exam1- cardiac structure

Cardiac anatomy location:

• The middle area of the chest

• Slightly to the left of the midline

• Infront of the the spine

• Behind the breastbone n lungs

• Between the lungs 3th-5th ICS

pericardium

• surrounded by a fibroserous sac

• 10-50ml of serous fluid

• Protects the heart- from infection n trauma

• Holds it in place (normal position)

• The fluid inside reduces friction as the heart beats

Pericardium

• a loose, double layer sac of elastic connective tissue

• Outer layer- fibrous pericardium

• 2 Inner layer- serous pericardium

  • Parietal layer

  • Visceral layer (Epi)- lines the fibrous, forming the parietal

Pericardial space

• between parietal n visceral

• Contains a clear fluid that is released by the serous membrane

• The fluid acts as lubricant to prevent friction during contraction and relaxation of the heart

The Heart

• right side- low pressure receives deoxygenated (Venus) blood from the body and pumps it to the lungs

  • Called Pulmonary circulatory system

• left side- high pressure receives oxygenated (arterial) blood from the lungs and pumps it to the body

  • Called Systemic circulatory system

The Heart

• the surface of the heart emerges two basic “rules” of normal cardiac anatomy:

  • Right sided structures lie mostly anterior to their left sided

  • Atrial chambers are located mostly to the right of their corresponding ventricles

Valves

• 4 major valves direct blood flow in a forward direction and prevent backward leakage

  • AV valve- tricuspid n mitral, separate the atria and ventricles

  • The semilunar valves- pulmonic and aortic, separate the ventricles from great arteries

Right Atrium and Ventricle

• coronary sinus carries venus return from the coronary arteries

• The inner wall of the outflow tract is smooth, the rest of ventricles is covered by a number of irregular bridges (termed trabeculae carneae) that gives RV wall a sponge like appearance

• A large trabecula that crosses the ventricular cavity is called the moderator band

Right Atrium and Ventricle

• contains 3 papillary muscles, projects into the chamber and their thin, string like chordae attach to the edge of the tricuspid valve leaflets

• Contraction of the papillary muscle to the chordae tendineae helps to align and restrain the leaflets so they are forced to close the tricuspid. Prevents blood from regurgitating (flowing back) into the RA during ventricular contraction

Right atrium and ventricle

• RV consists of three cusps attached to the fibrous ring

• During relaxation of the ventricle, elastic recoil of the pulmonary arteries forces blood back toward the heart, distending the valve cusps toward one another. This action closes the pulmonic valve and prevents regurgitation of blood back into the right ventricle

Left Atrium and Ventricle

• the posterior half of the LA are 4 pulmonary veins

• The wall of LA is about 2mm thick, being slightly greater than RA

• LV cone shaped and longer than RV

• most of the ventricle is covered by trabeculae carneae, which are finer and more numerous than RV

Left atrium and ventricle

• contains 2 large papillary muscles, much larger than their counterparts (matching) in RV, and chordae tendineae are thicker but less numerous

• chordae tendineae of each papillary muscle distribute to both leaflets of the mitral valve

• Tensing(tightening) the chordae tendineae during LV contraction helps restrain and align the mitral leaflets, enabling them to close properly and preventing the backward leakage of blood

Left atrium and ventricle

• aortic valve separated LV from the aorta

• Surrounding the aortic valve opening is a fibrous ring to which is attached the 3 cusps of the valve

• just above the R/L aortic valve cusps in the aortic wall are the origins of the R/L coronary arteries

IVS

• large muscular portion of the septum bulges(sticks out) toward the right ventricle

• The small oval shaped membranous part of the septum is thin and located just inferior to the cusps of the aortic valve (right below)

Impulse Conduction System: Bundle of His and Its Branches

• Located distal to the AV node- right before AV node

• Perforates(pass through) the IVS posteriorly (back of)

• Bifurcates into: (divided into 2)

  • RBB- compact, cable like on the right side(narrow, tight, cord shaped structure, like single thin cable/wire)

  • LBB- broad sheet over left septum(wider and spread out across, flatter and fans out more instead of being tight

Impulse Conduction System: Right Bundle Branch Pathway

• thick and deeply embedded(inside/surrounded) in septal muscle

• Travels toward the apex(bottom tip of the heart)

• Becomes subendocardial (under) near the anterior RV wall

• Bifurcation: (divide into 2)

  • One branch crosses RV via moderator band (muscle “bridge)- quickly carry electrical signals to the front wall of RV

  • Other continues toward ventricular tip- helps send the signal to the lower part of the ventricular

  • Forms a finely divided anastomosing plexus(connected network that spreads n overlaps) across the RV- after splitting, both branches keep dividing into many tiny fibers

Impulse Conduction System: Left Bundle Branch Pathway

• Divides into: 3 Fascicle- smaller branch of the electrical pathway

  • anterior- runs anteriorly to apex(bottom tip); forms plexus(network) near anterior papillary muscle (helps activate, spreads out under lining of the heart)

  • Posterior- travels to posterior papillary muscle, then forms a subendocardial plexus(network just under the inner heart lining)

  • Small septal branch- goes into/ between the IVS wall (helps activate the septal muscle early so contraction is coordinated)

• Plexus spreads to entire LV- breaks into fine network of fibers, spread across entire LV, making sure LV contracts strongly all at once

Impulse Conduction System: Purkinje Fibers and Ventricular Activation

• Subendocardial plexuses send outline fibers to ventricular muscle- forms network under inner lining heart, spread into ventricular muscle, deliver electrical signal quickly

• Impulse transmission order:

  • Papillary muscles (1)- tightens the chordae tendineae (valve cord)

  • Ventricle muscle (2)- spread thru main ventricular wall muscle

• Ensures papillary muscle contraction precedes ventricular contraction- making sure papillary muscle contract slightly before main ventricular wall

• Prevents regurgitation through AV valves- blood is forced toward only

Coronary Arteries

The heart muscle is supplied with oxygen and nutrients by the R/L coronary arteries, which arise from the root of the aorta just above the aortic valve cusps

Cardiac Vessels

• Include:

  • Coronary arteries (red

  • Coronary veins (blue)

  • Lymphatic vessels (green)

• Major components lie in epicardial fat within loose connective tissue- outside surface of the heart, fatty layer covering the heart, soft supportive tissue

Left Main Coronary Artery

• left main coronary artery passes between left atrium and pulmonary trunk

• Divides into:

  • Left Anterior Descending(LAD) artery

  • Circumflex artery

Left Main Coronary Artery

LAD artery:

• Travels in anterior IV groove to apex

  • Septal branches- anterior 2/3 of IVS, anterior papillary muscle

  • Diagonal branches- anterior surface of LV

• Circumflex artery:

  • Travels in left AV groove (surface of the heart)

  • Gives off obtuse marginal branches- lateral & posterior LV

Right Coronary Artery

• travels in right AC groove between right atrium & ventricle

• Gives off:

  • Acute marginal branches- right ventricle (along the boarder/edge)

  • Posterior descending artery(PDA)- inferior/posterior ventricles, posterior 1/3 of IVS

  • AV nodal artery

Coronary Veins

The cycle repeats

• followed a similar distribution to that of the coronary arteries. They return blood from the myocardium capillaries to the RA through the Coronary Sinus

The coronary arteries deliver oxygen-rich blood to the myocardium (heart muscle).

After the heart muscle uses the oxygen, the blood becomes oxygen-poor and must return to the heart through cardiac veins.