Topic 2 The Heart

Objective 1 Function of the Heart The function of the heart is to provide pressure for pumping blood into the arteries of systemic circulation. The heart functions as a pump by alternatively contracting and relaxing. Diastole: relaxation phase; during diastole, the pressure in a chamber of the heart is reduced Systole: contraction phase; during systole, the pressure in a chamber of the heart is increased Ventricular Ventricular Pressure low, Ventricles fill Pressure elevated, Ventricles empty Diastole Systole

Objective 2 Size and Position of the Heart Size of the Heart ♥ About the size of a fist ♥ Average dimensions of an adult heart: 12 cm X 9 cm X 6 cm ♥ Average weight of the adult heart Males: 280-340 grams Females: 230-280 grams

Location of the Adult Heart ♥ Lies in the mediastinum ♥ 2/3rds to the left of the midline ♥ Medial to the lungs ♥ Directly posterior to the sternum ♥ Anterior to the esophagus ♥ of the heart lies at T5-T8 ♥ of the heart lies in the 5th intercostal space, about 9cm to the left of the body’s midline Base Apex Note: The location of the base and apex of the heart are counter intuitive!

Objective 3 The Pericardium The pericardium is a double walled sac that surrounds the heart. A. Structure Fibrous pericardium: superficial portion made of dense irregular connective tissue Functions: 1. Protects the heart 2. Anchors the heart to surrounding structures 3. Prevents overfilling of the heart

Serous pericardium: deeper serous membrane, composed of Serous pericardium: deeper serous membrane, composed of areolar connective tissue and mesothelium (simple squamous epithelium) which secretes pericardial fluid Parietal layer: lines the internal surface of the fibrous pericardium Visceral layer: adheres to the surface of the heart; is also called the epicardium Pericardial cavity: space between the parietal and visceral layer that contains pericardial fluid Functions: pericardial fluid lubricates surfaces and reduces friction

Pericardial Sac Intact Sac Cut Away

Objective 4 Tissues of the Heart Wall The tissues that make up the wall of the heart are organized into three layers: Layer Location Structure Function(s) Epicardium outer layer described in Cells secrete (Visceral pericardium) objective 3 serous fluid

Myocardium

Layer Location Structure Function(s) Myocardium middle layer cardiac muscle cells Cardiac muscle: (myocytes) held in place by contracts to eject blood collagen and elastic fibers into arteries (called the fibrous skeleton) Fibrous skeleton: stabilizes the position of valves and myocytes helps to distribute the force of contraction Adds strength and helps to prevent overdistention Helps to maintain the shape of the heart Provides elasticity Isolates atrial muscle cells from ventricular muscle cells

Vascular Supply to the myocardium: vessels of coronary circulation The heart is filled with blood, why does it need it’s own circulation?

Nerve Supply: Autonomic NS SNS: PNS: Cardiac Nerves increases rate and strength of contraction Vagus Nerve (X) decreases rate and strength of contraction

Layer Location Structure Function(s) inner layer which endothelium (simple maintains a smooth lines the squamous epithelium/ surface for blood ventricles and areolar connective flow covers valves tissue Endocardium

Objective 5 Structures of the Heart The heart has four chambers: Atria: superior chambers which receive deoxygenated blood from systemic circulation (right atrium) and oxygenated blood from the lungs (left atrium)  The atria are separated from each other by an interatrial septum Ventricles: inferior chambers which distribute deoxygenated blood to lungs (right ventricle) and oxygenated blood to systemic circulation (left ventricle)  The ventricles are separated from each other by an interventricular septum

8 of 39 : 18-04bGrossHeart_L.jpg                                                                                 8 of 39 : 18-04bGrossHeart_L.jpg Right and Left Atria: superior chambers ♥ are separated from each other by an interatrial septum What To Look For In The Atria: Auricle Crista terminalis Pectinate Muscles Fossa Ovalis   © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

Crista terminalis: location of the SA node

Patent Foramen Ovale

Attached Vessels: Right Atrium Left Atrium SVC, IVC pulmonary veins coronary sinus

Right Atrium: receives deoxygenated blood from systemic circulation Left Atrium receives oxygenated blood from pulmonary circulation

Right and Left Ventricles: ♥ they are separated from each other by an interventricular septum What to look for in the ventricles: Papillary Muscles Note: The left ventricular wall is thicker than the right ventricular wall The apex lies in the floor of the left ventricle Trabeculae Carneae

Right Ventricle Left Ventricle

Attached Vessels: Right Ventricle Left Ventricle pulmonary trunk aorta

Heart Valves ♥ The heart valves prevent blood from moving backwards Mnemonic for remembering order of valves: Try Pulling My Aorta (Tricuspid, Pulmonary, Mitral, Aortic)

Try before you buy! Tricuspid Valve Right Atrio-ventricular Valve Left Atrio-ventricular Valve Bicuspid Valve                                                                                                                                                                    Tricuspid Valve Lies between the right atrium Lies between the left atrium and the right ventricle and the left ventricle Also called mitral Try before you buy!

Mitral Valve

Valve Mechanism:

Semilunar Valves Pulmonary: lies at the base of the pulmonary trunk Aortic lies at the base of the aorta

Semilunar Valves

C. External Features of the Heart Base Apex Coronary Sulcus Anterior Interventricular Sulcus Posterior Interventricular Sulcus

Objective 6 Great Blood Vessels Superior Vena Cava (SVC): Carries deoxygenated blood from areas of systemic circulation above the diaphragm to the right atrium Inferior Vena Cava (IVC): Carries deoxygenated blood from areas of systemic circulation below the diaphragm to the right atrium

Pulmonary Trunk (Artery):. Carries deoxygenated blood from the Pulmonary Trunk (Artery): Carries deoxygenated blood from the towards the lungs Pulmonary Veins (4): Carries oxygenated blood from the lungs to the left atrium Aorta: Carries oxygenated blood from the left ventricle to systems of the body right ventricle

Objective 7 Circulation of Blood Through The Heart Superior/Inferior Systemic Body Tissues Vena Cava Circulation Right Atrium Left Ventricle (Through the Mitral Valve) Pulmonary Trunk/Arteries Left Atrium (Through the Semilunar Valve) Lungs Aorta (Through the Semilunar Valve) Right Ventricle (Through the Tricuspid Valve) Pulmonary Veins