25 Posterior Abdominal Wall and Abdomen Structure List
POSTERIOR ABDOMINAL WALL AND URINARY SYSTEM
Learning Objectives
By the end of the course students will be able to:
- Demonstrate the relationships of the kidneys and suprarenal glands to adipose and fascial coverings, lower ribs and other abdominal organs
- Describe the basic internal gross anatomy of the kidney.
- Define the blood supply and drainage of the kidneys and suprarenal glands.
- Describe the general organization of the urinary and endocrine systems.
- Identify the diaphragmatic musculature and its fasciae, and its functional significance in respiration.
- Identify the thoracic and lumbar splanchnic nerves and the collateral ganglia or regional subdivisions of the preaortic plexus to which each functionally relates and how visceral referred pain travels along these autonomic nerves.
- Describe the lymphatic drainage of the GI tract and other structures in the abdomen.
- Describe the nerves of the lumbar plexus in terms of their: spatial relationship to the posterior abdominal wall muscles; distribution to the abdominal wall, the genital region, and the lower limb; and categorization into purely cutaneous nerves and those which also innervate muscles.
- Locate the lumbar sympathetic trunk and white and gray rami communicantes; explain the reason for the inferior limit of the white rami.
- Describe the branching pattern of the abdominal aorta and inferior vena cava
Reference: Moore, Clinically oriented Anatomy, chapter 2.
Particularly Relevant Blue Boxes in Moore:
●Accessory Renal Vessels, Congenital Anomalies of the Kidneys and Ureters, p. 299
●Renal and Ureteric Calculi, p. 300.
●Referred Pain From the Diaphragm, p. 317
●Congenital Diaphragmatic Hernia, p. 317.
●Psoas Abscess, p. 318
●Pulsations of the Aorta and Abdominal Aortic Aneurysm, p. 319
To access the Netter Presenter Database click here
Grant’s Dissector, 15th Edition, pp 116 – 124
To access Gray’s Photographic Dissector section on the Posterior Abdominal Wall section click here
To access the Primal Pictures software click here
Check out the Primal Pictures model of the Abdomen and Kidney
Posterior Abdominal Wall and Urinary System
The posterior abdominal wall (Netter 258) consists of the vertical ridge produced by the vertebral bodies and muscles which include:
- the psoas
- the quadratus lumborum
- the transversus abdominis muscle
- the posterior part of the diaphragm and its crura, posteriorly.
The parietal peritoneum covers this posterior abdominal wall along with the retroperitoneal organs such as the duodenum and the kidneys lying on the vertebrae and muscles.
After the mesentery has been cleaned from the posterior abdominal wall, you can see the true retroperitoneal structures of the abdomen (Netter 259, 260, 261, 262) These are the great vessels and their branches, sympathetics, kidneys and their ureters, and suprarenal glands.
You should be able to identify the following structures in your dissection:
- inferior vena cava (IVC)
- testicular (or ovarian)
- aorta
- celiac trunk
- superior mesenteric artery
- inferior mesenteric artery
- external iliac
- internal iliac
- testicular (or ovarian)
- lumbar sympathetic chain
- celiac ganglia
- ureter
- kidney
- suprarenal gland
MUSCLES OF THE POSTERIOR ABDOMINAL WALL (Netter 258)
Psoas major:
· attaches from the transverse processes and sides of the bodies and intervertebral discs of the 5 lumbar vertebrae;
· passes with iliacus (Iliacus arises from the inner surface of ilium)under the inguinal ligament
· attaches to the lesser trochanter fusing with iliacus (iliopsoas).
- innervated by L1, 2 and 3 inside the abdomen.
- flexes the hip joint.
Clinical Correlation: Certain types of tuberculosis which invade the spine can produce an accumulation of pus deep to the psoas major muscle, known as a psoas abscess. Patients with condition will experience pain upon extension of the thigh, known as a positive psoas sign.
Psoas minor is an occasional small muscle belly with its long tendon lying over the psoas major.
Iliopsoas is covered by dense layer of fascia so that muscles and lumbar plexus are behind fascia and iliac vessels are in front of it (The femoral sheath is formed by the transversalis fascia above the inguinal ligament and the iliopsoas fascia below the ligament).
