Anatomy - Blood

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Blood is the only...

fluid tissue (connective) in the body having both a solid and liquid component.

What causes the colour of blood to vary?

Oxygen levels.

What is the pH of blood?

7.35-7.45

What is the temperature of blood?

38 degrees Celsius

What is the volume of blood in a healthy adult?

5-6 litres.

What percentage of a healthy adults body weight is made up of blood?

8%

What percentage of a blood sample is made up of plasma?

approx. 55%

What percentage of a blood sample is made up of the formed elements?

approx. 45%

What are the components of plasma?

- water
- salts (electrolytes)
- plasma proteins
- substances transported by blood

What are the formed elements?

- erythrocytes
- leukocytes
- basophils
- eosinophils
- neutrophils
- monocytes
- lymphocytes
- platelets

Hematopoiesis

- The process of blood cell formation
- Occurs in red bone marrow

All blood cells are derived from a common stem cell, what is it?

hemocytoblast/ pluripotential stem cells

What are the 3 phases of hematopoiesis?

1. Mesoblastic
2. Hepatic
3. Medullary (Myeloid)

Mesoblastic phase

Begins around the 19th day of embryonic development. Forms the primitive RBC's and eventually early blood vessels.

Hepatic phase

5-7 weeks - characterized by recognizable clusters of developing cells. Represents definitive hematopoiesis. The liver is the main site.

Medullary (Myeloid) Phase

4-5 month of fetal development, the bone marrow takes over cell production. Becomes the main site of hematopoiesis.

Erythropoiesis

Red blood cell development/ production.

Granulopoiesis

Granulocyte development/production.
Neutrophils, Eosinophils, Basophils

Thrombopoiesis

Platelet development/production.

Why do RBCs differ from other blood cells?

- anucleate
- contain few organelles; lack mitochondria
- make ATP by anaerobic means
- essentially a sack of hemoglobin
- shaped like biconcave discs

How is the shape of RBCs beneficial?

The biconcave shape gives the cell a high surface to volume ratio which is essential for gas exchange.

What is the life span of RBCs?

120 days.

What are reticulocytes?

young RBCs which enter the blood to become oxygen - transporting erythrocytes.

Polychromasia

Young RBCs still contain residual RNA, therefore on the blood smear they appear lavender/purple in colour.

Erythropoietin

The hormone that controls the rate of RBC production.
Kidneys produce most erythropoietin as a response to reduced oxygen levels in the blood.

5 steps that maintain homeostasis: normal blood oxygen levels

1. Stimulus - Low blood oxygen carrying ability
2. Kidneys (and liver, to a smaller extent) release erythropoietin.
3. Erythropoietin stimulates red bone marrow.
4. Enhanced erythropoiesis increases RBC count.
5. Oxygen carrying ability of blood increases.

Factors that could lead to low blood oxygen carrying ability

Decreased RBC count
Decreased amount of hemoglobin
Decreased availability of oxygen

Hemoglobin

Iron bearing protein that binds oxygen.

How many oxygen molecules can one hemoglobin bind to?

4

Anemia

Decrease in the normal number of RBCs in circulation.
Abnormal or deficient amount of hemoglobin in the cells.
Not a disease, but the result of an underlying condition.

Anisocytosis

Variation in cell size

Erythrocyte sizes

Normocytic- Normal sized RBCs
Microcytic- Smaller than normal sized RBCs
Macrocytic- Larger than normal sized RBCs

Normochromic

Normal amount of hemoglobin content in the RBC

Hypochromic

Less than normal amount of hemoglobin content in the RBC

Hyperchromic

Higher than normal amount of hemoglobin content in the RBC

Poikilocytes

Abnormal shaped RBCs

Sickle cell anemia

When one amino acid on the beta chain of the hemoglobin molecule is substituted for another.
This abnormal hemoglobin becomes spiky and sharp when oxygen is unloaded or the oxygen content in the blood is below normal.

If an individual carries one copy of the defective gene that causes sickle cell anemia, are they symptomatic?

Generally no, Most individuals need to have two copies of the defective gene in order to display symptoms.

What are the consequences of sickle cell anemia?

When the cells sickle in areas of low oxygen, they can rupture easily and block blood vessels. This interferes with oxygen delivery to those areas and causes extreme pain.

Polycythemia

A disorder characterized by an abnormal increase in the number of red blood cells in the blood. This increase slows blood flow and increases blood viscosity.

A decrease in RBC number that results from a sudden hemorrhage leads to what kind of anemia?

Hemorrhagic anemia

A decrease in RBC number that results from lysis of RBCs due to a bacterial infection leads to what kind of anemia?

Hemolytic anemia

A decrease in RBC number that results from a lack of vitamin leads to what kind of anemia?

Pernicious anemia

A decrease in RBC number that results from destruction of bone marrow by cancer, radiation or certain medications leads to what kind of anemia?

Aplastic anemia

inadequate hemoglobin content in RBCs that results from a lack of iron in the diet or slow/prolonged bleeding leads to what kind of anemia?

Iron-deficiency anemia

Leukopoiesis

Refers to the development/productions of all WBCs

lymphopoiesis

lymphocyte production/development

monopoiesis

monocyte development/production

Diapedesis

the passage of blood cells through the intact walls of the capillaries, typically accompanying inflammation.

amoeboid motion

The flowing movement of the cytoplasm of a phagocyte.

granulocytes

contain lobed nuclei and the granules in their cytoplasm can be stained.

how can neutrophils, eosinophil, and basophils be distinguished by their granules?

neutrophils- contains fine tan/pinkish granules.
eosinophils- larger orange/pinkish granules.
basophils- larger black/purple granules, in the cytoplasm and on the nucleus.

