A&P Chapter 11- Heart
Location and orientation within the thorax
*Base: superior (top) portion of heart* *Apex: 5th & 6th ribs inferior to left nipple* (point of cone) *Largest organ of the mediastinum*: • located between the lungs
Blood supply to the myocardium
*Blood in the heart provides little nutrients* Reason: *heart muscle is too thick to diffuse oxygen and nutrients* *Blood supply: coronary arteries* Left and right coronary arteries Origin: ascending aorta *Located: coronary sulcus*
Right coronary artery
*Branches into two main arteries* 1.*Marginal branch (side of the heart)* 2. *Posterior interventricular artery*
Circumflex artery:
*Follows coronary sulcus posteriorly* Supplies 1. *left atrium* 2. posterior left ventricle
Extrinsic innervation
*Heart rate: altered by external controls ANS* Cardiac centers: *located in the medulla oblongata* Cardio acceleratory center: *innervates SA and AV nodes, heart muscle, and coronary arteries through sympathetic neurons* Cardio inhibitory center: inhibits SA and AV nodes through parasympathetic fibers in the vagus nerves *Visceral sensory fibers: referred pain (heart attack)*
Marginal branch
*Supplies: right ventricle*
1. Great cardiac vein Three main vessels drain into coronary sinus
*anterior interventricular sulcus*
Anterior interventricular
*branches off LCA* *Descends to the anterior interventricular sulcus towards the apex of heart* Supplies 1. *Interventricular septum* 2. Anterior walls both left and right atria 3. Anterior walls left and right ventricles
• Ductus arteriosus:
*connects the pulmonary trunk and the aorta*
• Foramen ovale:
*connects the two atria (doorway)*
Atherosclerosis: Coronary artery disease - disorders of the heart
*fatty deposits build up on inner lining of arteries of the heart* • Blood flow decreases resulting in hypoxia (lack of oxygen) • Silent ischemia: blood flow interrupted without pain, no signs or symptoms • Symptom: angina pectoris (aka chest pain)
Atrioventricular (AV) node, AV bundle & branches
*near the tricuspid valve* Depolarization Rate: 40-60x min Location: inferior part of inter-atrial septum *Delay: transmission by about 0.13 second* Results: *allows atria to contract and empty blood prior to ventricles contracting* Travels: *impulse travels to AV bundle* *AV Bundle: located in the interventricular septum and connects to the left and right bundles branches*
Superior Reflexion: Pericardium
*the fold of the parietal layer toward the back side* point where parietal layer and visceral layer of the pericardium join
Myocardial infarction:
-*blocked coronary artery resulting in muscle tissue death* -1/3 of all cases result in immediate death
2. Serous pericardium:
-*double layered closed sac* Located: between fibrous pericardium Layers (one continuous layer) A. Parietal layer of serous pericardium • Attaches to inner surface of fibrous pericardium
Pericarditis: Clinical complications of heart muscle
-*infection and inflammation of pericardium leading to roughness of serous lining* Pericardial friction rub: beating heart produces creaking sounds Without treatment: heart can adhere to outer pericardial wall, scar, thicken and inhibit movement Causes: fungus, bacteria, virus, radiation, cancer, drug use
Embryonic heart development
-Begins as blood vessels: formed from concentrations of mesodermal mesenchyme Timeline • Day 20: pair of tubes fuse • Bulges develop along heart tube • Day 22: heart starts pumping • Day 24: heart bends into an S-shape • Atria remain connected by the foramen ovale until birth • Day 28: bending continues • Day 35: bending complete
Serous fluid: Pericardium
-approximately 50 ml serous fluid - lubricating film is found in the pericardial cavity
Internal structures Gross structures of the heart
