Anatomy Cardiovascular System Case Study

Shier, Butler, and Lewis:  Hole’s Human Anatomy and Physiology, 11thed.                                Chapter 15:  Cardiovascular System 


Chapter 15:  Cardiovascular System


I. Introduction

A.  The heart pumps 7,000 liters of blood through the body each day.

B.  The cardiovascular system includes the heart and blood vessels.

C.   The pulmonary circuit sends oxygen-depleted blood to the lungs to pick up oxygen and unload carbon dioxide.

D.  The systemic circuit sends oxygen-rich blood and nutrients to the body cells and removes wastes.

II. Structure of the Heart

A.  Size and Location of the Heart

1.  An average size of an adult heart is generally 14 cm long and 9 cm wide.

2.  The heart is bounded laterally by the lungs, anteriorly by the sternum, and posteriorly by the vertebral column.

3.  The base of the heart lies beneath the second rib.

4.  The apex of the heart is at the level of fifth intercostal space.

B.  Coverings of the Heart

1.  The pericardium is a covering that enclosed the heart and the proximal ends of the large blood vessels to which it attaches.

2.  The fibrous pericardium is the outer fibrous layer of the pericardium.

3.  The visceral pericardium is a serous membrane that is attached to the surface of the heart.

4.  The parietal pericardium is a serous membrane that lines the fibrous layer of the pericardium.

 5.  The pericardial cavity is the space between the visceral pericardium and parietal pericardium.

6.  Serous fluid reduces friction between the pericardial membranes as the heart moves.

C.  Wall of the Heart

1.  The three layers of the heart wall are endocardium, myocardium, and pericardium.

2.  The epicardium is composed of a serous membrane that consists of connective tissue covered by epithelium, and it includes blood capillaries, lymph capillaries, and nerve fibers.

3.  The middle layer is the myocardium.

4.  The myocardium is composed of cardiac muscle tissue.

5.  The inner layer is the endocardium.

6.  The endocardium consists of epithelium and connective tissue that contains manly elastic and collagenous fibers. It also contains blood vessels and Purkinje fibers.

7.  The endocardium of the heart is continuous with the inner lining of the blood vessels attached to the heart.

D.  Heart Chambers and Valves

1.  The two upper chambers of the heart are the right atrium and the left atrium.

2.  Auricles are small, ear like projections of the atria.

3.  The two lower chambers of the heart are the right ventricle and the left ventricle.

4.  The interatrial septum separates the right and left atrium. 

5.  The interventricular septum separates the right and left ventricles.

6.  An atrioventricular orifice is an opening between an atrium and a ventricle.

7.  An atrioventricular orifice is protected by an A-V valve.

8.  The atrioventricular sulcus is located between the atria and ventricles.

9.  The right atrium receives blood from the superior and inferior vena cavae and the coronary sinus.

10.  The tricuspid valve is located between the right atrium and right ventricle and functions to prevent the back flow of blood into the right atrium.

 11. Chordae tendinae are fibrous strings and function to prevent cusps of A-V valves from swinging back into atria.

12.  Papillary muscles are located in ventricular walls and contract when the ventricles contract.

13.  The right ventricle receives blood from the right atrium.

14.  The right ventricle pumps blood into the pulmonary trunk.

15.  The pulmonary trunk divides into pulmonary arteries.

16.  Pulmonary arteries deliver blood to the lungs.

17.  The pulmonary valve is located between the right ventricle and pulmonary trunk and opens when the right ventriclecontracts.

18.  Pulmonary veins carry blood from the lungs to the left atrium.

19.  Blood passes from the left atrium into the left ventricle.

20.  The mitral valve is located between the left atrium and left ventricle and functions to prevent the back flow of blood intothe left atrium.

21.  The left ventricle pumps blood into the aorta.

22.  The aortic valve is located between the left ventricle and aorta and opens when the left ventricle contracts.

23.  The tricuspid and mitral valves are also called A-V valves because they are positioned between atria and ventricles.

24.  The pulmonary and aortic valves are also called semilunar valves

because of their structures.

E.  Skeleton of the Heart

1.  The skeleton of the heart is composed of rings of dense connective tissue and other masses of connective tissue in the interventricular septum.

