Lecture 29 - Cardiovascular 2

Question 1

describe the oxygenation of the two vena cavas

Answer 1

one has lower oxygenation than the other

Question 2

capillaries of the head and arms drain into the right atrium via which vessel?

Answer 2

the superior vena cava

Question 3

describe the lungs before birth

Answer 3

• filled with lung fluid
• no gas exchange
• slow to develop
  therefore very high percentage

Question 4

before birth, where does the deoxygenated blood from the right ventricle go?

Answer 4

a little bit goes through the pulmonaary circuit, but mostly goes through the ductus arteriosis and to the capillaries of the placenta to pick up O2 blood

Question 5

what happens to the little bit of deoxygenated blood flowing through the pulmonary circuit?

Answer 5

it comes back into the left atrium

Question 6

why is the blood coming into the right atrium in fetal circulation unique?

Answer 6

oxygenated blood from the placenta and deoxygenated blood from the viscera and legs both come back to the right atrium in a way that they don’t mix
- called laminar flow

Question 7

why doesn’t the blood coming into the right atrium mix?

Answer 7

because the oxygenated placental blood is physiologically different (pH, flow rate etc)

Question 8

which blood vessel coming into the right atrium contains two blood types with laminar flow?

Answer 8

the inferior vena cava

Question 9

what does the valve of the IVC/eustachian valve do?

Answer 9

it channels the oxygenated blood from the placenta to the foramen ovale

Question 10

explain the pathway of oxygenated blood in fetal circulation

Answer 10

• deox blood goes through ductus arteriosis and little bit pulmonary circuit
• blood becomes ox from placenta and does laminar flow alongside deox blood from viscera
• the valve of the IVC channels the ox blood to the foramen ovale, which pushes septum primum aside as it passes through the septum secundum, goes into the left atrium.
• the little bit of deox blood from the pulmonary circuit only very slightly dilutes the ox blood from placenta
• into left ventricle where pumped out through aorta

Question 11

how long does the laminar flow need to be maintained for and why?

Answer 11

only a short anatomical distance due to the placenta –> liver’s hepatic veins —> IVC, which are all in close proximity

Question 12

where does the oxygenated blood go after the left ventricle?

Answer 12

• through the aorta, where most of it will mix with the ductus arteriosis deox blood, but before that, the most oxygenated blood is sent up to the head and face (brain v important)
• through the coronary arteries

Question 13

what is the first change that happens at birth?

Answer 13

the infant takes its first breath and the non-compressible liquid is replaced with a compressible gas.
- resistance plummets quickly

Question 14

what is the second change that happens at birth?

Answer 14

far less blood flow through ductus arteriosis
after the fluid is replaced with compressible air in the lungs, resistance drops and blood flows through the low res pulmonary circuit over the higher res ductus arteriosis

Question 15

true or false, after baby’s first breath no blood flows through the ductus arteriosis

Answer 15

false, there is still a tiny amount of flow

Question 16

what is the third change that happens at birth?

Answer 16

more volume of blood coming into the left atrium from pulmonary circuit and increases pressure of L.A

Question 17

what is the fourth change that happens at birth?

Answer 17

more blood through pulmonary circuit means less blood through systemic and less blood returning to R.A

Question 18

what is the fifth change that happens at birth

Answer 18

LA pressure exceeds RA pressure, and so the blood tries flowing into the RA from LA, pushing the septum primum against the septum secundum and closing the foramen ovale

Question 19

how does the removal of the placenta effect the pressure of the systemic circuit?

Answer 19

it was a high flow low pressure component, then removed the systemic circuit became higher pressure

Question 20

what is the last change that happens after birth

Answer 20

low oxygen in the ductus arteriosis causes smooth muscle to constrict and close off the vessel after a couple days

Question 21

what happens if the ductus arteriosis doesn’t close?

Answer 21

blood leaving through the aorta (high pressure) preferentially flows back through ductus arteriosis into the pulmonary trunk (low pressure of pulmonary circuit) and starves vital organs of ox blood and then organ failure

Question 22

what is unique about the cross section of a newborn’s heart at the ventricle level?

Answer 22

the wall thicknesses are the same, and eventually will prefer the left due to working that muscle more to create high pressures and get thicker

Question 23

what is the feature of muscular arteries which is most significant?

Answer 23

they have the most clearly defined of the three tunics

Question 24

what are the tunicas of the muscular arteries?

Answer 24

• tunica intima
• tunica media
• tunica adventitia

Question 25

not all blood vessels have a tunica?

Answer 25

media or adventitia. all have a tunica intima

Question 26

describe the tunica intima

Answer 26

4 layers: - endothelial cells (most important) - basement membrane of endothelial cells - subendothelial CT - internal elastic lamina IEL, smooth in life but longitudinal folds after death

Question 27

what is the diameter of muscular arteries

Answer 27

10mm -> 0.5mm large variation

Question 28

describe the tunica media

Answer 28

- thickest coat with lots of smooth muscle controlled by autonomic nervous system. - contains elastic fibres and collagen fibers for structure and preventing over stretching - has an external elastic lamina EEL which is not as prominent as the IEL

Question 29

describe the tunica adventitia

Answer 29

loose CT with collagen and elastic fibres - can contain vasa vasorum and autonomic fibres

Question 30

what are the vasa vasorum?

Answer 30

blood vessels in the tunica adventitia of large muscular arteries that require their own separate blood flow

Question 31

what do autonomic fibers do?

Answer 31

they control the smooth muscle of muscular arteries from the tunica adventitia

Question 32

what is atherosclerosis?

Answer 32

disease of the tunica intima of muscular arteries, which is characterised by plaques (artheromas) containing fat and collagen fibres which looks like a 'porridge-like growth

Question 33

what causes atherosclerosis?

Answer 33

primarily caused from damage to the endothelium - shear stress on diverging blood vessels - toxins (smoking) - high cholesterol/lipid diet - viral infection

Question 34

describe the process of a lipid-induced atherosclerosis

Answer 34

lipids in blood can enter the tunica intima and the endothelium senses this and initiates an inflammatory response, which causes monocytes to differentiate into macrophages which engulf the lipids, which form droplets inside the macrophages and become foam cells. foam cells die and release bigger droplets of lipids called extracellular lipids

Question 35

atheroscleoris in blood vessels of the brain cause?

Answer 35

strokes

Question 36

what do smooth muscle cells do in response to damage via atherosclerosis?

Answer 36

some smooth muscle cells differentiate into macrophages, which then become foam cells etc some other smooth muscle cells are told to put down collagen to try and bind up weak areas of the blood vessel but instead make it stiffer and makes it harder to remove the plaque and locks it in. the endothelium may rupture after collagen fibers

Question 37

why are extracellular lipids more problematic?

Answer 37

less surface area, larger and harder to break down

Question 38

what happens to the internal elastic lamina in artherosclerosis?

Answer 38

it begins to degenerate