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Chapter 11
Anatomy of the Heart
-Approximately the size of a persons fist, weighs less than a pound
-Found within the bony thorax and lungs are found on either side.
-Apex-Base-PericardiumVisceral pericardium (epicardium)Parietal pericardium-Heart walls are composed of three layers; epicardium, myocardium,
endocardium
EpicardiumMyocardiumEndocardium-Four Chambers- two atria and two ventricles
AtriaVentricles-
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-Right atria-Right ventricle-Left atria-Left Ventricle-Valves- there are four heart valves, allow for one way movement only
Atrioventricular (AV) valves-Mitral or Bicuspid valve-TricuspidSemilunar valves-Pulmonary valve-Aortic valve-
Cardiac Circulation
Coronary arteriesCardiac veins-
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Physiology of the Heart
-Heart muscle tissue can contract independently of nervous system control.
-Regulated by two “controlling systems”:
Autonomic Nervous SystemIntrinsic conduction system (nodal system)-sinoatrial (SA) node-atrioventricular (AV) node-AV bundle, bundle branches, purkinje fibers-
Cardiac Cycle and Heart Sounds
SystoleDiastoleCardiac cycleMid-to-late diastoleVentricular systoleEarly diastoleHeart Sounds
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Cardiac Output- amount of blood pumped out by each side of the heart (ventricles) in
one minute.
-It is the product of the heart rate and the stroke volume HR x SV = CO
Stroke VolumeExample:
Regulation of Stroke Volume
-a healthy heart pumps out about 60% of the blood present in its ventricles (70ml)
-the more the heart muscles are stretched just before contract, the stronger the
contraction will be.
-venous return accounts for how much blood reaches the ventricles for possible
stretching.
Regulation of Heart Rate
-when stroke volume declines, cardiac output is maintained by a faster heartbeat.
-The ANS is the most important external influence on heart rate activity.
Sympathetic activationParasympathetic activation-hormones, chemicals, and drugs can also modify the heart rate
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Blood Vessels
Arteries-
Arterioles-
Capillary beds-
Venules-
Veins-
Structure of Vessels:
Tunica intima-
Tunica media-
Tunica externa-
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Differences between arteries, veins, and capillaries.
-Arteries tend to have a thicker tunica media, to deal with the constant change in
blood pulsing through them. Closer to the heart.
-Veins have thinner walls, blood pressure is relatively low at all time, further from
the heart.
-Capillaries contain just the tunica interna, form a network called a capillary bed.
-Contain two types of vessels;
Vascular shuntTrue capillariesPrecapillary sphincter-
Gross anatomy of blood vessels
Vessel List
Special Circulations-Brain
Special Circulation-Hepatic Portal
Special Circulation-Fetal Circulation
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Physiology of Circulation
Arterial Pulse-
Blood Pressure-
-usually refers to the large systemic arteries near the heart
-blood flows in a pressure gradient, from high pressure to low pressure
-valves, milking, help keep blood in veins from backflow and continuation on to
the heart
-cut an artery, blood spurts, cut a vein, blood flows evenly
-elasticity and recoil of arteries is vital for continual blood flow
Measuring blood pressure
Systolic pressureDiastolic pressure-Measured in mm of Hg (mercury), written with systolic over diastolic 120/80
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Effects of various factors on blood pressure
-Cardiac Output, already discussed
-Peripheral Resistance- amount of friction between blood and walls of blood vessels
-Constriction of blood vessels (sympathetic NS or atherosclerosis)
-Increased blood volume
-Increase blood viscosity
-Any increase in CO or PR will cause blood pressure to increase.
Neural Factors:
Renal Factors:
Temperature:
Chemicals:
Diet:
Variations in Blood Pressure
-“Normal” BP rages from 110-140 over 75-80
-Age, weight, mood, race, physical activity, and posture all effect blood pressure
-Hypotension-Hypertension8
Capillary Exchange
-substances tend to move to and from cells according to their concentration gradients
-substances exchanged first diffuse through interstitial fluid, then take one of four
routes across the plasma membranes of capillary epithelial cells:
-Blood and osmotic pressure play a role in bulk movement of fluid into and out of
capillaries.
-blood pressure is higher at the arteriole end, net movement out toward cells
-osmotic pressure is higher at the venule end, net movement into vessel.
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Developmental Aspects
-embryonic heart begins pumping at four weeks, completely formed by 7 weeks
-congenital heart defects account for half of infant death of all congenital defects.
Maternal infections, drugs during first 3 months
-heart can become stronger and more efficient with regular (3-4 times a week) aerobic
exercise.
-aging brings weaker venous valves, progressive atherosclerosis
-diet more than age effects health of heart.
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