Abdomen 1: Digestive System, Anterior Abdominal Wall & Inguinal Region PDF

ABDOMEN 1: Digestive System, Anterior Abdominal Wall & Inguinal Region John Vincent O. Estrada, MD | 20 NOVEMBER 2023 OUTLINE I. ANTERIOR ABDOMINAL WALL A. BOUNDARIES B. ABDOMINAL PLANES 1. TRANSPYLORIC PLANE...

ABDOMEN 1: Digestive System, Anterior Abdominal Wall & Inguinal Region John Vincent O. Estrada, MD | 20 NOVEMBER 2023 OUTLINE I. ANTERIOR ABDOMINAL WALL A. BOUNDARIES B. ABDOMINAL PLANES 1. TRANSPYLORIC PLANE 2. SUBCOSTAL PLANE 3. INTERCRISTAL PLANE 4. TRANSTUBERCULAR PLANE 5. MIDCLAVICULAR PLANE C. REGIONS OF ABDOMINAL CAVITY D. CUTANEOUS NERVE SUPPLY E. SUPERFICIAL FASCIA 1. CAMPER’S FASCIA 2. SCARPA’S FASCIA F. DEEP FASCIA G. SUPERFICIAL VEINS OF ANTERIOR ABDOMINAL WALL H. LINEA ALBA I. ANTEROLATERAL ABDOMINAL MUSCLES 1. EXTERNAL OBLIQUE 2. INTERNAL OBLIQUE 3. TRANSVERSUS ABDOMINIS 4. RECTUS ABDOMINIS 5. PYRAMIDALIS J. NEUROVASCULAR PLANE OF ANTERIOR ABDOMINAL WALL K. RECTUS SHEATH L. ANASTOMOSIS BETWEEN SUPERIOR AND INFERIOR EPIGASTRIC ARTERIES M. INTERNAL SURFACE OF ANTERIOR ABDOMINAL WALL N. TRANSVERSALIS FASCIA O. EXTRAPERITONEAL FAT P. PARIETAL PERITONEUM Q. LAYERS OF ANTERIOR ABDOMINAL WALL II. INGUINAL REGION A. INGUINAL TRIANGLE B. INGUINAL CANAL 1. CONTENTS OF INGUINAL CANAL 2. WALLS OF INGUINAL CANAL C. ABDOMINAL HERNIA D. INDIRECT INGUINAL HERNIA E. DIRECT INGUINAL HERNIA F. FEMORAL HERNIA ANTERIOR ABDOMINAL WALL BOUNDARIES OF ANTEROLATERAL ABDOMINAL WALL Superior: cartilages of the 7th-10th ribs and the xiphoid process of the sternum Inferior: inguinal ligament and the superior margins of the anterolateral aspects of the pelvic girdle (iliac crests, pubic crests, and pubic symphysis). For more general clinical descriptions, four quadrants of the abdominal cavity (right and left upper and lower quadrants) are defined by two readily defined planes: 1. transverse transumbilical plane- passing through the umbilicus (and typically the intervertebral disc between the L3 and L4 vertebrae), dividing it into upper and lower halves, and ANATOMY Aum, Caperas, Clemente, Fajardo, Mallanao, Montenegro, Paler, Peregrina, Osmeña, Ramos, Shdaefat, Page 1 of 11 4.00 Santos, Sy  2. vertical median plane- passing longitudinally through the body, dividing it into right and left halves. ABDOMINAL PLANES The horizontal transpyloric plane passes through the tips of the ninth costal cartilages on the two sides. It lies at the level of the body of the 1st lumbar vertebra. This plane passes through the pylorus of the stomach, the duodenal junction, the neck of the pancreas, and the hila of The regions are delineated by four planes: two sagittal the kidneys. (vertical) and two transverse (horizontal) planes. The horizontal subcostal plane joins the lowest point of The two vertical planes are the midclavicular planes. the costal margin on each side - that is, the 10th costal The two horizontal planes are the: cartilage. ○ subcostal plane This plane lies at the level of the 3rd lumbar vertebra. ○ transtubercular plane. The horizontal intercristal plane passes across the It is important to know what organs are located in each highest points on the iliac crests and lies on the level of abdominal region or quadrant so that one knows where the body of the 4th lumbar vertebra. to auscultate, percuss, and palpate them and to record This is commonly used as a surface landmark when the locations of findings during a physical examination. performing a lumbar spinal tap. The horizontal transtubercular plane (intertubercular CUTANEOUS NERVE SUPPLY plane) joins the tubercles on the iliac crests and lies at the level of the 5th lumbar vertebra The cutaneous nerve supply to the anterior abdominal The two vertical lines or sagittal planes are the wall is derived from the: midclavicular planes that pass from the midpoint of the ○ anterior rami of the lower six thoracic clavicles (approximately 9 cm from the midline) to the ○ 1st lumbar nerves. mid-inguinal points, midpoints of the lines joining the The thoracic nerves are the lower five intercostal and anterior superior iliac spine and the pubic