Gross Anatomy of the Anterior Abdominal Wall Part 2 PDF

Module 08: Gastrointestinal System and Nutrition 1 Gross Anatomy of the Anterior Abdominal Wall Part 2 Michele Rivera-Nuez, MD, FPCS, FPAPRAS | January 15, 2024 | Asynchronous TABLE OF CONTENTS A. THREE...

Module 08: Gastrointestinal System and Nutrition 1 Gross Anatomy of the Anterior Abdominal Wall Part 2 Michele Rivera-Nuez, MD, FPCS, FPAPRAS | January 15, 2024 | Asynchronous TABLE OF CONTENTS A. THREE FLAT MUSCLES External Oblique Muscles Learning Objectives 1 VII. Venous Drainage of 9 I. Muscles of the 1 Anterolateral Abdominal Largest and most superficial among the three flat muscles Anterolateral Wall 1 Wall Immediately deep to the superficial fascia A. Three Flat Muscles 1 A. Superficial Venous 9 Direction of muscle fibers: inferiorly and medially B. Two Vertical Muscles 4 Drainage Muscle fibers become aponeurotic at the level of the C. Functions of the 5 B. Deep Venous Drainage 9 midclavicular line Anterolateral Wall C. Cutaneous 10 ▪ This forms a sheath of tendinous fiber that crosses the Muscles Paraumbilical Veins II. Transversalis Fascia 5 VIII. Lymphatic Drainage 10 midline at the linea alba III. Extraperitoneal Fascia 6 A. Superficial Abdominal 10 IV. Peritoneum 6 Lymphatic Vessels V. Aponeuroses and Deep 6 B. Deep Abdominal 10 Fascia Lymphatic Vessels A. Aponeuroses 6 IX. Nerves of the 10 B. Linea Alba 6 Anterolateral Abdominal C. Linea Semilunaris 7 Wall D. Rectus Sheath 7 A. Innervation 10 VI. Blood Supply of the 8 Summary & Keypoints 11 Anterolateral Wall Review Questions 11 A. Primary Blood Vessels 8 Rationale 12 References 12 LEARNING OBJECTIVES 1. Describe the bony and cartilaginous landmarks visible or palpable on abdominal examination and explain their clinical significance. 2. Describe the different abdominal planes and its anatomical Figure 1. External Oblique Muscle correlates. 3. Describe the descriptive regions and quadrants of the abdomen. Intermuscular exchange occurs between the aponeuroses of 4. Describe the surface projections of the abdominal organs onto contralateral external and internal oblique muscles the four quadrants and nine descriptive regions of the abdomen. – Right and left external oblique muscles become continuous 5. Describe the surface projections of the liver, gallbladder, with the tendinous fibers of the contralateral internal oblique pancreas, spleen, kidneys, stomach, duodenum, jejunum, ileum, muscle caecum, appendix, ascending, transverse, descending, and – The muscular fibers decussate sigmoid parts of the colon. 6. Understand the layers of the anterior abdominal wall. 7. Describe the anatomy, innervation, and functions of the muscles of the anterior abdominal wall. 8. Describe the different aponeuroses of the anterior abdominal wall. 9. Identify blood supply and lymphatic of anterior abdominal wall. 10. Identify the umbilical folds/ligaments and their relative structures. I. MUSCLES OF THE ANTEROLATERAL WALL Three flat muscles – External Oblique Muscles – Internal Oblique Muscles Figure 2. Diagrammatic Representation of the External Oblique – Transversus Abdominis Origin Two vertical muscles – External surfaces of the 5th to 12th ribs – Rectus Abdominis – Pyramidalis TG7 | Berdin, de Jesus, Gerodias, Go, Hernandez, Lengwa, Malabuyoc, Martinez, Perfecto, Tan, Tinawin, Valarao YL5 08.01b 1 of 12 CG16 | Cabatbat, Cruz, Hocbo, Gaditano, Martinez, Milla, Mungkal, Santos, Tan, Teves, Tiu  ▪ Subcostal nerve (T12) – Sensory ▪ Iliohypogastric nerve from L1 Figure 3. Origin of the External Oblique (cadaveric model) Figure 7. Innervation of External Oblique Muscles Insertions Actions – Thoracolumbar fascia – Bilateral contraction – Linea alba ▪ Trunk flexion – Pubic tubercle ▪ Abdominal viscera compression – Anterior half of Iliac crest ▪ Expiration – Unilateral contraction ▪ Trunk lateral flexion (ipsilateral) ▪ Trunk Rotation (contralateral) Blood Supply – Lower posterior intercostal arteries – Subcostal arteries – Deep circumflex iliac artery Figure 4. Insertions of the External Oblique (cadaveric model) Figure 5. Diagrammatic representation of the Origin and Insertion of the External Oblique Figure 8. Blood Supply of External Oblique Muscles Inguinal Ligament The aponeurosis of the external oblique muscle forms the inguinal ligament and part of the inguinal canal – Found at the lower border of the external oblique muscle – The thickened, reinforced edge of the aponeurosis passes between the anterior superior iliac spine and the pubic tubercle ▪ This folds under itself, forming a trough ▪ Plays a role in the formation of the inguinal canal Figure 6. External Oblique (cadaveric model) detached from its origin Innervation – Motor ▪ Intercostal nerves (T7–T11) YL5 08.01b Gross Anatomy of the Anterior Abdominal Wall Part 2 2 of 12  Figure 9. Lower Border of External Oblique Muscles (cadaveric model) Figure 13. Internal Oblique Muscle (Behind External Oblique Muscle) Detached from Its Origin (cadaveric model) Internal Oblique Muscles – Insertion ▪ Inferior border of the 10th to 12th ribs ▪ Linea alba ▪ Pecten pubis through the conjoint tendon Figure 14. Insertion of the Internal Oblique Muscle (cadaveric model) Figure 10. Internal Oblique Muscles (cadaveric model) – Motor innervation (see Figure 7) Intermediate muscle of the three flat muscles ▪ Intercostal nerves (T7-T11) Direction of muscular fibers ▪ Subcostal nerve (T12) – Anteromedially, or forward and towards the middle ▪ Iliohypogastric nerve (L1) – Runs perpendicular to the external oblique muscle ▪ Ilioinguinal nerve (L1) Origin – Action – Thoracolumbar fascia ▪ Bilateral action – Anterior 2/3 of the iliac crest − Trunk flexion – Connective tissue deep to the lateral 1/3 of the inguinal − Compress abdominal viscera ligament − Expiration ▪ Unilateral action − Trunk lateral flexion (ipsilateral) − Trunk rotation (ipsilateral) o Differentiating action between internal and external oblique muscle – Blood supply ▪ Lower posterior intercostal arteries ▪ Subcostal artery ▪ Superior and inferior epigastric arteries ▪ Superficial and deep circumflex arteries ▪ Posterior lumbar arteries Figure 11. Origin of the Internal Oblique Muscle Figure 12. Origins of the Internal Oblique Muscles (cadaveric model) Figure 15. Blood Supply of the Internal Oblique Muscles ‘ YL5 08.01b Gross Anatomy of the Anterior Abdominal Wall Part 2 3 of 12  Transversus Abdominis Innermost of the three flat muscles – Found deep (at the back) of the internal oblique muscle Named after the direction of the muscle fibers, which is transverse – Its transverse circumferential orientation is ideal for: ▪ Compression abdominal content ▪ Encasing intra-abdominal pressure Continuous together superiorly with the transversus thoracis muscle Ends in the midline of the anterior aponeurosis, where it blends at the linea alba Figure 18. Neurovascular plane of the anterolateral abdominal wall ACTIVE RECALL BOX 1. The following are differentiating factors between the external and internal oblique muscles, except: a. Direction of the muscle fibers b. Motor innervation c. Bilateral action d. Unilateral action 2. All three flat muscles originate from the thoracolumbar fascia a. True b. False Figure 16. Transversus Abdominis Muscle and Its Insertions Answers: 1C, 2F B. TWO VERTICAL MUSCLES Rectus Abdominis Paired vertical muscle Most anterior abdominal muscle Divided into segments by tendinous intersections – Serve as attachment sites for the abdominis muscle to the overlying sheath (T11.01, 2025) Figure 