Anterior Abdominal Wall and Inguinal Canal PDF
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Summary
This document provides a detailed explanation of the anterior abdominal wall and inguinal canal, covering regions, planes, layers, and muscles. It also describes the location, functions, and relationships of abdominal organs within each quadrant. Helpful for students studying anatomy and related medical fields.
Full Transcript
12. Anterior Abdominal Wall, Inguinal Canal and Peritoneum A: Abdominal Regions, Planes and Quadrants Abdominal Regions 9 regions used to describe the location of abdominal organs, pains or pathologies Delineated...
12. Anterior Abdominal Wall, Inguinal Canal and Peritoneum A: Abdominal Regions, Planes and Quadrants Abdominal Regions 9 regions used to describe the location of abdominal organs, pains or pathologies Delineated by 4 planes: o 2 sagittal (vertical) o 2 transverse (horizontal) Right hypochondrium Epigastric Left Hypochondrium RH E LH Right lumbar (lateral) Umbilical Left lumbar (lateral) RL U RL Right inguinal/iliac Pubic (hypogastric) Left inguinal/iliac RI P RI Abdominal Planes 1 Zaid Ganie Most often used: Transverse planes- o subcostal plane § passes through the inferior border of the 10th costal cartilage on each side o Transtubercular plane § Passes through the iliac tubercles Mid-inguinal points: Sagittal planes- Midpoints of the lines o Midclavicular planes joining the anterior superior § Pass from the midpoint of the clavicles to the mid-inguinal points iliac spine and the pubic tubercles on each side Other planes used: Transverse planes- o Transpyloric plane § Horizontal line through L1 vertebra o Interspinous plane § Passes through the anterior superior iliac spine Sagittal planes- o Semilunar lines § Lines at which layers of the rectus sheath fuse lateral to the rectus abdominis muscle and medial to the oblique muscles Abdominal Quadrants Defined by 2 planes- o Transumbilical plane § Passes through the umbilicus o Median plane Organs present in each quadrant: Right Upper Quadrant Left Upper Quadrant 1. Liver- right lobe 1. Liver- left lobe 2. Gallbladder 2. Spleen 3. Stomach- pylorus 3. Stomach 4. Duodenum- parts 1-3 4. Jejunum and proximal ileum 5. Pancreas- head 5. Pancreas- body and tail 6. Right suprarenal gland 6. Left suprarenal gland 7. Right Kidney 7. Left kidney 8. Right colic (hepatic) flexure 8. Left colic (splenic) flexure 9. Ascending colon- superior part 9. Descending colon- superior part 10. Transverse colon- right half 10. Transverse colon- left half Right Lower Quadrant Left Lower Quadrant 1. Cecum 1. Sigmoid colon 2. Appendix 3. Ileum (most of) 4. Ascending colon- inferior part 2. Descending colon- Inferior part 5. Right ovary 3. Left ovary 6. Right uterine tube 4. Left uterine tube 7. Right ureter- abdominal part 5. Left ureter- abdominal part 8. Right Spermatic cord- abdominal part 6. Left spermatic cord- abdominal part 9. Uterus (if enlarged) 7. Uterus (if enlarged) 10. Urinary bladder (if full) 8. Urinary bladder (if full) 2 B: Anterolateral Abdominal Wall Borders Superior o Cartilages of 7th to 10th ribs o Xiphoid process of sternum Inferior o Inguinal ligament o Superior margins of the anterolateral aspects of the pelvic girdle § Iliac crests, pubic crests, pubic symphysis Layers 1. Skin 2. Superficial fascia (2 layers below umbilicus) o Camper fascia (superficial fatty layer) o Scarpa fascia (deep membranous layer) 3. Investing superficial fascia External oblique muscle 4. Investing intermediate fascia Internal oblique muscle 5. Investing deep fascia Transversus Abdominis 6. Endoabdominal (transversalis) fascia 7. Extraperitoneal fat 8. Peritoneum Muscles 3 Muscle Origin Insertion Innervation Main Action External oblique External surfaces of 5th–12th ribs Linea alba T7-T11 spinal nn. Compress abdominal Pubic tubercle Subcostal n. contents Lateral lip of iliac crest Both muscles flex trunk Each bends trunk to same side Each rotates trunk to the opposite side Internal oblique Thoracolumbar fascia Inferior borders of 10th–12th ribs Compress abdominal Anterior 2/3 of iliac crest Linea alba contents Connective tissue deep to lateral Pecten pubis via conjoint tendon Both muscles flex trunk 1/3 of inguinal ligament Anterior rami of Each bends trunk and T6-T12 spinal nn. turns anterior part of L1 spinal n. abdomen to same side Transversus Internal surfaces of 7th–12th