OS 206 Anterior Abdominal Wall, Peritoneal Cavity, and Diaphragm PDF

OS 206: ABDOMEN AND PELVIS ANTERIOR ABDOMINAL WALL, PERITONEAL CAVITY, and DIAPHRAGM UPCM 2029 | Dr. Christopher S. Constantino | LU3 A.Y. 2024-2025...

OS 206: ABDOMEN AND PELVIS ANTERIOR ABDOMINAL WALL, PERITONEAL CAVITY, and DIAPHRAGM UPCM 2029 | Dr. Christopher S. Constantino | LU3 A.Y. 2024-2025 side OUTLINE ​ Aponeurosis of the anterolateral abdominal muscles forming the I.​ Anterior Abdominal Wall II.​ Peritoneal Cavity rectus sheath[2025 Trans] A.​ Surface Anatomy A.​ Overview ​ Wider and shallower than the linea alba B.​ Layers of the Anterior B.​ Divisions ​ Marks the lateral margin of the rectus abdominis Abdominal Wall C.​ Peritoneal Tendinous Intersections C.​ Muscles Formations D.​ Innervation D.​ Clinical Correlates ​ Forms the six pack definition E.​ Blood Supply III.​ Diaphragm ​ Transverse lines that seem to transect the rectus abdominis F.​ Lymphatics IV.​ References ​ Divides the rectus abdominis into several sections G.​ Inguinal Region Inguinal Groove ​ Site of diagonal inguinal ligament I.​ ANTERIOR ABDOMINAL WALL ​ Area commonly known for the appearance of hernias ​ Part of the trunk between the thorax and the pelvis ​ Folded inferior edge of the external oblique aponeurosis ​ Dynamic and flexible container that houses organs of the digestive ​ Separates the abdominal region from the thigh (i.e., transition) system and part of the urogenital system ​ Junction is the area of the medial compartment of the thigh that Functions contains the groin muscles (adductor muscles of the hip) ​ Movements of the trunk ​ Diagnoses disease ○​ Knowing anatomical sites of organs can aid diagnosis based on their location ○​ Acts as the mirror of the clinician ○​ Symptoms of abdominal disease reflect on the abdominal wall[2025 Trans] ​ Increases intraabdominal pressure ○​ In the upper tract, muscles can facilitate forceful expulsion of air from the lungs and fluid through vomitus ○​ In the lower tract, muscles in the abdomen can facilitate expulsion of fluid through urine, feces, and gas ○​ Expulsion of the fetus is made possible by forceful contractions of abdominal muscles ​ Ambulation ○​ Core stability Figure 1. Boundaries of the AAW ○​ Transfer of forces ○​ Dynamic movement ○​ Proper posture and balance when walking ​ Protects and supports the viscera ○​ Tensing of muscles provide protection from the visceral organs[2025 Trans] Boundaries ​ All of the boundaries are palpable during physical examination ○​ Superior ​ Costal Margins (7th-10th ribs) ​ Xiphoid Process ○​ Inferior ​ Anterior superior iliac spine (ASIS) ​ Inguinal ligament ​ Pubic crest ​ Pubic symphysis ○​ Lateral ​ Vertical plane through ASIS A.​ SURFACE ANATOMY SKIN Umbilicus ​ Belly button or navel ​ Vestigial structure in adults Figure 2. Surface anatomy of the AAW ​ Found in the regions of L2, L3, and L4 BONY PROMINENCES ○​ Depends on how globular the abdomen is ​ Connections to the mother during fetal development ​ Similar to the boundaries, these are all palpable ○​ Once contained fetal arteries and veins ​ Costal margins and xiphoid process (T6 dermatome) ○​ Lifeline of the fetus ​ Pubic crest and symphysis ○​ Attachment of AAW muscles[2025 Trans] Linea Alba ​ Pubic tubercles ​ Midline connective tissue structure in the abdominal region ​ Iliac crest ​ Help in stabilizing core muscles ​ ASIS ​ Separates the left and right rectus abdominis muscles ​ Iliac tubercles ​ Discontinuous due to the umbilicus ​ Tendinous avascular raphe running vertically from the xiphoid process to the symphysis pubis ○​ Formed by decussating