17. Transversus Abdominis Muscle and Its Origins (cadaver model) Origin – Internal surface of the 7th-12th costal cartilages – Thoracolumbar fascia – Iliac crest – Connective tissue deep to the lateral third of the inguinal Figure 19. Rectus abdominis muscle (cadaveric model) with visible tendinous intersections ligament Insertion (see Figure 16) Covered by two tendinous aponeurotic sheaths: anterior and – Linea alba with aponeuroses of: posterior rectus sheath (T11.01, 2025) ▪ Internal oblique – Composed of the aponeuroses of the three flat muscles of the ▪ Pubic crest anterior abdominal wall ▪ Pecten pubis – Via conjoint tendon Neurovascular Plane – Located between the transversus abdominis and internal oblique muscle – Contains nerves and arteries supplying the anterolateral abdominal wall YL5 08.01b Gross Anatomy of the Anterior Abdominal Wall Part 2 4 of 12  C. FUNCTIONS OF THE ANTEROLATERAL WALL MUSCLES Maintenance of normal physiological functions To keep the abdominal viscera within the abdominal cavity To protect the viscera from injury To help maintain the position of the viscera in the erect posture against the action of gravity II. TRANSVERSALIS FASCIA Deep to the transversus abdominis muscle – Located between the inner surface of the transversus abdominis muscle and parietal peritoneum Figure 20. Rectus abdominis muscle (cadaveric model) with the anterior wall of the rectus sheath opened through a vertical incision Figure 23. Transversalis fascia Thin aponeurotic membrane that forms part of the general layer of fascia lining the abdominal walls Directly continuous with: – Iliac fascia – Internal spermatic fascia – Pelvic fascia Figure 21. Rectus abdominis muscle (cadaveric model) with the anterior portion of the rectus sheath reflected laterally Origin (T09.01, 2026) – 5th to 7th costal cartilages Insertion (T09.01, 2026) – Pubic crest Actions (T09.01, 2026) – Active flexion ▪ Lumbar spine flexion – Static effect ▪ Keeps lumbar spine straight when the force of gravity tends to extend it Pyramidalis Paired triangular muscle Figure 24. Transversalis fascia (cadaveric model) Seen caudally or inferiorly to rectus abdominis (T11.01, 2025) Absent in ~20% of population Generally unremarkable except for the deep layers near the Tenses the linea alba (T11.01, 2025) transversus abdominis muscle which is better developed The transversalis fascia is seen below the arcuate line, which is the thickened portion of the posterior rectus sheath Figure 22. Pyramidalis muscle (cadaveric model) Figure 25. Arcuate line (cadaveric model) YL5 08.01b Gross Anatomy of the Anterior Abdominal Wall Part 2 5 of 12  Figure 26. Arcuate line Becomes the endopelvic fascia (a.k.a parietal pelvic fascia) – Particularly after attaching to the iliac crest and blending with the fascia that covers the muscles associated with the upper regions of pelvic bone Transversalis fascia is thickened and dense around the inguinal region Figure 28. Extraperitoneal fascia during surgical procedures In males, transverse fascia extends downwards as the internal In surgical procedures, dissections can be performed to access spermatic fascia the preperitoneal fascia, and from there, the retroperitoneal As it ascends to the diaphragm, the fascia becomes thinner organs can be reached from that space and blends with the fascia covering the under surface the IV. PERITONEUM diaphragm Visceral peritoneum - covering the reflects onto the abdominal – The thickness of the transversalis fascia depends on the area viscera, provides complete or partial covering III. EXTRAPERITONEAL FASCIA Parietal peritoneum - lines the walls Figure 27. Extraperitoneal fascia (diagram) A layer of connective tissue, also called the endoabdominal fascia Separates transversalis fascia