Anatomy of the Heart-Mediastinum
THORAX
ANTERIOR MEDIASTINUM AND HEART
(MIDDLE MEDIASTINUM)
Mediastinum
Superior
Inferior : anterior, middle, posterior
Anterior Mediastinum
Posterior to sternum and anterior to pericardium
Contains fat, sternopericardial ligaments, thymus
Middle Mediastinum
Space bounded by pleura containing pericardium, heart, & phrenic nerve
Phrenic nerve [N.182]
From anterior rami of C4 (C3, C5)
Contains postganglioinc symp. axons
Provides motor and sensory nerves to diaphragm
Provides sensory nerves to pericardium
Pericardiacophrenic vessels accompany phrenic n.
Heart
Pericardium [N.200]
Fibrous pericardium
Tough conn. Tissue sac containing heart
Not distensible, heart can be compressed if pericardial sac fills up
Attached to diaphragm inferiorly and wall of great vessels superiorly
Lined with parietal layer of serous pericardium
Heart with visceral layer of serous pericardium = epicardium, allows heart to move freely in epicardial sac
Oblique pericardial sinus
Transverse pericardial sinus
External Anatomy of Heart [N.201 & M.56]
Anterior surface: right ventricle, right atrium, right auricle, let auricle, left ventricle, ant. interventricular sulcus, coronary sulcus
Posterior surface
Least mobile portion of heart
Left atrium, pulmonary veins, right atrium
Apex: most ant. and infer. Portion of left ventricle, most mobile
Right Border
Right atrium, superior and inferior vena cava
Left Border
Aorta, pulmonary trunck, left auricle, left ventricle
Sulci
Interventricular sulcus- between ventricles
Coronary sulcus- between atria and ventricles
Surface projections (expiration)
1/3 of heart projects to right midline
2/3 projects to left
apex projects to 5th intercostals space near mid clavicular line
left margin projects to 2nd intercostals space hear sternum
inferior margin projects to 6th costal cartilage and 5th intercostals spece left of sternum
right margen projects from 3rd to 6th costal cartilage right of sternum
Blood Supply of Heart
Coronary Arteries [N.204]
From ascending aorta
Left coronary artery, anterior interventricular branch runs in the ant. interventricular sulcus supplies the interventricular septum, AV bundle, R &L ventricles circumflex branch runs in the coronary sulcus gives off left marginal branch supplies the posterior left ventricle.
Right coronary artery
Runs in the coronary sulcus
Gives off right marginal branch
Ends in post. Interventicular artery in sulcus
Forms anastomosis with anterior interventicular artery
Supplies AV and SA nodes and right ventricle
Cardiac Veins [N.204]
Anterior Cardiac Veins
Ant. surf. Of right ventricle
Cross coronary sulcus
Enter right atrium
Smallest Cardiac Veins
Drain from myocardium into chambers of heart
Not on external surface
Most in right atrium and ventricle (none in left ventricle)
Coronary Sinus
Large vein, muscle fibers in wall
Majority of posterior coronary sulcus
Beneath left atrium
Term in right atrium
Receives all cardiac veins except for above
Great cardiac vein
Begins at apex
Occupies ant. interventricular sulcus
Continuous with coronary sinus, post.
Accomp. Interventricular artery
Middle cardiac vein
Begins at apex
Occupies posterior interventricular sulcus
Enters coronary sinus near terminus (right atrium)
Accomp. Post. Interventricular artery
Small cardiac vein
Begins low on ant. right surf. Of heart in myocardium of right ventricle
Courses posteriorly to right side of coronary sulcus to enter coronary sinus near terminus (right atrium)
Oblique cardiac vein
Of left atrium
Aka Vein of Marshall
From left atrium near left sup. Pulmonary vein
Enter coronary sinus near beginning
Cavities of Heart
Right Atrium-Tricuspid Valve [N.208]
Anterior: auricle and pectinate muscles
Sinus venarum: from veins
Posterior: Superior and inferior vena cavae, crista terminalis
Superior: sinoatrial node
Interatrial septum: opening of coronary sinus, fossa ovalis
Tricuspid valve
Inferior vena cava
Begins at common iliac vein (abdomen)
Enters thorax thru central tendon of diaphragm
Enters fibrous pericardium at 8th thoracic vertebra
Right Ventricle [N.208]
Muscular inflow and Smooth outflow (infundibulum & pulmonary trunk)
Thinner wall than left ventricle and C-shaped
Muscles: trabeculae carnae
Septomarginal trabeculum: right AV bundle
Three papillary muscles attached to two cusps via chordae tendinae
Crista supraventricularis
Pulmonic valve
Within pulmonary trunk
Three semilunar cusps with walls called lunules and center nodule
Left Atrium [N.209]
Smooth walled portion: receives oxygenated blood from R & L pulm. Veins
Only left auricle contains pentinate muscles
AV or mitral valve only 2 cusps
Left Ventricle [N.209]
Muscular inflow portion and smooth walled outflow portion
Aortic vestibule
Ascending aorta
Thick walls, circular shaped
2 papillary muscles
Aortic valve (L & R coronary art.; posterior noncoronary)
Cardiac Skeleton
Connective tissue between atria and ventricles around all 4 cardiac valves
Functions: supporting valves
Acting as electrical insulator, preventing spread of current from AàV
Except at atrioventricular bundle
Conducting System of Heart
Consists of spontaneously active, specialized cardiac muscle fibers
