Bone marrow | CHAPTER 5 | Anatomy and Physiology

Bone marrow-The course is designed for the basic understanding of anatomical structures and physiological functions of human body, musculoskeletal system, digestive system, respiratory system; cardiovascular system; urinary system, endocrine system, reproductive system, nervous system, hematologic system, sensory organs, integumentary system, and immune system.The aim of the course is to acquire knowledge and skills regarding anatomy and physiology.

Bone marrow

Bone marrow:

Bone marrow is a soft vascular tissue which occupies the medullary cavity and the spaces between trabeculae of the spongy bone that produces about 95 percent of the body’s blood cells. In adults, the blood-producing marrow is found mainly in the flat bones of the skull, pelvis, ribs, and sternum.

Types:

1. Red bone-marrow.
2. Yellow bone-marrow.
3. List the Functions and Distribution of red bone-marrow.

Functions of red bone marrow:

1. Formation of RBC
2. Formation of WBC
3. Formation of Platelets.
4. Destruction of RBC by macrophage.

Distribution of red bone marrow:

1. Vertebrae
2. Sternum.
3. Rabs
4. Clavicles.
5. Bones of the pelvis.
6. Cranial bones
7. Epiphysis of femur and humerous

Platelet

Platelet: Platelets (also called thrombocytes) are the smallest disc like cells among the blood cells formed in the bone marrow from megakaryocytes. Platelets have no nuclei like RBC.

Normal count: 150,000 to 350,000/cmm of blood.

Morphology:

Cell size: 2-4 µm.

Shape: Discoid.

Nucleus: Absent

Cytoplasm: Two regions are seen in light microscope.

1. A peripheral clear region.
2. A central darker region.

These regions contain platelet tubules & granules.

Color: Light blue cytoplasm.

Lifespan: 8-12 days.

Site of destruction: Spleen.

Substances secreted: Thromboxane, Serotonin, Blood clotting factors etc.

Substances storage & transport: Histamine, 5-HT etc.

Functions of platelets:

a) Platelet helps in hemostasis by-

i. Vascular smooth muscle contraction

ii. Platelet plug formation

iii. Clot formation.

iV.  Clot retraction.

b) Helps in the formation of new vascular endothelium.

c) Platelets liberate some proteins (5HT, Histamin) which increases vascular permeability & helps in inflammatory reaction.

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