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What are the roles of blood?

- It acts as a connective tissue
- It transports many substances to the cells by connecting every part of the body
- It aids heat distribution throughout the body
- It has a function in immunity
- Haemostasis – thrombogenesis and thrombolysis
- Support – i.e. with the penis
- Maintains homeostasis


What are the major components of blood?

- Erythocytes
- Leukocytes
- platelets
- plasma


What is cooperative binding?

Initially Hb has a low affinity for oxygen due to the conformational shape of the globin moelcules. But when one oxygen binds, the conformation is broken and the structure opens up allowing the second oxygen to bind more easily.


What is normal Hb concentration for a male and female?

female - 11.5-14.5 g/dL
male - 13.5 - 16.5 g/dL


What is normal RBC for male and female?

female - 4.8*10^12/L
male- 5.4*10^12/L


What is normal haematocrit for males and females?

female - 0.35-0.47
male - 0.40-0.54


How are litres converted into deciltres?

1L = 10 dL


What is anaemia?

Low blood haemoglobin concentration


What are the three types of anaemia?



Microcytic anaemia

Small MCV
Caused by failure of Hb synthesis, iron deficiency
Caused by menstruation, GO tract lesions and parasitic infections


Normocytic anaemia

Normal MCV
Acute blood loss e.g. in an accident


Macrocytic anaemia

Large MCV
Failure of DNA synthesis and cell division resulting in reduced division of progenitor cells and so there are fewer but larger compensatory erythrocytes
- Caused by folic acid deficiency (needed for thymidine synthesis, happens in pregnancy)
- Vit B12 deficiency (needed for folic acid actions)- autoimmune conditions can cause this by destroying uptake in gut/ can also be caused by being vegan


Sickle cell disease

Caused by a mutation in the gene that codes for haemoglobin leading to distorted erythrocytes
Having one copy = malaria resistance



Excess eryhtrocytes
Physiological response to high altitudes
Pathological when blood viscocity is high causing heart problems



- The low oxygen level is detected by the kidney
- The kidney secretes a hormone called erythropoietin
- Erythropoietin stimulates bone marrow stem cells (haematopoietic stem cells) to differentiate into erythrocytes – this is erythropoiesis
- The levels of erythrocytes in the blood increases. This consequently increases the level of haemoglobin
- This therefore increases the oxygen carrying capability of the blood, so blood oxygen levels increase
- This is detected by the kidney and the levels of erythropoietin secreted by the kidney decreases (negative feedback)


Erythrocytes life cycle

- Red blood cells are produced in bone marrow from precursors (haematopoietic stem cells) which produce haemoglobin then lose organelles
- Immature erythrocytes contain ribosomes. These are called reticulocytes
- High circulating levels of reticulocytes is a diagnostic tool for conditions caused by anaemia, chemotherapy etc.
- The reticulocytes are removed through the reticulo-endothelial system, by phagocytic macrophages in the spleen
- Their lifespan is about 120 days
- The life cycle is dependent on dietary iron



There is an oxidised form of haemoglobin, that contains ferric iron (Fe3+) – this is called methaemoglobin. This cannot carry oxygen – however, this only happens after exposure to poisons such as benzene etc.


What is the main product of the breakdown of Hb?



What are leukocytes?

- These are white blood cells and use the circulation for transport
- They travel near the capillary wall and invade tissue space to fight infections
- They are classified by structure and dye binding
- There are many types of leukocyte


What are polymorphonuclear granulocytes and give examples?

They have multilobed nuclei with many granules
- nuetrophils (phagocytic)
- eosinophils (allergy)
- basophils (histamine)


When do monocytes appear to the site of infection?

After granulocytes


What do monocytes do?

They become macrophages and engulf, they also secret inflammatory mediators and stimulate angiogenesis
They present antigens to lymphocytes


What is a normal leukocyte count and what do high/low levels suggest?

3.5-7.5*10^9 /L
(neutrophil highest, then lymphocytes, monocytes, eosinophils, basophils)

Leukocytosis (high) - infection and cancer
Lekopenia (low) - HIV, chemotherapy


What is the size of a platelet and normal count?
What do they contain?
Life span
What is their role?

2-3 micrometers
25*10^4 /ml
- derived from megakaryocytes
- Life Span = 8-10 days
- Many granules and organelles but no nucleus
- They are involved in clot or thrombus formation



This is the fluid component of the blood and act as the carrier of the solids in the blood
- Contains nutrients (glucose, lipids, amino acid)
- Hormones (hyroxine, cortisol)
- Inorganic ions (Na+, K+, Ca2+, PO43-, HCO3)
- Products of metabolism (urea, lactic acid)
- There are plasma proteins like albumins, globulins, fibrinogen (precursor to fibrin, which is involved in clotting and platelet aggregation)


What is serum?

Plasma with the proteins removed (due to clotting)


How are platelets activated?

- Have surface receptors which attach to platelet activators such as collagen and thrombin.
- Adhesion to exposed collagen or atherosclerosis
- Release granules - promotes platelet aggregation
- Produce THROMBOXANE A2 using cyclooxygenase enzyme (aspirin inhibits this)

Shape changes when activated - produce extensions called filapodia


What else inhibits platelet activation?

The vascular endothelium produces prostacyclin and nitric oxide which inhibit platelet activation