Blood Composition and Function

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Questions and Answers

What are the four general overall functions of blood?

Transport medium, haemostatic function, homeostatic function, and defensive function.

Briefly describe the composition and percentages of cellular elements versus plasma in blood.

Cellular elements make up 45% of blood and consist of RBCs, WBCs, and platelets. Plasma makes up 55% of blood.

What are the main components of plasma, and what approximate percentage does each represent?

Plasma is composed of 90% water, 0.9% inorganic substances, and 9.1% organic substances.

List three advantages of the biconcave shape of red blood cells (RBCs).

Increased surface area, minimal membrane tension when the volume of the cell changes, and increased cell flexibility. Signup and view all the answers

Outline the primary function of RBCs related to gas transport.

RBCs transport oxygen from the lungs to the tissues and carbon dioxide from the tissues back to the lungs, primarily facilitated by hemoglobin. Signup and view all the answers

Besides gas transport, what other significant function do RBCs perform related to acid-base balance?

Hemoglobin in RBCs acts as an excellent acid-base buffer. Signup and view all the answers

Briefly describe how RBCs contribute to blood viscosity and its subsequent effect.

RBCs produce blood viscosity, which contributes to peripheral resistance to maintain arterial blood pressure (ABP). Signup and view all the answers

What key role does the cell membrane of RBCs play in maintaining cellular integrity and function?

The cell membrane keeps hemoglobin inside cells to prevent its loss in plasma and provides a large surface area for gas exchange. Signup and view all the answers

How are glycoproteins on the surface of RBCs used in determining blood groups?

The glycoproteins present are antigens used for determination of blood groups. Signup and view all the answers

Describe the composition of adult hemoglobin (Hb A).

Adult hemoglobin (Hb A) contains two alpha and two beta polypeptide chains. Signup and view all the answers

How does fetal hemoglobin (Hb F) differ from adult hemoglobin (Hb A) in terms of oxygen affinity and composition?

Hb F has a greater affinity for oxygen than Hb A and is composed of two alpha and two gamma chains. Signup and view all the answers

How does hemoglobin combine with oxygen, and what is the significance of this combination?

Hemoglobin combines loosely and reversibly with oxygen to form oxyhemoglobin. This allows for efficient oxygen transport. Signup and view all the answers

What happens to hemoglobin when RBCs rupture, and where does this process primarily occur?

Released hemoglobin from ruptured RBCs is phagocytosed by macrophages, primarily in the spleen. Signup and view all the answers

Outline the breakdown products of hemoglobin and their subsequent fate.

Hemoglobin breaks down into globin (amino acids) and heme (iron and biliverdin), with biliverdin converting to bilirubin. Signup and view all the answers

Define erythropoiesis.

Erythropoiesis is the process of new RBC production. Signup and view all the answers

Describe the sites of erythropoiesis at different stages of development (first trimester, middle trimester, and last trimester/after birth).

In the first trimester, the yolk sac. Second trimester, liver and spleen. Last trimester and after birth, red bone marrow. Signup and view all the answers

Outline the primary site of erythropoiesis after the age of 20.

Red bone marrow in flat bones such as the skull, vertebrae, sternum, ribs, and pelvic bones, and proximal parts of long bones. Signup and view all the answers

What principal factor stimulates RBC production, and how does it act?

Defective tissue oxygenation (O2 lack or hypoxia) increases erythropoiesis by releasing erythropoietin hormone. Signup and view all the answers

Briefly describe the role and sources of erythropoietin hormone in adults.

Erythropoietin is a glycoprotein that mostly produced by the kidneys (90%) in adults and stimulates RBC production. Signup and view all the answers

What effect does erythropoietin have on erythrogenesis?

It stimulates the production of proerythroblasts from stem cells and speeds up all the stages of development into erythroblasts and then into mature RBCs. Signup and view all the answers

List three factors that stimulate erythropoietin secretion.

Hypoxia, epinephrine, and androgens. Signup and view all the answers

How does bone marrow destruction impact erythropoiesis?

Destruction of bone marrow by irradiation, chemicals, drugs, or bacterial toxins leads to aplastic anemia. Signup and view all the answers

What key roles does a healthy liver play in supporting erythropoiesis?

The liver supports erythropoiesis by formation of globin portion of Hb, formation of 10% of erythropoietin, and by storing iron and vitamin B12 . Signup and view all the answers

Name three hormones that stimulate erythropoiesis.

Thyroid hormones, androgens, and glucocorticoids. Signup and view all the answers

Explain the importance of proteins and minerals like copper and cobalt in erythropoiesis.

Proteins contain essential amino acids needed for erythropoiesis and copper and cobalt act as cofactors in Hb synthesis, cobalt stimulates erythropoietin secretion. Signup and view all the answers

Describe the significance of iron and vitamins, particularly folic acid and vitamin B12, in erythropoiesis.

Iron enters formation of heme and vitamins, especially Folic acid and B12, that are essential for maturation of RBCs. Signup and view all the answers

Outline the distribution of iron in the body.

65% is in the form of hemoglobin, 4% in the form of myoglobin, 1% in the cytochrome enzyme, 0.1% combined with transferrin, and 15-30% stored in the form of ferritin. Signup and view all the answers

What are the daily losses and intakes of iron in males and females?

