Download Cardiovascular System

Charles C. Cook, MD
Basics of the Human Body
 Energy is the currency of the body
 The body will do what it can to save energy
 Lubrication
 Valves
 Diffusion
 Sesamoid bones (patella)
 Etc
Basics of the Human Body
 Throughout 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 Disease
 Leading 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
 Obesity
 Smoking
 Inactivity
 Gender ???


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 development
 Heart is first functional organ (day 22)
 Lung development begins at about 6 weeks
 24 weeks - begin to secrete surfactant
 25-28 weeks - sufficient surfactant
 26 weeks - start of alveolarization
 Lungs don’t function until birth*
 Fetus potentially viable @ 24-26 wks
Cardiopulmonary development
 So 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 circulation
 Umbilical vein from placenta to liver
 Ductus venosus to IVC
 Right atrium
 Foramen Ovale connects right atrium to left atrium
 Ductus arteriosus
 Umbilical arteries (2)
Quick Review
 Gases 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
Changes at birth
 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.ht
ml
The heart
Anatomy of the heart
 Cone shaped muscle; fist size
 In mediastinum bordered by lungs,
vertebrae, and sternum
 Base 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 Pericardium
 A delicate double layer of serous membrane
 Parietal pericardium lines the inside of the
fibrous pericardium
 Visceral pericardium - covers the surface of
the heart
Anatomy of the heart
 Pericardial cavity
 A space between the parietal and visceral
pericardium
 Contains a small amount of fluid that
lubricates and reduces energy demands
Anatomy of the heart
 The 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 heart
 The chambers of the heart
 The 2 upper chambers are the ATRIA
 The receiving chambers
 Right atrium receives deoxygenated blood
from body tissues
 Left atrium receives oxygenated blood from
lungs
Anatomy of the heart
 Atria (continued)
 The interatrial septum divides the two
atria
 Contains a depression - the fossa ovalis
Anatomy of the heart
 Cardiac skeleton
 A ring of connective tissue that encircles the valves
 It electrically isolates the atria from the ventricles
Anatomy of the heart
 The chambers of the heart
 The two lower chambers are called
ventricles
 These are the pumping chambers
 Right ventricle pumps blood to the lungs
 Left ventricle pumps blood to the body
tissues
Anatomy of the heart
 Ventricles (continued)
 The interventricular septum divides the
two ventricles
 Ventricular septal defects occur high at
the fibrous portion.
Anatomy of the heart
 Purpose of valves:
 Keep blood flowing in only one direction.
 Why?
Anatomy of the heart
 Valves 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 heart
 Valves (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 heart
 Heart murmurs
 Caused by turbulent flow
 Stenosis - narrowing of aperture (partial obstruction)
 Regurgitation - valve fails to close completely & allows
backflow.
 Why is stenosis and regurgitation bad?
MINI CLINI
 Mitral 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 CLINI
 Mitral 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 heart
 Semilunar 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 aorta
 Cardiac veins
 Coronary sinus
 R atrium
Anatomy of the heart
 Coronary arteries
 Arise just above the aortic valve leaflets
 The ascending aorta is stretched as the left ventricle
pumps blood into it
 The elasticity of the aorta causes blood to be pumped
into the coronary arteries when the aortic valve closes
Anatomy of the heart
 Left coronary artery
 Anterior descending (LAD)
 L Circumflex
 Right coronary artery
 Goes to right around sulcus
 Ends as posterior descending
Anatomy of the heart
 Cardiac veins
 Coronary sinus
 Thebesian veins
 Empty into all chambers
 “anatomical shunt”
The Vascular System
The Vascular System
 Blood flow through the heart
 Rt atrium receives blood from SVC, IVC, coronary
sinus
 Tricuspid valve
 Rt ventricle
 Pulmonary semilunar valve
 (start of pulmonary circuit)
 Pulmonary trunk
The Vascular System
 Blood flow through the heart
 Pulmonary arteries
 Lung capillaries
 Pulmonary veins
 Left atrium
 Bicuspid (mitral) valve
The Vascular System
 Blood flow through the heart
 Left ventricle
 Aortic semilunar valve
 Aorta
 (Systemic circuit)
Systemic Vasculature
 Arteries - carry blood away from the heart
 “conductance vessels”
 Arterioles - smallest arteries
 “resistance vessels”
Systemic Vasculature
 Capillaries - smallest vessels
 “exchange vessels”
 Venules - collect blood from capillaries
 Veins - carry blood toward the heart
 “capacitance vessels”
Determinants of Blood Pressure
 Cardiac output
 Vascular resistance
Control of cardiovascular system
 Integrated control of the heart and the vascular system
 A. Can change capacity of blood vessels
 Or
 B. Can change cardiac output
 Or both
Control of cardiovascular system
 Local “intrinsic” control
 Central “extrinsic” control
Regulation of peripheral
vasculature
 Local control can be myogenic or metabolic
 Myogenic refers to muscle response to pressure changes
 Metabolic 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
vasculature
 Central control is achieved mainly by the sympathetic
nervous system
Regulation of cardiac output
 Principle index of cardiac performance
 volume pumped by one ventricle in one minute
 CO=HR X SV
 Approx 5 liters at rest (>20-35)
Regulation of cardiac output
 Cardiac output can be changed by changing stroke
volume
 Or
 Changing heart rate
 Or
 Changing both
Regulation of cardiac output
 SV=EDV-ESV




EDV at rest about 120 ml
ESV at rest about 50 ml at rest
SV=120-50
If HR = 70, then CO= ??
Regulation of cardiac output
 During exercise
 EDV increases up to 250 ml
 ESV drops to as low as 10 ml
 Therefore SV could more than triple
Regulation of cardiac output
Changes in heart rate
 Extrinsic control
 Sympathetic system (“accelerator”)

Increases heart rate
 Parasympathetic system (“brakes”)

Decreases heart rate
 Hormones from adrenal medulla have same effect as
sympathetic stimulation
Regulation of cardiac output
Changes in heart rate
 Intrinsic control
 Bainbridge (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 mechanisms
 Achieved by integrating local and central mechanisms
that affect both heart and vasculature
Cardiovascular control mechanisms
 Mostly involves local (intrinsic) control
 Central (extrinsic) control relies upon
 Vasomotor centers and cardiac centers in the brainstem
 Peripheral receptors in aortic arch and carotid sinus
Cardiovascular control mechanisms
 Brainstem centers
 Vasomotor area
 Cardioacceleratory center
 Cardioinhibitory center
 There is interaction between cardiac and vasomotor
centers
Cardiovascular control mechanisms
 Peripheral 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 change
 10% loss – increased sympathetic stimuli to sinus node
and increased ADH
 20% - same as above but increased vascular tone in
capacitance vessels
 30% - significant increase in tone plus massive
vasoconstriction in peripheral vessels
Application Time
 When does blood flow through cardiac muscle?
 Circulating humoral agents
 Systemic vascular resistance
 What does it mean to say a fetus is potentially viable?
 Vasomotor tone
Questions???