Heart Presentation - Steve Flashcards
What are the boundaries of the middle mediastinum?
- Superior: transverse thoracic plane – disc between TV4 and TV5
- Inferior: diaphragm
- Lateral: mediastinal pleura
- Anterior: anterior surface of pericardium
- Posterior: posterior surface of pericardium
Contents of the middle medistinum?
- Pericardium
- Heart
- Origin of great vessels: pulmonary trunk, ascending aorta, pulmonary veins.
- Phrenic nerve and pericardiophrenic vessels
Describe the pericardium
A.A closed, fibroserous sac surrounding the heart and origins of great vessels.
- Fibrous pericardium
- serous pericardium
- pericardial sac
Describe the fibrous pericardium
- Tough external layer composed of dense irregular connective tissue.
- Anchors heart and prevents overfilling.
- The fibrous pericardium is attached:
a. anteriorly to the sternum via superior and inferior sternopericardial ligaments.
b. posteriorly to the fascia of the esophagus.
c. Inferiorly to the central tendon of diaphragm via pericardiacophrenic ligaments.
d. Superiorly with the adventitia (outer connective tissue layer) of the great vessels.
Describe the serous pericardium
- Thin serosal membranes (visceral and parietal layers)
- A closed sac that provides smooth, nearly frictionless surfaces for the heart to move in during contraction.
- Parietal pericardium
a. Composed of simple squamous epithelial cells + thin layer of loose connective tissue
b. Adherant to inner surface of fibrous pericardium - Visceral Pericardium
a. Composed of simple squamous epithelial cells + thin layer of loose connective tissue
b. Lines heart surfaces; continuous with parietal pericardium at great vessels.
c. Forms outer layer of the heart and is called the epicardium.
Describe the two clinical correlations of the pericardial sac
- Potential space between parietal and visceral pericardium; contains only a minimal amount of lubricating serous fluid.
- CLINICAL CORRELATION – Cardiac tamponade: If the pericardial sac is filled with fluid (due to trauma, inflammation, malignant effusion) the heart cannot fill to capacity due to the surrounding fluid and the inflexibility of the fibrous pericardium. This condition can be lethal as filling of the heart (preload) is reduced. The maximum capacity of pericardial sac is approximately 300 cc.
- CLINICAL CORRELATION – Pericardiocentesis is a procedure which removes excess pericardial fluid. Typically, a big needle is inserted through the bare area of the heart (left of sternum; 5th or 6th intercostal space) to avoid pleural cavity.
What are the pericardial sinuses?
Transverse pericardial sinus
oblique pericardial sinus
Describe the transverse pericardial sinus
what is the clinical correlation associated with this structure?
- Anterior border: aorta and pulmonary trunk.
- Posterior border: SVC and pulmonary veins.
- CLINICAL CORRELATION – Clinically important sinus because it allows surgeons to pass a surgical clamp around the major arteries and veins and insert tubes allowing blood to be diverted to a cardiac bypass pump during coronary artery bypass grafting and other cardiac procedures.
Describe the oblique pericarial sinus
- Pocket-like, cul-de-sac posterior to the heart.
- Bounded by the pulmonary veins and IVC.
What are the sternopericardial attachments?
Superior sternopericardial ligament
Inferior sternopericardial ligament
phrenopericardial ligaments
Describe the pericardial vascular supply
- Pericardiacophrenic arteries from internal thoracic artery
- Pericardiacophrenic veins → internal thoracic veins.
Describe the pericardial innervation
- Phrenic nerve provides sensory innervation to fibrous and parietal pericardium.
- Visceral pericardium is supplied by the cardiac plexus (see below).
- CLINICAL CORRELATION: Pain from the pericardium is typically referred to the shoulder/neck region (dermatomes supplied by the phrenic nerves; C3,4,5).
What happens if the serous pericardial membranes become inflamed?
If the serous pericardial membranes become inflamed (pericarditis), they become rough and no longer slide easily over one another. Pericarditis can be very painful due to the presence of pain fibers in the fibrous and parietal pericardium (There are no pain fibers in visceral pericardium).
Describe a cardiac tamponade
Surgeons and ER docs call this:
Beck’s Triad
- Distended neck veins
- Hypotension
- Muffled heart sounds
Mnemonic - 3 D’s:
- Distended jugular veins
- Decreased arterial pressure
- Distant heart sounds
What is Dressler’s syndrome?
Post MI pericarditis
Detail the flow of blood through the heart beginning with deoxygenated blood.
