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Human physiology > Blood 2 > Flashcards

Blood 2 Flashcards

1
Q

How many RBCs are ther per ml in the blood?

A

5 billion

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2
Q

What are the physical properties of an RBC?

A
  • Biconcave shape
  • Diameter = 8um
  • Thickness = 2um
  • Flexibile membrane
  • No nucleus or organelles
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3
Q

What are the benefits of the biconcave shape of the RBC?

A
  • Large SA (larger than sphere of same vol)
  • Favours diffusion (thickness of cell allows O2 to diffuse in & out)
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4
Q

How is the flexibility of the membrane of an RBC beneficial?

A

Allows them to squeeze through narrow capilaries - many are narrower the the diameter of the RBC

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5
Q

What % of the blood vessels in the body are capillaries and how much of the blood vol do they hold?

A
  • 99% of blood vessels in the body are capillaries
  • Hold only 5% of blood volume
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6
Q

How does the flexibility of the membrane help with osmosis

A

Means the RBCs can cope with different levels of osmolarity as the membrane is robust

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7
Q

How many molecules of Hb can an erythrocyte carry - therefore hoe many molecules of O2 can it carry?

A

Hb –> 250,000,000

O2 –> 1,000,000,000 molecules

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8
Q

How many molecules of O2 can one Hb carry?

A

4 each

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9
Q

Why are RBCs well adapted to carry so much O2?

A

They have no nucleus or organelles which frees up more room to pack in more O2

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10
Q

What does it mean for RBCs because they have no nucleus?

A

No DNA or RNA =

  • No cell repair
  • No cell growth
  • No division
  • No energy generation
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11
Q

How long can RBCs survive?

A

Only 120 days (travel 700 miles)

Due to the lack of nucleus - cannot survive any longer alone

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12
Q

How do RBCs survive without any nuclues?

A

They survive on the supplies they synthesised before the nucleus & organelles were extruded

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13
Q

What happens to RBCs when they reach the end of their lifespan? (120 days)

A

They become fragile - will eventually rupture in the narrow capillaries which they’re forced through

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14
Q

Where are RBCs most likely to rupture and why?

A

In the spleen - this is where the capillaries are narrowest

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15
Q

Why is it beneficial that RBCs rupture mainly in the spleen?

A

Rather than the debris ending up in the capillaries and floating around, instead:

The spleen takes up the debris –> can store RBCs which can be released if you need more O2 carrying capacity or lose blood

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16
Q

How many RBCs are the at a time in the average adult?

A

25-30 trillion

5 million per microlitre, 5.5.L of blood total = 25-30tr

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17
Q

How many RBCs need to by synthesised per second, whats the maths behind this?

A

3,000,000 need to be synthesised every second

Bc:
30,000,000,000,000 RBCs, each lives 120 days –> 250,000,000,000 RBCs are destroyed every day = 3,000,000 per second

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18
Q

What is haematopoiesis?

A

The process by which cellular components of the blood are formed

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19
Q

What is eythropoeisis?

A

The production of RBCs

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20
Q

What is the first site of eythropoeisis?

A

The yolk sac - a group of cells that exist outside of the embryo which then moves into the embryo

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21
Q

What is the second site of eythropoeisis?

A

After the yolk sac moves into the embryo the liver and spleen take over

22
Q

Where is the final site of eythropoeisis?

A

The bone marrow

It takes over from the spleen and liver as they have other roles in the embryo

23
Q

How does child and adult bone marrow differ?

A

Child bone marrow = bones filled with red marrow

As you get older the red marrow turns to yellow bone marrow cells

24
Q

Why do adult & child bone marrow differ?

A

As you’re growing as a child you need to produce lots of RBCs due to your volume constantly increasing - once you’re fully grown you don’t need to increase the volume anymore, only replace the lost cells

25
Q

What is the amount of bone marrow in the body equivalent to?

A

Same weight & size as the liver

26
Q

What is the tissue of the bone marrow like in general?

A

It is a very vascular tissue & has lots of blood supply going in

Filled w lots of blood sinuses –> wider regions are lined w an epithelium

27
Q

How to RBCs enter the blood stream?

Explain from the stem cell to once it reaches the blood stream

A

Begin as a stem cell - it divides to produce RBCs, as it divides it loses the nucleus

The RBCs enter the bloodstream by squeezing through the endothelial cells]

Various cell types comr from this same area

28
Q

How are RBCs produced differently in an emergency situation?

e.g. blood loss and lots needs to be produced at once

A

The bone marrow must produce RBCs quickly, however the process takes time to make them

You would therefore be better off having cells in the blood without the nuclei removed, rather than proper innucleated cells

When these cells are present this is a sign of injury

29
Q

How can you regulate how many RBCs you have at a time?

A

Need to measure the carrying capacity of the blood and need to make sure you have enough resource availble to make the cells you need

30
Q

What is the process of controlling erythropoiesis?

