Introduction

Posteriorabdominal wallAbdominal wallThe outer margins of the abdomen, extending from the osteocartilaginous thoracic cage to the pelvis. Though its major part is muscular, the abdominal wall consists of at least seven layers: the skin, subcutaneous fat, deep fascia; abdominal muscles, transversalis fascia, extraperitoneal fat, and the parietal peritoneum.Surgical Anatomy of the Abdomen

• Complex musculoskeletal structure representing the posterior boundary of the abdominal cavity
• SupportsretroperitonealRetroperitonealPeritoneum: Anatomy organs and contains important neurovascular structures
• Boundaries:
  • Anteriorly by:
    • Anterolateral abdominal muscles
    • RetroperitonealRetroperitonealPeritoneum: Anatomy organs
    • ParietalParietalOne of a pair of irregularly shaped quadrilateral bones situated between the frontal bone and occipital bone, which together form the sides of the cranium.Skull: AnatomyperitoneumPeritoneumThe peritoneum is a serous membrane lining the abdominopelvic cavity. This lining is formed by connective tissue and originates from the mesoderm. The membrane lines both the abdominal walls (as parietal peritoneum) and all of the visceral organs (as visceral peritoneum).Peritoneum: Anatomy
  • Posteriorly by:
    • Lumbar vertebraeLumbar vertebraeVertebrae in the region of the lower back below the thoracic vertebrae and above the sacral vertebrae.Vertebral Column: Anatomy
    • Muscles
    • FasciaFasciaLayers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs.Cellulitis 
  • Superiorly by the 12th rib anddiaphragmDiaphragmThe diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force.Diaphragm: Anatomy 
  • Inferiorly by the pelvic brim

Structures

• FasciaFasciaLayers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs.Cellulitis
• Muscles
  • DiaphragmDiaphragmThe diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force.Diaphragm: Anatomy
  • Psoas major and minor
  • Iliacus muscle
  • Quadratus lumborum
• Extraperitoneal fat
• ParietalParietalOne of a pair of irregularly shaped quadrilateral bones situated between the frontal bone and occipital bone, which together form the sides of the cranium.Skull: AnatomyperitoneumPeritoneumThe peritoneum is a serous membrane lining the abdominopelvic cavity. This lining is formed by connective tissue and originates from the mesoderm. The membrane lines both the abdominal walls (as parietal peritoneum) and all of the visceral organs (as visceral peritoneum).Peritoneum: Anatomy
• Vasculature
  • AbdominalaortaAortaThe main trunk of the systemic arteries.Mediastinum and Great Vessels: Anatomy
  • Inferior vena cavaInferior vena cavaThe venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs.Mediastinum and Great Vessels: Anatomy 
• Somatic innervation: subcostal nerve and lumbar plexus

Fascia and Related Structures of the Posterior Abdominal Wall

ThoracolumbarfasciaFasciaLayers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs.Cellulitis

Large area ofconnective tissueConnective tissueConnective tissues originate from embryonic mesenchyme and are present throughout the body except inside the brain and spinal cord. The main function of connective tissues is to provide structural support to organs. Connective tissues consist of cells and an extracellular matrix.Connective Tissue: Histology that is made up of 3 layers:

• Posterior:
  • Extends from the 12th rib to the iliac crest
  • Laterally goes to theinternal obliqueInternal obliqueMuscles of the anterolateral abdominal wall consisting of the external oblique and the internal oblique muscles. The external abdominal oblique muscle fibers extend from lower thoracic ribs to the linea alba and the iliac crest. The internal abdominal oblique extend superomedially beneath the external oblique muscles.Anterior Abdominal Wall: Anatomy andtransversus abdominisTransversus abdominisAnterior Abdominal Wall: Anatomy muscles
  • Overlies the latissimus dorsi muscle
• Middle:
  • Together with the anterior layer, encloses the quadratus lumborum muscle
  • Together with the posterior layer, encloses the deepmuscles of the backMuscles of the backThe back is composed of several muscles of varying sizes and functions, which are grouped into intrinsic (or primary) back muscles and extrinsic (or secondary) back muscles. The extrinsic muscles comprise the superficial and intermediate muscle groups, while the intrinsic muscles comprise the deep muscles.Muscles of the Back: Anatomy
• Anterior:
  • Attached to the iliac crest, anterior part of the transverse processes oflumbar vertebraeLumbar vertebraeVertebrae in the region of the lower back below the thoracic vertebrae and above the sacral vertebrae.Vertebral Column: Anatomy, and 12th rib
  • Thickens on the superior aspect to form the lateral arcuate ligament
  • Laterally, continues with the aponeurosis of thetransversus abdominisTransversus abdominisAnterior Abdominal Wall: Anatomy muscle

PsoasfasciaFasciaLayers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs.Cellulitis

