Gut Book 5: Posterior Adominal Wall, diaphragm, Aorta, IVC & Lumbar Plexus Flashcards
Psoas major (O,I,A,N)
O: Anterior and lateral surfaces of bodies and transverse processes of vertebrae T12-L5 and their corresponding intervertebral discs.
I: lesser trochanter of femur
A: flexes thigh; with feet fixed flexes trunk; with only one side acting side bends trunk to same side.
N: spinal nerves L2 & L3 and sometimes L4
Psoas minor
O: lateral surface of bodies T12 and L1 and their corresponding intervertebral disc
I: Pectineal line on superior pubic ramus
A: Assists in flexion and side bending of the trunk; assists rectus abdominis in controlling pelvic tilt
N: spinal nerves L1 and L2
Quadratus lumborum
O: posterior 1/3 of the iliac crest and iliolumbar ligament
I: Medial anterior 1/2 of 12th rib and tips of transverse processes of vertebrae L1-L4
A: depresses 12th rib, assists in extension of trunk, side bends to same side; fixes last rib against traction of diaphragm during deep inspiration
N: spinal nerves T12-L4
Iliacus
O: iliac fossa
I: lesser trochanter
A: flexes thigh; with lower limb stabilized flexes the pelvis on the thigh
n: femoral nerve
Diaphragm
musculfascial septum which partitions the body cavity into thoracic and abdominopelvic cavities.
principal muscle of inspiration
dome shaped; concave superior surface
Action of diaphragm
a. increases the volume of the thorax and decreases intrathoracic pressure (necessary for inspiration to occur)
b. decreases the volume of the abdomen and increases the intra-abdominal pressure (important for stabilizing the spine while lifting, for defecation and parturition)
How high does the concave superior surface of the diaphragm extend?
as high as the 5th rib
muscle arrangement of diaphragm
radially arranged around a central tendon
what covers the superior surface of the diaphragm
endothoracic fascia and pleura
What covers the inferior surface of the diaphragm
transversalis fascia, subserous fascia and peritoneum.
Note: fascial layers above and below the diaphragm are continuous with one another through the openings in the diaphragm.
Subdivisions of the diaphragm
sternal, costal, lumbar portions
Sternal portion of the diaphragm
two muscular slips arising from the inner surface of the xiphoid process that pass directly posteriorly until they fuse with the central tendon.
Costal portion of the diaphragm
muscular slips that interdigitate with the costal attachment of the transversus abdominis arise from the inner surface of the lower six ribs and pass superiorly to fuse with the central tendon
lumbar portion of the diaphragm
crura and fibers originating from arcuate ligaments
Right crus
arises from the anterior surfaces of L1-L3 vertebrae, corresponding intervertebral discs and the anterior longitudinal spinal ligament.
Muscular fibers ascend and arch anteriorly to fuse with the central tendon.
Muscle fascicles split to enclose the esophagus (esophageal hiatus)
Larger of the two crura
Left crus
arises from the anterior surfaces of L1 and L2 vertebrae, corresponding intervertebral disc and anterior longitudinal spinal ligament
Fibers ascend and arch anteriorly to fuse with the central tendon
fibers originating from arcuate ligaments
medial arcuate ligament (medial lumbocostal arch), lateral arcuate ligament (lateral lumbocostal arch).
Muscular fibers arise from the medial and lateral arcuate ligaments, pass superiorly and fan laterally as they fuse with the central tendon of the diaphragm
Medial arcuate ligament
= medial lumbocostal arch
fascial thickening over the superior portion of the psoas major extending from the lateral portion of the body of L1 or L2 vertebra to its corresponding transverse process.
Lateral arcuate ligament
= lateral lumbocostal arch
fascial thickening over the superior portion of the quadratus lumborum extending from the transverse process of L1 vertebra to the distal tip of the 12th rib
Vertebral costal trigone
area where diaphragmatic fibers which originate on the lateral lumbocostal arch are lacking and represented only by the opposed fascias of the thorax and abdomen. Present to some degree in 80% of individuals, these areas are sites of potential diaphragmatic hernia. Also, the posterior surface of the kidney contacts the vertebral costal trigone. Here, perinephric abscess may reach the thorax by dissecting through this fascial trigone.