Quadratus lumborum lies lateral to psoas, running between the iliac crest and T12. It is a lateral flexor of the trunk and is innervated segmentally by the adjacent lumbar nerves.
The diaphragm (Netter 258) crosses the quadratus lumborum and the psoas by the lateral and medial lumbocostal arches (arcuate ligaments) It arises from the xiphoid process, lower six costal cartilages, medial and lateral lumbocostal arches, vertebrae L1 – L3 for the right crus and vertebrae l1 – L2 for the left crus. It receives its motor fibers from the phrenic nerve; its central part receives sensory fibers from the phrenic nerve while the peripheral part receives sensory fibers from the intercostal nerves. Its blood supply is from the musculophrenic, pericardiophrenic, superior phrenic and inferior phrenic arteries (Netter 259).
You should be able to identify on the diaphragm:
- right and left domes of the diaphragm
- right crus
- left crus
- medial arcuate ligament arches over the sympathetic trunk as it enters the abdomen and the upper fibers of the psoas muscle.
- lateral arcuate ligament arches over the free tip of the twelfth rib and the subcostal nerve (T12)
- median arcuate ligament arches over the aorta and the cysterna chyli (a lymphatic sac that continues into the thorax as the thoracic duct.
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Note:
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The Transversus abdominis muscle arises from the thoracolumbar fascia (Anterior attachments have been described in the anterior abdominal wall;
Blood Vessels – Abdominal Aorta
The abdominal aorta(Netter 259) lies in the midline It enters the abdomen under the median arcuate ligament at T12 and ends at L4, left of the midline by dividing into the 2 common iliac arteries. The main continuation of the aorta is the median or middle sacral artery
Other branches of the abdominal aorta
1. Ventral branches are the celiac, superior and inferior mesenteric arteries to the fore-, mid- and hindgut respectively.
2. Lateral branches supply the suprarenal glands, kidneys and the gonads
· The largest are the renal arteries, which receive 1/4 of the cardiac output. They arise just below the superior mesenteric artery. The right renal artery passes posterior to the inferior vena cava. They also send branches to the suprarenal glands and the renal pelvis.
● The suprarenal branch of the aorta is also called the middle suprarenal artery.
- The gonadal (ovarian or testicular) arteries arise from the aorta just below the renal arteries. They descend lying anterior to the surface of the psoas to reach the ovary or pass into the inguinal canal to go to the scrotum.
3. Branches to the body wall
· The inferior phrenic arteries: branches to the suprarenal glands and ramify on the inferior surface of the diaphragm.
● The 4 lumbar arteries: gives a posterior branch going through the back and giving a spinal branch. The anterior branch runs in the anterior abdominal wall between the transversus and the internal oblique muscle.
● The median (middle) sacral artery: in the midline, anterior to the sacrum.
Clinical Considerations:
The aortic pulse is palpable through the anterior abdominal wall and often can be observed in lean individuals. Aneurysms of the aorta commonly involve the origins of the aortic branches. A large aneurysm may erode into an adjacent vertebra, with resulting back pain.
Coarctation (occlusion) of the aorta. Stenosis superior to the renal arteries is more likely to be fatal, because the kidneys require far more blood than can flow through collateral vessels. Slow occlusion below the renal arteries results in progressive development of collateral pathways. A major shunt between the internal thoracic artery and the inferior epigastric artery develops, with enlargement of the intercostal and abdominal arteries (giving grise to rib notching). The marginal artery (of Drummond) may hypertrophy when occlusion occurs between the origins of the superior and inferior mesenterid arteries.
Inferior Vena Cava
The INFERIOR VENA CAVA (Netter 260) begins in front of the body L5 and ascends to the diaphragm to pierce the central tendon at T8.
From the renal veins upwards, veins lie anterior to the corresponding arteries. Below the level of the renal veins, the arteries lie anterior to the veins.
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Tributaries of the inferior vena cava may be deduced from branches of the aorta
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Nerves in the Posterior Abdominal Wall (Netter 262; Moore 312)
The nerves of the posterior abdominal wall are branches of the lumbosacral plexus.
On the cadaver, if you cut and reflect the psoas major muscle, you should be able to identify the roots of the plexus:
- L1 – L5
These roots are the ventral primary rami of the spinal nerves:
L1 – gives rise to the iliohypogastric and ilioinguinal nerves.
