Human Physiology: Erythrocytes and Hematopoiesis

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Questions and Answers

What is the shape of erythrocytes and why is it beneficial?

Biconcave shape, enhances gas exchange due to greater surface area (correct)

Biconcave shape, increases resistance in blood flow

Flat shape, reduces cell size

Spherical shape, provides structural support

What percentage of a red blood cell's volume is comprised of hemoglobin?

100%

50%

97% (correct)

80%

Why do erythrocytes not contain mitochondria?

To enhance structural integrity

To prevent consumption of absorbed oxygen (correct)

To increase energy production

To allow for aerobic respiration

What component of hemoglobin carries oxygen?

Iron atom in heme Signup and view all the answers

What is the role of carbonic anhydrase in erythrocytes?

Catalyzes the conversion of carbon dioxide to bicarbonate Signup and view all the answers

Which stage of erythropoiesis involves the formation of a concave shape in erythrocytes?

Orthochromatic erythroblast Signup and view all the answers

Where is hematopoiesis primarily located in adults?

In red bone marrow of the axial skeleton and other areas Signup and view all the answers

What is the function of reticulocytes in the bloodstream?

Indicate the rate of red blood cell formation Signup and view all the answers

What is the primary function of erythrocytes?

Transporting oxygen and carbon dioxide Signup and view all the answers

Which component of blood is primarily responsible for maintaining osmotic pressure?

Albumin Signup and view all the answers

What percentage of blood is typically composed of plasma?

Approximately 55% Signup and view all the answers

Which of the following best describes platelets?

Cell fragments involved in clotting Signup and view all the answers

What condition is prevented by hemostasis?

Blood loss Signup and view all the answers

What is the normal hematocrit range for adult males?

47 ± 5% Signup and view all the answers

Which type of blood cell has no nuclei or organelles?

Erythrocytes Signup and view all the answers

Which is a key feature of plasma that contributes to its ability to transport substances?

Dissolved proteins and solutes Signup and view all the answers

What color is blood that is rich in oxygen?

Scarlet red Signup and view all the answers

What is the function of leukocytes in the blood?

Providing immunity Signup and view all the answers

What is the primary function of erythropoietin in erythropoiesis?

To regulate the balance between production and destruction of RBCs Signup and view all the answers

Which dietary component is primarily needed for the synthesis of hemoglobin in red blood cells?

Iron Signup and view all the answers

What risks are associated with athletes using artificial erythropoietin (EPO)?

Dehydration and increased blood viscosity Signup and view all the answers

How is iron transported in the blood?

Bound to transferrin Signup and view all the answers

Which of the following is NOT a consequence of artificially increasing hematocrit (hct) with EPO?

Improved oxygen delivery to tissues Signup and view all the answers

What percentage of iron is stored in the liver, spleen, and bone marrow?

35% Signup and view all the answers

Which plant sources are high in iron?

Beans and lentils Signup and view all the answers

What percentage of red blood cells is produced per second in a healthy adult?

<blockquote> 2 million RBC/sec </blockquote> Signup and view all the answers

What is hemolytic anemia primarily caused by?

Premature RBC lysis Signup and view all the answers

Which form of anemia is characterized by a mutation in the beta chain of hemoglobin?

Sickle-cell anemia Signup and view all the answers

How does hydroxyurea help in the treatment of sickle-cell anemia?

By inducing the formation of fetal hemoglobin Signup and view all the answers

What condition is associated with an excess of red blood cells leading to increased blood viscosity?

Polycythemia vera Signup and view all the answers

What initiates the process of thrombopoiesis?

Thrombopoietin Signup and view all the answers

What is the primary role of platelets in the body?

Clotting of blood Signup and view all the answers

Which of the following conditions can lead to secondary polycythemia?

Increased EPO production due to low oxygen levels Signup and view all the answers

Which component prevents platelets from becoming activated while in circulation?

Nitric oxide (NO) Signup and view all the answers

What is the primary role of vitamin B12 and folic acid in the body?

DNA synthesis for rapidly dividing cells Signup and view all the answers

What happens to old red blood cells (RBCs) once they become fragile?

They are trapped in smaller circulatory channels and can be engulfed by macrophages Signup and view all the answers

What is a common symptom of anemia?

Conjunctival pallor Signup and view all the answers

In pernicious anemia, which deficiency leads to the enlargement of red blood cells?

Vitamin B12 Signup and view all the answers

How is renal anemia primarily treated?

Synthetic erythropoietin (EPO) Signup and view all the answers

Which type of anemia is characterized by rapid blood loss due to a wound?

