Human Physiology Week 8 - Blood (Notes)

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Questions and Answers

What initiates the expression of EPO in the kidneys?

Hypoxia detected by juxtaglomerular cells (correct)

Inflammatory cytokines released

Increased oxygen levels in blood

Increase in blood cell count

Which cell type does a hematopoietic stem cell differentiate into to produce platelets?

Lymphoid progenitor cell

Megakaryoblast (correct)

Basophil

Proerythroblast

What is the primary function of the spleen in relation to erythrocytes?

Filtering and removing older or abnormal red blood cells (correct)

Regulating blood glucose levels

Producing new red blood cells

Storing excess blood components

What causes the formation of reticulocytes to increase in the bloodstream?

Increased demand for red blood cells due to blood loss or anemia Signup and view all the answers

What is considered the normal range for hematocrit levels in adult males?

40-50% Signup and view all the answers

What is the role of thrombosis in relation to blood flow?

It assists in the formation of blood clots. Signup and view all the answers

Which substance is primarily responsible for converting fibrinogen into fibrin during coagulation?

Thrombin Signup and view all the answers

What factor significantly contributes to hypercoagulability in patients?

Cytokines from cancer cells Signup and view all the answers

What is a primary clinical sign of Deep Vein Thrombosis (DVT)?

Calf soreness Signup and view all the answers

Which condition could result from excessive clotting in the body?

Pulmonary embolism Signup and view all the answers

What does impaired conversion of prothrombin into thrombin lead to?

Inadequate clotting response Signup and view all the answers

What is a potential risk associated with anticoagulant therapy?

Excessive bruising Signup and view all the answers

What is a critical hematocrit level indicating acute trauma?

Under 20 Signup and view all the answers

What is the primary function of hemoglobin in red blood cells?

Transporting oxygen Signup and view all the answers

Which factor helps to decrease total peripheral resistance during exercise?

Dilation of blood vessels Signup and view all the answers

What condition is characterized by the buildup of bilirubin in the blood?

Jaundice Signup and view all the answers

Which type of anemia is specifically associated with chronic inflammation affecting iron metabolism?

Anemia of chronic disease Signup and view all the answers

What form of iron can be directly absorbed by the intestines?

Fe2+ Signup and view all the answers

What can happen as a result of effective iron absorption and utilization during pregnancy?

Improved oxygen delivery for the fetus Signup and view all the answers

Which condition can result from the breakdown of red blood cells leading to excessive bilirubin production?

Hemolytic anemia Signup and view all the answers

Study Notes

Hematopoiesis

Erythrocytes (red blood cells): transport oxygen and are anucleate (lack a nucleus), making them flexible for passage through capillaries.
Lymphocytes (white blood cells): involved in immune response.
- B lymphocytes: produce antibodies.
- T lymphocytes: directly attack infected cells.
- Plasma cells: secrete antibodies.
- Natural killer cells: target infected cells and tumor cells.
Basophils: release histamine and heparin, involved in allergic reactions and inflammation.
Neutrophils: first responders to infection, phagocytose bacteria.
Eosinophils: target parasites and allergens.
Macrophages: engulf and destroy pathogens and cellular debris.
Platelets: cell fragments involved in blood clotting.
Hematopoietic stem cells: can differentiate into all blood cell types.
- Cytokines signal hematopoietic stem cells toward specific cell lineages, e.g., lymphoid progenitor cells (for lymphocytes) or myeloid progenitor cells (for other blood cells).
Megakaryoblast: differentiates into megakaryocyte, which fragments into platelets.
Proerythroblasts: precursors to erythrocytes.

Hematopoiesis Sites

Red blood cells: form in the liver early in life, then shift to the spleen later.
Bone marrow: primary site for red blood cell and some white blood cell production.
- Major sites: vertebrae, pelvis, sternum, ribs.
- Long bones contribute less as we age.
Lymph nodes: primarily for white blood cell formation.
Extramedullary hematopoiesis: production of blood cells outside the bone marrow, e.g., in the liver and spleen, often occurring in response to pathological conditions or deficiencies.
Erythropoietin (EPO): hormone primarily responsible for red blood cell production.
- Juxtaglomerular cells in the kidney sense low oxygen levels and initiate EPO expression.
- EPO stimulates differentiation of hematopoietic stem cells into proerythroblasts.
Reticulocyte: immature red blood cell released into circulation, indicating increased erythropoiesis.
Lifespan of erythrocytes: about 120 days, after which they are removed by the spleen.

The Spleen

Filters out old and dysfunctional red blood cells.
Splenomegaly: enlarged spleen, often caused by the accumulation of abnormal red blood cells, as in sickle cell disease.

Hematocrit

Percentage of red blood cells in blood.
Normal range: 35-45%, with females typically having lower hematocrit than males.
Dehydration can lead to higher hematocrit due to decreased plasma volume.
Low hematocrit:
- Acute blood loss: dangerous, requiring immediate intervention
- Chronic anemia: body can adapt but may impair performance.
Exercise:
- Increased EPO production leads to higher hematocrit and oxygen carrying capacity.
- However, also results in increased blood viscosity.
- Increased plasma volume in athletes helps dilute blood, lowering total peripheral resistance.

Hemoglobin

Major oxygen transport molecule.
Heme group: contains an iron ion that binds to oxygen.
One hemoglobin molecule has four heme groups, allowing for the binding of four oxygen molecules.
Red blood cells: contain around 270 million hemoglobin molecules.

Iron Metabolism

Forms of iron:
- Fe2+ (ferrous): heme iron, readily absorbed from animal products.
- Fe3+ (ferric): non-heme iron, found in plants and requires conversion to Fe2+ for absorption.
Ferritin: storage form of iron inside intestinal cells.
Transferrin: protein that transports iron in the bloodstream.
Hepcidin: hormone that regulates iron storage in the liver.

