Ch. 84 and 85 Diaphragmatic Hernias Flashcards
How much of the diaphragm is made up by the Y shaped central tendon?
21%
What layers does the central tendon have in the diaphragm?
two layers of fibers and around the foramen vena cava, the fibers have strong concentric arrangement
What are the parts of the diaphragm (3)?
central tendon
pars lumbalis dorsally
pars sternalis ventrally
what makes up the crus of the diaphragm
paired lumbar muscles form the diaphragmatic crura with the right crus being larger than the left
each crus has a bifurcate tendon from the 3rd and 4th lumbar vertebrae
what is the sternal muscle
an unpaired medial muscle continuous with the left and right costal muscles
what are the three openings of the diaphragm
esophageal
caval
aortic
what runs through the caval foramen
just vena cava - and it is tight!
the adventitia literally fuses with the foramen
what runs through the esophageal hiatus
esophagus and dorsal and ventral vagal trunks along with the esophageal blood supply
what runs through the aortic foramen
aorta, azygos, hemiazygos, and the lumbar cistern of the thoracic duct
what are the foramina of Morgagni
aka the sternocostal triangles
they are situated between the costal and sternal attachments of the thoracic diaphragm and allow egress of the cranial epigastric arteries (termination of the internal thoracic arteries)
herniations can occur and then they are called retrosternal or morgagni hernia!
what is the blood supply to the diaphragm
main phrenic arteries
they arise from the paired phrenicoabdominal arteries and extend forward to ramify subperitoneally on the crura of the diaphragm –> pass medial to the dorsal extensions of the tendinous center –> divide over the tendinous part –> redivide farther in the peripheral musculature
Terminal branches will follow the costal muscle and anastomose with the prhenic branches of the 10th/11th/12th intercostal arteries
what drains the blood of the diaphragm
cranial phrenic vein - empties into the cauda vena cava
caudal phrenic vein - joins the cranial abdominal vein to become the common phrenicoabdominal trunk, which empties into the cava near the ipsilateral renal vein
what is the motor innervation to the diaphragm
the phrenic nerves - arise from the 5th/6th/7th in dogs (sometimes a twig of 4) and 4th/5th/6th in cats
cranial to the diaphragm, the phrenic nerves are invested by the plica venae cavae and mediastinum and each left and right divides into three branches to innervate all three diaphragmatic muscles
what innervates the costal muscles
supplied by axons derived partly from the 4th nerve but mainly the 5th
what innervates the crural musculature
axons supplied mainly from the sixth and partly from the fifth cervical nerves
What is the role of the transverse septum in the diaphragm
in the embryo, the transverse septum originates in the region of the cervical vertebrae and then migrates caudally where it becomes the central tendon
*this is why the innervation to the diaphragm comes from all the way at C5/6/7 in the dog and C4/5/6 in the cat!
What forms the diaphragmatic crura from the embryologic anatomy?
the esophageal mesentery forms the diaphragmatic crura and is dorsal to the transverse septum
what is the fate of the embryologic pleuroperitoneal folds?
they develop along the lateral body walls and migrate medially where they close the pleuroperitoneal canals by fusion with the esophageal mesentery and dorsal portion of the transverse septum
what will result from contraction of the diaphragm?
the diaphragm contracts during inspiration and pushes caudally on the viscera, which displaces the abdominal wall outward -> this will produce expansion of the caudal rib cage
there is only a net effect on caudal rib cage dimensions when the abdominal cavity is open
What muscles are responsible for inspiratory dorsal displacement of the sternum
parasternal intercostal muscles
what does the term peritonealization mean
traumatic or incisional hernias do not have hernia sacs but with time, they will develop peritoneum over them and make a new sac
what is the term for when a rib inside the body fractures and creates a hernia?
auto penetrating hernia
What makes up the linea alba. What will it become caudally?
fibers of the tendinous aponeuroses of the external abdominal oblique, internal abdominal oblique and transversus abdominus. It will narrow as it travels caudally and is called the prepubic tendon or sometimes called the cranial pubic tendon
Where does the external abdominal oblique sheath run in relation to the rectus abdominus sheath?
ALWAYS superficial
From the umbilicus to more caudal, where does the internal abdominal oblique fibers run in relation to the rectus abdominus?
the internal abdominal oblique fibers are superficial to the rectus caudally. Cranially, they run deep and superficial
Where do the transverse abdominal muscle fascial fibers run in relation to the rectus abdominus?
in the cranial two thirds, the transverse abdominal sheath are deep to the rectus but in the caudal third, they are superficial
what is the arcuate line
denotes the cranial most aspect where the aponeurosis of the internal abdominal oblique and the transverse abdominal muscles first transition to a location superficial to the rectus abdominis
Where does the external abdominal oblique muscles originate from
4th or 5th to 12th rib and from the last rib and thoracodorsal fascia
where do the fibers of the internal abdominal oblique arise?
from the thoracolumbar fascia caudal to the last rib and from the tuber coxae
where does the transverse abdominal muscle originate from
the lumbar portion arises from the transverse processes of the lumbar vertebrae and thoracolumbar fascia and the costal portion arises from the medial sides of the 12th and 13th ribs and from the 8-11 costal cartilaegs
what are epigastric hernias
aka cranial ventral midline hernias
most often congenital and include umbilical and substernal hernias
What kind of abdominal wall defects are most at risk of incarceration and strangulation
defects with small inelastic hernial rings
how does strangulation of abdominal contents occurring a hernia
constriction of blood supply at the hernia ring
torsion of the vascular pedicle because of increased organ mobility within the hernia
*incarceration of a hollow viscus organ favors strangulation because the intraluminal pressure increases and that obstructs venous outflow