• Covers the psoas major muscle 
• Thickened superiorly, forming medial arcuate ligament
• Medially adheres to thelumbar vertebraeLumbar vertebraeVertebrae in the region of the lower back below the thoracic vertebrae and above the sacral vertebrae.Vertebral Column: Anatomy and pelvic brim
• Continues with part of the iliacfasciaFasciaLayers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs.Cellulitis inferiorly and the thoracolumbarfasciaFasciaLayers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs.Cellulitis laterally

Lumbar triangles

Similarly to the anteriorabdominal wallAbdominal wallThe outer margins of the abdomen, extending from the osteocartilaginous thoracic cage to the pelvis. Though its major part is muscular, the abdominal wall consists of at least seven layers: the skin, subcutaneous fat, deep fascia; abdominal muscles, transversalis fascia, extraperitoneal fat, and the parietal peritoneum.Surgical Anatomy of the Abdomen,herniationHerniationOmphalocele can occur in weakened areas in the posteriorabdominal wallAbdominal wallThe outer margins of the abdomen, extending from the osteocartilaginous thoracic cage to the pelvis. Though its major part is muscular, the abdominal wall consists of at least seven layers: the skin, subcutaneous fat, deep fascia; abdominal muscles, transversalis fascia, extraperitoneal fat, and the parietal peritoneum.Surgical Anatomy of the Abdomen. These herniations occur in the Grynfeltt-Lesshaft triangle (superior lumbar triangle) or Petit triangle (inferior lumbar triangle).

• Inferior lumbar (Petit) triangle:
  • Lies superficially 
  • Sometimes called the lumbar triangle
  • Bound by:
    • External obliqueExternal obliqueMuscles of the anterolateral abdominal wall consisting of the external oblique and the internal oblique muscles. The external abdominal oblique muscle fibers extend from lower thoracic ribs to the linea alba and the iliac crest. The internal abdominal oblique extend superomedially beneath the external oblique muscles.Anterior Abdominal Wall: Anatomy muscle anteriorly
    • Latissimus dorsi muscle posteriorly
    • Iliac crest inferiorly
• Superior lumbar (Grynfeltt-Lesshaft) triangle:
  • Deep; size varies per individual.
  • More commonly the site ofherniationHerniationOmphalocele
  • Bound by:
    • Quadratus lumborum medially
    • Internal obliqueInternal obliqueMuscles of the anterolateral abdominal wall consisting of the external oblique and the internal oblique muscles. The external abdominal oblique muscle fibers extend from lower thoracic ribs to the linea alba and the iliac crest. The internal abdominal oblique extend superomedially beneath the external oblique muscles.Anterior Abdominal Wall: Anatomy muscle laterally
    • 12th rib superiorly
    • TransversalisfasciaFasciaLayers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs.Cellulitis as the floor of the triangle
    • External abdominal oblique as the roof of the triangle

