Posterior Abdominal Wall: Anatomy

Introduction

Posterior abdominal wall Abdominal wall The 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
• Supports retroperitoneal Retroperitoneal Peritoneum: Anatomy organs and contains important neurovascular structures
• Boundaries:
  • Anteriorly by:
    • Anterolateral abdominal muscles
    • Retroperitoneal Retroperitoneal Peritoneum: Anatomy organs
    • Parietal Parietal One 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: Anatomy peritoneum Peritoneum The 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 vertebrae Lumbar vertebrae Vertebrae in the region of the lower back below the thoracic vertebrae and above the sacral vertebrae. Vertebral Column: Anatomy
    • Muscles
    • Fascia Fascia Layers 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 and diaphragm Diaphragm The 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

• Fascia Fascia Layers 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
  • Diaphragm Diaphragm The 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
• Parietal Parietal One 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: Anatomy peritoneum Peritoneum The 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
  • Abdominal aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy
  • Inferior vena cava Inferior vena cava The 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

Thoracolumbar fascia Fascia Layers 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 of connective tissue Connective tissue Connective 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 the internal oblique Internal oblique Muscles 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 and transversus abdominis Transversus abdominis Anterior 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 deep muscles of the back Muscles of the back The 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 of lumbar vertebrae Lumbar vertebrae Vertebrae 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 the transversus abdominis Transversus abdominis Anterior Abdominal Wall: Anatomy muscle

Psoas fascia Fascia Layers 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 the lumbar vertebrae Lumbar vertebrae Vertebrae 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 iliac fascia Fascia Layers 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 thoracolumbar fascia Fascia Layers 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 anterior abdominal wall Abdominal wall The 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, herniation Herniation Omphalocele can occur in weakened areas in the posterior abdominal wall Abdominal wall The 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 oblique External oblique Muscles 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 of herniation Herniation Omphalocele
  • Bound by:
    • Quadratus lumborum medially
    • Internal oblique Internal oblique Muscles 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
    • Transversalis fascia Fascia Layers 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

• Diaphragm Diaphragm The 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 hiatus Esophageal hiatus Diaphragm: Anatomy (T10)
    • Aortic hiatus Aortic hiatus Diaphragm: Anatomy (T12)
  • Origin:
    • Xiphoid process Xiphoid process Chest Wall: Anatomy
    • Ribs Ribs A 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
    • Upper lumbar vertebrae Lumbar vertebrae Vertebrae in the region of the lower back below the thoracic vertebrae and above the sacral vertebrae. Vertebral Column: Anatomy
  • Insertion: the middle part of the central tendon Central tendon Diaphragm: Anatomy
  • Functions:
    • Major muscle of respiration Respiration The 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) and expiration Expiration Ventilation: Mechanics of Breathing (relaxation)
    • Abdominal straining (increasing intraabdominal pressure)
    • Separates the abdominal cavity from the thoracic cavity 
  • Motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology innervation: right and left phrenic nerves (originate from cervical spinal cord Spinal cord The 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)
  • Sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology innervation:
    • Phrenic nerve Phrenic nerve The 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 of diaphragm Diaphragm The 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 of diaphragm Diaphragm The 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 the kidneys Kidneys The 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 the lumbar vertebrae Lumbar vertebrae Vertebrae in the region of the lower back below the thoracic vertebrae and above the sacral vertebrae. Vertebral Column: Anatomy
    • Stabilizes the 12th rib during respiration Respiration The 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: hip flexion Flexion Examination of the Upper Limbs, lateral flexion Flexion Examination 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: flexes thigh Thigh The 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 the hip joint Hip joint The 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 nerve Femoral Nerve A 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 posterior abdominal wall Abdominal wall The 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 column Vertebral column The 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:
  • 12th thoracic vertebrae Thoracic vertebrae A group of twelve vertebrae connected to the ribs that support the upper trunk region. Vertebral Column: Anatomy
  • Lumbar vertebrae Lumbar vertebrae Vertebrae in the region of the lower back below the thoracic vertebrae and above the sacral vertebrae. Vertebral Column: Anatomy (L1–L5)
  • Sacrum Sacrum Five 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 the hip bone Hip bone Bones 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 posterior abdominal wall Abdominal wall The 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

