Mediastinum And Heart Flashcards
What limits the central compartment of the thoracic cavity?
Connective walls that separate this central region from the pleural cavities on either side
-it is continuous anteriorly/posteriorly from sternum and costal cartilages to the bodies of the vertebrae
Describe the superior portion of mediastinum
- continuous with thoracic aperture
- attached inferiorly to the diaphragm
-Inferior part of mediastinum is subdivided into?
Anterior, middle, and posterior regions
What are the regions of the inferior part of the mediastinum separated by?
Pericardium (connective tissue)
What are the thoracic viscera located within the mediastinal regions?
- esophagus
- trachea
- bifurcation to the primary bronchii
- heart
- origin of the great vessels
What part of the mediastinum is the pericardium?
Middle region of the inferior part of the mediastinum
What does the pericardium consist of?
-2 layers (tough outer latter and inner serous layer)
What tissue type is the tough outer layer of the pericardium?
Dense irregular CT
What type of epithelium is the inner serous layer of the pericardium?
Simple squamous epithelium (mesothelium)
What is the pericardium continuous with?
- the tunica adventitia of the great vessels
- cervical fascia
Parietal epicardium
- it is the inner layer of mesothelium
- it is reflected onto the heart as the visceral epicardium or outermost layer of the heart
What is the visceral epicardium adhered to?
The muscular myocardium (heart muscle)
How many layers of tissue is the heart made up of?
3
- visceral epicardium (outermost)
- myocardium
- endocardium (innermost)
What is the myocardium made up of?
Cardiac branched striated muscle
How are cardiac sarcomeres attached to each other?
- gap junctions
- Intercalated discs-allows for contraction in a widespread fashion
Functions of the fibrous skeleton of the heart:
- supports integrity of cusps and valves
- “insulator” of electrical activity allowing for directing of the depolarizing wave to the AV node `
How does depolarizing wave spread from SA node to atria?
Gap junctions allow for spread of calcium
Myogenic spread is limited to the atria by?
The fibrous skeleton
Flow of deploarizing wave
SA node-atria-AV bundle (bundle of His), ventricles
Papillary muscles
- contract first in order to stabilize the 2 AV valves to resist prolapsed and regurgitation of blood back into atria
- have strong connective tissue attachments to the CT of the cusps of AV valves (chordae tendinae)
Muscular fiber ridges
- mark the atrial and ventricular walls
- assist in complete contraction of walls of chambers
Pectinate muscles
-mark the thin walled atria
Trabeculae carneae
Mark the thicker ventricular walls
Chordae tendinae
Attach papillary muscles to the cusps of the AV valves
Where do the openings of the coronary arteries lie?
Behind the left and right cusps of the aortic valve
What are the primary branches of the L coronary artery?
- anterior interventricular artery (LAD)
- circumflex branch of the LCA
What are the branches of the right coronary artery?
- marginal branch (travels along the right ventricle)
- terminal posterior interventricular branch
Coronary veinous drainage
- drainage parallels the arterial supply
- Great cardiac vein in the interventricular groove (anterior)
- Middle cardiac vein in the interventricular groove (posterior)
Cardiac sinus
- lies in the right AV sulcus posteriorly and drains into right atrium
- small cardiac vein and marginal branch of RCA drain here
What closes the aortic valve cusps?
The elasticity of the aorta pushing blood back toward the valve
Closing of aortic valve causes what to happen?
-blood pools in the aortic sinuses of the L and R aortic cusps
Elastic pressure causes what to occur?
Perfusion (flow or spread) of arterial blood into the coronary vessels
Fossa ovale
- remnant of fetal circulation
- goes from R atrium to L atrium
- blood didn’t need to go to lungs since it came oxygenated from placenta
