Red Blood Cells Flashcards
What is the scientific name for rbcs?
Erythrocytes
What part of rbcs bind to O2 and CO2?
Haemoglobin
What affect does the presence of haemoglobin have on rbcs?
Gives them a red colour
What makes up most of rbcs?
Haemoglobin
What is a H’crit?
The fraction of the blood that is blood cells
What is a small blood cell called?
Microcyte
What may cause microcytes?
Anemia
What is a big rbc called?
Macrocyte
What may cause macrocytes?
The incorrect folding of proteins in an rbc
What is a pale rbc called?
Hypochromic rbc
What may cause an rbc to be hypochromic?
Less haemoglobin
What is a stack of rbcs called?
A rouleaux of rbcs
What is so special about the rouleaux of rbcs?
This organisation allows rbcs to get through small capillaries quickly
What are sickle shaped rbcs?
Incorrectly shaped rbcs
Why are sickle cells dangerous?
3
They cannot form the rouleaux structure
They cannot get through capillaries
Can cause pain in areas such as the lungs
What is a red blood cell count?
The number of RBCs per ml of blood
What is the expected rbc count in males?
4.5-6.3 million per mm cubed
What is the expected rbc count in females?
4.2 - 5.5 million per mm cubed
Why is there a difference in rbc count in females and males?
This is accounted for by the hormone testosterone which boosts RBC number
What is the total RBC number in the body?
Approximately 25 trillion
What is the total cell number in the body?
75 trillion
How are rbcs shaped?
3
Biconcave discs
Thin centre
Thick rim
Give the measurements of an rbc.
2
7.8 um in diameter
between 2.6 um and 0.8 um in thickness
Why are rbcs biconcave in shape?
To give the rbc a larger surface area to volume ratio
How long does it take to make blood cells?
about a week
What do rbcs begin as on day 1?
Proerythroblasts
What are rbcs called on day 2 of their formation?
Basophilic erythroblasts
What are rbcs called on day 3 of their formation?
Polychromatophilic erythroblasts
What are rbcs called on day 4 of their formation?
Normoblasts
What happens after day 4 in the production of rbcs?
The normoblasts eject their nucleus
What are rbcs called on day 5-7 of their production?
Reticulocytes
What happens to a reticulocyte when it enters circulation?
It becomes a mature red blood cell
What stem cell gives rise to all blood cells except lymphocytes?
Myeloid stem cell
Why might rbcs not be considered cells?
4
They cannot divide
They cannot make proteins
They cannot make enzymes
They cannot repair
What is the life span of rbcs?
120 days
What type of metabolism do rbcs have and why?
Anaerobic metabolism because they have no mitochondria
What organelles do rbcs loose during their formation?
They loose all organelles not associated with gas transport
Describe the structure of haemoglobin.
5
Has 2 alpha and 2 beta chains of polypeptides
Each chain is a globular protein subunit e.g. myoglobin
Each chain has a single Heme molecule
Each chain is a polypeptide chain attached to a heme prosthetic group
This attached group binds iron
What is HBO2?
Oxyhaemoglobin
What is oxyhaemoglobin?
Oxygen bound to haemoglobin
What is different about foetal hamoglobin?
It binds O2 more readily and therefore steals O2 from the mother’s blood
How many O2 binding sites does haemoglobin have?
4
What happens if O2 in plasma is low?
O2 is released from Haemoglobin
What is hypoxemia?
Low oxygen in blood
What organs sense hypoxemia?
Liver
Kidney
What is low oxygen a stimulant for?
The production of more rbcs
What is anaemia?
2
A condition where there is either a low Hb content or low H’crit
Results in body cells are deprived of O2
Give three symptoms of anaemia.
Fatigue
Weakness
Disorientation
What does anaemia do to blood?
2
Blood becomes less viscous
Blood pressure drops
What is the main cause of anaemia?
Low haemoglobin levels
What may cause low haemoglobin levels?
4
Abnormal alpha chains (a thalassemia)
Abnormal beta chains (sickle cell anaemia)
Low iron
Low dietary protein
What is anaemia caused by low iron levels caused?