Muscles and Bones

Muscles

• DiaphragmDiaphragmThe diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force.Diaphragm: Anatomy:
  • Forms superior border of the posterior abdominal region
  • Consists of 3 parts:
    • Sternal 
    • Costal 
    • Lumbar
  • Contains 3 important apertures:
    • Caval opening (T8)
    • Esophageal hiatusEsophageal hiatusDiaphragm: Anatomy (T10)
    • Aortic hiatusAortic hiatusDiaphragm: Anatomy (T12)
  • Origin:
    • Xiphoid processXiphoid processChest Wall: Anatomy
    • RibsRibsA set of twelve curved bones which connect to the vertebral column posteriorly, and terminate anteriorly as costal cartilage. Together, they form a protective cage around the internal thoracic organs.Chest Wall: Anatomy 7–12
    • Upperlumbar vertebraeLumbar vertebraeVertebrae in the region of the lower back below the thoracic vertebrae and above the sacral vertebrae.Vertebral Column: Anatomy
  • Insertion: the middle part of thecentral tendonCentral tendonDiaphragm: Anatomy
  • Functions:
    • Major muscle ofrespirationRespirationThe act of breathing with the lungs, consisting of inhalation, or the taking into the lungs of the ambient air, and of exhalation, or the expelling of the modified air which contains more carbon dioxide than the air taken in.Nose Anatomy (External & Internal), helping in inhalation (contraction) andexpirationExpirationVentilation: Mechanics of Breathing (relaxation)
    • Abdominal straining (increasing intraabdominal pressure)
    • Separates the abdominal cavity from the thoracic cavity 
  • MotorMotorNeurons which send impulses peripherally to activate muscles or secretory cells.Nervous System: Histology innervation: right and left phrenic nerves (originate from cervicalspinal cordSpinal cordThe spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons).Spinal Cord: Anatomy: C3–C5)
  • SensorySensoryNeurons which conduct nerve impulses to the central nervous system.Nervous System: Histology innervation:
    • Phrenic nervePhrenic nerveThe motor nerve of the diaphragm. The phrenic nerve fibers originate in the cervical spinal column (mostly C4) and travel through the cervical plexus to the diaphragm.Diaphragm: Anatomy: for central part ofdiaphragmDiaphragmThe diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force.Diaphragm: Anatomy
    • 6th–11th intercostal nerves for periphery ofdiaphragmDiaphragmThe diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force.Diaphragm: Anatomy
• Quadratus lumborum:
  • Posterior to thekidneysKidneysThe kidneys are a pair of bean-shaped organs located retroperitoneally against the posterior wall of the abdomen on either side of the spine. As part of the urinary tract, the kidneys are responsible for blood filtration and excretion of water-soluble waste in the urine.Kidneys: Anatomy, lateral to psoas muscles
  • Origin: posterior border of the iliac crest
  • Insertion: L1–L4 vertebrae and inferior border of 12th rib
  • Functions:
    • Laterally flexes thelumbar vertebraeLumbar vertebraeVertebrae in the region of the lower back below the thoracic vertebrae and above the sacral vertebrae.Vertebral Column: Anatomy
    • Stabilizes the 12th rib duringrespirationRespirationThe act of breathing with the lungs, consisting of inhalation, or the taking into the lungs of the ambient air, and of exhalation, or the expelling of the modified air which contains more carbon dioxide than the air taken in.Nose Anatomy (External & Internal)
  • Innervation: subcostal (T12) and lumbar (L1–L4) nerves
• Psoas:
  • Major
    • Origin: T12–L4 vertebrae 
    • Insertion: lesser trochanter of femur
    • Function: hipflexionFlexionExamination of the Upper Limbs, lateralflexionFlexionExamination of the Upper Limbs of the trunk
    • Innervation: lumbar plexus (ventral rami of L1–L3)
  • Minor
    • Origin: T12 and L1 vertebrae
    • Insertion: attaches to the pectineal line on the superior pubic ramus
    • Function: weak flexor of the trunk
    • Innervation: ventral rami of L1–L3
• Iliacus:
  • Origin: iliac fossa
  • Insertion: lesser trochanter of the femur 
  • Function: flexesthighThighThe thigh is the region of the lower limb found between the hip and the knee joint. There is a single bone in the thigh called the femur, which is surrounded by large muscles grouped into 3 fascial compartments.Thigh: Anatomy at thehip jointHip jointThe hip joint is a ball-and-socket joint formed by the head of the femur and the acetabulum of the pelvis. The hip joint is the most stable joint in the body and is supported by a very strong capsule and several ligaments, allowing the joint to sustain forces that can be multiple times the total body weight.Hip Joint: Anatomy 
  • Innervation: ventral rami of L2–L4 (femoral nerveFemoral NerveA nerve originating in the lumbar spinal cord (usually L2 to L4) and traveling through the lumbar plexus to provide motor innervation to extensors of the thigh and sensory innervation to parts of the thigh, lower leg, and foot, and to the hip and knee joints.Femoral Region and Hernias: Anatomy)

Support of the posteriorabdominal wallAbdominal wallThe outer margins of the abdomen, extending from the osteocartilaginous thoracic cage to the pelvis. Though its major part is muscular, the abdominal wall consists of at least seven layers: the skin, subcutaneous fat, deep fascia; abdominal muscles, transversalis fascia, extraperitoneal fat, and the parietal peritoneum.Surgical Anatomy of the Abdomen

• 12th thoracic rib
• Vertebral columnVertebral columnThe human spine, or vertebral column, is the most important anatomical and functional axis of the human body. It consists of 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae and is limited cranially by the skull and caudally by the sacrum.Vertebral Column: Anatomy:
  • 12ththoracic vertebraeThoracic vertebraeA group of twelve vertebrae connected to the ribs that support the upper trunk region.Vertebral Column: Anatomy
  • Lumbar vertebraeLumbar vertebraeVertebrae in the region of the lower back below the thoracic vertebrae and above the sacral vertebrae.Vertebral Column: Anatomy (L1–L5)
  • SacrumSacrumFive fused vertebrae forming a triangle-shaped structure at the back of the pelvis. It articulates superiorly with the lumbar vertebrae, inferiorly with the coccyx, and anteriorly with the ilium of the pelvis. The sacrum strengthens and stabilizes the pelvis.Vertebral Column: Anatomy
• Ilium:
  • Largest of the 3 bones that merge to form thehip boneHip boneBones that constitute each half of the pelvic girdle in vertebrates, formed by fusion of the ilium; ischium; and pubic bone.Pelvis: Anatomy
  • The iliac crest (the curved superior border of the ilium) forms the inferior boundary of the posteriorabdominal wallAbdominal wallThe outer margins of the abdomen, extending from the osteocartilaginous thoracic cage to the pelvis. Though its major part is muscular, the abdominal wall consists of at least seven layers: the skin, subcutaneous fat, deep fascia; abdominal muscles, transversalis fascia, extraperitoneal fat, and the parietal peritoneum.Surgical Anatomy of the Abdomen.