from the peritoneum Highlighted in green in Figure 27 is the extraperitoneal fascia of the anterior abdomen Highlighted in blue (Figure 27) is the extraperitoneal fascia of the posterior abdominal wall Extraperitoneal fascia is more abundant in the posterior wall, especially around the kidneys Organs found behind the extraperitoneal fascia can be called retroperitoneal organs Fascia towards the anterior side of the body is described as Figure 29. Visceral (red/purple) and parietal (blue) peritoneum preperitoneal or properitoneal, because they are in front of the V. APONEUROSES AND DEEP FASCIA peritoneum. , A. APONEUROSES Sheaths of pearly white fibrous tissue that takes the place of tendons in flat muscles Have a wide area of attachment Anterior abdominal aponeurosis is made up of the aponeuroses of the following flat muscles: – External oblique muscle – Internal oblique muscle – Transversus abdominis muscle YL5 08.01b Gross Anatomy of the Anterior Abdominal Wall Part 2 6 of 12  C. LINEA SEMILUNARIS Lateral to the rectus abdominis muscle on each side Paired and slightly curved vertical lines Represents the lateral border of the rectus sheaths Encloses the rectus abdominis muscle on both sides Figure 30. Aponeuroses (white cover-like layer) B. LINEA ALBA Anterior abdomen is characterized by the linea alba near the Figure 33. Lines of the Abdominal wall midline – Fusion of all the layers of the anterolateral wall muscles – Runs vertically from xiphoid process to pubic symphysis – The umbilicus is seen at its midline – Transmits small vessels and nerves to the skin – In thin muscular people, the groove is visible on the skin overlying the linea alba – Wider superiorly and narrows down as it goes to the pubic symphysis (see Figure 32) – In the umbilicus, the linea alba contains the umbilical ring ▪ Natural defect in the linea alba during fetal development Figure 34. Linea semilunaris in the gross specimen ▪ Where fetal umbilical vessels pass to and from the D. RECTUS SHEATH umbilical cord and the placenta Covering that encloses the rectus muscles – Anterior rectus sheath – Posterior rectus sheath Formed by unique layering of the aponeuroses of the external, internal and transversus abdominis muscles The opposite sides interweave and decussate (cross over) Figure 35. Anterior rectus sheath (L) and Posterior rectus sheath ® Figure 31. Linea alba Figure 36. Organization of the rectus sheath. A. Transverse section through the upper three-quarters of the rectus sheath. B. Transverse section through the lower one-quarter of the rectus sheath. Figure 32. Linea alba seen in the midline Arcuate line – Crescentic in shape YL5 08.01b Gross Anatomy of the Anterior Abdominal Wall Part 2 7 of 12  – Demarcates the transition between the aponeurotic posterior Take Note! border of the sheath – Demarcates the transition between the superior ¾ of your → Dr. Nuez mentioned in this segment that all three muscles rectus and the transversalis fascia covering the inferior ¼ contribute to the rectus sheath above the costal margin. → However, according to the diagram presented and other ▪ Superior ¾ - covered by posterior rectus sheath sources, only the external oblique muscle is involved (Moore, ▪ Posterior ¼ covered by transversalis fascia 2018; Vasković, 2023) → Instead, the diagram shows that the three flat muscles are simultaneously involved in the other three regions of the rectus (above arcuate line, below arcuate line, just above the pubis). Rectus Sheath above the Arcuate Line Presence of both anterior and posterior rectus sheaths Aponeurosis of internal oblique muscle splits into two layers: – Anterior rectus sheath ▪ Passes through anterior to the muscle of rectus abdominis ▪ Formed by anterior lamina joining the aponeurosis of