Introduction to Structure and Function of Blood Flashcards
1
Q
What is blood composed of?
A
- Red blood cells (erythrocytes) - makes up 44% of blood
- White blood cells (leucocytes - colourless) - less than 1%
- Platelets (thrombocytes)- less than 1%
- Plasma - 55%
2
Q
Where do mature blood cells originate from?
A
Stem cells within the bone marrow
NB - bone marrow contains many immature blood cells
- Also why some blood-related diseases are derived from conditions affecting the bone marrow
3
Q
Describe the structure of red blood cells.
A
- Biconcave
- No nucleus and does not contain DNA, RNA or mitochondria
- Major constituent is haemoglobin(which make up a third of the cell)
- Contain high amounts of haemoglobin - usually 300 million per cell
4
Q
Describe the structure and function of haemoglobin
A
- Tetramer - made up of 2 alpha globin chains and 2 beta global chains
- Each globin chain has a haem group consisting of a ferrous (Fe 2+) ion to which oxygen binds reversibly through a coordinate bond
- This is how oxygen is carried within the red blood cell
5
Q
What is the difference between granulocytes and agranulocytes? Give examples.
A
White blood cells are classified into these categories.
GRANULOCYTES contain cytoplasmic granules used for killing microorganisms, which agranulocytes lack. Agranulocytes are also mononuclear.
Examples of granulocytes include neutrophils, basophils and eosinophils. Examples of agranulocytes include monocytes and lymphocytes.
6
Q
Describe the structure and function of platelets
A
- Cytoplasmic fragments
- No nucleus
- Membrane bound and contain granules
- Involved in primary haemostasis - the formation of a temporary platelet plug to prevent/stop bleeding by recognising damage to blood vessel walls
7
Q
What do FBC (full blood count) blood tests take into account?
A
- White blood cell count - specifically neutrophil and lymphocyte count
- Haemoglobin concentration - overall Hb concentration in blood
- Mean red cell volume - size of red blood cells
- Mean red cell haemoglobin content - how much Hb in each red blood cell
- Haematocrit
8
Q
What is meant by haematocrit and what can it be used to prove?
A
- Packed cell volume
- Measure of the proportion of red blood cells within blood
- LOW indicates anaemia/high number of white blood cells due to infection
- HIGH indicates dehydration/polycythemia vera
9
Q
What does pulse oximetry measure and how does it do so?
A
- Measures oxygen saturation of blood by analysing the colour of haemoglobin
- LOW OXYGEN SATURATION indicates HYPOXIA
10
Q
Describe the role of the blood in homeostasis
A
- Plasma proteins are involved in regulation of acid-base balance through buffering action - pH at around 7.4
- Plasma proteins such as albumin are involved in the regulation of osmotic pressure (at around 25 mmHg)
- Vasoconstriction and vasodilation are major parts of thermoregulation by keeping a balance between heat gain and loss
- Controlling distribution of water and solutes
- Ensuring plasma pH, ion concentrations etc. are kept within safe levels
- Homeostasis disturbed by kidney, liver and cardiovascular disorders
10
Q
What is plasma and what is it composed of?
A
- The fluid component of the blood
- 92% is made up of water( the solvent in which the components are suspended, and where proteins and solutes are dissolved) and between 6-8% is made up of plasma proteins (involved in buffering and have specific transport properties). 90% of these proteins are albumin - thousands of others in smaller proportions
- Also made up of hormones (e.g cortisol and thyroxine) and waste products (e.g urea) - transport them to target organs for secretion/excretion etc.
- Also made up of nutrients such as glucose, amino acids and vitamins - which can act as energy sources as well as precursors for synthesis of other molecules
- Contains electrolytes such as ions - which help establish and maintain membrane potentials, maintain pH balance and regulate osmotic potentials. Examples of cations are H+, Na+ and Mg 2+. Examples of anions are Cl- and HCO3- ions
- Contain oxygen which is needed by cells for aerobic respiration, as well as CO2 which is a waste product of the aforementioned reaction
11
Q
What is serum and why is it important in some blood tests?
A
- Serum is the fluid left after blood clotting factors removed
- It is important since some blood tests such as LFT and U&E tests work better with serum than they do with plasma. Some others directly require unclotted blood.
- In these cases anticoagulants (e.g heparin, EDTA) may be added to blood samples to prevent clotting
12
Q
Outline the role of plasma in transport
A
- Facilitates the transport of respiratory gases e.g CO2 may be transported in a dissolved form or as HCO3 - ions from the tissues to the lungs for excretion
- Removal of nitrogenous waste products e.g urea, ammonia, creatinine from cellular metabolism by transport to lungs or kidneys for excretion
- Plasma proteins can be used to facilitate transport of substances which are poorly soluble in water/ nutrients such as glucose, amino acids and vitamins absorbed from the digestive tract
13
Q
Outline the role of plasma proteins in transport with examples
A
- Transferrin transports iron. Cells have receptors that bind to transferring for iron uptake.
- Globulin acts as a specialised carrier for metal ions and is involved in the transport of hormones to their target organs e.g TBG is involved in thyroxine transport. Alpha globulins facilitate transport of lipids and some metal ions. Beta globulins facilitate transport of iron ions and lipids. Gamma globulins have immune functions - one prominent subgroup are immunoglobulins
- Albumin is a general purpose carrier for fatty acids, hormones and drugs/ also behaves as an osmotic regulator
- Transport of ions is essential as these ions are toxic and can be used by bacteria for growth
14
Q
Outline the role of the plasma in immunity
A
- Involved in haemostasis - plasma proteins such as fibrinogen and other associated procoagulants such as prothrombin and Factor X are found within the plasma. Fibrinogen converted to fibrin to strengthen primary platelet plug. Process controlled by other clotting factors.
- Plasma contains immunoglobulins and complement proteins
- Immunoglobulins are synthesised by B-lymphocytes - act as antibodies
- Carry complement proteins - cooperate with white cells and immunoglobulins to kill bacteria and pathogens
