blood physiology

Question 1

functions of the blood:

Answer 1

Maintenance of cellular function – through the establishment of correct ion gradients
between the intracellular and
• extracelluar phases.
• Gaseous exchange - carriage of O2 and CO2 between tissues & lungs.
• Delivery of other nutrients - between the gut, liver and kidney for absorption, metabolism
and excretion.
• Carriage of hormones - endocrine gland secretions are carried to target tissues.
• Protection against invading organisms - blood provides an immunological function.
• Thermoregulation - heat is exchanges with the outside world by regulating blood flow to the
skin.

Question 2

The blood plasma consists of:

Answer 2

plasma - it consists of an ionic solution, containing also nutrients, waste products, gases
and larger molecules such as albumin, globulin and clotting factors. Serum is the residual
after fibrinogen removal – a clotting factor
• a cellular component – comprising red cells (erythrocytes), white cells (leukocytes) and
platelets (thrombocytes).

Question 3

What does the colloid osmotic pressure regulate?

Answer 3

the passage of water and solutes through the walls of the capillaries.

Question 4

What is the osmolality of blood plasma?

Answer 4

280-300 mosmol/kg of water

Question 5

What is the pH of blood plasma?

Answer 5

7.35-7.45

Question 6

What is the function of globulins

Answer 6

transport lipids and fat soluble vitamins in the blood.

Question 7

What is a fibrinogen?

Answer 7

a clotting factor circulating in the blood

Question 8

What does the haematocrit ratio describe?

Answer 8

it describes the proportion of the total blood volume occupied by the erythrocytes.

Question 9

Describe the colloid oncotic (osmotic) pressure.

Answer 9

The key function of the blood plasma proteins is to maintain an adequate fluid volume. Sometimes the capillaries are leaky to water and small solutes into the extracellular compartment due to hydrostatic pressure of about 25 mmHg.
The plasma proteins prevent this from happening by asserting an colloid osmotic absorption pressure of 25mmHg. A decrease of osmotic pressure (decrease in plasma proteins or liver failure) or an increase in hydrostatic pressure (congestive heart failure) will result in leakage of water into extravascular space–oedema.

Question 10

How does the plasma proteins (immunoglobins) help to prevent attack by antigens?

Answer 10

1. agglutination: forming an immune complex with large antigens
2. opsonization: encouraging phagocytosis

Question 11

concentration of red blood cells in the blood:

Answer 11

4.5-6.0 x 10^12 per litre of blood.

Question 12

function of red blood cells:

Answer 12

transport the respiratory gases oxygen and carbon dioxide around the body. they are small, circular and biconcave discs of 7-8 micrometers diameter and do not possess a nucleus. They can thin and can squeeze through holes in capillaries. Their shape gives a large surface area to volume ratio which promotes efficient gas exchange. They are synthesized by the red blood precursors in the bone marrow.

Question 13

Which hormone facilitates maturation of the RBC?

Answer 13

erythropoietin

Question 14

What is anemia?

Answer 14

it is a condition where oxygen carriage in the hemoglobin is low. It can be due to a lack in iron, folic acid and vitamin B12 required for RBC produced and red cell maturation. It is also a condition with defective hemoglobin with poor oxygen-carrying properties: sickle cell anemia.

Question 15

What is the normal percentage for hematocrit in men?

Answer 15

45%

Question 16

What is special about type O blood?

Answer 16

it is a universal donor as it has two types of antibodies A and B.

Question 17

What is special about type AB blood?

Answer 17

It is a universal receiver as it has no antibodies.

Question 18

Why must blood transfusion be careful with blood types?

Answer 18

to avoid agglutination of blood

Question 19

What antibodies do type A and type B have?

Answer 19

B antibodies and A antibodies

Question 20

What is hemolytic disease?

Answer 20

The rhesus factor is another blood group that exists. Generally those who lack the Rh antigen also does not have the plasma rhesus antibody. Rh-negative women is pregnant, might have the rhesus antibodies from the foetus if the father if Rh-positive. The maternal antibodies can cross to the placenta and kill the red cells in the foetus causing hemolytic disease.

Question 21

Describe white blood cells

Answer 21

they are larger than RBCs and possess a nucleus. they are less numbered than red blood cells. contain 7 x 10^9 white cells per liter. They protect the body from diseases. They are being transported rapidly to specific areas of infection and inflammation to give powerful defense against invading organisms.

Question 22

What is diapedesis?

Answer 22

The process of passing through walls in capillaries and enter tissue spaces

Question 23

There are three major types of white blood cells. they are:

Answer 23

granulocytes; monocytes; lymphocytes

Question 24

Granulocytes are divided into three groups types. they are:

Answer 24

Neutrophils; eosinophils; basophils

Question 25

What is the function of granulocytes?

