Blood Composition and Function General Composition of Blood Plasma Formed Elements Erythrocytes Leukocytes Hematopoesis Hemostasis (Clotting)

Blood Composition and Function General Composition of Blood

• Plasma

• Formed Elements

Erythrocytes

Leukocytes

Hematopoesis

Hemostasis (Clotting)

Transfusion and Blood Typing

Developmental Aspects of Blood

Blood Composition

Figure 10.1

The only fluid tissue in the human body

Classified as a connective tissue

• Living cells = formed elements

• Non-living matrix = plasma

Color range

• Oxygen-rich blood is scarlet red

• Oxygen-poor blood is dull red

pH must remain between 7.35–7.45

Blood temperature is slightly higher than body temperature

Hematocrit: Percent of blood volume that is RBCs

• 47% ± 5% for males

• 42% ± 5% for females

Blood Cell Types


• Plasma

• Formed Elements

Erythrocytes

Leukocytes

Hematopoesis




Erythrocytes (Red Blood Cells)

Main function is to carry oxygen

Biconcave disks

Essentially bags of hemoglobin; few organelles

Anucleate (no nucleus)

Outnumber white blood cells 1000:1

Contain the plasma membrane protein spectrin and other proteins

Major factor contributing to blood viscosity

Hemoglobin Molecular structure

• Protein globin: two alpha and two beta chains

• Heme pigment bonded to each globin chain

Iron atom in each heme can bind reversibly to one O2 molecule

Each Hb molecule can transport four O2

Sickle Cell Hemoglobin Causes Clotting

Normal hemoglobin = HbA

Sickle cell hemoglobin = HbS (mutation in single amino acid - missense)

Pleiotropic Effects Seen if HbS present

HbAHbA = normal

HbAHbS = sickle cell trait

HbSHbS = sickle cell disease/anemia

Fetal Hemoglobin Binds O2 More Avidly Fetal circulation must

extract oxygen from maternal circulation

Fetal hemoglobin (HbF) binds O2 more avidly than normal hemoglobin (HbA) does

Replaced by “adult” hemoglobin just after birth


• Plasma

• Formed Elements

Erythrocytes

Leukocytes

Hematopoesis




Leukocytes (White Blood Cells)

Figure 17.9

Formedelements

Platelets

Leukocytes

Erythrocytes

DifferentialWBC count(All total 4800 –10,800/l)

Neutrophils (50 – 70%)

Lymphocytes (25 – 45%)

Eosinophils (2 – 4%)

Basophils (0.5 – 1%)

Monocytes (3 – 8%)

Agranulocytes

Granulocytes

Leukocyte Levels in the Blood Normal levels are between 4,000 - 11,000 cells per millimeter

Abnormal leukocyte levels

• Leukocytosis

o Above 11,000 leukocytes/ml

o Generally indicates an infection (bacterial, fungal, parasitic)

o Also caused by some cancers, (including lymphocyte leukemia), hemhorrage, pneumonia

• Leukopenia

o Abnormally low leukocyte level (< 3,500/ml)

o Commonly caused by certain drugs, radiation

o Neutropenia (low neutrophil count) common in cancer patients receiving chemotherapy

