Heart Anatomy Notes PDF

# The Heart The heart is a muscular double pump with 2 functions: 1. **Right side:** recieves oxygen poor blood from the body tissues and then pumps this blood to the lungs so it can pick up oxygen and get rid of CO₂ * **Pulmonary circuit:** blood vessels that carry blood to and from the lung...

# The Heart The heart is a muscular double pump with 2 functions: 1. **Right side:** recieves oxygen poor blood from the body tissues and then pumps this blood to the lungs so it can pick up oxygen and get rid of CO₂ * **Pulmonary circuit:** blood vessels that carry blood to and from the lungs 2. **Left side:** recieves oxygenated blood (returned from lungs) then pumps this blood throughout the body to supply oxygen & nutrients to the body tissues * **Systemic circuit:** vessels that transport blood to and from all body tissues and back to the heart * The heart has 2 recieving chambers: **right** and **left atrium** they recieve blood that's returning from the pulmonary & systemic circuits. It also has two main pumping chambers: **right** and **left ventricle**, that pump blood around the two circuits. ## Location within the thoraxi * heart lies in the thorax posterior to sternum and costal cartilages. * and rests on the superior surface of the diaphragm * largest organ in the mediastinum * assumes an oblique position * pointed apex, lies to the left of the midline and anterior to the rest of the heart * heart's base is its broad posterior surface ## Structure of the heart ### Coverings * **The Pericardium** is a triple layer sac that encloses the heart * **Fibrous Pericardium** (outer layer): strong layer of dense CT * adheres to diaphragm inferiorly, superiorly it's infused to the roors of the great vessels * **acts as a tough outer coat that holds the heart in place and keeps it from overfilling w/blood** * **Serous Pericardium:** double layered, enclosed sac sandwiched between fibrous pericardium & heart * **Parietal layer:** adheres to the inner surface of fibrous Pericardium * **visceral layer** (epicardium): lies on the heart and is considered tobe part of the heart wall * **Pericardial cavity:** Inbetween parietal & visceral layers, a division of embryonic coelom * **fluid in serous pericardium reduces friction between beating heart & outer wall of pericardial sac** ### Layers of the heart wall * heart wall has 3 layers, all richly supplied w/ blood vessels. 1. **epicardium:** (superficial) visceral layer of serous pericardium, often infiltratedw/ fat, especially in older people 2. **Myocardium:** (middle) the bulk of the heart. made up of cardiac muscle tissue, & is the layer that contracts. 3. **Endocardium:** (inner) deep to myocardium, sheet of simple squamous epithelium resting on a thin layer of CT. lines heart chamber & covers heart valves ### Heart Chambers * 4 heart chambers * **left atrium** * **left ventricle** * **right atrium** * **right ventricle** * **Interatrial septum:** divides heart longitudinally between atria * **Interventricle septum:** clivides the ventricles * **boundaries of heart chambers are marked by two grooves** * **coronary suicus:** honzuntal, circles boundaries between atria and ventricles. * **anterior interventricular sulcus:** extends vertically marking anterior Position of interventricular septom * **Posterior interventricular SUICUS:** seperates 2 ventricles, on heart's inferior surface * **Right Atrium:** recaeving chamber for oxygen-poor blood returning from the systemic circuit * recieves blood from 3 veins: 1. Superior vena cava 2. Inferior vena cava 3. Coronary sinus * **right auricle:** small flap that projects anteriorly from superior corner of the atrium... * **Internally atrium has 2 parts: smooth walled posterior and an anterior part lined w/ ridges** * **Pectinate muscles** * **crista terminalis:** C-shaped ridge that seperates the two parts of the atrium * **helps locate sites where veins enter right atrium** * **Right atrium opens into right ventricle through the tricuspid valve** * **Right ventricle:** (anterior surface) recreves blood from right atrium then pumps it into the pulmonary circut through pulmonary trunk * **there are Papillary muscles that project from the walls into the ventricular cavity** * **Chordae Tendineae.** strong bands that project superiorly from papillary muscle to the flaps of the tricuspid * **opening between the RV & pulmonary trunk contains the Pulmonary valve** * **Left Atrium:** recieves oxygen rich blood returning from the lungs through 2 right & 2 left Pulmonary veins * **opens into LV through the mitral valve** <start_of_image> Schematic diagram of the heart showing the flow of blood <start_of_image> circulatory system * **Left ventricle:** forms apex & dominates inferior surface......... pumps blood into systemic system. * **opens into stem artery of the systemic circulation (aorta) through the aortic valve** ## Heart valves * **Valve structure** * Valves enforce the one way flow of blood throug the heart * Each valve has 2 or 3 cusps * flaps of endocardium reinforced by cores of dense CT * **Atrioventricular valves** * **right atrioventricular (Tricuspid) valve.