18.10.2011

Kaan Yücel M.D., Ph.D.

DIAPHRAGM A very thin, a double-domed muscle, is the only structure (apart

from the pleura and peritoneum) that separates the chest from the abdominal viscera

Its mainly convex superior surface faces the thoracic cavity, and its concave inferior surface faces the abdominal cavity.

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The diaphragm is the chief muscle of inspiration (actually, of respiration altogether, because expiration is largely passive).

It descends during inspiration; however, only its central part moves.

The central tendon of the diaphragm is a thin but strong aponeurosis situated near the center of the vault formed by the muscle.

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During expiration, the right dome reaches as high as the 5th rib and the left dome ascends to the 5th intercostal space. The level of the domes of the diaphragm varies according to the:

Phase of respiration (inspiration or expiration)

Posture (e.g., supine or standing)

Size and degree of distension of the abdominal viscera.

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It is divided into three parts, based on the peripheral attachments:Sternal partCostal partLumbar part

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The crura of the diaphragm are musculotendinous bands that arise from the anterior surfaces of the bodies of the superior 3 lumbar vertebrae, the anterior longitudinal ligament, and the IV discs.

Right crus

Left crus

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The right and left crura and the fibrous median arcuate ligament, which unites them as it arches over the anterior aspect of the aorta, form the aortic hiatus. The diaphragm is also attached on each side to the medial and lateral arcuate ligaments.

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ArteriesThe arteries supplying the the diaphragm are the branches of the internal thoracic artery, the thoracic aorta and the abdominal aorta.

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VeinsThe veins empty into the internal thoracic veins and the inferior phrenic veins. Lympathic drainage of diaphragmLymph from the nodes of the diaphragm drains into the parasternal, posterior mediastinal, phrenic, anterior diaphragmatic, and superior lumbar (caval/aortic) lymph nodes. InnvervationThe entire motor supply to the diaphragm is from the right and left phrenic nerves.

Phrenic nerve

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Diaphragmatic AperturesThe diaphragmatic apertures (openings, hiatus) permit structures (vessels, nerves, and lymphatics) to pass between the thorax and abdomen. There are three large apertures for: 1. Inferior vena cava (IVC)2. Esophagus3. Aortaand a number of small ones.

I’m Eating Apples.

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The most superior of the three large diaphragmatic apertures

An aperture in the central tendon primarily for the IVC

Also passing through the caval opening : terminal branches of the right phrenic nerve and a few lymphatic vessels.

CAVAL OPENING

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ESOPHAGEAL HIATUS

An oval opening for the esophagus in the muscle of the right crus of the diaphragm at the level of the T10 vertebra.

Also transmits the anterior and posterior vagal trunks, esophageal branches of the left gastric vessels, and a few lymphatic vessels.

CLINICAL NOTES- VENTRICLES

• Ventricular Septal Defects (VSD): The membranous part of the IVS is the common site of ventricular septal defects (VSDs) , although defects also occur in the muscular part.

• VSDs rank first on all lists of cardiac defects. • A VSD causes a left to right shunt of blood through the defect.• A large shunt increases pulmonary blood flow, which causes

severe pulmonary disease and may cause cardiac failure.

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CLINICAL NOTES- ATRIAAtrial Septal Defects (ASD): A congenital anomaly of the interatrial septum, usually incomplete closure of the oval foramen, is an atrial septal defect (ASD).

• Large ASDs allow oxygenated blood from the lungs to be shunted from the left atrium through the ASD into the right atrium, causing enlargement of the right atrium and ventricle and dilation of the pulmonary trunk.

• This left to right shunt of blood overloads the pulmonary vascular system, resulting in hypertrophy of the right atrium and ventricle and pulmonary arteries.

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CLINICAL NOTES- VALVES

Disorders involving the valves of the heart disturb the pumping efficiency of the heart. Valvular heart disease produces either stenosis (narrowing) or insufficiency. Because valvular diseases are mechanical problems, damaged or defective cardiac valves can be replaced surgically in a procedure called valvuloplasty.Stenosis is the failure of a valve to open fully, slowing blood flow from a chamber.

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CLINICAL NOTES- VALVES

Insufficiency or regurgitationis failure of the valve to close completely, usually owing to nodule formation on the cusps so that the edges do not meet or align.This allows a variable amount of blood to flow back into the chamber it was just ejected from. Both stenosis and insufficiency result in an increased workload for the heart.

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CLINICAL NOTES- VALVESMitral Valve Insufficiency (Mitral Valve Prolapse):

Scarring and shortening of the cusps results in insufficiencyRestricts the outflow of the left ventricle and leads to the hypertrophy of the myocardiumDuring ventricular systole, blood regurgitates back to the left atriumA hurt murmur will be heard.

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CLINICAL NOTES- VALVES

Narrowing of the mitral orifice Restricts the outflow of the left atrium A murmur will be heard during atrial contraction

Mitral valve stenosis

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CLINICAL NOTES- VALVES

Pulmonary valve stenosis

Narrowing of the pulmonary valve due to the fused cusps

Restricts the outflow of the right ventricle and leads to the hypertrophy of the myocardium.

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CLINICAL NOTES- VALVES

Pulmonary valve incompetence

Incomplete closure of the cusps due to thickening of their free margins due to a disease

During diastole, blood regurgitates back to the right ventricle from the pulmonary trunk

Heart murmur (a pathologic sound) could be heard by stethescope. Murmur is produced due to the turbulance caused by the blood passing from a narrow opening into a larger vessel or chamber.

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CLINICAL NOTES- VALVES

Aortic insufficiencyDuring diastole blood regurgitates from aorta back to the left ventricle. A hurt murmur will be heard during diastole.

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CLINICAL NOTES- VALVESAortic Valve Stenosis

The most frequent valve abnormality. (MVP??)Blood is unable to flow freely from left ventricle to aorta. The great majority of aortic stenoses is a result of degenerative calcification, and fusion of the aortic cups as a result.Aortic stenosis causes extra work for the heart, resulting in left ventricular hypertrophy.