Blood Functions and Composition

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Questions and Answers

What is the main function of the formed elements in blood?

To transport oxygen and nutrients to body cells (correct)

To produce plasma proteins

To maintain normal pH buffers

To regulate body temperature

What is the primary composition of blood plasma?

80% water and 20% dissolved solutes

About 90% water and over 100 dissolved solutes (correct)

70% water and 30% dissolved solutes

90% water and 10% dissolved solutes

What is the primary function of albumin in blood plasma?

To work as a carrier of other molecules, blood buffer, and contribute to plasma osmotic pressure (correct)

To transport oxygen to body cells

To produce hormones

To regulate body pH

What is the approximate percentage of erythrocytes in whole blood?

45% in males and 42% in females Signup and view all the answers

What is the primary function of blood in the body?

To transport oxygen and nutrients to body cells, and metabolic wastes to lungs and kidneys for elimination Signup and view all the answers

What is the approximate pH range of blood?

7.35 to 7.45 Signup and view all the answers

What is the function of leukocytes in blood?

To fight infection and disease Signup and view all the answers

What is the average volume of blood in a male adult?

5 to 6 liters Signup and view all the answers

What is the characteristic of blood color when it has high oxygen content?

Scarlet red Signup and view all the answers

What is the main function of hemoglobin in erythrocytes?

To transport oxygen Signup and view all the answers

What is the shape of an erythrocyte?

Biconcave Signup and view all the answers

What is the percentage of erythrocytes that contain mitochondria?

0% Signup and view all the answers

What is the process of oxygen unloading in tissues called?

Deoxyhemoglobin Signup and view all the answers

What is the origin of most blood cells?

Bone marrow Signup and view all the answers

What is the term for the formation of all blood cells?

Hematopoiesis Signup and view all the answers

What is the term for the stem cell that gives rise to all formed elements?

Hemocytoblast Signup and view all the answers

What is the name of the stem cell that transforms into a myeloid stem cell during erythropoiesis?

Hematopoietic stem cell Signup and view all the answers

What is the result of having too few red blood cells in the body?

Hypoxia Signup and view all the answers

What is the hormone that stimulates the production of red blood cells in response to hypoxia?

Erythropoietin Signup and view all the answers

What is the effect of erythropoietin on red blood cell production?

It causes red blood cells to mature faster Signup and view all the answers

What is the effect of high oxygen levels on erythropoietin production?

It inhibits the production of erythropoietin Signup and view all the answers

What is the result of having too many red blood cells in the body?

Increased blood viscosity Signup and view all the answers

What is the approximate number of red blood cells produced every second?

2 million Signup and view all the answers

What is the primary role of iron in erythropoiesis?

To promote the production of hemoglobin Signup and view all the answers

What is the cause of pernicious anemia?

Autoimmune destruction of intrinsic factor Signup and view all the answers

What is the characteristic shape of red blood cells in sickle cell anemia?

Crescent-shaped Signup and view all the answers

What is the purpose of transfusion in sickle cell anemia treatment?

To provide healthy red blood cells Signup and view all the answers

What is the function of vitamin B12 and folic acid in erythropoiesis?

To support the rapid division of cells Signup and view all the answers

What is the result of aplastic anemia?

Inhibition of red bone marrow Signup and view all the answers

What is the term for the premature lysis of red blood cells?

Hemolytic anemia Signup and view all the answers

What is the effect of transfusion on sickle cell anemia patients?

It reduces the risk of malaria Signup and view all the answers

What is the genetic disorder characterized by the absent or reduced production of one globin chain?

Thalassemia Signup and view all the answers

What is the treatment for sickle cell anemia that induces the formation of fetal hemoglobin?

Hydroxyurea Signup and view all the answers

What is the primary cause of polycythemia vera?

Bone marrow cancer leading to excess red blood cells Signup and view all the answers

What is the function of therapeutic phlebotomy in polycythemia vera?

To reduce blood viscosity Signup and view all the answers

What is the percentage of hematocrit that may be reached in polycythemia vera?

80% Signup and view all the answers

What is the characteristic of a monocyte?