- Deoxygenated blood enters the right atrium through the SVC and IVC.
- Blood passes through the tricuspid valve to enter right ventricle.
- Blood exits right ventricle via pulmonary valve and pulmonary trunk – to lungs. (i.e. pulmonary circulation)
- Oxygenated blood enters left atrium through pulmonary veins (two on left, two on right).
- Blood passes through the bicuspid (mitral) valve to enter left ventricle.
Blood is pumped from the left ventricle to the systemic circulation through the aorta.
What are the external sulci of the heart?
- Atrioventricular sulcus (coronary sulcus)
- Interventricular sulci (anterior and posterior)
Describe the surfaces and borders of the heart
(3 borders, 4 surfaces)
- Surfaces
a. Anterior (sternocostal); 2/3 right ventricle, 1/3 left ventricle.
b. Right; right atrium.
c. Left; left ventricle + auricular appendage
d. Diaphragmatic (in the anatomical position, the heart rests on its diaphragmatic surface); 2/3 left ventricle, 1/3 right ventricle. - Borders
a. Right ; right atrium
b. Inferior ; 2/3 right ventricle, 1/3 left ventricle
c. Left ; left ventricle + auricular appendage
What forms the base and apex of the heart?
- Apex
a. Directed inferiorly and to the left.
b. Composed entirely of left ventricle.
c. Lies posterior to the left fifth intercostal space (MCL). - Base
a. Formed by left atrium
b. Directed posteriorly
Identify the tagged structures!
Describe the function of the fibrous skeleton of the heart
a. Provide structural support for heart valves; maintaining patency and preventing distention during heart contraction.
b. Provide attachment sites for the cardiac muscle and for the valve leaflets.
c. Insulates against impulse conduction from atria to ventricles; prevents aberrant spread of impulses.
d. Provides tunnel for passage of the A/V Bundle (of His)
Describe the structure of the fibrous skeleton of the heart
- Fibrous rings a) anulus fibrosis – around each orifice of the 2 atrioventricular valves.
b) fibrous coronets – around the aortic and pulmonary semilunar valves - Fibrous trigones - connections between the fibrous rings.
a. Left fibrous trigone forms a link between aortic and mitral valves.
b. Right fibrous trigone forms a link between aortic, mitral, and tricuspid valves. - Membranous portions of interventricular and atrioventricular septa
Describe the ratio of the atrial wall to the right ventricular wall to the left ventricular wall.
1:3:9
What are the noteable features of the right atrium?
- Sinus venarum
- auricle
- crista terminalis
- interartrial and atrioventricular septa
- fossa ovalis right atrioventricular orifice
- sinuatrial and atrioventricular nodes
Describe the sinus vernarum
a. Smooth and thin-walled; derived embrologically from the sinus venosus.
b. Forms the entrances of the IVC, SVC, and coronary veins.
Describe the auricle off the right atrium
a. Small, ear-like pouch extending anteriorly over the root of the aorta.
b. Represents the embryonic atrium.
c. Wall is lined with pectinate muscles.
Describe the crista terminaleis of the right atrium
a. Dividing line between sinus venarum and embryonic atrium (auricle).
b. The crista terminalis is demarcated externally by the sulcus terminalis.
Describe the fossa ovalis of the right atrium
a. Oval depression in interatrial septa representing the embryonic foramen ovale.
b. Embryologically, the foramen ovale allowed blood returning from the body to be shunted directly to the left atrium thus bypassing the fetal lungs.
Describe the Right atrioventricular orifice
a. Opening between right atrium and right ventricle with tricuspid valve.
b. Surrounded by a fibrous ring (anulus fibrosis) to maintain shape and patency.
Describe the Sinuatrial (SA) and atrioventricular (AV) nodes
a. SA node is located in the sub-epicardium of the right atrium near the junction of the sulcus terminalis and the SVC.
b. AV node is located in the sub-endocardium of the right atrium, near the opening of coronary sinus.
What are the structures of the right ventricle?
(6)
- Trabeculae carnae
- conus arteriosus
- right atrioventricular (tricuspid) valve
- Membranous interventricular septum
- muscular interventricular septum
- pulmonary (semilunar) valve
7.
Describe the trabeculae carnae
a. Muscular ridges of the ventricular wall.
b. Moderator band (septomarginal) – a specialized trabecular muscle passing from the interventricular septum to the anterior papillary muscle.
Describe the conus arteriosus
smooth-walled portion of chamber leading to pulmonary artery