Chapter 15: Cardiovascular System
cardiovascular system includes the heart and blood vessels.
blood circulation, the tissues lack oxygen and nutrients and waste accumulates.
of the Heart
and Location of the Heart
1. An average size
of an adult heart is generally 14 cm long and 9 cm wide.
heart is bounded laterally by the lungs, anteriorly by the sternum, and posteriorly by the vertebral column.
base of the heart lies beneath the second rib.
apex of the heart is at the level of fifth intercostal space.
of the Heart
pericardium is a covering that enclosed the heart and the proximal ends of the large blood vessels to which it attaches.
fibrous pericardium is the outer fibrous layer of the pericardium.
visceral pericardium is a serous membrane that is attached to the surface of the heart.
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
fluid reduces friction between the pericardial membranes as the heart moves.
of the Heart
three layers of the heart wall are endocardium, myocardium, and pericardium.
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.
middle layer is the myocardium.
myocardium is composed of cardiac muscle tissue.
inner layer is the endocardium.
endocardium consists of epithelium and connective tissue that contains manly elastic and collagenous fibers. It also contains
blood vessels and Purkinje fibers.
endocardium of the heart is continuous with the inner lining of the blood vessels attached to the heart.
Chambers and Valves
two upper chambers of the heart are the right atrium and the left atrium.
two lower chambers of the heart are the right ventricle and the left ventricle.
are small, earlike projections of the atria.
interatrial septum separates the right and left atrium.
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.
atrioventricular sulcus is located between the atria and ventricles.
right atrium receives blood from the superior and inferior vena cavae and the coronary sinus.
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.
muscles are located in ventricular walls and contract when the ventricles contract.
right ventricle receives blood from the right atrium.
right ventricle pumps blood into the pulmonary trunk.
pulmonary trunk divides into pulmonary arteries.
arteries deliver blood to the lungs.
pulmonary valve is located between the right ventricle and pulmonary trunk and opens when the right ventricle contracts.
veins carry blood from the lungs to the left atrium.
passes from the left atrium into the left ventricle.
mitral valve is located between the left atrium and left ventricle and functions to prevent the back flow of blood into the
left ventricle pumps blood into the aorta.
aortic valve is located between the left ventricle and aorta and opens when the left ventricle contracts.
tricuspid and mitral valves are also called A-V valves because they are positioned between atria and ventricles.
pulmonary and aortic valves are also called semilunar valves
because of their structures.
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.
skeleton of the heart provides attachments for the heart valves and for muscle fibers.
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.
Supply to the Heart
first two branches of the aorta are the left and right coronary arteries.
arteries supply blood to the tissues of the heart.
circumflex artery is located in the atrioventricular groove between the left atrium and left ventricle and supplies blood
to the walls of the left atrium and left ventricle.
anterior interventricular artery is located in the anterior interventricular groove and supplies blood to walls of both ventricles.
posterior interventricular artery is located the posterior interventricular groove and supplies the posterior walls of both
marginal artery is located along the lower border of the heart and supplies blood to the wall of the right atrium and right
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.
veins drain blood that passes through the capillaries of the myocardium.
coronary sinus is an enlarged vein on the posterior surface of the heart.
III. Heart Actions
systole is atrial contraction.
diastole is ventricular relaxation.
diastole is atrial relaxation.
systole is ventricular contraction.
the atria of the heart contract, the ventricles relax.
the ventricles of the heart contract, the atria relax.
1. During a cardiac
cycle, the pressure within the heart chambers rises and falls.
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
5. As ventricles contract,
the A-V valves snap shut.
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.
sounds are produced by the movement of blood through the heart and by the opening and closing of heart valve.
first heart sound is lubb and occurs during ventricular contraction.
when the A-V valves snap shut.
second heart sound is dupp and occurs during ventricular relaxation when the pulmonary valves snap shut.
4. A murmur
is an abnormal heart sound.
1. A functional
syncytium is a mass of merging cells that act as a unit.
syncytiums of the heart are in the atrial walls and the ventricular walls.
atrial syncytium and ventricular syncytium are connected by fibers of the cardiac conduction system.
cardiac conduction system consists of an S-A node, atrial syncytium, junctional fibers, A-V node, A-V bundle, bundle branches,
Purkinje fibers, and a ventricular syncytium.
S-A node is located in the wall of the right atrium and initiates one impulse after another.
S-A node is called the pacemaker because it generates the hearts rhythmic contractions.
