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Phys Pharm > TOPIC 5 - The circulatory system > Flashcards

TOPIC 5 - The circulatory system Flashcards

1
Q

How is the heart organised into 3 functional parts?

A
  1. Pump (heart)
  2. Fluid (blood)
  3. Set of containers (blood vessels)
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2
Q

Why is the heart a dual pump?

A

Because the heart pumps blood in two serial circuits:

Left heart - Systemic circulation:
- Parallel pathways from left to right

Right heart - Pulmonary circulation:
- Single pathway from right to left side of heart

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3
Q

What is the role of arteries, microcirculation and veins?

A
  • Arteries - the distribution system
  • Microcirculation - diffusion and filtration systems
  • Veins - collection system (reservoir)
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4
Q

What are the 4 ‘building blocks’ in vascular wall?

A

1) Endothelial cells
2) Elastic fibres
3) Collagen fibres
4) Smooth-muscle cells

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5
Q

What are the 3 layers in the blood vessel walls?

A

Blood vessel walls - 3 layers:

  1. intima (Tunica Interna)
  2. media (Tunica Media)
  3. adventitia (Tunica Externa)

Capillaries - only intimal layer resting on a basement membrane

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6
Q

Describe the structure of Elastic arteries (large arteries)?

A
  • High compliance - walls stretch easily without tearing in response to pressure increase –> Enables vessels (e.g. aorta) to cope with peak ejection pressures.
  • Elastic fibres - Recoil of elastic fibres forces blood to move even when the ventricles are relaxed
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7
Q

What is the function if muscular arteries?

Describe the structure of MUSCULAR
arteries (medium sized arteries)

A

Muscular arteries control blood flow and pressure.

  • Smooth muscle cells are arranged circumferentially
  • Capable of greater vasoconstriction and vasodilation to adjust the rate of blood flow
  • Vascular tone – state of partial contraction maintains vessel pressure and efficient flow.
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8
Q

Describe the structure of arterioles.

A
  • Arterioles have smooth muscle enabling regulation of blood flow into capillary networks regulated microcirculation
  • Terminal regions of arterioles are known as metarterioles
  • Precapillary sphincters monitor blood flow into the capillary
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9
Q

Describe the structure of Venules.

A
  • Postcapillary venules are porous - act as exchange sites for nutrients and waste
  • Muscular venules have a thin smooth muscle cell layer (less muscular than arterioles)
  • Thin walls allow expansion - excellent reservoirs for blood
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10
Q

Describe the structure of veins

A
  • Less muscular and elastic but distensible enough to adapt to variations in volume and pressure of blood
  • Like venules, veins can “store” blood
  • Veins have valves (prevent backflow)
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11
Q

Describe the structure of veins

A
  • Less muscular and elastic but distensible enough to adapt to variations in volume and pressure of blood
  • Like venules, veins can “store” blood
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12
Q

Describe the structure of large veins.

A
  • More muscular than venules and smaller veins
  • Possess valves to prevent backflow
  • Defective, leaky valves allow backflow and can lead to varicose veins
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13
Q

What is the function of the capillary?

A

Capillary – principal exchange site:

  • Gases
  • Water
  • Nutrients
  • Waste products

Most tissues capillaries serve -nutritional needs, in addition:

  • Glomerular filtrate
  • Skin temperature regulation
  • Hormone delivery
  • Platelet delivery
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14
Q

Describe the structure of capillaries.

A
  • Small vessels composed only of endothelial cells and basement membrane
  • Exchange of substances between blood and interstitial fluid
  • Three groups based on their degree of ‘leakiness’
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15
Q

Describe the structure of capillaries.

A
  • Small vessels composed only of endothelial cells and basement membrane
  • Exchange of substances between blood and interstitial fluid
  • Three groups based on their degree of ‘leakiness’
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16
Q

Who’s equation is used for fluid transfer in capillaries and what is fluid transfer?

A

Starling’s Forces

  • Fluid transfer across capillary walls driven by sum of hydrostatic and osmotic pressures
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17
Q

What is oncotic pressure?

A

Oncotic pressure (colloid osmotic pressure) due to serum proteins (albumin)

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18
Q

What is hydraulic conductance?

A

Kf hydraulic conductance (water permeability of capillary wall) varies with tissue

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19
Q

If there is a blockage in the lymphatic system?

A

Blockage leads to Oedema.

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20
Q

What is the function of the lymphatic system?

A
  • Drains excess interstitial fluid
  • Transport of dietary lipids
  • Lymph nodes/organs - immunology
21
Q

How do the Starling forces change across the capillary wall?

A

Pc (capillary hydrostatic pressure) declines along length of capillary.

Net filtration becomes net absorption.

22
Q

What are the key components of blood?

A
  • plasma
  • erthrocytes
  • Leukocytes
  • platelets
23
Q

What is plasma?

