Chapter 5: Leucocytes (White Blood Cells)

Question 1

What are leukocytes?

Answer 1

Mobile units of the body’s protective system.

Question 2

How are leukocytes produced?

Answer 2

They are produced from pluripotential stem cells (just like platelets). Under the effect of interleukins, the uncommitted stem cells are converted to committed stem cells and divide to give to two separate stem cell lines:
Myeloid line:- gives rise to three types of granulocytes, monocytes, and megakaryocytes.
Lymphoid line: gives rise to lymphocytes.

Question 3

Myeloid line

Answer 3

Granulocytes, monocytes, and megakaryocytes.

Question 4

Lymphoid line

Answer 4

Lymphocytes

Question 5

Leucocytic count

Answer 5

Adult human has approximately 4000-11000 WBC’s/mm3.

Question 6

Leucocytosis

Answer 6

Increase in the number of leukocytes up to 20,000/mm3 or more.
It occurs in any condition of tissue destruction like:
1. Tissue inflammation with pus formation
2. Myocardial infarction

Question 7

Leukemia

Answer 7

Malignant disease of the bone marrow leading to uncontrolled production of abnormal WBC’s that cannot protect the body against infection.

Question 8

Agranulocytosis

Answer 8

Bone marrow stops producing WBC’s. It is a rapidly fatal disease, which occurs as a result of exposure to radiation or drugs and toxins.

Question 9

What is an inflammatory response?

Answer 9

The response of living tissue to injury.

Question 10

What are the reasons of inflammatory response?

Answer 10

1. Infection
2. Trauma
3. Extremes of hot and cold
4. Chemical agents

Question 11

How is the process of inflammatory response characterized?

Answer 11

Local vasodilation causing redness, heat, and increased vascular permeability with resultant swelling.

Question 12

What are the cells involved in inflammatory response?

Answer 12

Mainly monocytes and neutrophils.

Question 13

What are the steps involved in inflammatory response?

Answer 13

1. Margination
2. Diapedesis
3. Chemotaxis and Ameboid movement
4. Phagocytosis

Question 14

Margination

Answer 14

The process starts by the action of other substances produced at the site of inflammation on the nearby capillary walls leading to the sticking of the neutrophils and the monocytes to the endothelial cells.

Question 15

Diapedesis

Answer 15

Both cells squeeze through the pores between endothelial cells.

Question 16

Chemotaxis and ameboid movement

Answer 16

Then they move by ameboid movement towards the site of inflammation.
- Substances that attract the phagocytes to the site of inflammation are called Chemotaxis and they include breakdown products of inflamed tissue.
- Sometimes bacterial toxins repel neutrophils, this is called negative Chemotaxis.

Question 17

Chemotaxins

Answer 17

Substances that attract the phagocytes to the site inflammation.
They include breakdown products of inflamed tissues.

Question 18

Negative chemotaxis

Answer 18

Sometimes bacterial toxins repel neutrophils.

Question 19

Phagocytosis

Answer 19

The bacteria then binds to receptors on the phagocytic cell membrane and is engulfed into the cell.
- A phagocytic vacuole is then formed in which lysosomes fuse and releases their enzymes to kill the bacteria.
- Opsonization: when immunoglobulins and complement proteins coat the bacteria to make them tasty to phagocytes.