1. *Two atria* (Receives from pulmonary and systemic circuits and pumps to ventricles) 2. *two ventricles* (Receives from atria and pumps to pulmonary and systemic circuits) 3. interventricular and interatrial septa
External structures Gross structures of the heart
1. Coronary sulcus (ditch between masses) 2. Anterior interventricular sulcus 3. Posterior interventricular sulcus
Embryonic heart chambers
1. Sinus venous 2. Atrium 3. Ventricle 4. Belbus cordis
Typical & Atypical- blood supply to the heart
15% of people have a LCA which provides both ventricular arteries 4% of people have a single coronary artery Generally, • *RCA supplies 35% of heart* • *LCA supplies 65% of heart* Collateral (*growth of additional blood vessels*) circulation 1. Vessels are occluded 2. *Vigorous exercise*
Left Side of Heart The pulmonary and systemic circuits
A. Left Atrium B. Left Ventricle C. Systemic Circuit (away from the heart to the body)
Right Side of Heart The pulmonary and systemic circuits
A. Right Atrium B. Right Ventricle C. Pulmonary Circuit (going to lungs)
2. Stenosis Heart valve dysfunction - two main categories
A. Valve opening becomes narrowed and leaflets become thick B. *Closing doesn't occur: valves always remain open* Causes: 1. *Rhematic fever* (follows 2-3 weeks after streptococcal infection) typically as a child 5-15 y.o. 2. *calcium deposits with age* 3. *Viral infection* 4. *Congenital deformation*
Pathway of blood through the heart (15 steps)
Begin oxygen-poor blood 1. Superior/Inferior Vena Cava & Coronary Sinus 2. Right Atrium 3. Right AV Valve (tricuspid valve) 4. Right Ventricle 5. Pulmonary Semilunar Valve 6. Pulmonary Trunk 7. *Pulmonary Arteries* 8. *Lungs (pulmonary)* 9. *Pulmonary veins (bright red)* 10. Left Atrium 11. Left AV Valve (bicuspid valve, mitral valve) 12. Left Ventricle 13. Aortic Semilunar Valve 14. Aorta 15. Body(systemic system)
Conducting system
Cardiac muscle tissue has intrinsic ability to: 1. *Generate and conduct impulses* 2. *Signal these cells to contract rhythmically* Conducting system • Defined:*a series of specialized cardiac muscle cells*
3. Endocardium (inside the heart) Layers of the heart wall
Composition: sheet of endothelium resting on a thin layer of connective tissue Location: *lines the internal walls of the heart and composes the heart valves*
The heart: description
Defined: a muscular double pump Composition: cardiac muscle tissue Shape: cone Size: a persons fist Weight: approximately 250-350 grams (5lb or 8-12 oz)
1. Fibrous pericardium: Pericardium (3 layers)
Defined: triple layered sac surrounding the heart -*sac's outer layer* Composition: *strong layer of dense connective tissue* Purpose(s): Attaches diaphram to roots of great vessels • Attaches heart in place • Holds heart in place • Keeps heart from overfilling
Heart failure Disorders of the heart
Defined:progressive weakening of the heart ventricles Results: cannot meet the body's demands for oxygenated blood Valves: can be associated with valvular disorder
SA node (pacemaker) - conducting system
Depolarization (intrinsic) rate: 75-100 bpm Location: lies in the posterior right atrial wall Appearance: visible with naked eye (pencil tip) Conduction:* impulse travels through atria via internodal pathways* Results: *atria contraction*
Left coronary artery
Divides into two main branches 1. *Circum flex artery* then branches off to 2. *Anterior interventricular artery*
Purkinje fibers - conducting system
Location: bifurcate off the bundles branches half way through the interventricular septum Characteristics: atypical cells- large Location: *spread throughout the ventricles* Results: *contraction of ventricles* *Ventricle contraction: begins at the apex*
General characteristics of left atria
Location: left posterior aspect of heart Receives blood: *4 pulmonary veins* *Sends blood: left ventricle* Muscular Wall: *~1/8 inch thick* Externally: left auricle (appendage) - remnant of embryonic dev. Internally: *few musculi pectinate and mostly smooth*