4. As a
cardiac impulse travels from the S-A node into the atrial syncytium, it goes from cell to cell via gap junctions.
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.
are delayed as they move through the A-V node because this allows time for atria to contract.
the A-V node, impulses pass to the A-V bundle.
A-V bundle is located in the superior part of the interventricular septum and gives rise to bundle branches.
fibers carry impulses to distant regions of the ventricular myocardium.
ventricular myocardium contracts as a functioning unit.
fibers are located in the inferior portion of the interventricular septum, papillary muscles, and in the ventricular walls.
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.
of the ventricles begins at the apex of the heart and pushes blood superiorly toward the aortic and pulmonary semilunar valve.
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 on the 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.
use ECG patterns to assess the hearts ability to conduct impulses.
of Cardiac Cycle
volume of blood pumped changes to accommodate cellular requirements.
parasympathetic nerve to the heart is the vagus nerve
vagus nerve innervates the S-A and A-V nodes.
vagus nerve can alter heart rate by secreting acetylcholine onto the nodes.
fibers reach the heart via the accelerator nerves.
endings of accelerator nerves secrete norepinephrine which increases the rate and force of myocardial contractions.
cardiac control center controls the balance between the inhibitory actions of the parasympathetic nervous system and the stimulatory
actions of the sympathetic nervous system.
detect pressure changes.
baroreceptors in the aorta detect an increase in pressure, they signal the cardioinhibitory center of the medulla oblongata.
blood pressure is too high, the medulla oblongata sends parasympathetic impulses to the heart to decrease heart rate.
venous blood pressure increases abnormally, sympathetic impulses flow to the heart and heart rate and contraction increases.
body temperature increases heart action.
most important ions that influence heart action are potassium and calcium.
IV. Blood Vessels
vessels form a closed circuit of tubes that carries blood from the heart to cells and back again.
types of blood vessels are arteries, arterioles, capillaries, venules, and vein.
conduct blood away from the heart and to arterioles.
and veins conduct blood from capillaries and to the heart.
capillaries are sites of exchange of substances between the blood and the body cells.
are strong, elastic vessels that are adapted for carrying the blood away from the heart under high pressure.
give rise to arterioles.
three layers of the wall of an artery are the endothelium, tunica media, and tunica adventitia.
inner layer of an artery is called endothelium and functions to provide a smooth surface for blood flow and prevents blood
middle layer of an artery is called the tunica media and is composed of smooth muscle fibers.
outer layer is the tunica adventitia and consists of connective tissues with collagenous and elastic fibers.
vasa vasorum of an artery is a series of blood vessels that supply the wall of large arteries.
sympathetic nervous system innervates smooth muscle in arteries and arterioles.
fibers stimulate smooth muscle cells to contract, decreasing the diameter of the vessel.
is the contraction of smooth muscle cells in blood vessel walls.
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 pressure.
wall of a very small arteriole consists of an endothelium and some smooth muscle cells and connective tissue.
are branches of arterioles and help regulate blood flow to an area.
shunts are connections between arterioles and venous pathways.
smallest diameter blood vessels are capillaries.
connect arterioles to venules.
wall of a capillary consists of endothelium.
most permeable capillaries are located in the liver, spleen, and red bone marrow.
and tight capillaries are located brain.
a. The higher a
tissues rate of metabolism, the denser its capillary networks.
richly supplied with capillaries are muscle and nervous tissues.
that lack capillaries are cartilage and epithelial tissues.
exercise, blood is directed to capillary networks of skeletal muscle and it bypasses some of the capillary networks of the
of Capillary Blood Flow
sphincters are located at the opening of capillaries and their function is control the flow of blood into a capillary.
cells have low concentrations of oxygen, precapillary sphincters relax and blood flow increases.
in the Capillaries
vital function of exchanging gases, nutrients, and metabolic by-products between the blood and the tissue fluid surrounding
body cells occurs in the capillaries.
move through capillary walls by diffusion, filtration, and osmosis.
is the most important means of transfer.
and nutrients diffuse out of the capillary walls into surrounding cells because they are in a lower concentration in surrounding
dioxide and other wastes diffuse into the capillary blood because they are in a lower concentration in the capillary blood.
proteins generally remain in the blood because they are too big to cross through capillary walls.
filtration, hydrostatic pressure forces molecules through a membrane.
the capillaries, the force for filtration is provided by blood pressure.
pressure is greater at the arteriole end of the capillary.
osmotic pressure is osmotic pressure and is created by plasma proteins in the blood of capillaries.
the arteriolar end of the capillary, filtration predominates.
the venular end of the capillary, osmotic pressure predominates.
