Haematopeisis. Flashcards
What are the main features of blood?
1- circulates around the entire body via blood vessels, primarily arteries, veins and capillaries
2- Makes up 7-8% of body weight
3- typically 38 degrees C
4- slightly alkaline: 7.35-7.45
What is the function of blood?
Carry to body tissues:
-O2, nutrients, hormones, H2O, solutes and heat
Carry from tissues:
-Waste matter and CO2
What is the composition of blood?
1-Plasma=55%. Liquid component where cells are suspended. Has gases, salts, proteins, carbs and lipids.
2- Formed elements= 45%. Red cells (99%), platelets and white cells.
3- Serum- does not contain coagulation factors.
What are the different white cells?
White cells are divided into 2 components:
1- Polymorphonuclear granulocytes (65%):
-neutrophils
-basophils
-eosinophil
2- Mononuclear agranulocytes:
-Monocytes
-Lymphocytes
What is haematopoeisis and what are the sites where it occurs?
Production and development of new blood cells.
In the embryo, it’s occurs in the yolk sac, then the spleen, liver and lymph’s nodes. When the bone marrow develop it assumes this task (femur and tibia)
In adults it occurs in the bone marrow (pelvis, cranium, vertebrae and sternum).
*In rare cases the liver, thymus and spleen can resume this role if necessary e.g extreme blood loss
What is a progenitor cell?
It’s a descendant of a multi-potent stem cell that divides to produce our body cells.
What are the steps involved in production of blood cells?
Single stem cells grows and divides in bone marrow. This process is influenced by growth factors: erythropoietin, colony stimulating factors, interleukins and thrombopoietin. The stem cell then looses its cell adhesion molecule (CAM) which allows cells to leave marrow and enter circulation.
NB- once cells differentiate, they loose their capacity for self renewal.
Describe the structure of an erythrocyte.
A mature erythrocyte has a biconcave disc. This shape enhances the diffusion of gases by:
1- ^ surface area
2- Thinness allows O2 to diffuse rapidly
3- ^ flexibility
It’s primary role is to transport O2.
Describe the structure of a platelet/ thrombocyte.
Consists of megakaryocyte which are cell fragments shed from bone marrow. They lack a nuclei, but have organelles and cytosolic enzymes for generating energy & synthesis of secretory products.
How often are blood cells produced?
1- White cell: remain functional for 10 days. Greater turnover means WBCs take up 2/3 of overall blood cell production. removed from circulation by tissue macrophages.
2- Red cell production: Makes up 1/3 of blood cell production. Remains in circulation for approx 120 days. Also removed from circulation by macrophages in liver or spleen (haem and globin recycled).
What roles do blood cells play in homeostasis?
Platelets: sealing leak in blood vessel e.g in injury.
Erythrocytes: carrying O2, H20, heat, nutrients to tissues and CO2 + waste from tissues.
Leukocytes: Defend against invading infections. Recognise self and non self e.g cancer cells. Remove worn out cells and tissue debris.
What is the function of a neutrophil?
Phagocytose: defend against bacterial infections. In circulation for 4-10hrs but once activate can last 1-2 days.
What is the function of a Eosinophil?
Granules have histamine, RNase and DNase. It combats viral and parasitic infections. Overstimulation: allergies and asthma pathogenesis.
*dyed with eosin = brick red stain.
What is the function of a Basophil?
Contains large cytoplasmic granules. Synthesise and store histamine and heparin. Histamine = allergic reaction. Heparin= speeds up removal of fat particles from blood.
What is the function of lymphocytes?
B lymphocytes: produce antibodies. responsible for antibody mediated or humeral immunity.
T lymphocytes: destroy target cells via chemicals e.g antigens.