Agranulocytes

lack visible cytoplasmic granules
nuclei are spherical, oval, or kidney shaped
includes lymphocytes (round to oval nucleus) and monocytes (irregular shaped nucleus)

WBCs from most to least abundant

neutrophils, lymphocytes, monocytes, eosinophils, basophils

neutrophil

most numerous WBC.
multilobed nucleus (segmented) or banded.
cytoplasm stains tan/pink and contains fine granules.
function as phagocytes at active sites of infection.
play a role in natural immunity.
numbers increase during infection.

eosinophils

nucleus stains blue-red.
brick red cytoplasmic granules.
function is to kill parasitic worms; play a role in allergy attacks.
play a role in natural immunity.

basophils

rarest of the WBCs.
large histamine-containing granules that stain dark blue to purple.
release histamine (vasodilator) at sites of inflammation.
contain heparin (anticoagulant).
play a role in natural immunity.

lymphocytes

slightly larger than RBCs.
have a large, dark purple nucleus that is round/oval shaped.
can have larger lymphocytes with more abundant cytoplasm.
reside in lymphatic tissues.
play a role in adaptive immune response.

monocytea

largest or the WBCs.
distinctive U or kidney shaped dark purple nucleus.
function as macrophages when they migrate into tissues.
important in fighting chronic infection.
play a role in natural immunity.

Leukocytosis

Abnormally high WBC count.
Normal response to an infection, or potentially more severe disease states.

Leukopenia

Abnormally low white blood cell count.
Commonly caused by certain drugs, such as corticosteroids and anticancer agents.

Leukemia

Bone marrow becomes cancerous.
Numerous immature WBC are produced.

Neutropenia

A decrease in the number of neutrophils in circulation.

Neutrophilia

Increase in the number of neutrophils in circulation.

Monocytosis

increase in the number of monocytes in circulation.

Eosinophilia

increase in the number of eosinophils in circulation.

basophilia

increase in the number of basophils in circulation.

megakaryocyte

large platelet precursor cell found in the bone marrow

Megakaryopoiesis

production of megakaryocytes

Thrombocytopenia

decrease in platelets in peripheral blood.
can lead to bleeding because platelets are essential for clotting process.

thrombocytosis

increase in platelets in peripheral blood.
may lead to clotting in the body.

primary hemostasis

blood vessels and platelets work together to form a temporary platelet plug.

secondary hemostasis

activation of the coagulation proteins with the main objective to make fibrin and stabilize the temporary platelet plug.

Fibrinolysis

the gradual digestion and dissolving of the clot following healing.

Hemostasis: Vasoconstriction

Leads to vascular spasms.
Immediate response to blood vessel injury.
Spasms narrow the blood vessel, decreasing blood loss, and aid in the clotting process.

Role of platelets

Surveillance cells that maintain the blood vessel integrity, and the first line of defense when a blood vessel is breached.
Trigger primary hemostasis when exposed to the sub-endothelial membrane/inflammatory proteins at the site of vessel injury.
Metabolically active cells that basically initiate and control hemostasis.

Primary hemostasis: Adhesion

Platelets bind to exposed collagen and the release of vWF from the exposed collagen, links platelets to the collagen.
platelets have receptors that also bind to the vWF to reinforce adhesion process.

What is vWF?

von Willebrand factor

Primary hemostasis: Aggregation

Platelets bind to one another via the platelet receptor GP IIb/IIIa.
Fibrinogen is the bridge that binds to the platelets via the GP IIb receptor in the presence of ionized calcium.
fibrinogen binding is essential for platelet aggregation.

Thromboxane A2

Produced by activated platelets and stimulates the activation of other platelets - recruits others to the site for aggregation.

Coagulation system - secondary

main purpose is to produce fibrin and stabilize the primary platelet plug.
mediated by coagulation proteins via different pathways: intrinsic, extrinsic, common.

Intrinsic pathway

Contact of internal factors to negatively charged surfaces (collagen)

Extrinsic pathway

Activated via external factors due to blood vessel breach - exposure to collagen

common pathway

factors that the intrinsic and extrinsic have in common.

How long does blood take to clot?

3-6 minutes

Thrombus

a clot that develops and persists in an unbroken blood vessel
can be deadly in areas such as the lungs

embolus

A thrombus that breaks away and floats freely in the bloodstream
Can later clog vessels in critical areas such as the brain

Hemophilia

Hereditary bleeding disorder (x-linked)
Normal clotting factors are missing
Minor tissue damage can cause life-threatening prolonged bleeding.

Loss of 15 to 30 % of blood causes what?

pallor and weakness.

Loss of over 30% of blood causes what?

shock, which can be fatal

Transfusion reactions

Lysed red blood cells release hemoglobin into the blood stream
Freed hemoglobin may block kidney tubules, causing kidney failure and death
Fever, nausea, and vomiting can also result.

Blood types are based on the presence of two antigens

Type A and B

Presence of both antigens A and B is called

type AB

presence of antigen A is called

type A

presence of antigen B is called

type B

lack of both antigens A and B is called

type O

Who is the universal recipient?

Type AB

Who is the universal donor?

Type O

how did the Rh blood group get its name?

Named because of the presence or absence of one of eight Rh antigens that was originally defined in Rhesus monkeys

What happens when a mother is Rh- and the child is Rh+

Hemolytic disease of the newborn.
RhoGAM shot can prevent buildup of anti-Rh+ antibodies in mothers blood.
Binds the positive Rh antibodies and prevents them from eliciting an immune response.