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
1. Blood pressure
is the force the blood exerts against the inner walls of the blood vessels.
pressure most commonly refers to pressure in arteries.
pressure is the maximum pressure and is created when the ventricles contract.
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.
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 posterior tibial artery.
C. Factors that Influence Arterial Blood Pressure
volume is the volume of blood discharged from the ventricle with one contraction.
output is the volume of blood discharged from a ventricle in one minute.
stroke volume or heart rate increases, cardiac output increases.
volume equals the sum of the formed elements and plasma volumes in the vascular system.
pressure is normally directly proportional to blood volume.
resistance is the friction between blood and the walls of the blood vessels.
peripheral resistance increases, blood flow decreases and blood pressure increases.
of blood vessels reduces peripheral resistance.
is the thickness of a fluid.
blood viscosity rises, blood pressure increases.
cells and plasma proteins contribute to blood viscosity.
of Blood Pressure
pressure is determined by cardiac output and peripheral resistance.
output depends on the stroke volume and heart rate.
volume is the difference between EDV and ESV.
Diastolic Volume is the volume of blood in each ventricle at the end of ventricular diastole.
Systolic Volume is the volume of blood in each ventricle at the end of the ventricular systole.
affecting stoke volume and heart rate are mechanical, neural, and chemical.
is the mechanical stretching of a ventricular wall prior to ventricular contraction.
greater the EDV, the greater the larger the preload lengthening of myocardial fibers.
Law of the Heart is the relationship between fiber length and force of contraction.
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
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.
Law of the Heart ensures that the volume of blood discharged from the heart is equal to the volume entering the heart.
blood pressure rises, baroreceptors initiate the cardioinhibitory reflex which decreases blood pressure.
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.
factors that increase heart rate and blood pressure are emotional responses, exercise, and a rise in body temperature.
arterial blood pressure suddenly increases, baroreceptors signal the vasomotor center, and sympathetic outflow to arterial
walls decreases, which results in a decrease in blood pressure.
that influence peripheral resistance are carbon dioxide, oxygen, and hydrogen ions.
1. Blood pressure
decreases as the blood moves through the arterial system into capillary networks.
flow through the venous system largely depends on skeletal muscle contractions and valves in veins.
squeezing action of skeletal muscles helps push blood toward the heart.
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.
is the constriction of a vein and occurs when some blood is lost from veins.
venous pressure is the pressure within the heart.
venous pressure is of special interest because it affects the pressure within the peripheral veins.
factors that increase central venous pressure are an increase in blood volume or widespread venoconstriction.
4. An increase
in central venous pressure can lead to peripheral edema.
VII. Paths of
two major pathways of blood vessels are the pulmonary circuit and the systemic circuit.
pulmonary circuit consists of vessels that carry blood from the heart to the lungs and back to the heart.
systemic circuit carries blood from the heart to all parts of the body, except the lungs, and back again.
enters the pulmonary circuit as it leaves the right atrium.
pulmonary trunk divides into pulmonary arteries.
the lungs the pulmonary arteries divide into lobar arteries.
lobar branches give rise to arterioles that continue into capillary networks.
blood in the arteries and arterioles of the pulmonary circuit is low in oxygen.
are exchanged between the blood and the air as the blood moves through alveolar capillaries.
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.
osmotic pressure of the blood removes any fluid that gets into the alveoli.
entering the venules of the pulmonary circuit is oxygen rich.
10. Venules merge to form veins.
veins return blood to the left atrium and this completes the pulmonary circuit.
1. Freshly oxygenated
blood moves from the left atrium to the left ventricle.
of the left ventricle forces blood into the systemic circuit.
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.
1. The aorta is the
largest diameter artery in the body.
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.
Branches of the Aorta
ascending aorta is the first portion of the aorta.
