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Anatomy of the Heart

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The Systemic

and Pulmonary

Circuits

Pulmonary Circuit:

Heart Lungs

Systemic Circuit:

Heart Body tissues

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Apex:

Points to the left hip

Base:

Points to the right shoulder

Location of the Heart:

Mediastinum (Medial Cavity)

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Location of the Heart:

Mediastinum (Medial Cavity)

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Pericardium

Double-walled fibroserous sac

- Fibrous pericardium (outermost)

- Serous pericardium (parietal and visceral layer)

- Pericardial cavity (serous fluid: prevents friction)

Pericarditis: Inflammation of the pericardium

3 layers:

1) Pericardium

2) Myocardium

3) Endocardium

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Myocardium

The Heart Muscle

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Cardiac Muscle

Photomicrograph of cardiac muscle (700x)

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Endocardium

Innermost layer of the heart
White sheet of epithelium and connective tissue
Continuous with inner linings of heart vessels

Endocardium

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Components of the heart�External structures

Atria

Auricles

Ventricles
Vessels:

Inferior/Superior vena cava
Pulmonary trunk/artery
Pulmonary veins
Aortic Arch/Aorta
Coronary arteries/Cardiac veins

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Coronary Circulation:

Arteries and Veins

Coronary arteries

Functional blood supply of the heart
Provide myocardium with blood
If blocked, can cause heart attack

Blood that is pumped by the heart does not nourish the myocardium. The functional blood supply of the heart is provided by the right and left coronary arteries. They issue from the base of the aorta and encircle the heart anteriorly and posteriorly.

The myocardium is drained by the great, middle, and small cardiac veins which empty into the coronary sinus (in the right atrium).

Coronary Artery Disease (CAD): partial or complete blockage of coronary circulation. Cardiac muscle needs constant blood supply. Any reduction in blood flow to heart muscle produces reduction in cardiac performance (coronary ischemia). Cause: usually formation of fatty deposit (atherosclerotic plaque) in the wall of a coronary vessel. This can cause heart attacks.

Treatment options:

Catheter and removal of plaque w/laser

Balloon angioplasty (catheter w/inflatable end)

Coronary artery bypass graft (CABG)

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Coronary Circulation:

Arteries and Veins

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Valves:

- Tricuspid valve

- Pulmonary semilunar valve

- Bicuspid (Mitral) valve

- Aortic semilunar valve

Chambers:

- Right atrium

- Right ventricle

- Left atrium

- Left ventricle

Components of the Heart

Internal Structures

Muscles:

- Papillary muscle (and Chordae tendineae)

- Pectinate muscle

- Trabeculae carneae

Other: moderator band, interventricular

septum

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Right Atrium: Receives blood from the inferior and superior venae cavae. Superior v.c. delivers blood from head, neck, upper limbs, and chest. Inferior v.c. delivers blood from the rest of the trunk, the viscera, and the lower limbs.

Pectinate Muscles: only found in anterior wall of R atrium.
Fossa ovalis: small, shallow depression in R atrium. During embryonic development, it forms an open connection between the two atria (foramen ovale). It closes at birth and is sealed w/in 3 months of delivery.

Right/Left ventricles: contain muscular ridges called trabeculae carneae. Chordae tendineae are tendinous connective-tissue fibers that are attached to the atrioventricular valves (tricuspid and bicuspid valves respectively). These fibers originate at the papillary muscles. Chordae tendineae are holding the cusps of valves closed during ventricular contraction to prevent backflow into atria.

Left atrium: Receives blood from the respiratory capillaries

Interventricular septum: muscular ridge between the ventricles, contains conduction system (Bundle of His)

Atrioventricular valves: Tricuspid valve sends blood from R atrium to R ventricle; Bicuspid (mitral) valve sends blood from L atrium to L ventricle

Semilunar valves: Pulmonary Semilunar valve sends blood from R ventricle to lungs; Aortic Semilunar valve sends blood from L ventricle to Aortic arch/Aorta.

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Components of the Heart

Internal Structures

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Moderator Band

(Septomarginal Band)

Connects interventricular septum and papillary muscles
Helps coordinate contraction of ventricles

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Components of the Heart

Heart Valves

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Right AV valve: looking

into R atrium from

R ventricle

Components of the Heart

Heart Valves

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Bloodflow through the Heart

Right atrium Left atrium

Right ventricle Left ventricle

Pulmonary trunk Aortic arch

Pulmonary artery Aorta

Lungs

Tricuspid valve

PSL valve

Bicuspid valve

ASL valve

Inf/Sup. Vena cava

Pulmonary veins

O2 poor, CO2 rich

O2 rich, CO2 poor

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Aortic Arch

Pulmonary trunk/artery

Sup. vena cava

Pulmonary veins

Inf. vena cava

Pulmonary veins

Descending Aorta

Bicuspid valve

Tricuspid valve

Pulmonary SL valve

Aortic SL valve

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Figure 18.9

How heart valves operate

Atrioventricular valves (Tricuspid and Bicuspid (Mitral) valves):

Prevent backflow into atria when the ventricles are contracting
Chordae tendineae anchor the cusps to the papillary muscles in ventricle walls
When the heart is relaxed, valve flaps hang limply into ventricular chambers and blood flows into atria and ventricles. When ventricles contract, compressing blood in their chambers, intraventricular pressure rises, blood is forced toward atria and against valve flaps. Flap edges meet and close the flaps.
Chordae tendineae and papillary muscles anchor the valve flaps in their closed position. If the flaps would not be anchored in this manner, they would be blown upward into the atria (like an umbrella is blown inside out in a gusty wind)
Papillary muscles contract just before full ventricular contraction to ‘prepare’ the chordae tendineae for the ‘blow’.

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How heart valves operate

Semilunar valves (Pulmonary and aortic semilunar valves:

Guard the bases of the large arteries issuing from the ventricles (pulmonary trunk and aorta)
Prevent backflow into ventricles
Each valve is made out of 3 pocketlike cusps (semilunar=‘half moon’)
Their action differs from AV valves
When ventricles contract, intraventricular pressure rises above the pressure in the aorta and pulmonary trunk. This forces the SL valves open and their cusps are flattened against the arterial walls as blood rushes past them.
When the ventricles relax, and blood flows backward toward the heart, it fills the cusps and closes the valves.

There are no valves guarding entrances of the venae cavae and pulmonary veins into the R and L atria. Small amounts of blood do spurt back into these vessels during atrial contraction, but backflow is minimal because as it contracts, the atrial myocardium compresses (and collapses) these venous entry points.