The heartCardiovascular system

Today’s goal

• Describe the gross anatomy of the human heart– Muscle layers– Chambers– membranes

Heart AnatomyYou know this…

• Approximately the size of a fist• Location, location, location– In the mediastinum between second rib and fifth

intercostal space– On the superior surface of diaphragm– Two-thirds to the left of the midsternal line

• Enclosed in pericardium, a double-walled sac

Figure 18.1a

Point ofmaximalintensity(PMI)

Diaphragm

(a)

Sternum

2nd rib

Midsternal line

Figure 18.1c

(c)

Superiorvena cava

Left lung

AortaParietalpleura (cut)

Pericardium(cut)

Pulmonarytrunk

Diaphragm

Apex ofheart

Pericardium

• Superficial fibrous pericardium• Protects, anchors, and prevents overfilling

Pericardium

• Deep two-layered serous pericardium• See notes, October, 2012

Figure 18.2

Fibrous pericardium

Parietal layer ofserous pericardiumPericardial cavity

Epicardium(visceral layerof serouspericardium)Myocardium

Endocardium

Pulmonarytrunk

Heart chamber

Heartwall

Pericardium

Myocardium

Layers of the Heart Wall1. Epicardium—visceral pericardium

-(layer of the serous pericardium)

2. Myocardium – Spiral bundles of cardiac muscle cells

3. Endocardium is continuous with endothelial lining of blood vessels

Figure 18.2

Fibrous pericardium

Parietal layer ofserous pericardiumPericardial cavity

Epicardium(visceral layerof serouspericardium)Myocardium

Endocardium

Pulmonarytrunk

Heart chamber

Heartwall

Pericardium

Myocardium

Figure 18.3

Cardiacmusclebundles

Chambers

• Four chambers– Two atria• Separated internally by the septum

Chambers

• Two ventricles– Separated by the interventricular septum– Anterior and posterior interventricular sulci mark

the position of the septum externally

Figure 18.4b

(b) Anterior view

Brachiocephalic trunk

Superior vena cava

Right pulmonaryarteryAscending aortaPulmonary trunk

Right pulmonaryveins

Right atrium

Right coronary artery(in coronary sulcus)Anterior cardiac vein

Right ventricle

Right marginal artery

Small cardiac vein

Inferior vena cava

Left common carotidarteryLeft subclavian artery

Ligamentum arteriosum

Left pulmonary artery

Left pulmonary veins

Circumflex artery

Left coronary artery(in coronary sulcus)

Left ventricle

Great cardiac vein

Anterior interventricularartery (in anteriorinterventricular sulcus)

Apex

Aortic arch

Auricle ofleft atrium

Atria: The Receiving Chambers

• Vessels entering right atrium– Superior vena cava – Inferior vena cava– Coronary sinus

• Vessels entering left atrium– Right and left pulmonary veins

Ventricles: The Discharging Chambers

• Papillary muscles project into the ventricular cavities

• Vessel leaving the right ventricle– Pulmonary trunk

• Vessel leaving the left ventricle– Aorta

Figure 18.4e

Aorta

Left pulmonaryarteryLeft atriumLeft pulmonaryveins

Mitral (bicuspid)valve

Aortic valve

Pulmonary valveLeft ventricle

Papillary muscleInterventricularseptumEpicardiumMyocardiumEndocardium

(e) Frontal section

Superior vena cava

Right pulmonaryarteryPulmonary trunk

Right atrium

Right pulmonaryveinsFossa ovalisPectinate muscles

Tricuspid valveRight ventricle

Chordae tendineae

Trabeculae carneae

Inferior vena cava

Pathway of Blood Through the Heart • The heart is two side-by-side pumps

– Right side is the pump for the pulmonary circuit• Vessels that carry blood to and from the lungs

– Left side is the pump for the systemic circuit• Vessels that carry the blood to and from all body tissues

Figure 18.5

Oxygen-rich,CO2-poor bloodOxygen-poor,CO2-rich blood

Capillary bedsof lungs wheregas exchangeoccurs

Capillary beds of allbody tissues wheregas exchange occurs

Pulmonary veinsPulmonary arteries

PulmonaryCircuit

SystemicCircuit

Aorta and branches

Left atrium

Heart

Left ventricleRight atrium

Right ventricle

Venae cavae

Pathway of Blood Through the Heart

• Right atrium tricuspid valve right ventricle• Right ventricle pulmonary semilunar valve

pulmonary trunk pulmonary arteries lungs

PLAY Animation: Rotatable heart (sectioned)

PLAY Animation: Rotatable heart (sectioned)

Pathway of Blood Through the Heart

• Lungs pulmonary veins left atrium• Left atrium bicuspid valve left ventricle• Left ventricle aortic semilunar valve aorta• Aorta systemic circulation

1 Start with blood in the right atrium2 Start with blood in the pulmonary vein3. You pick!

Pathway of Blood Through the HeartFun facts

• Equal V of blood are pumped through both circuits

• Pulmonary circuit is a short, low-pressure

Pathway of Blood Through the Heart

• Systemic circuit blood encounters much more resistance in the long pathways

• Anatomy of the ventricles reflects these differences

Figure 18.6

Rightventricle

Leftventricle

Interventricularseptum

Coronary Circulation

• The functional blood supply to the heart muscle itself

• Arterial supply varies person to person!• Collateral routes provide additional routes for

blood delivery

Coronary Circulation

• Arteries – Right – marginal– left coronary (in atrioventricular groove),

circumflex, and anterior interventricular arteries• Veins – Small cardiac, anterior cardiac, and great cardiac

veins

Figure 18.7a

Rightventricle

Rightcoronaryartery

Rightatrium

Rightmarginalartery

Posteriorinterventricularartery

Anteriorinterventricularartery

Circumflexartery

Leftcoronaryartery

Aorta

Anastomosis(junction ofvessels)

