Human Physiology: Blood and Fluid Composition

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Questions and Answers

What are the cellular components of blood?

Red blood cells, white blood cells, and platelets.

What are the main components of plasma?

Water, electrolytes, proteins, hormones, and waste products.

Describe the structure of a red blood cell (erythrocyte).

A red blood cell is a biconcave, non-nucleated disc that allows for increased surface area.

What are the phases of red blood cell production in the bone marrow?

The phases include differentiation of stem cells into proerythroblasts, then into erythroblasts, and finally into reticulocytes. Signup and view all the answers

What is the role of erythropoietin in red blood cell production?

Erythropoietin stimulates the bone marrow to increase red blood cell production, especially in response to low oxygen levels. Signup and view all the answers

How much total body water is approximately present in a 70Kg male?

Around 40-45 litres. Signup and view all the answers

What is the composition of extracellular fluid (ECF)?

ECF is composed of interstitial fluid and plasma. Signup and view all the answers

What triggers the increase in red blood cell production at high altitudes?

The lack of oxygen in the air prompts physiological changes that increase erythropoietin secretion and subsequently RBC production. Signup and view all the answers

What is the implication of erythropoietin use in sports?

It is commonly used for blood doping to enhance athletic performance by increasing the oxygen-carrying capacity of the blood. Signup and view all the answers

What happens in the body during anemia?

Anemia results in a reduced number of red blood cells or hemoglobin, leading to decreased oxygen-carrying capacity. Signup and view all the answers

What are the primary functions of red blood cells (RBC)?

RBCs primarily function in oxygen and carbon dioxide transport and act as a blood buffer to maintain pH around 7.4. Signup and view all the answers

Describe the normal structure of adult hemoglobin.

Adult hemoglobin consists of 4 polypeptide chains, specifically 2 alpha and 2 beta chains, each linked to a heme group containing an iron atom. Signup and view all the answers

What is the process of red blood cell breakdown?

RBCs are broken down in the spleen, where heme is separated from globin, with globin recycled as amino acids and heme yielding bilirubin, which is processed by the liver. Signup and view all the answers

Define the term 'anaemia.'

Anaemia is a condition characterized by a deficiency in the number or quality of red blood cells, leading to reduced oxygen delivery to tissues. Signup and view all the answers

What is the role of platelets in haemostasis?

Platelets play a crucial role in haemostasis by aggregating at the site of vascular injury and facilitating the formation of a clot. Signup and view all the answers

Explain the significance of blood group O Rh-negative individuals in transfusions.

Blood group O Rh-negative individuals are termed 'Universal Donors' because they have no antigens on their RBCs and can be received by patients with any blood type. Signup and view all the answers

What are hemoglobinopathies and give an example?

Hemoglobinopathies are disorders caused by abnormal hemoglobin structure, such as Sickle Cell Disease, characterized by distorted and fragile RBCs. Signup and view all the answers

What happens to bilirubin after red blood cell breakdown?

After RBC breakdown, bilirubin is transported to the liver, where it is processed and eventually secreted into bile. Signup and view all the answers

What is the relationship between high blood viscosity and polycythemia?

In polycythemia, the increase in red blood cell mass raises blood viscosity, potentially leading to heart failure or stroke. Signup and view all the answers

Outline the sequence of events leading to clot formation.

Clot formation begins with platelet adhesion to the injury site, followed by platelet aggregation, and culminates in the activation of fibrinogen to fibrin, creating a stable clot. Signup and view all the answers

Study Notes

Total Body Water

Total Body Water is around 60% of body weight
40-45 liters in a 70 kg male
Divided into Extracellular Fluid (ECF) and Intracellular Fluid (ICF)
ECF consists of Interstitial Fluid (ISF) and plasma

Composition of Blood

Plasma is a component of the Extracellular Fluid compartment

Cellular Content of Blood

Red Blood Cells (Erythrocytes)
White Blood Cells (Leukocytes)
Platelets (Thrombocytes)

Red Blood Cells

Mature Red Blood Cells are non-nucleated
Biconcave shape
Important for oxygen transport

Red Blood Cell Production

Begins in utero
Bone marrow takes over at 6-7 months
All bone marrow involved in children
Later life only sternum, vertebrae, ribs, and pelvis are involved
Requirements:
- Adequate nutrition
- Protein
- Vitamins (e.g. B12, folic acid)
- Erythropoietin (hormone released by the kidney)
Lack of RBC and/or Hb leads to anemia, reducing the oxygen-carrying capacity of the blood

Sequence of Events in Red Blood Cell Production

Proerythroblast is the first stage of development
Erythroblast
Normoblast
Reticulocyte
Mature red blood cell

Role of Erythropoietin

Increases red cell production in response to lack of oxygen (e.g., at high altitudes)
Synthesized EPO is used to treat patients, such as those with chronic renal failure
EPO is a source of controversy in sports for blood doping, potentially leading to:
- Polycythemia (increased red blood cell count)
- Increased blood viscosity
- Heart failure
- Stroke

Function of Red Blood Cells

Contain hemoglobin (Hb)
Oxygen transport
Carbon dioxide transport
Blood buffer (maintaining pH)

Structure of Hemoglobin

Four polypeptide chains (2 alpha/ 2 beta in adult HbA, 2 alpha / 2 gamma in fetal HbF)
Each linked to one heme molecule
Each heme contains one iron atom that binds oxygen
Hemoglobinopathies are abnormal Hbs, e.g., HbS (Sickle Cell Disease) and Thalassaemias

Anemia

Sickle Cell Disease is a genetic disorder causing sickled cells (fragile)
Symptoms: Sickle Cell Haemolytic Anaemia, severe pain, stroke, jaundice, respiratory problems

Red Blood Cell Breakdown

Lifespan is around 120 days
Cells become fragile and trapped in the spleen ("Red Cell Graveyard")
Heme is separated from globin
- Globin is recycled as amino acids
- Heme breakdown yields iron (recycled)
Other heme breakdown products:
- Biliverdin
- Bilirubin (yellow pigment transported to the liver and excreted in bile)
Jaundice is caused by high levels of bilirubin in blood, and can occur in liver disease

Blood Groups

An individual’s blood group is determined by the antigen present on the red blood cell membrane
All blood groups are either Rhesus (Rh) positive or negative
Blood group O, Rhesus negative is considered the “Universal Donor" because there are no antigens to react with antibodies in the recipient’s plasma

Blood Transfusion

Patients’ blood is typed and crossmatched to prevent reactions
If the antigen on the donor’s cells comes in contact with the corresponding antibody in the recipient’s plasma, an adverse reaction will occur
For example, if a patient with type A blood receives a transfusion of type B blood, the patient's anti-B antibodies will react with the B antigens on the donor's red blood cells

Platelets

Platelets are important for hemostasis (stopping bleeding)

Coagulation

Platelets trigger a cascade of events resulting in the formation of the clotting protein fibrin
fibrin forms a mesh that traps red blood cells, forming a clot and stopping the bleeding

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Description

This quiz covers the essential concepts of total body water, blood composition, and the formation of red blood cells. It explores the roles of different blood components and what is required for effective red blood cell production. Test your knowledge of human physiology regarding body fluids and blood.