Comprehensive Blood and Hemostasis Notes

Blood

Blood is the fluid and cells inside the Cardiovascular System.

Functions of the System

The body cannot function fast enough with simple diffusion, necessitating the cardiovascular system.
The heart creates pressure to push blood.
Vessels transport blood throughout the body.
Blood cells and plasma carry nutrients and wastes.

Components of Blood

Formed elements (cells):
- Red Blood Cells (RBC)
- White Blood Cells (WBC)
- Thrombocytes (platelets)
Plasma (fluid portion):
- Water
- Wastes
- Dissolved nutrients
- Dissolved proteins

Makeup of Blood

Blood is composed of plasma, leukocytes and platelets (buffy coat), and erythrocytes.
Plasma constitutes 55% of whole blood.
Leukocytes and platelets make up less than 1% of whole blood.
Erythrocytes account for 45% of whole blood.

Blood Characteristics

Mean fraction of body weight: 8%
Volume in adult body:
- Female: 4-5 L
- Male: 5-6 L
Volume/body weight: 80-85 mL/kg
Mean temperature: 38°C (100.4°F)
pH: 7.35-7.45
Viscosity (relative to water):
- Whole blood: 4.5-5.5
- Plasma: 2.0
Osmolarity: 280-296 mOsm/L
Mean salinity (mainly NaCl): 0.9%
Hematocrit (packed cell volume):
- Female: 37-48%
- Male: 45-52%
Hemoglobin:
- Female: 12-16 g/dL
- Male: 13-18 g/dL
Mean RBC count:
- Female: 4.2-5.4 million/μL
- Male: 4.6-6.2 million/μL
Platelet count: 130,000-360,000/μL
Total WBC count: 5,000-10,000/μL

Functions of the Blood

Transportation:
- Cells: Primarily red blood cells to carry Oxygen
- Plasma: Carries nutrients and wastes that can dissolve in water; carries dissolved proteins made by the liver, endocrine glands, or white blood cells
Regulation:
- Temperature
- pH – buffers
- Volume of water for blood pressure
Defense:
- Cells: Primarily white blood cells to fight invaders
- Cell fragments: Primarily platelets for blood clotting

Plasma Proteins

Plasma is 91.5% water and 7% protein.
Proteins:
- Albumins (60%):
  - Responsible for colloid osmotic pressure; major contributor to blood viscosity; transport lipids, hormones, calcium, and other solutes; buffer blood pH
- Globulins (36%):
  - Alpha (α) Globulins:
    - Haptoglobulin: Transports hemoglobin released by dead erythrocytes
    - Ceruloplasmin: Transports copper
    - Prothrombin: Promotes blood clotting
    - Others: Transport lipids, fat-soluble vitamins, and hormones
  - Beta (β) Globulins:
    - Transferrin: Transports iron
    - Complement proteins: Aid in destruction of toxins and microorganisms
    - Others: Transport lipids
  - Gamma (γ) Globulins:
    - Antibodies; combat pathogens
- Fibrinogen (4%):
  - Becomes fibrin, the major component of blood clots

Hemopoiesis

The making of blood cells.
All begins with “stem cells” (pluripotential) that continually reproduce themselves.
- As child: occurs in the bones, liver, spleen, and kidney
- As adult: occurs in axial bones (especially pelvis and sternum) and long bones – proximal epiphysis
Become committed to form:
- Reticular cells (fibers in lymph system and marrow)
- Mast cells (histamine release in connective tissue)
- Adipocytes
- Myeloid stem cells
- Lymphoid stem cells

Stem Cells

Myeloid Stem Cells:
- Give rise to Erythrocytes, Granulocytes, Monocytes, and Megakaryocytes
Lymphoid Stem Cells:
- Give rise to B lymphocytes and T lymphocytes

