anatomy of abdomen lecturer notes from the University of Rwanda

1. Posterior abdominal wall and
Retroperitoneal Organs
Prof. Julien GASHEGU

2. The structures of the posterior abdominal wall
and retroperitoneal space include:
• Bones: vertebrae colum, ribs and pelvic bones
• Muscles: including psoas major and quadratus lumborum and
diaphragm
• The abdominal aorta and its branches
• The inferior vena cava (IVC) and its tributaries
• The kidneys.
• The ureters.
• The adrenal (suprarenal) glands.
• The lumbar sympathetic trunks and plexuses and the lumbar plexus
. Lymphatic vessels

4. The diaphragm
 The diaphragm is a dome-shaped septum that separate the
thoracic and abdominal cavities.
 It is composed of a peripheral muscular
portion which inserts into a central
aponeurosis, the central tendon.
 The muscular part has three component
origins:
- A costal part: wide muscular slips that are
attached to the inner aspects of the lower six ribs
and their costal cartilages.
- A sternal part: consists of two small slips arising
from the deep surface of the xiphoid process.

6.  A vertebral part: this comprises the crura and arcuate
ligaments.
 The right crus arises from the front of the L1–3 vertebral bodies
and intervening discs. Some fibres from the right crus pass
around the lower oesophagus.
 The left crus originates from L1 and L2 only.
 The medial arcuate ligament is made up of thickened fascia which
overlies psoas major and is attached medially to the body of L1
and laterally to the transverse process of L1.
 The lateral arcuate ligament is made up of fascia which overlies
quadratus lumborum from the transverse process of L1 medially
to the 12th rib laterally.
 The median arcuate ligament is a fibrous arch which connects left
and right crura.

8. Openings (hiatus, apertures) in the
diaphragm: passage of structures
between the abdomen and thorax
- The opening for the inferior vena cava(Caval opening):
transmits the inferior vena cava and right phrenic nerve, at T8
level
- The oesophageal opening: transmits the oesophagus, vagi
and branches of the left gastric artery and vein, at T10 level
- The aortic opening: transmits the aorta, thoracic duct and
azygos vein, at T12 level
- The left phrenic nerve passes into the diaphragm as a solitary
structure.
- 2 small opening in each crus of diaphragm for the greater and
lesser splanchnic nerves
- the sympathetic trunk and the least splanchnic nerve pass
deep to the medial arcuate ligament

10. Nerve and artery supply of the
diaphragm
Motor supply: the entire motor supply arises from the phrenic
nerves (C3,4,5). Diaphragmatic contraction is the mainstay of
inspiration
 Sensory supply: the periphery of the diaphragm receives
sensory fibres from the lower intercostal nerves. The sensory
supply from the central part is carried by the phrenic nerves.
 Artery supply: the arteries suppling the thoracic surface are
pericardiacophrenic and musculophrenic arteries branches of
the internal thoracic arteries and superior phrenic arteries
branches of the thoracic aorta. The abdominal surface is
supplied by the inferior phrenic arteries branches of the
abdominal aorta

11. Muscles of Posterior abdominal wall
Those muscles are supplied by
local branches of adjacent anterior
rami (lumbar or sacral plexuses)

13. Psoas Major and Psoas Minor
• Psoas major is a long, thick and fusiform
muscle that is lateral to the lumbar spine
• It attaches on the T12 – L4 vertebral bodies
and transverse processes
• It passes deep to the inguinal ligament
• It attaches on the lesser trochanter
• Psoas minor is often absent
• It attaches of T12 and L1 bodies and lies
anterior to psoas mijor, to insert on the
iliopectineal eminence

15. Iliacus and Quadratus Lumborum
• Iliacus is a triangular muscle that arises from the
iliac fossa and lateral part of sacrum
• Its tendon fuses with the psoas major to form the
iliopsoas tendon that attaches on the lesser
trochanter
• Quadratus Lumborum is a quadralateral muscle
that forms the thick posterior sheet of the posterior
abdominal wall
• It attaches superiorly on lower border of the 12th rib
and inferiorly to the iliolumbar ligament and the iliac
crest

19. Abdominal aorta
• The Abdominal Aorta is 13 cm long, begins at aortic hiatus in
diaphragm at T12 level and ends at the level of L4 by
bifurcating in right and left common iliac arteries
• The Abdominal Aorta branches can be classified as parietal or
visceral; paired or unpaired:
1. Unpaired branches (4):
• Celiac trunk at T12 that divides into common hepatic, left
gastric and splenic arteries
• Superior mesenteric at L1
• Inferior mesenteric at L3
• Median Sacral at L4
2. Paired visceral branches (3 pairs): Supra-renal, Renal at L1,
Gonadic (ovarian or testicular arteries) at L2
3. Paired parietal segmental branches (5 pairs): inferior phrenic or
diaphragmatic and 4 lumbar arteries