Abdominal aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy

• Relation:
  • Continuation of the thoracic aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy
  • Enters the abdomen through the aortic hiatus Aortic hiatus Diaphragm: Anatomy in the diaphragm Diaphragm The 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 the vertebral column Vertebral column The 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 iliac arteries Arteries Arteries 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
• Different arteries Arteries Arteries 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 abdominal aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy:
  • Unpaired branches:
    • Celiac trunk
    • Superior mesenteric artery Superior mesenteric artery A 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 artery Inferior mesenteric artery The 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/suprarenal arteries Arteries Arteries 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
    • Renal arteries Arteries Arteries 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
    • Gonadal arteries Arteries Arteries 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 phrenic arteries Arteries Arteries 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
    • Lumbar arteries Arteries Arteries 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 iliac arteries Arteries Arteries 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 ( aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy bifurcates)

Inferior vena cava Inferior vena cava The 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 iliac veins Veins Veins 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 the aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy
  • Goes through the diaphragm Diaphragm The 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:
  • Hepatic veins Veins Veins 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 phrenic veins Veins Veins 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
  • Renal veins Veins Veins 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 suprarenal veins Veins Veins 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 left renal vein Renal vein Short thick veins which return blood from the kidneys to the vena cava. Glomerular Filtration, which then drains into the inferior vena cava Inferior vena cava The venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs. Mediastinum and Great Vessels: Anatomy.
  • Lumbar veins Veins Veins 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

