Main Body: Mediastinum and Pleural Cavity

transthoracic plane

divides teh superior mediastinum from the inferior mediastinum, through the sternal angle anteriorly and the body of T5 posteriorly- cuts the pleural cavity into 1/3 and 2/3 parts

main compartments in the thoracic cavity

2 pleural cavities, 1 mediastinum

structures at the transthoracic plane

ascending aorta becomes arch of aorta, which becomes the descending aorta, brachiocephalic veins become the superior vena cava, trachea bifurcates into two main bronchi (carina)

carina

name for the portion of the trachea that bifurcates into the two primary bronchi 

nerves found within the superior mediastinum

vagus nerve and cardiac nerves from the sympathetic trunk

function of the heart

self-adjusting suction and pressure pump, has 4 chambers, atria are the receiving and ventricles are discharging chambers

apex of the heart

inferolateral part of the left ventricle, posterior to the left 5th intercostal space

base of the heart 

hearts posterior aspect, mainly the left atrium 

position of the heart

is tilted about 45 degrees to the left and the apex tilts about 45 degrees in the anterior-posterior plane, is also slightly centered to the left, which 2/3 of the heart left of the midsternal line

fibrous pericardium

outermost layer of the heart, function to envelop and protect the heart and aids in contractile efficiency of the heart by constricting how much the muscle can expand (like the deep fascia of the leg kinda)

serous pericardium

lines the inner surface of the fibrous pericardium, consists of the parietal pericardium and the visceral pericardium the directly lines the heart, in between the layers is the pericardial space in which serous fluid is found

serous fluid 

found in the pericardial space and functions as lubrication between the pericardium of the heart and the heart itself 

blood supply of the pericardium

80% of the blood supply is derived from the right and left internal thoracic arteries by way of their pericardiacophrenic branches (since blood from inside the heart itself moves too quickly to diffuse and supply it)

innervation of the pericardium

phrenic nerve provides sensory innervation from the parietal pericardium, and the general visceral afferent of the vagus nerves carries pain from the visceral pericardium

right atrium 

sits posterior in situ, vessels entering are teh SVC, IVC, and the coronary sinus, also technically the foramen ovale (oval fossa) which is closed after first breath but in utero functioned as a pathway between the R and L atria 

tricuspid valve

valve found between the right and left atria

right ventricle 

ejects blood into the pulmonary trunk through the semilunar valves (3)

papillary muscles

myocardium that attach to cordinae tendinae and help to open and close the bicuspid and tricuspid valves

left atria

recieves blood from the 4 pulmonary veins, atria/ventricle separated by the bicuspid valve (mitral valve)

left ventricle

contains semilunar valves between it and the arch of the aorta, has the thickest muscular wall since ejects the blood into the aorta and rest of the body from here

valves open during diastole 

during diastole, the heart fills and the tricuspid and bicuspid are open (aortic and pulmonary valves closed)

valves open during systole

during systole, the heart empties and the aortic and pulmonary semilunar valves are open while the tricuspid and bicuspid are closed

branches from the arch of the aorta

R brachiocephalic trunk, L common carotid, L subclavian

blood supply of the heart

supplied by branches from the left and right coronary arteries, which branch just distal to the start of the aorta

branches of the left coronary artery 

is the dominant anterior artery, give rise to 

• circumflex branch which wraps under the L auricle 

  • anterior interventricular branch that runs between the ventricle on the anterior surface 

branches of the right coronary artery

wraps under the right auricle, gives rise to the right marginal artery and posterior interventricular artery

innervation of the heart

vagus nerve and many of its branches, as well as sympathetic nerves

veins of the heart

begins at the coronary sinus, see branches of the small cardiac vein, the great cardiac vein, and the middle cardiac vein

great anatomists must practice so much 

• great cardiac vein runs with anterior interventricular artery 

• middle cardiac vein runs with posterior interventricular artery 

• small cardiac vein runs with right marginal artery 

conduction of the heart

begins at the SA node, travels to the AV node, then to the AV bundle, then to the right and left bundles, then to the purkinje fibers (which are formed by the purkinje cells)

pleural cavity components

parietal pleura (outermost layer), visceral pleura (lines the lungs), and the parietal cavity between them (potential space filled with pleural fluid)

right lung

has three lobes, superior, middle, and inferior with a horizontal and oblique fissure

left lung 

only has a superior and inferior lobe with a oblique fissure, also has a cardiac notch and the lingula 

root of the lungs

is surrounded by the hilum, contains veins, arteries, and bronchus

right bronchi

is shorter and stouter, also more vertical which predisposes it to aspirated objects which get dumped into the middle lobe

apex of lungs

found just above the 1st rib right under the root of the subclavian artery and vein

pulmonary arteries and veins 

unlike all other arteries and veins, pulmonary arteries carry deoxygenated blood from the heart and veins carry oxygenated blood to the heart 

indentations seen in the R lung 

see indentation from the superior vena cava, the esophagus, and the inferior vena cava 

indentations in the left lung

see indentations from the thoracic aorta and aortic arch, and from the esophagus

flow of blood through lungs

pulmonary artery to the alveolar sac to the pulmonary vein a

azygous system

consists of the azygous vein and the hemiazygous vein and accessory hemiazygous vein which crosses over to the L side, drains into the right and left bronchial veins

posterior mediastinum 

consists of the aorta, hemiazygous vein, azygous vein, the accessory hemiazygous vein, the SVC, and the brachiocephalic vein, the thoracic duct, and the sympathetic chains and splanchnic nerves 

diaphragm

innervated by the phrenic nerve (C3, C4, C5) and functions in inspiration. Has openings for the major structures passing between the abdomen and thorax, the anterior portion is found at the level of T9 and the posterior is found at the level of T12

IVC hiatus

found at the level of T8

esophageal hiatus

found at the level of T10

aortic hiatus 

found at the level of T12 

celiac trunk

branches off the aorta right underneath the diaphragm, is the main blood supply to teh viscera