Vasculature and Lymphatic Drainage

AbdominalaortaAortaThe main trunk of the systemic arteries.Mediastinum and Great Vessels: Anatomy

• Relation:
  • Continuation of the thoracicaortaAortaThe main trunk of the systemic arteries.Mediastinum and Great Vessels: Anatomy
  • Enters the abdomen through theaortic hiatusAortic hiatusDiaphragm: Anatomy in thediaphragmDiaphragmThe diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force.Diaphragm: Anatomy at the level of the T12 vertebra
  • Travels down the posterior wall of the abdomen (anterior to thevertebral columnVertebral columnThe human spine, or vertebral column, is the most important anatomical and functional axis of the human body. It consists of 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae and is limited cranially by the skull and caudally by the sacrum.Vertebral Column: Anatomy)
  • Divides into the common iliacarteriesArteriesArteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles.Arteries: Histology at L4
• DifferentarteriesArteriesArteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles.Arteries: Histology branch out from the anterior, lateral, and posterior parts of the abdominalaortaAortaThe main trunk of the systemic arteries.Mediastinum and Great Vessels: Anatomy:
  • Unpaired branches:
    • Celiac trunk
    • Superior mesenteric arterySuperior mesenteric arteryA large vessel supplying the whole length of the small intestine except the superior part of the duodenum. It also supplies the cecum and the ascending part of the colon and about half the transverse part of the colon. It arises from the anterior surface of the aorta below the celiac artery at the level of the first lumbar vertebra.Small Intestine: Anatomy
    • Inferior mesenteric arteryInferior mesenteric arteryThe artery supplying nearly all the left half of the transverse colon, the whole of the descending colon, the sigmoid colon, and the greater part of the rectum. It is smaller than the superior mesenteric artery and arises from the aorta above its bifurcation into the common iliac arteries.Small Intestine: Anatomy
    • Median sacral artery
  • Paired branches:
    • Middle adrenal/suprarenalarteriesArteriesArteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles.Arteries: Histology
    • RenalarteriesArteriesArteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles.Arteries: Histology
    • GonadalarteriesArteriesArteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles.Arteries: Histology
    • Inferior phrenicarteriesArteriesArteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles.Arteries: Histology
    • LumbararteriesArteriesArteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles.Arteries: Histology
    • Common iliacarteriesArteriesArteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles.Arteries: Histology (aortaAortaThe main trunk of the systemic arteries.Mediastinum and Great Vessels: Anatomy bifurcates)

Inferior vena cavaInferior vena cavaThe venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs.Mediastinum and Great Vessels: Anatomy

• Relations:
  • Formed at the L5 level by the 2 common iliacveinsVeinsVeins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia.Veins: Histology
  • Ascends to the right of theaortaAortaThe main trunk of the systemic arteries.Mediastinum and Great Vessels: Anatomy
  • Goes through thediaphragmDiaphragmThe diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force.Diaphragm: Anatomy at the T8 level
• Tributaries:
  • HepaticveinsVeinsVeins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia.Veins: Histology
  • Inferior phrenicveinsVeinsVeins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia.Veins: Histology
  • Right suprarenal vein
  • Right gonadal vein
  • RenalveinsVeinsVeins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia.Veins: Histology: The left gonadal, inferior phrenic and suprarenalveinsVeinsVeins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia.Veins: Histology enter the leftrenal veinRenal veinShort thick veins which return blood from the kidneys to the vena cava.Glomerular Filtration, which then drains into theinferior vena cavaInferior vena cavaThe venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs.Mediastinum and Great Vessels: Anatomy.
  • LumbarveinsVeinsVeins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia.Veins: Histology

Lymphatic drainage

• Mostlymph nodesLymph NodesThey are oval or bean shaped bodies (1 – 30 mm in diameter) located along the lymphatic system.Lymphatic Drainage System: Anatomy are located beside the vascularchannelsChannelsThe Cell: Cell Membrane running along the posteriorabdominal wallAbdominal wallThe outer margins of the abdomen, extending from the osteocartilaginous thoracic cage to the pelvis. Though its major part is muscular, the abdominal wall consists of at least seven layers: the skin, subcutaneous fat, deep fascia; abdominal muscles, transversalis fascia, extraperitoneal fat, and the parietal peritoneum.Surgical Anatomy of the Abdomen.
• Lymphatic drainage:
  • GI tract: superior and inferior mesentericlymph nodesLymph NodesThey are oval or bean shaped bodies (1 – 30 mm in diameter) located along the lymphatic system.Lymphatic Drainage System: Anatomy
  • Adrenal glandsAdrenal GlandsThe adrenal glands are a pair of retroperitoneal endocrine glands located above the kidneys. The outer parenchyma is called the adrenal cortex and has 3 distinct zones, each with its own secretory products. Beneath the cortex lies the adrenal medulla, which secretes catecholamines involved in the fight-or-flight response.Adrenal Glands: Anatomy and retroperitoneum: lumbar or para-aorticlymph nodesLymph NodesThey are oval or bean shaped bodies (1 – 30 mm in diameter) located along the lymphatic system.Lymphatic Drainage System: Anatomy
  • Urinary tractUrinary tractThe urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra.Urinary Tract: Anatomy: iliac and lumbarlymph nodesLymph NodesThey are oval or bean shaped bodies (1 – 30 mm in diameter) located along the lymphatic system.Lymphatic Drainage System: Anatomy
  • GonadsGonadsThe gamete-producing glands, ovary or testis.Hormones: Overview and Types/reproductive tract: lumbar, iliac inguinallymph nodesLymph NodesThey are oval or bean shaped bodies (1 – 30 mm in diameter) located along the lymphatic system.Lymphatic Drainage System: Anatomy
• All drain the abdominal viscera into the cisterna chyli through the right and left lumbar and intestinal trunks.

