Charles C. Cook, MD

Basics of the Human BodyEnergy is the currency of the bodyThe body will do what it can to save energy

LubricationValvesDiffusionSesamoid bones (patella) Etc

Basics of the Human BodyThroughout medicine there is a recurring

theme and hopefully the different physiological events we will see will lend some method to the madness.

Now that all your hearts are beating faster with anticipation lets dive into cardio & try to understand why that is happening.

Function of the Cardiovascular System

The ultimate goal of the cardiovascular system is to ensure that all tissues are adequately perfused.**

If tissue is not adequately perfused it cannot perform at peak performance, heal, and if stressed long enough will die.

CV DiseaseLeading cause of death in U.S.About 2600 people die every day of

cardiovascular disease. (2x that of cancer)Coronary artery disease (CAD) most common.There are accidents……..

Risk Factors for CVD Major:

Hypertension (HTN)Elevated cholesterol

>200mg./dl LDL—”bad cholesterol” HDL—”good cholesterol”

Risk Factors for CVD Major:

Diabetes Esp. Type II (adult onset) One of fastest growing diseases in U.S. due to

unchecked obesity Certain ethnic groups @ increased risk:

Blacks, Hispanics, Asian & Pacific Islanders, and Native Americans.

Risk Factors for CVD Major

ObesitySmokingInactivityGender ???

Women catching up with men If CVD present mortality higher in women

And the #1 reason for CVD if you sort through the pharmacology commercials……BAD GENETICS

Cardiopulmonary developmentHeart is first functional organ (day 22)Lung development begins at about 6 weeks24 weeks - begin to secrete surfactant25-28 weeks - sufficient surfactant26 weeks - start of alveolarizationLungs don’t function until birth*Fetus potentially viable @ 24-26 wks

Cardiopulmonary developmentSo what?Since the lungs do not function in the

developing fetus we need some kind of mechanism to deliver oxygenated blood to the left side of the heart.

Fetal circulationUmbilical vein from placenta to liverDuctus venosus to IVCRight atriumForamen Ovale connects right atrium to left

atriumDuctus arteriosusUmbilical arteries (2)

Quick ReviewGases and liquids go down the hill of

resistance and pressure.The cardiovascular system is a closed system.

If something happens in a closed system it affects the entire system

Occlusion of placental flow causes pressure drop in IVC and right atrium

Aeration of lungs results in increased pulmonary flow

Increased flow raises pressure in left atrium, also closure of umbilical arteries increases systemic pressure

Pressure gradient closes foramen ovale

www.indiana.edu/~anat550/cvanim/fetcirc/fetcirc.html

The heart

Anatomy of the heart

Cone shaped muscle; fist sizeIn mediastinum bordered by lungs,

vertebrae, and sternumBase at 2nd rib, apex 5th intercostal

space

Anatomy of the heart

Pericardium - encloses and holds heart. Is comprised of a fibrous bag surrounding a delicate double layer of serous membrane.

Anatomy of the heart

The tough outer bag is the fibrous pericardium

Attached to the great vessels and the diaphragm

It is a tough, inelastic connective tissue

Anatomy of the heart

The Serous PericardiumA delicate double layer of serous

membrane Parietal pericardium lines the inside

of the fibrous pericardiumVisceral pericardium - covers the

surface of the heart

Anatomy of the heart

Pericardial cavityA space between the parietal and

visceral pericardiumContains a small amount of fluid

that lubricates and reduces energy demands

Anatomy of the heartThe walls of the heart

Epicardium - the outer covering of the heart (i.e.. VISCERAL PERICARDIUM; location is the only difference)

Myocardium - middle layer - cardiac muscle tissue

Endocardium - inner layer of epithelium and connective tissue

Anatomy of the heartThe chambers of the heart

The 2 upper chambers are the ATRIAThe receiving chambersRight atrium receives deoxygenated

blood from body tissuesLeft atrium receives oxygenated

blood from lungs

Anatomy of the heart

Atria (continued)The interatrial septum divides the

two atriaContains a depression - the fossa

ovalis

Anatomy of the heartCardiac skeleton

A ring of connective tissue that encircles the valves

It electrically isolates the atria from the ventricles

Anatomy of the heartThe chambers of the heart

The two lower chambers are called ventricles

These are the pumping chambersRight ventricle pumps blood to the

lungsLeft ventricle pumps blood to the

body tissues

Anatomy of the heart

Ventricles (continued)The interventricular septum

divides the two ventriclesVentricular septal defects occur

high at the fibrous portion.

Anatomy of the heartPurpose of valves:

Keep blood flowing in only one direction.Why?

Anatomy of the heartValves of the heart

Atrioventricular (AV) valves assure that blood flows in one direction; from atrium to ventricle

Tricuspid valve - lies between right atrium and right ventricle

Anatomy of the heartValves (continued)

Mitral (bicuspid) valve - lies between left atrium and left ventricle

Chordae tendinae - strong fibrous strings that attach cusps of AV valves to heart wall. Why?

Anatomy of the heartHeart murmurs

Caused by turbulent flowStenosis - narrowing of aperture (partial

obstruction)Regurgitation - valve fails to close completely

& allows backflow.Why is stenosis and regurgitation bad?