and intertwining aponeurotic fibers from the right and left sides of the muscular abdomen ​ Important surgical landmark ​ Obvious from xiphoid process to umbilicus ○​ Not obvious inferiorly Linea Semilunaris ​ “One pack,” lateral to the six pack ​ Lateral boundary of the rectus sheath ​ Site of union where the tendons of the lateral abdominal muscles meet the sheath surrounding the rectus abdominis muscle ​ Vertical indentation seen as a curved line from the inferior costal margin near the 9th costal cartilage to the pubic tubercle on each Trans 2 TG14: Gensolin, Geron, Gicom, Gomez, Gonzales, Guevarra, Guinto J. TH: Ordoñez 1 of 12  Figure 5. Quadrants of the abdomen Figure 3. Bony prominences of the AAW PLANES Horizontal ​ Subcostal Plane (L3) ○​ Passes through the lower body of the 10th costal cartilage on each side ○​ Transverse plane bisecting the body at the 10th costal margin and vertebral body of L3 ​ Transtubercular Plane (L5) ○​ At the level of the iliac tubercle Figure 6. Nine regions of the AAW ○​ Approximately 5 cm posterior to the ASIS on each side of the iliac crest and the body of the L5 B.​ LAYERS OF THE ANTERIOR ABDOMINAL WALL ○​ Marks the widest point between the ilia ​ Interspinous Plane ​ Most superficial: Skin ○​ Passes through the ASIS ​ Subcutaneous Tissue ​ Transpyloric Plane (L1 to L2) ○​ Consistent with other regions ○​ Preferred by many surgeons ○​ Inferior to the umbilicus (reinforced by elastic and collagen fibers) ○​ Midway between the superior borders of the manubrium, ​ Camper’s fascia sternum, and the pubic symphysis ​Superficial fatty layer; thicker ​ Around the area of the hilum of the kidney ​ Scarpa’s fascia ○​ If the patient is supine, it is found on the level of the 8th costal ​Deeper membranous layer; thinner cartilage and L1 ​More pronounced in the lower abdomen below the umbilicus ○​ Passes through: especially in children[2027 Trans] ​ Pylorus of the stomach (when supine) ​ Deep fascia (Investing fascia) ​ Neck of pancreas ○​ Lies directly over the muscles ​ Fundus of gallbladder ​ Muscles (Superficial to Deep) ​ Origins of the superior mesenteric artery ○​ External oblique ​ Hepatic portal vein ○​ Internal oblique ○​ Location of the root of transverse mesocolon, duodenal-jejunal ○​ Transversus abdominis junction, and hila of kidneys ○​ Rectus abdominis ​ Transumbilical Plane (L3 to L4) ○​ Pyramidalis ○​ Found at the level of the umbilicus ​ Transversalis fascia ○​ Divides the abdomen into quadrants with the median plane ○​ Almost a complete envelope in the area ​ Pain in the right lower quadrant is indicative of appendicitis ​ Extraperitoneal fat[2025 Trans] ○​ Pre/properitoneal fatty layer Umbilicus ○​ Thickness depends on nutritional status ​ Right and left midclavicular planes ​ Peritoneum ○​ Sagittal midpoints of the clavicle and inguinal ligament Figure 7. Layers of the AAW[Moore 8th ed.] Figure 4. Bony prominences of the AAW OS 206 Anterior Abdominal Wall, Diaphragm, and Peritoneal Cavity 2 of 12  1. EXTERNAL OBLIQUE Figure 10. External oblique muscle. Figure 8. (a) Cross-sectional image depicting the layers of the abdominal wall, including Camper’s fascia (b) Wound closure of abdominal wall. C.