The diaphragm is a dome-shaped, muscular and membranous structure that plays a crucial role in respiration. Here are the main parts and anatomical features of the diaphragm:
1. Central Tendon
Location: Central portion of the diaphragm.
Structure: Aponeurotic (tendon-like) structure that is devoid of muscle fibers.
Function: Acts as the insertion point for the muscle fibers of the diaphragm and provides attachment for the pericardium of the heart.
2. Muscular Portions
The diaphragm has three main muscular components:
Sternal Part:
Origin: Attaches to the xiphoid process of the sternum.
Insertion: Central tendon.
Costal Part:
Origin: Attaches to the inner surfaces of the lower six ribs and their costal cartilages.
Insertion: Central tendon.
Lumbar Part:
Origin: Attaches to the lumbar vertebrae via the right and left crura and the arcuate ligaments.
Insertion: Central tendon.
3. Crura (Right and Left Crus)
Right Crus:
Origin: Arises from the bodies of the upper three lumbar vertebrae.
Left Crus:
Origin: Arises from the bodies of the upper two lumbar vertebrae.
Function: The crura anchor the diaphragm to the lumbar spine and form the esophageal hiatus.
4. Arcuate Ligaments
Medial Arcuate Ligament: Spans from the body of L1 to the transverse process of L1.
Lateral Arcuate Ligament: Spans from the transverse process of L1 to the 12th rib.
Median Arcuate Ligament: Connects the right and left crura, forming an arch over the aortic hiatus.
5. Hiatuses (Openings)
Aortic Hiatus:
Location: Posterior to the diaphragm, formed by the median arcuate ligament.
Contents: Aorta, thoracic duct, and sometimes the azygos vein.
Esophageal Hiatus:
Location: Formed by the right crus, located slightly to the left of the midline.
Contents: Esophagus, vagus nerves.
Caval Opening (Foramen):
Location: Central tendon, right of the midline.
Contents: Inferior vena cava, branches of the right phrenic nerve.
The diaphragm is primarily innervated by the phrenic nerves, with some additional sensory innervation from the intercostal nerves.
Phrenic Nerves
Origin: Arise from the cervical spinal cord segments C3, C4, and C5.
Course: The phrenic nerves descend through the neck, passing anterior to the scalenus anterior muscles, enter the thoracic cavity, and run along the pericardium to reach the diaphragm.
Function: Provide motor innervation to the entire diaphragm and sensory innervation to the central tendon, pleura, and peritoneum covering the diaphragm.
Intercostal Nerves
Origin: Arise from the thoracic spinal cord segments T5 to T11.
Function: Provide sensory innervation to the peripheral parts of the diaphragm.
Arterial Supply of the Diaphragm
The diaphragm receives blood supply from multiple arteries originating from both the thoracic and abdominal sides.
Superior Aspect:
Pericardiacophrenic Arteries:
Origin: Branches of the internal thoracic arteries.
Course: Accompany the phrenic nerves.
Supply: Central portion of the diaphragm.
Musculophrenic Arteries:
Origin: Terminal branches of the internal thoracic arteries.
Supply: Anterolateral portions of the diaphragm.
Superior Phrenic Arteries:
Origin: Branches of the thoracic aorta.
Supply: Posterior part of the diaphragm.
Inferior Aspect:
Inferior Phrenic Arteries:
Origin: Branches of the abdominal aorta (or celiac trunk).
Supply: Inferior surface of the diaphragm.
Development of the Diaphragm
The diaphragm develops from four embryological structures:
Septum Transversum:
Origin: Mesodermal tissue.
Development: Forms the central tendon of the diaphragm.
Location: Initially located at the cervical level and later descends to the thoracic region during development.
Pleuroperitoneal Membranes:
Development: Fuse with the septum transversum and the dorsal mesentery of the esophagus to form the posterolateral parts of the diaphragm.
Significance: Close the pericardioperitoneal canals, preventing the herniation of abdominal contents into the thoracic cavity.
Dorsal Mesentery of the Esophagus:
Development: Contributes to the formation of the crura of the diaphragm, which attach the diaphragm to the lumbar vertebrae.
4. Body Wall Mesoderm:
Development: Contributes to the muscular portions of the diaphragm, especially in the peripheral areas.
Describe the origin and insertion of muscles of the diaphragm.
Origin: The diaphragm originates from the xiphoid process of the sternum, the lower six costal cartilages, and the lumbar vertebrae (via the crura and arcuate ligaments).
Insertion: It inserts into the central tendon of the diaphragm.
Explain the blood supply to the diaphragm.
The diaphragm receives blood from the following arteries:
Superior phrenic arteries (branches of the thoracic aorta)
Inferior phrenic arteries (branches of the abdominal aorta)
Musculophrenic and pericardiacophrenic arteries (branches of the internal thoracic arteries).
Discuss the nerve supply of the diaphragm.
The diaphragm is innervated primarily by the phrenic nerve (C3, C4, and C5), which provides motor and sensory innervation. The lower intercostal nerves also provide some sensory innervation to the peripheral parts of the diaphragm.
What are the major openings in the diaphragm and what structures pass through them?
The diaphragm has three major openings:
Caval opening (at T8 level) for the inferior vena cava.
Esophageal hiatus (at T10 level) for the esophagus and vagus nerves.
Aortic hiatus (at T12 level) for the aorta, thoracic duct, and azygos vein.