0.6 mg in males and 1.3 in females. Signup and view all the answers

How is iron stored in tissues and transported in the blood?

It is stored in tissues as ferritin and transported in blood by transferrin. Signup and view all the answers

Which of the following is needed for erythropoiesis?

Vitamin B12 Signup and view all the answers

Which of the following is most probably to occur in a person living at high altitude?

Increased red blood cell count Signup and view all the answers

Which of the following is the source of erythropoietin?

Kidneys Signup and view all the answers

Which of the following is needed for vitamin B12 absorption?

Intrinsic factor Signup and view all the answers

How does tissue oxygenation influence erythropoiesis and which hormone mediates this effect?

Low tissue oxygen leads to increased erythropoiesis through the release of erythropoietin. Signup and view all the answers

What is the significance of hemoglobin's ability to combine loosely and reversibly with oxygen?

This reversibility allows hemoglobin to efficiently transport oxygen to tissues and collect carbon dioxide for removal. Signup and view all the answers

Explain the process by which old or damaged RBCs are removed from circulation and the role of the spleen in this process.

Old RBCs rupture, especially in the spleen, and their components are phagocytosed by macrophages. Signup and view all the answers

Describe the process of iron absorption, mentioning the key proteins involved.

Iron is absorbed in the intestine with the help of DMT1. Ferroportin 1 helps in transporting iron from the cells to blood and Transferrin transports iron in the blood. Signup and view all the answers

What is the role of intrinsic factor in vitamin B12 absorption, and where is it produced?

Intrinsic factor is needed for vitamin B12 absorption; it is produced by the parietal cells of the stomach. Signup and view all the answers

How do disorders of the bone marrow, such as those caused by irradiation or chemicals, affect erythropoiesis?

They can cause destruction of bone marrow leading to aplastic anemia, impairing RBC production. Signup and view all the answers

Explain why both iron deficiency and vitamin deficiencies such as B12 and folic acid lead to anemia.

Iron deficiency limits heme and hemoglobin production, while B12 and folic acid deficiencies impair RBC maturation, both leading to anemia. Signup and view all the answers

How does the biconcave shape of red blood cells enhance their function in oxygen transport?

The biconcave shape increases the surface area for gas exchange and provides flexibility when passing through small capillaries. Signup and view all the answers

Explain the roles of the kidney and liver in erythropoiesis, especially regarding erythropoietin production.

The kidneys primarily produce erythropoietin in adults, which stimulates RBC production. The liver produces a smaller amount of erythropoietin (10%) in adults and is the primary site during fetal life. Signup and view all the answers

Describe how hemoglobin's structure facilitates the reversible binding of oxygen.

Hemoglobin contains iron (Fe++) to which oxygen molecules loosely and reversibly attach, forming oxyhemoglobin. Signup and view all the answers

Outline the process by which iron is absorbed in the intestines, mentioning key transporters and storage forms.

Iron is absorbed either as heme iron, or as Fe2+ after reduction of non-heme iron by duodenal cytochrome B. It is transported into cells via DMT1. Inside intestinal cells iron is stored as ferritin and transported in blood by transferrin. Signup and view all the answers

What is the significance of fetal hemoglobin (HbF) having a higher affinity for oxygen than adult hemoglobin (HbA)?

The higher affinity of HbF allows the fetus to efficiently extract oxygen from the maternal blood supply, ensuring adequate oxygenation for development. Signup and view all the answers

How do old or damaged red blood cells get removed from circulation, and how are their components recycled?

Old RBCs rupture in the spleen and their components are recycled. Hemoglobin is phagocytized, broken down into globin (amino acids) and heme (iron and biliverdin), which eventually becomes bilirubin. Signup and view all the answers

Describe the role of Vitamin B12 in red blood cell production and explain how a deficiency in this vitamin affects erythropoiesis.

Vitamin B12 is essential for the maturation of red blood cells. A deficiency leads to megaloblastic anemia, characterized by large, immature, and dysfunctional red blood cells. Signup and view all the answers

Explain how chronic hypoxia stimulates erythropoiesis, including the specific hormone involved and its primary site of production.

Chronic hypoxia stimulates the release of erythropoietin (EPO) primarily from the kidneys. EPO then stimulates the bone marrow to increase red blood cell production. Signup and view all the answers

What are the four general functions of blood?

Transport medium, haemostatic function, homeostatic function and defensive function. Signup and view all the answers

Explain how the body maintains iron balance, considering daily loss, intake, storage, and transport.

The body maintains iron balance by equating daily loss with intake. Iron is stored as ferritin in tissues and transported in the blood by transferrin, ensuring a balance between iron use and storage. Signup and view all the answers

Flashcards

General functions of blood

Blood serves as a transport medium, facilitates hemostasis, maintains homeostasis, and defends the body.

Composition of blood

Blood consists of cellular elements (45%) including RBCs, WBCs, and platelets, and plasma (55%).

Plasma composition

Plasma is composed of 90% water, 0.9% inorganic substances, and 9.1% organic substances like plasma proteins and lipids.