Definition Of Blood Cells.docx

Definition of Blood cells and body fluids Blood cells:

ERYTHROCYTES (red cells)



LEUCOCYTES (white cells)



PLATELETS (CELL FRAGMENTS)

Red Blood Cell ‘erythrocyte’ •

Biconcave disc with diameter 7-8µm – Greater surface area for diffusion • Lack of nucleus and other organelles – All internal space is available for oxygen transport • Contain haemoglobin – Oxygen transport • Strong and flexible – Able to squeeze through narrow capillaries Hemoglobin • •

One RBC contains about 280 million hemoglobin Hemoglobin contains – Heme • Iron ion  combine reversibly with one oxygen molecule – Globin • 4 polypeptide chains • 2 alpha and 2 beta White Blood Cells (Leucocytes) • •

All WBCs (leukocytes) have a nucleus and no hemoglobin Granular or agranular classification based on presence of cytoplasmic granules made visible by staining – granulocytes are neutrophils, eosinophils or basophils – agranulocytes are monocyes or lymphocytes

PLATELETS • •

Platelets help stop blood loss from damaged vessels by forming a platelet plug. Their granules also contain chemicals that promote blood clotting. Thrombopoietin stimulates myeloid stem cells to produce platelets

Body fluid •

55% and 60% of total body mass in females and males.

• •

Plasma membrane and blood vessel wall separate ICF, interstitial fluid and blood plasma. Plasma membrane of individual cell separates intracellular fluid from surrounding interstitial fluid. It is selectively permeable. Active transport pumps work continuously to maintain different concentrations of certain ions in ICF and interstitial fluid. Blood vessel wall divide interstitial fluid from blood plasma. Only wall of capillaries are thin and leaky enough to permit exchange of water and solutes between blood plasma and interstitial fluid.

•