Blood Flashcards
What are the cells in blood known as?
Formed elements
What is the blood composed of?
Cells / formed elements and plasma
What cells / formed elements are found in blood?
erythrocytes, leucocytes, thrombocytes (platelets)
What does plasma consist of?
extracellular fluid, water, electrolytes (e.g. sodium), organic molecules (glucose, fatty acids, glycerides, amino acids…), plasma proteins.
What are the plasma proteins?
albumins (60%), globulins (35%), fibrinogen (4%), regulatory proteins (1%)
What are the most abundant plasma proteins?
Albumins (60%)
Function of albumin
Maintains oncotic pressure - helps retain water in the bloodstream and prevents fluid leaking excessively into tissues. Also responsible for transport of lipids.
Name of swelling caused by excess fluid leaking into tissues
oedema
Function of globulins
Responsible for transport of ions, hormones, lipids and immune function.
Function of fibrinogen
key component of blood clotting
What constitutes regulatory proteins?
Enzymes, hormones
How does blood volume differ between individuals?
Blood volume depends on size with males typically having a greater blood volume (70ml/kg) than females (60ml/kg).
What percentage of the blood volume is made from plasma?
55% (46-63%)
What percentage of blood volume is made of cells/formed elements?
45% (37-54%)
What is the most abundant blood cell?
Over 99% of blood cells are erythrocytes, followed by leucocytes and thrombocytes)
What is the morphology of erythrocytes? (diameter, shape)
6-8um diameter and has a biconcave disk shape
Advantages of biconcave disk shape of erythrocytes
Provides a large SA:vol ratio which allows rapid diffusion of CO2 and O2 across plasma membrane. Can bend in narrow capillaries and expand in hypotonic solutions.
Behaviour of older erythrocytes in hypotonic solutions
older erythrocytes are more fragile and therefore more likely to haemolyse
Appearance of erythrocytes in blood film
Halo effect - outer thicker portion of RBC stains more intensely than thinner, concave centre which appears pale.
Term for red blood cell formation
erythropoiesis
Where are red blood cells formed?
red bone marrow
Average lifespan of erythrocytes
120 days
How are old erythrocytes broken down?
MPS system (mononuclear phagocyte system) which is part of the immune system, removes and breaks down RBCs in the spleen.
Where does the MPS system mostly remove and breakdown old red blood cells?
in the spleen mainly (also in liver and bone marrow)
What happens to the breakdown products of red blood cells?
haemoglobin is broken down into protein (globin) and haem group which are recycled. The protein is broken down into amino acids which enter the pool to make new proteins. Haem is broken down into iron (used in production of new RBCs) and biliverdin (converted into bilirubin).
What is conjugated bilirubin?
The form of bilirubin (bilirubin glucuronide) excreted as bile pigment.
How is conjugated bilirubin / bile pigment formed?
Produced in the liver when bilirubin combines with glucuronic acid to produce bilirubin glucuronide.
What happens to 10% of newly produced erythrocytes?
They are non functional and haemolyse. They are then either engulfed my macrophages in MPS or the haemoglobin is filtered out of the circulation by the kidneys into urine.
What happens to the Fe2+ that is one of the breakdown products of haem (along with biliverdin)?
Fe2+ is transported in the circulation by transferrin back to the red bone marrow for erythropoiesis. (recycled)
What elements are recycled in erythrocyte breakdown?
Amino acids and Fe2+
What happens to bilirubin as it enters the large intestine from the small intestine?
It is broken down into bilirubin-derived products some of which are absorbed into the circulation and filtered out by the kidneys. Most bilirubin-derived products (e.g. urobilins and stercobilins) continue in the large intestine and are eliminated in faeces.
Example of bilirubin-derived products
urobilins and stercobilins
What causes the brown colour of faeces?
Bilirubin-derived products e.g. urobilins and stercobilins
Stages of erythropoiesis
day 1 - proerythroblast
day 2 - basophilic erythroblast (dark staining)
day 3 - polychromatophilic erythroblast (pink)
day 4 - normoblast
Nucleus ejected (no longer an erythroblast)
days 5-7 - reticulocyte
enters circulation as a mature erythrocyte
Summary of erythropoeisis
cell size is reduced and nucleus is ejected
Which substances are required for the reduction in cell size and nucleus regression during erythropoiesis?
Folic acid and vitamin B12
What substance is required to increase haemoglobin content of the reticulocyte (after nucleus is ejected)?
iron
Which hormone regulates erythropoiesis?
Erythropoietin (based in kidneys)
Term to describe low blood oxygen
hypoxia
How does the body counteract low blood oxygen (hypoxia)?
Usually due to decreased RBC numbers. This means less oxygen is delivered to cells. The kidney detects low blood oxygen and releases erythropoietin which travels to the red bone marrow and stimulates increased erythropoiesis. More erythrocytes in the blood increases the blood oxygen.