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
paired visceral branches of the aorta
superior & inferior suprarenal
renal
gonadal (testicular & ovarian)
paired parietal branches of the aorta
inferior phrenic
lumbar aa. 1-4
unpaired parietal branches of the aorta
median sacral
Branches of the aorta listed in order of occurrence from above downward:
inferior phrenic aa (T12) celiac trunk (T12-L1) middle suprarenal aa. (L1) 1st lumbar aa. (L1) suuperior mesenteric a. (L1) renal aa. (L2) gonadal aa. (L2) 2nd lumbar aa. (L2) inferior mesenteric a. (L3) 3rd lumbar aa. (L3) 4th lumbar aa. (L4) median sacral a. (L4) common iliac aa. (L4)
Gonadal aa. course (Testicular a.)
arises from anterior surface of aorta inferior to renal vessels
courses retroperitoneally in an obliquely inferior direction across the psoas to enter the deep inguinal ring.
gonadal aa. relations
right- posterior- crosses the IVC, right psoas, right ureter, right external iliac artery
right- anterior- crossed by the right colic and ileocolic vessels
left- posterior- crosses the left psoas, left ureter and the left external iliac artery
left- anterior- crossed by left colic and sigmoidal aa.
Branches from the testicular artery
provides branches to the ureter, ductus deferens and testis
Ovarian artery
has the same course as the testicular artery as far as the brim of the pelvis. Medial to the pelvic brim the ovarian artery traverses the suspensory ligament of the ovary to gain the ovary and uterine tube.
Lumbar aa.
four paired arteries, corresponding to the intercostal arteries of the thorax, located at LV1,2,3,4
Lumbar aa. course
first on the anterior surface, then on the lateral surface of the vertebra deep to the psoas and lumbar plexus.
lumbar aa. branches
anterior- smaller; extend only a short distance beyond the quadratus lumborum into the posterolateralabdominal wall
posterior- larger; divides into spinal branches and muscular branch
spinal branches of the lumbar aa
enter interverteral foramen to provide branches to the spinal cord, meninges and vertebra
muscular branch of lumbar arteries
to erector spinae muscles
Median sacral a. course
arises from the posterior surface of the aorta at LV4 (just proximal to the bifurcation)
descends on the surface of the fourth and fifth lumbar vertebrae, sacrum and coccyx
median sacral a. branches
5th lumbar aa- same course as first four lumbar aa.
provides branches to the rectum and posterior pelvic wall
will anastomose with the lateral sacral artery (branch of internal iliac a.)
terminal branches of aorta
common iliac arteries
- formed via the aortic bifurcation opposite LV4
- course on the surface of the pelvic brim
- divide into internal and external iliac arteries
internal vs. external iliac arteries
internal provides branches to pelvis
external continues on the lateral surface of the pelvic brim to eventually pass beneath the inguinal ligament and become the femoral artery
Aorta: relations: anterior surface
from above downward after (a)
a. posterior body wall peritoneum, root of the mesentery, small intestine
b. Right & left celiac ganglia, aorticorenal ganglia
c. formation of portal vein (approx. junction of splenic and superior mesenteric vv)
d. pancreas
e. part 4 of the duodenum
f. left renal vein
g. autonomic nerve plexuses (aortic, intermesenteric)
h. pre and para aortic lymph nodes and their lymphatic plexuses
aorta: relations: posterior surface
from above downward after “a”
a. Anterior longitudinal spinal ligament
b. Thoracic duct (variable)
c. cisterna chyli (variable)
d. posterior aortic lymphatic plexuses
e. left lumbar veins
Aortic Aneurysm
result of inherent wall weakness (disease of tunica media and adventitia) complicated by smoking, hypertension, atherosclerosis, trauma
occurs most often between the origin of the renal aa. and the aortic bifurcation
violent pain starts in the abdomen and radiates to the back
often results in death due to massive retroperitoneal bleed
Inferior Vena Cava (IVC): formation
formed by the union of common iliac veins at LV5
IVC: course
courses on the right lateral surface of all lumbar and lower thoracic vertebrae paralleling the aorta.
passes through the subsance of the liver where it receives the hepatic veins
passes through the central tendon of the diaphragm at the level of TV8 to directly join the right atrium of the heart
Tributaries to the IVC
correspond to the paired visceral and parietal branches of the aorta.
NOTE: the unpaired visceral tributaries contribute to the hepatic portal vein and do NOT join the IVC
Paired visceral tributaries:
right suprarenal vv. (left drains to left renal v)
renal vv.
right gonadal vv. (testicular and ovarian)
What join the left renal v. prior to its joining the IVC?
Both the left inferior phrenic v., receiving the left suprarenal v., and the left gonadal v.
What drain directly to the IVC in the segment that passes through the substance of the liver prior to its passing through the caval foramen?
3 paired hepatic vv draining hepatic venous sinusoids
Paired parietal tributaries to the IVC
- right inferior phrenic vv.
- lumbar vv.(drainage of lumbar vv. 1&2 is variable)
- common iliac vv.
discuss the fate of the right and left ascending lumbar vv.
arise from the common iliac vv., course superiorly deep to the psoas, unite lumbar vv. and join the subcostal vv. to form the azygos and hemiazygos vv., respectively, effectively joining IVC and SVC venous systems.
how do the lumbarvv. communicate with the vertebral venous plexus?
they receive intervertebral vv.