General characteristics of the right atria
Location: right upper border of the heart Receives blood: superior and inferior vena cava and coronary sinus Sends blood: right ventricle *Muscular wall: <1/8 in (thinnest of all chambers)* right ventricle Externally: *right auricle (appendage)* - remnant of embryonic development *(fatty flap)*
Right coronary artery (RCA) - blood supply to the heart
Originates: right side of ascending aorta Travels: descends coronary sulcus on anterior surface of heart between right atrium and right ventricle Supplies 1.* Most of right ventricle* 2. Posterior side of the left ventricle and right atrium *Branches into two main arteries* 1.*Marginal branch (side of the heart)* 2. *Posterior interventricular artery*
Fetal Heart Circulation
Oxygen supply: mother supplies oxygen thus certain fetal heart structures allow blood to bypass pulmonary circulation Remnants: structures are nonfunctional in an adult heart
Treatment: cardiac tamponade
Pericardial Centesis • *Hypodermic needle inserted into pericardial cavity* • Between 5th and 6th intercostal space • *Drain cavity of excess fluid* Other causes • Wounds or accidents *Hemopericardium: fills with blood (blood in the pericardial sac)*
Cardiac veins Veins of the heart
Purpose: *carry deoxygenated blood from the heart wall to the right atrium* Location: sulci of heart
AV valve function
Purpose: *prevent regurgitation of ventricle blood* Operation: pressure gradient *Chordae tendinae attaches to:* • *3 papillary muscles (tri) Right side* • *2 papillary muscles (bi) left side* • Flaps of heart valves *closes the doors/stings stop the door from going too far (pulling a rope tightly)*
Coronary sinus (largest vein)
Purpose: *return most venous blood to the right atrium* Location: posterior part of coronary sulcus
Heart rate and cardiac cycle
Resting heart rate and associated terminology • Typically: 60-80 beats/minute • Conditioned: <60 bpm • *Tachycardia: abnormally fast heart rate (>100 bpm)* • *Bradycardia: heart rate slower than 60 bpm*
Cardiac tamponade (heart plug)
Severe acute case of pericarditis • *Inflammation of tissue and filling of pericardial* cavity with large amounts of fluid Results: *fluid compresses heart and limits expansion which leads to*: 1. *Decreased filling* 2.*Decrease expulsion* Sign:veins in face and neck expand and engorge *(back up of blood)*
Left coronary artery (LCA) - blood supply to the heart
Size: 1/2-1 in length (typically width of pulmonary trunk) Originates: *left side of ascending aorta* Travels: passes posterior to pulmonary trunk Divides into two main branches 1. *Circum flex artery* then branches off to 2. *Anterior interventricular artery*
Papillary muscle
The papillary muscles attach to the lower portion of the interior wall of the ventricles. *They connect to the chordae tendineae.* *The contraction of the papillary muscles opens these valves. When the papillary muscles relax, the valves close.*
Posterior interventricular artery: continuation of RCA
Travels: along the posterior interventricular sulcus Supplies: *posterior interventricular septum* *Anastomosis*: posteriorly with circumflex and anterior interventricular artery
Semilunar valves
Two valves 1. *Pulmonary semilunar valve (going to lungs)* 2. *Aortic semilunar valve (going to Aorta)* Purpose: Prevent regurgitation to the ventricle Operates: Pressure gradient Space behind valves prevents sticking to walls of arteries • *Pulmonary sinus(prevents from door opening)* • *Aortic sinus*
General blood volume characteristics of the ventricles
Volume: each ventricle holds ~125 ml *(1/2 cup) blood* *Stroke volume:amount of blood ejected per beat* (~70 ml bld/beat at rest) Remaining: ~40-50 ml Rest HR: = ~72beats/minute Body volume of blood: *~5 liters* *Cardiac Output= HRxSV*