tubercles (in the subcostal nerves; the 1st lumbar nerve is Moore) or the symphysis pubis (Snell) on each side. represented by the iliohypogastric and the ilioinguinal Nine regions of the abdominal cavity are used to nerves. describe the location of abdominal organs, pains, or The dermatome of T7 is located in the epigastrium over pathologies. the xiphoid process. These are the: The dermatome of T10 includes the umbilicus and that ○ Right hypochondriac region of L1 lies just above the inguinal ligament and the ○ Epigastric region symphysis pubis. ○ Left hypochondriac region ○ Right lumbar region ○ Umbilical region ○ Left lumbar region ○ Right iliac region ○ Hypogastric region ○ Left iliac region ANATOMY Aum, Caperas, Clemente, Fajardo, Mallanao, Montenegro, Paler, Peregrina, Osmeña, Ramos, Shdaefat, Page 2 of 11 4.00 Santos, Sy  SUPERFICIAL FASCIA The superficial fascia is divided into: ○ superficial fatty layer (Camper's fascia) ○ deep membranous layer (Scarpa’s fascia). The fatty layer is continuous with the superficial fat over the rest of the body and may be extremely thick (3 in./8 cm or more in obese patients). In the scrotum, the fatty layer of the superficial fascia is represented as a thin layer of smooth muscle, the dartos muscle. The membranous layer of the superficial fascia persists as a separate layer. The membranous layer is thin and fades out laterally and above, where it becomes continuous with the superficial fascia of the back and the thorax, respectively. Inferiorly, the membranous layer passes onto the front of the thigh, where it fuses with the deep fascia one fingerbreadth below the inguinal ligament. In the midline inferiorly, the membranous layer of fascia is not attached to the pubis but forms a tubular sheath for the penis (or clitoris). Below in the perineum, it enters the wall of the scrotum (or labia majora). From there, it passes to be attached on each side to the margins of the pubic arch; it is here referred to as Colles’ VEINS OF ANTERIOR ABDOMINAL WALL fascia. Posteriorly, it fuses with the perineal body and the SUPERFICIAL VEINS posterior margin of the perineal membrane. The superficial veins form a network that radiates out from the umbilicus. The thoraco-epigastric vein may exist and drain above into the axillary vein via the lateral thoracic vein and, below, into the femoral vein via the superficial epigastric vein and great saphenous vein. DEEP FASCIA The deep fascia in the anterior abdominal wall is merely a thin layer of connective tissue covering the muscles; it lies immediately deep to the membranous layer of superficial fascia. A few small veins, the periumbilical veins, connect the network through the umbilicus and along the ligamentum teres to the portal vein. This forms an important portal-systemic venous anastomosis. LINEA ALBA A fibrous band that separates the rectus sheath into two sides of the anterior abdominal wall. ANATOMY Aum, Caperas, Clemente, Fajardo, Mallanao, Montenegro, Paler, Peregrina, Osmeña, Ramos, Shdaefat, Page 3 of 11 4.00 Santos, Sy  This extends from the xiphoid process down to the RECTUS ABDOMINIS symphysis pubis and is formed by the fusion of the aponeuroses of the lateral muscles of the two sides. Compresses the abdominal contents and flexes the Wider above the umbilicus, it narrows down below the vertebral column; acts as accessory muscle of expiration. umbilicus to be attached to the symphysis pubis. Nerve supply: Lower six thoracic nerves. ANTEROLATERAL ABDOMINAL MUSCLES PYRAMIDALIS Tenses the linea alba EXTERNAL OBLIQUE The nerve supply is the 12th thoracic nerve. Supports abdominal contents; compresses abdominal As a group, the muscles of the anterolateral contents; assists in flexion and rotation of the trunk; abdominal wall: assists in forced expiration, micturition, defecation, parturition, and vomiting. ○ Form a strong expandable support for the Nerve supply: lower six thoracic nerves and anterolateral abdominal wall. iliohypogastric and ilioinguinal nerves (L1). ○ Support the abdominal viscera and protect them from most injuries. INTERNAL OBLIQUE ○ Compresses the