35 terms

Anatomy: Thoracic diaphragm

STUDY
PLAY
The thoracic diaphragm is a double-domed musculotendinous partition between the thorax and abdomen that is the principal muscle of
inspiration
Its convex superior surface faces the thorax and the concave inferior surface the abdomen. It has a trifoliate central aponeurotic part, also known as the
central tendon of the diaphragm, CTD, and a peripheral muscular part that takes origin from several sources.
The peripheral muscular part comes from several different sites and constitutes the origin of the thoracic diaphragm. These sites of origin are the
sternum (sternal origin), lower six ribs (costal origin), the lumbar vertebrae and deep fascia of posterior abdominal muscles (lumbar origin).
Sternal origin:
this consists of two muscular slips arising from the posterior aspect of the xiphoid process. This part is variable - may or may not be present.
Costal origin:
this part arises from the internal surface of the lower six costal cartilages and their corresponding ribs. These fibers arch upwards and medially to form the domes of the thoracic diaphragm
Lumbar origin;
this part arises from the deep fascia of two posterior abdominal muscles (Psoas major and Quadratus lumborum) as medial and lateral arcute ligaments respectively, and from the abdominal surface of the first two to three lumbar vertebrae/intervertebral discs/anterior longitudinal ligament, as the right and left crura (one crus; two crura). Fibers from the crural part ascend to the central tendon of the diaphragm. The right crus is longer and larger than the left. The two crura are united by their deep fascia to form the median arcuate ligament, which forms the aortic hiatus anterior the descending thoracic aorta and other structures.
Arcuate ligaments:
the median arcuate ligament is the deep fascia that connects the two crura in the midline, and forms the aortic hiatus. The medial and lateral arcuate ligaments are deep fascia over Psoas major and Quadratus lumborum respectively, that gives origin to a part of the lumbar part of the thoracic diaphragm.
Insertion
The fibers from especially the lumbar origin converge on the central tendon of the diaphragm, CTD, at xiphisternal junction level. This tendinous insertion has no bony attachment and is incompletely divided into three leaves, resembling a wide cloverleaf that lies rather more anterior than central. The caval opening (for Inferior vena cava) lies here. The central tendon is slightly depressed by the inseparably attached fibrous pericardium, enclosing the heart
The muscular part of the thoracic diaphragm is located peripherally with its fibers converging radially on the
trifoliate central tendon of the diaphragm.
Actions:
immediately preceeding normal respiration, the medullary respiratory center of the brain stem sends action potentials to the C3 - C5 spinal cord segments, which then give off motor nerves from lamina IX (9) which ventral rami coalesce to form the phrenic nerves bilaterally. This successful respiratory stimulus reaches the thoracic diaphragm, making the CTD contract, pulling the domes down into the abdomen, decreasing the intra- thoracic pressure, thereby increasing the intra - thoracic volume according to Boyle's law. The thoracic diaphragm exerts a tremendous influence on both thoracic and abdominal organs, creating space during the respiratory cycles for air to be drawn into the nostrils and for venous blood to return to the right atrium.
Diaphragmatic Hernias (Fig.3)
A diaphragmatic hernia is abnormal protrusion of any abdominal viscera, or parts thereof, into the thoracic cavity through a congenital or acquired opening in the diaphragm. When a diaphragmatic hernia occurs via the esophageal hiatus, it is termed a hiatus/hiatal hernia. There are two principal types of diaphragmatic hernias, congenital and acquired.
Acquired DiaphragmaticHernias (Fig.4): there are two types of acquired diaphragmatic hernias,

the sliding is the one

It develops mostly in women of middle and more advanced age, as a result of progressive slackness of the

This permits the lower esophageal sphincter (LES), the cardia and fundus of the stomach, to



The upward sliding occurs with



Early on, the hernia slides upward and retracts relatively freely (reversible, unobstructed hiatus hernia), but later,










Causes:
sliding and rolling (para-esophageal). Of all the diaphragmatic hernias, both congenital and acquired,

most commonly encountered.

phrenoesophageal ligament, from which a dilation of the esophageal hiatus ensues.