22. Relations of the Abdominal
Aorta
The important anterior relations are from
superior to inferior:
• Esophagus
• Stomach
• Celiac plexus and ganglions
• Body of pancreas and splenic vein
• Left renal vein
• 3rd part of duodenum
• Coils of small intestine

23. Inferior vena cava

24. Inferior Vena Cava (IVC)
• The IVC begins at L5 level by unions of the right and
left common iliac veins
• It ascends on the right side of L5-L3 vertebral bodies
and on right psoas major to right of aorta
• It continues in a deep groove at posterior surface of
the liver, diaphragm and drains in the right atrium
• Its tributaries correspond to paired visceral and
parietal (right suprarenal vein, right gonadic vein,
renal veins, note: left suprarenal and gonadic veins
drain in the left renal vein that drains into IVC)
• The unpaired visceral veins collect into portal vein
that drain into hepatic veins that eventually drain into
the IVC

25. Contrasted CT scan
showing thrombosis
in the IVC

26. Tributaries of IVC
• Lumbar veins course
anterior to the spinal
transverse processes
and parallel the lumbar
arteries
• They connect the IVC to
the azygos venous
system on the right side
and hemiazygos venous
system on the left side of
the thorax

27. Retroperitoneal lymphatic
• Apart of abdominal cavity
and viscera, lower limbs,
perineum, and external
genitalia drain into the
retroperitoneum via iliac
lymph vessels
• The cisterna chyli tends to
lie within the thorax just to
the right of the aorta in a
retro-crural position

28. Nervous system in the
Retroperitoneum
• It is part of the peripheral nervous system
• It has both autonomic and somatic nerves
• The autonomic nerves: afferent and efferent
innervation of organs, blood vessels, glands,
and smooth muscles –2 synapsing peripheral
nerves (pre-ganglionic and post-ganglionic)
• The somatic nerves supply afferent and
efferent innervationto the skin, skeletal
muscles, and joints

29. Retroperitoneal nervous plexuses

30. Autonomic Nervous System
• Sympathetic and parasympathetic fibers
• Sympathetic preganglionic fibers: spinal
nerve T1 –L3: The chain courses vertically
along the anterolateral aspect of the spine
just medial to the psoas muscle
• Parasympathetic preganglionic fibers begin
in the cranial (brainstem) and sacral spinal
cord

31. Sympathetic pathways
• Three possible courses of preganglionic
fibers:
• To various autonomic plexuses (splanchnic
nerves)-> ganglion (synapse) ->
postganglionic fibers -> viscera
• Synapse within the sympathetic chain ganglia
and send postganglionic fibers to the body
wall and lower extremities
• Can proceed directly to the adrenal gland
without synapsing -> catecholamines

32. Autonomous nerve plexuses
• Associated with the primary branches of the
aorta
• Autonomic plexuses are the –celiac - superior
hypogastric - inferior hypogastric plexuses
• sympathetic input from preganglionic sympathetic
chains grouped into greater, lesser and least
thoracic splanchnic nerves (from T5-T12),
lumbar and sacral splanchnic nerves
• parasympathetic input via the vagus nerve and
pelvic splanchnic nerves from the sacral plexus

33. Sympathetic
pathways

34. Autonomous nerves plexuses

35. Lumbar Plexus in the posterior abdominal wall
See for details
Anatomy 1 module

36. Adrenal glands, Kidneys and
Ureters

38. Adrenal (Suprarenal) Gland
• In adults: 5 g and 3 to
5 cm in greatest
dimension
• Yellow-orange
• Enclosed in the peri-
renal (Gerota) fascia
• Separated from the
upper pole of the
kidneys by a layer of
connective tissue.

39. Adrenal gland relationship
• The right gland is
pyramidal and more
superiorly located
• It is almost directly cranial to
the upper pole of the right
kidney
• Anterolaterally: the liver,
• Anteromedially: the
duodenum,
• Medially: IVC
• Note: often a retro-caval
extension of one wing.

40. Adrenal gland relationship
• The left gland: more
crescenteric and
medial to the upper
pole of the left
kidney.
• The upper and
anterior aspects are
related to:
• the stomach
• the tail of the
pancreas
• the splenic vessels

42. Position
• The adrenals are small glands which lie in the
renal fascia on the upper poles of the kidneys.
• The right gland lies behind the right lobe of the
liver and immediately posterolateral to the IVC.
• The left adrenal is anteriorly related to the lesser
sac and stomach.

44. Adrenal (suprarenal) glands.
• The adrenal glands comprise an outer cortex
and inner medulla.
• The cortex is responsible for the production of
steroid hormones (glucocorticoids,
mineralocorticoids and sex steroids).
• The medulla acts as a part of the autonomic
nervous system.