Fibers initiate and maintain heart beat: endogenous
Sinoatrial node
highest endogenous rate
determines heart rate
located within superior part of crista terminalis (right atrium
Atrioventricular node
Located in interatrial septum
Atrioventricular bundle
Begins at AV node
Passes thru membranous interventricular septum into muscular part
Divides into right and left bundle branches for two ventricles
Surface Anatomy of Cardiac Valves
mitral valve
blood flow sound conveyed: left bentricle to apex
sound heard: 5th intercostalspaceon left
tricuspid valve
blood flow sound conveyed: rightby right ventricle
sound heard: lower part of sternum
aortic valve
blood flow sound conveyed: ascending aorta
sound heard: 2nd intercostal space behind sternum
pulmonic valve
blood flow sound conveyd: pulmonary trunk
sound heard: 2nd intercostals space left of sternum
Innervation of Heart
Supplied with nerves from superficial and deep cardiac plexes
preganglionic parasympathetic axons
from cardiac branches of vagus nerve
decrease heart rate
efferent: decrease contractile force and constrict coronary arteries
afferent: mediate reflexes
postganglionic sympathetic axons
increase heart rate
efferent: increase contractile force and dilate coronary arteries
cell bodies in cervical sympathetic ganglia
“referred pain” ****
CLINICAL CORRELATION
Costal cartilages provide reliance to the thoracic cage, preventing many blows from fracturing the sternum and/or ribs. In elderly people, costal cartilages undergo calcification, making the cartilages radiopaque.
Rib excision is performed by surgeons desiring to access the thoracic cavity. A incision is made through the periosteum along the curve of the rib, and a piece of ribe is removed. After the operation, the reib regenerates from the oseogenic layer of the perosteum.
Rib fracture commonly result directly from blows or indirectly from crushing injuries. May injure internal organs such as lung or spleen
Cervical ribs articulate with C7 vertebra dn are clinically significant because they may compress the inferior trunk of the brachial plexus of nerves and cause tingling and numbness along the medial border of the forearm. They may so compress the subclavian artery, resulting in ischemic muscle pain I the upper limb, ie pain caused by poor blood supply.
Sternal fracture- body is commonly fractured, usually a comminuted fracture (broken into several pieces)
To access the thoracic cavity for operations on heart and great vessels, sternum is divided in the median plane. Sternal body is often used for a bone marrow needle biopsy because of its breath and subcutaneous position.
The apices of the lungs and their coverings project through the superior thoracic aperture into the root of the neck. On its way to the upper limb, the subclavian art also passes through the superior thoracic aperture and produces a groove in the first rib. Sometimes this artery is compressed between the clavaicle superiorly and the first rib interiorly, producing vascular symptoms (pallor and coldness of skin) costoclavicular syndrome. Clinicians may refer to the superior thoracic aperture as the thoracic outlet, emphasizing that imp. Nerves and vessels pass from the thorax through the aperture into the upper limb. Hence clinicians refer to various types of thoracic outlet syndromes.
Understanding of lymphatic drainage of the breats is of practical importance in predicting the metastasis of breast cancer. Interference with the lymphatic drainage by cancer produces a leathery thickening of the skin. Often it is dimpled and has prominent pores that give the skin the appearance of orange peel. Dimples and pores result from shortening of the suspensory ligaments because of cancerous invation.
Mastectomy is now uncommon. Often only tumor and surrounding tissues removed. In males, breast cancer undetected until invasion of lymph nodes has occurred.
Rib dislocation refers to displacement of a costal cartilage from the sternum ie the sternocostal joint is dislocated. This causes severe pain ,partic. During deep respiratory movements. The injury produces a lump-like deformity at the dislocation site. Common in body contact sports, possible complications are pressure on or damage to nearby nerves, vessels, and muscles
Rib separation refers to dislocation of costochondral junction. In separation of the 3rd to 10th ribs, tearing of the perichondrium and periosteum usually occurs.
Paralysis of half of the diaphragm because of injury to its motor supply from the phrenic nerve does not affect the other half because each dome has a separate nerve supply. One can detect paralysis of the diaphragm radiographically by noting its paradoxical movement. Instead of descending on inspiration, the paralyzed dome is pushed superiorly by the abdominal viscera.
Tags: anastomosis, aorta, Atrioventricular bundle, Cardiac Skeleton, chordae tendinae, coronary sulcus, crista terminalis, diaphragm, epicardium, interventricular sulcus, ischemic muscle pain, Mediastinum, myocardium, Pericardiacophrenic vessels, postganglioinc, preganglionic parasympathetic axons, Pulmonic valve, Sinoatrial node, sternum, thoracic cage, thoracic vertebra, Thorax, Tricuspid Valve