L1 + L2 – gives rise to the genitofemoral nerve
L2 + L3 – gives rise to the lateral femoral cutaneous
L2 + L3 + L4 – give rise to the femoral and obturator nerves
L4 + L5 – give rise to the lumbosacral trunk which joins sacral nerves to form the sacral plexus.
The subostal nerve (T12) penetrates the transverse abdominal wall muscle to run between it and the internal oblique muscle. It innervates the external oblique, internal oblique, transversus and rectus abdominus mscles
The iliohypogastric nerve (L1) emerges from the lateral border of the psoas major muscle and runs across the quadratus lumborum. It innervates the internal oblique and transverse abdominus muscles and divides into an anterior cutaneous branch which innervates the skin above the pubis and a lateral cutaneous branch which innervates the skin of the gluteal region.
The ilioinguinal nerve (L1) runs across the quadratus lumborum and accompanies the spermatic cord or round ligament of the uterus, continues through the inguinal canal and emerges through the superficial inguinal ring. It innervates the internal oblique and transversus abdominal muscles and gives off femoral cutaneous branches to the upper medial part of the thigh and anterior scrotal or labial branches.
The genitofemoral nerve (L1 , L2) emerges in front of the psoas muscle and descends on its anterior surface. It divides into a genital branch which enters the inguinal canal through the deep inguinal ring to reach the spermatic cord and supply the cremaster muscle, and a femoral branch, which supplies the skin of the femoral triangle.
The lateral femoral cutaneous nerve (L2, L3) emerges from the lateral side of the psoas muscle and runs in front of the iliacus and behind the inguinal ligament. It innervates the skin of the anterior and lateral thigh.
The femoral nerve (L2, L3, L4) emerges from the lateral border of the psoas major and enters the femoral triangle deep to the inguinal ligament. It innervates the quadriceps, iliacus and sartorius muscles and supplies the anterior and medial thigh with sensory innervation.
The obturator nerve (L2, L3, L4) descends along the medial border of psoas and enters the thigh through the obturator foramen. It supplies the adductor muscles and an area of skin on the medial thigh.
The lumbosacral trunk (L4, L5) enters into the formation of the sacral plexus.
Kidneys and Ureters. (Netter 308, 309, 310, 311, 312, 313; Moore 290-300)
- The kidneys lie on the psoas major, quadratus lumborum and the origin of the transversus abdominis from medial to lateral
- Superiorly, the upper part of the kidney lies against the diaphragm posterior to which is the costodiaphragmatic recess of pleura and the lower ribs (12 R; 11 and 12 L). The subcostal, iliohypogastric and ilioinguinal nerves are also posterior relations.
- Kidneys are surrounded by perirenal fat enclosed in renal fascia. The renal capsule lies directly surrounding the kidney
Kidneys
The kidneys develop as and remain retroperitoneal organs. They develop in the pelvis and “ascend” to the level of T12. The right kidney is slightly lower than the left kidney; this is probably due to the presence of the liver on the right side. The left kidney may also be a little longer than the right kidney.
The kidneys with their tough outer capsule are surrounded by fatty areolar tissue which is further enclosed by a surrounding fibrous sheath. This cushion of perinephric fat or fatty capsule allows the kidneys 2-3 cm. of vertical mobility to compensate for the contraction of the diaphragm in breathing. The renal fasciae or perinephric fasciae of the kidneys are interconnected anterior to the vertebral column and posterior to the aorta and inferior vena cava. In fact, this fibrous tissue interconnection is closely adherent to the adventitia of these great vessels.