abdominal contents to maintain or increase the intra-abdominal pressure and, in Supports abdominal contents; compresses abdominal doing so, opposes the diaphragm (increased contents; assists in flexion and rotation of the trunk; intra-abdominal pressure elevates the relaxed assists in forced expiration, micturition, defecation, diaphragm). parturition, and vomiting. ○ Produce the force required for defecation, Nerve supply: lower six thoracic nerves and micturition, vomiting, and parturition. iliohypogastric and ilioinguinal nerves (L1). ○ Move the trunk and help to maintain posture. ○ Assist the diaphragm during inspiration by TRANSVERSE ABDOMINIS relaxing as the diaphragm descends so that the abdominal viscera can be accommodated. Compresses abdominal contents Nerve supply: lower six thoracic nerves and NEUROVASCULAR PLANE OF ANTERIOR iliohypogastric and ilioinguinal nerves (L1). ABDOMINAL WALL Between the internal oblique and the transversus abdominis muscles is the neurovascular plane of the anterolateral abdominal wall, which contains the nerves and arteries supplying the anterolateral abdominal wall. ANATOMY Aum, Caperas, Clemente, Fajardo, Mallanao, Montenegro, Paler, Peregrina, Osmeña, Ramos, Shdaefat, Page 4 of 11 4.00 Santos, Sy  The posterior rectus sheath is absent, and the rectus abdominis lies in contact with the transversalis fascia. Where the aponeuroses forming the posterior rectus sheath pass in front of the rectus abdominis at the level RECTUS SHEATH of the anterior superior iliac spine, the posterior rectus sheath has a free, curved lower border called the A long fibrous sheath that encloses the rectus arcuate line (semicircular line of Douglas). abdominis muscle and pyramidalis muscle and contains At this site, the inferior epigastric vessels enter the rectus the anterior rami of the lower six thoracic nerves and the sheath and pass upward to anastomose with the superior superior and inferior epigastric vessels and lymph epigastric vessels. vessels. The rectus sheath is considered at three levels: Above the costal margin, the anterior rectus sheath is formed by the aponeurosis of the external oblique. There is no posterior rectus sheath; the rectus abdominis rests on the 5th, 6th, and 7th costal cartilages and the intercostal spaces. The posterior rectus sheath is not attached to the rectus abdominis muscle. The anterior rectus sheath is firmly attached to it by the muscle’s tendinous intersections. Between the costal margin and the level of the anterior ANASTOMOSIS BETWEEN SUPERIOR AND and superior iliac spine, the aponeurosis of the internal INFERIOR EPIGASTRIC ARTERIES oblique splits to enclose the rectus abdominis; the external oblique aponeurosis is directed in front of the The superior and inferior epigastric arteries make an muscle, and the transversus abdominis aponeurosis is anastomosis with each other and supply the muscles of directed behind the muscle. the anterior abdominal wall. Between the level of the anterior superior iliac spine and The anastomosis forms a collateral circulation between the pubis, the aponeuroses of all the three muscles form the subclavian artery via the internal thoracic artery, and the anterior rectus sheath. the external iliac artery. ANATOMY Aum, Caperas, Clemente, Fajardo, Mallanao, Montenegro, Paler, Peregrina, Osmeña, Ramos, Shdaefat, Page 5 of 11 4.00 Santos, Sy  INTERNAL SURFACE OF ANTERIOR ABDOMINAL WALL LAYERS OF THE ANTERIOR ABDOMINAL WALL Skin The infra-umbilical part of this surface exhibits five Camper’s Fascia umbilical peritoneal folds passing toward the umbilicus, Scarpa’s Fascia one in the median plane and two on each side. External oblique muscle and aponeurosis The median umbilical fold extends from the apex of Internal oblique and aponeurosis the urinary bladder to the umbilicus and covers the Transversus abdominis muscle and aponeurosis median umbilical ligament, a fibrous remnant of the Transversalis fascia urachus that joined the apex of the fetal urinary bladder Extraperitoneal fat to the umbilicus. Parietal peritoneum Two medial umbilical folds, lateral to the median