Mediastinum and Heart Flashcards
mediastinum
- where is it/what is it
- limited by
central compartment of thoracic cavity
limited by
-connective walls that separate this central region from the pleural cavities on either side
mediastinum
- continuous anteriorly/posteriorly with…
- continuous superiorly with…
- attached inferiorly to…
A/P -sternum -costal cartilages to the bodies of the vertebrae superiorly -thoracic aperture inferiorly -diaphragm
mediastinum divisions
superior inferior -anterior -middle -posterior
inferior divisions of mediastinum separated by…
pericardium (CT)
what are the thoracic viscera located within the mediastinal regions?
esophagus
trachea and bifurcation to primary bronchii
heart
origin of great vessels
pericardium
- location
- composed of…
location
-middle region of inferior part of mediastinum
consists of a CT sac that is made up of 2 layers
-tough outer layer of dense irregular CT
-inner serous layer of simple squamous epithelium (mesothelium)
fibrous pericardium continuous with…
tunica adventitia of great vessels
cervical fascia
inner layer (mesothelium) of pericardium
- called…
- reflected onto heart as…
called parietal epicardium
reflected onto heart as visceral epicardium or outermost layer of heart
visceral epicardium adheres to…
muscular myocardium (heart muscle)
3 layers of heart tissue
-continuous with…
visceral epicardium -outermost myocardium -cardiac branched striated muscle endocardium three layers continuous with three tunics of the vasculature
myocardium
-sarcomere arrangement
branched striated, similar to that of a skeletal muscle
why are differences in the type of muscle between the heart and muscles important
sarcomere contractions
how do sarcomeres in the heart connect?
-why is this important
via modified z-lines (intercalated discs)
ensures contraction occurs in a widespread fashion rather than a strict linear fashion as seen in skeletal muscle
why are branched sarcomeres of the heart connected by gap junctions
allow direct sharing of cytoplasmic signals
in the heart, the sharing is of Ca++ to assure contraction
where in the heart is there a gross difference of appearance in terms to muscle (sarcomeres)
-is the myocardium different in these areas?
between atrium and ventricular walls
pectinate and trabeculae carneae
branched striated myocardium is similar
fibrous skeleton of heart
- histological composition
- function
composition
-dense collagen
supports integrity of
-cusps of the valves
-opening of each transition from chamber to vessel and between chambers
“insulator” of electrical activity limiting the spread of contraction from the atria to the ventricles, directing the depolarizing wave to the atrioventricular node
heart conductive system function
designed to spread a depolarizing wave across the atria and ventricles
from sinoatrial node, wave goes to…
goes through both atria myogenically (through the muscle)
myogenic spread of signal through atria limited to atria by…
fibrous skeleton
wave from SA node converges at…
-what is activated here
atrioventricular node
activates AV bundle (bundle of His)
AV bundle
- location
- function
location
-located in interventricular septum
-branches near apex of heart to spread through a right and left bundle branch
function
-right bundle branch supplies right ventricle
-left bundle branch supplies left ventricle
bundle branches end in…
-function of these
end in purkinje fibers
spread depolarization across walls of ventricles
function of papillary muscles from a timing standpoint
contract first in order to stabilize the two AV valves to resist prolapse and regurgitation of blood back into the atria
atrial and ventricular walls
- marked by
- these are not found…
marked by multiple muscular fiber ridges
ridges not present on interatrial or interventricular septa