1. Sinus Venarium Internal structures of right atria
a) Appearance: smooth b) Location: posterior lateral surface
2. Pectinate Muscles (Musculi Pectinati) Internal structures of right atria
a) Purposes (rough side next to sinus venarium) 1) Increase surface area 2) *Conduct impulses*
Congestive heart failure: heart enlarges
a.k.a. dilated cardiomyopathy Results: pumping efficiency declines Cause: unknown Hypothesis: positive feedback loop-weak heart, sympathetic tone increases HR, further weakening the heart
3. Crista Terminalis Internal structures of right atria
barrier between 1 and 2 ^
Anastomosis
defined: natural junction between two vessels connecting or putting together two vessels
3. Small cardiac vein
heart inferior right margin RCA
Anterior cardiac veins:
horizontal and drain directly into right atrium
2. Middle cardiac vein
posterior interventricular sulcus
PericardialCavity: Pericardium
space between parietal and visceral layers Purpose: *holds serous fluid necessary to reduce friction while beating*
3. Pancarditis
• *Inflammation of all three layers simultaneously*
2. Endocarditis
• *Inflammation of endocardium* • Fatal if not treated quickly Causes *viral infection* *bacterial infection*
2.Myocardium (cardiac muscle) Layers of the heart wall
• *Majority of heart* • Elongated *muscle cells* arranged in circular and spiral patterns • Blood: squeezed (ringed) [like a towel when wet] From atria: superior to inferior From ventricles: inferior to superior
4. Fossa Ovalis: depression Internal structures of right atria
• *Small remnant of a fetal opening (foramen ovale)* • Blood circulation prior to birth (rt. and lt. atrium)
1. Incompetence Heart valve dysfunction - two main categories
• *Valve can no longer prevent back flow* Example: prolapse • *Valve flaps extend beyond normal closing* Cause(s) (various) 1. Chordae tendeneae too long 2. Papillary muscle doesnt contract correctly 3. Bacteria infection
Systole Cardiac cycle (two parts)
• Cardiac muscle contraction • Emptying of the heart chambers
Diastole Cardiac cycle (two parts)
• Cardiac muscle relaxation • Filling of the heart chambers
Heart muscle destruction
• Directly: weakening of heart • Indirectly: damaging the conduction system
3. Visceral layer of serous pericardium (epicardium)
• Located on heart muscle wall • Considered part of heart wall
1. Atrioventricular(AV)valves(two) Heart valves - four
• Located: between atria and ventricles • *Right side: a.k.a. tricuspid* • *Left side: a.k.a. bicuspid or mitral*
2. Aortic and pulmonary semilunar valves (two) Heart valves - four
• Location: *between ventricles and great arteries* Composition: • *Endocardium with connective tissue core*
1.Epicardium (upon the heart) Layers of the heart wall
• Visceral layer of the serous pericardium • Contains a fat layer usually in older persons
Right Ventricle Anatomical structures of the ventricles
• Wall: *~1/4 in thick* Internal Structures • *Trabeculae Carneae: high ridges of muscle tissue* • *Conus Arteriosus: smooth parting exiting chamber* • *Papillary muscle* • *Chordae Tenineae (heart strings)*
Left Ventricle
• Wall:* ~3/4 in thick* Internal structures: • Trabeculae Carneae • *Aortic Vestibule: smooth part exiting chamber* • Papillary Muscle • Chordae Tendinae
1. Myocarditis Clinical complications of heart muscle
•*Inflammation of heart muscle* Causes viral infection Parasites poison Radiation excess alcohol Fungus Bacterial infection
Heart sounds (What you hear?)
"Lub-dup" sound 1. *First sound: "lub"-the Atrial Ventricular (tri and bi) valves closing* • *Beginning of systole* 2. *Second sound: "dup"-the Semilunar valves closing* • *Beginning of ventricular diastole* *Heart murmurs:* abnormal heart sounds are most often indicative of valve problems