2.  The skeleton of the heart provides attachments for the heart valves and for muscle fibers.

F.  Path of Blood Through the Heart

1.  Blood that is low in oxygen and rich in carbon dioxide enter the right atrium of the heart through venae cavae and the coronary sinus.

2.  As the right atrium contracts, blood passes into the right ventricle.

3.  When the right ventricle contracts, blood moves into the pulmonary trunk.

4.  From the pulmonary arteries blood enters the lungs.

5.  The blood loses carbon dioxide in the lungs and picks up oxygen.

6.  Freshly oxygenated blood returns to the heart through pulmonary veins.

7.  The pulmonary veins deliver blood to the left atrium.

8.  When the left atrium contracts, blood passes into the left ventricle.

9.  When the left ventricle contracts, blood passes into the aorta.

G.  Blood Supply to the Heart

1.  The first two branches of the aorta are the left and right coronary arteries.

2.  Coronary arteries supply blood to the tissues of the heart.

3.  The circumflex artery is located in the atrio ventricular groove between the left atrium and left ventricle and supplies blood to the walls of the left atrium and left ventricle.

4.  The anterior interventricular artery is located in the anterior interventricular groove and supplies blood to walls of both ventricles.

5.  The posterior interventricular artery is located the posterior interventricular groove and supplies the posterior walls of both ventricles.

6.  The marginal artery is located along the lower border of the heart and supplies blood to the wall of the right atrium and right ventricle.

7.  Blood flow in coronary arteries is poorest during ventricular contraction because the contracting myocardium interferes with blood flow and the openings of the coronary arteries are partially blocked by cusps of the aortic valve.

8.  Cardiac veins drain blood that passes through the capillaries of the myocardium.

9.  The coronary sinus is an enlarged vein on the posterior surface of the heart.

III.  Heart Actions

A.  Introduction

1.  Atrial systole is atrial contraction.

2.  Ventricular diastole is ventricular relaxation.

3.  Atrial diastole is atrial relaxation.

4.  Ventricular systole is ventricular contraction.

5.  When the atria of the heart contract, the ventricles relax.

6.  When the ventricles of the heart contract,the atria relax.

B.  Cardiac Cycle

1.  During a cardiac cycle, the pressure within the heart chambers rises and falls which is what causes the valves to open and close.

2.  The pressure in the ventricles is low during ventricular diastole.

3.  During diastole, the A-V valves are open.

4.  About 70%of the blood flows passively from the atria into ventricles and the remaining blood is pushed into the ventricles when the atria contract.

5.  As ventricles contract, the A-V valves close.

6.  When the pressure in the atria is lower than venous pressure, blood flows from the veins into atria. 

7.  During ventricular systole, ventricular pressure increases and the pulmonary valves open.

8.  As blood flows out of the ventricles, ventricular pressure decreases.

9.  The semilunar valves close when the pressure in the ventricles is lower than pressure in the aorta and pulmonary trunk.

C.  Heart Sounds

1.  Heart sounds are produced by the movement of blood through the heart and by the opening and closing of heart valve.

2.  The first heart sound is lubb and occurs during ventricular systole

when the A-V valves close.

3.  The second heart sound is dupp and occurs during ventricular diastole when the pulmonary and aortic valves close.

4.  A murmur is an abnormal heart sound.

D.  Cardiac Muscle Fibers

1.  A functional syncytium is a mass of merging cells that act as a unit.

2.  Two syncytiums of the heart are in the atrial walls and the ventricular walls.

3.  The atrial syncytium and ventricular syncytium are connected by fibers of the cardiac conduction system.

E.  Cardiac Conduction System

1.  The cardiac conduction system is responsible for coordinating events of the cardiac cycle.

2.  The S-A node is located in the wall of the right atrium and initiates one impulse after another.

3.  The S-A node is called the pacemaker because it generates the heart’s rhythmic contractions.

4.  As a cardiac impulse travels from the S-Anode into the atrial syncytium, it goes from cell to cell via gap junctions.