It has a kidney shape and later turns into a macrophage Signup and view all the answers

What is the name of the process by which white blood cells are produced from bone marrow?

Leukopoiesis Signup and view all the answers

What is the characteristic of granulocytes?

They are produced from myeloid stem cells Signup and view all the answers

What is the percentage of lymphocytes in the blood?

25% Signup and view all the answers

What is the reason why there are more white blood cells produced than red blood cells?

Because white blood cells have a shorter life Signup and view all the answers

What is the developmental sequence of agranulocytes?

Monoblast to promonocyte to monocyte Signup and view all the answers

What is the purpose of using hematopoietic hormones in cancer patients?

To stimulate bone marrow production Signup and view all the answers

What is the lifespan of a monocyte?

Several months Signup and view all the answers

What is the purpose of using hematopoietic hormones in AIDS patients?

To increase the protective immune response Signup and view all the answers

What is a common precursor shared by monocytes and neutrophils?

Myeloid stem cell Signup and view all the answers

What type of cells are involved in myeloid leukemia?

Myeloblasts Signup and view all the answers

What is the primary cause of death in leukemia patients if left untreated?

Internal hemorrhage or overwhelming infections Signup and view all the answers

What is the name of the virus that causes infectious mononucleosis?

Epstein-Barr virus Signup and view all the answers

What is the term for a condition characterized by an abnormally low number of white blood cells?

Leukopenia Signup and view all the answers

What is the term for a type of leukemia that involves the proliferation of later cell stages and primarily affects older people?

Chronic leukemia Signup and view all the answers

What is a common symptom of infectious mononucleosis?

Sore throat, low fever, and tiredness Signup and view all the answers

What is the primary function of platelets in the blood?

To help in the clotting process Signup and view all the answers

What is the normal range of platelets in a microliter of blood?

150000-400000 Signup and view all the answers

What is the role of thrombopoietin in platelet formation?

It regulates platelet formation Signup and view all the answers

What is the first step in the clotting process?

Vascular spasm Signup and view all the answers

What is the function of von Willebrand factor in platelet plug formation?

It helps to stabilize platelet collagen adhesion Signup and view all the answers

What is the effect of prostacyclins on platelet plug formation?

It prevents platelet sticking Signup and view all the answers

What is the origin of platelets in the blood?

From the megakaryocytes in the bone marrow Signup and view all the answers

What is the role of nitric oxide in platelet function?

It keeps platelets inactive and mobile Signup and view all the answers

What is the effect of serotonin on platelet plug formation?

It enhances vascular spasm Signup and view all the answers

What is the term for the process of stopping bleeding?

Hemostasis Signup and view all the answers

What is the trigger for the intrinsic pathway of coagulation?

Negatively charged surfaces Signup and view all the answers

What is the role of thrombin in phase 3 of coagulation?

Converting fibrinogen to fibrin Signup and view all the answers

What is the function of factor XIII in coagulation?

Cross-linking fibrin and stabilizing the clot Signup and view all the answers

What is the result of the coagulation process?

Blood is transformed from liquid to gel Signup and view all the answers

What is the role of vitamin K in coagulation?

Synthesizing clotting factors Signup and view all the answers

What is the difference between the intrinsic and extrinsic pathways of coagulation?

Intrinsic pathway uses clotting factors within the blood, while extrinsic uses tissue factor Signup and view all the answers

What is the function of prothrombin activator in coagulation?

Converting prothrombin to thrombin Signup and view all the answers

What is the result of the formation of fibrin strands in coagulation?

Fibrin strands form the structural basis of the clot Signup and view all the answers

What is the trigger for the extrinsic pathway of coagulation?

Tissue factor Signup and view all the answers

What is the primary function of clot retraction?

To draw the ruptured blood vessel edges together Signup and view all the answers

What is the role of plasminogen in fibrinolysis?

To convert into plasmin, a fibrin-digesting enzyme Signup and view all the answers

What is the primary function of tissue plasminogen activator (tPA) in fibrinolysis?

To convert plasminogen into plasmin Signup and view all the answers

What is the result of clot retraction?

