Anatomy: Posterior Abdominal Wall
The posterior abdominal wall consists of the lumbar vertebrae, surrounding muscles, fascia, and vessels. It is shaped by prominent structures like the lumbar vertebral column, abdominal aorta, and kidneys, and plays a vital role in housing various abdominal structures, nerves, and fat. The wall is also covered by endoabdominal fascia, providing structural integrity.
The posterior abdominal wall is mainly composed of:
5 Lumbar vertebrae + IV discs
posterior abdominal wall muscles
diaphragm
fascia
lumbar plexus
fat, nerves, vessels, lymph nodes
Key Terms
The posterior abdominal wall is mainly composed of:
5 Lumbar vertebrae + IV discs
posterior abdominal wall muscles
diaphragm
fascia
Posterior abdominal muscles include:
psoas
quadratus lumborum
iliacus
transverse abdominal
oblique muscles (laterall...
What is a marked central prominence in the posterior wall and creates two paravertebral ‘gutters’ on each side of it?
lumbar vertebral column
The deepest (most posterior) part of the lumbar vertebral ‘gutters’ is occupied by the…?
kidneys + their surrounding fat
What great vessel lies on the anterior aspect of the anteriorly protruding vertebral column?
abdominal aorta
In lean individuals, the lower abdominal aorta lies where?
close to the anterior abdominal wall
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| Term | Definition |
|---|---|
The posterior abdominal wall is mainly composed of: |
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Posterior abdominal muscles include: |
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What is a marked central prominence in the posterior wall and creates two paravertebral ‘gutters’ on each side of it? | lumbar vertebral column |
The deepest (most posterior) part of the lumbar vertebral ‘gutters’ is occupied by the…? | kidneys + their surrounding fat |
What great vessel lies on the anterior aspect of the anteriorly protruding vertebral column? | abdominal aorta |
In lean individuals, the lower abdominal aorta lies where? | close to the anterior abdominal wall |
Many structures lie anterior to the aorta which may be close to the anterior abdominal wall in thin people. These structures include: |
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The posterior abdominal wall is covered with a continuous layer of _____________? It lies between what two structures/layers? |
parietal peritoneum + the post. ab. muscles |
The fascia lining the posterior abdominal wall is continuous with what other fascia? | transversalis fascia (lines transverse abdominal muscle) |
PSOAS FASCIA | covers psoas major m. (psoas sheath) attached medially = lumbar vertebrae + pelvic brim superiorly = thickened to form medial arcuate ligament laterally = fuses with quadratus lumborum + thoracolumbar fascias Inferior (to iliac crest) = continuous with iliac fascia covering iliacus |
THORACOLUMBAR FASCIA | extensive fascial complex
(with muscles enclosed between them)
(NOT external obliques) |
What part of the thoracolumbar fascia is thin + transparent? What part is thick + strong? | thin+transparent = thoracic parts of the deep muscles thick+strong =** lumbar region** (lumbar = b/t 12th rib + iliac crest) |
The anterior layer of the thoracolumbar fascia covers which muscle + is continuous laterally with what structure? | COVERS = quadratus lumborum m. CONTINUOUS W. = aponeurotic origin of transverse abdominal m. |
ANTERIOR THORACOLUMBAR FASCIA = | quadratus lumborum fascia
attachments:
superiorly = thickens to form lateral arcuate ligament inferiorly = adheres to iliolumbar ligaments |
The main paired muscles in the posterior abdominal wall (3): | - Psoas major (inferolaterally) - Iliacus (lateral to inferior part of psoas major) - Quadratus lumborum (lateral to superior part of psoas major) |
PSOAS MAJOR MUSCLE (attachment, innervation, action) | Attachment: superior = transverse processes of lumbar vert.; sides of T12-L5 vert. bodies + discs Inferior = strong tendon to lessor tronchanter of femur Innervation: Lumbar Plexus (anterior L2-L4 spinal n. branches) Main action:
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ILIACUS MUSCLE (attachment, innervation, action) | Attachment: superior = superior 2/3 of iliac fossa; ala of sacrum; anterior sacroiliac ligaments Inferior = lesser tronchater of femur + shaft inferior to it; psoas major tendon Innervation: Femoral nerve (L2-L4) Main action:
- stabilizes hip joint
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QUADRATUS LUMBORUM MUSCLE (attachments, innervation, actions) | Attachment: superior = medial 1/2 interior border of 12th ribs + tip of lumbar transverse processes Inferior = iliolumbar ligament + internal lip of iliac crest Innervation: anterior branches T12 = L1-L4 spinal n. Main action: - extends + laterally flexes vertebral column - fixes 12th rib (inspiration) |
