Abdomen 4 - Posterior Abdominal Wall

Question 1

what is the sacral promontory?

Answer 1

landmark where lumbar spine transitions to sacrum

Question 2

what type of curvature is the sacral region?

Answer 2

primary curvature/kyphosis - develops during foetal development

Question 3

iliopsoas muscle - origins? insertions?

Answer 3

origins:
- iliacus = iliac fossa
- psoas major = T12-L5 vertebral bodies; L1-5 IVDs & transverse processes

insertion: lesser trochanter of femur

Question 4

action of the iliopsoas?

Answer 4

primary hip flexor (hip flexion)

Question 5

psoas minor - origin, insertion, action?

Answer 5

origin: T12-L1 vertebral bodies

insertion: pectinate line (femur)

action: assists trunk flexion - minimal involvement
(variable presentation; not everyone has this muscle)

Question 6

what nerve plexus is embedded within the psoas major?

Answer 6

lumbar plexus (T12-L4)

Question 7

origin, insertion & action of psoas major?

Answer 7

origin: transverse processes of T12-L4

insertion: fibres pass inguinal ligament & join with iliacus - forms iliopsoas & inserts on *lesser trochanter of femur&

actions: flexes thigh at hip joint & flexes trunk

Question 8

origin & insertion of quadratus lumborum?

Answer 8

origin: iliac crest

insertion: 12th rib & transverse processes of L1-4

Question 9

what happens with bilateral contraction of the quadratus lumborum?

Answer 9

extends vertebral column

Question 10

what happens with unilateral contraction of the quadratus lumborum?

Answer 10

lateral flexion of trunk (ipsilateral/ same side as contraction)

Question 11

the quadratus lumborum is a posterior continuation of WHAT MUSCLE

Answer 11

transversus abdominis

Question 12

what is the central tendon of the diaphragm?

Answer 12

an aponeurosis that serves as the main insertion site for diaphragm muscle fibres

Question 13

why is the right dome of the diaphragm higher than the left?

Answer 13

presence of liver makes right dome higher

stomach & spleen makes left dome lower

Question 14

what is the function of the arcuate ligaments?

Answer 14

provide fascial attachments to posterior abdominal wall muscles - form a continuous structural layer

Question 15

what are the three arcuate ligaments (from medial to lateral)? what do they attach to?

Answer 15

median arcuate ligament - no attachments; aorta passes posteriorly

medial arcuate ligament - attaches to psoas major

lateral arcuate ligament - attaches to quadratus lumborum

Question 16

what attaches to the lateral arcuate ligament?

Answer 16

quadratus lumborum

Question 17

what attaches to the medial arcuate ligament?

Answer 17

psoas major

Question 18

what part of the diaphragm secures the oesophagus at the midline? how?

Answer 18

right & left crura of the diaphragm - encircle the oesophageal hiatus to secure the oesophagus

Question 19

what is the difference between the right and left crura of the diaphragm?

Answer 19

right crus is longer - attaches to L1-3

left crus is shorter - attaches to L1-2

Question 20

which diaphragm crus attaches at L1-2?

Answer 20

left crus (shorter than the right)

Question 21

what contents pass through the caval opening?

Answer 21

(at T8) - IVC & right phrenic nerve

Question 22

what passes through the diaphragm at T10?

Answer 22

oesophagus
anterior & posterior vagal trunks

Question 23

what passes with the aorta through the aortic hiatus?

Answer 23

thoracic duct
azygos vein

Question 24

at what thoracic level does the right phrenic nerve pass through the diaphragm

Answer 24

T8 - passes through caval opening with IVC

Question 25

does the aorta pass through the diaphragm?

Answer 25

NO - aorta travels posterior to the diaphragm between the crura (at the level of T12)

Question 26

how does the left phrenic nerve pass through the diaphragm?

Answer 26

perforates the diaphragm rather than passing through a hiatus

Question 27

which phrenic nerve passes with the IVC through the diaphragm?

Answer 27

right phrenic nerve

Question 28

what muscle compartments/subsets does the thoracolumbar fascia separate?

Answer 28

separates deep back muscles from posterior abdominal wall muscles (then converges into lumbar fascia)

Question 29

what fascia serves as an attachment point for muscles like the internal & external obliques?

Answer 29

lumbar fascia - attachment point for anterolateral abdominal muscles

Question 30

at what vertebral level does the abdominal aorta begin and end?

Answer 30

begins at T12 (aortic hiatus) ends at L4 (bifurcation into common iliac arteries)

Question 31

which branches of the abdominal aorta are unpaired and supply the GI tract?

Answer 31

midline unpaired branches - coeliac trunk (T12) = foregut - superior mesenteric artery (L1) = midgut - inferior mesenteric artery (L3) = hindgut

Question 32

at what vertebral level does the IMA come off the aorta?

Answer 32

L3

Question 33

at what vertebral level does the SMA come off the aorta?

Answer 33

L1

Question 34

at what vertebral level does the coeliac trunk come off the aorta?

Answer 34

T12

Question 35

which paired visceral branches of the abdominal aorta supply organs?

Answer 35

renal arteries gonadal arteries - testicular/ovarian suprarenal arteries (to adrenals)

Question 36

what are the paired posterolateral branches of the abdominal aorta?

Answer 36

lumbar arteries - one from each lumbar vertebral level; supply the posterior abdominal wall and vertebrae

Question 37

what do the lumbar arteries supply?

Answer 37

supply the posterior abdominal wall and vertebrae

Question 38

what are the three vascular planes of the abdominal aorta?

Answer 38

unpaired midline arteries paired visceral arteries paired posterolateral arteries

Question 39

what vertebral levels does the lumbar plexus originate from?

Answer 39

T12-L4

Question 40

where is the lumbar plexus located?

Answer 40

within the psoas major muscle, with most nerves running behind or in front of it

Question 41

which nerve of the lumbar plexus is considered an intercostal nerve?

Answer 41

subcostal nerve (T12) - called "subcostal" because it arises below the last rib

Question 45

which two nerves of the lumbar plexus wrap around the top of psoas major?

Answer 45

iliohypogastric (L1) ilioinguinal (L1)

Question 46

what are are the branches of the genitofemoral nerve (L1-2)?

Answer 46

genital branch femoral branch

Question 47

which nerve of the lumbar plexus is vulnerable to compression under the inguinal ligament?

Answer 47

lateral femoral cutaneous nerve (L2-3)