Abdomen Anatomy Lecture Notes PDF

ANATOMY-LEC: LE 4 | TRANS 1 Abdomen in General SANDY C. MAGANITO, MD | Lecture Date (01/06/2025) re OUTLINE o​ Transpyloric plane I.​ Introduction...

ANATOMY-LEC: LE 4 | TRANS 1 Abdomen in General SANDY C. MAGANITO, MD | Lecture Date (01/06/2025) re OUTLINE o​ Transpyloric plane I.​ Introduction V. Inguinal Region o​ Hesselbach triangle A.​ Abdomen A.​ Inguinal Ligament o​ Intertubercular plane B.​ Peritoneal B.​ Iliopubic Tract o​ McBurney point Organization C.​ Inguinal Canal ✔​ How the abdomen is divided into quadrants and nine II.​ Abdominal Quadrants VI. Posterior Abdominal wall regions recognizing the clinical application of such and Regions A.​ Components ✔​ Naming the layers of the anterolateral abdominal wall A.​ Abdominal B.​ Fascia Layer of the from outward, going inwards and defining the extent Quadrants Posterior of each B.​ Abdominal Endoabdominal Wall ✔​ Describing the deposition of the superficial and deep Regions and C.​ Posterior Abdominal fascia in the anterolateral abdominal wall Planes Wall Muscles ✔​ Describing the formation of the rectus sheath III. Abdominal Wall D.​ Nerve Supply of the including its variations at various levels IV. Anterolateral Posterior Abdominal ✔​ Naming the contents of the rectus sheath recognizing Abdominal Wall Wall Muscles the potential anastomotic relationship between the A.​ Boundaries VII. Peritoneum and superior and inferior epigastric vessels B.​ Fascial Peritoneal Cavity ✔​ Identifying the linea alba, semilunar line, tendinous Organization A.​ Peritoneum: Structure intersections, arcuate line, and pyramidalis muscle (if C.​ Layers and Function present) D.​ Muscles B.​ Peritoneal Cavity ✔​ Describing the nerves and blood vessels of the E.​ Rectus Sheath C.​ Embryology anterolateral abdominal wall F.​ Internal Surface VIII. Review Questions​ ✔​ Describing the disposition of the peritoneum G.​ Other Structures IX. References H.​ Arterial and X. Appendix I. INTRODUCTION Venous Supply of A. ABDOMEN the Anterolateral ​ Anatomical position: Between thorax and pelvis Abdominal Wall ​ Function: Dynamic container for vital organs I.​ Lymphatic ​ Primary contents: Drainage of the →​Alimentary organs Anterolateral →​Parts of urogenital system Abdominal Wall ​ Structural support of the abdomen J.​ Dermatomes of → Superior: Thoracic skeleton the Anterolateral → Inferior: Pelvic girdle Abdominal Wall → Posterior: Lumbar vertebral column K.​ Nerve Supply → Anterolateral Walls: Musculoaponeurotic composition L.​ Clinical ​ Walls: Correlation of the → Superior: Diaphragm Anterolateral → Anterolateral: Musculoaponeurotic walls Abdominal Wall SUMMARY OF ABBREVIATIONS 📣 → Inferior: Pelvic muscles This arrangement of walls creates a flexible container ​ Dynamic Functions ASIS Anterior Superior Iliac Spine ICS Intercostal Space →​Respiratory movements IV Intervertebral → Postural control IVC Inferior Vena Cava → Intra-abdominal pressure regulation MCL Midclavicular Line TFL Tensor Fascia Latae ❗️ Must know 📣 Lecturer 📖 Book 📋 Previous Trans LEARNING OBJECTIVES Demonstrate knowledge and understanding of the gross (SPACE LEFT INTENTIONALLY BLANK) anatomy of the anterolateral abdominal wall, including the peritoneal deposition, by: ✔​ Identifying the anatomical landmarks used in the study of the surface anatomy of the abdomen on the articulated skeleton, the cadaver, and the living subject. ✔​ Describing how the following are marked out on the body surface: LE 4 TRANS 1 VER 1 TG-A13: L. Caro, M. Casao, L. Castaneda, K. Castillo, N. TE: L. Caro AVPAA: K. Casumbal Page 1 of 20 Castillo, A. Catan, E. Chavez, Y. Chavez, E. Cheng  →​Left Upper Quadrant (LUQ) →​Right Lower Quadrant (RLQ) →​Left Lower Quadrant (LLQ) Figure 1. Abdomen B. PERITONEAL ORGANIZATION ​ The peritoneum is a serous membrane with 2 components– Parietal and Visceral peritoneum ​ Parietal peritoneum Figure 3. Abdominal quadrants → Lines cavity walls ​ Visceral peritoneum Table 1. Contents of the quadrants → Covers organs Right Upper Quadrant Left Upper Quadrant ​ Between these layers lie the peritoneal cavity containing Liver: right lobe Liver: left lobe just enough fluid for lubrication Gallbladder Spleen ​ There are areas wherein there’s a double layered Stomach: pylorus Stomach reflection of the peritoneum and contains the ff: Duodenum: parts 1-3 Jejunum and proximal ileum → Blood vessels Pancreas: head Pancreas: body and tail → Lymphatics Right suprarenal gland Left kidney 📣→ Nerves Ex: the visceral peritoneum holds upon itself and wraps around the organs. It creates a double layer of Right kidney Right colic(hepatic) flexure Left suprarenal gland Left colic (splenic flexure Ascending colon: superior Transverse colon: left half peritoneum and pouches wherein blood vessels, part Descending colon: superior lymphatics, and nerves are located. Transverse colon: right half part Right Lower Quadrant Left Lower Quadrant Cecum Sigmoid colon Appendix Descending colon: inferior Most of ileum part Ascending colon: inferior Left ovary part Left uterine tube Right ovary Left ureter: abdominal part Right uterine tube Left spermatic cord: Right ureter: abdominal part abdominal part Right spermatic cord: Uterus (if enlarged) abdominal part Urinary bladder (if very full) uterus (if enlarged) Urinary bladder (if very full) B.​ ABDOMINAL REGIONS AND PLANES ​ Sagittal planes → Midclavicular planes (9 cm from midline) ​ Transverse planes Figure 2. Peritoneum Structure → Subcostal plane - inferior border of 10th costal cartilage → Transtubercular plane - through iliac tubercles II. ABDOMINAL QUADRANTS AND REGIONS → Transpyloric plane A.