Anterior abdominal wall , Rectus sheath and Inguinal.pptx

In this detailed lecture note, we embark on a comprehensive journey through the complex and crucial anatomy of the abdominal wall. The abdominal wall is not just a physical barrier; it is a dynamic structure with multiple layers, muscles, and intricate structures that play a fundamental role in protecting our internal organs, providing support, and enabling various bodily functions.

We will delve deep into the layers of the abdominal wall, understanding the significance of each component - from the outermost skin to the innermost peritoneum. Through detailed illustrations, diagrams, and explanations, you will gain a profound insight into the anatomical intricacies of this region.

Moreover, this lecture note provides valuable insights into the clinical relevance of the abdominal wall. Learn about common medical conditions and surgical procedures related to the abdominal wall, including hernias, trauma, and abdominal wall reconstruction. Whether you are a medical student, healthcare professional, or simply intrigued by the wonders of the human body, this resource will enrich your knowledge and understanding of this vital anatomical structure.

Join us on this educational journey as we unravel the mysteries of the abdominal wall, exploring its anatomy, functions, and clinical significance. Whether you're studying medicine, pursuing a career in healthcare, or just eager to expand your knowledge, this lecture note is a valuable resource for anyone interested in the fascinating world of human anatomy."

1. Anterior abdominal wall , Rectus sheath and Inguinal canal Dr Sam Chime

2. The abdominal wall surrounds the abdominal cavity , providing it with flexible coverage and protecting the internal organs from damage. It is bounded superiorly by the xiphoid process and costal margins, posteriorly by the vertebral column and inferiorly by the pelvic bones and inguinal ligament .

3. FEATURES OF THE ABDOMINAL WALL Multiple muscular and fascial layers Form a sturdy, protective musclo fascial layer that protects the visceral organs Encloses the abdominal cavity Holds the major visceral organs that include stomach, intestine, liver, and biliary system, pancreas, spleen, kidneys, ureters, and suprarenal glands Divided into as many as 9 separate regions

4. Four quadrants , which are divided by the horizontal transumbilical and vertical median planes. The four resulting areas are called right upper, left upper, right lower and left lower quadrants.

5. Nine abdominopelvic regions , which are divided horizontally by the superior subcostal plane, which passes right under the costal margins of the 10th ribs , and the inferior intertubercular plane, which connects the tubercules of the iliac crest. Vertically they are divided by the two midclavicular planes which pass through the midpoint of each clavicle and halfway between the pubic symphysis and the anterior superior iliac spine. The four planes create nine abdominal regions as you see in the picture: hypochondriac (right, left) and epigastric regions superiorly, flanks (right, left) and umbilical region in the middle, groin (right, left) and hypogastric region inferiorly.  

6.   The  skin is the most superficial layer of the anterior abdominal wall. In pregnant women, obese people and those with abdominal distention, it can contain elongated lines called stretch marks or striae distensae , usually situated in the umbilical and hypogastric regions. The superficial fascia is located just below the skin and consists of connective tissue . In the anterior abdominal wall, superior to the umbilicus, it is similar and continuous to the superficial fascia of the body and is made up mostly of one layer. However, inferior to the umbilicus, it is divided into two layers:

7. Superficial Camper’s fascia , which is a thicker fatty layer that can have a variable degree of thickness. For example, it is greatly increased in obese individuals and very thin in people with low body fat. Deep Scarpa's fascia , which is a thinner and denser membranous layer overlying the muscle layer of the abdominal wall. It is firmly attached to the linea alba and pubic symphysis and fuses with the fascia lata (deep fascia of the thigh) right below the inguinal ligament. 

8. In men, the Camper’s fascia continues over the penis and blends with the Scarpa’s fascia to form the superficial fascia of the penis. The latter extends further on into the scrotum , where it contains smooth muscle fibers and becomes the dartos fascia . Scarpa’s fascia continues into the perineum to form the superficial fascia of the perineum, called Colles ’ fascia . In women it continues into the labia majora and anterior perineum.