5.  Conducting fibers deliver impulses from the S-A node to the A-V node.

 6.  The A-V node is located in the inferior part of the interatrial septum and provides the only normal conduction pathway between the atrial and ventricular syncytiums.

7.  Impulses are delayed as they move through the A-V node because this allows time for atria to contract.

8.  From the A-V node, impulses pass to the A-V bundle.

9.  The A-V bundle is located in the superior part of the interventricular septum and gives rise to bundle branches.

10.  Purkinje fibers carry impulses to distant regions of the ventricular myocardium.

11.  The ventricular myocardium contracts as a functioning unit.

12.  Purkinje fibers are located in the inferior portion of the interventricular septum, papillary muscles, and in the ventricular walls.

13.  The ventricular walls contract with a twisting motion because the muscle fibers in the ventricular walls form irregular whorls.  The twisting motion produces a pushing motion.

14.  Contraction of the ventricles begins at the apex of the heart and pushes blood superiorly toward the aortic and pulmonary semilunar valve.

F.  Electrocardiogram

1.  An electrocardiogram is a recording of the electrical changes that occur in the myocardium during a cardiac cycle.

2.  An ECG is recorded by placing electrodes onthe skin and connecting the electrodes to an instrument that respond to very weak electrical changes by moving a pen on a moving strip of paper.

3.  A P-wave is produced when atrial fibers depolarize.

4.  A QRS-wave is produced when ventricular fibers depolarize.

5.  A T-wave is produced when the ventricular fibers repolarize.

6.  Physician’s use ECG patterns to assess the heart’s ability to conduct impulses.

G.  Regulation of Cardiac Cycle

1.  The volume of blood pumped changes to accommodate cellular requirements.

2.  The parasympathetic nerve to the heart is the vagus nerve

3.  The vagus nerve innervates the S-A and A-Vnodes.

4.  The vagus nerve can alter heart rate by secreting acetylcholine onto the nodes.

5.  Sympathetic fibers reach the heart via the accelerator nerves.

6.  The endings of accelerator nerves secrete norepinephrine which increases the rate and force of myocardial contractions.

7.  The cardiac control center controls the balance between the inhibitory actions of the parasympathetic nervous system and the stimulatory actions of the sympathetic nervous system.

8.  Baroreceptors detect pressure changes.

9.  When baroreceptors in the aorta detect an increase in pressure, they signal the cardioinhibitory center of the medulla oblongata.

10.  If blood pressure is too high, the medulla oblongata sends parasympathetic impulses to the heart to decrease heart rate.

11.  If venous blood pressure increases abnormally, sympathetic impulses flow to the heart and heart rate and contraction increases.

12.  Rising body temperature increases heart action.

13.  The most important ions that influence heart action are potassium and calcium.

IV.  BloodVessels

A.  Introduction

1.  Blood vessels form a closed circuit of tubes that carries blood from the heart to the body cells and back again.

2.  Five types of blood vessels are arteries,arterioles, capillaries, venules, and vein.

3.  Arteries conduct blood away from the heart and to arterioles.

4.  Venules and veins conduct blood from capillaries and to the heart.

5.  The capillaries are sites of exchange of substances between the blood and the body cells.

B.  Arteries and Arterioles

1.  Arteries are strong, elastic vessels that are adapted for carrying the blood away from the heart under high pressure.

2.  Arteries give rise to arterioles.

3.  The three layers of the wall of an artery are the endothelium, tunica media, and tunica adventitia.

4.  The inner layer of an artery is called endothelium and functions to provide a smooth surface for blood flow and prevents blood clotting.

5.  The middle layer of an artery is called the tunica media and is composed of smooth muscle fibers.

6.  The outer layer is the tunica adventitia andconsists of connective tissues with collagenous and elastic fibers.

7.  The vasa vasorum of an artery is a series of blood vessels that supply the wall of large arteries.

8.  The sympathetic nervous system innervates smooth muscle in arteries and arterioles.

9.  Vasomotor fibers stimulate smooth muscle cells to contract, decreasing the diameter of the vessel.

10.  Vasoconstriction is the contraction of smooth muscle cells in blood vessel walls.

11.  Vasodilation is the relaxation of smooth muscle cells in the walls of blood vessels and occurs when the blood vessel diameter increases.