Cell Maturation

Myeloid Stem Cells:
- Complete maturation in the bone marrow
- Cell types:
  - Colony-forming unit (CFU)
    - CFU-E
    - CFU-Meg
    - CFU-GM
- Stimulated to produce the final cell by hormones from:
  - Macrophages
  - Kidney
  - Liver
  - Endothelial cells (and others)
Lymphoid Stem Cells
- Complete maturation in the lymph system
- Cell types:
  - T lymphocyte – cell to cell fighter
  - B lymphocyte – becomes plasma cell and makes antibodies
  - Natural Killer Cell – non-specific defense
- Stimulated to produce the final cell by interleukins released from other lymphocytes

Cell Lineages

CFU-E and CFU-Meg:
- Stem cell -> Committed cells -> Precursor cells -> Formed elements of circulating blood
- Proerythroblast -> Erythroblast -> Normoblast -> Reticulocyte -> Erythrocyte
- Megakaryoblast -> Megakaryocyte -> Platelets
CFU-GM:
- Hemocytoblast -> Granulocyte-macrophage colony-forming unit -> Myeloblast -> Neutrophilic myelocyte -> Neutrophil
- Hemocytoblast -> Granulocyte-macrophage colony-forming unit -> Myeloblast -> Eosinophilic myelocyte -> Eosinophil
- Hemocytoblast -> Granulocyte-macrophage colony-forming unit -> Myeloblast -> Basophilic myelocyte -> Basophil
- Hemocytoblast -> Granulocyte-macrophage colony-forming unit -> Monoblast -> Monocyte
CFU-Lymphocytes:
- T progenitor -> T cell precursor (lymphoblast) -> T lymphocyte
- B progenitor -> B cell precursor (lymphoblast) -> B lymphocyte

Erythropoiesis

Process: Hemocytoblast (Stem Cell) -> Myeloid Stem Cell -> Proerythroblast -> Ribosomes are added to produce hemoglobin, which stores Iron.
As hemoglobin is added, the cell becomes red = normoblast.
When 1/3 full of hemoglobin, the nucleus is ejected along with most organelles = reticulocyte.
When cell full of hemoglobin, all organelles ejected = erythrocyte.

Erythrocytes

Contents:
- Hemoglobin
Shape: Donut
Structure:
- Spectrin
- Agglutinogens
  - Antigen if not self agglutinogen
Respiration: Anaerobic
Function:
- Gas transport
- Oncotic Pressure
- Nitric Oxide transport

Blood Types

ABO Blood Types:
- Type A: Agglutinogen A
- Type B: Agglutinogen B
- Type AB: Agglutinogens A and B
- Type O: Neither Agglutinogen A nor B
Rh Blood Types:
- Rh positive: Agglutinogen D
- Rh negative: No agglutinogen D

Blood Types and Heredity

Inherit one AB or (O) and one Rh gene from each parent.
A or B = agglutinogen either A or B - if have both is AB
O = no agglutinogen - makes nothing since is nothing
+ = Rh factor - if have, will make
- = no Rh factor - makes nothing since is nothing
Do not know your genotype, only phenotype

Rh Incompatibility

Occurs when an Rh-negative mother carries an Rh-positive fetus.
During pregnancy or childbirth, fetal blood enters the mother's circulation.
The mother develops antibodies against the Rh antigen.
In subsequent pregnancies with Rh-positive fetuses, maternal antibodies attack the fetal red blood cells.

Hemoglobin (Hb)

Composition:
- 4 globin chains
- 1 heme group per chain
- 1 iron molecule per heme
- 1 oxygen per iron
Gas transport:
- Oxyhemoglobin
- Deoxyhemoglobin
- Carbaminohemoglobin
300 million/cell

Oxygen on Hemoglobin

Cells have no organelles, so they do not use $O<em>2$ to make energy to load and unload the $O</em>2$ , just glucose.
$O_2$ binds best when normal pH and high Oxygen concentrations.
Makes cells bright red (Arterial blood).
$O_2$ binds easily in lungs and releases easily at tissues because concentration is lower and we will see that pH is decreased.
Usually only 1 of the 4 on each hemoglobin is released.
Lack of $O_2$ makes cells darker red (Venous blood).

