Blood cells

Question 1

Define Hematology.

Answer 1

> Hematology is the study of the blood its composition and its function.

Question 2

Define blood

Answer 2

• Blood is an ‘aqueous body fluid’.
– i.e. It is water containing a whole range of substances.
• It is contained in a complex network called the vascular system and is pumped around the body by the heart.

Question 3

What are the functions of blood?

Answer 3

1. Transportation
2. Regulation
3. Protection

Question 4

Transportation as a function of blood

Answer 4

Oxygen from the lungs to the cells of the body and carbon
dioxide from the cells to the lungs.
• Nutrients from the gastrointestinal tract to body cells.
• Hormones form the endocrine glands to other body cells.
• Heat that regulates body temperature
• Waste products away from the cells such as excess water.

Question 5

Regulation as a function of blood

Answer 5

• Electrolyte balance (that is a substance containing free ions, that behaves as an electrically conductive medium).
• Helps to regulate pH.

Question 6

Protection as a function of blood

Answer 6

Certain blood cells protect against blood loss (clotting
mechanism).
• Leukocytes provide immunity against infection

Question 7

Blood composition

Answer 7

Plasma (55%)
• Erythrocytes (RBCs)
• Leukocyte (WBCs)
• Thrombocytes (platelets)

Question 8

What is plasma composed of?

Answer 8

Water and dissolved solutes:
• Ions (mostly Na+)
• Nutrients
• Metabolic waste products
• Hormones
• Enzymes
• Antibodies
• Proteins
Cells use plasma amino acids to make their own proteins
• Serum is plasma without the clotting factors (fibrinogen)
– When blood is left to clot

Question 9

Plasma proteins

Answer 9

– Albumins
– Globulins
– Fibrinogens

Question 10

Albumin

Answer 10

-produced by the liver
• most abundant protein in the plasma
• provides osmotic pressure to maintain blood volume
(i.e. draw water from the surrounding tissue fluid into
capillaries)
– Without albumin, the high pressure in the blood vessels would force more fluids out into the tissues. Albumin maintains the proper distribution of fluid between vessels and tissues.
The balance between the two forces differs at different points on the capillaries.
• At the arterial end of a vessel, the
hydrostatic pressure is greater than the
osmotic pressure, so the net movement
favors water and other solutes being
passed into the tissue fluid.
• At the venous end, the osmotic pressure is
greater, so the net movement favors
substances being passed back into the
capillary. This difference is created by the direction of the flow of blood and the
imbalance in solutes created by the net
movement of water favoring the tissue
fluid

Question 11

Globulins

Answer 11

-α and β:
– produced by the liver
– transport lipids and fat-soluble vitamins
• γ :
– antibodies produced by B-lymphocytes (WBCs) defend against bacteria and viruses

Question 12

Fibrinogen

Answer 12

• Important clotting factor produced by the liver

- Fibrinogen —> fibrin threads (insoluble)

Question 13

Red blood cells, what are they?

Answer 13

Are the most abundant cells of the body

• Necessary for the delivery of oxygen to the tissues.

Question 14

The function of red blood cells

Answer 14

• Transport of haemoglobin
– Haemoglobin carries oxygen from the lungs to the tissues.
• Carbonic anhydrase forms bicarbonate ion (HCO3
- ) from CO2 and waters.
– Carries CO2 in the form of HCO3- from the
tissues to the lungs, where converted to CO2; expelled as waste.

Question 15

Explain the diagram

Answer 15

CO2 from tissue to red blood cell and oxygen from rbc to tissue.

HbO2 –>O2 + Hb

Question 16

Hemoglobin

Answer 16

• Heme (iron) + globulin (globular protein)
• RBCs concentrate hemoglobin up to 34g per 100 ml cells
(max).
• Iron bound to heme combines with O2 in the lungs and
release oxygen in the tissues

Question 17

What are the shape and size of RBCs?

Answer 17

• Average volume is 90-95 cubic um.
• Biconcave
– Provides increased surface area through 
which gas can diffuse.
– Places the cell membrane closer to oxygen 
carrying hemoglobin
• Shape can change rapidly as cells 
squeeze through the capillaries.

Question 18

What is the normal concentration of RBCs in the

blood?

Answer 18

– Men: 5.2 million per cubic mm

– Women: 4.7 million

Question 19

How are RBCs adapted to their

function?

Answer 19

• Lack nuclei
– More space for hemoglobin
– Cannot divide (reproduce)
• Lack mitochondria
– Anaerobic metabolism
– Do not use the oxygen they carry
• Contain carbonic anhydrase
– Catalyses the formation of bicarbonate ions (for 
CO2 transport)

Question 20

Where are RBCs produced?

Answer 20

• Early weeks of embryonic life: - Yolk sac
– Are nucleated
• Middle trimester: - Liver
• From the last month of gestation onwards: Bone
marrow
• Up to 5 yrs old:
– All bones produce RBCs
• After 20yrs:
– Production stop in the marrow of the long bones, except the proximal portions of the humeri and tibiae
• Produces in the membranous bones (vertebrae,
sternum, ribs)
– Becomes less productive as age increases