12.Changes in the diameters of arteries and arterioles greatly influence blood flow and blood pressure.

13.  The wall of a very small arteriole consis tsof an endothelium and some smooth muscle cells and connective tissue.

14.  Metarterioles are branches of arterioles and help regulate blood flow to an area.

15.  Arteriovenous shunts are connections between arterioles and venous pathways.

C.  Capillaries

1.  Introduction

a.  The smallest diameter blood vessels are capillaries.

b.  Capillaries connect arterioles to venules.

c.  The wall of a capillary consists of endothelium.

2.  Capillary Permeability

a.  The most permeable capillaries are located in the liver, spleen, and red bone marrow.

b.  Protective and tight capillaries are located brain.

3.  Capillary Arrangement

a.  The highera tissue’s rate of metabolism, the denser its capillary networks.

b.  Tissues richly supplied with capillaries are muscle and nervous tissues.

c.  Tissues that lack capillaries are cartilage and epithelial tissues.

d.  During exercise, blood is directed to capillary networks of skeletal muscle and it bypasses some of the capillary networks of the digestive tract.

4.  Regulation of Capillary Blood Flow

a. Precapillary sphincters are located at the opening of capillaries and their function is control the flow of blood into a capillary. 

b.  When cells have low concentrations of oxygen,precapillary sphincters relax and blood flow increases.

5.  Exchanges in the Capillaries

a.  The vital function of exchanging gases,nutrients, and metabolic by-products between the blood and the tissue fluid surrounding body cells occurs in the capillaries.

b.  Biochemicals move through capillary walls by diffusion, filtration, and osmosis.

c.  Diffusion is the most important means of transfer.

d.  Oxygen and nutrients diffuse out of the capillary walls into surrounding cells because they are in a lower concentration in surrounding cells.

e.  Carbon dioxide and other wastes diffuse into the capillary blood because they are in a lower concentration in the capillary blood.

f.  Plasma proteins generally remain in the blood because they are too big to cross through capillary walls.

g.  In filtration, hydrostatic pressure forces molecules through a membrane.

h.  In the capillaries, the force for filtration is provided by blood pressure.

i.  Blood pressure is greater at the arteriole end of the capillary.

j.  Colloid osmotic pressure is osmotic pressure and is created by plasma proteins in the blood of capillaries.

k.  At the arteriolar end of the capillary,filtration predominates.

l.  At the venular end of the capillary, osmotic pressure predominates.

D.  Venules and Veins

1.  Venules are blood vessels that continue from capillaries and merge to form veins.

2.  The middle layer of the wall of a vein is very thin and poorly developed compared to that of an artery.

3.  The function of valves in veins is keep blood flowing toward the heart.

4.  Veins also function as blood reservoirs.

V.  Blood Pressure

A.  Introduction

1.  Blood pressure is the force the blood exerts against the inner walls of the blood vessels.

2.  Blood pressure most commonly refers to pressure in arteries.

B.  Arterial Blood Pressure

1.  Systolic pressure is the maximum pressure and is created when the ventricles contract.

2.  Diastolic pressure is the minimum pressure and is created when the ventricles relax.

3.  A pulse is the alternate expanding and recoiling of an arterial wall.

4.  Common places to detect a pulse are the radial artery, the brachial artery, the carotid artery, the temporal artery,the facial artery, the femoral artery, the popliteal artery, and the posteriortibial artery.

C. Factors that Influence Arterial Blood Pressure

1.  Heart Action

a.  Stroke volume is the volume of blood discharged from the ventricle with one contraction.

b.  Cardiac output is the volume of blood discharged from a ventricle in one minute.

c.  If stroke volume or heart rate increases,cardiac output increases.

2.  Blood Volume

a.  Blood volume equals the sum of the formed elements and plasma volumes in the vascular system.

b.  Blood pressure is normally directly proportional to blood volume.

3.  Peripheral Resistance

a.  Peripheral resistance is the friction between blood and the walls of the blood vessels.

b.  If peripheral resistance increases, blood flow decreases and blood pressure increases.

c.  Dilation of blood vessels reduces peripheral resistance.