Linea alba Compress abdominal abdominis costal cartilages aponeurosis of internal oblique contents Thoracolumbar fascia Pubic crest Iliac crest Pecten pubis via conjoint tendon Connective tissue deep to lateral 1/3 of inguinal ligament Rectus abdominis Pubic symphysis Xiphoid process Anterior rami of Compress abdominal Pubic crest 5th–7th costal cartilages T6-T12 spinal nn. contents Flex lumbar vertebrae Controls tilt of pelvis Pyramidalis Front of pubis Linea alba Anterior ramus of Tenses the linea alba Pubic symphysis T12 spinal n. 3 paired flat muscles Combined actions of anterolateral abdominal wall muscles o External oblique (hands in pockets) Move the trunk & maintain posture o Internal oblique (hands on tits) Strong expandable support (stomach, uterus) o Transversus abdominis (horizontal fibres) Depress the ribs by approximating anterior costal margin and 2 paired flat muscles pubic crest (expiration) Compress abdomen (evacuation & heavy weight lifting) o Rectus abdominis Support & protect viscera especially intestines o Pyramidalis 4 External oblique aponeurosis Begins medially at the midclavicular line and inferiorly at the spino-umbilical line Fibres decussate at the linea alba Most fibres become continuous with tendinous fibres of the contralateral internal oblique muscle o The contralateral external and internal oblique muscles together form a digastric muscle since they share a common tendon o e.g. The right external oblique and left internal oblique work together when flexing and rotating to bring the right shoulder toward the left hip Inguinal ligament (Poupart ligament) o Inferior margin of external oblique aponeurosis o Thickened under-curving fibrous band with a free posterior edge o Spans between the anterior superior iliac spine and the pubic tubercle o Continuous with the deep fascia of the thigh inferiorly Lacunar ligament o at medial end of inguinal ligament to superior pubic ramus Pectineal ligament (of Cooper) o most lateral fibres of lacuna ligament on pecten pubis Internal oblique aponeurosis Fibres also become aponeurotic at the midclavicular line Transversus abdominis Aponeurosis forms conjoint tendon with internal oblique Neurovascular plane is superficial to this muscle Muscle Contribution to covering of spermatic cord* Contribution to rectus sheath External oblique External spermatic fascia Aponeurosis- anterior layer Internal oblique Cremaster muscle & fascia Aponeurosis- both layers Transversus abdominis No contribution Aponeurosis- posterior layer * Transversalis fascia contributes as internal spermatic fascia Rectus abdominis Enclosed in the rectus sheath Anchored transversely by attachment to the anterior layer of the rectus sheath at 3 tendinous intersections o At the level of the xiphoid process o Halfway between the xiphoid process and umbilicus o At the umbilicus To test action of muscle: o Raise head while lying flat on back without using arms Pyramidalis Variable in size o Larger on one side (may be double) Not always present (80% only) Rectus Sheath, Linea Alba and Umbilical Ring Rectus sheath: Strong, incomplete fibrous compartment of the rectus abdominis and pyramidalis muscles Contents: o Rectus abdominis and pyramidalis muscles o Superior and inferior epigastric arteries and veins o Lymphatic vessels o Abdominal portions of the anterior rami of spinal nerves T7-T12 (thoraco-abdominal nerves) Formed by the decussation and interweaving of the aponeuroses of the flat abdominal muscles o Anterior layer- external oblique and anterior lamina of internal oblique o Posterior layer- transversus abdominis and posterior lamina of internal oblique 5 Levels of variation: Arcuate line: o One third distance from the umbilicus to the pubic crest o Demarcates transition in composition of posterior layer of rectus sheath o Above arcuate line (superior ¾ of posterior layer): § Made from aponeuroses of transversus abdominis and posterior lamina of internal oblique o Below arcuate line (inferior ¼ of posterior layer): § All 3 aponeuroses pass anterior to the rectus abdominis § Only the thin transversalis fascia covers the rectus abdominis posteriorly Superior to the costal margin o Posterior layer is deficient § Transversus abdominis continues superiorly as transversus thoracis internal to costal cartilages § Internal oblique attaches to the costal margin o Rectus abdominis lies directly on the thoracic wall