introduction to blood L2

Question 1

what percentage of body weight is made up of blood

Answer 1

8%

Question 2

what is the volume distribution of blood

Answer 2

0.6L- lungs
2L- systemic venous circulation
1.4 L- the heart, systemic arteries, arterioles and capillaries

Question 3

describe 3 functions of blood

Answer 3

1. gas transport and exchange
2. distributing solutes
   - plasma transports: ions (thus helps regulate ion concentrations in tissues) nutrients , hormones, metabolic waste
3. immune functions: leukocytes (WBC) and immune system proteins are transported in blood

Question 4

describe 4 more functions of blood

Answer 4

1. maintains body temp
   - blood carries away heat - a byproduct of many chemical reactions in body
2. regulates blood clotting
   - platelets and certain proteins form blood clot; seals damaged blood vessels to prevent blood loss
3. Preserving acid-base homeostasis
   - pH of blood wants to be in range of 7.35-7.45
   - blood contains several buffer systems to maintain pH
4. stabilising blood pressure
   - blood volume is a major factor in determining blood pressure

Question 5

what are the 4 main components of blood

Answer 5

1. plasma (complex liquid in which cells are suspended)
2. Erythrocytes- Red Blood Cells
3. Leukocytes- White Blood Cells
4. Thrombocytes- Platelets
   - fewer white blood cells than red

Question 6

how do Blood Constituents settle in tube

Answer 6

bottom (most heavy): red blood cells
middle: buffy coat layer- white blood cells and platelets
top: plasma

Question 7

what is the percentage of RBC layer

Answer 7

44%

Question 8

what is the percentage of buffy coat

Answer 8

1%

Question 9

what is the percentage of plasma

Answer 9

55%
- composed of mainly water and soluble factors

Question 10

what is serum

Answer 10

plasma without clotting factors

Question 11

define Haematocrit and give its normal percentage for men and women

Answer 11

the ratio of the volume of red blood cells to the total volume of blood.
M: 45%
W: 42%

Question 12

what is blood made up of

Answer 12

plasma
cellular elements
- RBC, WBC, platelets

Question 13

what is plasma made up of

Answer 13

water, ions, organic molecules, trace elements and vitamins, gases

Question 14

what organic molecules make up plasma

Answer 14

amino acids, proteins, glucose, lipids, waste

Question 15

what important proteins make up plasma

Answer 15

albumins, globulins, fibrinogens (important clotting factor)

Question 16

what are the two main functions of plasma

Answer 16

1. thermoregulation
2. transport

Question 17

what are the three main components of plasma

Answer 17

1. water >90%
2. plasma proteins 8%
3. dissolved small molecules 1-2%

Question 18

describe role of water in plasma

Answer 18

High capacity to hold heat; blood temperature only undergoes small changes.
- Heat not needed is lost to the environment.
Percentage of water determines blood viscosity:
- less water -> thicker blood -> sluggish flow

Question 19

describe role of the 3 main plasma proteins in plasma

Answer 19

Serum albumin (~55%):
- maintains osmotic pressure of plasma
- assists in transport of lipids and steroid hormones
- large protein, synthesised in the liver
Globulins (~38%):
- bind to and transport ions, hormones and lipids otherwise incompatible with water-based plasma
- immune proteins: Antibodies or gammaglobulins, made by leukocytes
Clotting proteins (fibrinogen) (~7%):
- essential for blood clotting
- synthesised in liver
Remainder (~1%):
- Regulatory proteins such as enzymes, proenzymes, and hormones.

Question 20

how can plasma proteins be identified

Answer 20

electrophoresis
- used in diagnostics of myeloma
- those with myeloma have band indicating monoclonal component (uncontrolled growth) which is not on normal band patterning

Question 21

describe role of dissolved small molecules in plasma

Answer 21

Nutrients: Glucose, amino acids, lipids, vitamins
Waste Products : Creatinine, bilirubin, urea
Dissolved gases: Oxygen, Carbon Dioxide
Hormones, vitamins and minerals
- Transported in solution and Readily exchanged between blood and interstitial fluid

Question 22

what is the structure and function of erythrocytes

Answer 22

bioconcaved disk that contains haemoglobin and functional enzymes
transports oxygen to respiring cells and removes carbon dioxide

Question 23

what is the volume of erythrocytes

Answer 23

80-96 femtolitres (10 to the power of -15)

Question 24

what is MCV

Answer 24

Mean Cell Volume
- measures the average size of your red blood cells

Question 25

what does it mean if your RBC are microcytic or macrocytic

Answer 25

MICRO: they are small caused by iron deficiency and will often be seen as pale - anaemia MACRO: RBC are large - folate (vitamin B9) deficiency anaemia

Question 26

describe synthesis of RBC

Answer 26

1. starts in bone marrow - multipotent hematopoietic stem cell (hemocytoblast) may become any type of formed element 2. hemocytoblast goes down myeloid pathway to go on to form erythrocyte - hemocytoblast becomes erythrocyte-CFU and cell is committed to becoming erythrocyte - forms proerythroblast (requires erythropoietin to happen) - early erythroblast made which starts to synthesise haemoglobin - late erythroblast ejects organelles - reticulocyte formed and enters blood continues maturing in vessel forming erythrocyte