2. An aortic
sinus is a swelling of the aortic wall.
arteries arise from the aortic sinus.
bodies are small structures located within the aortic sinuses
contain chemoreceptors that sense blood concentrations of oxygen and carbon dioxide.
arteries originating from the aortic arch are the brachiocephalic artery, the left common carotid artery, and the left subclavian
brachiocephalic artery supplies blood to the tissues of the upper limb and head.
brachiocephalic divides into the right common carotid artery and the right subclavian.
common carotids supply blood to the head and neck.
subclavian arteries supply blood to the arms.
descending aorta is located the portion of the aorta that moves through the thoracic and abdominal cavity.
thoracic aorta is portion of the descending aorta above the diaphragm.
of the thoracic aorta are the bronchial, pericardial, and esophageal arteries.
abdominal aorta is the portion of the descending aorta below the diaphragm.
of the abdominal aorta are celiac, phrenic, superior mesenteric, suprarenal, renal, gonadal, inferior mesenteric, lumbar,
and middle sacral arteries.
celiac artery gives rise to gastric, splenic, and hepatic arteries which supply upper portions of the digestive tract, spleen
arteries supply the diaphragm.
superior mesenteric artery branches to many parts of the intestinal tract.
suprarenal arteries supply the adrenal glands.
renal arteries supply the kidneys.
gonadal arteries supply the ovaries and testes.
inferior mesenteric artery branches into arteries leading to the descending colon, sigmoid colon, and the rectum.
arteries supply muscle of the skin and posterior abdominal wall.
middle sacral artery supplies the sacrum and coccyx.
abdominal aorta terminates near the brim of the pelvis and divides into common iliac arteries.
common iliac arteries supply lower regions of the abdominal wall, the pelvic organs, and the lower extremities.
of the Neck, Head, and Brain
1. Branches of the
subclavian and common carotids supply structures within the neck, head, and brain.
main divisions of the subclavian artery to the neck, head, and brain are the vertebral, thyrocervical, and costocervical arteries.
common carotid artery communicates with these regions by means of the internal and external carotid arteries.
vertebral arteries arise from the subclavian arteries and supply the base of the neck.
5. A basilar
artery is formed by the union of vertebral arteries.
basilar artery divides into posterior cerebral arteries
portions of the occipital and temporal lobes of the cerebrum.
cerebral arterial circle is formed by the anterior and posterior cerebral arteries.
of the cerebral arterial circle are supply brain tissue and to provide alternate routes through which blood can reach brain
tissue in the event of an arterial occlusion.
arteries give rise to branches to the thyroid gland, parathyroid glands, larynx, trachea, esophagus, and pharynx.
arteries carry blood to muscles of the neck, back and thoracic wall.
common carotid arteries ascend deeply within the neck and divide to form internal and external carotid arteries.
external carotid artery gives off branches to structures of the neck, face, jaw, scalp, and base of skull.
branches off external carotid arteries are superior thyroid, lingual, facial, occipital and posterior auricular arteries.
superior thyroid artery supplies the hyoid bone, larynx, and thyroid gland.
lingual artery supplies the tongue and salivary glands.
facial artery supplies the pharynx, palate, chin, lips, and nose.
occipital artery supplies the back of the scalp, the meninges, the mastoid process, and muscles of the neck.
posterior auricular artery supplies the ear and scalp over the ear.
external carotid artery terminates by dividing into maxillary and superficial temporal arteries.
maxillary artery supplies the teeth, gums, jaws, cheek, nasal cavity, eyelids, and meninges.
temporal artery supplies the parotid glands and various regions of the face and scalp.
major branches of the internal carotid artery are ophthalmic, posterior communicating, and anterior choroid arteries.
ophthalmic artery supplies the eyeball and various muscles and accessory organs within the orbit.
posterior communicating artery forms part of the circle of Willis.
anterior choroids artery supplies the choroid plexus and structures within the brain.
internal carotid artery terminates by dividing into anterior and middle cerebral arteries.
middle cerebral artery supplies the lateral surfaces of the cerebrum.
anterior cerebral artery supplies the medial surfaces of the cerebrum.
29. A carotid
sinus is an enlargement of each carotid artery and contains baroreceptors that control blood pressure.
to the Shoulder and Upper Limb
1. As it
passes into the arm, the subclavian artery becomes the axillary artery.
axillary artery supplies structures of the axilla and chest wall.
axillary artery becomes the brachial artery.
brachial artery gives rise to deep brachial artery.
branches of the brachial artery supply structures of the arm.
the elbow, the brachial artery divides into ulnar and radial arteries.
branches of the ulnar artery supply structures on the ulnar side of the forearm.
branches of the radial artery supply structures on the radial side of the forearm.
supply to the wrist, hands, and fingers come from branches of the radial and ulnar arteries.