slide/glide into the thoracic cavity, with a consequent apparent loss of the cardiac notch and a downward displacement of the physiologic inferior esophageal sphincter.

change of body position (reclining), in response to the suction effect of each inspiratory movement, or with filling of the stomach.

adhesions may form which fix the hernia in place. The disease may remain symptomless for many years and may be discovered only accidentally during the search for the cause of a variety of epigastric symptoms, usually produced by an accompanying reflux esophagitis (inflammation of the esophageal mucosa due to the regurgitation of gastric acid). The diagnosis is readily established by adequate radiographic examination (putting the patient into the head-down Trendelenburg position may be necessary) and esophagoscopy, which, in particular, is able to confirm the reflux phenomenon.

weakened LES, abnormally large esophageal hiatus, increased intra-abdominal pressure(chronic cough, straining, constipation, obesity, pregnancy, vomiting).
Paraesophageal Hernia:
Much less frequently, the esophagophrenic ligament remains intact, leaving the esophagus and cardia in the usual and fixed position, while a portion of the gastric fundus (and sometimes most of the stomach) herniates into the thoracic cavity through a fibromuscular aperture on the left or right side of the gastroesophageal junction. In such cases of paraesophageal hernia, the parietal peritoneum, which normally covers the abdominal surface of the diaphragm, prolapses and forms the outer wall of the hernial sac. Since the esophagocardial relationships, attachment, and position are normal, there is usually no reflux esophagitis; however, incarceration or obstruction of the herniated portion of the stomach may occur.
Congenital Diaphragmatic Hernias, C.D.H. (Fig.5) :




The most common site is a
a congenital diaphragmatic hernia is characterized by the presence of abdominal viscera in the thoracic cavity from birth. Because of the complexity of the formation of the thoracic diaphragm, CDHs do occur.

postero-lateral defect, leading to a lumbocostal triangle hernia. Because this site is the most dominant of all sites for the congenital type, the term congenital diaphragmatic hernia is synonymous with a lumbocostal defect (foramen of Bochdaleck), the sites where the pleuroperitoneal membranes cover, especially the left pleuriperitoneal membrane/fold (85 -90%). It occurs about once in 2,000 newborn infants. Because it occurs very early in development (between week 3 and 10), the presence of abdominal viscera in the thorax inhibits fetal lung development and maturation (pulmonary hypoplasia) through compression and displacement, and thus results in life-threatening breathing difficulties from birth. The much rarer type of congenital hernia is the foramen of Morgagni hernia - a protrusion between the xiphisternal fibers of the thoracic diaphragm.
2. Its muscular portion arises from the wide, ring like inferior thoracic aperture, invaginates the thoracic cage to form the trefoil central tendon of the diaphragm, and produces a right dome that is
higher (level with top of liver and nipple) than the left,
4. The _____ nerve innervates most of the muscle of the diaphragm and also sensory , whereas the lower five _____ plus _____ nerves provide the peripheral part with sensory innervation,
4. The phrenic nerve innervates most of the muscle of the diaphragm and also sensory , whereas the lower five intercostal plus subcostal nerves provide the peripheral part with sensory innervation,
5. When stimulated by the phrenic nerves, the domes of the diaphragm pull
down (descend), compressing the abdominal viscera, increasing the intrathoracic volume while decreasing the intrathoracic pressure, according to Boyle's law; this draws in air and enables venous blood to return to the right heart,
6. The lumbocostal triangle and the esophageal hiatus are potential sites of
congenital and acquired diaphragmatic hernias respectively; developmental defects in the left lumbocostal region accounts for most congenital hernias.
The diaphragm has a circumferential origin from
three different sources (4 in the embryo),
Congenital diaphragmatic hernias are an indication for
intrauterine surgery,
Domes right higher than left.
When people can't breath you
keep them up due to the diaphragm being pulled by gravity.
THORACIC DIAPHRAGM
DEFINITION : a musculotendinous/fibromuscular partition
2 Surfaces, 2 Domes, & 2 Parts,
TWO PARTS :
- Peripheral muscular (Sternal, costal & lumbar/crural), part,
- Trefoil central aponeurotic part.
EMBRYOLOGY : 4 sources
FUNCTIONS : (1) Because the peripherally disposed muscle of the diaphragm is radially arranged, and insert into the central tendon (CTD), when it contracts, it pulls the domes down into the abdomen, thereby increasing the intra - thoracic volume & vertical diameter of the thoracic cage/decreasing intra-thoracic pressure, for air to enter, (2) The diaphragm exerts a tremendous influence on both thoracic and abdominal organs , creating space during the respiratory cycles.
EFFECTS OF POSTURE ; recumbency/supine, sitting/standing, trendelenburg vis -a-vis patients with respiratory problem,
SUSPENSORY LIGAMENT OF DUODENUM (ligament of Treiz)
from RT crux of diaphragm to DJF (duodenojejunal flexure/junction)
APERTURES OF THE DIAPHRAGM
(what are the three major)?
Think : I Phrentically Ate
10 Vile Eggs
AT Around 12