​ MUSCLES Figure 11. Lacunar ligament. Figure 12. Reflex inguinal ligament. Figure 9. Muscles of the AAW. ​ Direction of Fibers: inferomedial ​ Muscles of the AAW ○​ Fleshy, becoming aponeurotic ○​ External oblique ○​ Importance of knowing the direction of fibers: ○​ Internal oblique ​ When the patient’s AAW is hard to identify due to their ○​ Transversus abdominis condition (e.g., hacking injury or stabbing) ○​ Rectus abdominis ​ To locate nerves that are close to the muscles ○​ Pyramidalis ​ Origin: 5th to 12th ribs ​ Main Actions of the Muscles ​ Medially: linea alba ○​ Compress and support abdominal viscera ​ Inferiorly: inguinal ligament and iliac crest ○​ Flex and rotate trunk ○​ Inguinal Ligament ○​ Stabilize the pelvis and controls pelvic tilt ​ Inferiormost part of the external oblique ​ One thing that makes these muscles different from other muscles is ​ Thickening of external oblique aponeurosis from the ASIS to that they extend further to form flat, continuous sheets called the pubic tubercle[2027 Trans] aponeurosis ○​ Lacunar Ligament ○​ Linea semilunaris is important because these is where the ​ Formed via the reflection of external oblique interdigitation of the muscles starts and where the rectus sheath ​ Forms the superficial external inguinal ring[2027 Trans] is formed ​ Opens superior and lateral to the pubic tubercle[2027 Trans] ○​ Linea alba is where all the muscles insert; hence, it is a very ​ Where spermatic cord (males) and round ligament (females) of strong structure in the midline the uterus pass through[2027 Trans] ​ During core exercises, rectus abdominis is NOT the only muscle ​ More prominent in males[2027 Trans] that is activated or strengthened to get a well-defined core. Other ○​ Reflex Inguinal Ligament AAW muscles must also be activated. ​ Formed via the reflection of external oblique ​ See Appendix (Table 3) for summary table ​ Crosses to the other side Additional information from National Cancer Institute (n.d.): ​ Nerve supply: thoracoabdominal (T7 to T12 spinal nerves) and Aponeurosis = flat, wide bands of tissue holding one muscle to subcostal nerve another or to the periosteum (bone covering) ​ Action: flexion results in twisting of the trunk[2027 Trans] Tendon = tough, fibrous, cord-like tissue that connects muscle to bone or another structure Fascia = a connective tissue that surrounds and separates the muscles OS 206 Anterior Abdominal Wall, Diaphragm, and Peritoneal Cavity 3 of 12  2. INTERNAL OBLIQUE ​ Recall: linea alba, linea semilunaris, tendinous intersections (Section IA) ​ Direction of fibers: vertical ​ Origin: pubic symphysis and crest ​ Insertion: aponeurosis with other AAW muscles →​Superior: xiphoid process and 5th to 7th costal cartilages →​Medially: linea alba →​Laterally: linea semilunaris ▪​ Do NOT incise along the linea semilunaris because it is full of innervations[2025 Trans] ​ Cover: rectus sheath ​ Anchor: tendinous intersections of the external oblique, internal oblique, and transversus abdominis muscles →​For these 3 muscles to get to the linea alba, their aponeurosis must pass through the rectus abdominis Figure 13. Internal oblique muscle. ​ Attachments:[2025 Trans] →​Superiorly to the lower costal cartilages →​Inferiorly to the pubic crest and pubic symphysis ​ Nerve supply: thoracoabdominal (T6 to T12 spinal nerves) ​ When tensed in muscular people or those with low abdominal fat, the areas of the muscles between tendinous intersections bulge outward, forming abs RECTUS SHEATH ​ Incomplete compartment ​ Aponeurosis of 3 muscles →​External oblique, internal oblique, and transversus abdominis muscles →​The aponeurosis extends medially to the linea alba →​The muscles move laterally to medial ​ Lamina: divided into 2 portions due to aponeurosis of the internal Figure 14. Internal oblique and transversus muscles and conjoint tendon. oblique splitting into two as it approaches the rectus abdominis →​Anterior: aponeuroses of internal and external oblique (from ​ Direction of fibers: superomedial xiphoid