the external oblique muscle – Posterior rectus sheath ▪ Passes posterior to the muscle of rectus abdominis ▪ Formed by posterior lamina joining the aponeurosis of the Figure 37. Arcuate line transversus abdominis muscle Rectus Sheath Formation Rectus can be arbitrarily divided into the following areas: – Above the costal margin – Above the arcuate line – Below the arcuate line Figure 40. Anterior and posterior rectus sheath (green) above the arcuate line – Just above the pubis Rectus Sheath below the Arcuate Line Approximately ⅓ of the distance from the umbilicus to the pubic crest Aponeurosis of all three flat muscles passes inferior to the rectus abdominis to form the anterior rectus sheath There is no posterior wall of rectus sheath – Only transversalis fascia lies behind the rectus abdominis muscle Figure 41. Aponeurosis of the rectus sheath (green) below the arcuate line Rectus Sheath just above the Pubis Figure 42. Aponeurosis of the rectus sheath (green) just above the pubis Figure 38. Contributions of abdominal wall muscles to rectus sheath Rectus Sheath Contents Rectus Sheath above the Costal Margin Superior and inferior epigastric arteries Superior and inferior epigastric veins Posterior layer is deficient Lymphatic vessels – This is because the transversus abdominis muscle continues Abdominal portions of anterior rami of spinal nerves T7-T12 superiorly as the transversus thoracis (no posterior rectus Distal portions of the thoraco-abdominal nerves sheath) The rectus abdominis lies directly on the thoracic wall above the costal margin Figure 39. Aponeurosis of the rectus sheath (green) above the costal margin All three flat muscles contribute to the formation of the anterior rectus sheath (Nuez, 2024) – There is no rectus sheath behind the rectus abdominis muscle above the costal margin YL5 08.01b Gross Anatomy of the Anterior Abdominal Wall Part 2 8 of 12  Superficial Vessels Superior part of the wall – Superior epigastric vessels ▪ Branches from the musculophrenic artery, a terminal branch of the internal thoracic artery Inferior part of the wall – Medially placed superficial epigastric artery – Laterally placed superficial circumflex iliac artery – Both branches of the femoral artery Figure 43. Vessel contents of the rectus sheath Figure 46. Superficial blood supply to the anterolateral wall Deep Vessels Figure 44. Nerve contents of the rectus sheath Superior part of the wall VI. BLOOD SUPPLY OF THE ANTEROLATERAL WALL – Superior epigastric artery A. PRIMARY BLOOD VESSELS ▪ A terminal branch of the internal thoracic artery Primary blood vessels: Lateral part of the wall – Superior epigastric vessels – Branches of the 10th and 11th intercostal arteries and the – Inferior epigastric and deep circumflex iliac subcostal artery – Superficial circumflex iliac and superficial epigastric Inferior part of the wall – Posterior intercostal vessels of the 11th intercostal space – Medially placed inferior epigastric artery – Anterior branches of subcostal vessels – Laterally placed deep circumflex iliac artery – Both are branches of the external iliac artery Figure 47. Deep blood supply to the anterolateral abdominal wall VII. VENOUS DRAINAGE OF ANTEROLATERAL ABDOMINAL WALL A. SUPERFICIAL VENOUS DRAINAGE Intricate subcutaneous venous plexus – For skin and subcutaneous tissue of the abdominal wall – Drains superiorly and inferiorly to the superior and inferior vena cava respectively Figure 45. Arterial supply to the anterolateral abdominal wall YL5 08.01b Gross Anatomy of the Anterior Abdominal Wall Part 2 9 of 12  ▪ The blood cannot drain back to the liver, so it finds an alternate pathway to go back to the heart Clinical Correlations: Caput Medusae → Results from Portal Hypertension a. Blood cannot drain back