Structure and function of blood

Question 1

What are the major cellular components of blood? Describe them

Answer 1

Red blood cells (erythrocytes) - biconcave, no nucleus, transport oxygen, remove CO2, contain Hb, porphyrin ring surrounding central Ferrous (iron) ion.

White blood cells (leukocytes) - colourless, involved in immune response , can be granulated or not granulated

Platelets (thrombocytes) - cytoplasmic fragments, no nucleus, membrane bound, granulated

Question 2

How are white blood cells classified morphologically?

Answer 2

Into granulocytes and granulocytes:

Granulocytes are neutrophils, basophils, eosinophils

Agranulocytes - Monocytes, lymphocytes, macrophages

Question 3

Describe the structure and function of neutrophils

Answer 3

Phagocytes, kill bacteria and fungi

Main mediators of innate immunity

Polymorphonuclear- irregular, multi-lobed nucleus

Prominent cytoplasmic granules

Question 4

Describe the structure and function of eosinophil

Answer 4

Bi-lobed nucleus, granules stain red with eosin

Question 5

Describe the structure and function of basophils

Answer 5

Bi-lobed nucleus, granules stain blue/purple with basic dyes

Question 6

What are the mononuclear white blood cells?

Answer 6

• Monocytes
• Lymphocytes

These have NO granules, and large, regular nuclei

Question 7

What is the function of lymphocytes?

Answer 7

• Main role in adaptive immunity
• B lymphocytes - produce specific antibodies
• T lymphocytes - produce cytotoxic granules that eat up tissue

Question 8

What is the structure of haemoglobin?

Answer 8

Porphyrin ring with central ferrous ion, protein tetramer made of 4 polypeptide chains, each polypeptide chain has a haem group attached to it

Question 9

What is the role of plasma?

Answer 9

Transports essential materials, waste products, carbohaydrates, lipids

Question 10

What is plasma?

Answer 10

Fluid containing:
Water
Salts
Proteins
Organic molecules e.g. metabolites, carbohydrates, lipids
Clotting factors

Positive ions Na and potassium, calcium, magnesium

Question 11

What is serum?

Answer 11

Fluid left after blood clotting

Question 12

How do blood cells develop from haematopietic stem cells?

Answer 12

• begin with multipotent haematopoietic stem cells

Through series of steps cells develop through targeted processes to specific cell type they will later become

Cells develop into myeloid/lymphoid progenitor cells or red blood cells or platelets

Question 13

What is the average red blood cell life span?

Answer 13

120 days

Question 14

What is the normal value for blood volume?

Answer 14

5 litres

Question 15

What is the normal value for plasma volume

Answer 15

2.5/3 literes

Question 16

What is the normal value for haematocrit reading

Answer 16

0.4/0.5

Question 17

Describe the appearance of blood after centrifuging

Answer 17

Bloody splits into red cell at bottom, buddy white layer of white blood cells , and plasma on top

Question 18

What are the components of a full blood count test?

Answer 18

Haemoglobin (Hb): concentration of haemoglobin within the blood. Hb is the protein in red blood cells which carries oxygen. It is the first value you should look at. Low haemoglobin = ‘anaemia’.
Mean corpuscular volume (MCV): mean volume of the red blood cells (‘-cytic’). This is the main method used to classify anaemia (macrocytic = large cells; normocytic = normal cells; microcytic = small cells).
Reticulocyte count: the number of immature red blood cells. Increased in blood loss and haemolytic anaemia because the bone marrow works harder to replace lost cells. Decreased if there is impaired red blood cell production in the bone marrow.
Red cell count (RCC): the concentration of red blood cells within the blood
It may be increased due to: reduced plasma volume (e.g. dehydration), or increased red blood cell production (e.g. polycythaemia rubra vera)
It may be decreased due to: increased plasma volume (e.g. pregnancy), or reduced red blood cell production/red blood cell loss (e.g. bone marrow failure, bleeding, anaemias)
Haematocrit (HCT)/packed cell volume (PCV): percentage of the total volume of blood accounted for by red blood cells. Causes of abnormalities are similar to the RCC but the haematocrit is based on volume so is also affected by the red cell volume (MCV).
Mean corpuscular haemoglobin (MCH)/haemoglobin concentration (MCHC): the mean quantity/concentration of haemoglobin within the red bloods cells. This affects the colour of the cells (‘-chromic’: hypochromic = pale; normochromic = normal red).
Most normocytic and macrocytic anaemias are normochromic
Most microcytic anaemias are hypochromic (except anaemia of chronic disease)
Red blood cell distribution width (RDW): measure of the variation of red blood cell volumes. It is used in conjunction with MCV to determine if anaemia is due to a mixed cause or a single cause. Raised red cell distribution width = ‘anisocytosis’.