9. MUSCLES Lateral flat muscle group situated on either side of the abdomen, which includes three muscles: external oblique , internal oblique and transversus abdominis .  Anterior vertical muscles situated bilaterally to the median fibrous structure called linea alba. They are called rectus abdominis and pyramidalis muscles.

10. External abdominal oblique muscle Origin:  External surface of ribs 5-12 Insertion:  fleshy fibres into ant 2/3 of outer lip of iliac crest broad aponeurosis into linea alba Innervation:  Lower 6 thoracic nerves Function: Bilateral contraction - Trunk flexion, Compresses abdominal viscera, Expiration Unilateral contraction - Trunk lateral flexion (ipsilateral), Trunk rotation (contralateral) IMPORTANCE: lower border is thickened & folded to form inguinal ligament extending from ant sup iliac spine to pubic tubercle

11. The external oblique muscle is a lateral flat muscle that courses from the 5th to the 12th rib ventromedially until the anterior layer of the rectus sheath . At its origin, it is tightly connected with the serratus anterior and latissimus dorsi muscles. Ventrally the external oblique muscle builds a large aponeurosis which extends medially to the linea alba and caudally to the iliac crest and the pubic bone. Its inferior margin forms the inguinal ligament.

12. Internal abdominal oblique muscle Origin:  Lateral 2/3 of inguinal ligament & anterior 2/3iliac crest Insertion:  muscle into the lower 3-4 ribs broad aponeurosis into 7,8 & 9 costal cartilages linea alba & pubic crest Innervation:  Lower 6 thoracic nerves and first lumbar nerves Function: Bilateral contraction - Trunk flexion, Compresses abdominal viscera, Expiration Unilateral contraction - Trunk lateral flexion (ipsilateral), Trunk rotation (ipsilateral)

13. Originating from the thoracolumbar fascia , iliac crest and iliopectineal arch, the internal oblique muscle inserts cranially at the lower costal cartilages and ventrally at the linea alba. In men, caudal fibers extend to the spermatic cord and merge to form the cremaster muscle . The semilunar lines ( linea semilunaris ) are formed by the divisions of the internal oblique aponeurosis and correspond with the lateral margins of the rectus abdominis muscle. They extend from the tip of the 9th costal cartilage to the pubic tubercle. 

14. Transversus abdominis muscle Origin:  lateral 1/3 of inguinal ligament, ant 2/3 iliac crest, lower 6 costal cartilages Insertion: Linea alba Innervation:  Lower 6 thoracic & first lumbar nerves Function: Bilateral contraction - Compresses abdominal viscera, Expiration Unilateral contraction - Trunk rotation (ipsilateral)

15. The transversus abdominis muscle is the deepest of the three lateral abdominal muscles. It runs from the inner surface of the lower costal cartilages, thoracolumbar fascia, iliopectineal arch and iliac crest horizontally to the linea alba. Caudal fibers are also involved in the formation of the cremaster muscle. The transversalis fascia separates the anterior abdominal wall from the extraperitoneal fat. Posteriorly, the transversalis fascia is continuous with the thoracolumbar fascia.

16. The external oblique muscle is the outermost muscle, whose fibers run inferomedially . Right beneath it sits the internal oblique muscle whose fibers run superomedially . The most profound lateral muscle is the transversus abdominis which consists of horizontal fibers. The transverse fascia is located below the transversus abdominis. 

17. RECTUS SHEATH The aponeuroses of these muscles form the rectus sheath , which is divided into anterior and posterior layers. The latter is only present in the superior three quarters of the rectus sheath and its inferior limit is demarcated by the horizontal arcuate line . This is where the inferior epigastric artery and vein perforate the rectus abdominis. Above the arcuate line the anterior layer consists of the aponeuroses of the internal and external oblique , while the posterior layer is made up the aponeuroses of the internal oblique and transversus abdominis muscles. Below the arcuate line the anterior layer of the rectus sheath is built by the aponeuroses of all three lateral abdominal muscles whereas the posterior layer is only covered by the transverse fascia and the peritoneum .