Describe the role of the diaphragm in respiration.
The diaphragm is the primary muscle of respiration. During inspiration, it contracts and flattens, increasing the vertical dimension of the thoracic cavity and reducing intrathoracic pressure, which allows air to enter the lungs. During expiration, it relaxes and returns to its dome shape, decreasing the thoracic cavity volume and increasing intrathoracic pressure, pushing air out of the lungs.
Explain the clinical significance of the diaphragmatic hernia.
A diaphragmatic hernia occurs when abdominal contents herniate into the thoracic cavity through a defect in the diaphragm. This can lead to respiratory distress and compromised lung function, often requiring surgical repair.
What are the anatomical differences between the right and left hemidiaphragm?
The right hemidiaphragm is typically higher than the left due to the presence of the liver beneath it. The left hemidiaphragm is usually lower and more mobile due to the stomach and spleen.
Identify and describe the arcuate ligaments of the diaphragm.
The diaphragm has three arcuate ligaments:
Median arcuate ligament (over the aortic hiatus).
Medial arcuate ligaments (over the psoas major muscles).
Lateral arcuate ligaments (over the quadratus lumborum muscles).
These questions cover key aspects of the diaphragm's anatomy, function, and clinical relevance, providing a comprehensive understanding of this vital structure.
What is the extent and course of oesophagus ?
Oesophagus is a muscular tube that conveys food from the pharynx to the stomach.
Extent of oesophagus:
it begins as continuation of pharynx in the neck at the lower border of the cricoid cartilage ( at the level of C6 vertebra) to the cardiac end of the stomach in the abdomen (opposite T11 vertebra)
Is 10 inches ( 25cm) long.
Is divided into three parts i.e. cervical, thoracic and abdominal.
Course of oesophagus:
Cervical part (4cm): descends behind the trachea and in front of the bodies of the cervical vertebrae.
Thoracic part (20 cm): passes down through the superior and posterior mediastinum in from of thoracic vertebrae. It lies behind the trachea in superior mediastinum and from the bifurcation of trachea onwards, it passes behind the right pulmonary artery. left principal bronchus and left atrium ( in the posterior mediastinum).
Abdominal part (1-2cm): enters the abdomen by passing through the opening in the diaphragm (at the level of T10 vertebral level. After a short course in the abdomen ( 2cm) opens in the cardiac end of stomach.
Enumerate the sites of constrictions of esophagus.
Oesophagus has four constrictions:
1st constriction : at the beginning of oesophagus, at the level of C6 vertebra (15 cms/ 6 inches from incisor teeth ). This is the narrowest part of oesophagus.
2nd constriction : where the arch of aorta crosses it, at the level of T3 vertebra ( 22.5 cms/9 inches from incisor teeth)
3rd constriction : where the left bronchus crosses it , at the level of T6 vertebra ( 27.5 cms/11 inches from incisor teeth )
4th constriction : where it passes through the diaphragm, at the level of T10 vertebra ( 40 cm/15 inches from incisor teeth)
Name the arteries that supply oesophagus.
Arterial that supply oesophagus are:
Cervical part of oesophagus: oesophageal branches of inferior thyroid artery.
Thoracic part of oesophagus : oesophageal branches of descending thoracic aorta and bronchial arteries.
Abdominal part of oesophagus : oesophageal branches of left gastric and left inferior phrenic arteries.
Name the veins into which the oesophageal veins drain.
Venous drainage of oesophagus:
Cervical part: into inferior thyroid veins
Thoracic part : into azygous and hemiazygous veins
Abdominal part : into hemiazygous vein (tributary of inferior vena cava) & into left gastic vein ( tributary of portal vein)
*Abdominal part of oesophagus is one of the sites portocaval anastomosis.
Enumerate the lymph nodes into which lymphatic drainage of oesophagus occurs.
Lymphatic drainage of oesophagus:
Cervical part : into deep cervical nodes
Thoracic part : into posterior mediastinal nodes draining into supraclavicular nodes
Abdominal part : into left gastric nodes
*Hard fixed supraclavicular nodes may be palpated in patients with advanced oesophageal cancer.
Applied Aspects
Oesophageal varices
Are the dilated submucosal veins in the lower esophagus.
Occur as a consequence of portal hypertension.
Lower end of oesophagus is one of the sites of portocaval anastomosis. There is anastomoses between the oesophageal veins that drain above into azygous vein (drains into superior vena cava) and below into left gastric vein(a tributary of portal vein). In situations where portal pressure increases, such as cirrhosis of liver, the blood flow is redirected from the liver into areas with portocaval anastomosis. The collateral channels of portocaval anastomosis open up, become dilated and tortuous to form oesophageal varices which may rupure to cause hematemesis (vomiting of blood ).
Achalasia cardia
It occurs due to spsm of sphincter/ inability of the lower esophageal sphincter smooth muscles to relax. It causes dysphagia i.e. inability to swallow. Barium swallow shows Bird’s beak appearance.
Knowledge of the constrictions of oesophagus is important
Knowledge of the constrictions of oesophagus is important for the following reasons:
To ensure safe passage of Ryle’s tube which is inserted in stomach for gastric analysis and gastric feeding.
These are the sites where the swallowed foreign bodies are most likely to become impacted.
Strictures may occur after swallowing corrosive fluids.
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