Heart divided into 4 chambers. 2 atria – upper chambers, thin- walled; receive blood returning to heart. 2 ventricles – lower chambers, thicker walled; pump blood into arteries.
Septum divides atrium and ventricle on right from left side. R atrium receives blood from body from inferior vena cava and superior vena cava. R atrium separated from R ventricle by tricuspid valve.
Developing fetus - hole between L and R atria. After birth - hole supposed to close. If hole does not close - hole in heart (atrial septal defect) Blood enters lungs - breathing problems.
Chordae tendineae – attach cusps of tricuspid valve. Originate from papillary muscles on walls of ventricles. R ventricle pumps blood through pulmonary artery to lungs. Pulmonary valve leads into artery.
* L atrium receives blood from lungs through pulmonary vein. L atrium and L ventricle separated by bicuspid (mitral) valve. L ventricle pumps through aorta to entire body. Aortic valve leads into aorta.
Mitral valve prolapse – one or both cusps stretch and bulge into L atrium during contraction. Results in blood going back into L atrium.
Blood flow Blood low in O 2, high in CO 2 enters R atrium. R atrium passes blood into R Ventricle. R ventricle contracts, blood flows into pulmonary artery (to lungs) Pulmonary vein brings blood high in O 2 back to L atrium.
Blood passes to L ventricle. Pumped through aorta to body. 1 st 2 branches of aorta – R,L coronary arteries – supply blood to heart tissue. Cardiac veins – drain blood, join together to form coronary sinus – dump into R atrium.
Cardiac cycle Heart sounds made from opening and closing of valves. 1 st sound made from recoil of blood against closed AV valves (“lub”) 2 nd sound made from recoil of blood against semilunar valves. (“dup”) Heart murmurs result of incomplete valve closure resulting in swishing noise.
Sinoatrial node (SA node) – generates action potentials on its own (pacemaker). Impulse passes along fibers to mass of specialized tissue (atrioventricular node)
From AV node, moves through bundle of His (AV bundle) Divide into L and R branches underneath endocardium. Give rise to Purkinje fibers. Causes ventricular walls to contract.
ECG Electrocardiogram – recording of electrical changes in heart muscle. QRS complex – depolarization of ventricular fibers (ventricles contract) T wave – ventricular fibers repolarize.
Heart rate – duration of cardiac cycle. Stroke volume – volume of blood ejected from ventricles during contraction. Cardiac output = heart rate X stroke volume.
More cells stretched by incoming blood, more strongly heart walls contract to eject blood – Starling’s law of the heart. Cardiac output increases with increasing exercise and blood flow.
Heart rate monitored in medulla oblongata of brain. Increase in blood pressure – stretch sensors send message to brain to slow heart rate down.
Blood vessels Arteries – carry oxygenated blood away from heart. Branch into arterioles, then capillaries. Artery – 3-layered wall surrounding interior (lumen).
3 Blood volume – decrease causes drop in b.p. Sympathetic nervous system – causes rise in b.p, heart rate. Parasympathetic – decrease.
Hormones regulate b.p. Epinephrine, norephinephrine – rise, fall of b.p. Antidiuretic hormone – rise in b.p. Kidneys aid in regulation – drop in b.p. releases renin; renin causes formation of angiotensin.
Circulatory Pathways 1 Pulmonary circulation – pulmonary trunk carries blood from R ventricle. Divides into R and L pulmonary artery, into capillaries. O 2 picked up in lungs, brought back to heart via pulmonary veins.
Arteries 2 Systemic – blood leaves L ventricle into ascending aorta. Branches into R, L coronary arteries (supply heart wall). Aorta curves to back (aortic arch) 3 branches – brachiocephalic, L common carotid, L subclavian.
Branches into celiac artery (liver, spleen, stomach, pancreas), superior mesenteric artery (small intestine), suprarenal arteries (adrenal glands), renal arteries (kidneys), inferior mesenteric artery (large intestine). Divides into R, L iliac (to lower legs)
Pelvis, lower limbs – common iliac divides into internal, external iliac. External iliac – becomes femoral. Forms deep femoral artery (flexor muscles of thigh), popliteal artery (knee), anterior, posterior tibial arteries.
Head, neck – from common carotid, subclavian. R common carotid arises from brachiocephalic. R, L common carotid branch into external, internal carotid.
Shoulder, upper limbs – from subclavian. Axillary artery – near armpit. Continues down arm as brachial artery; divides into ulnar, radial arteries.
Veins Head, face veins – blood drained into R, L external jugular. Merge with subclavian veins internal jugular brachiocephalic vein superior vena cava.
Upper limbs – ulnar, radial vein brachial vein axillary vein. Major superficial arm veins – basilic (forearm to middle of upper arm), cephalic (wrist to shoulder), median cubital vein (where blood is drawn).
Inferior vena cava – longest vein in body – great saphenous vein, joins with femoral vein. Abdomen – hepatic portal system – blood from capillaries of digestive tract to liver only. Dumps blood into superior, inferior mesenteric veins.
Diseases 1 Congestive heart failure – can’t pump blood to body. Bad circulation to body increased pressure, fluid leaking in lungs. Caused by damage to cardiac muscle. Symptoms – shortness of breath, swelling in lower legs.
2 Hypertension – increase in blood pressure. Due to narrowing of blood vessels (atherosclerosis) or hardening of vessels (arteriosclerosis)
3 Endocarditis – infection of lining of heart due to bacterial infection. Can cause embolus (blood clot) 4 Aneurysm – sac formation in vessel or heart chamber; can produce tear in vessel (hemorrhage)