18. FORMATION Above the costal margin Anterior wall : external oblique aponeurosis Posterior wall: deficient Between the costal margin and arcuate line Anterior wall : ext obliq aponeurosis & ant lamina of int oblique Post wall : post lamina of int obliq & aponeurosis of transversus abdominis Below the arcuate line Ant wall: aponeuroses of all 3 muscles Post wall: deficient

19. CONTENTS OF RECTUS SHEATH 2 Muscles : Rectus abdominis & pyramidalis 2 arteries : superior & inferior epigastric arteries 2 veins : superior & inferior epigastric veins 6 nerves : 5 lower intercostal & subcostal nerves FUNCTIONS Maintains strength to anterior abdominal wall Checks bowing of rectus muscle

20. Anterior abdominal wall muscles The  anterior muscle group  includes the rectus abdominis and pyramidalis muscles. These are almost completely enveloped by the thick rectus sheath formed by the aponeuroses of the lateral abdominal muscles. The only exception is the posterior side of the lowest fourth of the rectus abdominis muscle, below the arcuate line , which is covered only by the transversalis fascia and parietal peritoneum. Immediately deep to the rectus sheath is the transversalis fascia, below which lie the two deepest layers of the abdominal wall: extraperitoneal fat and peritoneum

21. Rectus abdominis muscle Origin:  Pubic symphysis, Pubic crest  Insertion:  Xiphoid process, Costal cartilages of ribs 5-7 Innervation:  Intercostal nerves (T7-T11), Subcostal nerve (T12)  Function:  Trunk flexion, Compresses abdominal viscera, Expiration 

22. The rectus abdominis muscles are a pair of long, straight muscles which run vertically on either side of the anterior abdominal wall. They are separated by the linea alba. The term rectus abdominis means “straight abdominal” in Latin, indicating that the muscle fibers run in a straight vertical line through the abdominal region of the body. Each muscle consists of a string of four fleshy muscular bodies connected by three narrow bands of tendon known as tendinous intersections . The shape of these segments is often visible through the superficial fascia and skin in those with low body fat, resulting in a ‘six-pack’ shape.

23. Pyramidalis muscle Origin:  Pubic symphysis, Pubic crest Insertion:  Linea alba Innervation:  Subcostal nerve (T12) Function:  Tenses linea alba

24. The pyramidalis muscle is a small triangular muscle lying anterior to the rectus abdominis muscle that can be absent in approximately 20% of the population. It is contained in the rectus sheath and originates from the bony pelvis , where it is attached to the pubic symphysis and pubic crest through tendinous fibers. The fibres run superiorly and medially to insert into the linea alba, tensing it during muscular contractions.

25. Mnemonic  Just remember TIRE P ump T ransversus abdominis I nternal oblique R ectus abdominis E xternal oblique P yramidalis

26. ARTERIAL SUPPLY The superficial branches include: Musculophrenic artery , which is a branch from the internal thoracic artery . It supplies the superior part of the superficial anterolateral abdominal wall. Superficial epigastric artery and lateral to it the superficial circumflex iliac artery . They are branches of the femoral artery and supply the inferior part of the wall.

27. The deep layers of the anterolateral abdominal wall are supplied by the following: Superior epigastric artery , a terminal branch of the internal thoracic artery. It runs in the rectus sheath behind the rectus muscle and supplies the superior part of the wall.  Inferior epigastric artery and deep circumflex iliac artery , both branches from the external iliac artery , supply the inferior part of the wall. The inferior epigastric artery enters the rectus sheath after piercing the fascia transversalis and ends by anastomosing with the superior epigastric artery. The tenth and eleventh intercostal arteries and subcostal artery supply the lateral part of the abdominal wall.

28. There is a network of superficial veins that radiate out from the umbilicus and a few small paraumbilical veins which interconnect the network. The deep veins follow the arteries of the same name. The skin and peritoneum of the anterolateral abdominal wall are innervated by the T7 to L1 spinal nerves , which run in an inferomedial direction. They give off lateral and anterior cutaneous branches along their course. Muscles of the anterior abdominal wall are supplied by lower six thoracic nerves, the iliohypogastric nerve and the ilioinguinal nerve .

