Cardiovascular System

	Pulmonary circuit	Systemic circuit
Driven by	Right heart	Left heart
Supplies	Lungs only	~11 organ systems (everything else)
Size/volume	Small (~9% of blood volume)	Large (~84% of blood volume)
Arterial pressure	Medium	High

compare the pulmonary systemic circuits

• arteries — carry blood away from the heart

• veins — carry blood towards the heart

• pulmonary arteries — carrydeoxygenated blood (heart → lungs); pulmonary veins carry oxygenated blood (lungs → heart) — the opposite of the systemic circuit

outline the key definitions of arteries and veins

• blood from the gut capillary bed doesn’t go straight back to the heart; it’s routed via the hepatic portal vein to a second capillary bed in the liver before finally returning to the heart

• a portal vein connects two capillary beds without passing through the heart in between

outline the hepatic portal vein

1. a volume-changing chamber

2. an inlet valve

3. an outlet valve

what are the three components required to build a ventricular pump

• filling: chamber relaxes → volume increases, pressure decreases → inlet valve opens (passively fills), outlet valve stays shut (prevents reflux)

• ejection: chamber contracts → volume decreases, pressure increases, inlet valve shuts (prevents backflow), outlet valve opens once chamber pressure > arterial pressure

what happens to chamber volume, pressure, and valves during the filling phase vs. ejection phase

• atrium: acts as a reservoir upstream to collect venous blood while the inlet valve is closed during ejection (allows fast refilling)

• inlet/outlet proximity: positioning them close together allows the ventricle to shorten in both length and width during contraction (increases efficiency)

• auricle: an appendage on the atrium that increases its reservoir capacity

what are the physiological functions of adding an atrium, moving valve positions, and adding an auricle when building a ventricular pump

• right heart (deoxygenated): SVC/IVC → right atrium (+ auricle) → right ventricle → pulmonary trunk → L/R pulmonary arteries → lungs

• left heart (oxygenated): pulmonary veins → left atrium (+ auricle) → left ventricle → aorta → systemic circuit

what are the pathways for deoxygenated vs. oxygenated blood through the heart

• interventricular sulcus: surface groove marking the boundary between the ventricles

• heart’s base: broad end (mostly left atrium) facing posteriorly; pulmonary vein connections are mainly visible from the posterior view

describe the location of the interventricular sulcus and the heart’s base

• right atrium (vertical): SVC enters from above, IVC from below (reflects systemic circuit above and below the heart)

• left atrium (horizontal): pulmonary veins enter from both sides (reflects lungs sitting on either side of the heart)

how does the anatomical orientation of the right vs. left atrium reflect what drains into them

Chamber	Peak pressure
Left atrium	~8 mmHg
Right atrium	~5 mmHg
Right ventricle	~27 mmHg
Left ventricle	~120 mmHg

what are the normal peak pressures (in mmHg) for the four chambers of the heart

• atria: low-pressure receiving chambers (only need enough pressure to top up the ventricles)

• ventricles: high-pressure ejecting chambers (must generate high force to push blood into arterial circuits)

how do peak pressures reflect the difference in function between the atria and ventricles

• the left ventricle drives blood through the systemic circuit, which is much larger and has much higher vascular resistance than the small pulmonary circuit driven by the right ventricle

why does the left ventricle generate significantly higher peak pressure than the right ventricle

• efficiency: they lack inlet valves, meaning some blood is pushed backward into the veins when they contract; they only “top up” the ventricles

• structure: walls are very thin, made of bundles of pectinate muscle with light gaps between them

why are the atria inefficient pumps during atrial systole (“atrial kick”), and what is their wall structure

• the peak pressure that the specific chamber must generate to push blood forward

• higher pressure requires a thicker muscular wall

what determines the muscular wall thickness of a heart chamber

• left ventricle: thick, cone-shaped; forms the muscular core/apex of the heart (~120 mmHg)

• right ventricle: thinner-walled; wraps around the LV like a “hip pocket on a pair of trousers” (~27 mmHg)

describe the shape, wall thickness, and peak pressure of the left ventricle vs. right ventricle

• mitral (bicuspid) valve: left side (between left atrium and left ventricle)

• tricuspid valve: right side (between right atrium and right ventricle)

what are the two inlet (atrioventricular) valves of the heart, and where are they located

• made up of 2 or 3 flat fibrous flaps (cusps)

• free edges are tethered by chordae tendineae (tendinous cords)

• function: the cords prevent the flaps from ballooning or prolapsing backward into the atrium during ventricular contraction (systole) — functioning like parachute lines holding air

describe the structure of AV valves and how chordae tendineae prevent backflow

• filling (diastole): open passively as blood pushes through them into the ventricle

• contraction (systole): close when ventricular pressure rises above atrial pressure to prevent regurgitation

how do inlet (AV) valves operate during filling vs. ventricular contraction

• valves: aortic valve (left) and pulmonary valve (right)

• location: sit at the ventricular outlets leading into the great arteries

• structure/mechanisms: consist of 3 pocket-shaped cusps, consist of 3 pocket-shaped cusps, they gain strength from their 3D “pocket” shape when filled with blood rather than relying on chordae tendineae

what are the outlet (semilunar) valves, where are they located, and how do they function without tendinous cords

• open (ejection): opens passively when ventricular pressure exceeds arterial pressure

• close: closes when blood tries to flow backward into the ventricle, filling the 3D pockets and pushing the cusp edges tightly together

what causes the semilunar (outlet) valves to open and close

located in the aorta, immediately downstream (distal) to the aortic valve cusps

where are the openings (ostia) of the coronary arteries located in relation to the heart valves

• LV: forms a hollow cone that acts as the core of the heart

• RV: sits alongside and wraps around the LV

describe the shape and spatial relationship of the left ventricle (LV) vs. right ventricle (RV)

• inlet opening: large/wide (allows low-pressure filling)

• outlet opening: small/narrow (allows high-pressure ejection)

• blood pathway: V-shaped (blood enters the wide inlet, sweeps around, and exits through the adjacent narrow outlet)

how are ventricular openings size-divided, and what path does blood take through each ventricle

1. tricuspid

2. aortic

3. pulmonary

4. mitral

what is the order of heart valves arranged around the ventricular openings when viewed from above