The drawing of the ruptured blood vessel edges together Signup and view all the answers

What stimulates the division of smooth muscle cells and fibroblasts during vessel repair?

Platelet-derived growth factor (PDGF) Signup and view all the answers

What happens to serum during clot retraction?

It is squeezed out of the clot Signup and view all the answers

When does fibrinolysis typically begin?

Within 2 days of clot formation Signup and view all the answers

What is the term for a clot that develops and persists in an unbroken blood vessel?

Thrombus Signup and view all the answers

What is the primary purpose of anti-coagulant drugs?

To prevent undesirable clotting Signup and view all the answers

What is the term for a deficit in the number of circulating platelets?

Thrombocytopenia Signup and view all the answers

What is the diagnostic platelet count for thrombocytopenia?

Less than 50,000/ul Signup and view all the answers

What is the treatment for thrombocytopenia?

Transfusion of concentrated platelets Signup and view all the answers

What is a common cause of impaired liver function that affects blood coagulation?

Vitamin K deficiency Signup and view all the answers

What is the primary symptom of hemophilia A?

Prolonged bleeding into joint cavities Signup and view all the answers

What is a consequence of disseminated intravascular coagulation?

All of the above Signup and view all the answers

What is the treatment for hemophilia A?

Injection of genetically engineered factors Signup and view all the answers

What is a possible cause of disseminated intravascular coagulation?

Septicemia Signup and view all the answers

What is the effect of liver disease on vitamin K absorption?

Decreased vitamin K absorption Signup and view all the answers

Study Notes

Blood Functions

Transporting oxygen and nutrients to body cells
Transporting metabolic wastes to lungs and kidneys for elimination
Transporting hormones from endocrine organs to target organs
Protecting against blood loss and infection
Regulating body temperature
Maintaining normal pH buffers
Maintaining adequate fluid volume in the circulatory system

Composition of Blood

Blood is the only fluid tissue in the body
Consists of plasma and formed elements (type of connective tissues)
Cells are suspended in plasma
Formed elements include erythrocytes, leukocytes, and platelets

Blood Layers

Erythrocytes (red blood cells) make up 45% of whole blood (47% in males, 42% in females)
Plasma makes up 55% of whole blood
White blood cells and platelets in the buffy coat make up less than 1% of whole blood

Physical Characteristics and Volume

Blood is a sticky, opaque fluid with a metallic taste
Color varies with oxygen content (scarlet red with high oxygen, dark red with low oxygen)
pH ranges from 7.35 to 7.45
Average volume of blood in males is 5-6 liters, and in females is 4-5 liters

Blood Plasma

Blood plasma is a straw-colored, sticky fluid
Composed of approximately 90% water
Contains over 100 dissolved solutes, including nutrients, gases, hormones, wastes, proteins, and inorganic ions
Proteins produced mainly by the liver, including albumin, which makes up 60% of plasma proteins
Albumin functions as a carrier of other molecules, blood buffer, and contributes to plasma osmotic pressure

Formed Elements

Formed elements include red blood cells, white blood cells, and platelets
White blood cells are the only complete cells, while red blood cells lack nuclei and organelles
Platelets are cell fragments
Most formed elements have a short lifespan of only a few days in the blood stream
Most blood cells originate from bone marrow and do not divide

Erythrocytes (Red Blood Cells)

Erythrocytes have a diameter of 7.5 micrometers and play a crucial role in gas transport
They consist of a plasma membrane and spectrin, which allows for flexibility and shape change
Characteristics include a biconcave shape, 97% hemoglobin content, and lack of mitochondria
Functions include gas transport, with hemoglobin binding to oxygen
The red hue of erythrocytes gives blood its red color
Hemoglobin is composed of 4 polypeptides: 2 alpha and 2 beta
There are 4-6 million erythrocytes per microliter of blood
Oxygen loading in the lungs is called oxyhemoglobin, while oxygen unloading in tissues is called deoxyhemoglobin
20% of carbon dioxide in the blood binds to hemoglobin, forming carbaminohemoglobin