Question 27

synthesis of RBC is a feedback loop, describe it

Answer 27

low RBC cause hypoxia reduce O2 causes kidney to release erythropoietin which stimulates red bone marrow to start synthesising RBC leads to increase O2 levels so synthesis slows down

Question 28

describe what happens to damaged RBC

Answer 28

RBC become damaged from squeezing through capillaries in the liver or spleen, haemoglobin in ruptured RBC is decomposed to haem and globin haem is recycled to form bile or iron ions globin, membrane and other proteins are broken down into amino acids and used to make new RBC

Question 29

what is the function of haemoglobin

Answer 29

transport O2 as it is poorly soluble in water - 98% of O2 bound to haemoglobin

Question 30

describe the structure of haemoglobin

Answer 30

The globin part –made up of four protein chains Four iron containing haem groups – each iron atom can reversibly bind one molecule of oxygen

Question 31

describe the structure of the haem group

Answer 31

Haem is an iron containing pigment Consists of a porphyrin ring containing one atom of iron Due to its iron content it appears reddish when combined with oxygen and bluish when deoxygenated Iron: Fe2+ (ferrous) in absence of O2, Fe3+ (ferric) when O2 bound

Question 32

describe structure of globins

Answer 32

there are 4 kinds- alpha, beta, gamma, delta 97% of adults have 2 beta and 2 alpha (HbA) 2.5% of adults have two alphas and two deltas (HbA2) foetal haemoglobin is two alphas and two gammas (HbF) alpha coded for by 2 genes on chromosome 16 beta coded for by 1 gene on chromosome 11

Question 33

what is oxygen binding to haemoglobin determined by

Answer 33

partial pressure of oxygen (pO2). number of free oxygen binding sites available in the molecule O2 binding is cooperative – binding of one oxygen molecule encourages O2 binding by the other three haem molecules

Question 34

what are the two forms of haemoglobin

Answer 34

taut (t) and relaxed (r) - r form: high O2 affinity, exists at high pO2 – firmly binds oxygen (e.g. in the lungs) - t form: low O2 affinity, exists at low pO2 - releases oxygen (in peripheral tissues)

Question 35

other than oxygen, what else can haemoglobin bind to

Answer 35

1. carbon dioxide 2. The acidic hydrogen ion portion (H+) of carbonic acid –generated in tissues from carbon dioxide, Hb buffers the acid 3. Carbon monoxide (CO) –not normally in blood but if inhaled preferentially binds to Hb (carboxyhaemoglobin) causing carbon monoxide poisoning. 4. Nitric oxide – an important regulatory molecule

Question 36

what are two types of HB production abnormalities

Answer 36

Haemoglobinopathies: - Abnormal globin chains are made: - sickle cell anaemia The Thalassaemias: - Normal globin chains are made but in decreased amounts OR are absent because of defects at the level of gene expression.

Question 37

describe sickle cell anaemia

Answer 37

Genetic disease: Mutation in the -globin gene -> a glutamic acid residue is replaced by valine in the protein (βS). Creates ‘sticky patches’ on the molecule. Resultant haemoglobin (HbS) polymerises at low pO2 forming long crystals of HbS. RBCs deform and become sickle-shaped.

Question 38

what can sickle cell anaemia result in

Answer 38

Sickled RBCs become trapped within and block small blood vessels depriving downstream tissues of oxygen and causing ischemia and infarction Damaged cells go to spleen and can block it so normal removal systems do not work Can get trapped in lungs or joints- inflammation

Question 39

describe Thalassemias

Answer 39

Diseases where synthesis of one or both of the alpha or beta globins is reduced Disease severity varies from minor, intermediate to major RBC prone to damage and short lived -> anaemia Recessive genetic disease, either: Gross deletion of one or more globin genes Gene mutation

Question 40

what are the two classes of Thalassemias

Answer 40

α and β α – production of α globin is deficient found predominantly in India and surrounding regions β – production of β globin is defective predominantly in Mediterranean region Haemoglobin fails to form correctly -> RBC attempt to make Hb with the globin chains that are available

Question 41

describe α Thalassaemia

Answer 41

Production of α globins is reduced Leads to excess β chains; unstable tetramers of four β chains (called Haemoglobin H (HbH)) form. Leads to abnormal oxygen dissociation curves (high O2 affinity, reduced oxygen carrying capacity) and RBC damage. Short lived RBC -> anaemia

Question 42

describe β Thalassaemia

Answer 42

Relative excess of α chains do not form tetramers bind to and damage RBC membranes at high concentrations form toxic aggregates. RBC are fragile and short lived-> anaemia

Question 43

which form of Thalassaemia is clinically most important

Answer 43

β Thalassaemia Results in iron overload –> organ damage (heart, liver, endocrine system). Treatment: iron chelation therapy otherwise patients accumulate potentially fatal iron levels.

Question 44

how can Thalassaemia be diagnosed

Answer 44

electrophoresis α Thalassaemia: Reduced HbA, presence of HbH β Thalassaemia: Production of β globins is reduced or absent; decreased HbA on electrophoresis

Question 45

types of haemoglobin

Answer 45

Remember: HbA = two alpha and two beta globins. HbA2 = two alpha and two delta globins HbF = two alpha and two gamma globins HbH = four beta chains. HbS = sickle cell