Linea alba: Interlacing fibres of the anterior and posterior layers of the rectus sheath in the anterior median line Separates the bilateral rectus sheaths Narrows inferior to the umbilicus to the width of the pubic symphysis Widens superiorly to the width of the xiphoid process Transmits small vessels and nerves to the skin Umbilical ring: In the middle of the linea alba beneath the umbilicus All layers of the anterolateral abdominal wall fuse 6 Neurovasculature Dermatomes Anterior rami of T7-T12 and L1 Nerves Dermatomes Origin Thoraco-abdominal T7-T11 Continuation of 7th – 11th intercostal nerves distal to the costal margin 7th – 9th lateral cutaneous br. T7-T9 Anterior divisions of 7th - 9th intercostal nerves Subcostal T12 Anterior ramus of T12 Iliohypogastric L1 Superior terminal branch of anterior ramus of L1 Ilio-inguinal L1 Inferior terminal branch of anterior ramus of L1 T7-T9: skin superior to umbilicus T10: skin around umbilicus T11-L1: skin inferior to umbilicus L1: inguinal fold Referred pain: T10 from appendix Superficial veins Internal thoracic v. ® brachiocephalic v. Lateral thoracic v. ® axillary v. Subcutaneous venous plexus Thoraco-epigastric v. Peri-umbilical vv. ® hepatic portal v. Inferior epigastric v. ® external iliac v. Superficial epigastric v. ® femoral v. Lymph drainage Superficial vessels above transumbilical plane o Axillary lymph nodes o Parasternal lymph nodes Superficial vessels below transumbilical plane o Superficial inguinal lymph nodes Deep vessels o External iliac lymph nodes o Common iliac lymph nodes o Right lumbar (caval) lymph nodes o Left lumbar (aortic) lymph nodes 7 Arteries Artery Origin Course Supply Musculophrenic Descends along costal margin Hypochondrium Anterolateral diaphragm Internal thoracic Superior epigastric Descends in rectus sheath deep to rectus Rectus abdominis m. abdominis Epigastric and upper umbilical regions 10th&11th posterior intercostal Aorta Descends between internal oblique and Lateral (lumbar) region Subcostal transversus abdominis Inferior epigastric* Ascends in rectus sheath deep to rectus Rectus abdominis m. External iliac abdominis Deep pubic & lower umbilical regions Deep circumflex iliac Runs parallel to inguinal ligament deep in Iliacus m. anterior abdominal wall Deep inguinal region & iliac fossa Superficial circumflex iliac Runs in subcutaneous tissue along the Superficial inguinal region Femoral inguinal ligament Adjacent anterior thigh Superficial epigastric Runs in subcutaneous tissue toward Superficial pubic & lower umbilical umbilicus regions *Enters the rectus sheath at the level of the arcuate line Internal Anterolateral Abdominal Wall Covered with transversalis fascia, extraperitoneal fat and parietal peritoneum Umbilical peritoneal folds- o Folds on the infra-umbilical part of the internal surface of the anterolateral abdominal wall o 2 on each side and 1 in the median plane o Median umbilical fold § Apex of bladder to umbilicus § Covers median umbilical ligament Remnant of urachus o Medial umbilical folds § Lateral to the median umbilical fold § Cover medial umbilical ligaments Obliterated umbilical aa. o Lateral umbilical folds § Lateral to the medial umbilical folds § Cover the inferior epigastric vessels peritoneal fossae- o Depressions lateral to umbilical folds o Potential sites for hernia o Supravesical fossa- § Between median and medial umbilical folds § Level rises and falls with filling of bladder o Medial inguinal fossa- § Between medial and lateral umbilical folds § AKA inguinal triangle § Potential site for direct inguinal hernias o Lateral inguinal fossa- § Lateral to the lateral umbilical folds § Include the deep inguinal ring § Potential sites for indirect inguinal hernia 8 C: Inguinal Canal Inguinal Region AKA groin Extends between anterior superior iliac spine and pubic tubercle Bilaminar flexor retinaculum of the hip joint: o Formed by inguinal ligament and iliopubic tract o Extends from anterior superior iliac spine to pubic tubercle o Spans the Subinguinal space (lacunar ligament forms medial boundary) Inguinal ligament: o Dense band constituting inferior most part of the external oblique aponeurosis o Insertions: Fibres Insertion Name Most fibres Pubic tubercle inguinal ligament Deeper fibres passing posteriorly Superior pubic ramus Lacunar ligament Lateral deeper fibres Pecten pubis Pectineal ligament Superior fibres fanning upward