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MEDSCI201 > Cardiovascular System > Flashcards

Cardiovascular System Flashcards

1
Q

Diastole

A

filling

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2
Q

Systole

A

Contracting

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3
Q

Heart Development - before 3 weeks

A

Heart forms a straight tube on ventral midline. Relies on oxygenation and nutrient delivery via diffusion.

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4
Q

Heart Development - 3 weeks

A

Heart tube lengthens and starts to form S shaped tube. Primitive atrium moves dorsally towards head and primitive ventricle swings ventrally and towards the tail = cardiac looping

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5
Q

Heart Development - 3.5 weeks

A

As atrium moves towards head, it passes behind the bulbus cordis. The sinus venosus is carried with the atrium and disappears from our view. as it moves to the dorsal side of the heart, behind the ventricle

Growth is quicker in regions compared to junction, therefore bulging is pronounced. Sinus venosus is hidden and has horn projects on each side attached to three veins

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6
Q

Common cardinal vein

A

Drains the embryo

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7
Q

Umbilical vein

A

Carries oxygenated blood from placenta to embryo

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8
Q

Vitelline vein

A

Carries nutrient laden blood from the diminishing yolk sac to the SV

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9
Q

Heart Development - 4 weeks

A

Cardiac looping has finished

Horns of the sinus venosus now enter the atria on cranial and dorsal side. Interatrial septum forms, beginning chamber formation, one on each side of the bulbus cordis. Primitive ventricle forms caudal apex of the heart. Interventricular septum begins to form at old bulboventricular junction, separating LV and RV

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10
Q

Heart Development - 5 weeks

A

Sinus venosus is no longer recognisable
Blood returning from body drains mostly to the right side.
Right horn enlarges & contributes to the right atrial wall
Left horn diminishes and eventually forms the coronary sinus (draining blood from cardiac veins back to RA.)

Distal part of Bulbus Cordis splits into Conus cordis and Truncus arteriosus

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11
Q

Conus cordis

A

Forms the outflow tracts of both ventricles

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12
Q

Truncus arteriosus

A

Form proximal aorta and pulmonary trunk

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13
Q

Heart Development - 6 weeks

A

SVC & IVC are established
Ridges run lengthwise inside the truncus arteriosus and conus cordis. Ridges run in a spiral and when fusion occurs will form a spiral partition or septum

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14
Q

Heart Development - 7-8 weeks

A

Aorta (Ao) and Pulmonary trunk (Pt) become separate vessels twisting around another. Caudal part of spiral septum contributes to interventricular septum that separates the two ventricles

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15
Q

Heart Development - Full term fetus

A

Pulmonary trunks gives rise to left, right pulmonary arteries and ductus arteriosus. Interatrial septum is incomplete allowing blood to pass from RA to LA

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16
Q

Ductus Arteriosus

A

Transfers most of the blood from he pulmonary into the aorta

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17
Q

Formation of interatrial septum

A
  1. Downgrowth of septum primum and formation of L and R endocardial cushion.
  2. Fusion of inferior and superior endocardial cushion forms septum intermedium
  3. Cell death creates ostium secundum
  4. Downgrowth of thick septum secundum. Ostium primum completed sealed
  5. Septum secundum stops growing and foramen ovale forms allowing blood flow for RH to LH
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18
Q

Fetal circulation: overall pattern

A

Fetus lungs are fluid filled
Pulmonary capillaries are compressed, resistance to blood flow through lungs is higher than systemic. Blood takes lower resistance path through ductus arteriosus into aorta rather than high resistance path.

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19
Q

Placenta

A

Drains oxygen rich blood back via the umbilical vein (liver)

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20
Q

Changes at birth

A

Resistance decreases

  1. Infant takes first breath, lungs inflate and replaces fluid. Capillaries expand and resistance to blood flow decreases
  2. Blood leaving right ventricle travels through low resistance lung pathway rather than high resistance ductus arteriosus into the systemic circuit.
  3. Blood travels through the left side for the first time
  4. Umbilical vein constricts and is clamped. Venous return to placenta is 0. Inflow to RA from systemic circuit decreases, RA pressure falls
  5. LA pressure exceeds RA pressure. Septum primum closes, the foramen closes separating the two atria
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21
Q

L ventricle

A

Pump
95mmHg
Thick muscular walls, inlet & outlet valves

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22
Q

Large arteries

A

Conduct blood away from pump
Store blood during systole, releasing it during diastole
95mmHg
Elastic walls

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23
Q

Medium-sized arteries

A

Distribute blood to body
95-85 mmHg
Muscular walls to control diameter, plus CT ofr strength

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24
Q

Arterioles, metarterioles, precapillary sphincters

A

Control distribution of blood to capillaries
85-35mmHg
Smooth muscle to control diameter, little CT

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25
Q

Capillaries

A

Exchange
35-15mmHg
Very thin walls, no muscle or CT

26
Q

Venules

A

Collect blood
Thin walled, larger diameter

27
Q

Veins

A

Conduct blood to pump
15-0mmHg
Thin walled, variable structure, valves to assist return

28
Q

R. Atrium

A

Reservoir & pre-pump
0-2mmHg
Thin, muscular walls

29
Q

Muscular arteries

A

10mm - 0.5mm

Has 3 tunics
Tunica intima
Tunica media
Tunica adventitia

30
Q

Tunica Intima

A

Innermost coat
Endothelium
Basement membrane
Subendothelial CT
Internal elastic lamina - smooth but longitudinal folds after death

31
Q

Tunica Media

A

Middle and thickest coat
SM control diameter
Elastin fibres give resiliency
Collagen fibres limit expansion and prevent rupture
Sometimes has external elastic lamina

32
Q

Tunica Adventitia

A

Outermost coat
Usually only collagen and elastin fibers
Vaso vasorum to service the outer layers of the vessel wall.

