Blood cells Flashcards
Define Hematology.
> Hematology is the study of the blood its composition and its function.
Define blood
• Blood is an ‘aqueous body fluid’.
– i.e. It is water containing a whole range of substances.
• It is contained in a complex network called the vascular system and is pumped around the body by the heart.
What are the functions of blood?
- Transportation
- Regulation
- Protection
Transportation as a function of blood
Oxygen from the lungs to the cells of the body and carbon
dioxide from the cells to the lungs.
• Nutrients from the gastrointestinal tract to body cells.
• Hormones form the endocrine glands to other body cells.
• Heat that regulates body temperature
• Waste products away from the cells such as excess water.
Regulation as a function of blood
- Electrolyte balance (that is a substance containing free ions, that behaves as an electrically conductive medium).
- Helps to regulate pH.
Protection as a function of blood
Certain blood cells protect against blood loss (clotting
mechanism).
• Leukocytes provide immunity against infection
Blood composition
Plasma (55%)
• Erythrocytes (RBCs)
• Leukocyte (WBCs)
• Thrombocytes (platelets)
What is plasma composed of?
Water and dissolved solutes: • Ions (mostly Na+) • Nutrients • Metabolic waste products • Hormones • Enzymes • Antibodies • Proteins Cells use plasma amino acids to make their own proteins • Serum is plasma without the clotting factors (fibrinogen) – When blood is left to clot
Plasma proteins
– Albumins
– Globulins
– Fibrinogens
Albumin
-produced by the liver
• most abundant protein in the plasma
• provides osmotic pressure to maintain blood volume
(i.e. draw water from the surrounding tissue fluid into
capillaries)
– Without albumin, the high pressure in the blood vessels would force more fluids out into the tissues. Albumin maintains the proper distribution of fluid between vessels and tissues.
The balance between the two forces differs at different points on the capillaries.
• At the arterial end of a vessel, the
hydrostatic pressure is greater than the
osmotic pressure, so the net movement
favors water and other solutes being
passed into the tissue fluid.
• At the venous end, the osmotic pressure is
greater, so the net movement favors
substances being passed back into the
capillary. This difference is created by the direction of the flow of blood and the
imbalance in solutes created by the net
movement of water favoring the tissue
fluid
Globulins
-α and β:
– produced by the liver
– transport lipids and fat-soluble vitamins
• γ :
– antibodies produced by B-lymphocytes (WBCs) defend against bacteria and viruses
Fibrinogen
- Important clotting factor produced by the liver
- Fibrinogen —> fibrin threads (insoluble)
Red blood cells, what are they?
Are the most abundant cells of the body
• Necessary for the delivery of oxygen to the tissues.
The function of red blood cells
• Transport of haemoglobin
– Haemoglobin carries oxygen from the lungs to the tissues.
• Carbonic anhydrase forms bicarbonate ion (HCO3
- ) from CO2 and waters.
– Carries CO2 in the form of HCO3- from the
tissues to the lungs, where converted to CO2; expelled as waste.
Explain the diagram
CO2 from tissue to red blood cell and oxygen from rbc to tissue.
HbO2 –>O2 + Hb
Hemoglobin
• Heme (iron) + globulin (globular protein)
• RBCs concentrate hemoglobin up to 34g per 100 ml cells
(max).
• Iron bound to heme combines with O2 in the lungs and
release oxygen in the tissues
What are the shape and size of RBCs?
• Average volume is 90-95 cubic um. • Biconcave – Provides increased surface area through which gas can diffuse. – Places the cell membrane closer to oxygen carrying hemoglobin • Shape can change rapidly as cells squeeze through the capillaries.
What is the normal concentration of RBCs in the
blood?
– Men: 5.2 million per cubic mm
– Women: 4.7 million
How are RBCs adapted to their
function?
• Lack nuclei – More space for hemoglobin – Cannot divide (reproduce) • Lack mitochondria – Anaerobic metabolism – Do not use the oxygen they carry • Contain carbonic anhydrase – Catalyses the formation of bicarbonate ions (for CO2 transport)
Where are RBCs produced?
• Early weeks of embryonic life: - Yolk sac
– Are nucleated
• Middle trimester: - Liver
• From the last month of gestation onwards: Bone
marrow
• Up to 5 yrs old:
– All bones produce RBCs
• After 20yrs:
– Production stop in the marrow of the long bones, except the proximal portions of the humeri and tibiae
• Produces in the membranous bones (vertebrae,
sternum, ribs)
– Becomes less productive as age increases