Innervation

Somatic innervation comes from the ventral rami of the subcostal and lumbarspinal nervesSpinal nervesThe 31 paired peripheral nerves formed by the union of the dorsal and ventral spinal roots from each spinal cord segment. The spinal nerve plexuses and the spinal roots are also included.Spinal Cord: Anatomy. 

• Subcostal nerve:
  • From the ventral ramus of T12
  • MotorMotorNeurons which send impulses peripherally to activate muscles or secretory cells.Nervous System: Histology supply to theabdominal wallAbdominal wallThe outer margins of the abdomen, extending from the osteocartilaginous thoracic cage to the pelvis. Though its major part is muscular, the abdominal wall consists of at least seven layers: the skin, subcutaneous fat, deep fascia; abdominal muscles, transversalis fascia, extraperitoneal fat, and the parietal peritoneum.Surgical Anatomy of the Abdomen muscles (external obliqueExternal obliqueMuscles of the anterolateral abdominal wall consisting of the external oblique and the internal oblique muscles. The external abdominal oblique muscle fibers extend from lower thoracic ribs to the linea alba and the iliac crest. The internal abdominal oblique extend superomedially beneath the external oblique muscles.Anterior Abdominal Wall: Anatomy,internal obliqueInternal obliqueMuscles of the anterolateral abdominal wall consisting of the external oblique and the internal oblique muscles. The external abdominal oblique muscle fibers extend from lower thoracic ribs to the linea alba and the iliac crest. The internal abdominal oblique extend superomedially beneath the external oblique muscles.Anterior Abdominal Wall: Anatomy, transverse abdominis, andrectus abdominisRectus AbdominisA long flat muscle that extends along the whole length of both sides of the abdomen. It flexes the vertebral column, particularly the lumbar portion; it also tenses the anterior abdominal wall and assists in compressing the abdominal contents. It is frequently the site of hematomas. In reconstructive surgery it is often used for the creation of myocutaneous flaps.Anterior Abdominal Wall: Anatomy)
  • SensorySensoryNeurons which conduct nerve impulses to the central nervous system.Nervous System: Histology innervation to the T12dermatomeDermatomeSpinal Disk Herniation (anterolateral region)
• Lumbar plexus:
  • Iliohypogastric nerve:
    • Origin: ventral rami of L1spinal nervesSpinal nervesThe 31 paired peripheral nerves formed by the union of the dorsal and ventral spinal roots from each spinal cord segment. The spinal nerve plexuses and the spinal roots are also included.Spinal Cord: Anatomy
    • MotorMotorNeurons which send impulses peripherally to activate muscles or secretory cells.Nervous System: Histology innervation: supplies theinternal obliqueInternal obliqueMuscles of the anterolateral abdominal wall consisting of the external oblique and the internal oblique muscles. The external abdominal oblique muscle fibers extend from lower thoracic ribs to the linea alba and the iliac crest. The internal abdominal oblique extend superomedially beneath the external oblique muscles.Anterior Abdominal Wall: Anatomy andtransversus abdominisTransversus abdominisAnterior Abdominal Wall: Anatomy muscles
    • SensorySensoryNeurons which conduct nerve impulses to the central nervous system.Nervous System: Histology innervation: hypogastric region
  • Ilioinguinal nerveIlioinguinal nerveInguinal Canal: Anatomy and Hernias:
    • Origin: ventral rami of L1
    • MotorMotorNeurons which send impulses peripherally to activate muscles or secretory cells.Nervous System: Histology innervation:internal obliqueInternal obliqueMuscles of the anterolateral abdominal wall consisting of the external oblique and the internal oblique muscles. The external abdominal oblique muscle fibers extend from lower thoracic ribs to the linea alba and the iliac crest. The internal abdominal oblique extend superomedially beneath the external oblique muscles.Anterior Abdominal Wall: Anatomy andtransversus abdominisTransversus abdominisAnterior Abdominal Wall: Anatomy muscles along with the iliohypogastric nerve
    • SensorySensoryNeurons which conduct nerve impulses to the central nervous system.Nervous System: Histology innervation: superomedial aspect of thethighThighThe thigh is the region of the lower limb found between the hip and the knee joint. There is a single bone in the thigh called the femur, which is surrounded by large muscles grouped into 3 fascial compartments.Thigh: Anatomy and anterior surface of the external genitalia
  • Genitofemoral nerveGenitofemoral nerveInguinal Canal: Anatomy and Hernias:
    • Origin: ventral rami of L1–L2spinal nervesSpinal nervesThe 31 paired peripheral nerves formed by the union of the dorsal and ventral spinal roots from each spinal cord segment. The spinal nerve plexuses and the spinal roots are also included.Spinal Cord: Anatomy 
    • Genital branch: thecremaster muscleCremaster muscleTesticles: Anatomy (male),skinSkinThe skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue.Skin: Structure and Functions ofmons pubisMons pubisVagina, Vulva, and Pelvic Floor: Anatomy andlabia majoraLabia majoraVagina, Vulva, and Pelvic Floor: Anatomy (female)
    • Femoral branch:sensorySensoryNeurons which conduct nerve impulses to the central nervous system.Nervous System: Histology innervation of thefemoral triangleFemoral triangleFemoral Region and Hernias: Anatomy
