PSC1002/L02 Blood Flashcards
What percentage of total body weight is blood?
8%
Give 3 functions of blood.
Gas transport and exchange
Distributing solutes
Immune functions
Maintaining body temperature
Regulates blood clotting
Preserving acid-base homeostasis
Stabilising blood pressure
What is blood composed of? (3)
Erythrocytes
Leukocytes
Thrombocytes
How does blood separate when centrifuged? (3)
55% soluble materials (top)
1% buffy coat - white blood cells and platelets
44% haematocrit (bottom)
What are the 2 main functions of plasma?
Thermoregulation
Transport
How does a high percentage of water in plasma affect properties? (3)
High specific heat capacity
Heat not needed lost to environment
Precentage of water determines blood viscosity/ bp
Describe serum albumins (3)
55% of plasma volume
Large protein synthesised in liver
Maintains osmotic pressure of plasma
Transport of lipids & steroid hormones
Describe globulins (3).
38% of plasma volume
Transport ions, hormones, lipids
Immune proteins made by leukocytes
Describe clotting proteins. (3)
7% plasma volume
Essential for blood clotting
Synthesised in liver
What makes up the final 1% of blood plasma?
Regulatory proteins
Enzymes, proenzymes, hormones
What does a normal electrophoretic pattern of plasma proteins show? (5)
Albumin, a1, a2, B and Y globulins
Give 3 causes of cirrhosis.
Cancer
Alcoholism
Viral hepatitis
What can cirrhosis lead to? (2)
Decrease in production of plasma proteins
Decreased colloidal osmotic pressure
Fluid loss to ECS
Severe edema in abdomen
Decline in clotting factor/easy bruising
What is the volume of erythrocytes?
80-96 femtolitres
Where are small/large RBCs found?
Small - macrocytic in iron deficiency anaemia
Large - microcytic in folate (vitamin B9)
Where does erythropoiesis occur?
Bone marrow
Describe the 7 steps in erythropoiesis.
Hematopoietic cell
Erythrocyte-CFU
Proerythroblast
Early erythroblast
Late erythroblast
Reticulocyte
Erythrocyte
In which step of erythropoiesis does the hormone erythropoietin stop being produced?
3 - proerythroblast
In which step of erythropoiesis is haemoglobin synthesised?
4 - early erythroblast
In which step of erythropoiesis is the nucleus ejected?
5 - late erythroblast
In which step of erythropoiesis are organelles ejected?
6 - reticulocyte
How long after a bleed is homeostasis achieved in the blood?
26 days
How are erythrocytes disposed of at the end of their life?
Phagocytosed in liver and spleen
What are heme components recycled into? (2)
Heme into biliverdin then bilirubin, secreted in bile from liver
Iron stored by protein ferritin in liver
Describe Glucose-6-phosphate dehydrogenase (G6PD).
Predisposes to red blood cell breakdown (haemolytic crisis) when exposed to certain environmental triggers
Describe the 2 parts of a haemoglobin molecule.
Globin - 4 protein chains
4 iron containing haem groups
Describe the structure of the Haem group.
Porphyrin ring containing 1 iron atom
Describe the structure of iron with and without oxygen.
Without: Fe2+ (ferrous)
With: Fe3+ (ferric)
Give the 4 forms of globin protein.
Alpha, beta, gamma, delta
What are the 3 combinations of globin chains in adults?
HbA - 2A, 2B
HbA2 - 2A, 2D
HbF - 2A, 2Y
What are the 2 forms of haemoglobin and where are they found?
r form - high O2 affinity e.g., in lungs
t form - low O2 affinity e.g., in peripheral tissues
Give 3 other molecules that haemoglobin can bind.
Carbon dioxide
Acidic hydrogen portion of carbonic acid
Carbon monoxide
Nitric oxide
What are haemoglobinopathies?
Abnormal haemoglobin chains
What are thalassaemias?
Decreased amount of globin chains or absent globin chains due to gene expression defects
Describe sickle cell anaemia. (3)
Mutation is B-globin gene
Glutamic acid replaced by valine
Creates sticky patches and HbS polymerisation
How can thalassaemias occur? (2)
Gross deletion of one or more globin genes
Gene mutation
Describe the 2 classes of thalassaemia.
a - production of a globin is deficient
b - production of b globin is deficient
What form of haemoglobin is produced in a thalassaemia?
Excess B chains
Unstable tetramers of 4 B chains
HbH
What happens to the oxygen dissociation curve in a thalassaemia?
High O2 affinity, reduced oxygen carrying capacity
Why is B thalassaemia more clinically important than a thalassaemia?
Results in iron overload -> organ damage
What does an excess of a chains lead to in B thalassaemia? (3)
Do not form tetramers
Bind to and damage RBC membranes
At high conc. form toxic aggregates
RBC are fragile and short-lived