The iliopsoas has extensive and clinically important relations to which (8) structures? When any of these structures is diseased, movement of iliopsoas usually causes pain. |
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When intra-abdominal inflammation is suspected, what test is performed? | iliopsoas test lie on unaffected side + extend thigh on the affected side against the resistance of the examiner’s hand
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Why is it that disease of the intervertebral + sacroiliac joints may cause spasm of the iliopsoas (protective reflex)? | because. .. |
Adenocarcinoma of the pancreas in advanced stages invades the muscles and nerves of the posterior abdominal wall. What symptom does this cause + why? | excruciating pain
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Psoas Abscess & Turberculosis: Prevalence of tuberculosis (TB) has been greatly reduced, but still very present in some areas. TB of the vertebral column is quite common. How is this caused by hematogenous spread, and how does it cause a psoas abcess? | - hematogenous spread = infection may spread through blood to the vertebrae (esp. during childhood) = psoas abscess |
What occurs as a result of a psoas abscess? |
Pus can also reach psoas sheath from posterior mediastinum when thoracic vertebrae are diseased |
Nerves of the Posterior Abdominal Wall: Components of which nervous systems are associated with the posterior abdominal wall? | somatic + autonomic (visceral) nervous systems |
Nerves of the Posterior Abdominal Wall: What path do the subcostal nerves (anterior rami of T12) take to enter the abdomen and reach their target structures? |
- supply the external oblique + skin of the anterolateral abdominal wall |
Thoracolumbar out-flow = | Sympathetic nervous system |
Craniosaccreal out-flow = | Parasympathetic nervous system |
Nerves of the Posterior Abdominal Wall: What path do the lumbar spinal nerves (L1 - L5) take to enter the abdomin and reach their target structures? |
(divide into posterior + anterior rami) sensory + motor fibers |
The initial portions of the anterior rami of the L1, L2, (occasionally L3) spinal nerves give rise to what structures? What type of fibers to these convey to the lumbar sympathetic trunks? |
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Nerves of the Posterior Abdominal Wall: The abdominal part of the sympathetic trunks (lumbar sympathetic trunks), consist of 4 and _______________? These are continuous with the thoracic part of the trunks deep to what structure? | 4 lumbar paravertebral sympathetic ganglia + interganglionic branches that connect them
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Nerves of the Posterior Abdominal Wall: The lumbar sympathetic trunks descend on what surface of the lumbar vertebrae? These rest in a groove formed by what adjacent muscle? | anterolateral aspects of the vertebral bodies
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Nerves of the Posterior Abdominal Wall: Inferiorly, the lumbar sympathetic trunks cross what structure before continuing inferiorly into the pelvis as the sacral part of the trunks? | cross the sacral promontory |
For the innervation of the abdominal wall + lower limbs, synapses between the presynaptic and postsynaptic fibers occur … (where)? Postsynaptic sympathetic fibers travel from the lateral aspect of the trunks via _ to the anterior rami? |
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Which nerve fibers become the thoracoabdominal and subcostal nerves, and the lumbar plexus (somatic nerves)? What actions do they stimulate in the lowermost trunk and lower limb? | Postsynaptic sympathetic fibers from anterior rami stimulate: - vasomotion (stimulates blood vessels) - **sudomotion **(stimulates sweat glands) - pilomotion (stimulates erector pili) |
What type of nerve fibers are conveyed by the lumbar splanchnic nerves arising from the medial aspect of the lumbar sympathetic trunks? What do these nerves innervate? | - presynaptic sympathetic fibers
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Partial Lumbar Sympathectomy | surgical removal of two or more lumbar sympathetic ganglia by division of their rami communicantes
|
Buerger’s Disease | (thromboangiitis obliterans) | rare disease of the arteries + veins in the arms and legs
STRONGLY CORRELATED TO SMOKING If you cut sympathetic chain, you can’t stop process but can delay the process |