33
Q

Artherosclerosis

A

Disease of intima
Formation of plaques (atheromas) containing fat and collagen. Caused from damage (shear stress, toxins (smoking), lipid diet) to the endothelium

34
Q

Atherosclerosis problems

A

Narrowing of BV
Thrombus (bludclart)
Embolus (stroke)
Aneurism
haemorrhage

35
Q

Endothelium in Atherosclerosis

A

Loses ability to regulate whether cholesterol leaves the blood and enters blood vessel wall. Low surface area to volume ratio -> harder to reabsorb it

Macrophages accumulates lipid to form foam cell. Accumulation of hydrophobic lipids

36
Q

Elastic arteries

A

20mm-10mm
Layers:
Tunica Intima
Tunica media
Tunica adventitia

37
Q

Elastic arteries function and location

A

Aorta and Pulmonary arteries, downstream of ventricles.

Store blood during systole and recoil during diastole to squeeze blood outwards into arterial tree

38
Q

Tunica Intima

A

Endothelium
Subendothelial CT
IEL

Is thicker than muscular arteries and contains longitudinal elastin fibres in subendothelial CT

39
Q

Tunica Media

A

Lamellar units
(Fenestrated sheet of elastin
Smooth muscle
Collagen)

50-60 lamellar units in aorta.

40
Q

Tunica adventitia

A

EEL
Collagen
Small BV and autonomic nerves

41
Q

Transition from elastic to muscular

A

Gradual not abrupt

42
Q

Aneurysms

A

Thin, weak section of artery wall which bulge outwards. Weakness may arise from trauma, congenital defect or by atherosclerosis

43
Q

Berry aneurysms

A

Occur at branch points of cerebral arteries and rupturing causes bleeding into subarachnoid space or into the brain substance

44
Q

Dissecting aneurysms

A

Affect aorta, vessel weakened by atherosclerosis and media is penetrated by blood entering the intima. The split dissects the media over time and if the adventitia fails, death frequently occurs

45
Q

Arterioles

A

Smallest of muscular arteries
0.1mm
Wall thickness equal to diameter of lumen

Layers
endothelium
IEL - in larger arterioles
Smooth Muscle Fibre - 3 or fewer
Collagen

For their size have the thickest muscle coat in media.

Greatest pressure drop occurs

46
Q

Hypertension

A

Sustained, elevated blood pressure

Arteries constrict to try maintain correct pressure in the capillaries. Arteriole media enlarges and the internal media enlarges and the internal elastic lamina splits and reduplicates. The intima becomes thickened with collagen, thus narrowing the lumen of the vessel

47
Q

Primary hypertension

A

No single cause can be found. 90% of cases

48
Q

Secondary hypertension

A

Cause can be identified
Can be caused by anything that increases cardiac output ( increases in sympathetic activity from stress)

49
Q

Microcirculation

A

The order of blood flow in small arterioles, capillary bed and postcapillary venules.

Distribution is controlled by terminal arterioles (single layer of SM) and metarterioles (incomplete layer of muscle). Precapillary sphincter controls entry into each capillary. Relaxation allows blood to flow through capillaries.

50
Q

Capillaries

A

Exchange with tissue fluids
Endothelium with basal lamina
8-10 um

51
Q

Continuous capillaries

A

Endothelial cell forms a continuous sheet

52
Q

Fenestrated capillaries

A

Endothelial cells are perforated with numerous small fenestrae

53
Q

Continuous capillaries with closed intercellular clefts

A

Tight junctions make a complete seal. Occurs in the CNS and is responsible for the blood-brain barrier

54
Q

Continuous capillaries with open intercellular clefts

A

6nm clefts permit the passage of water,ions and small molecules NOT plasma proteins

Pericytes wrap around and can differentiate into SM cells

Found in muscle, CT, lungs, most common continuous capillary

55
Q

Fenestrated capillaries with closed perforations

A

fenestrae are about 60nm in diameter but are closed by a non-membranous diaphragm. Diaphragm restricts passage of proteins but not water

Most common intestine

56
Q

Fenestrated capillaries with open perforations

A

Leaky as fluid exchange is important

Endocrine glands and kidney glomeruli

57
Q

Sinusoids

A

Wide-pore capillaries (>9um) between edges of adjacent endothelial cells, allowing easy passage of large molecules and cells.

Sinusoids occur in bone marrow and the spleen where red blood cells leave the bloodstream

58
Q

Endothelium

A

Detect changes in blood pressure, blood flow and blood composition

Secrete molecules such as prostacyclin and NO causing SM relaxation and endothelin causes contraction.

Discourage platelets from adhering and do not stimulate blood coagulation. During injury, they can promote thrombosis

59
Q

Endothelium in atherosclerosis

A

Hypertension endothelial cells release factors (eg. platelet-derived growth factor PDGF) which cause SM cells to change their form; they proliferate, enlarge and migrate to the intima.

60
Q

Postcapillary venules

A

10-25um in diameter drain capillary beds
Lack SM (have pericytes)
During inflammation, respond to histamine and serotonin with increased leakage of blood plasma into tissue fluid, causing swelling (oedema) and migration of neutrophils through vessel wall.

61
Q

Muscular venules

A

Larger (20-100 um)
Up to two layer of smooth muscle in media (no IEL)
Characterized by thin wall in relation to their diameter and by endothelial nuclei which bulge into lumen

MEDSCI201 (20 decks)

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