Today’s Objectives

Be able to explain location, size and position of the heart

Be able to explain the definitions

Be able to label the pictures of the heart

Heart:Location, Size, Position

Located between the lungs and lower portion of mediastinum

Two-thirds of its mass is on the left Triangular shape - a closed fist Thoracic cavity: between sternum in the

front and the thoracic vertebrae behind Apex, lower edge, lies on the diaphragm

Anatomy of the Heart

Hollow, not solid Atria-upper chambers Ventricles-lower

chambers Myocardium-cardiac

muscle tissue that lines the walls of the chambers

Interatrial septum- septum (divider) between the atrial chambers

Interventricular septum-separates the ventricles Endocardium-thin layer of very smooth tissue

that lines each chamber (“endo” means within or inside)

Endocarditis-inflamed lining; rough and abrasive to RBC’s passing over its surface- thrombus- fatal blood clot

Pericardium – covering of the heart that consists of two layers of fibrous tissue:

1. Inner layer-epicardium (visceral pericardium) Covers the heart like skin on an apple (“epi” means upon or on)

2. Outer layer- parietal pericardium (loose fitting sac that allows the heart to beat)

No friction because the two layers are moist serous membranes

Pericardial fluid lubricates between heart and pericardial sac

Pericarditis

Inflammation of the pericardium Trauma, bacterial and viral infections, tumors Often visceral and parietal pericardium rub

together – severe chest pain Pericardial effusion- pericardial fluid, pus, or

blood accumulate in the space between the two layers and impairs pumping action of the heart

Cardiac tamponade-compression of the heart

Objectives

1. Be able to describe the conduction system of the heart

2. Be able to identify the structures of the heart involved in electrical conduction

Conduction System of the Heart

View the animation and take the quiz http://highered.mcgraw-hill.com/sites/0072

495855/student_view0/chapter22/animation__conducting_system_of_the_heart.html

Conduction System of the Heart

The intercalated disks are electrical connectors.

Thus, both atrial walls will contract at about the same time and both ventricular walls will contract at about the same time.

Conduction System Sequence

1. SA node (pacemaker) 2. All directions through atria causing

atrial fibers to contract 3. AV node 4. Bundle of His 5. Purkinje fibers