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The kidneys lie in a paravertebral gutter. Posterior to the kidneys is the transversalic fascia (psoas fascia and quadratus lumborum fascia), the psoas muscle and the quadratus lumborum muscle. Three important nerves lie posterior to the kidney in their initial course to the anterior abdominal wall. The ilio-hypogastric nerve and the ilio-inguinal nerve (both Ll) course along the quadratus lumborum to the anterior abdominal wall. The ilio-hypogastric nerve being lateral to the ilio-inguinal nerve. The genito-femoral nerve (Ll,2) courses through and more medially along the psoas muscle to turn laterally to the anterior abdominal wall. |
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On the posterior abdominal wall the lower lateral borders of the kidneys lie in the lumbar triangle or triangle of Petit. Only the internal oblique and the transversus abdominis muscles lie between the kidney and the exterior wall. The kidneys are anatomically associated with other retroperitoneal structures including the following: the inferior vena cava, the aorta, the pancreas, most of the duodenum, the ascending colon and the descending colon. The root of the transverse mesocolon and the root of the coronary ligament are associated with the kidneys superiorly and anteriorly as they are reflected off the posterior wall and diaphragm respectively. |
The ureters (Netter 314) pass from the kidneys to the bladder. They are about 25 cm. long and have a thick muscular wall. The ureters are divided into three parts: the pelvis, the abdominal ureter, and the pelvic ureter. The pelvis is formed by three (usually) major calyces which are in turn formed by the minor calyces. The abdominal portion of the ureter lies in the extraperitoneal connective tissue.
There are three anatomical constrictions along the ureter, one at the narrowing of the pelvis, one where the abdominal ureter passes over the pelvic brim, and one where the pelvic ureter enters the bladder.
In their descent to the bladder, the ureters pass anterior to the psoas muscle into the pelvis. They pass anterior to the bifurcation of the common iliac artery after turning medially.
The blood supply to the ureters is from the renal arteries, the testicular arteries, and branches from each internal iliac artery.
The blood supply to the kidneys is by way of the renal arteries from the aorta. The right renal artery is longer than the left renal artery because of the position of the aorta to the left of the inferior vena cava and to the left of the midline. The converse is true regarding the renal veins — the right renal vein is shorter than the left. Both renal arteries are posterior to the renal veins and they enter the kidney at the hilus. The renal artery trifurcates prior to entering the kidney, and the ureter exits from the kidney anterior to two of the arteries.
Predominantly autonomic in nature, the kidneys are served by the renal plexus. The ureters are served by the renal, superior and inferior hypogastric plexuses. The bladder is served by the sympathetic lumbar splanchnic nerves (L1, L2) which form the vesical nervous plexus with parasympathetic participation (pelvic and sacral in origin), and which is continuous with the inferior hypogastric plexus. Note that urinary pain (especially renal and ureteric) is often referred to the infero-antero-lateral quadrant (especially the groin area) on the side the pain is occurring. Visceral sensory fibers travel from the kidney and upper part of the ureter with the renal and other arteries and enter spinal cord levels T12 and L1 to give referred pain in these dermatomes.
The bladder is also under control of the autonomic nervous system. When empty, the internal urethral sphincter is contracted, whereas the bladder is relaxed. When the bladder is filled and begins to stretch, the internal sphincter relaxes, whereas the bladder reflexively contracts. With practice this reflex can be suppressed. The external urethral sphincter is voluntarily innervated by the pudendal nerve.
A cross section showing the kidneys and other posterior abdominal wall structures can be viewed by clicking here
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The Adrenal Glands (Netter 310; Moore 294) The adrenal glands or suprarenal glands lie on the supero-medial surface of the kidney. The adrenal gland is an endocrine gland. The cortex is responsible for the production of steroids which control body essential for life. The adrenal medulla is source of epinephrine (derived from neural crest cells) which circulates in the blood. Both adrenal glands are embedded in perinephric fat. They are separated from the kidney by a thin layer of fibrous connective tissue contributed by the perinephric fascia which surrounds both the kidney and the adrenal gland. |
The right adrenal gland is triangular in shape. The diaphragm lies posterior to the gland, inferior vena cava contacts the anterior surface but lies medially, and the liver contacts the anterior surface but lies laterally. The left adrenal gland is crescent shaped and descends to the hilus of the left kidney. It contacts the left crus of the diaphragm posteriorly. The anterior surface of the stomach, and inferiorly contacts the pancreas. The celiac trunk and celiac plexus lie between the two medial aspects of the adrenal glands.