to the liver thus finds an alternative pathway that leads to the heart → Uncommon pathway is the Umbilical Vein a. Directs blood through the dilated superficial veins in the abdominal wall back to the heart. VIII. LYMPHATIC DRAINAGE A. SUPERFICIAL ABDOMINAL LYMPHATIC VESSELS. Superficial abdominal lymphatic vessels accompany the subcutaneous veins of the abdominal wall. – Above the umbilicus through ▪ Axillary Lymph Nodes ▪ Parasternal Lymph Nodes – Below the umbilicus through ▪ Superficial Inguinal Lymph Nodes Figure 48. Lymphatics and superficial veins of anterolateral abdominal wall (anterior view) B. DEEP VENOUS DRAINAGE Internal thoracic vein – Medially drains to the superior vena caval system Lateral thoracic vein – Laterally drains to the superior vena caval system Superficial epigastric veins – Drains to the inferior vena caval system Inferior epigastric veins – Drains to the inferior vena caval system Figure 50. Superficial lymphatics B. DEEP ABDOMINAL LYMPHATIC VESSELS Deep abdominal lymphatic vessels accompany deep veins of the abdominal wall – Drains to the following: ▪ External Illiac Lymph Nodes ▪ Common Iliac Lymph Nodes ▪ Right and Left Lumbar Nodes Figure 49. Lymphatics and deeper veins of anterolateral abdominal wall (anterior view, rib cage opened) C.CUTANEOUS PARAUMBILICAL VEINS Surrounds the umbilicus Figure 51. Deep abdominal lymphatics Anastomose with small tributaries of hepatic portal vein IX. NERVES OF THE ANTEROLATERAL ABDOMINAL WALL In cases of altered venous flow, anastomotic channels may exist A. INNERVATION or develop Nerve supply comes from T7-T12 – E.g., portal vein hypertension resulting in thoraco-epigastric – Thoraco Abdominal Nerve (T7 - T11) vein ▪ Anterior and Lateral Cutaneous Branches ▪ Thoraco-epigastric vein is formed by superficial epigastric – Lateral (Thoracic) Cutaneous Branches of the thoracic vein and lateral thoracic vein spinal nerves T7-T9 or T10 YL5 08.01b Gross Anatomy of the Anterior Abdominal Wall Part 2 10 of 12  – Subcostal Nerves (Anterior Ramus of T12) – Injury to the ilioinguinal nerve during dissection of the groin – Iliohypogastric Nerves area can manifest as numbness in medial thigh ▪ Superior Terminal branch of anterior ramus of spinal nerve SUMMARY AND KEYPOINTS L1 The muscles of the anterolateral wall can be divided into two: flat – Ilioinguinal Nerves (external oblique, internal oblique, and transversus abdominis) ▪ Inferior terminal branch of anterior ramus of spinal nerves and vertical muscles (rectus abdominis and pyramidalis). L1 Two fascia layers are found deep to the muscles: the transversalis and extraperitoneal fascia. Transversalis fascia is continuous with the iliac fascia, internal spermatic fascia, and pelvic fascia; becomes the endopelvic fascia; and extends as internal spermatic fascia in males. Its thickness depends on the area and may also be free or attached. While the extraperitoneal fascia is thicker in the posterior wall, near the kidneys. The last layer of the anterior abdominal wall is the peritoneum, which can be parietal or visceral. It is a descriptive landmark for the types of procedures done, whether preperitoneal/pro- peritoneal or retroperitoneal. Aponeuroses are tendons in flat muscles and the anterior abdominal aponeurosis is an example of that. Two lines lie on the vertical plane of the abdomen: linea alba and Figure 52. Dermatomal Innervation linea semilunaris. Linea alba is on the midline, while the linea Nerve T7-T12 and L1 supply skin, muscles, and underlying semilunaris is more lateral and marks the end of the rectus Parietal Peritoneum sheath. Linea alba is not only a fusion of the anterolateral wall Anterior Abdominal Wall follows a dermatomal distribution muscles, but also a transmitter of small