Acute hemorrhagic anemia Signup and view all the answers

What is the process by which iron from dying red blood cells is made available for reuse in the body?

Binding to ferritin or hemosiderin Signup and view all the answers

What is the consequence of iron deficiency in red blood cells?

Formation of small, pale red blood cells (microcytes) Signup and view all the answers

Study Notes

Anatomy & Physiology I - Lecture 11 - Blood (Part 1)

Course: ANP 1105A
Topic: Basic cellular physiology, anatomy, and physiology of the cardiovascular, lymphatic, and respiratory systems.
Specific focus: Blood (part 1)
Presenter: Dr. Stephen Gee

Readings - Marieb and Hoehn 11th Edition, Chapter 17 (pp. 642-666)

Blood functions: Transport, regulation, and protection
Blood composition: Plasma and formed elements
Erythrocytes (red blood cells): Crucial for oxygen and carbon dioxide transport
Platelets: Cell fragments aiding in stopping bleeding
Hemostasis: Prevents blood loss
Transfusion: Replaces lost blood

Overview: Chapter 17 Blood

Blood as the body's internal transport system
Blood function questions: What does blood do?, What is blood made of?, What happens when a blood vessel breaks?, How do we replace blood in an emergency?, What can the study of blood tell us about a patient?
Blood composition: Plasma, formed elements (erythrocytes, leukocytes, and platelets)

Blood - Internal Transport System

Blood is the life-sustaining transport vehicle of the cardiovascular system
Circulatory pathways: Pulmonary circulation and systemic circulation
Components: Heart, arteries, veins, and capillaries
Oxygen-rich (red) and oxygen-poor (blue) blood

Functions of Blood

Transport: Oxygen, nutrients, metabolic wastes (CO2 and urea), hormones from endocrine glands to targets.
Regulation: Body temperature, heat distribution, pH buffering (bicarbonate), fluid volume.
Protection: Proteins and platelets initiate clot formation to prevent blood loss, antibodies, complement proteins, and white blood cells fight infection.

Composition of Blood

Fluid connective tissue
Matrix: Plasma (liquid portion)
Cells: Formed elements (erythrocytes, leukocytes, platelets)
Plasma components: Amino acids, nutrients, proteins (albumins, globulins, fibrinogen), gases, electrolytes, nitrogenous waste
Formed elements: Platelets, leukocytes (granulocytes and agranulocytes), erythrocytes

Centrifugation of Whole Blood

Yields three layers: Hematocrit, Buffy coat, Plasma
Hematocrit: Normal values for males and females (M: 47 +/- 5%; F: 42 +/- 5%).
Buffy coat: Thin, whitish layer between RBCs and plasma (low percentage, < 1%)
Plasma: ~55% of whole blood (most abundant portion).

Physical Characteristics and Volume

Sticky, opaque fluid with a metallic taste
Color varies with oxygen content (oxygen-rich: scarlet; oxygen-poor: dark red)
Slightly alkaline pH (7.35-7.45)
Denser than water, 5x viscosity (mostly due to RBCs)
~8% of total body weight
Average volumes: Males (5-6 L), Females (4-5 L)

Blood Plasma

Straw-colored, sticky fluid (mostly water - 90%)
100 dissolved solutes
Major components (plasma proteins, electrolytes, nutrients, gases, hormones, wastes, and inorganic ions)
Plasma proteins are the most abundant solutes
Albumin (60%): Plasma protein, carrier, blood buffer, contributes to plasma osmotic pressure.

Formed Elements

RBCs (erythrocytes), WBCs (leukocytes), platelets
Only WBCs are complete cells
RBCs lack nuclei and organelles
Platelets are cell fragments
Survival in bloodstream (days)
Originate in bone marrow, do not divide.

Erythrocytes - Structural Characteristics

Small diameter (7.5 µm) cells
Biconcave disc shape, anucleate, and no organelles
Contain hemoglobin (Hb) for gas transport
RBC diameters exceed some capillaries (spectrin and other PM proteins allow flexibility)
Features for efficient gas transport (biconcave shape - large surface area to volume ratio for gas exchange, and 97% Hb)
No mitochondria (anaerobic metabolism)

Erythrocyte Function

Respiratory gas transport: Hemoglobin (Hb) binds reversibly with oxygen.
Normal values for Hb concentration (Males 13-18 g/100ml; Females 12-16 g/100ml)
Hemoglobin (Hb) structure: Heme pigment bound to Globin protein (α and β chains)
Hb binds oxygen in lungs (Oxyhemoglobin); unloads it in tissues (Deoxyhemoglobin or reduced hemoglobin); and binds carbon dioxide in tissues (carbaminohemoglobin).