4.  Viscosity

a.  Viscosity is the thickness of a fluid.

b.  As blood viscosity rises, blood pressure increases.

c.  Blood cells and plasma proteins contribute to blood viscosity.

D.  Control of Blood Pressure

1.  Blood pressure is determined by cardiac output and peripheral resistance.

2.  Cardiac output depends on the stroke volume and heart rate.

3.  Stroke volume is the difference between EDV and ESV.

4.  End Diastolic Volume is the volume of blood in each ventricle at the end of ventricular diastole.

5.  End Systolic Volume is the volume of blood in each ventricle at the end of the ventricular systole.

6.  Factors affecting stoke volume and heart rate are mechanical, neural, and chemical.

7.  Preload is the mechanical stretching of aventricular wall prior to ventricular contraction.

8.  The greater the EDV, the greater the preload lengthening of myocardial fibers.

9.  Starling’s Law of the Heart is the relationship between fiber length and force of contraction.

10.  The more blood that enters the heart, the greater the ventricular distention, the stronger the ventricular contractions,the greater the stroke volume and the greater the cardiac output

11.  The less blood that returns from veins to the heart, the less ventricular distension, the weaker the ventricular contractions, the lesser the stroke volume and the lesser the cardiac output.

12.  Starling’s Law of the Heart ensures that the volume of blood discharged from the heart is equal to the volume entering its chambers.

13.  If blood pressure rises, baroreceptors initiate the cardioinhibitory reflex which decreases blood pressure.

14.  If blood pressure falls, the cardioaccelerator reflex occurs which increases sympathetic stimulation to the heart, which increases heart rate and cardiac output, which increases blood pressure.

15.  Other factors that increase heart rate and blood pressure are emotional responses, exercise, and a rise in body temperature.

16.  When arterial blood pressure suddenly increases, baroreceptors signal the vasomotor center, and sympathetic outflowto arterial walls decreases, which results in a decrease in blood pressure.

17.  Chemicals that influence peripheral resistance are carbon dioxide, oxygen, and hydrogen ions.

E.  Venous Blood Flow

1.  Blood pressure decreases as the blood moves through the arterial system into capillary networks.

2.  Blood flow through the venous system largely depends on skeletal muscle contractions and valves in veins.

3.  The squeezing action of skeletal muscles helps push blood toward the heart.

4.  During inspiration, the pressure in the thoracic cavity is reduced and the pressure in the abdominal cavity increases.

5.  An increases in abdominal pressure will squeeze blood out of abdominal veins.

6.    When venous pressure is low, sympathetic reflexes stimulate smooth muscles in the walls of the veins to contract. 

F.  Central Venous Pressure

1.  Central venous pressure is the pressure within the heart.

2.  Central venous pressure is of special interest because it affects the pressure within the peripheral veins.

3.  Other factors that increase central venous pressure are an increase in blood volume or widespread venoconstriction.

4.  An increase in central venous pressure canlead to peripheral edema.

VII.  Paths of Circulation

A.  Introduction

1.  The two major pathways of blood vessels are the pulmonary circuit and the systemic circuit.

2.  The pulmonary circuit consists of vessels that carry blood from the heart to the lungs and back to the heart.

3.  The systemic circuit carries blood from the heart to all parts of the body and back again.

B.  Pulmonary Circuit

1.  Blood enters the pulmonary circuit as it leaves the right ventricle through the pulmonary trunk.

2.  The pulmonary trunk divides into pulmonary arteries.

3.  Within the lungs the pulmonary arteries divide into lobar branches.

4.  The lobar branches give rise to arterioles that continue into capillary networks.

5.  The blood in the arteries and arterioles of the pulmonary circuit is low in oxygen and high in carbon dioxide.

6.  Gases are exchanged between the blood and the air as the blood moves through alveolar capillaries.

7.  The arterial pressure in the pulmonary circuit is less than in the systemic circuit because the right ventricle contracts with a force less than that of the left ventricle.

