A closed system of the heart/blood The heart pumps blood

It is no more than a transportation pump

Blood vessels allow blood to circulate throughout the body MILES of blood vessels – intricate network

At all times, blood is contained within the vessels or heart

Function: Deliver oxygen and nutrients and re”move”

carbon dioxide and other waste products

Location Thorax: between the lungs & inferior to the

mediastinum Orientation

Apex (5cm) is pointed toward the left hip Superior surface lies on the diaphragm

Base (9 cm) is towards the right shoulder

Lies anterior to the vertebral column, posterior to the sternum

Size About the size of your fist Weighs less than 1 pound

Shape Hollow & cone shaped

Pericardium Double walled sac containing the heart & the roots

of the greater vessels Two walls: fibrous pericardium & serous

pericardium Functions to protect the heart & lubricate the heart

Fibrous pericardium is loose and superficial Functions:

Protect the heart Anchor the heart to its surrounding structures

(diaphragm & greater vessels) Prevents overfilling of the heart with blood

Serous membrane (pericardium) is deep to the fibrous pericardium and composed of two layers

Visceral pericardium Next to heart; also known as the epicardium

Parietal pericardium Outside layer that lines the inner surface of the fibrous

pericardium Serous fluid fills the space between the layers of

pericardium The fluid is pale yellow, translucent, & benign in

nature (“functionless)

Three layers Epicardium

Outside layer This layer is the visceral pericardium

Produces pericardial fluid Connective tissue layer Lubricates the motion between the inner and outer layers

of the pericardium Often infiltrated with fat, in older people

Myocardium Middle layer Mostly cardiac muscle – arranged in circular/spiral

bundles This arrangement is what links all the structures of the heart

together Collagen & elastin connective tissues form the fibrous

skeleton of the heart Creates additional support where the great vessels issue from

the heart/around the heart valves Over time, these area become “stretched out” from the continual

stress of blood pumping Connective tissue cannot carry electrical impulses - limits the

direct spread of action potential across cardiac tissue

Endocardium Inner layer Endothelium

Thin, white sheet of epithelial tissue Lines the entire surface of the

circulatory system, down to the interior surfaces of the capillaries

Label it all!

Right and left side act as separate pumps Four chambers & two major separations Atria

Thin walled & small blood just flows down Receiving chambers: blood enters the heart

Right atrium: receives deoxygenated blood from: Superior vena cava

Returns blood from the body that is superior from the diaphragm

Inferior vena cava Returns blood from the body that is inferior from the

diaphragm Coronary sinuses

Collects blood that drains from the myocardium itself Left atrium: receives oxygenated blood from:

Left & right pulmonary veins This makes up most of the heart’s base Transports blood back to the heart, from the lungs

Atria The right and left atria are separated by

the interatrial septum Fossa ovalis: small shallow depression that marks

where the foramen ovale had existed in the fetal heart

Auricles: small “flaps” that increase atrial volume – distinguishing feature of atria

Bundles of muscle in atria are specifically called pectinate muscles – look like they have been “raked with a comb”

Ventricles Makes up most of the mass of the heart Discharging chambers: blood leaves the

heart Right ventricle: pumps deoxygenated blood

to the lungs through the pulmonary arteries Makes up most of the anterior surface of the heart

Left ventricle: pumps (propels) oxygenated blood through the aorta out through the body (systemic circulation) Makes up most of the posteroinferior surface

Trabeculae carneae: irregular ridges in the internal walls of the muscle layer – “crossbars”

Papillary muscles: conelike muscle bundles Play a role in valve function

Interventricular septum Separates the two ventricles

Interatrial septum Separates the two atria

Systemic circulation Blood flows from the left side of the heart through the

body tissues and back to the right side of the heart Left side of the heart – systemic circuit pump

Blood leaves the left side of the heart to smaller arteries attached to body tissues to provide nutrients and gases.

Pulmonary circulation Blood flows from the right side of the heart to the

lungs and back to the left side of the heart Right side of the heart – pulmonary circuit pump

Starts as Oxygen poor/carbon dioxide rich blood in the right atrium/ventricle

OPPOSITE: Pulmonary veins carry OXYGEN RICH blood back to the L.A.