A

Watery solution of electrolyres, plasma proteins, carbs and lipids.

24
Q

What are erythrocytes?

A
  • most abundant element in blood (haematocrit).
  • non-nucleated biconcave disc = maximises SA: vol ratio.
  • carries O2 from lungs to systematic system
  • C02 carriage from tissues to lungs
25
Q

What are leucocytes?

A

Are white blood cells…

can be granulocytes - neurtrophils, eosinophils and basophils.

or non-granular - lymphocytes and monocytes.

26
Q

What are platelets and how do they form?

A

Platelets are nucleus free fragments.

They bud-off from megakaryocytes in bone marrow.

27
Q

What does blood viscosity measure?

How does blood flow viscosity change with increasing haematocrit?

A

Viscosity measures resistance to sliding of shearing fluid layers.

Blood flow decreases with increasing haematocrit.

28
Q

How is blood flow affected by velocity?

A

Velocity increases from wall to centre - RBC moves faster in the centre of the arteriole.

In a cylindrical blood vessel, laminae of blood are concentric cylinders.

29
Q

how does blood flow turbulence occur?

A

At high flow rate, blood flow is no lionger laminar - but turbulent.

Turbulent flow when radius is large, velocity is hight or local stenosis.

laminar flow = silent
turbulent flow = murmurs.

30
Q

What is haemostasis and how does it occur (4 ways)?

A

It is the prevention of a haemorrhage (blood clotting that stops excessive blood loss).

Haemostasis from….

  1. Vasoconstriction
  2. Increased tissue pressure
  3. Platelet plug (adhesion, activation and aggregation)
  4. Coagulation/clot formation
31
Q

What is a thrombus?

A

an intravascualr clot

32
Q

How is a blood clot prevented?

A
  • homeostatic mechanisms prevent haemostasis.

- endothelial cells - maintain normal blood fluidity through paracrine and anticoagulant factors.

33
Q

What 3 layers does the heart wall contain?

A

Epicardium
Myocardium
Endocardium

34
Q

Describe the sequence of depolarisation through the heart.

A

1 ) cells of SA node depolarise to fire action potentials at regular rate.

2) Cardiac cells electrically coupled through gao junctions conduct cell to cell through right and left atrial muscle - atrial systole
3) Signal arrives at atrioventricular node.
4) impulse spread prevented by fibrous atrioventricualr ring (non-conducting tissue) so impulse spreads from AV to His-purkinje within ventricles so leads to ventricular systole.

35
Q

What are the steps A-G of the cardiac cycle?

A

A - atrial systole

B - Isovolumetric ventricular contraction

C - Rapid ventricular ejection

D - Reduced ventricular ejection

E - Isovolumetric ventricular relaxation

F - Rapid ventricular filling

G - Reduced ventricular filling

36
Q

What does an an ECG electrocardiogram detect?

A

ECG records the summed electrical activity of the heart - the depolarisation and repolarisation events of the cardiac cycle.

37
Q

What does the P wave show in an ECG?

A

Depolarisation of atria

P wave duration = atrial conduction time

38
Q

What does the PR interval show in ECG?

A

AV node conduction - shows initial depolarisation of atria to that of ventricles.

39
Q

What does QRS complex show in ECG?

A

depolarisation of ventricles

40
Q

What does T wave show on ECG?

A

Repolarisation of ventricles.

41
Q

What is the equation for velocity of blood flow?

A

V = Q/A

velocity = flow / area

42
Q

What is the relationship between blood flow, resistance and pressure?

A

Blood flow is determined by the pressure difference between vessel inlet and outlet and resistance to blood flow.

43
Q

Why is there resistance to blood flow?

A

Poiseuille’s Law

Resistance due to: 
•	Blood vessel diameter
•	Vessel length
•	Series/parallel arrangement
•	Blood viscosity
44
Q

How does blood pressure vary in the cardiovascular system?

A

Blood pressure decreases as blood flows as energy is consumed by frictional resistance.

45
Q

What is the equation for pulse pressure?

A

pulse pressure = systolic - diastolic pressure

46
Q

What is the equation for the mean arterial pressure?

A

mean arterial pressure = diastolic pressure + 1/3 pulse pressure

47
Q

How is blood pressure regulated in both short and long term?

A

Short term = baroreceptors, chemoreceptors, ADH

Long term = renin - angiotensin - aldosterone (RAAs) system regulates blood volume.

  • angiotension -> angiotensin 1 -> angiotensin 2 (acts on adrenal cortex to make and secrete aldosterone)
48
Q

What is hypertension and how can it be treated?

A

a long term elevation of blood pressure –> Chronic hypertension can desensitise baroreceptors

treated with ACE inhibitors, ARBs, diuretics, alpha blockers, renin inhibitors.

Phys Pharm (6 decks)

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