Summary of IVC tributaries from inferior to superior
common iliac vv lumbar vv. renal vv. rt. gonadal v. rt. suprarenal vv. rt. & sometimes lt. inferior phrenic v.
Relations of IVC- anterior
a. visceral surface of the liver
b. portal vein
c. common bile duct
d. parts 2 & 3 of the duodenum
3. head of the pancreas
f. root of the mesentery
g. small intestine
h. right gonadal vessels
i. right lumbar lymph nodes
j. right common iliac artery
Relations of IVC- posterior
a. right crus of the diaphragm
b. right sympathetic splanchnic nerves
c. anterior longitudinal spinal ligament and spinal column
d. right celiac ganglion
e. right suprarenal gland
f. right sympathetic trunk
g. right psoas muscles
h. arteries from superior to inferior: right inferior phrenic a., right middle suprarenal a., right renal a. and the right lumbar aa.
what is the lumbar plexus composed of?
ventral rami of spinal nerves L1-L4 with contribution from T12 (50% occurrence)
Where do nerves of lumbar plexus emerge?
all of nerves formed within the lumbar plexus in some way emerge from undercover of the psoas major muscle
lumbar plexus provides motor innervation to…
muscles of the anterior and posterior abdominal wall, anterior and medial thigh as well as cutaneous innervation to the anterior abdominal wall, gluteal region, perineum and lower limb.
What does lumbosacral trunk contribute to the sacral plexus
primary ventral rami of L4 and L5
What do abdominal spinal nerves receive from the sympathetic trunk
each one receives rami communicantes
Lumbar Plexus: Subcostal n. (T12): course
emerges lateral to the psoas major deep to the lateral arcuate ligament
traverses the quadratus lumborum, pierces the transversus abdominis to run between it and the IAO
Lumbar Plexus: Subcostal n. (T12): branches to…
rectus abdominis, pyramidalis, TA, IAO, EAO
skin of the anterior and lateral body wall and upper gluteal area
Branches of the lumbar plexus: Iliohypogastric n. (course)
(L1; T12-L1 50%)
emerges from the lateral border of the psoas (medial arcuate ligament)
traverses the quadatus lumborum to pierce the transversus abdominis muscle at its medial border
travels forward between the TA and IAO
Pierces the IAO several centimeters medial and inferior to the ASIS to run between the IAO and EAO
Branches of the lumbar plexus: Iliohypogastric n. (provides branches to…)
TA, IAO, EAO
Skin of the suprapubic region
Skin of the gluteal region
Branches of the lumbar plexus: Ilioinguinal n. (course)
same approximate course as the iliohypogastric nerve, but slightly more inferior
pierces the IAO near the deep inguinal ring
traverses the inguinal canal and will emerge from the superficial inguinal ring on the superior surface of the spermatic cord
Branches of the lumbar plexus: ilioinguinal n. (provides branches to…)
- IAO and TA
- Skin of the root of the penis and anterior scrotum; in the female, the skin of the mons pubis and labia majus
- Skin of the medial and upper portion of the thigh
Branches of the lumbar plexus: Genitofemoral n. (course)
(L1-L2)
passes through the substance of the of the psoas from L1 and L2 to emerge on its surface at LV3 or LV4.
Descends on the surface of the psoas deep to the psoas fascia.
Branches of the lumbar plexus: Genitofemoral n. (divides into…)
Genital branch (lateral) and femoral branch (medial)
Genital branch of the genitofemoral nerve
enters the deep inguinal ring, traverses the inguinal canal; innervates the cremaster muscle, the skin of the scrotum (labia) and thigh adjacent to the scrotum (labia)
Femoral branch of the genitofemoral nerve
passes deep to the inguinal ligament on the surface of the external iliac artery to enter the femoral sheath; pierces the femoral sheath and deep fascia of the thigh to innervate the skin of the thigh lateral to the distribution of the ilioinguinal nerve.
Branches of the lumbar plexus: lateral femoral cutaneous n.
(L2, L3)
emerges from the lateral border of the psoas near LV4
crosses the iliac fossa deep to the iliacus fascia
passes under the inguinal ligament near the ASIS
innervates the skin of the anterolateral and posterolateral thigh as far as the knee
Branches of the lumbar plexus: femoral n.
(L2,3,4)
Largest branch of the lumbar plexus
passes inferiorly from its origin undercover of the lateral border of the psoas major
continues inferiorly between the psoas and iliacus muscles
passes under the inguinal ligament to enter the femoral triangle
innervates: muscles of the anterior thigh including: iliacus, sartorius, quadriceps and pectineus
skin of the anterior thigh and medial leg.
Branches of the lumbar plexus: Obturator n.
(L2,3,4)
Descends from its origin along the medial border of the psoas posterior and lateral to the common iliac vessels
Passing lateral to the internal iliac vessels it accompanies the obturator vessels through the obturator foramen
In the thigh it innervates:
a. adductor compartment musculature
b. the hip join
c. skin of the medial thigh
Branches of the lumbar plexus: Accessory obturator n.
(L3,4)- 9% occurrence
medial to the psoas
follows the path of the external iliac vein into the thigh
enters the thigh deep to the pectineus which it innervates
May communicate with the anterior division of the obturator nerve
Branches of the lumbar plexus: Lumbosacral trunk
(L4, L5)
Located medially, deep to the psoas major
descends on the ala of the sacrum to join the sacral plexus in the pelvis