​ ABDOMINAL QUADRANTS ​ Divided by: →​Transumbilical plane - (at L3-L4 disc level) →​Median plane ​ Quadrants →​Right Upper Quadrant (RUQ) ANATOMY Abdomen in General Page 2 of 20  📣 While the anterior and lateral regions consist of muscle and aponeurosis, the posterior wall is unique, incorporating the lumbar spine. The transition between the anterior and lateral wall is gradual—leading to the common term, anterolateral abdominal wall Figure 4. Abdominal Regions and Planes TRANSPYLORIC PLANE ​ Location: Midway between manubrium and pubic symphysis (L1 vertebral level) ❗️ ​ The transpyloric plane is an important landmark for the structures listed below, as it transects: → Pylorus of the stomach (when recumbent) Figure 6. Abdominal wall IV. ANTEROLATERAL ABDOMINAL WALL →​ Fundus of the gallbladder A. BOUNDARIES →​ Neck of the pancreas ​ Superior →​ Origins of the superior mesenteric artery (SMA) and →​ Cartilages of the 7th -10th ribs hepatic portal vein →​ Xiphoid process of the sternum →​ Root of the transverse mesocolon ​ Inferior →​ Duodenojejunal junction →​ Inguinal ligament →​ Hila of the kidneys →​ Superior margins of the anterolateral aspects of the pelvic girdle (iliac crests, pubic crests, and pubic symphysis) B. FASCIAL ORGANIZATION ​ Above the umbilicus →​The subcutaneous tissue is consistent with that found in 📣 most regions This regional variation in fascial organization is clinically significant for surgical approaches ​ Below the umbilicus →​Superficial fatty layer (Camper’s fascia) →​Deep membranous layer (Scarpa’s fascia) ○​ Continues as the Colles fascia as it enters the perineal region (SPACE LEFT INTENTIONALLY BLANK) Figure 5: Transpyloric plane III. ABDOMINAL WALL ​ Subdivided into: → Anterior → Lateral (Right and left) → Posterior → Anterolateral abdominal wall ANATOMY Abdomen in General Page 3 of 20  C. LAYERS D. MUSCLES Figure 7. Layers of the anterolateral abdominal wall ​ These layers are applicable only inferior to the umbilicus ​ Skin ​ Superficial fatty layer (Camper fascia) → Fat tissue ​ Deep membranous layer (Scarpa fascia) Colles fascia 📣 → Continues into the perineal region where it is known as Above the umbilicus, the subcutaneous tissue maintaining a more uniform structure typically what 📋 Figure 8. Muscles of the Anterolateral abdominal wall[Moore] There are five (bilaterally paired) muscles in the we find in other regions of the body. This regional variation anterolateral abdominal wall: 3 flat muscles and 2 vertical in fascial organization is clinically significant for surgical muscles [See Appendix Table 9] approaches. ​ Three (3) flat muscles ​ Investing (deep) Fascia →​External Oblique (EO) Muscle → Superficial ▪​ The largest and most superficial of the abdominal → Intermediate wall muscles → Deep ▪​ Fibers run inferomedially; “hands in your side pocket” -​ Envelopes the muscle layers and their aponeurosis ▪​ Does not originate posteriorly from the thoracolumbar -​ Composed of epimysium and is exceptionally thin fascia unlike the deeper muscles and firmly adherent to the underlying structures making gross dissection challenging 📋 ▪​ Inferior margin of EO aponeurosis = inguinal ligament Muscular laterally and aponeurotic towards the 📋 ​ Endoabdominal or Transversalis Fascia midline Internal aspect of the abdominal wall lined with the ○​ Aponeurotic fibers at the level of the ASIS thicken 📋 membranous and areolar sheet of varying thickness Although continuous, different parts of this fascia are ligament ❗️ up to the pubic tubercle forming the inguinal 📋 names according to the muscle or aponeurosis it is lining o​ Continues as external spermatic fascia which Transversalis Fascia: Portion lining the deep surface of covers the spermatic cord 📣 transversus abdominis muscle and its aponeurosis →​Internal Oblique (IO) Muscle Endoabdominal fascia as umbrella term with the ▪​ Middle layer of the flat abdominal muscles transversalis fascia being one of its regional components ▪​ Fibers running superomedially; “hands on your chest” 📋 →​Extraperitoneal fat 📋 ▪​ Perpendicular to the external oblique 📋 Layer of fat before the peritoneum Smaller and thinner than external oblique; Muscular Found between the endoabdominal fascia and parietal peritoneum 📣 laterally and aponeurotic towards the midline Lowermost fibers follow a different orientation pattern →​Parietal Peritoneum 📋 ▪​ Separated by extraperitoneal fat →​Transversus Abdominis (TA) Muscle 📋 Glistening lining of the abdominal cavity ▪​ Innermost/deepest of the three flat abdominal Formed by a single layer of epithelial cells and muscles featuring a horizontal fibers EXCEPT in the supporting connective tissue inferior portion where they parallel the run to the IO ▪​ Circumferential orientation ▪​ In between IO and TA is the neurovascular plane/bundle of the anterolateral abdominal wall ▪​ Its aponeurosis contributes to the rectus sheath (SPACE LEFT INTENTIONALLY BLANK) 📋 formation Oriented transversely to compress the abdominal contents and increase the intra-abdominal pressure ANATOMY Abdomen in General Page 4 of 20  E. RECTUS SHEATH Figure 9. Muscles of the Anterolateral abdominal wall [Lecturer’s PPT] ​ Two (2) vertical muscles: →​Rectus Abdominis Muscle ▪​ Principal/main abdominal muscle of the anterior abdominal wall ▪​ Paired rectus muscle separated by the linea alba, lie close together inferiorly Figure 10. Rectus Sheath[Lecturer’s