3 blood platelets and bone marrow

Fragments of cytoplasm covered with a membrane with no nucleus (not true cells). Origin: megakaryocytes. Size: 2 - 4 μm. Life span: 5-10 days. Shape: oval or rounded discs. Number: 150.000 - 400.000 / mm3. Histol., LN.1&2 Dr.Mona Farouk Level 1- Semester 2- Block 3- Module 3B- IBL Page | 15 Function: (Haemostasis) 1. Serotonin → V.C. 2. Platelet aggregation. 3. Red thrombus (coagulation) Thromboblastin changes prothrombin into thrombin → change fibrinogen into fibrin network → attraction of RBCs → closes blood vessels and stops bleeding. 3- Granulomere: • α granules: fibrinogen. • β granules: mitochondria. • δ granules: serotonin, ATP, ADP and calcium. • λ granules: lysosomes. • Glycogen granules. Active(red) bone marrow structure 1. Stroma of fixed cells •Reticular branched cells •Fat cells •Endothelial cells •Osteogenic cells •Pericyte cells 2. Bl. Sinusoides 3. Free cells Sites: -In foetus: most of the bone. In adult: •Flat bone •Sternum. • Ribs and clavicle. •Vertebrae. Function: 1. Formation of blood cells. 2. Destruction of old RBCs. 3. Storage of iron. 4. Storage of fat. InActive (yellow) bone marrow 1.Stroma of fixed cells: • Undiff. Mesencymal cells • Macrophage • Reticular cells 2. Large number of adipose cells 3. No free cells Present in adults: •In shafts of long bone. 1. Storage of fat 2. On need , it changes into active red bone marrow. for contact shereenhamed200@gmail.com Telegram channel https://t.me/drshereenhamed​​​​