umbilical fold, cover the medial umbilical ligaments, formed by occluded parts of the umbilical arteries. INGUINAL REGION Two lateral umbilical folds, lateral to the medial umbilical folds, cover the inferior epigastric vessels and therefore bleed if cut. TRANSVERSALIS FASCIA The transversalis fascia is a thin layer of fascia that lines the transversus abdominis muscle and is continuous with a similar layer lining the diaphragm and the iliacus muscle. The femoral sheath for the femoral vessels in the lower limbs is formed from the transversalis fascia. The inguinal region (groin) is an important area surgically because it is the site of inguinal hernias.​ These hernias occur in both sexes but are more EXTRAPERITONEAL FAT common in males.​ The extraperitoneal fat is a thin layer of connective tissue that contains a variable amount of fat and lies INGUINAL TRIANGLE between the transversalis fascia and the parietal The inguinal triangle (Hesselbach’s triangle) is bounded:​ peritoneum. ○ Superolateral: Inferior epigastric artery​ ○ Medial: Rectus abdominis​ PARIETAL PERITONEUM ○ Inferior: Inguinal ligament (Poupart’s ligament) The walls of the abdominal cavity are lined with parietal The inguinal triangle is the site of a direct inguinal peritoneum. hernia. - This is a thin serous membrane and is continuous below with the parietal peritoneum lining the pelvis. ANATOMY Aum, Caperas, Clemente, Fajardo, Mallanao, Montenegro, Paler, Peregrina, Osmeña, Ramos, Shdaefat, Page 6 of 11 4.00 Santos, Sy  INGUINAL CANAL The inguinal canal is an oblique passage through the lower part of the anterior abdominal wall.​ It lies parallel to and immediately above the inguinal ligament. The inguinal canal is about 4 cm (1.5 in) long in the adult and extends from the deep inguinal ring, a hole in the transversalis fascia, downward and medially to the WALLS OF INGUINAL CANAL superficial inguinal ring, a hole in the aponeurosis of the external oblique muscle. CONTENTS OF INGUINAL CANAL The main content of the inguinal canal is the: ○ Spermatic cord in males ○ Round ligament of the uterus in females These are functionally and developmentally distinct structures that occur in the same location.​ The inguinal canal also contains: ○ Blood and lymphatic vessels ○ Ilio-inguinal nerve ○ Genital branch of the genitofemoral nerve in both sexes. Anterior Wall: External oblique aponeurosis, reinforced laterally by the origin of the internal oblique from the inguinal ligament ANATOMY Aum, Caperas, Clemente, Fajardo, Mallanao, Montenegro, Paler, Peregrina, Osmeña, Ramos, Shdaefat, Page 7 of 11 4.00 Santos, Sy  Posterior Wall: Conjoint tendon medially, transversalis INDIRECT INGUINAL HERNIA fascia laterally Conjoint Tendon (inguinal falx): Located in the inferior part of the anterior abdominal wall and is formed from the common aponeurosis of the internal oblique and transversus abdominis, although they can be separated - The fibers turn inferiorly and insert into the pubic crest at the pectineal line immediately deep to the superficial inguinal ring Superior Wall or Roof: Arching lowest fibers of the internal oblique and transversus abdominis muscles Inferior Wall or Floor: Upturned lower edge of the inguinal ligament and at its medial end, the lacunar ligament or also called as Gimbernat’s ligament Inguinal Canal is the site of an indirect inguinal hernia ABDOMINAL HERNIA It is the remains of the processus vaginalis and therefore is congenital in origin. It is more common than a direct inguinal hernia. It is much more common in males than females. It is more common on the right side. It is more common in children and young adults. The hernial sac enters the inguinal canal through the deep inguinal ring and lateral to the inferior epigastric vessels. The neck of the sac is narrow. The hernial sac may extend through the superficial inguinal ring above and medial to the pubic tubercle. The hernial sac may extend down into the scrotum or labium majus. DIRECT INGUINAL HERNIA A hernia is the protrusion of part of the abdominal contents beyond the normal confines of the abdominal wall. It consists