    •  BothsensorySensoryNeurons which conduct nerve impulses to the central nervous system.Nervous System: Histology andmotorMotorNeurons which send impulses peripherally to activate muscles or secretory cells.Nervous System: Histology parts of thecremasteric reflexCremasteric ReflexMale Genitourinary Examination
  • Femoral nerveFemoral NerveA nerve originating in the lumbar spinal cord (usually L2 to L4) and traveling through the lumbar plexus to provide motor innervation to extensors of the thigh and sensory innervation to parts of the thigh, lower leg, and foot, and to the hip and knee joints.Femoral Region and Hernias: Anatomy:
    • Origin: L2–L4spinal nervesSpinal nervesThe 31 paired peripheral nerves formed by the union of the dorsal and ventral spinal roots from each spinal cord segment. The spinal nerve plexuses and the spinal roots are also included.Spinal Cord: Anatomy
    • MotorMotorNeurons which send impulses peripherally to activate muscles or secretory cells.Nervous System: Histology innervation:pectineusPectineusThigh: Anatomy,sartoriusSartoriusThigh: Anatomy,rectus femorisRectus femorisThigh: Anatomy,vastus lateralisVastus lateralisThigh: Anatomy,vastus medialisVastus medialisThigh: Anatomy, andvastus intermediusVastus intermediusThigh: Anatomy
    • SensorySensoryNeurons which conduct nerve impulses to the central nervous system.Nervous System: Histology innervation: gives rise to the medial and intermediate cutaneous nerves of thethighThighThe thigh is the region of the lower limb found between the hip and the knee joint. There is a single bone in the thigh called the femur, which is surrounded by large muscles grouped into 3 fascial compartments.Thigh: Anatomy, supplying the anteriorthighThighThe thigh is the region of the lower limb found between the hip and the knee joint. There is a single bone in the thigh called the femur, which is surrounded by large muscles grouped into 3 fascial compartments.Thigh: Anatomy and mediallegLegThe lower leg, or just “leg” in anatomical terms, is the part of the lower limb between the knee and the ankle joint. The bony structure is composed of the tibia and fibula bones, and the muscles of the leg are grouped into the anterior, lateral, and posterior compartments by extensions of fascia.Leg: Anatomy
    • Joints: innervates hip and knee joints
  • Lateral femoral cutaneous nerve:
    • Lateral cutaneous nerve of thethighThighThe thigh is the region of the lower limb found between the hip and the knee joint. There is a single bone in the thigh called the femur, which is surrounded by large muscles grouped into 3 fascial compartments.Thigh: Anatomy
    • Origin: L2–L3spinal nervesSpinal nervesThe 31 paired peripheral nerves formed by the union of the dorsal and ventral spinal roots from each spinal cord segment. The spinal nerve plexuses and the spinal roots are also included.Spinal Cord: Anatomy
    • SensorySensoryNeurons which conduct nerve impulses to the central nervous system.Nervous System: Histology innervation: cutaneous sensation from the lateral part of thethighThighThe thigh is the region of the lower limb found between the hip and the knee joint. There is a single bone in the thigh called the femur, which is surrounded by large muscles grouped into 3 fascial compartments.Thigh: Anatomy
    • NomotorMotorNeurons which send impulses peripherally to activate muscles or secretory cells.Nervous System: Histology function
  • Obturator nerveObturator NerveA nerve originating in the lumbar spinal cord (L2 to L4) and traveling through the lumbar plexus to the lower extremity. The obturator nerve provides motor innervation to the adductor muscles of the thigh and cutaneous sensory innervation of the inner thigh.Thigh: Anatomy:
    • Origin: L2–L4spinal nervesSpinal nervesThe 31 paired peripheral nerves formed by the union of the dorsal and ventral spinal roots from each spinal cord segment. The spinal nerve plexuses and the spinal roots are also included.Spinal Cord: Anatomy
    • MotorMotorNeurons which send impulses peripherally to activate muscles or secretory cells.Nervous System: Histology innervation: medialthighThighThe thigh is the region of the lower limb found between the hip and the knee joint. There is a single bone in the thigh called the femur, which is surrounded by large muscles grouped into 3 fascial compartments.Thigh: Anatomy compartment (hip adductors)
    • SensorySensoryNeurons which conduct nerve impulses to the central nervous system.Nervous System: Histology innervation: medial aspect of thethighThighThe thigh is the region of the lower limb found between the hip and the knee joint. There is a single bone in the thigh called the femur, which is surrounded by large muscles grouped into 3 fascial compartments.Thigh: Anatomy
  • Accessoryobturator nerveObturator NerveA nerve originating in the lumbar spinal cord (L2 to L4) and traveling through the lumbar plexus to the lower extremity. The obturator nerve provides motor innervation to the adductor muscles of the thigh and cutaneous sensory innervation of the inner thigh.Thigh: Anatomy: present in about 30% of cases (comes from L3–L4spinal nervesSpinal nervesThe 31 paired peripheral nerves formed by the union of the dorsal and ventral spinal roots from each spinal cord segment. The spinal nerve plexuses and the spinal roots are also included.Spinal Cord: Anatomy)

