Heart Anatomy

By: Collins Asadu-Bempah

• Size of a fist

• Cone Shaped

• Enclosed within mediastenum

• Covered in Pericardium

PERICARDIUM

• Double walled sac

2 Types

1) Fibrous Pericardium

Anchors heart to surrounding structures

Prevents overfilling of heart with blood

2) Serous Pericardium

-Parietal layer

-Visceral layer

• Paricardial Cavity - filled with serous fluid

-fluid allows heart to move in friction-free environment

*Pericarditis – inflammation of pericadium

-roughens the surfaces of serous membranes impedes heart movement

- in severe cases, large amounts of inflammatory fluids will leak into the pericardial cavity and compress the heart and limit its ability to pump blood. Known as a Cardiac Temponade

3 LAYERS OF THE HEART1) Epicardium – Superficial layer

- Visceral layer of serous pericardium

2) Myocardium – Middle, muscular layer

- Contractile layer of heart

3) Endocardium – Deeper layer

-Thin white sheet of endocardium

-lines heart chambers and valves

4 HEART CHAMBERS

2 Atria

2 Ventricles

*Interatrial Septum – a wall of tissue that divides the atria

*Interventricular Septum – divides the ventricles

ATRIA*Crista terminalis – separates anterior & posterior regions of right atrium*Fossa Ovalis – small depression located in right atrium. A remnant of the foramen ovale which is present during fetal development and allowed blood to flow from right atrium to left atrium• Blood enters right atrium via 3 veins

• Superior vena cava• Inferior vena cava• Coronary sinus

VENTRICLES

• Right Ventricle has larger anterior surface

• Left Ventricle has larger posteroinferior surface

• Left Ventricle is more muscular

• Trabecular Carneae - irregular ridges of muscle lining the inner surfaces of ventricles

• Chordae Tendineae – strong, fibrous strings attached to the valves of the heart

• Papillary Muscles – Anchor the chordae tendineae and keep them stretched

HEART VALVES

- Provide a unidirectional blood flow

- Made up of endocardium and connective tissue

- Attached to the chordae tendinae

• Tricuspid Valve

• Mitrial (bicuspid ) Valve

• Semilunar Valves

• Aortic Valves

Electrical System of the Heart- Composed of “autorhythmic” or self-excitable cells located at

distinct regions of the myocardium

• Sinoatrial Node (SA Node ) – located at right atrial wall

- the “pacemaker”

• Atrioventricular Node (AV Node)

• AV bundle

• Bundle Branches

• Purkinje Fibers

HEART PHYSIOLOGYCARDIAC CYCLE

*A 2 circuit system-Systemic -Pulmonary

*Deoxygenated blood enters the right atrium inferior and superior vena cava-Notice: AV valves are closed at this point because in atria not great

enough* SA node fires and causes atria contraction ( P-wave)* AV valves open due to increased pressure in atria and blood enters ventricles* There is a small delay before the electrical signal reaches the AV node; this allows enough time for ventricles to fill*AV node depolarizes and ventricular contraction

*Ventricular Systole- Isovolumetric contration-Ventricular Ejection

ISOVOLUMETRIC CONTRACTION

• All valves are closed

• Pressure in ventricles are great enough to cause AV valves to close but not great enough to cause SL and Aortic Valves to open

VENTRICULAR EJECTION

• Pressure is great enough to cause SL and Aortic valves to open and also to keep AV valves closed

• At this point the impulse has already reached the purkinjefibers and QRS complex is evident

ISOVOLUMETRIC RELAXATION

• Ventricles repolarizes ( T-wave) and cause the pressure to drop. The backflow of blood causes the SL and Aortic valves to close.

• AV valves remain closed because the pressure in the ventricles is not low enough to allow valves to open

sources

• http://classes.midlandstech.edu/carterp/Courses/bio211/chap18/chap18.html