Gut Book 5: Posterior Adominal Wall, diaphragm, Aorta, IVC & Lumbar Plexus

Question 1

Psoas major (O,I,A,N)

Answer 1

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

Question 2

Psoas minor

Answer 2

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

Question 3

Quadratus lumborum

Answer 3

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

Question 4

Iliacus

Answer 4

O: iliac fossa

I: lesser trochanter

A: flexes thigh; with lower limb stabilized flexes the pelvis on the thigh

n: femoral nerve

Question 5

Diaphragm

Answer 5

musculfascial septum which partitions the body cavity into thoracic and abdominopelvic cavities.

principal muscle of inspiration

dome shaped; concave superior surface

Question 6

Action of diaphragm

Answer 6

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)

Question 7

How high does the concave superior surface of the diaphragm extend?

Answer 7

as high as the 5th rib

Question 8

muscle arrangement of diaphragm

Answer 8

radially arranged around a central tendon

Question 9

what covers the superior surface of the diaphragm

Answer 9

endothoracic fascia and pleura

Question 10

What covers the inferior surface of the diaphragm

Answer 10

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.

Question 11

Subdivisions of the diaphragm

Answer 11

sternal, costal, lumbar portions

Question 12

Sternal portion of the diaphragm

Answer 12

two muscular slips arising from the inner surface of the xiphoid process that pass directly posteriorly until they fuse with the central tendon.

Question 13

Costal portion of the diaphragm

Answer 13

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

Question 14

lumbar portion of the diaphragm

Answer 14

crura and fibers originating from arcuate ligaments

Question 15

Right crus

Answer 15

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

Question 16

Left crus

Answer 16

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

Question 17

fibers originating from arcuate ligaments

Answer 17

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

Question 18

Medial arcuate ligament

Answer 18

= 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.

Question 19

Lateral arcuate ligament

Answer 19

= 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

Question 20

Vertebral costal trigone

Answer 20

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.

Question 21

Central tendon of the diaphragm

Answer 21

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

Question 22

Foramina of the diaphragm

Answer 22

Caval foramen, esophageal hiatus, aortic hiatus

Question 23

Caval foramen

Answer 23

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.

Question 24

Esophageal hiatus (of the diaphragm)

Answer 24

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

Question 25

Aortic hiatus (of the diaphragm)

Answer 25

located behind the confluence of the crura at the level of the 12th thoracic vertebra transmits the aorta and the thoracic duct

Question 26

Other structures which traverse the diaphragm

Answer 26

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

Question 27

arteries of the superior surface of the diaphragm

Answer 27

1. pericardicophrenic a. - from internal thoracic a. 2. musculophrenic a. - from internal thoracic a. 3. superior phrenic a.- last paired branches arising from descending thoracic aorta

Question 28

arteries of the inferior surface of the diaphragm (how do they get there? What branches are there?)

Answer 28

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.

Question 29

Veins of the superior surface of the diaphragm

Answer 29

Correspond to the arteries, drain to internal thoracic veins

Question 30

veins of the inferior surface of the diaphragm

Answer 30

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

Question 31

Nerves to the diaphragm (motor and sensory)

Answer 31

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

Question 32

referred pain from the gallbladder to the right shoulder

Answer 32

``` 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. ```

Question 33

Aorta: course

Answer 33

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.

Question 34

Unpaired anterior branches of the aorta

Answer 34

celiac SMA IMA

Question 35

paired visceral branches of the aorta

Answer 35

superior & inferior suprarenal renal gonadal (testicular & ovarian)

Question 36

paired parietal branches of the aorta

Answer 36

inferior phrenic | lumbar aa. 1-4

Question 37

unpaired parietal branches of the aorta

Answer 37

median sacral

Question 38

Branches of the aorta listed in order of occurrence from above downward:

Answer 38

``` 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) ```

Question 39

Gonadal aa. course (Testicular a.)

Answer 39

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.

Question 40

gonadal aa. relations

Answer 40

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.

Question 41

Branches from the testicular artery

Answer 41

provides branches to the ureter, ductus deferens and testis

Question 42

Ovarian artery

Answer 42

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.

Question 43

Lumbar aa.

Answer 43

four paired arteries, corresponding to the intercostal arteries of the thorax, located at LV1,2,3,4

Question 44

Lumbar aa. course

Answer 44

first on the anterior surface, then on the lateral surface of the vertebra deep to the psoas and lumbar plexus.