Clinical Relevance

• Hiccups:involuntary, spasmodic contractions of thediaphragmDiaphragmThe diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force.Diaphragm: Anatomy, leading to quick inhalations that are interrupted by the involuntary closure of theglottisGlottisThe vocal apparatus of the larynx, situated in the middle section of the larynx. Glottis consists of the vocal folds and an opening (rima glottidis) between the folds.Larynx: Anatomy. Hiccups can result from irritation of nerve endings or of medullary centers in thebrainBrainThe part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem.Nervous System: Anatomy, Structure, and Classification stem (which controlrespirationRespirationThe act of breathing with the lungs, consisting of inhalation, or the taking into the lungs of the ambient air, and of exhalation, or the expelling of the modified air which contains more carbon dioxide than the air taken in.Nose Anatomy (External & Internal)). Among the causes are indigestion,diaphragmDiaphragmThe diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force.Diaphragm: Anatomy irritation,alcoholismAlcoholismA primary, chronic disease with genetic, psychosocial, and environmental factors influencing its development and manifestations. The disease is often progressive and fatal. It is characterized by impaired control over drinking, preoccupation with the drug alcohol, use of alcohol despite adverse consequences, and distortions in thinking, most notably denial. Each of these symptoms may be continuous or periodic.Wernicke Encephalopathy and Korsakoff Syndrome, cerebral lesions, and thoracic and abdominal lesions, all of which disturb the phrenic nerves.
• Congenital diaphragmatic herniasCongenital diaphragmatic herniasCongenital diaphragmatic hernias are embryologically derived defects in the diaphragm through which abdominal structures can pass into the chest cavity. The presence of intestines and intra-abdominal organs in the chest interferes with embryonic development of the lungs, which is the major cause of pathology postnatally.Congenital Diaphragmatic Hernias: embryologically derived defects in thediaphragmDiaphragmThe diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force.Diaphragm: Anatomy through which abdominal structures can pass into the chest cavity. Prenatal diagnosis is commonly made by ultrasonography duringpregnancyPregnancyThe status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth.Pregnancy: Diagnosis, Physiology, and Care followed by confirmation on chestx-rayX-rayPenetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source.Pulmonary Function Tests after birth. Immediate respiratoryresuscitationResuscitationThe restoration to life or consciousness of one apparently dead. .Neonatal Respiratory Distress Syndrome at birth with endotrachealintubationIntubationPeritonsillar Abscess and mechanicalventilationVentilationThe total volume of gas inspired or expired per unit of time, usually measured in liters per minute.Ventilation: Mechanics of Breathing are required. Surgical repair is the only curative option.PrognosisPrognosisA prediction of the probable outcome of a disease based on a individual’s condition and the usual course of the disease as seen in similar situations.Non-Hodgkin Lymphomas varies, but children with diaphragmatic hernias usually suffer from lifelong pulmonary complications. 
• Psoas signPsoas signWhen there is RLQ pain with passive hip extension (characteristic of retrocecal appendix)Appendicitis:abdominal exam finding in acuteappendicitisAppendicitisAppendicitis is the acute inflammation of the vermiform appendix and the most common abdominal surgical emergency globally. The condition has a lifetime risk of 8%. Characteristic features include periumbilical abdominal pain that migrates to the right lower quadrant, fever, anorexia, nausea, and vomiting.Appendicitis. Finding is RLQpainPainAn unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons.Pain: Types and Pathways with passive right hipextensionExtensionExamination of the Upper Limbs (characteristic ofretrocecal appendixRetrocecal appendixAppendicitis, where the inflamedappendixAppendixA worm-like blind tube extension from the cecum.Colon, Cecum, and Appendix: Anatomy lies against the rightpsoas musclePsoas muscleA powerful flexor of the thigh at the hip joint (psoas major) and a weak flexor of the trunk and lumbar spinal column (psoas minor). Psoas is derived from the greek ‘psoa.Pyelonephritis and Perinephric Abscess).
