University:
Kentucky State University
Course:
BIO 301 | Human Anatomy
Academic year:

2020
Views:

145

Pages:

16
Author:

Dixie Summers

Inferior Thoracic Aperture (Thoracic outlet) (The Diaphragm) Inferior view (Abdominal) Superior view (Thoracic) It is a dome-shaped Musculofibrous septum that separates the thoracic from the abdominal cavity, its convex upper surface forming the floor of the thorax, and its concave under surface forming the roof of the abdomen. Its peripheral part consists of muscular fibers that take origin from the circumference of the inferior thoracic aperture and converge to be inserted into a central tendon. It is elevated on the right side due to the presence of the liver Origin of the diaphragm ..1 / 3 Sternal origin: • By 2 slips the back of the xiphoid process Origin of the diaphragm ..2 / 3 Costal origin: • By 6 slips from the inner surface of the lower 6 ribs and their costal cartilage. The slips of the costal origin interdigitate with the transversus abdominis muscle Origin of the diaphragm ..3 / 3 Vertebral origin: • Right crus: from the bodies of the upper 3 lumbar vertebrae (1). • Left crus: from the bodies of the upper 2 lumbar vertebrae (2). • Median arcuate ligament: arches over the aorta between the right and left crura (3). • 2 medial arcuate ligaments: arch over the psoas major muscles, each extends from the corresponding crus to the tip of the transverse process of the L1 (4). • 2 lateral arcuate ligaments: arch over the quadratus lumborum muscles, each extends from the transverse process of L1 to the 12th rib (5). 3 5 4 5 Insertion of the diaphragm It is inserted into the central tendon. The central tendon is shifted anteriorly (not central in position). Innervation of the diaphragm Right and Left Phrenic nerves (Mainly C4). Both nerves supply motor fibres to the diaphragm and sensory fibres to the fibrous pericardium, mediastinal pleura, and diaphragmatic peritoneum. The pericardiaco-phrenic arteries and veins travel with their respective phrenic nerves. The accessory phrenic nerve is a branch of the nerve to the subclavius and connects to the phrenic nerve in the thorax or the root of the neck. It may contain numerous phrenic nerve fibers. Clinical note Injury of the phrenic nerve can occur by multiple mechanisms; one common cause is from surgery (iatrogenic), primarily thoracic and cardiac surgery. The phrenic nerve can also be damaged from blunt or penetrating trauma, metabolic diseases like diabetes, infectious causes such as herpes zoster, direct invasion by tumor, neurological diseases such as cervical spondylosis and multiple sclerosis, myopathy (i.e., muscular dystrophy) and immunological disease (e.g., Guillain-Barre syndrome). Black arrow = dome of the diaphragm (Elevated) Red arrow = costophrenic angle Blue arrow = cardiophrenic angle. Major openings of the diaphragm ..1 / 3 Aortic Hiatus Lies exactly in the mid line at the level of the lower border of T12. Lies behind the median arcuate ligament. It transmits the: • • • • Aorta. Azygos vein. Thoracic duct. Lymphatics from the thorax to the cisterna chyli. The blood flow in the aorta is not affected by contraction of the diaphragm. Major openings of the diaphragm ..2 / 3 I. V. C. Hiatus Lies one inch to the right of the mid line at the level of the lower border of T8. Lies in the central tendon. It transmits the: • I. V. C. • Right phrenic nerve. • Lymphatics from the liver to the mediastinal lymph nodes. The adventitia of I.V. C. fuses fibres of the central tendon Major openings of the diaphragm ..3 / 3 Esophageal Hiatus Lies one inch to the left of the mid line at the level of the lower border of T10. Lies in the left crus but is surrounded by a sling from the right crus. This acts as a physiological sphincter at the lower end of the oesophagus. It transmits the: • Esophagus. • Anterior and posterior gastric nerves. • Esophageal arteries and veins. Minor openings of the diaphragm ..1 / 2 The superior epigastric artery passes between the sternal and costal origins of the diaphragm. The musculophrenic artery passes between the 7th and 8th slips of costal origin. The lower 5 intercostal nerves pass between all slips of costal origin of the diaphragm. Subcostal nerves and vessels pass behind the lateral arcuate ligament. Minor openings of the diaphragm ..2 / 2 The sympathetic chain passes behind the medial arcuate ligament. The greater and lesser splanchnic nerves pass through the corresponding crus of the diaphragm. The inferior hemiazygos vein passes through the left crus. The left phrenic nerve passes through the left crus. Functions of the Diaphragm - Main Muscle of Inspiration: The diaphragm pulls the central tendon down during contraction and increasing the vertical diameter of the thorax. This increases the negative pressure inside the thoracic cavity, which draws in air. - Muscle of Abdominal Straining: The contraction of the diaphragm will assist in the contraction of the muscles of the anterior abdominal wall in raising the intra-abdominal pressure will normal processes like micturition, defecation, and parturition. - Weightlifting Muscle: When a person takes and holds a deep breath, the diaphragm will assist the muscles of the anterior abdominal wall to raise the intra-abdominal pressure. This maneuver is also called as Valsalva maneuver and is used to augment heart murmurs and classify them whether they are clinically right-sided or left-sided.

The Diaphragm

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