Answer 25

Their function is to destroy invading organisms. They are attracted to damaged sites in the tissues by signals sent from injured tissues or foreign organisms. These cells engulf them and destroy them with enzymes in the lysosomes.

Question 26

What is the function of monocytes?

Answer 26

They are macrophages, larger than other white cells. They engulf foreign organisms and process and ingest antigens for future lymphocyte recognition.

Question 27

what is the function of lymphocytes?

Answer 27

There are two types of lymphocytes: T cells and B cells.
B cells produce more antibodies when encountering foreign particles (antigens) and
T cells participate in cell mediating response by cell lysis. Others modulate B cells into antibody-producing cells.

Question 28

what are platelets?

Answer 28

The control bleeding and maintain the integrity of the vascular endothelium. They are cell fragments that are formed in the bone marrow by budding off from the cytoplasm of large cells called megakaryocytes. They are 2-4 micrometers in diameter and survive for ten days.

Question 29

what is haematopoiesis?

Answer 29

the formation of blood cells

Question 30

What is haemostasis?

Answer 30

When a blood vessel is damaged, excessive blood loss from the wound, is prevented by a process
called haemostasis. This involves a series of events - vasoconstriction, platelet aggregation and
blood coagulation (clot formation). Later, blood vessel repair, clot retraction and dissolution
complete the healing process.

Question 31

When the vascular endothelium is damaged, there is a vascular constriction response by vascular smooth muscle to narrow the vessel. What mediates this?

Answer 31

humoral factors and mechanical stimulation

Question 32

platelets build up and adhere to the damaged site. This process is self perpetuating as the platelets secrete what?

Answer 32

ADP and 5-hydroxytryptamine

Question 33

What do the platelets also synthesize?

Answer 33

arachidonic acid and thromboxane A2

Question 34

ADP, 5-hydroxytryptamine, arachidonic acid and thromboxane A2 all trigger what response?

Answer 34

Trigger platelets to adhere to the damaged wall and form platelet plug.

Question 35

Define and describe coagulation

Answer 35

The process by which fibrin strands create a mesh that binds blood components together to form a blood clot.
Involves sequential blood clotting factors.
Most of the clotting factors are serine proteases related to trypsin that are synthesized in the liver.
The clotting factors undergo post-translational modification requiring vitamin K.

Question 36

There are two pathways for clotting, what are they

Answer 36

extrinsic and intrinsic pathways

Question 37

Describe the extrinsic pathway:

Answer 37

It requires Ca2+.

• damage to tissue exposes the blood to tissue factor, which is expressed on the surface of smooth muscle cells and the fibroblasts of the tunica adventitia (the outer layer of the vessel wall), the exposed tissue normally remains at the site of injury and this localizes the formation of blood clot.
• The contact of blood with tissue factor sets the clotting process in motion. Tissue factor combines with factor VII (proconvertin) and proteases present in small amounts in the plasma activate the bound factor VII by the cleavage of a single peptide bond. The tissue factor VIIa complex then activates factors IX and X.
• on the surface of platelets, factor Xa combines with factor Va and converts prothrombin to thrombin as described below for the final common pathway. It also speeds up the activation of factor VII that is complexed with tissue factor (positive feedback).

Question 38

Describe the intrinsic pathway

Answer 38

• The slower pathway of the two
• activates when blood contacts with injured vessel wall (and not tissue factor)
• all of the elements required to activate it are present in normal blood.
• contribute to the formation of activated factor X (factor Xa) at the end of the first stage of coagulation.
• factor Xa acts on prekallikrein to release kallikrein
• it forms complex with higih molecular weight kininogen
• complex activate more factor XIIa (positive feedback)

Question 39

The final common pathway. Fibrin is formed. How is it formed?

Answer 39

thrombin cleaves fibrinogen to release fibrin monomers, which undergo end-to-end polymerization to form long strands of insoluble fibrin.

Question 40

Thrombin also activates which factor which is synthesized in the liver? what is this factor secreted by?

Answer 40

Factor XIII; alpha-granules of the platelets.

Question 41

What does factor XIIIa do?

Answer 41

stabilizes the fibrin by forming cross links between the long polymerized strands of fibrin to form a mesh like structure that traps blood constituents to form the clot and bind the edges of of the damaged vessel together.

Question 42

Identify a positive feedback loop of thrombin.

Answer 42

thrombin activates factors V and VIII and so forms more thrombin

Question 43

What is von Willebrand’s disease associated with?

Answer 43

prolonged bleeding time.