Erythropoiesis

Formation of red blood cells
Occurs in red bone marrow
Regulated by Erythropoietin (EPO) from Kidneys
Stages: Hematopoietic stem cells to committed cells, to immature forms and mature forms through ribosome synthesis and hemoglobin accumulation.

Regulation of RBC Production by Erythropoietin

Kidneys regulate erythropoiesis through EPO (erythropoietin)
EPO is produced in response to low oxygen, such as at high altitudes; some athletes artificially increase EPO for athletic performance, but health risks possible
Feedback loop maintaining consistent RBC production.

Erythropoiesis Dietary Requirements

Nutritional needs for RBC production, including iron, amino acids, lipids, and carbohydrates.
Iron availability from diet; stored in cells as ferritin or hemosiderin, and transported in blood as transferrin.
Vitamins B12 and folic acid for DNA synthesis in RBC development.

Erythrocyte Fate

Life span: 100-120 days
Old RBC breakdown (heme, iron, globin separated)
Heme is degraded to bilirubin; liver secretes bilirubin into intestines; converted to stercobilin (excreted via feces)
Globin is metabolized to amino acids for reuse.

Erythrocyte Disorders

Anemia (too few RBCs) and Polycythemia (too many RBCs)
Anemia types: Blood loss (acute or chronic); insufficient production; too much destruction.
Polycythemia types: Primary (bone marrow cancer); Secondary (due to low oxygen or EPO production). Blood doping is an artificial method to increase RBC and EPO.

Anemia – Blood Loss

Acute hemorrhagic anemia: Rapid blood loss. Treated by blood replacement
Chronic hemorrhagic anemia: Slight, persistent blood loss. Treat the underlying cause like ulcers or hemorrhoids.

Anemia - RBC Production Defects

Iron-deficiency anemia: Hemorrhage, low Fe intake, impaired absorption. Treatment with iron supplements.
Pernicious anemia: Autoimmune - destroys stomach mucosa (needed to absorb B12). Treatment: Intramuscular B12 injections or nasal gel.
Renal anemia: Kidneys cannot produce enough EPO. Treatment: synthetic EPO.
Aplastic anemia: Destruction/inhibition bone marrow function. Treatment: Short-term: transfusion; Long-term: HSCs.

Anemia – RBC Destruction

Hemolytic anemia: Premature RBC lysis.
Hb abnormalities: Thalassemia and Sickle-cell anemia (genetic defects in globin). Sickle-cell anemia provides protection against malaria in some individuals.
Methods of treatment for abnormal hemoglobins and other disorders include incompatible transfusions, infections.

Polycythemia

Excess RBCs; increased blood viscosity; sluggish blood flow
Polycythemia vera: Bone marrow cancer - Treatment: therapeutic phlebotomy
Secondary polycythemia: Low O2 levels (high altitude) or EPO overproduction
Blood doping (artificial EPO or RBCs for stamina enhancement) is an ethical concern for athletes.

Platelets (thrombocytes)

Platelets are megakaryocyte fragments
Light blue-staining outer region, purple granules
Contain clotting chemicals (serotonin, calcium, enzymes, ADP, platelet-derived growth factor)
Form temporary plugs in injured blood vessels
Kept inactive and mobile via nitric oxide and prostacyclin from endothelial cells.

Platelet Formation (Thrombopoiesis)

Regulated by thrombopoietin (liver, kidneys)
Originate from megakaryoblasts (myeloid line blood cells)
Mitoses occurs, but no cytokinesis, to produce large, multilobed megakaryocytes. Projections from megakaryocytes are a route for platelets to detach into the blood vessel lumen.

Platelets

Stage IV megakaryocytes contact marrow sinusoids and send cytoplasmic projections (podosomes) into capillaries to release platelets.
Platelets live about 10 days
Normal platelet count: 150,000-400,000 platelets/µL blood.

Summary of Formed Elements

Table summarizing different blood cell types: Erythrocytes (red blood cells), Leukocytes (white blood cells), Granulocytes (neutrophils, eosinophils, basophils) and Agranulocytes (lymphocytes, monocytes), and Platelets
Includes illustrations, descriptions, cell count/µL of blood, and duration/life span of development.

Hematopoiesis in Humans

Detailed diagram outlining the processes of blood cell formation from the hematopoietic stem cell through stages in bone marrow, including different lineages and formed cell types.

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Description

This quiz explores the structure and function of erythrocytes, including their shape, composition, and role in oxygen transport. Additionally, it covers related concepts such as hematopoiesis and the functions of components in blood. Test your knowledge on the critical aspects of red blood cells and their physiological significance.