• Psoas abscessPsoas abscessAbscess of the psoas muscles resulting usually from disease of the lumbar vertebrae, with the pus descending into the muscle sheath. The infection is most commonly tuberculous or staphylococcal.Pyelonephritis and Perinephric Abscess: purulent collection in the iliopsoas muscle compartment. The condition can be secondary to spread from adjacent structures or byhematogenousHematogenousHepatocellular Carcinoma (HCC) and Liver Metastases spread from a distant site.Staphylococcus aureusStaphylococcus aureusPotentially pathogenic bacteria found in nasal membranes, skin, hair follicles, and perineum of warm-blooded animals. They may cause a wide range of infections and intoxications.Brain Abscess is the most common bacterium causing this infection. Tuberculosis-related abscesses  are seen in regions whereMycobacterium tuberculosisMycobacterium tuberculosisTuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis complex bacteria. The bacteria usually attack the lungs but can also damage other parts of the body. Approximately 30% of people around the world are infected with this pathogen, with the majority harboring a latent infection. Tuberculosis spreads through the air when a person with active pulmonary infection coughs or sneezes.Tuberculosis is endemic. Common signs and symptoms include backpainPainAn unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons.Pain: Types and Pathways,feverFeverFever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin.Fever, and abdominal andflank painFlank painPain emanating from below the ribs and above the ilium.Renal Cell Carcinoma. Diagnosis is via CT scan, along with cultures of blood andabscessAbscessAccumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection.Chronic Granulomatous Disease material. Management includes drainage and use of appropriate antibiotics.
• PyelonephritisPyelonephritisPyelonephritis is infection affecting the renal pelvis and the renal parenchyma. This condition arises mostly as a complication of bladder infection that ascends to the upper urinary tract. Pyelonephritis can be acute or chronic (which results from persistent or chronic infections). Typical acute symptoms are flank pain, fever, and nausea with vomiting. TPyelonephritis and Perinephric Abscess: infection affecting therenal pelvisRenal pelvisKidneys: Anatomy and the renal parenchyma. This condition arises mostly from abladderBladderA musculomembranous sac along the urinary tract. Urine flows from the kidneys into the bladder via the ureters, and is held there until urination.Pyelonephritis and Perinephric Abscess infection ascending to the upperurinary tractUrinary tractThe urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra.Urinary Tract: Anatomy. Typical symptoms areflank painFlank painPain emanating from below the ribs and above the ilium.Renal Cell Carcinoma,feverFeverFever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin.Fever, andnauseaNauseaAn unpleasant sensation in the stomach usually accompanied by the urge to vomit. Common causes are early pregnancy, sea and motion sickness, emotional stress, intense pain, food poisoning, and various enteroviruses.Antiemetics withvomitingVomitingThe forcible expulsion of the contents of the stomach through the mouth.Hypokalemia. ThekidneysKidneysThe kidneys are a pair of bean-shaped organs located retroperitoneally against the posterior wall of the abdomen on either side of the spine. As part of the urinary tract, the kidneys are responsible for blood filtration and excretion of water-soluble waste in the urine.Kidneys: Anatomy can be examined through the costovertebral angle (formed by the 12th rib andvertebral columnVertebral columnThe human spine, or vertebral column, is the most important anatomical and functional axis of the human body. It consists of 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae and is limited cranially by the skull and caudally by the sacrum.Vertebral Column: Anatomy) of the posteriorabdominal wallAbdominal wallThe outer margins of the abdomen, extending from the osteocartilaginous thoracic cage to the pelvis. Though its major part is muscular, the abdominal wall consists of at least seven layers: the skin, subcutaneous fat, deep fascia; abdominal muscles, transversalis fascia, extraperitoneal fat, and the parietal peritoneum.Surgical Anatomy of the Abdomen. The diagnosis is established via clinical presentation and laboratory findings (in blood and urine). Imaging studies are performed if severe illness is noted or if there is no response to initial treatment (antibiotics).

References

1. Drake, R., Vogl, A.W.,  Mitchell, A. (2020) Regional anatomy, posterior abdominal region. Chapter 4 of Gray’s Anatomy for Students, 4th ed. Churchill Livingstone/Elsevier, pp. 365–373.
2. Moore, K. L., Dalley, A. F., Agur, A. M. R. (2014). Abdomen. Chapter 2 of Clinically Oriented Anatomy, 7th ed. Lippincott Williams & Wilkins, pp. 309–321.
3. Morton D.A., Foreman K., Albertine, K.H. (Eds.) (2019). Posterior abdominal wall. In: The Big Picture: Gross Anatomy, 2nd ed. McGraw-Hill. Retrieved fromhttps://accessmedicine.mhmedical.com/content.aspx?bookid=2478&sectionid=202020626
4. Nunn, J.F., Khan, Y.S. (2020). Anatomy, abdomen and pelvis, posterior abdominal wall nerves. StatPearls. Retrieved from:https://www.ncbi.nlm.nih.gov/books/NBK557605/