29. INGUINAL CANAL It is a musculo aponeurotic tunnel extending from deep inguinal ring to the superficial inguinal ring It is about 4cm in length It is directed downwards, forwards& medially In females it is narrow hence inguinal hernias are less common This canal is as a result of the erect posture of man not found in other primates CONTENTS Spermatic cord/round ligament of uterus Illioinguinal nerve

30. Inguinal region   The anterior abdominal wall has naturally occurring paired canals in the lateral lower regions known as inguinal canals . These oblique intramuscular tunnels may range from 3 to 5 cm long in an adult. They serve as a conduit that allows the passage of the male gonads from their intra-abdominal point of origin to their final destination in the scrotal sac. Each inguinal canal originates superolaterally at the deep inguinal ring located at the medial half of the inguinal ligament of Poupart . The canal then terminates at the superficial inguinal ring , which is found about 1 cm superolateral to the pubic tubercle. 

31. n females, the round ligament of the uterus passes through each canal. Male inguinal canals convey the spermatic cord , which contains the vas deferens , its related neurovasculature , lymphatics and connective tissue. Superficial and deep inguinal rings impose weak points in the abdominal wall, creating a predisposition to inguinal hernias

32. INGUINAL CANAL The inguinal canal is an oblique intramuscular slit that may range from 3 – 5 cm long in an adult. It originates superolaterally at the deep inguinal ring . This opening occurs at the medial half of the inguinal ligament of Poupart at the midpoint between the anterior superior iliac spine (ASIS) and the pubic tubercle ; also known as the midpoint of the inguinal ligament . Please note that this is different from the mid inguinal point, which is the midpoint between the ASIS and pubic symphysis. However, the deep inguinal ring can also be found 1.25 cm above the mid inguinal point.

33. The canal then terminates at the superficial inguinal ring , which can be found about 1 cm superolateral to the pubic tubercle. Also, the superficial inguinal ring is bordered medially by the inferolateral border of rectus abdominis , laterally by the inferior epigastric vessels and inferiorly by the medial third of the inguinal ligament . These three borders are often referred to as Hesselbach's (inguinal) triangle and serve as an important landmark for the superficial ring.

34. BORDERS The various layers of tissue of the lower abdominal wall play an important role in the formation of the inguinal canal. The canal has four borders – a roof and a floor, and anterior and posterior walls. It should be noted that the deep ring and thinnest part of the postural wall (i.e. the lateral aspect) is supported by the thickest part of the anterior wall. Similarly, the reflected inguinal ligament and conjoint tendon provide additional support to the posterior wall immediately behind the superficial inguinal ring.

35. simple mnemonic to recall the borders of the inguinal canal is MALT : The roof is formed by M uscles (internal oblique and transversus abdominis ). The anterior wall is derived from A poneuroses (internal and external oblique aponeuroses). The floor is formed by L igaments (inguinal and lacunar ligaments). The posterior wall is formed by the conjoint T endon and T ransversalis fascia

36. DEEP INGUINAL RING The initial opening of the inguinal canal is located at the midpoint of the inguinal ligament, and is referred to as the deep (lateral) inguinal ring. It is an oval defect in the transversalis fascia , which is widest along the vertical axis of the opening. The defect is significantly larger in males than in females, as it is meant to accommodate the passage of the testes into the scrotal sac.

37. The deep ring is lateral to the inferior epigastric vessels as well as the interfoveolar ligament (fibrous band extending from the lower margin of the transversalis fascia to the superior pubic ramus) when they are present. The deep ring may also function as a valve whenever it is made taut by contractions of the internal oblique muscle in response to raised intra abdominal pressure

38. ANTERIOR WALL Skin Superficial fascia Aponeurosis of ext oblique Lateral1/3 of the wall is covered by int oblique

39. FLOOR It is formed by grooved upper surface of inguinal ligament, the posterior margin of which fuses with fascia transversalis Medially , the floor is formed by upper surface of lacunar ligament

