ionic composition as interstitial fluid.

Functions of Blood

Transport: oxygen, carbon dioxide, nutrients, hormones, waste products.
Homeostasis: regulates body temperature and ECF pH.
Protection against infections: white blood cells and antibodies.
Blood clotting: prevents blood loss.

Blood Cell Formation

Erythropoiesis: formation of red blood cells (RBCs).
Leucopoiesis: formation of white blood cells (WBCs).
Thrombopoiesis: formation of platelets.

Hematopoiesis

In-utero:
- Early weeks: yolk sac
- Middle trimester: liver, spleen, lymph nodes
- Last months: bone marrow of all bones
After birth:
- Bone marrow of flat bones continues RBC production
- Shaft of long bones stop producing RBCs at puberty, while epiphyses continue.
Locations of active bone marrow in adults: axial skeleton, pelvic and pectoral girdles, proximal epiphyses of the humerus and femur.

Normal Bone Marrow Conversion

Infant (<1 year): predominantly red marrow.
Childhood (1-10 years): red marrow gradually converts to yellow marrow centrally.
Adolescent (10-20 years): continued conversion.
Adult (>25 years): predominantly yellow marrow, with remaining red marrow in specific locations, such as flat bones and the epiphyses. Red marrow is active bone marrow. Yellow marrow is inactive bone marrow.

Blood Composition (Summary)

Approximately 55% plasma and 45% formed elements:
- Formed elements:
  - RBCs (4.2-6.2 million/mm³)
  - WBCs (5-9 thousand/mm³)
  - Platelets (250-400 thousand/mm³)
- Plasma:
  - Approximately 91% water
  - Proteins (7%):
    - Albumins (58%)
    - Globulins (38%)
    - Fibrinogens (4%)
  - Other solutes (2%):
    - Nutrients, electrolytes
    - Waste products, gases
    - Regulatory substances

Blood Cell Characteristics

RBCs:
- Biconcave discs, 7.5 µm in diameter
- Flexible membranes, no mitochondria or ribosomes, anaerobic glycolysis
- Life span: 120 days
- Normal hemoglobin (Hb): 14-16 g/dL
- Count: 4.7-5.2 million/mm³
WBCs: diverse types (granulocytes and agranulocytes), with different functions in immunity. - Normal count: 4000-11,000 per µl - Granulocytes: neutrophils, eosinophils, basophils - Agranulocytes: lymphocytes, monocytes
Platelets
- Fragments of megakaryocytes
- Important in blood clotting
- Count: 150,000-450,000 per µl

Hemoglobin

Complex protein contained in red blood cells, responsible for oxygen transport.
Composed of four protein globin chains and four heme groups each, containing iron.
Different types of hemoglobin exist.
The concentration of Iron in hemoglobin is approximately 65%.

Erythropoiesis

Production of red blood cells (RBCs).
Stimulated by erythropoietin (EPO), a hormone produced mainly in the kidneys in response to low oxygen levels (hypoxia).
Hypoxia can be caused by low RBC count, hemorrhage, high altitude, prolonged heart failure, or lung disease.
Also regulated by other factors such as vitamins (B12, folic acid), iron, and protein intake.

Erythrocyte Disorders

Polycythemia: increased RBC count (primary and secondary).
Anemia: decreased RBC count, hemoglobin content, or packed cell volume. Subtypes include:
- Blood loss anemia
- Iron deficiency anemia
- Pernicious anemia
- Hemolytic anemia
- Aplastic anemia
- Thalassemia
- Sickle cell anemia

Jaundice

Yellowing of the skin and eyes due to high bilirubin levels in the blood.
- Pre-hepatic (hemolytic): excessive RBC breakdown
- Intrahepatic (hepatic): liver dysfunction.
- Post-hepatic (obstructive): blockage of bile duct.
Types and causes of jaundice
Bilirubin metabolism
Plasma transport of bilirubin

White Blood Cells (WBCs)

Mobile cellular immune components (4000-11000/µL)
- Granulocytes:
  - Neutrophils: primary phagocytes (60%)
  - Eosinophils: defense against parasitic infections (2%)
  - Basophils: release histamine and heparin (0.4%)
- Agranulocytes:
  - Lymphocytes: crucial for acquired immunity (30%)
  - Monocytes: develop into macrophages in tissues (5%), powerful phagocytes.

WBC Function

Phagocytosis: engulf and destroy pathogens
Diapedesis: migration through capillary walls
Chemotaxis: movement toward a source of chemical attractants
Other functions vary by specific cell type (e.g., antibody production by B lymphocytes).

Blood Clotting

Hemostasis: stopping blood loss from a damaged vessel.
Mechanisms:
- Vascular spasm
- Platelet plug formation
- Blood clot formation (coagulation)
Clotting Factors:
- Extrinsic Pathway
- Intrinsic Pathway
Anticoagulants:
- Endothelial surface factors (e.g., thrombomodulin)
- Antithrombin III

Platelet Structure and Function

Fragments of megakaryocytes (large cells in bone marrow)
Important in hemostasis; form platelet plugs.
150,000-450,000 /µl in blood.

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Description

Test your knowledge on the immediate physiological responses of blood vessels and the role of white blood cells in hemostasis and immune response. This quiz covers critical concepts related to vascular constriction, platelet function, and the characteristics of various leukocytes involved in the body’s defense mechanisms.