** has three cuspsit * **left atrioventricular (bicuspid) valve:** only has 2 cusps * also called the Mitral valve because the cusps look like the two sides of a bishop's hat * **aortic & pulmonary valves:** located @ the junctions of the ventricles & greater arteries, each has 3 cusps * **cardiac skeleton:** lies in the plane between atria and the ventricles and surrounds all. 4 heart valves * **has 4 functions.** 1. anchors valve cusps 2. prevents overdilation of the valve openings as blood travels through them 3. Point of attacriment for bundies of cardiac muscle in the atria and ventricles 4. block directs spread of electrical impulses from the atria to the ventricles * Critical for maintaing coordination of atrial and ventricular contractions * **Valve function..** * **valves open to allow blood flow** * **Valves close to prevent backflow of blood** * **atrioventricular valves prevent backflow of blood into the atriaduring contraction of ventricles.** * **Semilunar valves prevent backflow from the Great Arteries. into the ventricles** ## Heart Sounds * "lub dub" * **"lub" = closing of Av valves @start of ventricular contraction** * **"dub" = Closing of semilunar valves. @end of ventricular contradiction** ## Pathway of blood through heart * **Deoxygenate blood from body enter ing inferior & Superior venacava** * **Right Atrium** * **Contracts trough Tricuspid valve** * **right ventricle** * **Contracts through pulmonic valve** * **Pulmonary Artery** * **Tungs** * **oxygenated blood from lungs through Pulmonary veins** * **left Atrium** * **Contracts blood through Mitral valve** * **left ventricle** * **Contracts & ejects blood through Aortic valve** * **Aorta** * **Body** ## Heartbeat * **heartbeat:** single sequence of atrial contraction followed by ventricular contraction * av. resting heart rate. 70-80 bpm * **Systole:** contraction of a heart chamber * **Diastole:** time when the heart chamber is relaxing and filling With blood ## Cardiac Muscle Tissue * **Structure of Cardiac Muscle** * cardiac muscle tissue: forms thick myocardium of heart wall * contractions of cardiac muscle cells pump blood through the neart and into & through blood vessels * Striated muscle, contracts by sliding filament mechanism * Carcliac muscle cells are short, branching cells with one or two large & Central nuciel: branching networks of cardiac muscle cells are called cardiac myofibers * **Intercalated Discs:** complex junctions that join cardiac muscle cells * **Sarcole mimas of adjacent cells interlock through meshing "fingers" Two distinct regions:** * **fasciae Adherens:** transverse regions have desmosome-like junctions, they bind adjacent cells together and transmit the contractile force to adjacent cells * **longitudinal regions have gap junctions that let lons pass between cells.** ## Conducting System & Innervation ### Conducting System * cardiac muscle cells have an intrinsic ability to generate and conduct electrical impulses to contract rhythmically. * intrinsic to heart muscle and doesn't depend on external nerve impulses * **conducting system:** Series of specialized cardiac muscle cells that carries impuises throughout the heart's musculature, signaling chambers to contract in a proper sequence * sets basic heart rate * **the impulse that signals each heart beat starts@ Sinoatrial (SA) node** * **heart's pacemaker** ### Innervation * heart rates can be alteredby extrinsic neural controls. * **Parasympathic : nerves to the heart arise as branches of the vagus nerve in the neck and thorax** * **parasympathetic innervation decreases heart rate & is restricted to the SA and Av nodes and the coronary arteries** * **Sympathetic nerves travel to the heart from the cervical upper thoracic chain ganglia** * **Innervate same structures as the parasympathetic fibers.→ increases heart rate and strength of contraction** ## Blood Supply to the heart * **Coronary Arteries** * **left coronary artery (LCA): arises from the left side of the aorta, passes posterior pulmonary trunk.** * divides into 2 branchies * **anterior interventricular artery:** descends into anterior interventricular Sulcus towards apex of heart * sends branches into and supplies the Interventricular septum and anterior walls of both ventricles. * **circumfiex artery:** follows coronary sulcus posteriorly & supplies. the left atrium & posterior part of LV * **Right coronary arterty (RCA): emerges from the right side of the aorta and descends in the coronary sulcus on the anterior surface of the heart, between RA and RV** * **Marginal artery:**