CVPR 03-24-14 08-09am Overview CV Anatomy - Proenza Flashcards
The functions of the cardiovascular system
- Distributes dissolved gases & nutrients.
- Removes metabolic waste
- Contributes to systemic homeostasis by controlling temp, O2 & nutrient supply, pH, ionic composition.
- Quickly adapts to changes in conditions and metabolic demands
Three parts of the cardiovascular system
- Heart (pump)
- Blood (transportation)
- Vasculature (including lymphatic system) (pipes).
Lt vs Rt Heart Side pumps to…
Left side of heart pumps blood to system circulation. Right side pumps to pulmonary circulation.
“In Series” arrangement of circulatory system
The primary arrangement of cardiac/pulmonary circulatory system. No direct connection between right and left (septum separates sides). Output of left and right sides of heart must be closely matched.
Pulmonary circulation vs. System circulation
A. Pulmonary: low pressure, single pathway between heart and lungs (“series”).
B. Systemic: higher pressure, multiple pathways from heart to different systemic vascular beds (“parallel”).
“In Parallel” arrangement of circulatory system … where occurs
The primary arrangement of SYSTEMIC circulation.
Importance of “parallel” arrangement of systemic circulation
- Oxygenated blood visits only one organ system before returning to pulmonary circulation.
- Changes in metabolic demand or blood flow in one organ do not significantly affect other organs.
- Blood flow to different organs can be individually varied to match demand.
Changes in blood flow to different organs during rest vs exercise
- At rest, most blood is directed to brain (~14%), skeletal muscle (~15%), GI system (21%), and kidney (22%).
- During exercise, up to 80% of blood may be directed to exercising muscle.
Major exception to “in parallel” systemic circulation
Hepatic circulation — large fraction of hepatic blood supply is via intestinal circulation
Layers of the heart wall
Outside to inside:
- Epicardium
- Myocardium
- Endocardium
Epicardium defn.
Outer membrane of the heart wall; Connective tissue & fat
Myocardium defn.
Thick middle muscle layer of the heart wall
Endocardium defn.
Inner membrane of the heart wall; Made of endothelial cells, as in vessels
Pericardium defn.
Fluid-filled membranous sac enclosing entire heart — Not connected to walls of heart — Stiff & non-compliant, resists sudden distension of chambers
Layers of pericardium
Fibrous layer (outer), Parietal pericardium, [Pericardial fluid], Visceral pericardium (inner)
Pericarditis
Inflammation of the pericardium –> restricts filling of the heart
Chambers of the heart (4)
Ventricles (left and right) = the main pumping chambers; separated from each other by interventricular septum………
Atria (left and right) = small “primer” chambers to supply the ventricles with blood; thinner walled.; separated from each other by interatrial septum
Left vs. Right Ventricles
Left ventricle supplies higher pressure systemic circulation, so is bigger with thicker walls than the right ventricle. The left ventricle does more work, uses more O2 than the right.
Vessels of the Heart (4)
- Vena cavae –> inlet to rt. atrium from body
- Pulmonary artery –> outlet from rt. ventricle to lungs
- Pulmonary vein –> inlet to lt. atrium from lungs
- Aorta –> outlet from lt. ventricle to body
Vena cavae
Superior vena cava & inferior vena cava; Inlet vessels into the right atrium
Pulmonary artery
Outlet vessel from right ventricle [Arteries go Away from the heart]…odd for an artery b/c it carries DEoxygenated blood
Pulmonary vein
Inlet vessel into left atrium
Aorta
Outlet from left ventricle; Main blood supply to body; Garden-hose sized, ~1” in diameter
Valves defn.
Thin flaps (“cusps”) of fibrous tissue covered by endothelium........... *Mitral valve has two cusps (bicuspid); the others have three.
Valves of the Heart (4)
- Tricuspid valve (btwn rt atrium & rt ventricle) …….2. Pulmonic valve (btwn rt ventricle & pulmonary artery)……. 3. Mitral valve (btwn lt atrium & lt ventricle)…….4. Aortic valve (btwn left ventricle & aorta)
Arrangement of heart valves
Arranged in two sets: Atrioventricular (Tricuspid & Mitral) and Semilunar (Pulmonic & Aortic); All are in the same horizontal plane in the heart
Atrioventricular valves – members, location, characteristics
Tricuspid & Mitral valves; Between atria and ventricles; Attached to papillary muscles in ventricles by chordae tendonae
Chordae tendonae
Tendon-like attachments that prevent atrioventricular valves from prolapsing into atria during ventricular contraction
Semilunar valves – members & location
Pulmonic & aortic valves; Between ventricles & great arteries
Valves of the heart – how they work & purpose
One-way, pressure-operated (i.e. passive); Direct blood flow, prevent backward blood flow
Heart sounds generation & Valve defects
Heart sounds are generated by opening & closing valves; Defective valves make unusual sounds (murmurs); Regurgitation is a minor valve leakage; Prolapse is a major valve failure, where valve gets pushed backward.
Apex vs. Base of the Heart
Apex = tip of left ventricle; Base = posterior surface
Coronary blood flow – Effects of Diastole vs. Systole, & Heart Rate
Most coronary blood flow occurs during diastole, b/c of compression of microvasculature during systole.
