THE HEART Position of the Heart human heart

THE HEART

Position of the Heart � human heart is about the size of a fist � lies in the thoracic cavity w/in the mediastinum (area from sternum to vertebrae, between the lungs) � tilted @ angle so its inferior surface lies against the diaphragm

Parts of the Heart Base of the heart is its superior border � Apex of the heart is lowest point �

Major Heart Structures: the Pericardium � Outer Layer: Fibrous Pericardium �tough, attaches to diaphragm � Inner Layer: Serous Pericardium �dbl membrane: ○ outer parietal: attaches to fibrous pericardium ○ inner visceral layer: covers cardiac muscle �between the 2: pericardial cavity filled with serous fluid

Wall of the Heart � 3 layers 1. outer epicardium � same as visceral pericardium 2. middle myocardium � cardiac muscle 3. inner endocardium � thin layer of endothelium that lines inside chambers of the heart & valves

Surface Features of the Heart � 4 chambers of heart: � 2 atria form the base ○ Auricles (ear-like) pouch-like extensions �tip of left ventricle forms the apex �Sulci: grooves where coronary blood vessels & adipose tissue that externally mark the boundaries between the 4 heart chambers ○ coronary sulcus: separates atria from ventricles ○ anterior & posterior interventricular sulcus: separate 2 ventricles

Right Atrium � Receives deoxygenated blood from SVC & IVC

Right Atrium � inside surface has honeycombed appearance & ridges called pectinate muscles � wall separating rt & lt atrium= interatrial septum: in fetus hole called foramen ovale (blood shunts from rt atrium lt atrium avoiding pulmonary circulation); when scarred over called fossa ovalis

Right Ventricle receives blood from right atrium � sends blood to pulmonary trunk lungs to be oxygenated �

Right Ventricle � inside has ridges of muscles called trabeculae carnae: largest ones called papillary muscles: have string-like cords called cordae tendinae

Right Ventricle � separated from left ventricle by: interventricular septum

Left Atrium receives oxygenated blood thru 4 pulmonary veins � delivers blood to left ventricle � seen on posterior surface of heart �

Left Atrium � thin-walled � identifiable entering it characteristic: 4 pulmonary veins

Left Ventricle � receives oxygenated blood from left atrium � sends blood to systemic circulation thru Aorta � has thickest muscle (pumps blood the farthest)

4 Heart Valves � control 1 -way flow of blood � 2 AV valves �between atria & ventricles �Tricuspid : rt AV valve �Mitral : lt AV valve, aka bicuspid � 2 semilunar valves �blood exits rt ventricle thru Pulmonary (semilunar) valve �blood exits lt ventricle thru Aortic (semilunar) valve

AV Valves � Tricuspid valve � Mitral Valve

Semilunar Valves � Pulmonary Valve � Aortic Valve

Blood Flow thru the Heart � thinner walled atria receive blood returning to heart from veins � pressure of blood in filled atria opens the AV valves & most of the blood flows into ventricles � both atria contract simultaneously to pump remaining blood into ventricles

Blood Flow thru the Heart � when atria have stopped contracting AV valves close � Ventricles contract together forcing semilunar valves open � walls of left ventricle thicker providing more force to pump blood thru systemic circulation

Blood Flow thru the Heart � Ventricular Systole: �when both ventricles are contracting �AV valves close �Semilunar valves open � Ventricular Diastole: �when both ventricles relaxed �Semilunar valves close �AV valves open

Cardiac Cycle

Systemic & Pulmonary Circulation

Heart Animations � http: //www. nhlbi. nih. gov/health//dci/Disease s/hhw_pumping. html � http: //www. hybridmedicalanimation. com/w ork/animation/beating-heart-with-bloodflow/

Heart Sounds � Auscultation: listening to body sounds � 1 heartbeat produces 2 heart sounds: lub-dub � heart murmurs: abnl heart sounds usually due to valve abnl � http: //www. blaufuss. org/tutorial/index 1. html

Heart Sounds � http: //www. dnatube. com/video/9217/Review -of-heart-sounds � http: //familymedicine. osu. edu/products/phys icalexam/flash/heart 2. cfm � http: //www. blaufuss. org/tutorial/index 2. html

Pulse � when ventricles contract a blood pressure wave is produced that travels in the arteries and can be felt as your pulse � radial pulse: check over radial artery � carotid artery pulse: check over carotid artery

Calculate Pulse � Count the # of beats in 15 s and multiply x 4 � If the math is too difficult count for 30 s and multiple x 2

Blood Pressure � pressure exerted by blood against blood vessel walls � highest in the aorta & large elastic arteries & decreases as arteries get smaller & further from heart

Systolic Blood Pressure � top # on a BP � pressure generated by ventricular systole � normal adult: ~120

Diastolic BP � bottom # on BP � pressure exerted during ventricular diastole � normal adult: 60 - 80

Arterial Blood Pressure � normal adult ~ 120/80 � normal venous BP: ~16 mm Hg

BP Measurement � Sphygmomanometer: BP cuff � usually use brachial artery � use correct size cuff

BP � pump used to inflate cuff to a pressure > the systolic pressure: �puts pressure on the artery, flattens it, & stops blood flow in the artery �pressure slowly released from cuff as stethoscope used to auscultate over brachial artery

BP � reported in mm Hg � as pressure in cuff becomes < pressure in artery…examiner will hear a sound can be heard, caused by the turbulent flow of blood as artery goes from flattened normal