CHAPTER 11: CARDIOVASCULAR SYSTEM

The Cardiovascular System A closed system of the heart/blood

The heart pumps blood Blood vessels allow blood to circulate

throughout the body 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

The HEART Location

Thorax: between the lungs & inferior to the mediastinum

Orientation Apex is pointed toward the left hip Base is towards the right shoulder

Size About the size of your fist

The HEART

The HEART

The HEART 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

Serous membrane 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”

The HEART: Heart wall 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 Myocardium

Middle layer Mostly cardiac muscle

Endocardium Inner layer Endothelium

Lines the entire surface of the circulatory system, down to the interior surfaces of the capillaries

Label it all!

The Chambers of the Heart Right and left side act as separate pumps Four chambers

Atria Receiving chambers: blood enters the heart

Right atrium: receives deoxygenated blood from: Superior vena cava, inferior vena cava, coronary

sinuses Left atrium: receives oxygenated blood from:

Left & right pulmonary veins Ventricles

Discharging chambers: blood leaves the heart Right ventricle: pumps deoxygenated blood to

the lungs through the pulmonary arteries Left ventricle: pumps oxygenated blood through

the aorta out through the body (systemic circulation)

The HEART

The Heart: Septa Interventricular septum

Separates the two ventricles Interatrial septum

Separates the two atria

The Heart: Valves 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

The Heart: Types of circulation Systemic circulation

Blood flows from the left side of the heart through the body tissues and back to the right side of the heart

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

lungs and back to the left side of the heart Coronary circulation

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

The Heart: Greater Vessels 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

Pathway of Blood flow 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

Pathway of Blood flow 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?

Coronary Circulation 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

Electrical Conduction of the Heart

Electrical Conduction of the Heart

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

Electrical Conduction of the Heart

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

Electrical Conduction of the Heart

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

Heart ContractionTachycardia—rapid heart rate over 100 beats per minute

Bradycardia—slow heart rate less than 60 beats per minutes

The Cardiac Cycle 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

The Cardiac Cycle

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

The Heart: Cardiac Output

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

Regulation of Heart Rate 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

Blood Vessels 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

Blood Vessels: Microscopic Anatomy 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

Differences between arteries & veins 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 Veins use the milking action of muscles to

help move blood

Capillaries 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

Major Arteries 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

Major Arteries 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

Major Arteries 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)

Major 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

Major Arteries 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

Major Arteries

Major Veins 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)

Major Veins 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

Major Veins 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

Major Veins

Arterial Supply of the Brain

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

Arterial Supply of the Brain

Pulse 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

Variations in Blood Pressure

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

Factors that affect blood pressure

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

Factors that affect blood pressure

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