• Most lymph nodes Lymph Nodes They are oval or bean shaped bodies (1 – 30 mm in diameter) located along the lymphatic system. Lymphatic Drainage System: Anatomy are located beside the vascular channels Channels The Cell: Cell Membrane running along the posterior abdominal wall Abdominal wall The 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 mesenteric lymph nodes Lymph Nodes They are oval or bean shaped bodies (1 – 30 mm in diameter) located along the lymphatic system. Lymphatic Drainage System: Anatomy
  • Adrenal glands Adrenal Glands The 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-aortic lymph nodes Lymph Nodes They are oval or bean shaped bodies (1 – 30 mm in diameter) located along the lymphatic system. Lymphatic Drainage System: Anatomy
  • Urinary tract Urinary tract The 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 lumbar lymph nodes Lymph Nodes They are oval or bean shaped bodies (1 – 30 mm in diameter) located along the lymphatic system. Lymphatic Drainage System: Anatomy
  • Gonads Gonads The gamete-producing glands, ovary or testis. Hormones: Overview and Types/reproductive tract: lumbar, iliac inguinal lymph nodes Lymph Nodes They 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 lumbar spinal nerves Spinal nerves The 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
  • Motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology supply to the abdominal wall Abdominal wall The 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 oblique External oblique Muscles 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 oblique Internal oblique Muscles 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, and rectus abdominis Rectus Abdominis A 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)
  • Sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology innervation to the T12 dermatome Dermatome Spinal Disk Herniation (anterolateral region)
• Lumbar plexus:
  • Iliohypogastric nerve:
    • Origin: ventral rami of L1 spinal nerves Spinal nerves The 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
    • Motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology innervation: supplies the internal oblique Internal oblique Muscles 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 and transversus abdominis Transversus abdominis Anterior Abdominal Wall: Anatomy muscles
    • Sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology innervation: hypogastric region
  • Ilioinguinal nerve Ilioinguinal nerve Inguinal Canal: Anatomy and Hernias:
    • Origin: ventral rami of L1
    • Motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology innervation: internal oblique Internal oblique Muscles 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 and transversus abdominis Transversus abdominis Anterior Abdominal Wall: Anatomy muscles along with the iliohypogastric nerve
    • Sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology innervation: superomedial aspect of the thigh Thigh The 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 nerve Genitofemoral nerve Inguinal Canal: Anatomy and Hernias:
    • Origin: ventral rami of L1–L2 spinal nerves Spinal nerves The 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: the cremaster muscle Cremaster muscle Testicles: Anatomy (male), skin Skin The 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 of mons pubis Mons pubis Vagina, Vulva, and Pelvic Floor: Anatomy and labia majora Labia majora Vagina, Vulva, and Pelvic Floor: Anatomy (female)
    • Femoral branch: sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology innervation of the femoral triangle Femoral triangle Femoral Region and Hernias: Anatomy
    •  Both sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology and motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology parts of the cremasteric reflex Cremasteric Reflex Male Genitourinary Examination
  • Femoral nerve Femoral Nerve A 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–L4 spinal nerves Spinal nerves The 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
    • Motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology innervation: pectineus Pectineus Thigh: Anatomy, sartorius Sartorius Thigh: Anatomy, rectus femoris Rectus femoris Thigh: Anatomy, vastus lateralis Vastus lateralis Thigh: Anatomy, vastus medialis Vastus medialis Thigh: Anatomy, and vastus intermedius Vastus intermedius Thigh: Anatomy
    • Sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology innervation: gives rise to the medial and intermediate cutaneous nerves of the thigh Thigh The 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 anterior thigh Thigh The 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 medial leg Leg The 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 the thigh Thigh The 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–L3 spinal nerves Spinal nerves The 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
    • Sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology innervation: cutaneous sensation from the lateral part of the thigh Thigh The 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
    • No motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology function
  • Obturator nerve Obturator Nerve A 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–L4 spinal nerves Spinal nerves The 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
    • Motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology innervation: medial thigh Thigh The 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)
    • Sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology innervation: medial aspect of the thigh Thigh The 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
  • Accessory obturator nerve Obturator Nerve A 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–L4 spinal nerves Spinal nerves The 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 the diaphragm Diaphragm The 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 the glottis Glottis The 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 the brain Brain The 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 control respiration Respiration The 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, diaphragm Diaphragm The 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, alcoholism Alcoholism A 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 hernias Congenital diaphragmatic hernias Congenital 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 the diaphragm Diaphragm The 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 during pregnancy Pregnancy The 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 chest x-ray X-ray Penetrating 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 respiratory resuscitation Resuscitation The restoration to life or consciousness of one apparently dead. . Neonatal Respiratory Distress Syndrome at birth with endotracheal intubation Intubation Peritonsillar Abscess and mechanical ventilation Ventilation The 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. Prognosis Prognosis A 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 sign Psoas sign When there is RLQ pain with passive hip extension (characteristic of retrocecal appendix) Appendicitis: abdominal exam finding in acute appendicitis Appendicitis Appendicitis 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 RLQ pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways with passive right hip extension Extension Examination of the Upper Limbs (characteristic of retrocecal appendix Retrocecal appendix Appendicitis, where the inflamed appendix Appendix A worm-like blind tube extension from the cecum. Colon, Cecum, and Appendix: Anatomy lies against the right psoas muscle Psoas muscle A 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 abscess Psoas abscess Abscess 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 by hematogenous Hematogenous Hepatocellular Carcinoma (HCC) and Liver Metastases spread from a distant site. Staphylococcus aureus Staphylococcus aureus Potentially 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 where Mycobacterium tuberculosis Mycobacterium tuberculosis Tuberculosis (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 back pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways, fever Fever Fever 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 and flank pain Flank pain Pain emanating from below the ribs and above the ilium. Renal Cell Carcinoma. Diagnosis is via CT scan, along with cultures of blood and abscess Abscess Accumulation 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.
• Pyelonephritis Pyelonephritis Pyelonephritis 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. T Pyelonephritis and Perinephric Abscess: infection affecting the renal pelvis Renal pelvis Kidneys: Anatomy and the renal parenchyma. This condition arises mostly from a bladder Bladder A 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 upper urinary tract Urinary tract The 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 are flank pain Flank pain Pain emanating from below the ribs and above the ilium. Renal Cell Carcinoma, fever Fever Fever 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 nausea Nausea An 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 with vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia. The kidneys Kidneys The 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 and vertebral column Vertebral column The 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 posterior abdominal wall Abdominal wall The 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).