Intro and haaemodynamics Session 1

Question 1

heart requires it’s own blood supply

Answer 1

distance of cells of LV from source of O2 and nutrients too far, serious damage will be caused if vessels to LV are blocked

Question 2

capillaries

Answer 2

single layer of endothelial cells surrounded by a basal lamina

Question 3

perfusion rate

Answer 3

perfusion rate= rate of blood flow

Question 4

factros affecting diffusion

Answer 4

• SA available for exchange (generally quite large)
• resistance to diffusion - nature of barrier, nature of molecule, diffusion distance
• conc. gradient (higher blood flow= higher conc. of nutrients in capillary blood - substance in tissue at lower conc. than in capillary blood)

Question 5

capillary density

Answer 5

more metabolically active tissue have more capillaries = higher capillary density

Question 6

perfusion rate at rest and exercise

Answer 6

• at rest = 5L.min^-1
• during execrcise can rise to 25L.min^-1

Question 7

perfusion rate of organs(brain, heart, kidney,)

Answer 7

• brain = 0.5ml.min^-1.g^-1
• hert = 0.9 to 3.6 ml.min^-1.g^-1
• kidneys = 3.5ml.min^-1.g^-1 - constant, high
• gut - high after a meal
• skeletal muscle - high during exercise

CVS must supply between 5 and 25 L of blood to tissues whilst at all times maintaining perfusion to vital organs such as brain, heart and kidneys

Question 8

layers of the pericardium

Answer 8

Question 9

fluid in the pericardium

Answer 9

• usually thin film of fluid
• if excess builds up rapidly can compress heart due to inextensible fibrous layer
• compression of heart can lead to cardiac tamponade
• fluid removed by pericardiocentesis
  
  • for testing/ relieve compression

Question 10

coronary arteries

Answer 10

• end arteries - few anastamoses
• prone to atheroma
  
  • (degeneration of arterial walls caused by build-up of fatty deposits or scar tissue leading to restriction of blood flow and thrombosis)
• vital to supply oxygenated blood to myocardium

Question 11

anterior view of coronary arteries

Answer 11

Question 12

posterior view of coronary arteries

Answer 12

Question 13

anterior view of cardiac veins

Answer 13

Question 14

posterior view of cardiac veins

Answer 14

Question 15

blood, plasma, serum

Answer 15

• blood = mix of cells + plasma
• fluid from unclotted blood = plasma
• fluid from clotted blood = serum
  
  • serum = plasma without clotting factrors (especially fibrinogen)

Question 16

increase in plasma viscosity can lead to increase in whole blood viscosity - most common cause?

Answer 16

multiple myoloma = cancer of plasma (antibody produccing) cells

Question 17

rbc and wbc counts effect blood viscosity

Answer 17

• increase in red blood cells= polycythaemia
• increase in platelets = thrombocythaemia
• increase in white cells = leukaemia
  
  • > all can lead to increase in whole blood visocsity and slugging of blood in peripheries

Question 18

changes in plasma viscosity can be caused by acute plasma proteins e.g. fibrinogen, complement factors or C-reative protein, inflammation?

Answer 18

• these protein levels can rise in response to inflammation
• changes in plasma viscosity can be used to measure inflammatory response
• CRP more commonly used to measure inflammation

Question 19

laminar blood flow

Answer 19

• blood usually flows in streamlines - laminar flow
  
  • velocity of blood in centre of vessel is greater than outer edge - leading to parabolic profile

Question 20

turbulent blood flow

Answer 20

• blood flowing in all directions - continually mixing
• occurs when
  
  • blood passes an obstruction in a vessel
  • rate of flow is too high when passes over rough surface + increased resistence to blood flow

Question 21

stenosis

Answer 21

abnormal narrowing of a passage in body

Question 22

trace of pressure in descending aorta

Answer 22

• anacroticlimb = upbeat - when ventricle contracts forcing blood into aortic arch
• dicrotic notch - aortic valve closes - no more blood leaves ventricle - end of systole

Question 23

pulse pressure and mean arterial pressure

Answer 23

• pulse pressure= systolic pressure - diastolic pressure
  
  • most commonly 120-80 = 40mmHg
• mean arterial pressure = diastolic pressure + 1/3 of pulse pressure
  
  • usually = 80 + 13 = 93mmHg
  • if this falls below 70 then organ perfusion is impaired

Question 24

Strength (also called volume) of pulse determined by 2 things (1)

Answer 24

(what we feel as a pulse is in fact a shok wave that arrives sllightly before blood itself)

strength determined by:

• Force that the left ventricle ejects blood into the arterial system. Reduced pulse volume can result from left ventricular failure, aortic valve stenosis, hypovolaemia, etc. leading to a thready pulse

Question 25

Strength (also called volume) of pulse determined by 2 things (2)

Answer 25

The strength or volume of the pulse depends on:

• The pulse pressure; the stronger the pulse pressure, the stronger the pulse. A strong pulse is said to be bounding.

Question 26

causes of a bounding pulse

Answer 26

• Bradycardia (slow heart rate), such as hot block, widens pulse pressure and leads to a bounding pressure- pulse pressure increased due to lower end diastolic pressure
• Low peripheral resistance (e.g. hot bath, exercise, and pregnancy) lowers diastolic pressure and therefore increases pulse pressure

Question 27

when measuring bp

Answer 27

• When measuring BP, pulse obliteration pressure (when pulse disappears) is the systolic pressure-phase 1 sound
  
  • onset of phase 1 sounds also same as systolic pressure
• when can no longer hear pulse= diastolic pressure - phase 5 sound

Korotkoff sounds are the sounds that medical personnel listen for when they are taking blood pressure

When standing, blood pressure at heart lower than in feet. Patient usually sitting maybe even lying down when bp measured