PPT] ▪​ Powerful flexor of the thoracic and lumbar regions of ​ A fibrous enclosure of the rectus abdominis muscle ❗️ the trunk →​Pyramidalis ​ Formed by the decussation and interweaving of the aponeurosis of the flat abdominal muscles →​External oblique aponeurosis → contributes to the ▪​ Tenses the linea alba ❗️ ▪​ Absent in approximately 20% of individuals ​ Both are contained within the rectus sheath. These anterior wall all throughout →​Internal oblique aponeurosis → shows regional variation ▪​ Superior ⅔: splits into two: one lamina passing muscles act as an antagonist of the diaphragm to produce anterior; passing posterior. expiration ▪​ Inferior ⅓: all three flat muscles pass anterior to the rectus abdominis muscle ▪​ Arcuate line - significant anatomical landmark ○​ Above: Aponeurotic posterior wall contract with transversalis fascia; 📋 ○​ Below: Rectus abdominis muscle is directly in No posterior 📣 rectus sheath, only the transversus abdominis ms. This transition occurs approximately the superior 3 📋 quarters of the abdominis muscle ​ Contents →​Superior and inferior epigastric arteries and veins →​Lymphatic vessels →​Distal portions of the thoraco-abdominal nerves (SPACE LEFT INTENTIONALLY BLANK) LINEA ALBA ​ Vertical structure running the length of the anterior abdominal wall and separating the bilateral rectus sheath in right and left compartments ​ ​ Superior to the umbilicus → widens to the width of the xiphoid process ​ Inferior to the umbilicus → narrows to the width of the ​📋pubic Interlacing fibers of the anterior and posterior layers of the rectus sheath at the anterior median line ANATOMY Abdomen in General Page 5 of 20  UMBILICAL RING PERITONEAL FOSSAE ​ All layers of the anterolateral abdominal wall fuse/unite at the umbilicus ​ Develops during fetal life, lacks muscle fiber hence weak and usual site where hernia may occur F. INTERNAL SURFACE 📣 [Lecturer’s PPT] Figure 12. Peritoneal Fossae Clinically significant fossa which are potential sites for Figure 11. Umbilical Peritoneal Folds[Lecturer’s PPT] herniation UMBILICAL FOLDS (5) Table 2. Summary of the Peritoneal Fossae ​ Median umbilical fold (1) Fossae Description Defect →​Runs centrally from the apex of the urinary bladder to Supravesical Between median Supravesical the umbilicus fossa and medial hernia (external 📋remnant of the urachus ❗️ →​Covers the median umbilical ligament; a fibrous Urachus: joins apex of the fetal bladder to umbilicus umbilical folds and internal) causes intestinal obstruction; ​ Medial umbilical folds (2) extremely rare →​Cover the medial umbilical ligaments, formed by occluded parts of the umbilical arteries ​ Lateral umbilical folds (2) Medial inguinal Between the Direct inguinal →​Cover the inferior epigastric vessels (bleeds when cut) fossa medial and lateral hernias (less ​ All layers of the anterolateral abdominal wall fuse/unite at umbilical folds common) the umbilicus ​ Develop during fetal life, lacks muscle fiber hence weak Commonly and usual site where hernia may occur known as inguinal triangle of Hesselbach (inguinal triangles or Hesselbach triangles) Lateral inguinal Lateral to the Indirect inguinal fossa lateral umbilical hernia (most folds, includes common type of deep inguinal hernia in lower rings abdominal wall) (SPACE LEFT INTENTIONALLY BLANK) ANATOMY Abdomen in General Page 6 of 20  FALCIFORM LIGAMENT Semilunar Line Figure 15. Semilunar Line [Lecturer PPT] ​ Spigelian Line; Linea semilunares ​ Lightly curves, linear impressions in the skin that extend from the inferior costal margin near the 9th costal cartilages to the pubic tubercles. ​ These semilunar skin grooves (5-8 cm from the midline) are clinically important because they are parallel with the lateral edges of the rectus sheath. Figure 13. Falciform Ligament[Lecturer’s PPT] ​ Superior anterior abdominal wall and the liver ​ Encloses: →​Round ligament of the liver (Ligamentum Teres Hepatis) ▪​ Remnant of umbilical vein →​Paraumbilical veins G. OTHER STRUCTURES TENDINOUS INTERSECTIONS Figure 16. Other variations of Semilunar Line [Lecturer PPT] ​ The linea semilunaris was first described by Adriaan van den Spiegel which marks the transition between the muscle and aponeurosis in the transversus abdominis muscle. ​ This line is clinically significant because it delineates spigelian fascia. →​Defects in this fascia whether it is congenital or acquired can lead to spigelian hernia which is characterized by protrusion of the peritoneal sac of an organ or peritoneal fat. ​ Other sources may indicate that the linea semilunaris is considered synonymous with the lateral border of the rectus abdominis muscle. Figure 14. Tendinous intersection[Lecturer PPT] (SPACE LEFT INTENTIONALLY BLANK) ​ Transverse fibrous bands which creates a surface anatomy landmark ​ These semilunar skin grooves (5-8 cm from the midline) are clinically important because they are parallel with the lateral edges of the rectus sheath providing important clinical reference point ANATOMY Abdomen in General Page 7 of 20  📣 Good to Know ARTERIAL SUPPLY OF THE ANTEROLATERAL ABDOMINAL WALL Figure 17. EIT Ambivium, Linea Semilunaris, and Fulcrum Abdominalis [Lecturer PPT] ​ Anatomical studies suggest that these structures are not always precisely aligned. →​The study proposes alternative concepts such as ▪​ EIT ambivium or defined in the study as the lateral border of the rectus sheath ▪​ Fulcrum abdominals which is defined as the termination of the posterior rectus sheath at the 📣 linea Arcuata. However, for