neurovascular structures – Skin is supplied by a specific dermatome / spinal branch to the skin. At the midline of it is the umbilicus, which contains ▪ T7-T9 supply skin from xiphoid process to just above the the umbilical ring. umbilicus The rectus sheath encloses the rectus muscles and it has ▪ T10 supplies skin on the umbilicus anterior and posterior portions, which contain neurovascular ▪ T11-T12 and L1 supplies skin below the umbilicus structures as well as lymphatic vessels. It is made up of ▪ L1 branch (ilioinguinal) aponeuroses which interweave and cross the opposite side. It − Supplies anterior surface of scrotum and labia majora can be divided into three areas depending on their location, − Sens some cutaneous branches to the thighs which identifies their formation. An arcuate line can be found Thoraco-abdominal Nerve between the superior ¾ and inferior ¼ of the rectus muscle, – Run between the internal oblique and transversus abdominis marking the margins of their different coverings. muscle, within the neurovascular plane Arteries and veins supplying the anterolateral wall originate from – Supply abdominal skin and muscles and drain to various blood vessels both superficial and deep. Subcostal Nerve Anastomosis is the connection between blood vessels, while – Also known as spinal nerve T12 caput medusae is the dilation and engorgement of the vein – Runs along inferior border of the 12th rib, then passes into around the umbilicus. Both can form as a result of portal sub-umbilical abdominal wall between the 2nd and 3rd layers hypertension. of abdominal muscles (internal oblique and transversus Superficial abdominal lymph vessels accompany subcutaneous abdominis) veins, while deep abdominal lymph vessels accompany the deep – Innervates: veins. ▪ Muscles of anterolateral wall, including inferior-most slip of The anterolateral wall innervation follows a dermatomal external oblique distribution, with nerves originating from T7 to L1. ▪ Overlying skin superior to iliac crest and inferior to REVIEW QUESTIONS umbilicus #1: Which of the following is not an origin of transversus Iliohypogastric Nerve abdominis? – Originates as superior terminal branch of anterior ramus of A. Internal surface of 7th to 12th costal cartilages spinal nerve L1 B. Pubic crest – Innervates: C. Iliac crest ▪ Skin overlying iliac crest D. Thoracolumbar fascia ▪ Upper inguinal #2: The intricate subcutaneous venous plexus drains the ▪ Hypogastric regions umbilicus and drains into the superior and inferior vena cava. ▪ Internal oblique The superficial and inferior epigastric veins drain into the ▪ Transversus abdominis muscle inferior vena caval system. Ilioinguinal Nerve A. Only statement 1 is true – Originates as inferior terminal branch of anterior ramus of B. Only statement 2 is true spinal nerve L1 C. Both statements are true – Innervates: D. Both statements are false ▪ Skin of lower inguinal region ▪ Mons pubis #3: T/F: The Iliohypogastric nerve originates as inferior terminal branch of anterior ramus of spinal nerve L1. ▪ Anterior scrotum or labium majus ▪ Adjacent medial thigh True or False? ▪ Inferior-most internal oblique and transversus abdominis #4: The following are deep abdominal lymphatic vessels except? YL5 08.01b Gross Anatomy of the Anterior Abdominal Wall Part 2 11 of 12 A. External iliac lymph nodes 7. [A] — Ilioinguinal and iliohypogastric nerves are branches of the B. Common iliac lymph nodes L1 nerve, which plays a role in the motor innervation of the C. Internal iliac lymph nodes internal oblique muscle and the sensory (and not motor) D. Right and left lumbar lymph nodes innervation of the external oblique muscle. 