Partial Lumbar Sympathectomy: The surgeon splits the muscles of the anterior abdominal wall and moves the peritoneum medially + anteriorly to expose the medial edge of the psoas major (along which the sympathetic trunk lies). The left trunk is overlapped slightly by the …? The right trunk is covered by the …? | left = aorta right = inferior vena cava |
Partial Lumbar Sympathectomy: Knowing that identification of the sympathetic trunks is not easy, surgeons take great care not to remove inadvertently part of these (3) structures…? | genitofemoral nerve lumbar lymphatics ureter |
lumbar plexus | anterior rami of L1 through L4 nerves
branches of lumbar plexus: - femoral nerve (L2 - L4)* - obturator nerve (L2 - L4)* - lumbosacral trunk (L4, L5)* - ilioinguinal + iliohypogastric nerves (L1) - genitofemoral nerve (L1, L2) - lateral femoral cutaneous nerve (L2, L3) - accessory obturator nerve (L3, L4) |
femoral nerve | (L2 - L4)
- supplies the flexors of the hip + extensors of the knee |
obturator nerve | (L2 - L4)
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lumbosacral trunk | (L4, L5)
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ilioinguinal + iliohypogastric nerves | (L1) - anterior ramus
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genitofemoral nerve | (L1, L2)
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lateral femoral cutaneous nerve | (lateral cutaneous nerve of the thigh) | (L2, L3)
- supplies skin on anterolateral surface of the thigh |
accessory obturator nerve | (L3, L4) - present almost 10% of the time
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The major neurovascular bundle of the inferior trunk includes what structures? (It courses in the midline of the posterior abdominal wall, anterior to the bodies of the lumbar vertebrae) |
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Abdominal Aorta |
ends = L4 vertebra level; bifutcates into right + left common iliac arteries - aortic bifurcation = 2 - 3 cm inferior + left of umbilicus (@ level of iliac crests) |
common iliac arteries | (right + left) |
(follow medial border of the psoas muscles to pelvic brim)
|
internal iliac artery (branch of right/left common iliac arteries) |
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external iliac artery (branch of left/right common iliac arteries) |
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The branches of the descending (thoracic and abdominal) aorta may be described as arising and coursing in _________(#) vascular planes ? They are classified as being or __ and ___________ or _________? |
visceral or parietal; paired or unpaired |
Paired parietal branches of the aorta serve the what structures? (2) | diaphragm posterior abdominal wall |
What unpaired parietal branch may be said to occupy a fourth (posterior) plane because it arises from the posterior aspect of the aorta just proximal to its bifurcation? | median sacral artery |
The median sacral artery could be considered a midline ________________? | continuation of the aorta (in which case its lateral branches, small lumbar arteries, and lateral sacral branches, would be included as part of the paired parietal branches) |
Branches of the Abdominal Aorta: CELIAC ARTERY | Vascular Plane: anterior midline Class: unpaired visceral Distribution: alimentary tract Vertebral Level: T12 |
Branches of the Abdominal Aorta: SUPERIOR MESENTERIC ARTERY | Vascular Plane: anterior midline Class: unpaired visceral Distribution: alimentary tract Vertebral Level: L1 |
Branches of the Abdominal Aorta: INFERIOR MESENTERIC ARTERY | Vascular Plane: anterior midline Class: unpaired visceral Distribution: alimentary tract Vertebral Level: L3 |
Branches of the Abdominal Aorta: SUPRARENAL ARTERY | Vascular Plane: lateral Class: paired visceral Distribution: urogenital + endocrine organs Vertebral Level: LI |
Branches of the Abdominal Aorta: RENAL ARTERY | Vascular Plane: lateral Class: paired visceral Distribution: urogenital + endocrine organs Vertebral Level: LI |
Branches of the Abdominal Aorta: GONADAL (TESTICULAR or OVARIAN) ARTERY | Vascular Plane: lateral Class: paired visceral Distribution: urogenital + endocrine organs Vertebral Level: L2 |
Branches of the Abdominal Aorta: SUBCOSTAL ARTERY | Vascular Plane: posterolateral Class: paired parietal (segmental) Distribution: diaphragm + body wall Vertebral Level: L2 |
Branches of the Abdominal Aorta: INFERIOR PHRENIC ARTERY | Vascular Plane: posterolateral Class: paired parietal (segmental) Distribution: diaphragm + body wall Vertebral Level: T12 |
Branches of the Abdominal Aorta: LUMBAR ARTERY | Vascular Plane: posterolateral Class: paired parietal (segmental) Distribution: diaphragm + body wall Vertebral Level: L1-L4 |
What pathology may cause the pancreas or stomach to transmit pulsations of the aorta that could be mistaken for an abdominal aortic aneurysm? | a tumor of the pancreas or stomach (because the aorta lies posterior to them) |