the purpose of this discussion, we will still Figure 19. Arterial supply of the anterolateral abdominal wall 📣 adhere to the traditional definition described by Moore This discrepancy highlights the dynamic nature of the [Lecturer PPT] ​ Superior Epigastric Artery 📣 anatomic knowledge even in seemingly fields This newer findings may or may not be incorporated into the future anatomical text →​Internal thoracic artery →​Enters the rectus sheath superiorly →​Supplies the superior part of the rectus abdominis ​ Inferior epigastric artery H. ARTERIAL AND VENOUS SUPPLY OF THE →​External iliac artery ANTEROLATERAL ABDOMINAL WALL →​Supplies rectus abdominis muscle; deep abdominal wall of pubic and inferior umbilical regions ​ Posterior intercostal arteries and Subcostal →​10th and 11th intercostal space →​Subcostal ▪​ Contributes to the lateral and posterior aspect of the abdominal wall’s blood supply. Note: The table for Arteries of Anterolateral Abdominal Wall is under the appendix. Figure 18. Arterial and Venous Supply of the Anterolateral (SPACE LEFT INTENTIONALLY BLANK) abdominal wall [Lecturer PPT] ​ Superior Epigastric Vessels ​ Inferior Epigastric Vessels ​ 10th and 11th posterior intercostal vessels and anterior branches of the subcostal vessels. ANATOMY Abdomen in General Page 8 of 20  SUPERFICIAL VENOUS DRAINAGE OF THE ​ The blood in the umbilical area tries to find a collateral ANTEROLATERAL ABDOMINAL WALL pathway for the veins to return to the vena cava. Then eventually, to the right side of the heart. I. LYMPHATIC DRAINAGE OF THE ANTEROLATERAL ABDOMINAL WALL Figure 20. Superficial Venous drainage of the anterolateral abdominal wall [Lecturer PPT] Table 3. Superficial venous drainage of the anterolateral abdominal wall Location Drainage Medial Internal thoracic vein → brachiocephalic vein → SVC Lateral Lateral thoracic vein → axillary vein → subclavian vein → SVC Inferior Superficial epigastric vein Figure 22. Lymphatic drainage of the anterolateral abdominal (draining to the femoral vein) wall [Lecturer PPT] → external iliac vein → ​ Superficial lymphatic vessels common iliac → IVC →​Superior to the umbilical plane: ▪​ Axillary lymph nodes Inferior epigastric veins ▪​ Parasternal lymph nodes (drains into iliac vein) → →​Inferior to the umbilical plane: common iliac → IVC ▪​ Superficial inguinal lymph nodes Umbilical Area Cutaneous veins in the ​ Deep lymphatic vessels umbilicus → Paraumbilical →​Accompany the deep veins of the abdominal walls; drain to the 📣 vein → hepatic portal vein This connection along with the potential anastomosis via thoracoepigastric vein between the superficial epigastric and ▪​ External iliac ▪​ Common iliac ▪​ Right and left lumbar (caval and aortic) lymph nodes lateral thoracic vein is a clinical significance which are position along the inferior vena cava and 📣 Clinical Significance aorta (SPACE LEFT INTENTIONALLY BLANK) Figure 21. Tortuous superficial vein [Lecturer PPT] ​ The picture is from a patient with increased portal hypertension such as in liver cirrhosis ​ This picture shows caput medusae ANATOMY Abdomen in General Page 9 of 20  J. DERMATOMES OF THE ANTEROLATERAL ​ The McBurney point is the most common site of maximum ABDOMINAL WALL tenderness in acute appendicitis ​ The oblique McBurney incision is made at the McBurney point, approximately 2.5 cm superomedial to the ASIS on the spino-umbilical line ​ This precise anatomic reference guides both clinical examination and surgical approach ABDOMINAL HERNIAS Figure 23. Dermatomes of anterolateral abdominal wall [Lecturer’s PPT] ​ Mirror peripheral nerve distribution (T7-T12) →​These nerves do not form plexuses ​ Each dermatome follows rib contour from posterior Figure 25. Abdominal Hernias [Lecturer’s PPT] intervertebral foramen. ​ Key landmarks: ​ Commonly develop at structural weak points in the →​T10 dermatome: umbilicus anterolateral abdominal wall particularly where the vessels →​L1 dermatome: inguinal fold or other structures penetrate the wall ​ Common Sites of Weakness: K. NERVE SUPPLY OF THE ANTEROLATERAL →​Inguinal region ABDOMINAL WALL →​Umbilical region 1.​Thoraco-abdominal nerves (T7-T11) →​Epigastric region 2.​Lateral cutaneous branches (T7-T10) TYPES OF HERNIAS 3.​Subcostal nerve (T12) 4.​Iliohypogastric and ilio-inguinal nerves (L1) 1. Umbilical Hernias: ***See Table 9 in the appendix ​ Neonatal: Incomplete umbilical ring closure ​ Acquired: Common in women and obesity ​ Note: T10 supplies the umbilicus 2. Epigastric Hernias: ​ Location: Linea alba between xiphoid process and L. CLINICAL CORRELATION OF THE ANTEROLATERAL umbilicus ABDOMINAL WALL ​ Characteristic: Usually fatty tissue protrusion MCBURNEY POINT ​ Often painful due to nerve compression 3. Spigelian Hernias: ​ Location: Along semilunar lines ​ Demographics: Age >40, often with obesity ​ Composition: Peritoneal sac with variable muscle coverage V. INGUINAL REGION Figure 26. Formations of Inguinal Region [Moore] Figure 24. McBurney Point[Moore] ​ Extends between the ASIS and pubic tubercle ANATOMY Abdomen in General Page 10 of 20  ​ Anatomically: major passageway where structures exit and Figure 28. Iliopubic tract [Netter] enter the abdominal cavity C. INGUINAL CANAL A. INGUINAL LIGAMENT ​ In adults, it is an oblique passage, approx. 