Leftventricle

Superiorvena cava

(a) The major coronary arteries

Left atrium

Pulmonarytrunk

Figure 18.7b

Superiorvena cava

Anteriorcardiacveins

Small cardiac vein

Middle cardiac vein

Greatcardiacvein

Coronarysinus

(b) The major cardiac veins

Figure 18.4d

(d) Posterior surface view

Aorta

Left pulmonaryartery

Left pulmonaryveinsAuricle of leftatriumLeft atrium

Great cardiacvein

Posterior veinof left ventricle

Left ventricle

Apex

Superior vena cava

Right pulmonary artery

Right pulmonary veins

Right atrium

Inferior vena cava

Right coronary artery(in coronary sulcus)

Coronary sinus

Posteriorinterventricularartery (in posteriorinterventricular sulcus)Middle cardiac veinRight ventricle

Homeostatic Imbalances

• Angina pectoris– Thoracic pain caused by a fleeting deficiency in

blood delivery to the myocardium– Cells are weakened

Homeostatic Imbalances

• Myocardial infarction (heart attack)– Prolonged coronary blockage– Areas of cell death are repaired with noncontractile scar tissue

Heart Valves

• Ensure unidirectional blood flow through the heart• Atrioventricular (AV) valves– Prevent backflow into the atria when ventricles contract– Tricuspid valve (right)– Mitral valve (left)

• Chordae tendineae anchor AV valve cusps to papillary muscles

Heart Valves

• Semilunar (SL) valves– Prevent backflow into the ventricles when

ventricles relax– Aortic semilunar valve– Pulmonary semilunar valve

Figure 18.8a

Pulmonary valveAortic valveArea of cutaway

Mitral valveTricuspid valve

Myocardium

Tricuspid(right atrioventricular)valveMitral(left atrioventricular)valveAorticvalve

Pulmonaryvalve

(b)

Pulmonary valveAortic valveArea of cutaway

Mitral valveTricuspid valve

Myocardium

Tricuspid(right atrioventricular)valve

(a)

Mitral(left atrioventricular)valveAortic valve

Pulmonaryvalve

Fibrousskeleton

Anterior

Figure 18.8b

Pulmonary valveAortic valveArea of cutaway

Mitral valveTricuspid valve

Myocardium

Tricuspid(right atrioventricular)valveMitral(left atrioventricular)valveAorticvalve

Pulmonaryvalve

(b)

Figure 18.8c

Pulmonaryvalve

AorticvalveArea ofcutawayMitralvalve

Tricuspidvalve

Chordae tendineaeattached to tricuspid valve flap

Papillarymuscle

(c)

Figure 18.8d

PulmonaryvalveAortic valveArea of cutawayMitral valveTricuspidvalve

Mitral valve

Chordaetendineae

Interventricularseptum

Myocardiumof left ventricle

Opening of inferiorvena cava

Tricuspid valve

Papillarymuscles

Myocardiumof rightventricle

(d)

Figure 18.9

1 Blood returning to theheart fills atria, puttingpressure againstatrioventricular valves;atrioventricular valves areforced open.

1 Ventricles contract, forcingblood against atrioventricularvalve cusps.

2 As ventricles fill,atrioventricular valve flapshang limply into ventricles.

2 Atrioventricular valvesclose.

3 Atria contract, forcingadditional blood into ventricles.

3 Papillary musclescontract and chordaetendineae tighten,preventing valve flapsfrom everting into atria.

(a) AV valves open; atrial pressure greater than ventricular pressure

(b) AV valves closed; atrial pressure less than ventricular pressure

Direction ofblood flow

Atrium

Ventricle

Cusp ofatrioventricularvalve (open)

Chordaetendineae

Papillarymuscle

Atrium

Blood inventricle

Cusps ofatrioventricularvalve (closed)

Figure 18.10

As ventriclescontract andintraventricularpressure rises,blood is pushed upagainst semilunarvalves, forcing themopen.

As ventricles relaxand intraventricularpressure falls, bloodflows back fromarteries, filling thecusps of semilunarvalves and forcingthem to close.

(a) Semilunar valves open

(b) Semilunar valves closed

Aorta

Pulmonarytrunk

Done with this lecture!

Microscopic Anatomy of Cardiac Muscle

• Cardiac muscle cells are striated, short, fat, branched, and interconnected

• Connective tissue matrix (endomysium) connects to the fibrous skeleton

• T tubules are wide but less numerous; SR is simpler than in skeletal muscle

• Numerous large mitochondria (25–35% of cell volume)

Figure 18.11a

Nucleus

DesmosomesGap junctions

Intercalated discs Cardiac muscle cell

(a)

Microscopic Anatomy of Cardiac Muscle

• Intercalated discs: junctions between cells anchor cardiac cells – Desmosomes prevent cells from separating during

contraction– Gap junctions allow ions to pass; electrically

couple adjacent cells• Heart muscle behaves as a functional

syncytium

Figure 18.11b

Nucleus

Nucleus

I bandA band

Cardiacmuscle cell

Sarcolemma

Z disc

Mitochondrion

Mitochondrion

T tubule

Sarcoplasmicreticulum

I band

Intercalateddisc

(b)