8. [D] — The deep vessels of the lateral part of the wall include the #5: In which rectus sheath are both anterior and posterior 10th and 11th intercostal arteries and subcostal artery. The rectus sheaths present? superficial epigastric artery and deep circumflex iliac artery are A. Above the costal margin branches of the femoral artery and external iliac artery, B. Above the arcuate line respectively. C. Below the arcuate line 9. [B] — Retroperitoneal organs: surgically accessible anteriorly #6: A patient with an inguinal hernia is undergoing surgery. from the preperitoneal space The surgeon must cut through the rectus abdominis in the 10. [F] — The transversalis fascia is directly continuous with the iliac hypogastric region. The fascia that is posteriorly in contact fascia, internal spermatic fascia, and pelvic fascia. with the abdominis rectus is made up of which aponeurosis? REFERENCES A. Fascia transversalis B. Transversalis fascia and oblique fascia REQUIRED RESOURCES C. Internal oblique fascia and transversalis fascia Rivera-Nuez, M. (2024, January 15). Gross Anatomy of the D. Internal oblique fascia Anterior Abdominal Wall [Lecture slides]. SUPPLEMENTARY RESOURCES #7: A patient with an impaired L1 nerve could expect the following symptoms or conditions, except: Moore, K.l., Daley II, A.F. A.M.R. 2018. Clinically Oriented Anatomy. Wolters Kluewer. ISBN 9781496347213 A. Difficulty in contralateral trunk rotation ASMPH 2027. 08.20b: Gross Anatomy of the Anterior B. Affected ilioinguinal nerve Abdominal Wall by Michele Rivera-Nuez, MD, FPCS, C. Difficulty in ipsilateral trunk rotation FPAPRAS. D. Affected iliohypogastric nerve Vasković, J. (n.d.). Rectus sheath: Anatomy, definition, function. Kenhub. Retrieved January 17, 2024, from #8: The deep vessels of the lateral part of the wall include the https://www.kenhub.com/en/library/anatomy/rectus-sheath 9th and 10th intercostal arteries and subcostal artery. The superficial epigastric artery and deep circumflex iliac artery Evaluate us! are branches of the external iliac artery and femoral artery, respectively. ✔ Feedback Form: bit.ly/2028EvalsYearRoundForm A. Only statement 1 is true ✔ Errata Tracker: https://tinyurl.com/GIErrataTracker28 B. Only statement 2 is true FREEDOM SPACE C. Both statements are true D. Both statements are false #9: Which of the following is incorrectly paired up? A. Preperitoneal: fascia toward anterior side of body, before peritoneum B. Retroperitoneal organs: surgically accessible posteriorly from the preperitoneal space C. Retroperitoneal: fascia toward posterior side of body, behind peritoneum D. None of the above #10: T/F: The endoabdominal fascia is directly continuous with the iliac fascia, internal spermatic fascia, and pelvic fascia. True or False? Answer Key 1B, 2B, 3F, 4C, 5B, 6A, 7A, 8D, 9B, 10F RATIONALE TO ANSWERS OF REVIEW QUESTIONS 1. [B] — Pubic crest is an insertion of transversus abdominis 2. [B] — The intricate subcutaneous venous plexus drains the skin and subcutaneous tissue of the abdominal wall, not the umbilicus. 3. [F] — The iliohypogastric nerve originates as superior terminal branch of anterior ramus spinal nerve L1. It is the ilioinguinal nerve that originates as inferior terminal branch of anterior ramus of spinal nerve L1. 4. [C] — Deep abdominal lymphatic vessels include external iliac lymph nodes, common iliac lymph nodes, and right and left lumbar lymph nodes. Internal iliac lymph nodes are not included. 5. [B] — The rectus sheath above the costal margin has a deficient posterior layer of rectus sheath while the rectus sheath below the arcuate line has no posterior wall of rectus sheath. 6. [A] — Past the arcuate line the posterior rectus sheath is absent and the rectus abdominis is in direct contact with transversalis fascia YL5 08.01b Gross Anatomy of the Anterior Abdominal Wall Part 2 12 of 12