process to pubic tubercle)[2025 Trans] ​ Origin: thoracolumbar fascia, anterior 2/3 of iliac crest, deep to →​Posterior: aponeuroses of internal oblique and transversus lateral 3rd of inguinal ligament abdominis (from xiphoid process to arcuate line)[2025 Trans] ​ Insertion: aponeurosis with other AAW muscles ○​ Superior: inferior borders of the 10th to 12th ribs ○​ Medially: linea alba (rectus sheath) ○​ Inferiorly: pecten pubis (conjoint tendon) ​ Conjoint tendon is important in integrity of inguinal canal by enforcing the weak areas to avoid herniation ​ Formed by both internal oblique and transversus abdominis muscles ​ Nerve supply: thoracoabdominal (T6 to T12 spinal nerves) and 1st lumbar nerves 3. TRANSVERSUS ABDOMINIS Figure 15. Rectus sheath. ​ Laminar organization with respect to the location (above or below the umbilicus) as seen in red circles in Figure X, differs in orientation with the rectus abdominis muscle ○​ Above Umbilicus: has anterior and posterior portions or laminae of the aponeurosis as it crosses the rectus abdominis ○​ Below Umbilicus: only has an anterior portion or lamina (hence, the rectus sheath is incomplete) Figure 15. Transversus abdominis muscle. ​ Direction of fibers: horizontal ​ Origin: internal surfaces of 7th to 12th costal cartilages, thoracolumbar fascia, iliac crest, connective tissue deep to the lateral 3rd of inguinal ligament ○​ A lot of origins because the abdomen is bigger compared to upper and lower extremities’ muscles in MSK ​ Insertion: aponeurosis with other AAW muscles ○​ Medially: linea alba (rectus sheath) ○​ Inferiorly: pecten pubis (conjoint tendon) ​ Nerve supply: thoracoabdominal (T6 to T12 spinal nerves) and 1st lumbar nerves Figure 18. Schematic diagram of the aponeurosis above the umbilicus (left) and below the umbilicus (right) in sagittal cut; skin = orange, external oblique = blue, 4. RECTUS ABDOMINIS internal oblique = green, transversus abdominis = purple, transversalis fascia = brown. Figure 19. Arcuate line. ​ Arcuate Line ○​ Transition zone between regions above and below the umbilicus Figure 16. Rectus abdominis muscle. OS 206 Anterior Abdominal Wall, Diaphragm, and Peritoneal Cavity 4 of 12  ​ Below this area, the abdomen has less reinforcement, is ​ Diastasis recti relatively weaker, and is more susceptible to hernias because there are less protective and supportive structures that resist protrusion of the abdominal wall. ​The structural integrity only relies on the transversalis fascia and peritoneum which are not as strong as the aponeurosis of the other muscles. ​Surgical application: Repair will be applied to the transversalis fascia immediately –due to the absence of posterior lamina Figure 24. Diastasis recti ​ Condition that overstretches linea alba ​ Common among females who gave birth as pregnancy puts a lot of pressure on abdomen especially if the abdominal muscles or core is not strong to begin with ​ Pregnancy pushes out the linea alba at the middle of the left and right muscles to make room for the growing baby ​ Treatment: improving integrity of the abdominal muscles by prescribing core exercises for patients planning pregnancies to prevent diastasis recti INCISIONAL HERNIA Figure 20. Harakiri ritual conducted by Samurais from Japan. ​ Case 1: →​In Seppuku in Japan, the katana will pass through the skin → anterior lamina of the internal oblique → rectus abdominis → vessels → posterior lamina of the internal oblique → transversus abdominis aponeurosis → transversalis fascia → peritoneum Figure 25. Incisional hernias ​ Hernia: a gap in this muscular wall that allows the contents