Coronary circulation Shortest circulation within the body Blood flow within the vessels of the heart itself

Ensures adequate oxygen supply for the heart muscle itself to function The vessels are the coronary arteries & cardiac

veins Coronary arteries are the only source of blood supply for

the actual myocardium Myocardium is too thick to allow for diffusion of nutrients

and gases Delivery of nutrients and gases are specifically

accomplished by the left and right coronary arteries (arising from the base of the aorta)

Coronary circulation The left C.A. runs towards the left side of the

heart, branching into the interventricular artery, supplies blood to the interventricular septum & the anterior walls of both ventricles

Then, that blood travels to the posterior walls of the left ventricle via the circumflex artery.

The right C.A. runs along the right side of the heart, branching in two: Marginal artery serves the myocardium of the

lateral part of the right side of the heart Posterior interventricular artery runs to the heart

apex and supplies the posterior ventricular walls

Coronary circulation Arterial supply of the heart varies considerably

Each person can have different anastomoses (merging points) of arteries These create different networks/routes of blood delivery to the heart This also explains how arterial blockages don’t always stop the heart from

working completely, unless. Complete blockage of a coronary artery leads to tissue death and heart attack

Coronary arteries provide pulsing, intermittent blood flow to the heart Actively deliver blood when the heart is relaxed Ineffective when the ventricles are contracting

Compressed by the contracting heart muscles Entrances to the coronary arteries are partly blocked by the flaps of

the open aortic semilunar valve

Even though the heart only represents 1/200 of body weight, it requires 1/20 of blood supply With the left ventricle using most of that blood supply

Valves allow blood to only flow in one direction (prevent backflow)

Four valves: Between the atria & ventricles: AV valves

Anchored in place by chordae tendinae: “heart strings” Open during heart relaxation and closed during ventricular

contract Bicuspid (mitral): left side of the heart Tricuspid: right side of the heart

Between ventricles & an artery: semilunar valves Closed during heart relaxation & open during ventricular

contract Pulmonary semilunar valve: between the right ventricle &

the pulmonary artery Aortic semilunar valve: between the left ventricle & the

aorta

Arteries: Aorta: leaves the left ventricle

Brings oxygenated blood out to the body Pulmonary artery: leaves the right ventricle

Brings deoxygenated blood to the lungs

Veins Superior & inferior vena cava: enters the right

atrium Brings deoxygenated blood into the heart

Pulmonary veins (there are four): enters the left atrium Brings oxygenated blood into the heart

Superior & Inferior venae cavae bring blood into the right atrium

From the right atrium, blood travels through the tricuspid valve to the right ventricle

Blood leaves the right ventricle, passing through the semilunar valve into the pulmonary trunk

The pulmonary trunk splits into the left/right pulmonary arteries that carry blood into the lungs

Oxygen is picked up and carbon dioxide is dropped off

Oxygen rich blood travels back to the heart through the four pulmonary veins

Blood enters the left atrium, travels through the bicuspid valve into the left ventricle

From the left ventricle, blood leaves the heart via the aortic semilunar valve and ultimately the aorta – allowing the blood to travel through the body.

Simple, no?

Blood in the heart chambers does not nourish the myocardium

The heart has its own nourishing circulatory system consisting of Coronary arteries—branch from the aorta to

supply the heart muscle with oxygenated blood Cardiac veins—drain the myocardium of blood Coronary sinus—a large vein on the posterior of

the heart, receives blood from cardiac veins Blood empties into the right atrium via the

coronary sinus

Intrinsic conduction system (nodal system) Heart muscle cells contract, without nerve

impulses, in a regular, continuous way Special tissue sets the pace

Sinoatrial node = SA node (“pacemaker”) Impulse generating tissue that keeps the regular

contractions of the heart It’s a group of cells called myocytes positioned by the

top of the right atrium It’s a muscle cell that contains some parts of the

contractile unit Atrioventricular node = AV node, is at the junction

of the atria and ventricles Serves as a “backup” for the SA node (pacemaker) Ensures there is a mild delay (0.12 seconds) in the

contraction of ventricles to ensure that there is actually enough blood to pump out of the ventricles