40. ROOF It is formed by arched fibres of internal oblique & transversus abdominis muscles

41. POSTERIOR WALL Like the internal oblique muscle, the transversus abdominis muscle also (albeit, partly) arises from the lateral third of the inguinal canal and curves inferomedially to join the internal oblique aponeurosis as both structures insert at the pectineal line and pubic crest as the conjoint tendon . This robust tendon provides additional support to the medial third of the posterior abdominal wall. The lateral part of the posterior wall is also supported by the in-rolled part of the inguinal ligament, alongside the transversalis fascia POSTERIOR WALL Formed by transversalis fascia And the conjoint tendon

42. Constituents of spermatic cord Vas deferens Arteries : testicular artery cremasteric artery artery of vas Veins : pampiniform plexus Lymphatics of testis Nerves : A genital branch of genitofemoral nerve, B testicular plexus of sympathetic nerves T10, C sympathic plexus around the artery of vas Areolar tissue

43. SUPERFICIAL INGUINAL RING The medial opening of the inguinal canal occurs within Hesselbach's triangle and is known as the superficial inguinal ring. It is a ‘V’ shaped defect in the external oblique aponeurosis , whose apex is parallel with the deep aponeurotic fibres . The side walls of the superficial ring are formed from the aponeurotic crura of the external oblique. The lateral crus is thicker than the medial one, as the former is reinforced by the inguinal ligament . The medial crus inserts at the pubic crest, while the lateral crus attaches to the pubic tubercle. There is also grooving of the lateral crus (not observed in females) that provides an atraumatic area for the spermatic cord to lay. The base of the triangular opening falls along the pubic crest. While there is variability in the size of the ring among individuals, it is also markedly larger in males than in females in order to accommodate testicular descent. 

44. CONTENTS The contents of the inguinal canal vary dramatically between males and females; as there are significantly less structures that traverse the female inguinal canal. The ilioinguinal (arising from T12 and L1) and genital branch of the genitofemoral nerves (arising from L2) are the only structures that are found in both male and female inguinal canals. Note that the ilioinguinal nerve does not pass through the deep inguinal ring. Instead, it gains access to the canal by piercing its roof midway along the length of the canal . Recall that the ilioinguinal nerve provides general somatic afferent innervation to the anterior perineum and medial part of the proximal thigh . Additionally, it innervates the mons pubis and labia majora in females, as well as the base of the penile shaft and anterior scrotal sac in males. The genital branch of genitofemoral nerve participates in the general somatic efferent supply to the cremasteric muscle (in males) and general somatic afferent to the labia and scrotum .

45. INGUINAL CANAL IN FEMALES The round ligament of the uterus ( ligamentum teres uteri) passes through the inguinal canal to insert on the posterior surface of the labia majora . It is a derivative of the embryonic gubernaculum that originates at the uterotubal junction (also called the uterine horn) and functions as a uterine anchor that keeps the uterus in the anteverted position

46. INGUINAL CANAL IN MALES In the simplest form, the male inguinal canal contains only the spermatic cord in addition to the same nerves found in the female inguinal canal. However, the spermatic cord contains several layers of fascia, and houses several arteries, nerves, and other reproductive structures. These structures can be readily recalled using the mnemonic “ FANO x 3 ”, which translates to :

47. Fascia – these are continuations of the muscular and fascial layers that were traversed by the processus vaginalis during development. The deepest of the three fascial layers is the internal spermatic fascia . It is a continuation of the transversalis fascia that was pulled through the canal during development. The cremasteric muscle and fascia form the middle musculofascial layer of the spermatic cord. Both are continuations of the internal oblique muscle and fascia, respectively. Finally, the external spermatic fascia is the outermost layer, which developed from the external oblique aponeurosis.