o HIV-AIDS, TB, malaria, influenza also cause leukopenia

o Requires careful sanitation and “gowning up” for medical staff

Types of Leukocytes Granulocytes

• Granules in their cytoplasm can be stained

• Include neutrophils, eosinophils, and basophils

Figure 10.4

Agranulocytes

• Lack visible cytoplasmic granules

• Include lymphocytes and monocytes

Characteristics of Formed Elements of the Blood

N E B

Characteristics of Formed Elements of the Blood

L M


• Plasma

• Formed Elements

Erythrocytes

Leukocytes

Hematopoesis




Hematopoiesis Subdivided into erythropoesis and leukopoesis

Erythropoesis ccurs in red bone marrow

Erythropoesis Steps

1. Ribosome synthesis

2. Hemoglobin accumulation

3. Ejection of the nucleus and formation of reticulocytes

4. Reticulocytes then become mature erythrocytes

Figure 17.5

Stem cell

HemocytoblastProerythro-blast

Earlyerythroblast

Lateerythroblast Normoblast

Phase 1Ribosomesynthesis

Phase 2Hemoglobinaccumulation

Phase 3Ejection ofnucleus

Reticulo-cyte

Erythro-cyte

Committedcell

Developmental pathway

Fate of Erythrocytes

Unable to divide, grow, or synthesize proteins

Wear out in 100 to 120 days

When worn out, are eliminated by phagocytes in the spleen or liver

• Iron is salvaged for reuse

• Heme is degraded to yellow the pigment bilirubin

• Liver secretes bilirubin (in bile)) into the intestines

Lost cells are replaced by division of hemocytoblasts

Control of Erythrocyte Production Rate is controlled by a

hormone (erythropoietin)

Kidneys produce most erythropoietin as a response to reduced oxygen levels in the blood (hypoxia)

Hypoxia can develop from hemorrhage, low O2 in air, insufficient hemoglobin

Homeostasis is maintained by negative feedback from blood oxygen levels

Platelets Important in Clotting Small fragments of megakaryocytes

Formation is regulated by thrombopoietin

Blue-staining outer region, purple granules

Form a temporary platelet plug that helps seal breaks in blood vessels

Stem cell Developmental pathway

Hemocyto-blast Megakaryocyte Platelets


• Plasma

• Formed Elements

Erythrocytes

Leukocytes

Hematopoesis




Hemastasis: Blood Clotting

Collagenfibers

Platelets

Fibrin

Step Vascular spasm• Smooth muscle contracts, causing vasoconstriction.

Step Platelet plug formation

• Injury to lining of vessel exposes collagen fibers; platelets adhere.

• Platelets release chemicals that make nearby platelets sticky; platelet plug forms.

Step Coagulation• Fibrin forms a mesh that traps red blood cells and platelets, forming the clot.

1

2

3

Figure 17.13

Hemastasis

Undesirable Clotting

Thrombus

• A clot in an unbroken blood vessel

• Can be deadly in areas like the heart

Embolus

• A thrombus that breaks away and floats freely in the bloodstream

• Can later clog vessels in critical areas such as the brain, causing a stroke (CVA)

Bleeding Disorders Thrombocytopenia

• Platelet deficiency

• Even normal movements can cause bleeding from small blood vessels that require platelets for clotting

Hemophilia

• Hereditary bleeding disorder

• Normal clotting factors are missing or deficiency in Vit. K.

mild hemophilia


• Plasma

• Formed Elements

Erythrocytes

Leukocytes

Hematopoesis




Blood Groups and Transfusions Large losses of blood have

serious consequences

• Loss of 15 to 30 percent causes weakness

• Loss of over 30 percent causes shock, which can be fatal

Transfusions are the only way to replace blood quickly

Transfused blood must be of the same blood group

Human Blood Groups

Blood contains genetically determined proteins

A foreign protein (antigen) on a donated RBC may be attacked by the immune system

Blood is “typed” by using antibodies that will cause blood with certain proteins to clump (agglutination)

Human Blood Groups There are over 30 common red blood cell antigens

The most vigorous transfusion reactions are caused by ABO and Rh blood group antigens

ABO Blood Groups and Alleles

anti-A anti-B

anti-B

anti-A

Components of Blood of this Type

Rh Blood Groups and Hemolytic Deaseas of Newborns

Named because of the presence or absence of one of eight Rh antigens (agglutinogen D)

Most Americans are Rh+

The danger is only when the mother is Rh– and the father is Rh+, and the child inherits the Rh+ factor

Dd dd

Dd

dd

This baby, if from the second or subsequent

pregnancy, could have

complications in an Rh- mother

• Problems can occur in second and subsequent pregnancies when the baby’s Rh+ blood enters Rh– maternal circulation: erythroblastosis fetalis (hemolytic disease of the newborn)

• RhoGAM injections contain anti-Rh antibodies that quickly clear the maternal circulation of Rh protein


• Plasma

• Formed Elements

Erythrocytes

Leukocytes

Hematopoesis




Documents

Blood Composition and Function General Composition of Blood Plasma Formed Elements Erythrocytes Leukocytes Hematopoesis Hemostasis (Clotting)