Necessary Nutrients

Vitamin B12:
- Requires intrinsic factor
Iron:
- Requires protein carriers

Iron Transport and Storage

Process:
1. Mixture of $Fe^{2+}$ and $Fe^{3+}$ is ingested.
2. Stomach acid converts $Fe^{3+}$ to $Fe^{2+}$ .
3. $Fe^{2+}$ binds to gastroferritin.
4. Gastroferritin transports $Fe^{2+}$ to the small intestine.
5. In blood plasma, Fe2+ binds to transferrin.
6. In the liver, some transferrin releases $Fe^{2+}$ for storage.
7. $Fe^{2+}$ binds to apoferritin to be stored as ferritin.
8. Remaining transferrin is distributed to other organs where $Fe^{2+}$ is used to make hemoglobin, myoglobin, etc.

Stimulation for RBC Production

Erythropoietin:
- Produced in:
  - Kidney
  - (Liver)
- Stimulated by:
  - Blood loss
  - Poor hemoglobin
  - Decreased $O_2$
  - Testosterone

Life Cycle of Erythrocyte

Hemocytoblast to Erythrocyte = 5 days
Circulating erythrocyte = @120 days
- Spectrin wears out as no organelles to repair
- Becomes brittle
- Checked for flexibility on the spleen and if not flexible, destroyed

Erythrocyte Life Cycle

Hemocytoblast to Erythrocyte = 5 days
Circulating erythrocyte = ~120 days
- Spectrin wears out as no organelles to repair, becomes brittle.
Checked for flexibility on the spleen and if not flexible, destroyed.

Anemia

Hemorrhagic anemia: Blood loss
Hemolytic anemia: Blood cell lysis – infection – Streptococcus
Aplastic anemia: Normal cells not formed
- May be due to radiation, drugs, chemical exposure, pregnancy
Iron deficiency anemia: Lack of iron
- Inability to make protein carriers or lack of intake
Pernicious anemia: Lack of Vitamin B12, usually lack of intrinsic factor

Abnormal Hemoglobin

Thalassemia: One globin chain is absent or faulty
Sickle Cell Anemia: One globin chain is faulty, and under low $O_2$ conditions, chains clump together and get stiff
Sickle Cell Trait: Recessive gene, so can carry the trait; prevents malaria

Polycythemia

Primary: Cancer
Secondary:
- Dehydration
- Excess EPO
Problem: Viscosity

Leukopoiesis

Myeloid Stem Cells:
- Surface receptor placed
- Responds to hormone
  - Colony stimulating factor
- Monocyte
- Granulocyte
  - Neutrophil
  - Eosinophil
  - Basophil
Lymphoid Stem Cells:
- Surface receptor placed
- Responds to hormones
  - Leukotrines (interleukins)
  - T- Lymphocyte
  - B- Lymphocyte
    - Plasma cell
      - Antibodies
  - NK Cell

Source of Hormones for WBCs

Leukotrines: Lymphocytes
Colony stimulating factors:
- Macrophages
- Endothelial cells

Antigen Presentation by Macrophages

Process:
1. Phagocytosis of antigen.
2. Lysosome fuses with phagosome.
3. Antigen and enzyme mix in phagolysosome.
4. Antigen is degraded.
5. Antigen residue is voided by exocytosis.
6. Processed antigen fragments (epitopes) displayed on macrophage surface.