Iron Deficiency

Causes:
- Blood loss: trauma, surgery, cancer, etc.
- Intravascular hemolysis: breakdown of blood cells.
- Malabsorption: celiac disease, etc.
- Inadequate intake: especially crucial during infancy, adolescence, and pregnancy.

Jaundice

Yellowish discoloration of skin, eyes, and mucous membranes due to bilirubin buildup.
Unconjugated bilirubin: released from breakdown of heme, binds to albumin.
Conjugated bilirubin: chemically modified in the liver, making it excretable.
Types of jaundice:
- Pre-hepatic: due to excessive destruction of red blood cells.
- Hepatic: liver dysfunction leads to impaired bilirubin conjugation.
- Post-hepatic: blockage of bile ducts prevents bilirubin excretion.

Anemia

Condition characterized by fewer or dysfunctional red blood cells.
Types of anemia:
- Hypoproliferative anemias: decreased red blood cell production or production of poor quality cells.
  - Aplastic anemia: affects both red and white blood cells.
  - B12 and B9 deficiency: leads to megaloblastic anemia (large, abnormal red blood cells).
  - Anemia of chronic disease: iron metabolism is impaired.
- Hemolytic anemias: destruction of red blood cells.
- Blood loss anemia: loss of blood through injury or bleeding.
- Dilution anemia (also known as Pseudoanemia): reduced hematocrit due to dilution of red blood cells.
Mechanisms of anemia:
- Impaired red blood cell production due to bone marrow disease, lack of raw materials (e.g., iron deficiency), etc.

Clinical Application of Anemia

Impaired oxygen delivery to tissues: leads to fatigue, exercise intolerance, etc.
Increased cardiac output: as the body attempts to compensate for low oxygen levels.
Respiratory impairment: due to reduced oxygen delivery in the body.

Exogenous EPO Use and Misuse

Erythropoietin (EPO): drug used to treat anemia in patients with cancer or chronic diseases.
EPO abuse in athletes: can increase red blood cell count, improving endurance, but increases blood viscosity, which is dangerous.

Coagulation

Process forming a blood clot to stop bleeding.
Initiated by injury:
- Endothelial cells are disrupted, exposing collagen.
- Endothelin (vasoconstrictor) is released, reducing blood flow at the injury site.
- Platelets adhere to exposed collagen and release cytokines to recruit more platelets (primary hemostasis).
Secondary hemostasis:
- Fibrin is released and reinforces the platelet plug.
Thrombus: blood clot composed of trapped blood cells and fibrin.
Prothrombin: precursor to thrombin, which activates fibrinogen into fibrin.
Vitamin K: essential for proper clotting.
Plasmin: dissolves fibrin clots.
Plasminogen: precursor to plasmin.
Tissue plasminogen activator (tPA): converts plasminogen into plasmin.
Thrombin: releases plasminogen activator inhibitors (PAI)
Thrombosis: formation of a blood clot within a blood vessel.
Hypercoagulability: increased tendency to clot.
Abnormal blood flow: stasis (pooling) and turbulent flow can increase the risk of thrombosis.

Coagulation Balance

Pro-thrombotic: increased tendency to clot.
Anti-thrombotic: decreased tendency to clot.

Deep Vein Thrombosis (DVT)

Blood clot in a deep vein, often in the legs.
Symptoms: pain, swelling, redness, calf soreness.
Can travel to lungs (pulmonary embolism), heart (heart attack), or brain (stroke).
Risk factors: stasis, dehydration, inflammation, pregnancy.

Anticoagulant Therapy

Blood thinners to reduce clotting risk.
Side effects: increased bruising, difficulty stopping bleeding.

Thrombus: blood clot within a vessel.
Embolism: blockage of a blood vessel.
Thromboembolism: clot that travels from one site to another.
Hypocoagulation: reduced blood clotting ability.
Petechiae: small pinpoint hemorrhages under the skin.
Ecchymoses: larger bruises.
Hematoma: localized collection of blood outside blood vessels.

Case Study: John

55-year-old male with chronic kidney disease (CKD) stage 3, hypertension, and type 2 diabetes.
Sedentary and overweight.
Takes ACE inhibitor for hypertension, metformin and insulin for diabetes.
Exercise plan: walking 30 minutes 5 times a week, light weightlifting 2 times a week, daily stretching.
Considerations for exercise program:
- Chronic kidney disease: may limit exercise tolerance, increased risk of cardiovascular events, orthostatic hypotension.
- Hypertension and diabetes: monitor blood pressure and glucose levels closely during exercise.
Potential benefits of exercise:
- Improved cardiovascular health, weight loss, better blood sugar control, overall well-being.
Monitoring during exercise: heart rate, perceived exertion (RPE), blood pressure, oxygen saturation.
Comparison to healthy individuals: John may experience faster fatigue, altered blood pressure responses, and muscle weakness.
Precautions: orthostatic hypotension, oxygen levels, hydration, blood glucose monitoring.
Progress monitoring: track changes in blood pressure, glucose levels, exercise intensity, and tolerance over time.
Patient education: crucial for ensuring adherence and understanding exercise limitations.
Long-term management: improved circulation, filtration, and glucose control can help manage CKD.
Impact on quality of life and mental health: improved physical function, confidence, and mental well-being.

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Description

Test your knowledge on hematopoiesis and the various types of blood cells, including erythrocytes, lymphocytes, and platelets. This quiz covers their functions, characteristics, and roles in the immune system. Perfect for students of biology or those interested in human physiology.