Haemopoiesis

Question 1

what are produced in the bone marrow

Answer 1

RBC, platelets and WBC

Question 2

where is bone marrow found

Answer 2

throughout the skeleton in infancy but limited to the pelvis, skull, ribs, sternum and vertebrae in adults

Question 3

what are the 2 types of bone marrow test

Answer 3

bone marrow trephine biopsy (taking a 1-2cm core of bone marrow to look at structure) or bone marrow aspiration (taking bone marrow cells to look at finer details)

Question 4

what type of cells do blood cells come from

Answer 4

multipotent hematopoietic cells

Question 5

what are hematopoietic cells differeniate into

Answer 5

myeloid progenitor cells or common lymphoid progenitor cells

Question 6

what controls haematopoiesis

Answer 6

the reduced oxygen is detected by the peritubular kidney cells which then increase their production of erythropoietin which stimulates release and maturation of RBC

Question 7

what cells are involved in the reticuloendotheial system

Answer 7

monocytes, macrophages, kupffer cells, microglial cells

Question 8

what do cells in the RES system do

Answer 8

identify old, abnormal blood cells and phagocytose them mainly in the spleen or liver.

Question 9

how long do erythrocytes live for

Answer 9

120 days

Question 10

what are the functions of erythrocytes

Answer 10

• carry haemoglobin
• maintain the ferrous/reduced state of haemoglobin
• generate ATP
• maintain osmotic pressure

Question 11

describe the structure of RBCs

Answer 11

• have proteins in their membranes making them flexible so can bend through capillaries
• large SA to vol ratio
• biconcave shape

Question 12

which gene codes for the production of haemoglobin and where is it found

Answer 12

globin gene found on chromosomes 11 and 16

Question 13

at what age do you switch from foetal to adult haemoglobin

Answer 13

3-6 months

Question 14

what do the globin chains do

Answer 14

• prevent the haem molecule from oxidation, preventing the ferric form being produced from the ferrous
• allows variation in oxygen affinity by changing shape
• allow solubility

Question 15

describe the break down of haemoglobin

Answer 15

macrophage or kupffer cells break it down into globin (a protein which is then broken down into amino acids) and heme. The irons is taken from the heme to be used. the rest of the molecule is converted to bilirubin in the liver and conjugated to be excreted

Question 16

what does an excess in bilirubin result in

Answer 16

jaundice

Question 17

why do you get anaemia with damaged kidneys

Answer 17

cant produce erythropoietin hormone so there is a decrease in haemoglobin production

Question 18

what are the 2 main metabolic pathways in RBC

Answer 18

• glycolysis

- pentose phosphate pathway

Question 19

what happens if metabolism is altered in RBC

Answer 19

their membrane changes and so they break down quicker so you become anaemic

Question 20

what are the types of available iron

Answer 20

• in haemoglobin
• in myoglobin
• tissue iron e.g. iron used in enzymes
• serum/transported iron

Question 21

what are the types of stored iron

Answer 21

• ferritin

- haemosiderin

Question 22

what happens to iron requirement in pregnancy

Answer 22

increases

Question 23

where does most of the active iron in our body come from

Answer 23

breakdown of RBC (not absorption in the gut from food)

Question 24

what is 95% of iron in the liver stored as and in what cells?
what about the remaining 5%

Answer 24

• ferritin in hepatocytes

- the other 5% is as haemosiderin in kupffer cells

Question 25

how is iron excreted from the body

Answer 25

its not excreted - only small amounts are lost each day by the loss of skin, hair and gut cells

Question 26

how much iron enters and leaves the body in a day

Answer 26

1-2mg

Question 27

what are the differences between haem and non-haem iron

Answer 27

- haem is a better source of iron found in meat which enters enterocytes (cells lining intestines) as Fe 2+ (ferrous) - non-haem is found in pulses and grains and exists as Fe3+ (ferric)

Question 28

what happens to non-haem iron in order to be taken up by enterocytes

Answer 28

stomach acid converts it into ferrous which then binds to transferrin which allows it to be taken up by the enterocytes in the duodenum and upper jejunum. can then be stored in the liver as ferritin or transported in the blood for use

Question 29

what exports iron out of the cells

Answer 29

ferroportin

Question 30

what is lactoferrin

Answer 30

primary iron source in infants

Question 31

how is iron taken into cells such as RBCs

Answer 31

binding of iron transferrin complex to a transferrin receptor

Question 32

what cells contain the highest number of transferrin receptors

Answer 32

RBCs

Question 33

what controls iron absorption

Answer 33

- levels are sensed by villi of enterocytes - can regulate transporters - control transferrin and HFE receptor expression - cytokines

Question 34

outline the role of hepcidin

Answer 34

it is a negative regulator of iron absorption which works by binding to ferroportin and so stops iron leaving enterocytes or macrophages giving a build up of non-functional iron

Question 35

what does an iron deficiency result from

Answer 35

- insufficient intake | - increased use

Question 36

what are the signs and symptoms of an iron deficiency

Answer 36

- tiredness - reduced oxygen carrying capacity - cardiac symptoms - tachycardia - increased respiratory rate - epithelia changes (shiny tongue and spooning of nails)

Question 37

what is hypochromic iron deficiency

Answer 37

low haemoglobin content

Question 38

what is a microcytic iron deficiency

Answer 38

small RBCs as the cells will carry on dividing

Question 39

what is anisopoikilocytosis

Answer 39

change in size and shape of RBC

Question 40

how can you test for an iron deficiency

Answer 40

- ferritin test (but this is an acute phase protein so will increase in infection) - Recticulocyte haemoglobin content - CHR (this is low in thalasaemias)

Question 41

what are the treatments to an iron deficiency

Answer 41

- dietary advice - oral supplements - intramuscular injections - intravenous - transfusion (but only in severe anaemia)

Question 42

why is excess iron dangerous

Answer 42

it can produce highly reactive hydroxyl and lipid radicals which damage lipid membranes, nucleic acids and proteins. the excess iron is deposited in tissues

Question 43

what is haemochromatosis

Answer 43

- iron excess resulting in organ damage due to deposition - can causes liver cirrhosis, diabetes, cardiomyopathy - can be hereditary or transfusion associated

Question 44

what is hereditary haemochromatosis

Answer 44

an autosomal recessive disease due to mutation on the HFE gene HFE normally competes with transferrin for binding to the transferrin receptor so without there is no competition so too much iron enters cells. treated with venesection