Role of Monocytes

Patrol the body for invaders
- Circulate as monocytes
- Stationed in key tissues as dendritic cells
  - Lungs
  - Liver
  - Spleen
  - Skin
When called into action, become macrophages “Big-eaters” as eat invaders and garbage
- Internal respiratory burst of lysosomes
Role in the immune system
- Antigen presenting cells

Role of Neutrophils (PMNs)

Contain defensins
- Proteins used to kill bacteria on contact
Contains lysozymes
- Enzymes that destroy certain bacteria
Contain lysosomes
- Hypochlorite, hydrogen peroxide, superoxide
Can phagocytize some bacteria and fungi
Can create external “respiratory burst”
- Extrudes all granules and lysosomes and kills everything in the area, including itself

Neutrophil Action

Neutrophils enter blood from bone marrow.
Margination
Diapedesis
Positive chemotaxis

Emigration (Diapedesis)

Margination
- CAMs – Cell adhesion molecules
  - Cause cells to stick to the endothelial cells
  - Selectins on endothelial cells
  - Integrins on neutrophils
Emigration
Chemotaxis
- Cause cells to leave the blood vessel and come to the site of trauma
Phagocytosis

Role of Eosinophils

Circulate in blood for defense
Stay in respiratory and digestive mucosa
- Primary entry points for parasites
When contact a parasite, degranulate, and release enzymes that eat skin of the parasite
Can phagocytize Antigen/Antibody complexes
- Prevents release of inflammatory chemicals

Role of Basophils

Release Histamine
- Vasodilation
- Attract more WBC’s
Increased in chronic dermatitis or some blood dyscrasias

Role of Lymphocytes

T – Lymphocytes
- The cell to cell fighters
B – Lymphocytes
- Produce antibodies after converting to plasma cells
Most live in lymphoid tissues
Some are always circulating, looking for invaders to the body

Differential WBC Count

Total: 4800-10,800/mm $\text{mm}^3$
Neutrophils: 60-70%
Eosinophils: 2-4%
Basophils: 0.5-1%
Lymphocytes: 20-25%
Monocytes: 3-8%

Leukocytosis vs. Leukopenia

Leukocytosis:
- Invader
- Strenuous exercise
- Anesthesia
Leukopenia:
- Cyclic neutropenia
- Drug induced
- Occurs with Aplastic anemia

Leukemia

Myelocytic: Cancer of monocytes or granulocytes or precursor
Lymphocytic: Cancer of T or B Lymphocytes or precursor
Acute – rapid onset, rapid progression
Chronic – slow progression
Multiple Myeloma: Overgrowth of abnormal plasma cells
Problem – marrow can’t make normal cells, so end up with anemia and infections

Mononucleosis

Excess agranulocytes
Caused by Epstein-Barr virus
Liver and spleen overtaxed by breakdown and slows functioning
- Jaundice
- Enlarged spleen
Virus may enter sensory neurons and cause recurrent ulcers

Differential Blood Count Significance

Total number of cells is important
Ratio of each kind is important

Life Span of WBCs

Neutrophils are first out
- Show up in a few hours of invasion
- Frequently are killed in the battle, so live only hours to days
Monocytes follow to help and clean up
- Show up after 12-20 hours
- Since their job is patrolling and clean-up, can live for months
Lymphocytes always patrol
- Some are memory cells, so can last a life-time

Platelet Formation (Thrombocytes)

Hemocytoblast->Myeloid Stem Cell-> Megakaryoblast-> Megakaryocyte (nuclei multiply, but cell does not divide).
Cell manufactures proteins for clotting. Cell so large it cannot escape the sinusoids of the marrow, and pieces break off = platelets.
These have no organelles, so short life span. Stimulated by hormone thrombopoietin from the liver.

Role of Thrombocytes

Hemostasis
Requires proteins from the blood plasma
Requires prostaglandin secretions from endothelial cells
Initiate clotting when blood vessel walls are not smooth
- Trauma
- Cholesterol plaques

Thrombocytopenia

Lack of platelets
- Secondary to Aplastic anemia
- Secondary to leukemia
- Idiopathic thrombocytopenia purpura:
  - Autoimmune disease

Result of Trauma to a Blood Vessel

Vascular spasm: Blood flow through the injured vessel decreases.
Platelet plug formation: Platelet plug forms.
Coagulation:
- The intrinsic and extrinsic pathways produce Factor Xa.
- The common pathway produces thrombin.
- Thrombin converts fibrinogen to fibrin, and the platelet plug is