Hematopoiesis and Hematopoietic Stem Cells

Hematopoiesis is the formation of all blood cells
Hematopoietic stem cells, also known as hemocytoblasts, give rise to all formed cells
Committed cells cannot change their cell type
New blood cells enter the sinusoids

Erythropoiesis

Erythropoiesis is the formation of red blood cells, which have a lifespan of 15 days
The process involves the transformation of a hematopoietic stem cell into a myeloid stem cell, then a proerythroblast, followed by a series of divisions and maturation stages

Maturation Stages

Proerythroblast divides into basophilic erythroblast, which synthesizes ribosomes and stains blue
Basophilic erythroblast develops into polychromatic erythroblast, characterized by a red hue with pink and blue areas
Polychromatic erythroblast matures into orthochromatic erythroblast, which contains hemoglobin and turns pink

Regulation and Requirement of Erythropoiesis

Too few red blood cells lead to hypoxia
Too many red blood cells increase blood viscosity
Approximately 2 million red blood cells are produced every second
Erythropoiesis is regulated by hormonal controls and dietary requirements

Hormonal Controls

Erythropoietin is a blood hormone released by the kidney
Hypoxia-induced factor can be accumulated due to hypoxia and hormonal control
Causes of hypoxia include hemorrhage, pneumonia, and iron deficiency
Erythropoietin is inhibited by erythrocytes and high oxygen levels
Testosterone enhances erythropoietin production

Dietary Requirements for Erythropoiesis

Amino acids, lipids, and carbohydrates are necessary for erythropoiesis
Iron is essential, but it needs to bind with protein to avoid toxicity
Iron is stored in cells called ferritin and hemosiderin
Transferrin transports iron in the blood

Vitamins and Anemia

Vitamin B12 and folic acid support rapidly dividing cells
Anemia can be caused by hemorrhage, iron deficiency, chronic hemorrhagic anemia, pernicious anemia, and renal anemia

Types of Anemia

Pernicious anemia: an autoimmune disease that destroys the intrinsic factor, leading to the inability to absorb B12
Renal anemia: occurs when the kidneys fail to produce erythropoietin
Aplastic anemia: caused by the destruction or inhibition of red bone marrow, often due to drugs, chemicals, radiations, or viruses
Hemolytic anemias: premature lysis of red blood cells, often caused by incompatible transfusion, infections, or hemoglobin abnormalities

Thalassemias

A genetic disorder resulting in abnormal globins
Typically found in people of Mediterranean ancestry
Characterized by the absence of one globin chain
Red blood cells are thin and deficient in hemoglobin

Sickle Cell Anemia

Caused by Hemoglobin S or mutated hemoglobin
Only one amino acid is incorrect in the beta chain out of 146 amino acids
Red blood cells become crescent-shaped when oxygen levels are low
Misshapen red blood cells rupture easily and block small vessels
More prevalent in black people
Individuals with 2 copies of Hb-s develop sickle-cell anemia, while those with 1 copy have a milder disease and a better chance of surviving malaria
Treatments include transfusion, inhaled nitric oxide, stem cell transplants, gene therapy, and hydroxyurea to induce fetal hemoglobin formation

Erythrocyte Disorders

Polycemia is a condition characterized by an excess of red blood cells and increased blood viscosity, leading to sluggish blood flow.
Polycythemia vera is a type of bone marrow cancer that causes an overproduction of red blood cells, resulting in a high hematocrit level (up to 80%).
Therapeutic phlebotomy is a treatment for polycythemia vera.

Causes of Polycemia

Low oxygen levels can lead to polycemia.
Increased EPO (erythropoietin) production can also cause polycemia.

Leukocytes

Leukocytes are complete cells with a shorter lifespan compared to red blood cells.
There are three main components of leukocytes: basophils, eosinophils, and neutrophils.

Agranulocytes

Agranulocytes consist of lymphocytes and monocytes.
Lymphocytes make up 25% of leukocytes and are divided into two types: T-lymphocytes (cell-mediated, originating from the thymus) and B-lymphocytes (antibody-producing, originating from bone marrow).
Monocytes are rare, making up 3-8% of leukocytes, and have a kidney-shaped nucleus that later develops into macrophages.