Special tissue sets the pace (continued) Atrioventricular bundle = AV bundle (bundle of His), is in

the interventricular septum Transmits impulses from the AV node to the apex of the

heart Purkinje fibers extend out of the AV bundle This bundle of cells is important because it’s regular rate of

impulse messaging is 40-60 beats per minute Bundle branches are in the interventricular septum Purkinje fibers spread within the ventricle wall muscles

Distribute the impulses to the walls of ventricles actually allowing cardiac muscle contraction to happen

Atrial fibrillation: the muscles of the atria “quiver” instead of regularly contract Physiological cause: overwhelming, disorganized

impulses from the SA node or AV node miscommunication

Increases stroke risk up to 7x because blood may pool in atria or clot

Contraction is initiated by the sinoatrial node Sequential stimulation occurs Force cardiac muscle depolarization in one

direction—from atria to ventricles Once SA node starts the heartbeat

Impulse spreads to the AV node Then the atria contract

At the AV node, the impulse passes through the AV bundle, bundle branches, and Purkinje fibers

Blood is ejected from the ventricles to the aorta and pulmonary trunk as the ventricles contract

Tachycardia—rapid heart rate over 100 beats per minute

Bradycardia—slow heart rate less than 60 beats per minutes

Atria contract simultaneously Atria relax, then ventricles contract Systole = contraction

Usually describes left ventricle contraction: cardiomyocytes

Diastole = relaxation Happens after systole; allows the heart to

refill with blood Cardiac cycle—events of one complete heart beat

Mid-to-late diastole—blood flows from atria into ventricles Ventricular systole—blood pressure builds before ventricle

contracts, pushing out blood Early diastole—atria finish refilling, ventricular pressure is

low

Atrialcontraction

Mid-to-late diastole(ventricular filling)

Ventricular systole(atria in diastole)

Early diastole

Isovolumetriccontraction phase

Ventricularejection phase

Isovolumetricrelaxation

Ventricularfilling

Left atrium

Right atrium

Left ventricle

Right ventricle

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Cardiac output (CO) Amount of blood pumped by each side (ventricle) of

the heart in one minute Stroke volume (SV)

Volume of blood pumped by each ventricle in one contraction (each heartbeat)

Usually remains relatively constant About 70 mL of blood is pumped out of the left

ventricle with each heartbeat Heart rate (HR)

Averages: 75 beats per minute CO = HR SV CO = HR (75 beats/min) SV (70 mL/beat) CO = 5250 mL/min Starling’s law of the heart—the more the cardiac muscle is

stretched, the stronger the contraction Changing heart rate is the most common way to change

cardiac output

Increased heart rate Sympathetic nervous system is stimulated

Crisis Low blood pressure

Hormones Epinephrine – released in stressful situations

(adrenaline) Thyroxine – used to increase metabolism

Exercise Decreased blood volume

Decreased heart rate Parasympathetic nervous system is activated in

reaction to a sympathetic stimulation High blood pressure or blood volume Decreased venous return

Transport blood to the tissues and back Carry blood away from

the heart Arteries Arterioles

Exchanges between tissues and blood Capillary beds

Return blood toward the heart Venules Veins

Three layers (tunics) Tunica intima

Endothelium – one layer of cells Have direct contact with

blood

Tunica media Smooth muscle

In larger arteries, there may be elastic tissue

Controlled by sympathetic nervous system

Tunica externa Mostly fibrous connective

tissue (collagen) Anchors blood vessels to

body organs

Walls of arteries are the thickest Lumens of veins are larger Larger veins have valves to prevent

backflow 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

Most arterial blood is pumped by the heart

Capillary beds consist of two types of vessels Vascular shunt—vessel directly connecting an

arteriole to a venule True capillaries—exchange vessels

Oxygen and nutrients cross to cells Carbon dioxide and metabolic waste products cross

into blood

Aorta Largest artery in the body Leaves from the left ventricle of

the heart Regions of the Aorta

Ascending aorta—leaves the left ventricle Left & right coronary arteries

leave here to supply blood to the heart

Aortic arch—arches to the left Thoracic aorta—travels

downward through the thorax Abdominal aorta—passes

through the diaphragm into the Abdominopelvic cavity

Arterial branches of the aortic arch (BCS) Brachiocephalic trunk splits into the

Right common carotid artery Right subclavian artery

Left common carotid artery splits into the Left internal and external carotid arteries