inside the abdomen to protrude outward ○​ Protruding due to weakness of the external layers ​ Incisional hernia: when the muscular or aponeurotic layers of the Figure 21. Stab wound of a trauma patient in PGH. abdomen are not closed properly or do not heal properly ​ Case 2: ○​ Result: skin has grown already (therefore intestines cannot be →​Patient who sustained a stab in this area: skin → internal immediately be seen), but muscles have been traversed oblique (no need to mention anterior since it is only one ○​ Solution: putting a mesh (physical barrier) in the area portion and no posterior) → transversus abdominis → rectus ​ Importance of using different sutures and closing the abdomen abdominis → transversalis fascia → peritoneum layer by layer to reinforce the layers ​ Note: reinforces the need for knowledge of the layers of the AAW LINEA ALBA: CLINICAL APPLICATIONS 5. PYRAMIDALIS Figure 26. Pyramidalis Figure 22. Midline incision. ​ Shape: triangular ​ Surgical Application: Site for quick incisions in trauma surgeries ​ Origin: pubic crest, symphysis (e.g., gunshot wound) where you only have to worry about the ​ Insertion: linea alba aponeurosis and not structures such as blood vessels (Figure X) ​ Sometimes absent and not as important as the other 4 muscles ○​ Aids the rectus abdominis Supplementary Dissection Pictures ​ AAW layers BELOW the abdomen Figure 23. Suture scar in linea alba. ​ Suturing in linea alba leads to a very stable wound because it is a Figure 27. Layers of the AAW below the abdomen strong area (Figure X) due to the converged aponeurosis of all AAW ○​ Distinguished due to the immediate presence of the fascia muscles right after the muscular layer ○​ Consequence: Prone to necrosis because of the lack of blood ​ AAW layers ABOVE the abdomen supply OS 206 Anterior Abdominal Wall, Diaphragm, and Peritoneal Cavity 5 of 12  ​ Thoracoabdominal Nerves ○​ Give motor function to the muscles of the abdomen ○​ Anterior divisions continue across the costal margin in the subcutaneous tissue, becoming cutaneous branches that supply the skin ○​ Distal abdominal parts of the anterior rami of the inferior six thoracic spinal nerves (T7-T11)[2027 Trans] ○​ Former inferior costal nerves distal to the costal margin[2027 Trans] ​ Continuation of the 7 to 10th intercostal nerves. ​ Anterior Abdominal Cutaneous Branches[2027 Trans] Figure 28. Layers of the AAW above the abdomen ○​ T7- T9: Superior to the umbilicus ○​ Muscles → posterior rectus sheath (posterior lamina of ○​ T10: At the level of the umbilicus internal oblique + transversus abdominis) → transversalis ○​ T11, subcostal (T12), iliohypogastric, and ilioinguinal nerves (L1): fascia → peritoneum Inferior to the umbilicus ​ Overall image ​ Lateral Cutaneous Branches of the Thoracic Spinal Nerves [2027 Trans] ○​ T7-T9 or T10 ○​ Emerge from the musculature of the anterolateral wall to enter the subcutaneous tissue along the anterior axillary line. ​ Anterior Abdominal Cutaneous Branche [2027 Trans] ○​ Pierce the rectus sheath to enter the subcutaneous tissue a short distance from the median plane VENTRAL RAMI OF T1 ​ Iliohypogastric Nerve ○​ Provides sensory innervation to the hypogastric skin or suprapubic area ​ Ilioinguinal Nerve ○​ Enters the inguinal canal over the spermatic cord and exits through the external ring Figure 29. Zoomed out views of cuts presented earlier ○​ Provides sensory innervation to the upper medial thigh and scrotum & labia majora ○​ Upper cut: normal cut for cholecystectomies ​ L1 Dermatome ​ Although these days, usually done laparoscopically ○​ branches into iliohypogastric (more superior) and ilioinguinal ○​ Lower cut: normal cut for appendectomies nerves ○​ Superior sensory innervation of the skin above the pubic area D.