Question 45

lumbar aa. branches

Answer 45

anterior- smaller; extend only a short distance beyond the quadratus lumborum into the posterolateralabdominal wall posterior- larger; divides into spinal branches and muscular branch

Question 46

spinal branches of the lumbar aa

Answer 46

enter interverteral foramen to provide branches to the spinal cord, meninges and vertebra

Question 47

muscular branch of lumbar arteries

Answer 47

to erector spinae muscles

Question 48

Median sacral a. course

Answer 48

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

Question 49

median sacral a. branches

Answer 49

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.)

Question 50

terminal branches of aorta

Answer 50

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

Question 51

internal vs. external iliac arteries

Answer 51

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

Question 52

Aorta: relations: anterior surface

Answer 52

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

Question 53

aorta: relations: posterior surface

Answer 53

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

Question 54

Aortic Aneurysm

Answer 54

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

Question 55

Inferior Vena Cava (IVC): formation

Answer 55

formed by the union of common iliac veins at LV5

Question 56

IVC: course

Answer 56

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

Question 57

Tributaries to the IVC

Answer 57

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)

Question 58

What join the left renal v. prior to its joining the IVC?

Answer 58

Both the left inferior phrenic v., receiving the left suprarenal v., and the left gonadal v.

Question 59

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?

Answer 59

3 paired hepatic vv draining hepatic venous sinusoids

Question 60

Paired parietal tributaries to the IVC

Answer 60

1. right inferior phrenic vv. 2. lumbar vv.(drainage of lumbar vv. 1&2 is variable) 3. common iliac vv.

Question 61

discuss the fate of the right and left ascending lumbar vv.

Answer 61

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.

Question 62

how do the lumbarvv. communicate with the vertebral venous plexus?

Answer 62

they receive intervertebral vv.

Question 63

Summary of IVC tributaries from inferior to superior

Answer 63

``` common iliac vv lumbar vv. renal vv. rt. gonadal v. rt. suprarenal vv. rt. & sometimes lt. inferior phrenic v. ```

Question 64

Relations of IVC- anterior

Answer 64

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

Question 65

Relations of IVC- posterior

Answer 65

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.

Question 66

what is the lumbar plexus composed of?

Answer 66

ventral rami of spinal nerves L1-L4 with contribution from T12 (50% occurrence)

Question 67

Where do nerves of lumbar plexus emerge?

Answer 67

all of nerves formed within the lumbar plexus in some way emerge from undercover of the psoas major muscle

Question 68

lumbar plexus provides motor innervation to...

Answer 68

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.

Question 69

What does lumbosacral trunk contribute to the sacral plexus

Answer 69

primary ventral rami of L4 and L5

Question 70

What do abdominal spinal nerves receive from the sympathetic trunk

Answer 70

each one receives rami communicantes

Question 71

Lumbar Plexus: Subcostal n. (T12): course

Answer 71

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

Question 72

Lumbar Plexus: Subcostal n. (T12): branches to...

Answer 72

rectus abdominis, pyramidalis, TA, IAO, EAO | skin of the anterior and lateral body wall and upper gluteal area

Question 73

Branches of the lumbar plexus: Iliohypogastric n. (course)

Answer 73

(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

Question 74

Branches of the lumbar plexus: Iliohypogastric n. (provides branches to...)

Answer 74

TA, IAO, EAO Skin of the suprapubic region Skin of the gluteal region

Question 75

Branches of the lumbar plexus: Ilioinguinal n. (course)

Answer 75

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

Question 76

Branches of the lumbar plexus: ilioinguinal n. (provides branches to...)

Answer 76

1. IAO and TA 2. Skin of the root of the penis and anterior scrotum; in the female, the skin of the mons pubis and labia majus 3. Skin of the medial and upper portion of the thigh

Question 77

Branches of the lumbar plexus: Genitofemoral n. (course)

Answer 77

(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.

Question 78

Branches of the lumbar plexus: Genitofemoral n. (divides into...)

Answer 78

Genital branch (lateral) and femoral branch (medial)

Question 79

Genital branch of the genitofemoral nerve

Answer 79

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)

Question 80

Femoral branch of the genitofemoral nerve

Answer 80

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.

Question 81

Branches of the lumbar plexus: lateral femoral cutaneous n.

Answer 81

(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

Question 82

Branches of the lumbar plexus: femoral n.

Answer 82

(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.

Question 83

Branches of the lumbar plexus: Obturator n.

Answer 83

(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

Question 84

Branches of the lumbar plexus: Accessory obturator n.

Answer 84

(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

Question 85

Branches of the lumbar plexus: Lumbosacral trunk

Answer 85

(L4, L5) Located medially, deep to the psoas major descends on the ala of the sacrum to join the sacral plexus in the pelvis