Left subclavian artery branches into the Vertebral artery In the axilla, the subclavian artery becomes

the axillary artery brachial artery radial and ulnar arteries

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Arterial branches of the thoracic aorta Intercostal arteries supply the muscles

of the thorax wall Other branches of the thoracic aorta

supply the Lungs (bronchial arteries) Esophagus (esophageal arteries) Diaphragm (phrenic arteries)

Arterial branches of the abdominal aorta Celiac trunk is the first branch of the abdominal

aorta. Three branches are Left gastric artery (stomach) Splenic artery (spleen) Common hepatic artery (liver)

Superior mesenteric artery supplies most of the small intestine and first half of the large intestine

Left and right renal arteries (kidney) Left and right gonadal arteries

Ovarian arteries in females serve the ovaries Testicular arteries in males serve the testes

Lumbar arteries serve muscles of the abdomen and trunk

Arterial branches of the abdominal aorta Inferior mesenteric artery serves the second half

of the large intestine Left and right common iliac arteries are the final

branches of the aorta Internal iliac arteries serve the pelvic organs External iliac arteries enter the thigh femoral

artery popliteal artery anterior and posterior tibial arteries

Superior and inferior vena cava enter the right atrium of the heart Superior vena cava drains the head and arms Inferior vena cava drains the lower body

Veins draining into the superior vena cava Radial and ulnar veins brachial vein axillary

vein These veins drain the arms Cephalic vein drains the lateral aspect of the arm

and empties into the axillary vein Basilic vein drains the medial aspect of the arm

and empties into the brachial vein Basilic and cephalic veins are jointed at the

median cubital vein (elbow area)

Veins draining into the superior vena cava Subclavian vein receives

Venous blood from the arm via the axillary vein Venous blood from skin and muscles via external jugular

vein Vertebral vein drains the posterior part of the head Internal jugular vein drains the dural sinuses of the

brain Left and right brachiocephalic veins receive venous

blood from the Subclavian veins Vertebral veins Internal jugular veins

Brachiocephalic veins join to form the superior vena cava right atrium of heart

Azygous vein drains the thorax

Veins draining into the inferior vena cava Anterior and posterior tibial veins and fibial veins drain the

legs Posterior tibial vein popliteal vein femoral vein

external iliac vein Great saphenous veins (longest veins of the body) receive

superficial drainage of the legs Each common iliac vein (left and right) is formed by the

union of the internal and external iliac vein on its own side Right gonadal vein drains the right ovary in females and

right testicle in males Left gonadal vein empties into the left renal vein Left and right renal veins drain the kidneys Hepatic portal vein drains the digestive organs and travels

through the liver before it enters systemic circulation Left and right hepatic veins drain the liver

Internal carotid arteries divide into Anterior and middle cerebral arteries These arteries supply most of the cerebrum

Vertebral arteries join once within the skull to form the basilar artery Basilar artery serves the brain stem and cerebellum

Posterior cerebral arteries form from the division of the basilar artery These arteries supply the posterior cerebrum

Circle of Willis Anterior and posterior blood supplies are united by

small communicating arterial branches Result—complete circle of connecting blood vessels

called cerebral arterial circle or circle of Willis

Pulse Pressure wave of

blood Monitored at

“pressure points” in arteries where pulse is easily palpated

Pulse averages 70–76 beats per minute at rest

Normal human range is variable Normal

140–110 mm Hg systolic 80–75 mm Hg diastolic

Hypotension Low systolic (below 110 mm HG) Often associated with illness

Hypertension High systolic (above 140 mm HG) Can be dangerous if it is chronic

BP is blood pressure BP is affected by age, weight, time of day,

exercise, body position, emotional state CO is the amount of blood pumped out of

the left ventricle per minute PR is peripheral resistance, or the amount of

friction blood encounters as it flows through vessels Narrowing of blood vessels and increased blood

volume increases PR BP = CO PR

Neural factors Autonomic nervous system adjustments (sympathetic

division) Renal factors

Regulation by altering blood volume Renin—hormonal control

Temperature Heat has a vasodilating effect Cold has a vasoconstricting effect

Chemicals Various substances can cause increases or decreases

Diet