The adrenal glands, being endocrine glands, are highly vascular. Their blood supply is from the inferior phrenic artery which arises from the inferior phrenic artery which arises from the abdominal aorta and gives off 6-8 superior adrenal branches, the abdominal aorta gives off the middle adrenal branch, and the renal artery gives off the inferior adrenal artery. In contrast to the numerous arterial branches, there is only one large venous branch leaving each adrenal gland at the hilus. The left adrenal vein enters the left renal vein, the right adrenal vein enters the inferior vena cava. Innervation of the chromaffin cells in the adrenal medulla is from the greater splanchnic nerve – unlike other splanchnic nerves which synapse in preaortic ganglia, thepreganglionic fibers of these splanchnic nerves synapse directly on the chromaffin cells, causing them to secrete norepinephrine and epinephrine.
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Clinical Correlations The kidneys “ascend” to their abdominal position from the pelvis during development. As the kidneys ascend, their blood supply changes; it comes from progressively higher and higher arteries. Consequently, it is not uncommon for the kidneys to have a double blood supply, where the lower artery has not degenerated (Netter 310). This is not pathologic unless the lower artery constricts the ureter. A kidney that fails to ascend to the abdomen from the pelvis is known as a “Pelvic Kidney“. An ectopic kidney is a kidney which has migrated to an abnormal position. A “horseshoe kidney“ is a condition which arises when the primordial kidneys fuse. Usually the fusion occurs at the inferior poles and a large, curved kidney – which resembles a horseshoe, develops. It is usually prevented from ascending into the abdomen by the presence of the mid-line inferior mesenteric artery. Surgical access to the kidney is frequently through the lumbar triangle (of Petit) where fewer muscle layers are encountered. The ureters (Netter 310, 311, 314) may also occasionally be double or two ureters may leave the kidney and fuse inferiorly to form a “Y”-shaped ureter. Damage to the ureters is primarily through surgery. Otherwise, they are well protected. A passing of a kidney stone may elicit excrutiating pain as the stone migrates along the ureter. Afferents (Netter 344) from the kidney enter at T12. Thus, passage of a kidney stone will sometimes give rise to referred pain from the testis (testicular plexus of nerves at T10). Obstruction of the ureter occurs by renal calculi (Kidney stones) (Netter 310a) where the ureter joins the renal pelvis, where it crosses the pelvic brim, or where it enters the wall of the urinary bladder. Kidney stones at these narrow points result in hydroureter and hydronephrosis. Hydronephrosis is a fluid-filled enlargement of the renal pelvis and calyces as a result of obstruction of the ureter. It has symptoms of nausea and vomiting, urinary tract infection, fever, dysuria (painful or difficult urination), urinary frequency and urgency. A pheochromocytoma is a tumor of the adrenal medulla. Excessive or life-threatening bursts of epinephrine and norepinephrine, which result in paroxysms of hypertensiion, may be released from these tumors on sympathetic activation or even abdominal palpation. |
Adrenalectomy. The suprarenal vein must be ligated before manipulation of the adrenal gland do that catecholamines do not escape into the circulation. The right adrenal gland is more difficult to approach surgically than the left adrenal gland because it is in part posterior to the inferior vena cava.
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Lymphatics of the Posterior Abdominal Wall (Netter 261; 316) There are two groups of lymph nodes in the posterior abdominal wall – pre-aortic nodes and para-aortic nodes The preaortic lymph nodes lie in front of the aorta, and may be divided into celiac lymph nodes, superior mesenteric lymph nodes, and inferior mesenteric lymph nodes groups, arranged around the origins of the corresponding arteries which supply these parts of the gastrointestinal system. The majority unite to form the intestinal trunk, which enters the cisterna chyli, a dilated sac marking the inferior end of the thoracic duct. The paraaortic lymph nodes (also known as lateral aortic nodes) are a group of lymph nodes that lie in front of the lumbar vertebral bodies near the aorta. These lymph nodes