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MEDSCI201 > Cardiovascular System > Flashcards

Cardiovascular System Flashcards

(61 cards)

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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 for 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
Capillaries
Exchange 35-15mmHg Very thin walls, no muscle or CT
26
Venules
Collect blood Thin walled, larger diameter
27
Veins
Conduct blood to pump 15-0mmHg Thin walled, variable structure, valves to assist return
28
R. Atrium
Reservoir & pre-pump 0-2mmHg Thin, muscular walls
29
Muscular arteries (size and tunics)
10mm - 0.5mm Has 3 tunics Tunica intima Tunica media Tunica adventitia
30
Tunica Intima of muscular arteries
Innermost coat Endothelium Basement membrane Subendothelial CT Internal elastic lamina - smooth but longitudinal folds after death
31
Tunica Media of muscular arteries
Middle and thickest coat SM control diameter Elastin fibres give resiliency Collagen fibres limit expansion and prevent rupture Sometimes has external elastic lamina
32
Tunica Adventitia of muscular arteries
Outermost coat Usually only collagen and elastin fibers Vaso vasorum to service the outer layers of the vessel wall.
33
Artherosclerosis
Disease of intima Formation of plaques (atheromas) containing fat and collagen. Caused from damage (shear stress, toxins (smoking), lipid diet) to the endothelium
34
Atherosclerosis problems
Narrowing of BV Thrombus (bludclart) Embolus (stroke) Aneurism haemorrhage
35
Endothelium in Atherosclerosis
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
Elastic arteries size and layers
20mm-10mm Layers: Tunica Intima Tunica media Tunica adventitia
37
Elastic arteries function and location
Aorta and Pulmonary arteries, downstream of ventricles. Store blood during systole and recoil during diastole to squeeze blood outwards into arterial tree
38
Tunica Intima of Elastic arteries
Endothelium Subendothelial CT IEL Is thicker than muscular arteries and contains longitudinal elastin fibres in subendothelial CT
39
Tunica Media of Elastic arteries
Lamellar units (Fenestrated sheet of elastin Smooth muscle Collagen) 50-60 lamellar units in aorta.
40
Tunica adventitia of Elastic arteries
EEL Collagen Small BV and autonomic nerves
41
Transition from elastic to muscular
Gradual not abrupt
42
Aneurysms
Thin, weak section of artery wall which bulge outwards. Weakness may arise from trauma, congenital defect or by atherosclerosis
43
Berry aneurysms
Occur at branch points of cerebral arteries and rupturing causes bleeding into subarachnoid space or into the brain substance
44
Dissecting aneurysms
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
Arterioles
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
Hypertension
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
Primary hypertension
No single cause can be found. 90% of cases
48
Secondary hypertension
Cause can be identified Can be caused by anything that increases cardiac output ( increases in sympathetic activity from stress)
49
Microcirculation
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
Capillaries
Exchange with tissue fluids Endothelium with basal lamina 8-10 um
51
Continuous capillaries
Endothelial cell forms a continuous sheet
52
Fenestrated capillaries
Endothelial cells are perforated with numerous small fenestrae
53
Continuous capillaries with closed intercellular clefts
Tight junctions make a complete seal. Occurs in the CNS and is responsible for the blood-brain barrier
54
Continuous capillaries with open intercellular clefts
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
Fenestrated capillaries with closed perforations
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
Fenestrated capillaries with open perforations
Leaky as fluid exchange is important Endocrine glands and kidney glomeruli
57
Sinusoids
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
Endothelium
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
Endothelium in atherosclerosis
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
Postcapillary venules
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
Muscular venules
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 (21 decks)

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