Introduction to blood

Question 1

What is the average circulating volume in a typical adult male

Answer 1

average 70kg man - 5L of blood: 1L in lungs, 3L in systemic venous system, 1L in heart and arterial circulation

(less in women - approx. 7-8% body weight)

Question 2

List the functions of plasma

Answer 2

• carriage of physiologically active compounds (plasma)
• clotting (platelets)
• defence (white blood cells)
• carriage of gas (red blood cells)
• thermoregulation
• maintenance of ECF pH

Question 3

Describe the composition of plasma

Answer 3

plasma = 4% body weight, 95% water

• circulating biologically active molecules & compounds
• composition usually kept within strict limits
• divided into 3 categories: Albumin, Globulin a,B,y , fibrinogen and other clotting factors

Question 4

Name the plasma proteins and describe their functions

Answer 4

red blood cells - transporting oxygen from your lungs to your body’s tissues, take the carbon dioxide waste to your lungs for you to exhale

white blood cells- help the body fight infection and other diseases

platelets - form clots and stop or prevent bleeding

Question 5

Define the term oncotic pressure and describe the factors responsible for generation

Answer 5

net direction of movement is determined by balance between colloid oncotic pressure (favours movement into capillary) and capillary hydrostatic pressure (blood pressure) which favours movement out of capillary

Question 6

What is the normal lifespan of red blood cells and platelets in the circulation

Answer 6

red blood cells - 120 days

platelets - 10 days

Question 7

Describe the function of erythropoietin and where it is synthesise

Answer 7

a hormone that the kidneys produce to stimulate production and maintenance of crucial red blood cells

Question 8

What factors may increase secretion of erythropoietin

Answer 8

when oxygen delivery to kidneys is reduced (hypoxia)

• haemorrhage
• anaemia
• cardia dysfunction
• lung disease

Question 9

Name the five main types of white blood cells

Answer 9

• Neutrophils
• eosinophils
• basophils
• monocytes
• lymphocytes

Question 10

Difference between monocyte and macrophage

Answer 10

Monocytes are the largest type of white blood cells and play an important role in the adaptive immunity process

Macrophages are monocytes that have migrated from the bloodstream into any tissue in the body

Question 11

Describe the factors controlling white blood cell formation

Answer 11

Leukopoiesis

controlled by cocktail of cytokines - colony stimulating factors (Granulocytes CSF)

cytokines are released from mature white blood cell

stimulates both mitosis and maturation of leukocytes

stimulate response to infection - bacterial = increase neutrophils, viral = increase lymphocytes

Question 12

Describe platelets

Answer 12

• membrane bound cell fragments, rarely nucleated, 2-4 um diameter
• adhere to damaged vessel walls and exposed connective tissue to mediated blood clotting
• do not adhere to healthy intact endothelium

Question 13

Describe the role of thrombopoietin in platelet formation

Answer 13

• self-renewal and expansion of HSCs
• through stimulation of the proliferation of megakaryocyte progenitor cells
• support of the maturation of these cells into platelet-producing cells

Question 14

What is meant by haematocrit

Answer 14

is a measurement of the proportion of blood that is made up of cells

The value is expressed as a fraction of cells in blood

Question 15

State the normal value for haematocrit

Answer 15

normal range = 40-50%

Question 16

What is meant by blood viscocity

Answer 16

is a measure of the resistance of blood to flow

It can also be described as the thickness and stickiness of blood

Question 17

Describe how viscosity may change in certain circumstances

Answer 17

when blood gets cold, it becomes “thicker” and flows more slowly

increase in red cell mass or increased red cell deformity, increased plasma levels of fibrinogen and coagulation factors, and dehydration can result in increases viscosity