Histology

Question 1

What is the nature of bone marrow?

Answer 1

Gelatinous connective tissue responsible for production of blood elements

Question 2

What is the types of bone marrow?

Answer 2

1- Red bone marrow due to predominance of maturing erythrocytes
2- Yellow bone marrow due to predominance of adipocytes

Question 3

What is the sites of red (active) bone marrow?

Answer 3

1- In fetus: located in the most of bone cavities

2- In adult: located in flat bone of skill, pelvic bones, long bone epiphysis, sternum, ribs and vertebrae

Question 4

What is the structure of red bone marrow?

Answer 4

1- Stroma of fixed elements
2- Blood sinusoids
3- Free cells

Question 5

What is the stroma fixed elements in red bone marrow?

Answer 5

1- C.T proper cells:

A- Reticular cells: specialized fibroblastic cells produce reticular fibers and secrete cytokines regulate differentiation of developing cells
B- Fibroblast secrete growth factors
C- Unilocular adipocyte store fat
D- Macrophge for foriegn body and remove iron from degraded old RBCs and store it
2- Bone cells
3- Pericyte
4- Endothelial cells
5- Matrix formed of collagen fibers and glycoprotiens

Question 6

What is the blood sinusoids in red bone marrow?

Answer 6

Irregular wide blood channels that drain toward a larger vein, provide route of entery of mature blood cells into circulation, endothelial cells separated by large gap, their basal laminae are absent and replaced by reticular fibers

Question 7

What are the free cells in in red bone marrow?

Answer 7

Newly formed blood cells, Myeloid progenitors (developing WBCs), Erythroid progenitors (developing RBCs)
The bone marrow forms more WBC than RBC as WBCs have a short life span

Question 8

What are the functions of red bone marrow?

Answer 8

1- Formation of all blood cells except T-lymphocyte
2- Destruction of old RBC by macrophage
3- Storage of iron in macrophage
4- Storage of fat in adipocyte

Question 9

What are the structure and functions of yellow bone marrow?

Answer 9

Structure:
1- Stroma of fixed elements inculding large number of fat cells
2- No free cells
Function:
1- Storage of fat
2- At time of need (in hemorrhage) it’s changed into active red marrow

Site: In shaft of long bone (diaphysis)

Question 10

What is the dominant site pf hemopoiesis after the 6th week of gestation?

Answer 10

Liver, Untill 7th month

Question 11

By the end of wich trimester the hemopoiesis establishes in bone marrow?

Answer 11

Second trimester