4 cm long ​ AKA Poupart’s ligament ​ Directed inferomedially through the inferior part of the ​ Dense band constituting the most inferior part of the external oblique aponeurosis ​ ASIS to Pubic tubercle (mostly medial end), extends ​ Structures transmitted: →​Male: Spermatic cord​ ❗️ anterolateral abdominal wall beyond its primary insertion contributing fibers to: →​Females: Round ligament of the uterus →​Lacunar ligament (of Gimbernat) ​ Two distinct openings ▪​ Deeper fibers pass posteriorly to attach to the →​Deep (internal) inguinal ring superior pubic ramus lateral to the tubercle, forming →​Superficial (external) inguinal ring the arching fibers → forms the medial boundary of ▪​ Lateral crus the subinguinal space ▪​ Medial crus →​Pectineal ligament (of Cooper) ▪​ Intercrural fibers ▪​ Most lateral of fibers continue to run along the pecten pubis Table 4. Openings of Inguinal Canal Deep Inguinal Ring ❗️ Superficial Inguinal Ring →​Reflected inguinal ligament ▪​ Superior fibers fan upward, bypassing the pubic ​ Entrance to inguinal ​ Exit of inguinal canal tubercle and crossing the linea alba to blend with the canal ​ Location: lower fibers of the contralateral external oblique ​ Location: →​Superolateral to the aponeurosis →​Superior to midpoint pubic tubercle of the inguinal ​ Slit-like opening in the ligament external oblique →​Lateral to the inferior aponeurosis featuring: epigastric artery →​Lateral crus: attaches ​ Represents an to pubic tubercle evagination in the →​Medial crus: attaches transversalis fascia to pubic crest allowing passage of →​Intercrural fibers: ductus deferens and running perpendicular testicular vessels (in to the aponeurosis males) or round connects these crura ligament of uterus (in and prevents females), along with the excessive widening of genitofemoral nerve the opening Figure 27. Inguinal ligament [Netter] Table 5. Boundaries of the Inguinal Canal Lateral ❗️ Medial B. ILIOPUBIC TRACT Middle Boundary Third/Deep Third/Superficial ​ Thickened inferior margin of the transversalis fascia Third Ring Ring ​ Fibrous band running parallel and posterior (deep) to the Posterior Transversalis fascia Inguinal falx inguinal ligament Wall (conjoint ​ Reinforces the posterior wall and floor of the inguinal canal tendon) plus as it bridges the structures traversing the subinguinal reflected space inguinal ​ Both inguinal ligament and iliopubic tract provide a central ligament strength at the myopectineal orifice Anterior Internal Aponeurosis Aponeurosis of Wall oblique plus of external external oblique →​Weak area lateral crus of oblique (lateral (intercrural →​Site of direct and indirect inguinal and femoral hernias aponeurosis of crus and fibers), with →​Provide central strength to an area of innate weakness external intercrural fascia of in the body wall in the inguinal region oblique fibers) external oblique continuing onto cord as external spermatic fascia Roof Transversalis Musculo-apon Medial crus of fascia eurotic arches aponeurosis of of internal external oblique oblique and transverse abdominal Floor Iliopubic tract Inguinal Lacunar ligament ligament ANATOMY Abdomen in General Page 11 of 20  MALE DEVELOPMENT OF THE INGUINAL CANAL FEMALE DEVELOPMENT OF THE INGUINAL CANAL Figure 30. Formation of inguinal canals in females[Moore] ​ Inguinal development initially parallels with male development →​Ovaries originate from the superior lumbar region →​Processes diverge as ovaries descend only to the lateral pelvic wall structures❗️ →​Female gubernaculum differentiates into two distinct ▪​ Ovarian ligament - connects the ovary to the uterus ▪​ Round ligament - extends from the uterus through the inguinal canal and to the labium majus (singular) / labia majora (plural) KEY DIFFERENCES FROM MALE DEVELOPMENT ​ Female processus vaginalis typically obliterates by 6th fetal month ​ Inguinal canals are characteristically narrower than the male counterpart Figure 29. Formation of inguinal canals and relocation of ​ Ovaries remain in pelvis due to uterine attachment testes[Moore] INFANT vs ADULT DEVELOPMENT IN BOTH SEXES ​ Development Timeline ​ Infant inguinal canals are shorter, less oblique, and more →​Week 7: Testes develop in superior lumbar region direct than adult canals (connected to the future deep inguinal ring by ​ Superficial rings are positioned almost directly anterior to gubernaculum) the deep rings →​Week 12: Testes descend to pelvis →​Week 28: Testes reach deep inguinal ring days) ❗️ →​Week 28-29: Crucial passage through inguinal canal (~3 →​Week 32: Testes enter scrotum ​ Key Structures​ deep ring ❗️ →​Gubernaculum: Fibrous tract connecting testis to future →​Processus Vaginalis: Peritoneal diverticulum through (SPACE LEFT INTENTIONALLY BLANK) developing canal; creates a pathway through the developing abdominal wall →​Musculofascial Extensions: form internal/external spermatic fasciae (protective layer of the spermatic cord) →​Tunica Vaginalis: forms from distal processus vaginalis ANATOMY Abdomen in General Page 12 of 20  SPERMATIC CORD Table 6. Corresponding layers of anterior abdominal wall, scrotum, and spermatic cord Scrotum and Layers of Anterior Spermatic covering of Abdominal Wall Cord Testis Skin - Skin Subcutaneous tissue Dartos fascia and Dartos fascia and fatty and membranous dartos muscle dartos muscle (Camper and Scarpa) External oblique and External External fascia spermatic fascia spermatic fascia Internal oblique Cremaster muscle Cremaster muscle muscle Fascia of both Cremaster muscle Cremaster superficial and deep muscle surfaces of the internal oblique muscle Transversus - - abdominis muscle Transversalis fascia Internal spermatic Internal spermatic fascia fascia Peritoneum Vestige tunica Tunica vaginalis vaginalis VI. POSTERIOR ABDOMINAL WALL A. COMPONENTS Figure 31. Inguinal canal and spermatic cord[Moore] ​ Anatomical Course →​Begins: Deep inguinal ring (lateral to inferior epigastric vessels) →​Traverses: Inguinal canal →​Exits: Superficial inguinal ring →​Ends: Posterior border of testis ​ Structure provides a vital connection between the abdominal cavity and testis ​ Contents 1.