Contralateral external oblique aponeurosis Reflected inguinal ligament Iliopubic tract o Thickened inferior margin of the transversalis fascia o Appears as a fibrous band running parallel and deep to the inguinal ligament o Reinforces the posterior wall and floor of the inguinal canal Inguinal Canal Location Oblique passage 4cm long directed inferomedially Lies parallel and superior to the medial half of the inguinal ligament Openings Deep (internal) inguinal ring o Oval structure that is larger in males than females o Entrance to the inguinal canal o Superior to the middle of the inguinal ligament and lateral to the inferior epigastric a. o Evagination in the transversalis fascia § Continues into the canal forming the innermost covering of the canal Superficial (external) inguinal ring o Triangular slit in the external oblique aponeurosis superolateral to the pubic tubercle o Margins: § Lateral crus- attaches to the pubic tubercle § Medial crus- attaches to the pubic crest o Intercrural fibres prevent the slit from expanding 9 Boundaries Boundary Lateral Third/Deep Ring Middle Third Medial Third/Superficial Ring Posterior wall Transversalis fascia Transversalis fascia Conjoint tendon and reflected inguinal ligament Anterior wall Internal oblique & lateral crus Lateral crus and intercrural fibres Intercrural fibres and external spermatic fascia Musculo-aponeurotic arches of internal Roof Transversalis fascia Medial crus oblique and transversus abdominis Floor Iliopubic tract Inguinal ligament Lacunar ligament Contents In both male and female In female Ilioinguinal n. Round ligament of Sympathetic nn. uterus Lymphatics In male External spermatic fascia Cremasteric fascia Internal spermatic fascia Spermatic cord: o Vas deferens o Testicular a., artery to vas deferens, cremasteric a. o Pampiniform plexus of veins o Genital branch of genitofemoral n. o Extraperitoneal fat 10 D: Abdominal Hernias Abnormal protrusion of a structure through tissues which normally contain it Most commonly in the inguinal, femoral, umbilical and epigastric regions. Inguinal hernia: o abdominal structures through inguinal canal as a site of weakness in abdominal wall Feature Indirect Inguinal Hernia Direct Inguinal Hernia Embryological descent of the testis with persistent Predisposing factor Acquired through weakness or defect of transversalis fascia processus vaginalis (Canal of Nuck in females) Passes entire inguinal canal via deep and Placed over body of pubis but does not pass via deep ring Course of hernia superficial rings. (Hesselbach’s triangle). Rarely descends into scrotum Relation of Inferior epigastric Medial to neck of hernia sac Lateral to neck of hernia sac vessels Spermatic Cord Directly Behind Lateral and posterior side Frequency Most common (more than 2/3) Much less common Gender frequency More common in young males More in males. Indirect inguinal hernia Femoral hernia: o Below and lateral to pubic tubercle o Bound laterally by femoral v. o Bound medially by lacunar ligament o Hernial sac compresses the contents of the femoral canal o More common in females 11 Anatomical features of inguinal canal that minimize herniation 1. Obliquity of canal ensures that the 2 rings do not overlie one another. 2. The strongest part of anterior wall lies in front of deep ring and strongest part of posterior wall lies behind superficial ring. o When intra-abdominal pressure rises, anterior and posterior walls of the canal are firmly opposed 3. Canal is compressed when abdominal muscles contract by descent of fibres of internal oblique and transversus abdominis (arched roof) 4. Slit valve action of the two crural rings of external oblique 5. Contraction of cremasteric muscle closes superficial ring 12 D: Peritoneum Continuous, transparent serous membrane Lines abdominopelvic cavity and invests the viscera Consists of 2 continuous layers: Parietal Peritoneum Visceral Peritoneum Lines abdominopelvic wall & Inferior surface of diaphragm Lines outer surface of most viscera (serosa) Loosely attached by extraperitoneal connective tissue Firmly adherent to viscera Blood supply: parietal arteries from inferior phrenic, intercostal (lower 6), lumbar Usually from blood vessels which supply the viscera & obturator aa. Nerve supply: nerves that supply the wall namely; phrenic, intercostal (lower 6), Nerve to the viscera lumbar & obturator nerves (pelvic) Sensitive to pain (Somatic innervation & referred to middle abdominal regions), Insensitive to pain (Autonomic) pressure, heat, cold and lacerations Development: somatopleuric layer of lateral plate mesoderm Splanchnic layer of lateral plate mesoderm Both layers consist of mesothelium o Layer of simple squamous epithelium o secretes serous fluid to lubricate & avoid friction in movements of viscera on each other Peritoneal Fluid Composition Water, electrolytes and other substances from interstitial fluid in adjacent tissues Proteins, desquamated mesothelial cells, macrophages, fibroblasts & lymphocytes Absorption Absorbed by lymphatic vessels mostly on the inferior surface of the diaphragm In females- o Communication present with the exterior through uterine tubes, uterine cavity and vagina o Potential pathway of infection from exterior Applied anatomy Abnormal collection of free fluid in peritoneal cavity- Ascites Procedure for draining of ascitic fluid- Paracentesis Abdominis Peritoneal Formations 1. Mesentery Double layer of peritoneum Invagination of the peritoneum by an organ Constitutes a continuity of the visceral and parietal peritoneum Provides a means for neurovascular communications between the organ and the body wall Has a core of connective tissue containing blood and lymphatics, nerves and fat Small intestine mesentery is known as ‘the mesentery’ Mesenteries related to other specific parts of the alimentary canal are named accordingly o Transverse mesocolon o Sigmoid mesocolon o Meso-oesophagus o Mesogastrium 13 2. Omentum Double layered extension of peritoneum Passes from the stomach and proximal part of the duodenum to adjacent organs in the abdominal cavity Greater omentum o 4-layered peritoneal fold o Hangs down like an apron from the greater curvature of the stomach and the proximal part of the duodenum o After ascending, it folds back and attaches to the anterior surface of the transverse colon and its mesentery o Limits spread of infection by moving to sites of infection & sealing it from surrounding area Lesser omentum o Smaller, double-layered peritoneal fold o Connects the lesser curvature of the stomach and the proximal part of the duodenum to the liver o Contains the portal triad of structures running between the duodenum and liver in the free edge: § Portal vein (posteriorly) § Common bile duct (right anterior) § Hepatic artery (left anterior) 3. Peritoneal ligaments Consists of a double layer of peritoneum that connects an organ with another organ or to the abdominal wall Connections of the liver: o Falciform ligament- to supra-umbilical anterior abdominal wall and diaphragm § Contains ligament teres hepatis (ligamentum teres)- remnant of umbilical vein o Triangular ligaments (right and left)- to diaphragm o Coronary ligaments (superior and inferior layers)- to diaphragm o Hepatogastric ligament- to stomach by the membranous portion of the lesser omentum o Hepatoduodenal ligament- to duodenum by thickened free edge of the lesser omentum o Hepatocolic ligament- liver to right colic flexure of transverse colon Connections of the stomach: o Gastrophrenic ligament- to inferior surface of diaphragm o Gastrosplenic ligament- to the spleen § Reflects to the hilum of the spleen o Gastrocolic ligament- to the transverse colon by the apron-like part of the greater omentum § Descends from the greater curvature of the stomach, turns under and ascends to the transverse colon Other o Lienorenal/splenorenal ligament- spleen to left kidney 14 4. Peritoneal folds Reflection of peritoneum that is raised from the body wall by underlying blood vessels, ducts and ligaments formed by obliterated foetal vessels (see page 8) 5. Peritoneal recess/fossa Blind pouch of peritoneum formed by a peritoneal fold 1. Superior duodenal recess 2. Inferior duodenal recess 3. Duodenojejunal fold 4. Mesentericoparietal fossa 5. Superior ileocecal 6. Inferior ileocecal 7. Retrocecal (with appendix) 8. Intersigmoid fossa* These recesses are sites of internal hernia or strangulation of intestine & * Associated with left ureter also spread pathological fluid like pus, water or blood. Subdivisions of the Peritoneal Cavity Compartments of the abdominal cavity Transverse mesocolon divides abdominal cavity into supracolic and infracolic compartments Supracolic compartment o contains § Stomach § Liver § Spleen o Divided by falciform ligament § Right and left subphrenic spaces