Central tendon of the diaphragm
common aponeurotic tendon of the muscular portion of the diaphragm
crescentic in shape; divided into three leaves: right, central and left
located more anteriorly such that posterior muscular fibers are longer
located directly below the pericardium, the external fibrous layer fusing with the central tendon
Foramina of the diaphragm
Caval foramen, esophageal hiatus, aortic hiatus
Caval foramen
located within the central tendon opposite the 8th thoracic vertebra
transmits the IVC and the right phrenic nerve
Note: the left phrenic nerve penetrates the muscular portion of the left hemidiaphragm.
Esophageal hiatus (of the diaphragm)
located within the right crus opposite the tenth thoracic vertebra
transmits the esophagus, esophageal branches of the left gastric artery, the anterior and posterior vagal trunks
Aortic hiatus (of the diaphragm)
located behind the confluence of the crura at the level of the 12th thoracic vertebra
transmits the aorta and the thoracic duct
Other structures which traverse the diaphragm
splanchnic nerves (greater, lesser, least) pass through the crura
the sympathetic trunk passes beneath the medial arcuate ligament
ascending lumbar veins, which form the azygos system, ascend beneath the medial arcuate ligament deep to the psoas muscles
the superior epigastric vessels penetrate the diaphragm a the sternocostal hiatus
arteries of the superior surface of the diaphragm
- pericardicophrenic a. - from internal thoracic a.
- musculophrenic a. - from internal thoracic a.
- superior phrenic a.- last paired branches arising from descending thoracic aorta
arteries of the inferior surface of the diaphragm (how do they get there? What branches are there?)
Inferior phrenic a.
a. paired anterolateral branches arising either as the first branches of the abdominal aorta or from the cloeliac trunk
b. the right inferior phrenic artery passes posterior to the IVC before gaining the inferior surace of the right hemidiaphragm
c. the left inferior phrenic passes posterior to the esophagus to gain the inferior surface of the left hemidiaphragm
d. both right and left inferior phrenic arteries divide into anterior and posterior branches.
Note: the posterior branch gives rise to the SUPERIOR SUPRARENAL ARTERIES.
Veins of the superior surface of the diaphragm
Correspond to the arteries, drain to internal thoracic veins
veins of the inferior surface of the diaphragm
on the right side the inferior phrenic vein is returned to the IVC
on the left side circulation of the inferior phrenic vein is returned to the left renal vein
Nerves to the diaphragm (motor and sensory)
motor- phrenic nerve (C3,4,5)
- only motor nerve to the diaphragm
- branches of the phrenic nerve distribute largely on the abdominal side of the diaphragm following the course of the inferior phrenic artery
Sensory- phrenic nerve conducts sensory fibers from the central portion of the diaphragm
- intercostal nerves 9-11 conduct sensory fibers from the peripheral portion of the diaphragm
referred pain from the gallbladder to the right shoulder
The posterior branch of the right phrenic n. which enters the abdomen via the caval hiatus, distributes with the posterior branch of the inferior phrenic a. and communicates with the sympathetic phrenic plexus (subsidiary plexus of the celiac plexus also traveling on the inferior phrenic a.) Visceral afferent (pain) fibers from the gallbladder are returned via this communication to the cervical spinal cord, most often to C4. This is the basis for referred pain from the gallbladder to the right shoulder.
Aorta: course
enters the abdominal cavity by passing through the diaphragm via the aortic hiatus which is located at the level of the 12th thoracic vertebra.
Follows a retroperitoneal course through the abdomen on the left lateral surface of the first four lumbar vertebrae
Terminates opposite the 4th lumbar vertebra by dividing into right and left COMMON ILIAC ARTERIES
The aorta undergoes an overall decrease in diameter from above downward after the origin of the celiac trunk.
Unpaired anterior branches of the aorta
celiac
SMA
IMA