​ Ductus deferens (vas deferens) 2.​ Testicular artery 3.​ Artery of ductus deferens 4.​ Cremasteric artery 5.​ Pampiniform venous plexus 6.​ Sympathetic nerve fibers on arteries and the ductus Figure 31. Fascia and aponeurosis of abdominal wall at level of renal hila deferens (inferior view and transverse section)[Moore] 7.​ Genital branch of the genitofemoral nerve → ​ Central elements supplying the cremaster muscle →​Five lumbar vertebrae 8.​ Lymphatic vessels →​Intervertebral discs 9.​ Vestige of processus vaginalis →​Prominent vertebral column creating paravertebral gutters (house the kidneys and surrounding fat) ​ Muscular components →​Psoas muscle →​Quadratus lumborum →​Iliacus →​Transversus abdominis (posterior portion) →​Oblique muscles ​ Supporting structures →​Superior component ▪​ Diaphragm →​Connective elements ▪​ Thoracolumbar fascia (provides support) ▪​ Retroperitoneal fat ​ Neurovascular elements →​Neural components ▪​ Lumbar plexus (formed by lumbar spinal nerves) ▪​ Anterior rami of lumbar nerves →​Vascular structures ▪​ Abdominal aorta (runs anteriorly to the vertebral column close to the anterior abdominal wall) Figure 32. Corresponding layers of anterior abdominal wall, ▪​ Inferior vena cava scrotum, and spermatic cord ▪​ Lymph nodes ANATOMY Abdomen in General Page 13 of 20  B. FASCIA LAYER OF THE POSTERIOR C. POSTERIOR ABDOMINAL WALL MUSCLES ENDOABDOMINAL WALL Figure 33. Muscles of the posterior abdominal wallMoore] ​ Psoas major (Muscle of the Loin) →​Long fusiform muscle →​Location: Extends from lateral to lumbar vertebrae Figure 32. Fascia and aponeurosis of abdominal wall at level →​Course: Inferolaterally beneath the inguinal ligament of renal hila (transverse section and posterolateral view)[Moore] and inserts to the lesser trochanter of the femur ​ Endoabdominal fascia →​Key feature: Houses the lumbar plexus posteriorly (key →​Creates a continuous sheath between the parietal consideration in nerve entrapment syndromes) peritoneum and the muscles →​Uniquely affects the lumbar vertebral movement through →​Named by structure it covers flexion and lateral bending →​Continuous with transversalis fascia of the anterior ​ Iliacus abdominal wall →​Shape: Large, triangular ​ Psoas fascia →​Position: Lateral to inferior psoas major →​Forms a distinct sheath around the psoas major muscle →​Forms iliopsoas complex with psoas major →​Attachments ▪​ Primary hip flexor ▪​ Medial: Lumbar vertebrae, pelvic brim ▪​ Hip joint stabilizer ▪​ Superior: Thickens to form medial arcuate ligament ▪​ Maintains erect posture ▪​ Lateral: Fuses with quadratus lumborum muscle and ​ Quadratus lumborum thoracolumbar fascia →​Shape: Quadrilateral, broad inferiorly ▪​ Inferior: Continues as iliac fascia covering the iliacus →​Location: Adjacent to lumbar transverse processes muscle below the iliac crest →​Relations: ​ Thoracolumbar fascia ▪​ Crossed by lateral arcuate ligament near the 12th rib →​Three layers (creates a pathway for the subcostal nerve that ▪​ Posterior layer: thick and strong passes posterior to this landmark) ▪​ Middle layer: encloses the erector spinae muscles ▪​ Anterior to subcostal nerve ▪​ Anterior layer: thinner and more transparent ▪​ Anterior surface provides a course for branches of ○​ Quadratus lumborum fascia the lumbar plexus →​Key features ▪​ Thin in thoracic region D. NERVE SUPPLY OF POSTERIOR ABDOMINAL ▪​ Thick in lumbar region (significant as it creates a WALL strong posterior compartment) ▪​ Encloses erector spinae muscles ▪​ Attaches to vertebral column medially →​Anterior layer characteristics ▪​ Covers quadratus lumborum ▪​ Attaches to transverse processes ▪​ Forms lateral arcuate ligament superiorly ▪​ Connects to iliolumbar ligaments inferiorly Figure 34. Muscles and nerves of the posterior abdominal wall Moore] ​ Somatic innervation →​Subcostal nerve (T12) ▪​ Course: Enter the abdomen posterior to the lateral (SPACE LEFT INTENTIONALLY BLANK) arcuate ligament ▪​ Supply: Anterolateral abdominal wall, and external oblique muscle →​Lumbar plexus (L1-L5) - forms within the psoas major ▪​ Major branches ○​ Femoral nerve (L2-L4) ○​ Obturator nerve (L2-L4) ○​ Lumbosacral trunk (L4-L5) ANATOMY Abdomen in General Page 14 of 20  ▪​ Minor branches Table 6. Branches of the Abdominal aorta[Lecturer’s PPT] ○​ Iliohypogastric/Ilioinguinal (L1) ○​ Genitofemoral (L1-L2) ○​ Lateral femoral cutaneous (L2-L3) ​ Autonomic components →​Lumbar sympathetic trunks ▪​ Contains four ganglia and continues from the thoracic region ▪​ Location: Anterolateral to vertebral bodies ▪​ Connections and sympathetic innervations that affect both visceral and somatic structures through: ○​ White communicating branches (L1-L3) ○​ Gray communicating branches ○​ Lumbar splanchnic nerves F.VENOUS DRAINAGE OF POSTERIOR ABDOMINAL E. ARTERIAL SUPPLY OF POSTERIOR ABDOMINAL WALL WALL Figure 35. Branches of the Abdominal aorta[Moore] ​ Abdominal aorta → Location and Course: ○​ Length:13 cm ○​ Begins at the aortic hiatus in the diaphragm at the level of T12 vertebra and ends at the level of the L4 vertebra by dividing into the right and left Figure 36. Inferior Vena