directly below diaphragm § Right subhepatic space (Morrison’s pouch) commonest site of subphrenic abscess & accumulation of fluid or pus § Left subhepatic space Omental bursa (lesser sac) Infracolic compartment- o contains § Small intestine § Ascending and descending colon o Lies posterior to the greater omentum o Divided into right and left infracolic spaces by mesentery of the small intestine § Right- extraperitoneal space corresponds to ‘bare area of the liver’ § Left- around left suprarenal gland & upper pole of left kidney Paracolic gutters- o Grooves between lateral aspect of the ascending or descending colon and the posterolateral abdominal wall o Allow free communication between supracolic and infracolic compartments (freest on right side) o Also communicates inferiorly with rectouterine pouch in females & rectovesical pouch in males 15 Divisions of the peritoneal cavity The peritoneal cavity is divided into the greater and lesser peritoneal sacs Greater sac- main and larger part of the peritoneal cavity Lesser sac (omental bursa)- lies posterior to the stomach and lesser omentum Omental bursa (lesser sac): Superior recess o Limited superiorly by the diaphragm and posterior layers of the coronary ligament of the liver Inferior recess o Between the superior parts of the layers of the greater omentum Permits free movement of the stomach on the structures posterior and inferior to it Omental foramen (epiploic foramen)- o Communication between the greater sac and the omental bursa o Situated posterior to the free edge of the lesser omentum at level of T12 vertebra o Can be located by running a finger along the gallbladder to the free edge of the lesser omentum o Boundaries: § Anterior- Hepatoduodenal ligament with portal triad § Posterior- IVC and right crus of diaphragm § Superior- Caudate lobe of liver § Inferior- Superior part of duodenum and portal triad o Internal hernia can occur into omental bursa through epiploic foramen Rectouterine pouch of Douglas Most dependent part of peritoneal cavity in standing position & of pelvic cavity in supine position in females Boundaries: o Anterior: Uterus & posterior fornix of vagina o Posterior: Rectum o Floor: Rectovaginal fold of peritoneum 16 E: Arrangement of Abdominal Viscera Organs present in each abdominal region: Right Hypochondriac Epigastric Left Hypochondriac Liver & Gall bladder Liver & Transverse colon, Stomach & Spleen Kidney & suprarenal gland, Abdominal aorta & inferior vena cava, Kidney & Suprarenal gland Colon (hepatic flexure) Pylorus & Duodenum (1st part) Colon (splenic flexure) Transpyloric plane Right Lumbar (Lateral) Umbilical Left Lumbar (Lateral) Kidney Transverse colon, Duodenum, pancreas, Kidney, Descending colon Ascending colon Abdominal aorta, Inferior vena cava, Pancreas Small intestine Small intestine, Iliac vessels Small intestine (jejunum) Intertubercular plane Right Inguinal (Iliac) Hypogastric Left Inguinal (Iliac) Caecum, Appendix Distensible organs of pelvis e.g. bladder when full; Sigmoid colon Small intestine (ileum) uterus from 12th week of pregnancy. Small intestine Small intestine, Iliac vessels, Spermatic cords Classification of Abdominal Structures Classification based on relationship of the viscera with the peritoneum Intraperitoneal organs: o Almost completely covered with visceral peritoneum Secondary retroperitoneal organs: o Organs that originally lied intraperitoneally, but have been pushed to the side during development o These organs and their mesenteries adhered to the abdominal wall Primary retroperitoneal organs: o Between the parietal peritoneum and the posterior abdominal wall o Have parietal peritoneum only on their anterior surfaces o Have been lying outside the peritoneal cavity from the beginning of development o Embedded in connective tissue and are therefore immobile Intraperitoneal Organs Secondary retroperitoneal organs Primary retroperitoneal organs 1. Stomach 1. Duodenum (except prox. ½ of 1st part) 1. Kidneys and ureters 2. Liver, gallbladder and spleen 2. Pancreas- head, neck and body 2. Suprarenal glands 3. Pancreas- tail 3. Colon- ascending and descending 3. Aorta and inferior vena cava 4. Duodenum (proximal ½ of 1st part) 4. Rectum (middle 1/3) 4. Rectum (lower 1/3) and anal canal 5. Jejunum and ileum 6. Appendix and Cecum 7. Transverse and sigmoid colon 8. Rectum (upper 1/3) 9. Body of uterus, oviducts and ovaries 17