MINI CLINIMitral stenosis

Which chamber has to work harder?Being a closed system, as the blood backs up

where will it start to accumulate & what would you see on PE?

More work/energy is being performed/expended with less positive results.

MINI CLINIMitral regurgitation

What chamber(s) is/are being over-loaded?What happens to muscle that works harder?What happens to the volumes in the L atrium?What would you find on PE

Anatomy of the heart

Valves (continued)Semilunar valves - lie between

ventricles and the large arteries that carry blood away from the heart

Anatomy of the heartSemilunar valves (continued)

Pulmonary semilunar valve - between right ventricle and pulmonary trunk

Aortic semilunar valve - between left ventricle and aorta

Both assure that blood pumped out does not reenter the ventricle

Anatomy of the heart

Blood flow of the heart (Coronary circulation)Coronary arteries arise from aortaCardiac veins Coronary sinusR atrium

Anatomy of the heartCoronary arteries

Arise just above the aortic valve leafletsThe ascending aorta is stretched as the left

ventricle pumps blood into itThe elasticity of the aorta causes blood to be

pumped into the coronary arteries when the aortic valve closes

Anatomy of the heartLeft coronary artery

Anterior descending (LAD)L Circumflex

Right coronary arteryGoes to right around sulcusEnds as posterior descending

Anatomy of the heartCardiac veinsCoronary sinusThebesian veins

Empty into all chambers“anatomical shunt”

The Vascular System

The Vascular System

Blood flow through the heartRt atrium receives blood from SVC, IVC,

coronary sinusTricuspid valveRt ventriclePulmonary semilunar valve(start of pulmonary circuit)Pulmonary trunk

The Vascular SystemBlood flow through the heart

Pulmonary arteriesLung capillariesPulmonary veinsLeft atriumBicuspid (mitral) valve

The Vascular SystemBlood flow through the heart

Left ventricleAortic semilunar valveAorta(Systemic circuit)

Systemic VasculatureArteries - carry blood away from

the heart“conductance vessels”

Arterioles - smallest arteries“resistance vessels”

Systemic Vasculature

Capillaries - smallest vessels“exchange vessels”

Venules - collect blood from capillariesVeins - carry blood toward the heart

“capacitance vessels”

Determinants of Blood PressureCardiac outputVascular resistance

Control of cardiovascular systemIntegrated control of the heart and the

vascular systemA. Can change capacity of blood vessels

OrB. Can change cardiac output

Or both

Control of cardiovascular systemLocal “intrinsic” controlCentral “extrinsic” control

Regulation of peripheral vasculatureLocal control can be myogenic or

metabolicMyogenic refers to muscle response to

pressure changesMetabolic responses include reaction to

changes in carbon dioxide, oxygen, pH changes, histamines, etc.

Brain more sensitive to metabolites while heart is sensitive to both myogenic and metabolic changes

Regulation of peripheral vasculatureCentral control is achieved mainly by the

sympathetic nervous system

Regulation of cardiac outputPrinciple index of cardiac performancevolume pumped by one ventricle in one

minuteCO=HR X SVApprox 5 liters at rest (>20-35)

Regulation of cardiac outputCardiac output can be changed by changing

stroke volume Or

Changing heart rateOr

Changing both

Regulation of cardiac outputSV=EDV-ESVEDV at rest about 120 mlESV at rest about 50 ml at restSV=120-50If HR = 70, then CO= ??

Regulation of cardiac outputDuring exercise

EDV increases up to 250 mlESV drops to as low as 10 mlTherefore SV could more than triple

Regulation of cardiac output Changes in heart rate

Extrinsic controlSympathetic system (“accelerator”)

Increases heart rateParasympathetic system (“brakes”)

Decreases heart rateHormones from adrenal medulla have same

effect as sympathetic stimulation

Regulation of cardiac output Changes in heart rate

Intrinsic controlBainbridge (atrial) reflex

increase return -- increase heart rate due to stretching of atrial wall Practice with each other by inhaling deeply, lying

down, or raising your legs.

Cardiovascular control mechanismsAchieved by integrating local and central

mechanisms that affect both heart and vasculature

Cardiovascular control mechanismsMostly involves local (intrinsic) controlCentral (extrinsic) control relies upon

Vasomotor centers and cardiac centers in the brainstem

Peripheral receptors in aortic arch and carotid sinus

Cardiovascular control mechanismsBrainstem centers

Vasomotor areaCardioacceleratory centerCardioinhibitory center

There is interaction between cardiac and vasomotor centers

Cardiovascular control mechanismsPeripheral receptors

Baroreceptors High pressure in aortic and carotid bodies Low pressure in atria and large thoracic veins

Chemoreceptors Respond to chemical change in blood Effect is vasoconstriction & increased heart rate

Responses to volume change10% loss – increased sympathetic stimuli to

sinus node and increased ADH20% - same as above but increased vascular

tone in capacitance vessels30% - significant increase in tone plus

massive vasoconstriction in peripheral vessels

Application TimeWhen does blood flow through cardiac

muscle?Circulating humoral agentsSystemic vascular resistanceWhat does it mean to say a fetus is

potentially viable?Vasomotor tone

Questions???