Cava[Moore] common iliac arteries ○​ Surface marking: 2.5 cm above transpyloric plane ​ Inferior vena cava to left of umbilicus → Characteristics: → Important Relations ○​ Largest vein in body ○​ Anterior ○​ No functional valves - Celiac plexus ○​ Length exceeds aorta by 7 cm - Pancreas and splenic vein → Course: - Horizontal duodenum ○​ Formation: L5 (Common iliac union) - Small intestine ○​ Position: 2.5 cm right of midline ○​ Lateral ○​ Termination: Caval opening (T8) - Right: Azygos vein, Cisterna chyli → Tributaries: - Left: Left crus of diaphragm ○​ Paired Visceral: →Arterial Branches - Right suprarenal vein ○​ Common Iliac Arteries: - Renal veins - Course: Along psoas border - Right gonadal vein - Division: Internal and external iliac ○​ Paired Parietal: ○​ Branch Classification - Inferior phrenic veins - Visceral (paired/unpaired) - L3 & L4 lumbar veins - Parietal (paired/unpaired) - Common iliac veins - Arranged in three vascular planes (SPACE LEFT INTENTIONALLY BLANK) ANATOMY Abdomen in General Page 15 of 20  G. LYMPHATIC SYSTEM OF POSTERIOR ABDOMINAL VISCERAL PERITONEUM WALL ​ Organ Investment ​ Sensory profile →​Insensitive to: Touch, Temperature, Laceration →​Responsive to: Stretch, chemical irritation →​Shared blood supply with underlying organs →​Visceral nerve innervation pattern ​ Embryological pain distribution: →​Foregut → Epigastric →​Midgut → Periumbilical →​Hindgut → Suprapubic PERITONEAL RELATIONSHIPS WITH ORGANS ​ Intraperitoneal Organs: Almost complete peritoneal coverage →​Examples: stomach, spleen →​Analogous to fist pressing into balloon ​ Extraperitoneal Organs: Partial peritoneal coverage →​Lies externally to parietal peritoneum and receives only partial peritoneal coverage →​Includes: retroperitoneal, subperitoneal organs →​Examples: ▪​ Retroperitoneal: kidneys (anterior coverage only) Figure 35. Nerves of the Posterior Abdominal Wall[Moore] ▪​ Subperitoneal: bladder (superior coverage only) B.​ PERITONEAL CAVITY ​ Lymph node groups ​ Characteristics: → Major Node Chains: →​Potential space between peritoneal layers ○​ Common Iliac Nodes →​Contains peritoneal layers ○​ Lumbar (caval/ aortic nodes) →​No organs within cavity itself ○​ Pre- aortic nodes ​ Peritoneal Fluid Functions: ​ Lymphatic Drainage Pattern → Lubrication for visceral movement → Visceral Drainage → Contains immune components ○​ Alimentary tract⇾ Pre-aortic nodes → Absorbed by diaphragmatic lymphatics ○​ Kidneys/Reproductive organs⇾ Lumbar nodes ​ Gender Differences → Convergence Points → Males: Completely closed system ○​ Right/ left lumbar trunks → Females: Communication pathway ○​ Intestinal lymphatic trunks ▪​ External communication pathway ○​ Thoracic lymphatic trunks ○​ Route: uterine tubes → uterus → vagina ​ Thoracic Duct ○​ Clinical significance: potential infection route → Formation: L1-L2 level → Components: C.​ EMBRYOLOGY ○​ Lumbar lymphatic trunks PERITONEAL CAVITY ○​ Intestinal trunks ○​ Descending thoracic trunks Table 6. Peritoneal Formations Peritoneal VII. PERITONEUM AND PERITONEAL CAVITY Definition Example Formation A.​ PERITONEUM: STRUCTURE AND FUNCTION Mesentery Double layer Small Intestine Mesentery ​ Continuous serous membrane system connecting ​ Transverse mesocolon ​ Composition: Simple Squamous mesothelium organs to body ​ Sigmoid mesocolon ​ Key characteristics: Transparent, glistening slippery wall with ​ Mesoappendix ​ Continuous serous membrane system neurovascular ​ Mesoesophagus ​ Two main components: supply → Parietal peritoneum (lines abdominopelvic wall) Omentum Peritoneal Greater Omentum → Visceral peritoneum (covers organs) extension from ​ Hangs like apron from stomach/ greater curvature PARIETAL PERITONEUM duodenum ​ 4-layered fold​ ​ Lines abdominopelvic cavity ​ Shares wall’s vasculature and innervation Lesser Omentum ​ Sensitive to multiple stimuli: ​ Connects lesser →​Pressure, pain, etc. curvature to liver ​ Clinical Significance: Pain Localization Peritoneal Double layer Falciform Ligament →​Parietal: Well-localized Ligament connecting Hepatogastric Ligament →​Visceral: Poorly localized, follows embryological organ-to-organ Hepatoduodenal Ligament patterns or organ-to-wall ​ Special considerations Stomach Connections →​Diaphragmatic irritation → shoulder pain (C3-C5) ​ Gastrophrenic ligament ANATOMY Abdomen in General Page 16 of 20  ​ Gastrosplenic ligament ​ Herniation into umbilical cord ​ Gastrocolic ligament ​ Maintained by omphalo-enteric duct SUBDIVISIONS OF PERITONEAL CAVITY ​ Initial 90° rotation begins ​ Major Peritoneal Subdivisions Phase 2: Rotation ​ Primary rotation: 270° ​ Two Main Compartments: Period (Week 6-10) counterclockwise →​Greater Sac (Main peritoneal cavity): accessible ​ Superior Mesenteric Artery as through routine abdominal surgery represents the main rotation axis peritoneal cavity ​ Sequential movement of →​Lesser Sac (Omental bursa): lies posterior to the intestinal segment stomach and lesser omentum creating a unique surgical ​ Development of mesenteric space attachments COMPARTMENTAL ORGANIZATIONS Phase 3: Return to ​ Reduction of liver/kidney ​ Supracolic Compartment Abdomen (Weeks relative size →​Location: Above transverse mesocolon 10-12) ​ Completion of remaining 180° →​Contains: Stomach, liver, spleen rotation ​ Infracolic Compartment ​ Establishment of final organ →​Location: Below transverse mesocolon positions →​Contains: Small intestine, ascending/descending colon ​ Development of ​ Divided into right and left spaces by small intestine retroperitoneal