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Transcript of ELAINE N. MARIEB EIGHTH EDITION 11 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin...
ELAINE N. MARIEB
EIGHTH EDITION
11
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
PowerPoint® Lecture Slide Presentation by Jerry L. Cook, Sam Houston University
ESSENTIALSOF HUMANANATOMY
& PHYSIOLOGY
PART A
The Cardiovascular System
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
The Cardiovascular System A closed system of the heart and blood
vessels
The heart pumps blood
Blood vessels allow blood to circulate to all parts of the body
The function of the cardiovascular system is to deliver oxygen and nutrients and to remove carbon dioxide and other waste products
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
The Heart Location
Thorax between the lungs
Pointed apex directed toward left hip & rests on diaphragm
Base from which great vessels emerge points toward right shoulder & lies beneath 2nd rib
About the size of your fist
Less than 1 pound
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The Heart
Figure 11.1
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The Heart: Coverings Pericardium – a double serous membrane
Visceral pericardium (epicardium)
Next to heart; part of heart wall
Parietal pericardium
Outside layer
Reinforced by dense connective tissue (fibrous pericardium)
Protects heart
Anchors it to the diaphragm & sternum
Serous fluid fills the space between the layers of pericardium
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
The Heart: Heart Wall Three layers
Epicardium (visceral pericardium)
Outside layer
Continuous with the parietal pericardium
Connective tissue layer
Myocardium
Middle layer
Mostly cardiac muscle
Reinforced internally by dense fibrous connective tissue (“Skeleton of the heart”)
Endocardium
Inner layer
Endothelium lines chambers; continuous w/ vessels entering & leaving heart – helps blood flow smoothly through heart
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External Heart Anatomy
Figure 11.2a
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The Heart: Chambers Right and left side act as separate pumps
Four chambers
2 Atria = Receiving chambers
Right atrium
Left atrium
2 Ventricles = Discharging chambers (Pumps)
Right ventricle
Forms most of heart’s anterior surface; pulmonary circuit pump
Left ventricle
Forms apex; systemic circuit pump
Walls are substantially thicker; more powerful to pump blood throughout body
Figure 11.2c
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The Heart: Chambers
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Pulmonary Circulation Right side = pulmonary circuit pump
Right atria receives deoxygenated blood from the body via the superior and inferior vena cava
Blood flows through the right atrioventricular (AV) valve (tricuspid valve) into the right ventricle
Right ventricle pumps deoxygenated blood out through the pulmonary semilunar valves into the pulmonary trunk that splits into right & left pulmonary arteries, which carry blood to the lungs
Oxygen is picked up & carbon dioxide is unloaded
Oxygen-rich blood is returned to the left atria via 4 pulmonary veins
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Systemic Circulation Left side = systemic circuit pump
Blood flows from the left atria through the left atrioventricular (AV) valve (bicuspid,or mitral valve) into the left ventricle
Left ventricle pumps oxygenated blood out through the aortic semilunar valves into the aorta from which the systemic arteries branch to supply body tissues
From left ventricle to the aorta to arteries to arterioles to capillaries to venules to veins to the vena cava to the right atrium
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Blood Circulation
Figure 11.3
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The Heart: Valves Allow blood to flow in only one direction
Four valves Atrioventricular valves between atria and ventricles prevent
backflow into atria when ventricles contract – hang limply when heart is relaxed
Bicuspid or mitral valve (left)
2 flaps, or cusps, of endocardium
Tricuspid valve (right)
3 flaps
Semilunar valves between ventricle and artery with 3 leaflets that fit tightly together when closed
Pulmonary semilunar valve
Aortic semilunar valve
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The Heart: Valves Valves open as blood is pumped through
Held in place by chordae tendineae (“heart strings”)
Close to prevent backflow
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Operation of Heart Valves
Figure 11.4
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The Heart: Associated Great Vessels Aorta
Leaves left ventricle
Pulmonary arteries
Leave right ventricle
Vena cava
Enters right atrium
Pulmonary veins (four)
Enter left atrium
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Coronary Circulation Blood in the heart chambers does not nourish
the myocardium
The heart has its own nourishing circulatory system
Coronary arteries branch from base of aorta encircling heart in coronary sulcus (AV groove)
Cardiac veins empty into the coronary sinus on the back side of the heart which empties into the right atrium
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The Heart: Conduction System Intrinsic conduction system
(nodal system)
Heart muscle cells contract, without nerve impulses, in a regular, continuous way
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The Heart: Conduction System Special tissue sets the pace
Sinoatrial node
In right atrium
Pacemaker
Atrioventricular node
At junction of the atria & ventricles
Atrioventricular bundle
a.k.a. bundle of His
Bundle branches
Right & left located in the interventricular septum
Purkinje fibers
Spread within muscles of ventricle walls
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Heart Contractions Contraction is initiated by the sinoatrial node
Sequential stimulation occurs at other autorhythmic cells
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Heart Contractions
Figure 11.5
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Filling of Heart Chambers – the Cardiac Cycle = one complete heartbeat
Figure 11.6
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The Heart: Cardiac Cycle Average heart beats 75 times/minute, so
cardiac cycle = 0.8 seconds
Atria contract simultaneously
Atria relax, then ventricles contract starting at the apex and moving toward the atria
Systole = contraction
Diastole = relaxation
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The Heart: Cardiac Cycle Cardiac cycle – events of one complete heart
beat
Mid-to-late diastole – blood flows into ventricles
Ventricular systole – blood pressure builds before ventricle contracts, pushing out blood; atria are relaxed & filling again
Early diastole – atria finish re-filling, ventricular pressure is low
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Heart Sounds When using a stethoscope, 2 distinct sounds
“Lub”
Caused by the closing of the AV valves
Longer and louder
“Dup” or “dub”
Occurs when the semilunar valves close at the end of systole
Short and sharp
Lub-dup, pause, lub-dup, pause, and so on
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The Heart: Cardiac Output Cardiac output (CO)
Amount of blood pumped out by each side of the heart in one minute (ventricles)
CO = (heart rate [HR]) x (stroke volume [SV])
Stroke volume
Volume of blood pumped by each ventricle in one contraction
Average adult CO = 75 beats/min. X 70 ml/min. = 5250ml/min.