of three parts: ○ sac ○ contents of the sac ○ coverings of the sac The hernial sac is a pouch (diverticulum) of peritoneum and has a neck and a body. The hernial contents may consist of any structure found within the abdominal cavity and may vary from a small piece of omentum to a large viscus such as the kidney. The hernial coverings are formed from the layers of the abdominal wall through which the hernial sac passes. It is common in old men with weak abdominal muscles and is rare in women. ANATOMY Aum, Caperas, Clemente, Fajardo, Mallanao, Montenegro, Paler, Peregrina, Osmeña, Ramos, Shdaefat, Page 8 of 11 4.00 Santos, Sy  The hernial sac bulges forward through the posterior REFERENCES wall of the inguinal canal medial to the inferior epigastric vessels. Lecturer’s Powerpoint. The neck of the hernial sac is wide. Estrada, (2023). Clinical Anatomy by Systems. FEMORAL HERNIA Snell, R. (2007). Clinical Anatomy by Systems. Philadelphia: Lippincott Williams & Wilkins. Atlas of Human Anatomy. Netter, F. (2014). Atlas of Human Anatomy (7th edition). Philadelphia PA: Elsevier Inc. It is a protrusion of the abdominal parietal peritoneum down through the femoral canal to form the hernial sac. It is more common in women than in men The neck of the hernial sac lies below and lateral to the pubic tubercle The neck of the hernial sac lies at the femoral ring and at that point is related anteriorly to the inguinal ligament (Cooper’s ligament) and the pubis, laterally to the femoral vein, medially to the sharp free edge of the lacunar ligament. ANATOMY Aum, Caperas, Clemente, Fajardo, Mallanao, Montenegro, Paler, Peregrina, Osmeña, Ramos, Shdaefat, Page 9 of 11 4.00 Santos, Sy  APPENDIX SGD QUESTIONS: ring and lateral to the 1. Explain what is meant by the term “direct inguinal inferior hernia.” Protrusion of abdominal contents through the epigastric transversalis fascia within Hesselbach's triangle. vessels. The ○ HESSELBACH’S TRIANGLE neck of the BOUNDARIES sac is narrow.. Superolateral: Inferior epigastric The hernial vessels Medial: Rectus sheath sac may Inferior: Inguinal ligament extend 2. How does direct inguinal hernia differentiate from through the indirect inguinal hernia? superficial inguinal ring DIRECT INDIRECT above and It is common It is the medial to the in old men remains of the pubic with weak processus tubercle. abdominal vaginalis and The hernial muscles and therefore is sac may is rare in congenital in extend down women. origin. into the The neck of It is more scrotum or the hernial common than labium majus. sacks wide a direct The hernial inguinal sac bulges hernia. forward It is much through the more common posterior wall in males than of the inguinal females. canal medial It is more to the inferior common on epigastric the right side. vessels It is most common in children and young adults. The hernial sac enters the inguinal canal through the deep inguinal ANATOMY Aum, Caperas, Clemente, Fajardo, Mallanao, Montenegro, Paler, Peregrina, Osmeña, Ramos, Shdaefat, Page 10 of 11 4.00 Santos, Sy 3. Embryological basis of direct and indirect inguinal hernia An indirect inguinal hernia is related to a defect in the lower abdominal wall that is present at birth. Unlike indirect inguinal hernia, a direct inguinal hernia has no embryological basis. It is related to a weak area in the inguinal canal that develops gradually because of continuous stress on the muscles. It is caused by connective tissue degeneration of the abdominal muscles, which causes weakening of the muscles during the adult years. Normally, most of the processus vaginalis obliterates before birth, except for the distal part that forms the tunica vaginalis of the testes. The peritoneal part of the hernial sac of an indirect inguinal hernia is formed by the persisting processus vaginalis. If the entire stalk of the processus vaginalis persists, the hernia extends into the scrotum superior to the testis, forming a complete indirect inguinal hernia ANATOMY Aum, Caperas, Clemente, Fajardo, Mallanao, Montenegro, Paler, Peregrina, Osmeña, Ramos, Shdaefat, Page 11 of 11 4.00 Santos, Sy