Deep palpation of the midabdomen can detect an aortic aneurysm, which usually results from …? | a congenital or acquired weakness of the arterial wall |
Pulsations of a large aneurysm can be detected in what area? What can be used to confirm the diagnosis in doubtful cases? | - to the left of the midline (pulsatile mass can be moved easily from side to side)
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Acute rupture of an abdominal aortic aneurysm is associated with severe pain in what areas? What is the mortality rate of aortic aneurysms? | the abdomen or back - 90% |
How can an aortic aneurysm be surgically repaired? |
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How ca you apply pressure to control bleeding in the pelvis or lower limbs (esp. in children and lean persons)? | (anterior abdominal wall is relaxed) - firm pressure on the anterior abdominal wall, over the umbilicus
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What line is helpful to identify the site of aortic bifurcation when examining obese persons in whom the umbilicus is not a reliable surface landmark? | line joining the highest points of the iliac crests (just to the left of the midpoint) |
The veins of the posterior abdominal wall are tributaries of the______________, except for the left testicular or ovarian vein, which enters the _________instead. |
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The IVC, the largest vein in the body, has no valves except for ___________________? | non-functional one at its orifice in the right atrium of the heart |
The IVC returns poorly oxygenated blood from …? | lower limbs most of the back abdominal walls abdominopelvic viscera |
Blood from the abdominal viscera passes through _________________ before entering the IVC through the hepatic veins | portal venous system + liver **(non-portal blood collected from abdomen + pelvis) * |
Where does the IVC begin, ascend, and exit the abdominal cavity? | begins = anterior to L5 vertebra @ union of common iliac veins (inferior to the bifurcation of the aorta and posterior to the proximal part of the right common iliac artery) ascends = right sides of L3 - L5 vertebrae bodies + on right psoas major to right of the aorta exits = thru caval opening in diaphragm; enters thorax at T8 vertebral level |
The tributaries of the IVC correspond to the branches of the abdominal aorta? The tributaries of the portal vein correspond to the ___ branches of the aorta? | IVC = paired visceral + parietal portal vein = unpaired visceral |
The branches of the IVC corresponding to the paired viscera branches of the abdominal aorta include … (4)? |
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Paired parietal branches of the IVC include … (4)? | inferior phrenic veins 3rd (L3) + 4th (L4) lumbar veins common iliac veins (union of external + internal iliac veins) |
Which 2 ascending veins connect the IVC + superior vena cava, either directly or indirectly? | lumbar veins and azygos veins |
What are the 3 collateral routes available for venous blood to return to the heart when the IVC is obstructed or ligated? |
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Why are IVC anomalies relatively common? Where do most of them occur? |
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In the posterior abdomen, where do lymphatic vessels + lymph nodes lie? | along the aorta along IVC along iliac vessels |
Where do the common iliac nodes receive lymph from + where do they drain lymph to? | receive from = external + internal iliac lymph nodes drain to = right + left lumbar lymph nodes |
Efferent vessels from which lymph nodes form the intestinal lymphatic trunks + participate in the confluence of lymphatic trunks that gives rise to the thoracic duct? What structures do these lymph nodes receive lymph from? | celiac, superior + inferior mesenteric nodes receive lymph from:
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The thoracic duct begins with the convergence of what ducts? Where is this located? These form what dialation/structure? |
convergence = the chyle cistern |
Lymphatic drainage from what areas of the body converge in the abdomen to enter the beginning of the thoracic duct? | all lymphatic drainage from lower half of the body
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Thoracic duct ascends through the aortic hiatus in the diaphragm into the posterior mediastinum. It collects more parietal and visceral drainage, particularly from what quadrant? | left upper quadrant of the body |
Where does the thoracic duct end? | ends by entering the venous system at: junction of the left subclavian + internal jugular veins (the left venous angle) |