Anatomy and Function of the Heart Overview Double

Anatomy and Function of the Heart • Overview: Double Pump • Goal: Push blood through vessels • Atria and Ventricles, Heart Valves, Great Vessels • Fetal Circulation • Cardiac Muscle and Heart Attacks • Control of Heart Rhythm Larry M. Frolich, Ph. D. , Yavapai College

Overview—Double Pump • Pulmonary Circuit: Right side of heart pumps blood to lungs to pick up oxygen • Systemic Circuit: Left side of heart pumps blood to rest of body to deliver oxygen • Schematic does not show left/right symmetry for most of circulatory system

Goal—push blood through vessels to capillaries • Pulmonary circuit—right side of heart pumps blood through pulmonary arteries to capillaries • Oxygen diffuses into blood and RBC’s in lungs at alveoli surrounded by capillaries • Pulmonary veins return blood to left side of heart • • Systemic left side of heart pumps blood through systemic arteries to capillaries Oxygen diffuses out of blood and into interstitial fluid around cells making oxygen available for cellular metabolism. This is the grand goal of the circulatory system—where the real action happens Besides oxygen, water, glucose and other nutrients are delivered; CO 2, waste products are picked up Systemic veins return blood to right side of heart

Heart Board Drawing • • • Apex Ventral view—ventricles Interventricular sulcus—between right and left ventricles Right ventricle leads right into pulmonary trunk (to lungs) Left ventricle leads into aorta (to systemic circulation) emerging behind pulmonary trunk • Auricle of right atrium • Pulmonary veins entering right atrium on posterior surface • IVC, SVC enter left atrium on posterior surface

Another View

Right Atrium • Receives low O 2 veinous blood from body (return of systemic circulation – Superiorly SVC (superior vena cava – Inferiorly IVC (inferior vena cava) – Thin muscular wall • At atrial systole, the right atrium contracts pushing blood into right ventricle passing through open right A-V valve (tricuspid valve) • Fossa ovalis is remnant of foramen ovale that shunts fetal blood into left atrium

Right Ventricle • • • Receives blood passing through open A-V valve from right atrium At ventricular systole, the right ventricle contracts pushing blood into the pulmonary trunk passing through the open right semi-lunar valve (pulmonary valve) As the ventricle begins to contract, the blood pushes against the cusps of the A-V valve causing it to snap shut preventing blood from backflowing into the right atrium (“lub…”) The papillary muscles then contract and pull on the chordae tendinae attached to the valve cusps so they don’t get overextended into the atrium As ventricle relaxes into diastole, the right semilunar valve (pulmonary valve) snaps shut keeping blood from back-flowing back into the ventricle (“…dub”)

Left Atrium • Receives high O 2 veinous blood from lungs (return of systemic circulation – Pulmonary veins— 2 from left lung, 2 from right lung • At atrial systole, the left atrium contracts pushing blood into left ventricle passing through open left A-V valve (bicuspid or mitral valve)

Left Ventricle • • • Receives blood passing through open A-V valve from left atrium At ventricular systole, the left ventricle contracts pushing blood into the aorta passing through the open left semi-lunar valve (aortic valve) As the ventricle begins to contract, the blood pushes against the cusps of the A-V valve causing it to snap shut preventing blood from backflowing into the left atrium (“lub…”) The papillary muscles then contract and pull on the chordae tendinae attached to the valve cusps so they don’t get overextended into the atrium As ventricle relaxes into diastole, the left semilunar valve (aortic valve) snaps shut keeping blood from back-flowing back into the ventricle (“…dub”)

Animation of heart and blood flow

• Fetal Circulation • No circulation to lungs—why? – Foramen ovale shunts blood from right atrium to left atrium – Ductus arteriosum shunts blood from pulmonary artery to aortic arch • Circulation must go to placenta – Umbilical aa. , vv.

Fetal Circulation

Adult remnants of fetal circulation Adult Fetus Fossa ovale Foramen ovale Ligamentum arteriosum Ductus arteriosus Medial umbilical ligaments Umbilical aa. (within fetus) Round ligament (ligamentum teres) of liver Ligamentum venosum Umbilical v. (within fetus) Medial umbilical ligament Umbilical cord (leaving fetus) Ductus venosus

Coronary arteries and circulation to the heart • • • Coronary arteries supply blood to heart muscle Come directly off of aorta as it leaves the heart from large high pressure aorta to small left and right coronary arteries Heart attack is loss of blood supply to heart muscle Blockage usually occurs in first two centimeters of coronary arteries Treatment can be angioplasty, stint, bypass

Cardiac Muscle A and P I Tissue Review— 3 types of muscle tissue • • • Usually 1 nucleus, sometimes several Much thinner than skeletal muscle (20 um versus 100 um) Intercalated disks pass action potential from cell to cell—most cells have no direct motor neuron connection Energy source is mostly lipids Calcium to trigger actin-myosin cross-bridge formation and muscle cell contraction comes from outside cell as part of action potential as well as from sarcoplasmic reticulum

Control of heart rhythm • Heart receives visceral motor innervation – Sympathetic (speeds up) – Parasympathetic (slows down) • Input is from chemoreceptors and baroreceptors

Input on blood pressure to brain • Chemoreceptors – aortic bodies, carotid bodies – Sense CO 2, p. H, O 2 • Barroreceptors – stretch receptors sense blood pressure pushing on vessel wall – aortic sinus, carotid sinus Bonus A and P I Review: Cranial Nerve that carries aortic receptor input to brain? X. Vagus Cranial Nerve that carries carotid receptor input to brain? IX. Glossopharyngeal

Reflexive output: heart rate • Baro- and chemo-receptor input arrives to medulla oblongata (A and P I review!) • Autonomic motor output (A and P I review) to AV node of heart – Sympathetic will speed heart rate (where do sympathetic neurons originate? What is path to heart? – Parasympathetic will slow heart (where do parasympathetic neurons originate? What is path to heart? ) • Bonus (common sense physiology!): Will blood vessels constrict or dilate with sympathetic response? A and P I Review Sympathetic = “fight or flight” = NE (norepinephrine) Parasympathetic = calming = ACH (acetylcholine)

Electrocardiogram • Surface electrodes measure sum total of action potentials in cardiac muscle • Distinct wave forms for atrial, ventricular depolarization • Intervals as well as wave forms important in interpretation Demo in Lab

Location of Heart in Thorax Heart Dissection Lab