Flow thus depends on heart rate (less time for perfusion at higher heart rates).
Angina
Heart has high oxygen consumption; Supply must closely match demand, or results in chest pain (angina)
Right and left coronary arteries – origin, course
Arise from root of aorta; Major coronary arteries course along epicardial surface of heart; Smaller branches enter myocardium; Some variation in anatomy between individuals.
Left main coronary artery – size, bifurcations, what it supplies
Short (~1cm); Bifurcates to left anterior descending (LAD) artery and circumflex artery; Primary blood supply to left heart chambers. [LAD = “widowmaker” = its occlusion is very deadly]
Right coronary artery – location, what it supplies
In groove between right atrium & right ventricle; Primary blood supply to right atrium and right ventricles, as well as part of left ventricle.
Coronary capillaries
Very dense; Each myocyte is associated with several capillaries
Coronary veins
Located adjacent to corresponding coronary arteries; Drain into coronary sinus, which opens into right atrium near inferior vena cava
Blood flow pathway
DEOXYGENATED BLOOD from systemic circulation –> Superior & Inferior vena cava –> (no valve, passive) Right atrium (contracts) –> (tricuspid valve) Right ventricle (contracts) –> (pulmonic valves) pulmonary arteries to lungs –> OXYGENATED BLOOD from lungs into pulmonary veins –> Left atrium (contracts) –> (mitral valve) Left ventricle (contracts) –> (aortic valve) aorta to systemic circulation
3 Parts of the Vascular System
- Arterial system (to distribute oxygenated blood & nutrients)
- Microcirculation & lymphatic system (for diffusion & filtration)
- Venous system (to collect deoxygenated blood & wastes)
Types of vessels (flow & size)
Aorta (~25mm, hose) > Arteries (~0.2-6mm)> Arterioles (~10-70 microns) > Capillaries ( Venules / Veins (~10 microns to 0.5 cm) < Vena cavae (~25-30 mm)
Aorta
Single outlet from left side of heart; Dampens pulsatile pressure
Arteries
Thick walled, resist expansion; distribute blood to different organs
Arterioles
Relatively thicker walls (more vascular smooth muscle); Highly innervated by autonomic nerves, circulating hormones, and local metabolites; Primary site of regulation of vascular resistances, via changes in diameter.
Capillaries
Smallest vessels (walls just a single layer of epithelial cells, with no smooth muscle); ~same size as RBCs, which travel through in single file; Huge total surface area; Primary site of gas & nutrient exchange with interstitial fluid.
Venules/Veins
Thin walls relative to diameter compared to equivalent-size arteries (but still some smooth muscle); Not much elasticity; Primary capacitance vessels of the body (most of blood volume stored there); One-way valves compensate for lower pressure in venous system to ensure blood flow only in correct direction
Resistance vessels – anatomy
Arterial walls have three layers:
- Tunica adventitia (outer CT layer, mostly collagen & elastin)
- Tunica media (middle layer, mostly innervated smooth muscle)
- Tunica intima (inner layer, lined with single layer of vascular endothelium cells)
Tunica media – in which types of vessels, purpose
In all arteries EXCEPT capillaries; Controls diameter of vessels, esp. in resistance arteries
Tunica intima – importance
Very important in regulation of blood flow & signaling; Site of atherosclerotic plaque formation
Microcirculation defn. & vasculature involved
Vasculature from first-order arterioles to venules; Capillaries
Capillaries in microcirculation
Site of gas, nutrient, and waste exchange; Blood flow through determined by pressure gradient and via constriction/dilation of arterioles & precapillary sphincters (no smooth muscle)
Precapillary sphincters
Smooth muscle bands around arterioles at junction of arteriole and capillaries
What drives movement of substances between capillaries and tissue
Concentration gradients
Lymph defn.
Lymph is excess interstitial fluid
Lymphatic capillaries
= blind end capillaries; less numerous than regular capillaries & much more porous (no tight junction in lymph vessels as normal capillaries do); have one-way valves (like veins) so lymph flow is uni-directional
Lymph flow – what drives it
Passive system; Lymph flows into lymphatic capillaries in response to increased interstitial pressure, contraction of smooth muscle in lymph vessels, and contraction of surrounding skeletal muscle.
Lymph flow – direction, path
Uni-directional b/c of one-way valves; Lymph is filtered through lymph nodes (bacteria removed), and rejoins the circulatory system in the subclavian veins.
Lymph flow – amount & d efects
Lymph flow ~2-4 L per day (vs ~7000 L blood flood per day); Edema occurs when interstitial fluid exceeds capacity of lymphatic system.
Cardiac conduction system -Contraction/Beating of the Heart – what makes it happen
Initiated & coordinated by specialized cells by conducting electrical impulses
Sinoatrial (SA) node
In wall of rt. atrium; Spontaneously depolarizes to initiate heart beat; Intrinsic activity ~100 bpm; Highly regulated by autonomic nervous system and many humoral factors; “natural pacemaker”
Spread of impulses from SA node
Impulse spreads through atria via gap junctions between myocardiocytes
Atrioventricular (AV) node
Between atria and ventricles; Slows conduction to allow atrial contraction to occur before ventricular contraction
His-Purkinje system
Specialized cells that rapidly conduct depolarization to trigger coordinated ventricular contraction (increase speed of conduction)