8.  Higher osmotic pressure of the blood removes any fluid that gets into the alveoli.

9.  Blood entering the venules of the pulmonary circuit is oxygen rich and low in carbon dioxide.

10. Venules merge to form veins.

11.  Pulmonary veins return blood to the left atrium and this completes the pulmonary circuit.

C.  Systemic Circuit

1.  Freshly oxygenated blood moves from the left atrium to the left ventricle.

2.  Contraction of the left ventricle forces blood into the systemic circuit.

3.  The systemic circuit includes the aorta and its branches that lead to all of the body tissues, as well as the companion system of veins that returns blood to the right atrium.

VIII. Arterial System

A.  Introduction

1.  The aorta is the largest diameter artery in the body.

2.  The aorta extends upward from the left ventricle, arches over the heart to the left, and descends just anterior and to the left of the vertebral column.

B.  Principal Branches of the Aorta

1.  The ascending aorta is the first portion of the aorta.

2.  An aortic sinus is a swelling of the aortic wall.

3.  Coronary arteries arise from the aortic sinus.

4.  Aortic bodies are small structures located within the aortic sinuses

   and contain chemoreceptors that sense blood concentrations of oxygen and carbon dioxide.

5.  Three arteries originating from the aortic arch are the brachiocephalic artery, the left common carotid artery, and the left subclavian artery.

6.  The brachiocephalic artery supplies blood to the tissues of the upper limb and head.

7.  The brachiocephalic divides into the right common carotid artery and the right subclavian.

8.  The common carotids supply blood to the head and neck.

9.  The subclavian arteries supply blood to the arms.

10.  The descending aorta moves through the thoracic and abdominal cavity.

11.  The thoracic aorta is portion of the descending aorta above the diaphragm.

12.  Branches of the thoracic aorta are the bronchial, pericardial, and esophageal arteries.

13.  The abdominal aorta is the portion of the descending aorta below the diaphragm.

14.  Branches of the abdominal aorta are celiac,phrenic, superior mesenteric, suprarenal, renal, gonadal, inferior mesenteric,lumbar, and middle sacral arteries.

15.  The celiac artery gives rise to gastric,splenic, and hepatic arteries which supply upper portions of the digestive tract, spleen and liver.

16.  Phrenic arteries supply the diaphragm.

17.  The superior mesenteric artery branches to many parts of the intestinal tract.

18.  The suprarenal arteries supply the adrenal glands.

19.  The renal arteries supply the kidneys.

20.  The gonadal arteries supply the ovaries and testes.

21.  The inferior mesenteric artery branches into arteries leading to the descending colon, sigmoid colon, and the rectum.

22.  Lumbar arteries supply muscle of the skin and posterior abdominal wall.

23.  The middle sacral artery supplies the sacrum and coccyx.

24.  The abdominal aorta terminates near the brim of the pelvis and divides into common iliac arteries.

25.  The common iliac arteries supply lower regions of the abdominal wall, the pelvic organs, and the lower extremities.

C.  Arteries of the Neck, Head, and Brain

1.  Branchesof the subclavian and common carotids supply structures within the neck, head,and brain.

2.  The main divisions of the subclavian arteryto the neck, head, and brain are the vertebral, thyrocervical, and costocervical arteries.

3.  The common carotid artery communicates with these regions by means of the internal and external carotid arteries.

4.  The vertebral arteries arise from thes ubclavian arteries and supply the base of the neck.

5.  A basilar artery is formed by the union of vertebral arteries.


 This case study focuses on a baby boy who was born with a problem with his heart.  The story is based on a real scenario, though some of the names have been changed, and the parents gave permission to include photos of the infant.   Students will read about symptoms that occur when a baby is born with stenosis, or a narrowing of the artery.   Students consider treatment options and compare the circulation of a fetus to that of an adult.   Finally, the Ross Procedure is described where a valve from the pulmonary artery is moved to the aorta.

This case study was made for a high school anatomy class, and may not be appropriate for younger audiences.  Students should have already completed the chapter on the circulatory system and have a strong foundation in how the circulatory system works.  Case studies are designed to be completed in small groups so that students can have discussions and help each other with difficult vocabulary.

Grade Level:  11-12  | Time Required:  2-3 Hours

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HS-LS1-2 Develop and use a model to illustratethe hierarchical organizationof interacting systemsthat provide specific functions within multicellular organisms



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