A
  1. Kidneys detect reduced O2-carrying capacity of the blood
  2. When less O2 is delivered to the kidneys, they secrete the hormone ERYTHROPOIETIN (EPO) into the blood
  3. EPO stimulates erythropoiesis in the bone marrow
  4. The additional circulating erythrocytes inc the O2 carrying capacity of the blood
  5. Inc O2-carrying capacity removes the stimulus that triggered erythropoietin secretion

This will eventually stabilise as this is a -ive feedback loop

31
Q

When red blood cells rupture in the spleen what does it break then down into?

A

Heme = made into iron & bilirubin

Globin = made into amino acids

32
Q

What happens to bilirubin once it has been broken down from heme?

A

It circulates & is then taken up by the LIVER & converted into bile —-> Bile is released into intestine (aids digestion & absorption of fats)

OR

Absorbed into circulation & picked up by KIDNEYS & excreted in the urine (gives it the yellow colour)

33
Q

Which organ monitors the oxygenation levels of blood?

A

Kidneys

34
Q

Which hormone is released to stimulate the production of RBCs?

A

Erythropoietin (EPO)

35
Q

What are the 2 places EPO can act on?

A
  • Act on initial stem cells & cause it to divide more
    OR
  • Act on stem cells further downstream –> preferred
36
Q

Why is it not optimal for EPO to act on inital stem cells?

A

It acts on them & causes them to divide more - you don’t want this to happen too much incase they acquire mutations

More stem cells dividing = inc risk of cancer

SO EPO acts on cells downstream from stem cells –> causes these cells to divide more before released into bloodstream

37
Q

How long does the process of making new RBCs, triggered by EPO take?

A

2-3 days

38
Q

What is a globin?

A

Protein made of 4 highly folded polypeptide chains

39
Q

What are hame groups?

A

4 iron-containing, nonprotein groups bound to the polypeptides

Each haem group can reversibly combine with one molecule of O2

40
Q

Why doe blood have a red colour?

A

Iron is present as Fe2+ - this appears as red

Oxygenated blood = bright red
Deoxygenated blood = dark red

41
Q

What % of O2 is carried in haemoglobin?

A

98.5% is carried in the blood bound to haemoglobin

This is bc O2 is poorly soluble in the plasma

42
Q

How does CO2 bind to RBCs?

A

It binds reversibly to polypeptide chains - not haemoglobin, it has a much higher affinity for O2 than CO2

43
Q

How does CO2 travel in the bloodstream?

A

Hb carries less CO2 than O2 - most is carried in plasma as hydrogen & bicarb ions:

Carbonic anhydrase found in erythrocytes - catalyses reversible conversion of CO2 and H2O to carbonic acid

RBCs don’t directly carry CO2

44
Q

How does CO bind to RBCs?

A

CO binds to haemoglobin directly (same site as O2)

It will preferentially bind to that site, hard to displace as the affinity for this is 240x

45
Q

Why do people suffer from carbon monoxide poisoning?

A

Red cells cannot carry O2 if there is CO present, as its affinity for CO is so much higher

RBCs cannot carry O2 therefore cells cannot respire & CO poisoning happens

46
Q

How does NO (nitric oxide) bind to Hb?

A
  • Binds to Hb in the lungs, released in the tissues
  • NO is a vasodilator –> relaxes and dilaes arterioles
47
Q

What is NO used for in the body?

A

Allows blood to circulate & helps maintain blood pressure as there’s always a small amt of NO in your bloodstream

It is used if the blood flow is blocked, it will be released in the affected area & will casue the blood vessel to dilate & let blood pass thru

48
Q

Explain the entire life cycle of iron in the bloodstream:

A
  1. There needs to be enough iron to produce RBCs - in body total amt of iron is about 4 grams, 65% ia as Hb –> is taken in from your diet from food
  2. Iron has to be atively absorbed in the digestive tract - means you can stop absorbing it if you don’t need to
  3. Something needs to transport it to where the cells are synthesised, this is done using TRANSFERRIN - it binds to iron & carries it in the plasma
  4. Sometimes we absorb too much iron, excess iron is stored in the liver as something called FERRITIN
  5. Any iron that you need will be used in bone marrow to make Hb and so you can produce the Hb that’s req to produce RBCs
  6. The RBCs will go into the circulation & will eventually encounter the spleen which converts Hb to bilirubin, this releases the iron
  7. Bilirubin will either be metabolised & excreted in bile
  8. Or can be broken down in the kidneys and excreted in urine or faeces
49
Q

What is evidence for anaemia involving DNA?

A

Insufficient iron in the diet will lead to a deficiency in DNA synthesis - it uses vitamin B12

This is a telltale sign of anaemia

50
Q

Summary of lecture:

A
  • Vast numbers or RBCs are produced each day
  • Turned over every 120 days
  • Regulation of exact no. is controlled by erythropoietin (EPO)
  • Kidney is responsible for monitoring O2 levels
  • Haemoglobin production relies on iron uptake
  • Haemoglobin breakdown releases bilirubin –> contributes to bile production

Human physiology (43 decks)

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