45. • The medulla receives sympathetic
preganglionic fibres from the greater
splanchnic nerves which stimulate the
medulla to secrete noradrenaline and
adrenaline into the bloodstream
• The medulla is composed of chromaffin
cells (neural crest origin) that receive
stimuli directly from presynaptic
sympathetic fibers from the sympathetic
chains => secretion of catecholamines by
the adrenal medulla is under sympathetic
control.

46. Adrenal gland cortex structure
• The adrenal cortex:
mesodermal origin
• Up to 90% of the adrenal mass
• Three layers: from external to
internal
-zona glomerulosa->
mineralocorticoides
(aldosterone)
-zona fasciculata->
glucocorticoides (cortisol)
-zona reticularis-> sex steroids
(androgens)
• (mneumonic: GFR!)

47. Adrenal gland supply
• Three sources of arterial supply:
-Superiorly, branches from the inferior phrenic
artery
-Middle: a branch from the aorta.
-Inferiorly: branches from the ipsilateral renal
artery supply
• The venous drainage by single large veins
• The lymphatic drainage follows the course of
the veins and empties into para-aortic lymph
nodes

49. The KIDNEYS

50. Kidney: gross appearance
• Color: reddish brown
• Weight in adults: 150 g in male and 135 g in
the female
• Size in adults: 10 to 12 cm vertically,
• 5 to 7 cm transversely, and 3 cm in the A-P
dimension
• Right kidney tends to be shorter and wider
(liver!)
• In children: relatively larger with more
prominent fetal lobations that disappear by the
first year of life

52. Structure
• The kidney has its own fibrous capsule and is surrounded by
perinephric fat which, in turn, is enclosed by renal fascia.
• Each kidney is approximately 10–12 cm long and consists of:
– an outer cortex,
– an inner medulla
– a pelvis.
• The hilum of the kidney is situated medially and transmits
from anterior to posterior the renal vein, renal artery, ureteric
pelvis, lymphatics and sympathetic vasomotor nerves.
• The renal pelvis divides into two or three major calices and
these, in turn, divide into minor calices which receive urine
from the medullary pyramids by way of the papillae.

57. Position
• The kidneys lie in the retroperitoneum
against the posterior abdominal wall.
• The right kidney lies approximately 1 cm
lower than the left.

59. Relations: Posterior Surface

60. Relations:

61. Relations: anterior surface

62. Relations:

65. Kidney hilum
• The renal pedicle consists
of a single artery and a
single vein that enter the
kidney via the renal hilum
• They branch from the
aorta and IVC just below
the SMA at level of the L2
vertebra
• The vein is anterior to the
artery
• The renal pelvis and
ureter are located farther
posterior.

66. Blood supply
• The renal arteries arise from the aorta at the
level of L2.
• Together, the renal arteries direct 25% of the
cardiac output towards the kidneys.
• Each renal artery divides into five segmental
arteries at the hilum which, in turn, divide
sequentially into lobar, interlobar, arcuate and
cortical radial branches.
• The cortical radial branches give rise to the
afferent arterioles which supply the glomeruli
and go on to become efferent arterioles.

67. Vessels of Kidneys
• The differential pressures between afferent
and efferent arterioles lead to the production
of an ultrafiltrate which then passes through,
and is modified by, the nephron to produce
urine.
• The right renal artery passes behind the IVC.
The left renal vein is long as it courses in
front of the aorta to drain into the IVC.
• Lymphatic drainage: to the para-aortic
lymph nodes.

68. Ureters
• Portions: abdominal,
pelvic and intravesical.
• Structure:
– 20–30 cm long
– muscular wall
– lined by transitional
epithelium.
– At operation it can be
recognized by its
peristalsis.

70. The course of the ureters
• from the renal pelvis at the hilum
• It passes along the medial part of psoas
major behind, but adherent to the
peritoneum.
• Crosses the common iliac bifurcation
anterior to the sacro-iliac joint
• courses over the lateral wall of the pelvis
to the ischial spine.
• •

71. • At the ischial spine the ureter passes
forwards and medially to enter the bladder
obliquely.
• The intravesical portion of the ureter is
approximately 2 cm long and its passage
through the bladder wall produces a
sphincter-like effect.

73. • In the male the ureter is crossed
superficially near its termination by the vas
deferens.
• In the female the ureter passes above the
lateral fornix of the vagina but below the
broad ligament and uterine vessels.

77. Ureteric
constrictures

78. Blood supply
• As the ureter is an abdominal and pelvic
structure it receives a blood supply from
multiple sources:
• The upper ureter receives direct branches
from the aorta, renal and gonadal arteries.
• The lower ureter receives branches of the
internal iliac and inferior vesical arteries.