Leukopoiesis

Leukopoiesis is the production of white blood cells from bone marrow, involving the action of interleukins and colony-stimulating factors.

Leukocyte Development

Leukocytes originate from hemocytoblasts, which give rise to lymphoid stem cells and myeloid stem cells.
Lymphoid stem cells produce lymphocytes, while myeloid stem cells produce other elements.

Granulocyte Production

Myeloblasts produce myelocytes.
Promyelocytes produce lysosomes.
Myelocytes produce granules.
Band cells produce nuclei that form a carved arc shape.
Mature granulocytes have segmented nuclei and are released into the blood, with 10 times more stored in the bone marrow than in the blood.

Agranulocyte Production

Agranulocyte production occurs in the following stages: monoblast → promonocyte → monocyte
Monocytes can live up to several months

Hematopoietic Hormones

EPO (Erythropoietin) and CSF (Colony-Stimulating Factor) are hematopoietic hormones used clinically
These hormones can stimulate bone marrow in cancer patients receiving chemotherapy or stem cell transplants
They are also used to increase protective immune responses in AIDS patients

Leukocytes Disorders

Leukocytes disorders include overproduction of abnormal white blood cells, such as leukemia and infectious mononucleosis.
Leukopenia is a condition characterized by an abnormally low number of white blood cells, which can be drug-induced.

Leukemia

Leukemia involves the cloning of white blood cells, with myeloid leukemia involving myeloblast descendants and lymphocytic leukemia involving lymphocytes.
Acute leukemia derives from stem cells and primarily affects children.
Chronic leukemia involves the proliferation of later cell stages and is prevalent in older people.
Without treatment, all leukemia are fatal, with death resulting from internal hemorrhage or overwhelming infections.
Cancerous cells fill the red bone marrow, leading to leukemia.

Treatment of Leukemia

Treatments for leukemia include irradiation, antileukemia drugs, and stem cell transplants.

Infectious Mononucleosis

Infectious mononucleosis is a highly contagious viral disease, usually seen in young adults.
It is caused by the Epstein-Barr virus and results in high numbers of typical agranulocytes.
The disease involves lymphocytes that become enlarged, and was originally thought to involve monocytes, hence the name mononucleosis.
Symptoms of infectious mononucleosis include sore throat, low fever, tiredness, and achy feelings.

Platelets

Cytoplasmic fragments of megakaryocytes with a blue-staining outer region and purple granules
Granules contain serotonin, calcium, enzymes, ADP, and platelet-derived growth factor (PDGF), which help in the clotting process
Normal platelet count is between 150,000 to 400,000 platelets/mcl of blood
Circulating platelets are kept inactive and mobile by nitric oxide (NO)
Platelet formation is regulated by thrombopoietin
Formed in the myeloid line from megakaryoblast (stage I megakaryocyte)

Platelet Formation

Stage IV megakaryocyte sends cytoplasmic projections into the lumen of a capillary
Projections then break off into platelet fragments

Hemostasis

Fast series of reactions to stop bleeding
Requires clotting factors and substances released by platelets and injured tissues
Three steps involved in the clotting process: vascular spasm, platelet plug formation, and coagulation

Vascular Spasm

Vessel responds to injury with vasoconstriction triggered by direct injury to vascular smooth muscle, chemicals released by endothelial cells, and pain reflexes
Most effective in smaller blood vessels

Platelet Plug Formation

Platelets stick to collagen fibers exposed when a vessel is damaged
Prostacyclins and nitric oxide secreted by endothelial cells prevent platelet sticking
Von Willebrand factor helps stabilize platelet-collagen adhesion
Activated platelets swell, become spiked and sticky, and release chemical messengers: • ADP causes more platelets to stick and release their contents • Serotonin and thromboxane A2 enhance vascular spasm and platelet aggregation

Coagulation Process

Coagulation reinforces the platelet plug with fibrin threads, transforming blood from a liquid to a gel-like state.

Coagulation Factors

There are 13 clotting factors (procoagulants) involved in the coagulation process, numbered I to XIII in the order of their discovery.
Vitamin K is necessary for the synthesis of four clotting factors.

