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


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


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


The Heart

Figure 11.1


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


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


External Heart Anatomy

Figure 11.2a


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


The Heart: Chambers


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


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


Blood Circulation

Figure 11.3


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


The Heart: Valves Valves open as blood is pumped through

Held in place by chordae tendineae (“heart strings”)

Close to prevent backflow


Operation of Heart Valves

Figure 11.4


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


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


The Heart: Conduction System Intrinsic conduction system

(nodal system)

Heart muscle cells contract, without nerve impulses, in a regular, continuous way


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


Heart Contractions Contraction is initiated by the sinoatrial node

Sequential stimulation occurs at other autorhythmic cells


Heart Contractions

Figure 11.5


Filling of Heart Chambers – the Cardiac Cycle = one complete heartbeat

Figure 11.6


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


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


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


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.


Cardiac Output Regulation

Figure 11.7


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


The Heart: Regulation of Heart Rate Increased heart rate

Sympathetic nervous system

Crisis

Low blood pressure

Hormones

Epinephrine

Thyroxine

Exercise

Decreased blood volume


The Heart: Regulation of Heart Rate Decreased heart rate

Parasympathetic nervous system

High blood pressure or blood volume

Decreased venous return


Blood Vessels: The Vascular System Taking blood to the tissues and back

Arteries

Arterioles

Capillaries

Venules

Veins

Figure 11.8a


The Vascular System

Figure 11.8b

Vessels have 3 layers or tunics


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


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


Capillary Exchange Substances exchanged due to concentration

gradients

Oxygen and nutrients leave the blood

Carbon dioxide and other wastes leave the cells


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


Diffusion at Capillary Beds

Figure 11.20


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


Hepatic Portal Circulation

Figure 11.14


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


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


Circulation to the Fetus

Figure 11.15


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


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


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


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


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)


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


Factors Determining Blood Pressure

Figure 11.19


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

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