Iron deficiency anaemia
Other than low haemoglobin levels, what is often a cause of anaemia?
Low H’crit
What may cause low H’crit?
Severe haemorrhage
Low RBC production
Renal failure
Low dietary B12
Break down of rbcs in the blood stream
What is anaemia caused by haemorrhage called?
Haemorrhagic anaemia
What is anaemia caused by low RBC production called?
Aplastic anaemia
What is anaemia caused by low dietary B12 called?
Pernicious anaemia
What is pernicious anaemia?
Anaemia caused by low dietary B12 which leads to poor maturation of RBCs
What is anaemia caused by the break down of rbcs in the blood stream?
Haemolytic anaemia
Why do rbcs only live for 120 days?
4
They cannot repair themselves and they get damaged in the circulatory system
They circulate the body every minute
Their size is large compared with capillary size
They are pumped under pressure
What happens when a rbc is damaged?
2
They are removed and by the liver and spleen
They are then replaced
Why does a bruise change colour?
The colour change is due to the heme being broken down
How are rbcs broken down?
5
Some may fragment and go straight to the kidney - blood in urine
Rbcs parts are reused
Heme broken down into biliverdin (green) and then bilirubin (bile)
Bilirubin is broken down in large intestine into derived products
Derived products move to kidneys - yellow colour in urine
How are the parts of old/damaged rbcs reused?
2
Amino acids are brought back to bone marrow to be reused
Iron is wrapped in a plasma protein so it can be reused in the marrow
Where are rbcs broken down into their reusable parts?
Liver - hence why the liver is such a good source of iron
What breaks down haemoglobin?
Phagocytic cells
What happens when haemoglobin is broken down?
The heme group and globular protein are recycled
How is the globular protein of Hb recycled?
Its broken down into amino acids
How is the heme group of Hb recycled?
2
Its broken down to release the iron for reuse
The rest is excreted in the bile or urine
What is a heme group without iron called?
Biliverdin
What colour is biliverdin?
Green
What happens to biliverdin?
It’s converted into bilirubin
What colour is bilirubin?
Orange-yellow
How is bilirubin excreted?
2
Excreted in bile
Bacteria then further break it down in the large intestine
How is bilirubin broken down by bacteria?
Urobilinogens and stercobilinogins are formed
What happens to urobilinogens?
They may be reabsorbed into the blood and excreted as urobilins into the urine (yellow colour)
What gives urine it’s yellow colour?
Urobilins
What happens to stercobilogins?
They are further converted into urobilins and stercobilins and excreted in faecal matter (yellow/brown colour)
What gives faecal matter it’s yellow/brown colour?
Urobilins
Stercobilins
What is jaundice?
2
Excess heme breakdown where some byproducts are deposited under the skin (jaundice)
Bilirubin is released into the blood where it diffuses into the peripheral tissue
What are the four main causes of jaundice?
Obstruction of the bile duct
Infections (bacterial or viral) of the liver
Cirrhosis of the liver (chemical damage)
Haemolysis in the blood stream
What causes neonatal jaundice?
3
Its a form of haemolytic jaundice
The liver of the neonate is immature and cannot handle bilirubin for the first week or so
The fetal Hb is being replaced by mature Hb
Why is excess iron dangerous?
Iron is toxic in the free state and is not excreted if in excess
Where is iron stored?
Liver or spleen
What does iron bind to in the blood?
The transferrin transport (plasma) proteins
What is excess iron bound to?
Ferritin or hemosiderin (for storage in liver or spleen)
What may cause iron deficiency?
2
Dietary insufficiency
Malabsorption
What may cause iron overload?
Genetic causes
What does iron overload cause?
Leads to secondary storage sites in other organs - leads to disease of other tissue such as heart or liver
What are the consequences of anaemia?
3
Oxygen deprivation - shortness of breath
Reduced blood viscosity - heart beats faster - turbulent flow - cardiac failure
Increased blood flow needed - increased heart rate
