The Heart and Great Vessels

Coronary circulation

- The heart muscle is too thick to obtain nutrition via diffusion from blood in chambers so it needs its own blood supply. -the first two branches off of the aorta become the right and left coronary arteries.

Sinoatrial Node

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Six great veins

Four pulmonary veins, IVC, SVC.

Fossa ovalis (right-atrium)

- a thumb sized depression in the interatrial septum where an opening existed in the fetal heart. -allowed blood from umbilical vein to go from right atrium to the left atrium bypassing pulmonary circulation.

DIASTOLE

-Atria and ventricle muscles are relaxed, AV valves are open, semilunar valves are closed. Ventricles and atria fill with blood (left is a little slower).

DIASTOLE

-Atria relax and then ventricles relax and blood begins to change the heart chambers.

Cardiac Conduction System

-Cardiac muscle cells have intrinsic ability to generate and conduct electrical impulses and contract rhythmically : the heart can beat even after all the nerve supply are gone. -There are special regions of the cardiac muscle where the electrical signal is formed and spread. -This electrical signal is carried by ions: Sodium, Calcium, Potassium.

Basic structure of the heart

-Four chambers that move blood: two atria (left and right), two ventricles (right and left). -Valves : right atrioventricular valve (tricuspid), pulmonary semilunar valve, left atrioventricular valve (bicuspid), aortic semilunar. -Auricles -Blood vessels: SVC, IVC, coronary sinuses (blood drainage from heart muscle), pulmonary trunk (artery), pulmonary veins, aorta (coronary artery branches) -Heart has its own blood supply: coronary arteries and veins. - right side if heart has deoxygenated blood. -left side of heart has oxygenated blood.

SYSTOLE

-Heart becomes electrically excited and heart muscle contract. -First atria contract and pump blood into ventricles. -Next ventricles contract and pump blood into the pulmonary and systematic circulation to the semilunar valves.

moderator band (right ventricular)

-Septomarginal band is a band of cardiac muscle passing from the inter-ventricular septum to papillary muscle.

Cardiac Histology

-Three layers -Epicardium(visceral layer of serous pericardium) : Simple Squamous epithelium -Myocardium : cardiac muscle (striated, uninucleated,branching) -Endocardium(simple squamous epithelium)

Pericardial Sac= Pericardium

-a triple-layered sac that encloses the heart -Fibrous pericardium , parietal layer of serous pericardium and visceral layer of serous pericardium.

Arteries

-carry blood away from the heart -carry oxygenated blood exception: pulmonary arteries which leave right ventricle

Veins

-carry deoxygenated blood toward the heart. -carry deoxygenated blood. exception: pulmonary trunk and veins which leave lungs and enter left atria.

papillary muscle ( right ventricle)

-cone shaped muscle project from ventricle walls and attach to chordae tendinae. -help keep the AV valve closed during the contraction of heart.

Coronary sinuses (coronary circulation)

-drains cardiac veins -runs along the posterior surface of heart of AV junctions.

Left ventricle

-forms apex of heart and dominates inferior surface. -pumps blood to systematic circulation via the aorta. - very muscular and thicker walled vs right ventricle. -terbeculae -papillary muscles. -chordae tendinae -cups of bicuspid (mitral) valve -Aortic semilunar valve : 3 cups

Cardiac Conduction System

-heart muscle contraction and pumping of blood requires an organized sequence of electrical events. -To start systole (contraction) the heart muscle be electrically excited. -This electrical excitement, depolarization , and return to the relaxed state, repolarization , is measured with an electrocardiogram (ECG or EKG)

Fibrous pericardium

-holds heart in place and avoids overfilling with blood. -strong connective tissue which adheres through diaphragm and fused to roots of great vessels.

The heart surface anatomy and orientation

-lies to the thorax posterior to sternum and costal cartilage. -rests on superior surface of diaphragm. -largest structure within mediastinum(midline space between the lungs).

right ventricle

-pumps blood to pulmonary trunk (located superiorly) which goes to the lungs to become oxygenated. -thinner wall then left ventricle but thicker wall than atria-must contract and move blood. -inter ventricular septum is the muscular wall that separates the ventricles. -trabeculae : irregular ridges of muscle on ventricular walls.

RIGHT- ATRIUM

-receives deoxygenated blood via: SVC (Superior)-drains blood from head,neck, upper limbs. IVC(inferior)-drains blood from lower limbs, pelvis, abdomen and most of thorax.Coronary sinus (towards left and posterior )- receives venous blood from cardiac veins. -Right auricle projects anteriorly from superior corner: do not help to pump blood. Pectinate muscle present in auricle and atrium: anterior horizontal ridges. -interatrial septum separating the atrium. -Coronary sinus runs along posterior heart atrioventricular junctions. -pumps blood into right ventricular via the tricuspid valve -thin walled because blood flow into ventricle from atria is primarily dependent on gravity and not effort. -cups of tricuspid valve.

left atrium

-receives oxygenated blood from the lungs via the pulmonary veins. -makes up most of the hearts posterior surface or base . -left auricle present anteriorly. -pectinate muscles line auricle only. -fossa ovalis within interatrial septum. -thin walled like the right atrium as blood movement to the ventricle is dependent primarily on gravity. -left atrioventricular valve (mitral valve)-bicuspid valve (two cups)

Cardiac Cycle

-the filling with blood and contraction of the heart is called the diastole and systole, respectively . -Pulse is the major of these cycles of diastole and systole per min : heart beat is a single sequence of atrial contraction followed by ventricular contraction.

Serous pericardium

-the two layers of serous pericardium are continuous with one another at the great vessels. -the two layers are continuous with one another and form a pericardial cavity filled with small amount of pericardial fluid which reduces frictions.

Chordae tendinae (heart strings) (right ventricle)

-thin string band of connective tissue project from papillary muscles and attach to the flaps of tricuspid valve.

right-atrioventricular valve (tricuspid) (right atrium)

-three cups -opens into to the right ventricular.

The Heart : Blood Oxygenation Circuit

Deoxygenated blood from SVC, IVC, Coronary sinus enter right atrium-> Right artioventricular(tricuspid valve)->RV->Pulmonary semilunar valve->Pulmonary trunk->lungs bloods becomes oxygenated->four pulmonary veins->LA->left atrioventricular (mitral valve)->LV-> Aortic semilunar valve->aorta>oxygenated blood goes to body tissues-> deoxygenated blood enters to SVC and IVC.

Heart

Function: a muscular double pump that does 2 things: 1. Right side receives oxygen-poor blood from the body tissues and pumps this blood to the lungs to pick up oxygen and dispel carbon dioxide.-pulmonary circuit 2.left side receives oxygenated blood returning from the lungs and pumps this blood throughout the body to supply oxygen and nutrients to body tissues.- systematic circuit.

two great arteries

Pulmonary trunk and aorta

Anterior- intraventricular artery (surface)

Surface landmark to differentiate right and left ventricles.

base(surface)

broad flat superior posterior surface with blood vessel.

apex (surface)

cone-shaped inferior anterior surface

Auricles(surface)

little flap shaped like a dog ear project from left and right atria.

pulmonary semilunar valve (right ventricular)

three semi moon shaped cups.