attachments mesentery OMENTAL BURSA (LESSER SAC) ​ Location: Posterior to stomach ​ Key components: →​Superior recess (beneath diaphragm) →​Inferior recess (within greater omentum) ​ Facilitates stomach mobility through smooth sliding of the bursa walls which provides the sole communication between the greater and lesser sac. OMENTAL FORAMEN ​ Function: Connected greater and lesser sacs ​ Boundaries: →​Anterior: Hepatoduodenal ligament →​Posterior: IVC and right diaphragmatic crus →​Superior: Liver →​Inferior: First part of duodenum ​ Clinical significance →​Paracolic gutters: Allow fluid communication →​Right side: more free flow →​Important in spread of pathological processes →​Essential for clinicians to identify the fluid movement through paracolic cutters which shows preferential flow on the right side EMBRYOLOGICAL FOUNDATIONS ​ Primitive Gut Division: Figure 37. Embryological Foundations[Lecturer’s PPT] →​Foregut: Proximal to ampulla of Vater →​Midgut: Post-ampullary to mid-transverse colon →​Hindgut: Remainder of colon and rectum VIII. REVIEW QUESTIONS PAIN DISTRIBUTION BY EMBRYOLOGICAL ORIGIN 1.​ Which of the following structures is contained within the medial umbilical ligament? ​ Foregut Pain (Epigastric): a.​ Urachus →​Structures: Esophagus, stomach, liver, proximal b.​ Umbilical arteries duodenum c.​ Inferior epigastric vessels →​Innervation: Vagal and sympathetic 2.​ What is the primary function of the linea alba in the ​ Midgut Pain (Periumbilical) anterior abdominal wall? →​Structures: Distal duodenum to proximal transverse a.​ It forms a boundary between the right and left rectus colon sheath compartments. →​Key organs: Small intestine, cecum, appendix b.​ It is the usual site where hernias occur. ​ Hindgut Pain (Hypogastric): c.​ It serves as the point of insertion for the rectus →​Structures: Distal transverse colon to rectum abdominis muscles. →​Clinical significance: colorectal pathology 3.​ Which of the following muscles does not originate Table 7. Developmental Sequence from the posterior aspect of the thoracolumbar Phase Events fascia? Phase 1: Initial ​ Rapid intestinal growth a.​ External oblique muscle Herniation (Week 4) exceeds abdominal capacity b.​ Internal Oblique muscle ANATOMY Abdomen in General Page 17 of 20  c.​ Transversus Abdominis muscle 4.​ Which of the following structures constitutes the FORMATIVE QUIZ deep inguinal ring? a.​ External oblique aponeurosis 1.​ The external or superficial inguinal rings is an b.​ Rectus abdominis muscle opening on the: c.​ Transversalis fascia a.​ Rectus Sheath 5.​ Which artery arises from the internal thoracic artery b.​ External Oblique Aponeurosis and descends within the rectus sheath? c.​ Internal Oblique Aponeurosis a.​ Musculophrenic artery d.​ Conjoint Tendon b.​ Superior epigastric artery 2.​ Which of the following structures forms the deeper c.​ Subcostal artery layer of the superficial fascia of the anterior d.​ Inferior epigastric artery abdominal wall and is continuous into the perineum with various fascial layers? a.​ Colles’ fascia ANSWER KEY b.​ Gallaudets’ fascia 1. B Medial umbilical folds cover the medial c.​ Camper’s fascia umbilical ligaments, formed by occluded parts d.​ Scarpa’s fascia of the umbilical arteries 3.​ Which of the following is a major intraperitoneal 2. A The linea alba is a fibrous structure running organ? along the midline of the anterior abdominal wall, a.​ Body of pancreas separating the left and right rectus sheath b.​ Duodenum, first part compartments. c.​ Ureter 3. A The external oblique muscle does not originate d.​ Descending colon from the thoracolumbar fascia. Instead, it 4.​ What forms the lateral border of the Hesselbach’s originates from the lower ribs and inserts into triangle? the iliac crest and the linea alba. a.​ Inferior epigastric vessels 4. C The deep inguinal ring is primarily formed by b.​ Inguinal ligament the transversalis fascia, a connective tissue c.​ Medial umbilical ligament layer that lines the posterior wall of the d.​ Deep inguinal ring abdominal cavity. This fascia creates the 5.​ Bony prominence or landmark of the anterior entrance to the inguinal canal, providing a abdominal wall which is the proximal attachment of passage for structures like the ductus deferens the inguinal ligament and testicular vessels in males or the round a.​ Iliac tubercle ligament of the uterus in females. b.​ Anterior superior iliac spine (ASIS) 5. B The superior epigastric artery is a branch of ICA c.​ Pubic tubercle that descends through the rectus sheath to ANS: 1) B, 2) D, 3) B, 4) A, 5) C supply the anterior abdominal wall and rectus abdominis. The musculophrenic artery, also IX. REFERENCES from the ICA, runs along the costal margin and ​ Moore, K.L., Dalley, A.F., Agur, A.M.R. (2018). Clinically Oriented supplies the diaphragm. The subcostal artery Anatomy (8th ed.). Wolters Kluwer originates from the abdominal aorta, while the ​ Sadler, T. W. (2019). Langman’s medical embryology (14th Ed.). inferior epigastric artery arises from the external Wolters Kluwer ​ Dr. Maganito. (2025). Abdomen in General, Posterior Abdominal iliac artery. Wall, and Peritoneum & Embryology Video Lecture ANATOMY Abdomen in General Page 18 of 20  X. APPENDIX Table 8. Arteries of the Anterolateral Abdominal Wall Table 9. Muscles of the Anterolateral Abdominal Wall ANATOMY Abdomen in General Page 19 of 20  Table 10. Nerves of Anterolateral Abdominal Wall Table 11. Muscles of Posterior Abdominal Wall ANATOMY Abdomen in General Page 20 of 20