​ INNERVATION ○​ Iliohypogastric (more superior) and ilioinguinal nerves pierce the ​ Thoracoabdominal, subcostal, and iliohypogastric nerves travel internal oblique muscle at the ASIS to travel superficial to it and antero-inferiorly between the internal oblique and transversus deep to the external oblique abdominal muscles[2027 Trans] ​ Note: both sensory because at that level, no more anterior ​ Main nerve supply from the thoracoabdominal nerves abdominal wall muscles Figure 30. Location and positioning of the AAW nerves VENTRAL RAMI OF T7 TO T12 ​ Primarily motor that gives off cutaneous branches ​ Dermatomes Figure 32. Dermatomes and innervation of the AAW. Supplementary Dissection Pictures: Nerves of the AAW Figure 31. Dermatomes ○​ Begin posteriorly overlying the intervertebral foramen, by which the spinal nerve exits the vertebral column[2027 Trans] Figure 33. Nerves of the AAW. ○​ Follows the slope of the ribs around the trunk[2027 Trans] ​ Internal oblique is flapped open ○​ T4: nipples ​ Exemplifies presence of nerves between internal oblique and ○​ T10: umbilicus transversus of abdominis ​ above umbilicus: 2 finger breadths ​ below umbilicus: 3 finger breadths ○​ T6: xiphoid process ○​ Note: There is NO C1 dermatome OS 206 Anterior Abdominal Wall, Diaphragm, and Peritoneal Cavity 6 of 12  E.​ BLOOD SUPPLY ARTERIAL SUPPLY ​ Superior Epigastric Artery ○​ Direct continuation of internal thoracic/mammary artery ○​ Enters the rectus sheath superiorly through its posterior layer ​ Located inside the rectus sheath ○​ Supplies superior part of rectus abdominis ○​ Anastomose with the inferior epigastric artery approximately in the umbilical region ​ Inferior Epigastric Artery ○​ From the external iliac artery ​ Also supplies the pubic and umbilical regions ○​ Supplies inferior part of rectus abdominis Figure 35. Lymphatics and associated veins of the AAW. ○​ Runs superiorly in the transversalis fascia to enter the rectus sheath below the arcuate line G.​ INGUINAL REGION ​ Located inside the rectus sheath ​ Inferior part of AAW ​ Superficial Epigastric Artery ​ Contents: ○​ Supplies the pubic and inferior umbilical area ○​ Inguinal ligament ​ Deep Circumflex Iliac Artery ○​ Inguinal canal ○​ Supplies the iliacus muscle and the inguinal and iliac fossa ○​ Inguinal triangle regions ​ Inherent site of weakness -> prone to hernias (“luslos”) ​ Superficial Circumflex Iliac Artery ○​ Supplies the inguinal region and the anterior thigh ​ Musculophrenic Artery ○​ Supplies the hypochondriac region and the antero-lateral diaphragm ○​ Branch of the internal thoracic artery ​ Posterior Intercostal, Subcostal, and Lumbar Arteries (10th and 11th) ○​ Arise from behind the aorta ○​ Supply the lumbar or flank regions Figure 36. Inguinal region. INGUINAL LIGAMENT ​ Inferior-most part of external oblique with most inserting to the pubic tubercle ​ Flexor retinaculum ○​ holds the hip flexors, iliopsoas and pectineus, in place ​ Passageway of femoral artery and vein to anterior thigh ​ Within is the inguinal canal Figure 34. Arterial supply of the AAW. VENOUS DRAINAGE ​ Superficial ○​ Internal thoracic v. ○​ Lateral thoracic v. ○​ Superior and inferior epigastric v. ○​ Paraumbilical v. ​ Deep ○​ Accompany the arteries bearing the same name ​ Blood drains away from the umbilicus via accompanying veins paired with their respective arteries (e.g., superior epigastric vein & superior epigastric artery) ​ Superficial Epigastric Vein (Femoral Vein Tributary) and Lateral Thoracic Vein (Axillary Vein Tributary) ○​ Anastomose through the thoraco-epigastric vein, uniting veins of Figure 37. Inguinal ligament. the superior and inferior halves of the body ​ Deeper anastomosis may exist or develop between the inferior INGUINAL CANAL and superior epigastric veins. ​ ~4 cm diagonal canal ​ 3 superficial inguinal veins end in the greater saphenous vein of the ​ Formed in relation to the relocation of the testes (used to be at the lower limb abdomen, descends to the scrotum) ​ Superficial and Deep Anastomoses: For collateral circulation ​ Opened during operations involving hernias when either vena cava is blocked (during trauma wherein major ○​ If it remains open, an omentum can pass through it, resulting in circulation is compromised) an inguinal hernia ​ Deep Venous Network ​ Area of inherent weakness (no muscle covering) ○​ Accompanies the arteries discussed ○​ Reinforced by pubic attachments of the internal oblique and transversus abdominis aponeurosis that merge to form the F.​ LYMPHATICS inguinal falx (conjoint tendon) and the reflected inguinal ligament ​ Superficial ○​ Axillary nodes ​ Also includes cervical nodes and some of the parasternal lymph nodes ​ Covers the area ABOVE the transumbilical plane ​Transumbilical plane: imaginary line from umbilicus to ASIS ○​ Superficial inguinal nodes ​ Covers the area BELOW the transumbilical plane ​ Deep ○​ Accompany deep veins ○​ Drains to: ​ Lumbar (para-aortic) lymph nodes ​ Common iliac nodes ​ External iliac lymph nodes Figure 38. Inguinal canal and spermatic cord. OS 206 Anterior Abdominal Wall, Diaphragm, and Peritoneal Cavity 7 of 12 ​ Openings: arising from inguinal ligament ○​ Deep inguinal ring (“entrance”) ​ Cremasteric Reflex: for temperature regulation for sperm ​ Opening in transversalis fascia production; impairment sign of L1, L2 pathology or testicular ​ Above the midpoint of the inguinal ligament and lateral to the torsion inferior epigastric artery ○​ External Spermatic Fascia: from external oblique aponeurosis ​ Only direct opening to the abdomen and investing fascia ○​ Superficial inguinal ring (“exit”) ​ Opening in the external oblique aponeurosis, superolateral to the pubic tubercle ​ Medial umbilical ligament: remnant of the medial umbilical artery Figure 42. Cremasteric reflex (left) and coverings of the spermatic cord (highlighted at the right). ​ Contents: ○​ Ductus deferens ​ Muscular tube for sperm from the epididymis to the ejaculatory Figure 39. Inguinal ligament openings. duct ○​ Testicular artery ○​ Artery of ductus deferens ○​ Cremasteric artery ○​ Pampiniform venous plexus ​ Network of up to 12 veins that converge superiorly as the right or left testicular veins ○​ Lymphatics ○​ Nerves ​ Sympathetic nerve fibers on arteries and sympathetic/parasympathetic nerve fibers on ductus deferens and genitofemoral nerve Figure 40. Inguinal canal borders. ○​ Vestige of processus vaginalis ​ Boundaries: ○​ Anterior wall: External oblique aponeurosis (EOA) & the origin of the internal oblique ○​ Posterior wall: Transversalis fascia ○​ Roof: Arched fibers of the internal oblique and transverse abdominis ​ Lateral portion: transversalis fascia ​ Central portion: musculoaponeurotic arches of Internal oblique and transversus abdominis ​ Medial portion: Medial crus of external oblique aponeurosis ○​ Floor: Grooved surface of inguinal ligament and lacunar ligament ​ Central: Inguinal ligament ​ Medial: Lacunar ligament ○​ Contents: ​ Males: Spermatic cord ​ Females: Round ligament of the uterus ​ Blood and lymphatic vessels ​ Ilioinguinal nerve (from L1 ventral rami) and genital branch of the genitofemoral nerve Figure 43. Spermatic cord contents. ​ Round ligament: Not a homolog of the spermatic cord and does not contain comparable structures INGUINAL CANAL ​ A.K.A. Hesselbach’s triangle or the inguinal trigone ​ Site of direct hernia especially in weight lifters ○​ Direct protrusion through the abdominal wall due to increased abdominal pressure ○​ Inherent weakness due to ​ Proximity to deep inguinal ring (only opening in the abdomen) ​ Absence of muscles in the area (only made up of aponeurosis) ​ Borders: ○​ Lateral: inferior epigastric artery ○​ Medial: lateral border of rectus abdominis (linea semilunaris) ○​ Inferior: inguinal ligament Figure 41. Boundaries of the inguinal canal. SPERMATIC CORD ​ As testes migrate from the abdominal interior to the scrotum, they carry with them the abdominal layers they pass through ○​ Begins at the deep inguinal ring lateral to the inferior epigastric vessels ○​ Passes through the inguinal canal ○​ Exits at the superficial inguinal ring ○​ Ends in the scrotum at the posterior border of the testes ​ Coverings: ○​ Internal Spermatic Fascia: from transversalis fascia ○​ Cremasteric Muscle & Fascia: from investing fascia of internal oblique muscle ​ Has loops of cremasteric muscle ​ Formed by lowermost fascicles of internal oblique muscle Figure 44. Borders of the inguinal triangle. OS 206 Anterior Abdominal Wall, Diaphragm, and Peritoneal Cavity 8 of 12  ​ Mesentery: gives mobility to the organs and connects the organs INGUINAL HERNIA to the body wall B.​ DIVISIONS ​ Greater and lesser sac ​ Essential for determining fluid collection due to pathology and/or trauma ○​ In trauma cases with suspected internal abdominal bleeding FAST (Focused Assessment with Sonography in Trauma) is performed GREATER SAC 2028 Trans Additional Information ​ Main, larger part of the abdominal cavity ​ Divided into supracolic and infracolic compartments by the transverse mesocolon Supracolic Compartment Figure 45. Acquired/direct inguinal hernia (the bowel entered lateral to the vessel ​ Subphrenic, subhepatic recess, hepatorenal recess because the deep inguinal ring is lateral to the vessels). 2028 Trans Additional Information ​ Due to the protrusion of abdominal organs and structures such as ​ Upper gastrointestinal tract above the transverse mesocolon the intestines and omentum into inguinal area ​ Boundaries: ​ Occurs mostly in males (~ 86%) due to the passage of the spermatic ○​ Right lobe of liver cord through the inguinal canal ○​ Right kidney (inferiorly) ​ Palpated at the testes or labia majora ○​ Suprarenal gland ​ Location: ○​ Right subhepatic space ○​ First part of duodenum ○​ Anterior surface of right kidney ○​ Lowest point of peritoneal cavity in supine position ​ Contents: ○​ Stomach ○​ Duodenum ○​ Pancreas ○​ Liver ○​ Spleen ​ Recesses and Spaces ○​ Possible sites of accumulation of fluid ○​ Subphrenic Recess ​ Between the liver and diaphragm ○​ Subhepatic Recess Figure 46. Difference between direct and indirect hernia. ​ Below the liver ​ Blood or bile could accumulate here Direct ○​ Hepatorenal Recess or Morison’s Pouch ​ Usually acquired ​ Most dependent and deepest area of peritoneal cavity ​ Due to the weakening of the muscles and the walls of the inguinal especially in supine position canal ​ Entry of hernia is medial to the inferior epigastric vessels, Infracolic Compartment < pushing through the peritoneum and transversalis fascia in inguinal ​ Infracolic space, paracolic gutters, rectovesical, rectouterine pouch triangle to enter the inguinal canal