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Cardiac Output Regulation
Figure 11.7
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The Heart: Regulation of Heart Rate Stroke volume usually remains relatively
constant
Starling’s law of the heart – the more that the cardiac muscle is stretched, the stronger the contraction
Changing heart rate is the most common way to change cardiac output
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The Heart: Regulation of Heart Rate Increased heart rate
Sympathetic nervous system
Crisis
Low blood pressure
Hormones
Epinephrine
Thyroxine
Exercise
Decreased blood volume
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The Heart: Regulation of Heart Rate Decreased heart rate
Parasympathetic nervous system
High blood pressure or blood volume
Decreased venous return
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Blood Vessels: The Vascular System Taking blood to the tissues and back
Arteries
Arterioles
Capillaries
Venules
Veins
Figure 11.8a
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The Vascular System
Figure 11.8b
Vessels have 3 layers or tunics
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Differences Between Blood Vessel Types Walls of arteries are the thickest
Lumens of veins are larger
Larger veins have valves that prevent backflow of blood
Skeletal muscle “milks” blood in veins toward the heart
Walls of capillaries are only one cell layer thick to allow for exchanges between blood and tissue
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Movement of Blood Through Vessels Most arterial blood is
pumped by the heart
Veins use the milking action of muscles to help move blood
Figure 11.9
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Capillary Exchange Substances exchanged due to concentration
gradients
Oxygen and nutrients leave the blood
Carbon dioxide and other wastes leave the cells
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Capillary Exchange: Mechanisms Direct diffusion across plasma membranes
Endocytosis or exocytosis
Some capillaries have gaps (intercellular clefts)
Plasma membrane not joined by tight junctions
Fenestrations of some capillaries
Fenestrations = pores
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Diffusion at Capillary Beds
Figure 11.20
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Special Circulations: Hepatic Portal Circulation Veins of the hepatic portal circulation drain
the digestive organs, spleen and pancreas and deliver this blood to the liver via hepatic portal vein
Liver processes glucose, fat and protein before they enter the systemic circulation
Some nutrients are removed to be stored for later release to the blood
Veins feed the liver circulation
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Hepatic Portal Circulation
Figure 11.14
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Special Circulations: Circulation to the Fetus Lungs and digestive system are not functional
All nutrient, excretory and gas exchanges occur through the placenta
Umbilical cord contains 3 blood vessels
1 large umbilical vein
Carries nutrients and oxygen to the fetus
2 smaller umbilical arteries
Carries carbon dioxide and waste from fetus to placenta
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Circulation to the Fetus As blood flows to the fetal heart, most of it bypasses the
immature liver via the ductus venosus and enters the inferior vena cava and is carried to the right atrium
Since lungs are nonfunctional, 2 shunts bypass them
Blood entering right atrium is shunted into the left atrium via foramen ovale, an opening in the interatrial septum
Blood that enters the right ventricle is pumped out the pulmonary trunk and shunted into the ductus arteriosus, which connects it to the aorta
Aorta carries blood to fetal tissues and ultimately back to the placenta via the umbilical arteries
Shortly after birth, the foramen ovale closes and the ductus arteriosus collapses and is converted to the ligamentum arteriosum
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Circulation to the Fetus
Figure 11.15
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Developmental Aspects of the Cardiovascular System A simple “tube heart” develops in the embryo
and pumps by the fourth week
The heart becomes a four-chambered organ by the end of seven weeks
Few structural changes occur after the seventh week
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Pulse Pulse – pressure
wave of blood
Monitored at “pressure points” where pulse is easily palpated
Resting pulse averages 70-76 beats/min
Figure 11.16
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Blood Pressure Measurements by health professionals are
made on the pressure in large arteries
Systolic – pressure at the peak of ventricular contraction
Diastolic – pressure when ventricles relax
Pressure in blood vessels decreases as the distance away from the heart increases
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Measuring Arterial Blood Pressure
Figure 11.18
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsFigure 11.17
Comparison of Blood Pressures in Different Vessels
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Blood Pressure: Effects of Factors Neural factors
Autonomic nervous system adjustments (sympathetic division) cause vasoconstriction, which increases BP
Renal factors
Regulation by altering blood volume
Allowing more water to leave as urine, lowers BP
Retaining water raises BP
Renin – hormonal control – raises BP (vasoconstriction)
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Blood Pressure: Effects of Factors Temperature
Heat has a vasodilation effect
Cold has a vasoconstricting effect
Chemicals
Various substances can cause increases or decreases
Increase BP – epinephrine and nicotine
Decrease BP – alcohol and histamine
Diet
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Factors Determining Blood Pressure
Figure 11.19
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Variations in Blood Pressure Human normal range is variable
Normal
140–110 mm Hg systolic
80–75 mm Hg diastolic
Hypotension (low BP)
Low systolic (below 100 mm HG)
Often associated with long life and an old age free of illness
Chronic hypotension may hint at poor nutrition
Hypertension
High systolic (above 140 mm HG)
Can be dangerous if it is chronic