T8 - IVC, Phrenic Nerve
T10 - Vagus, Esophagus
T12 - Aortic Arch, Thoracic Duct, Azygos Vein
VASCULATURE & INNERVATION OF THORACIC DIAPHRAGM
VASCULATURE:

LYMPHATICS :


NERVES :
pericardiocophrenic, musculophrenic, superior & inferior phrenic arteries & veins ; Veins drain to both ITV, IVC, & Azygos system

lymph drains to parasternal, mediastinal, phrenic & lumbar nodes

PHRENIC NERVE; Sole motor; also Sensory to the 3Ps & Central tendon,
LOWER 6-7 INTERCOSTAL NERVES: sensory to the peripheral part.
Innervation: anything that has phrenic in it relates the the diaphragm. You have the Phrenic nerves which are the major nerves.
What are the three Ps that relate the the diaphragm
The pleural, paricardium, peritonium.

Each are the outer layer/covering (of pleural sac, of pericardial sac, of a sac anterior and inferior of the diaphragm)

All are innervated for sensation by the Phrenic nerve
How are persons with breathing problems positioned and why?
standing up because you don't want their abdomal parts going into their thoracic cavity
What parts of the thoracic diaphragm transmit the following structures: esophagus, inferior vena cava, descending thoracic aorta, sympathetic trunks, and splanchnic nerves?
The middle mediastinum, essentially where one can draw the TTP (Plane of Ludwig: T4)
How would the sources of innervation of the thoracic diaphragm affect symptoms such as pain in diseases affecting the diaphragm?
The Phrenic Nerve (C3-5) innervates the diaphragm
When the thoracic diaphragm contracts, which of the three diameters of the thoracic cavity will increase?
- Vertical
What is paradoxical breathing?
- the diaphragm moves opposite to the normal directions of its movements

- it moves upwards during inspiration and downwards during expiration
What is the difference between congenital and acquired diaphragmatic hernias?
Congenital: Acquired during birth due to one or more parts of the thoracic diaphragm being weak or unable to close

Acquired: Most likely due to trauma or neuromuscular weakness (age, poor posture, etc.)
What is the difference between gliding and rolling esophageal hernias?
Sliding - part of the stomach "slides" up through the diaphragm (2nd degree acid reflux)
- This is worse because you lose function of the esophageal sphincter, and some loss of function of the vagal trunks

Rolling - fundus of the stomach "rolls" next to the esophagus
- The esophageal sphincter is relatively fine
What are the differences between Mallory-Weiss & Boerhaave's syndromes?
A Mallory-Weiss tear occurs in the mucous membrane of the lower part of the esophagus or upper part of the stomach, near where they join. The tear may bleed. Any condition that leads to violent and lengthy bouts of coughing or vomiting can cause these tears. Symptoms are bloody stools and vomiting blood.
What are the actions, major openings of the diaphragm, and the structures that enter and leave these openings?
- Action: Contract to increase thoracic cavity space for inspiration (moving downward) and then aid in normal expiration.
- T8, T10, T12
- T8: IVC, Phrenic Nerve
- T10: Esophagus, Vagus
- T12: Aortic Arch, Thoracic Duct, Azygos Vein
YOU MIGHT ALSO LIKE...