receive drainage from the posterior abdominal wall, kidneys, adrenal glands and the pelvic organs and lower limbs. The thoracic duct is the largest lymphatic vessel in the body. It collects most of the lymph in the body (except that from the right arm and the right side of the chest, neck and head, and lower left lobe of the lung, which is collected by the right lymphatic duct) and drains into the systemic (blood) circulation at the left brachiocephalic vein, right between where the left subclavian vein and left internal jugular connect. In adults, the thoracic duct is typically 38-45 cm in length and an average diameter of a few mm. It usually starts from the level of the second lumbar vertebra and extends to the root of the neck. It originates in the abdomen from the confluence of the right and left lumbar trunk and the intestinal trunk, forming a significant pathway upward called the cisterna chyli (Brownie points if you can find this structure in the posterior abdomen). The thoracic duct extends vertically in the chest and curves posteriorly to the left carotid artery and left internal jugular vein at the C7 vertebral level to empty into the junction of the left subclavian vein and left jugular vein It traverses the diaphragm at the aortic aperture and ascends the posterior mediastinum between the descending thoracic aorta (to its left) and the azygos vein (to its right). |
Posterior Abdominal Wall quiz click here
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ABDOMEN STRUCTURE LIST
Anterior Abdominal Wall
Fascia
Camper’s fascia
Scarpa’s fascia
Muscles
External Oblique
Internal Oblique
Transversus Abdominus
Rectus Abdominus
Inguinal Region/Peritoneum
Inguinal ligament
External/internal inguinal ring, inguinal canal
Median, medial lateral unbilical folds
Mesenteries
Greater omentum
Lesser omentum – gastrohepatic ligament, hepatoduodenal ligament
gastrolienal ligament, lienorenal ligament
Lesser sac, epiploic foramen of Winslow
Mesentery of small intestine
Foregut Structures
Stomach
Greater and lesser curvatures
Cardia
Fundus
Body
Pylorus – antrum, sphincter
Liver
Right and left lobes
Quadrate lobe
Caudate lobe
Coronary ligament
Bare area
Right and left triangular ligaments
Porta hepatis
Portal vein
Common hepatic duct
Proper hepatic artery
Ligamentum venosum
Hepatic veins
Inferior vena cava
Gall Bladder
Body, neck, cystic duct
Pancreas
Head, neck, body, tail
Uncinate process
Main pancreatic duct (Duct of Wirsung)
Accessory pancreatic duct (of Santorini)
Duodenum
First, second, third and fourth parts
Hepatopancreatic ampulla, Sphincter of Oddi
Branches of Celiac trunk
Left gastric
Esophageal branch
Splenic
Left gastroepiploic
Short gastric
Common hepatic
Right gastric
Gastroduodenal
Right gastroepiploic
Superior pancreaticoduodenal
Proper hepatic
Right hepatic
Cystic
Left hepatic
Midgut Structures
Jejunum
Ileum
Large Intestine
Cecum
Vermiform appendix
Ascending colon
Transverse colon
Iliocecal junction
Hepatic (right) colic flexure
Taenia coli
Haustra
Epiploic appendages
Superior mesenteric artery
Inferior pancreaticoduodenal
Vasa recta
Jejunoileal branches
Arterial arcades
Vasa recta, Ileocolic, right colic, middle colic
Hindgut Structures
Splenic flexure of colon
Descending colon
Sigmoid colon
Upper 1/3rd of rectum
Diverticulae
Inferior mesenteric artery (artery of hindgut)
Left colic
Ascending and descending branches
Sigmoid branches
Superior rectal
Marginal Artery of Drummond
Diaphragm
Openings: Caval orifice (T8)
Esophageal sphincter (T10)
Aortic orifice (T12)
Left and right crura
Medial and lateral lumbocostal (arcuate) arches
Muscles of Posterior Wall
Psoas major
Iliacus
Psoas minor
Quadratus lumborum
Transverse abdominus
Abdominal aorta
Left and right common iliac a.s
Median sacral a.
Inferior phrenic a.s
Lumbar a.s
Renal a.s
Gonadal a.s
Middle suprarenal a.s
Celiac trunk
Superior mesenteric a.
Inferior mesenteric a.
Inferior Vena Cava
Hepatic veins
Left renal vein
Nerves
Sympathetic trunks
Pelvic splanchnic nerves
Subcostal n.
Lumbar Plexus
Ilioinguinal, iliohypogastric n.s
Lateral femoral cutaneous n.
Femoral n.
Genitofemoral n.
Obturator n.
Lumbosacral trunk
Lymph Nodes
preaortic (celiac, superior mesenteric, inferior mesenteric nodes)
lateral aortic (para-aortic) nodes
Kidneys
Hilum
Renal a.s/v.s
Renal medulla (pyramids)
Renal cortex
Renal pelvis
Major, minor calices
Adrenal Glands
Cortex, medulla
Superior, middle and inferior suprarenal a.s/v.s