Phase 1 of Coagulation

Coagulation can be initiated by either the intrinsic or extrinsic pathway.
The intrinsic pathway is triggered by negatively charged surfaces, such as activated platelets, collagen, or glass.
The extrinsic pathway is triggered by exposure to tissue factor (TF) and is a faster pathway.
Both pathways cascade towards the activation of factor X.

Phase 1 of Coagulation (Factor X Activation)

Factor X combines with calcium and platelet factor 3 and factor 5 to form prothrombin activator.

Phase 2 of Coagulation

Prothrombin activator catalyzes the transformation of prothrombin to the active enzyme thrombin.

Phase 3 of Coagulation

Thrombin converts soluble fibrinogen to fibrin, forming the structural basis of the clot.
Fibrin makes the plasma become gel-like and traps formed elements passing by.
Thrombin, along with calcium, activates factor XIII, the fibrin-stabilizing factor, which cross-links fibrin and strengthens the clot.

Anticoagulants and Blood Coagulation

Anticoagulants are factors that inhibit blood coagulation, and can also refer to drugs that prevent clotting.

Clot Formation and Stabilization

A clot must be stabilized and removed after the damaged area has been repaired.
Clot retraction occurs within 30-60 minutes, where actin and myosin in platelets contract, pulling on fibrin strands and squeezing serum from the clot.
Serum is plasma minus the clotting proteins.

Clot Retraction and Vessel Repair

Clot retraction draws ruptured blood vessel edges together, preparing for repair.
Platelet-derived growth factor (PDGF) is released by platelets, stimulating the division of smooth muscle cells and fibroblasts to rebuild the blood vessel wall.

Fibrinolysis and Clot Removal

Fibrinolysis is the process of removing clots after repair is completed, starting within 2 days and continuing for several days until the clot is dissolved.
Plasminogen, a plasma protein trapped in the clot, is converted to plasmin, a fibrin-digesting enzyme.
Tissue plasminogen activator (tPA), factor XII, and thrombin all play a role in the conversion process.

Thromboembolic Disorders

Undesirable clot formation can lead to tissue death by blocking circulation
Thrombus: a clot that develops and persists in an unbroken blood vessel
Embolus: a thrombus that is freely floating in the bloodstream
Embolism: an embolus that obstructs a vessel

Treatment of Thromboembolic Disorders

Anti-coagulant drugs are used to prevent undesirable clotting, such as:
- Aspirin
- Heparin
- Warfarin

Bleeding Disorders

Abnormalities that prevent normal clot formation
Thrombocytopenia: a deficit of circulating platelets
Petechiae: a result of spontaneous widespread hemorrhage

Causes of Thrombocytopenia

Suppression or destruction of red bone marrow, such as:
- Malignancy
- Radiation
- Drugs

Diagnosis and Treatment of Thrombocytopenia

Platelet count less than 50k/ul is diagnostic
Treatment: transfusion of concentrated platelets

Impaired Liver Function

Inability to synthesize procoagulant factors can be caused by vitamin K deficiency, hepatitis, or cirrhosis
Liver disease can prevent the liver from producing bile, leading to impaired absorption of fat and vitamin K

Hemophilia

Hemophilia refers to a group of hereditary bleeding disorders
Hemophilia A: most common type, caused by factor VIII deficiency
Hemophilia B: caused by factor IX deficiency
Hemophilia C: milder form, caused by factor XI deficiency
Symptoms: prolonged bleeding, especially into joint cavities
Treatment: injection of genetically engineered factors, eliminating the need for plasma transfusion and the risk of contracting hepatitis or HIV

Disseminated Intravascular Coagulation (DIC)

Involves both widespread clotting and severe bleeding
Widespread clotting occurs in intact blood vessels, blocking blood flow
Severe bleeding follows due to depletion of clotting factors
Can occur in:
- Septicemia
- Incompatible blood transfusions
- Complications in pregnancy

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Description

Learn about the vital functions of blood, including transporting oxygen and nutrients, and its composition, including plasma and formed elements.