48. Arteries – the testes maintain the arterial supply it acquired during early development. These vessels migrate caudally with the gonad during its descent. The testicular artery is responsible for supply the testes. Also historically known as the internal spermatic arteries, these vessels are direct branches of the aorta. The cremasteric artery (formerly known as the external spermatic artery) supplies the cremaster as well as other fascial layers of the spermatic cord. The artery arises from the inferior epigastric artery and traverses the inguinal canal. It also shares anastomoses with the testicular artery. The third artery in the inguinal canal is the artery of the vas (ductus) deferens . The ductus deferens is responsible for transporting sperm from the testes to the urethra. The arteries that supply it arise indirectly from the internal iliac artery via either the superior or inferior vesical arteries.

49. Nerves – in addition to the general somatic afferent and efferent nerves mentioned earlier, there are also autonomic nerves that pass through the canal to supply the gonads and associated structures. Ilioinguinal nerves Genital branch of genitofemoral nerve Autonomics Other – miscellaneous structures found in the cord include: The ductus deferens . The pampiniform plexus of veins - These vessels encircle the arterial structures and participate in a countercurrent heat exchange process that ensures that the blood being carried to the testes is at ambient temperature. Testicular lymphatics will drain lymph from the testes to the para-aortic lymph nodes.

50. MECHANISM OF INGUINAL CANAL Flap valve mechanism { obliquity of inguinal canal} Ball valve mechanism { cremaster helps plugging spermatic cord} Shutter mechanism {of internal oblique} Slit valve mechanism {approximation of 2 crura of ext oblique} Hormones These are mechanism by which the inguinal canal is closed

51. Clinical application: HERNIAS A hernia is the abnormal protrusion of viscera out of the walls of its containing cavity as a result of a weakness in these walls. There are numerous potential points of herniation throughout the body. Essentially, hernias can be considered as disorders of collagen characterized by an imbalance of the types of collagen present in the tissue or an inherent problem with collagen synthesis. 

52. Some hernias occur through areas of innate weakness – as is the case with posterior abdominal wall hernias. In other instances, the weakness exists at a hiatus that is normally used for structures to enter and exit the primary cavity. This is the case for inguinal hernias , as the deep and superficial rings are innate points of weakness Both sharp and blunt force trauma can produce areas of weakness through which viscera may herniate (e.g. acquired diaphragmatic hernia, incisional hernia). Aging is associated with progressive, widespread tissue degeneration that results in increased laxity of the ligaments. The hormonal changes associated with pregnancy also promote ligament laxity to facilitate growth and subsequent delivery of the foetus . In the absence of weakening of the abdominal wall, raised intra abdominal pressure is unlikely to produce a hernia. However, in cases where there are inherent defects (i.e. the inguinal region) the positive pressure within the abdominal cavity may cause the abdominal viscera to herniate

53. Inguinal hernias are among the most common forms of hernias that require surgical intervention. They are more commonly encountered in males than in females. These hernias may be congenital (in which case the hernia is associated with a patent processus vaginalis ) or acquired (related to an imbalance of type I and type III collagen). Smoking, weight training and lifting heavy objects have also been identified as risk factors for developing hernias. The hernia usually begins as a saccular outpouching that contains extraperitoneal tissue. Over time, as the hernia gets larger, positive pressure from the intra abdominal cavity forces peritoneum into the sac. Eventually, abdominal viscus may enter the hernia sac as well.

54. Types of hernia Direct inguinal hernia direct medial hernia direct lateral hernia Indirect inguinal hernia congenital vaginal hernia congenital funicular hernia infantile hernia bubonocele Reducible hernia Irreducible hernia Strangulated hernia

55. TYPES OF INGUINAL HERNIA Inguinal hernias that protrude through the deep inguinal ring and traverse the canal are known as indirect hernias . In these cases, the swelling is noted at the midpoint of the inguinal ligament. If the sac emerges through the superficial ring, then this is a direct inguinal hernia , with the contents emerging within Hesselbach's triangle. In either case, the contents of the hernia may pass all the way through the inguinal canal and enter the scrotal sac. This inguinoscrotal swelling should be adequately examined to determine if this is primarily a testicular or scrotal disorder, or a large inguinal hernia.

56. Other types of hernias Epigastric hernia Incisional hernia Femoral hernia Umbilical hernia

57. Difference between the direct & indirect hernia Indirect hernia direct hernia

58. On rare occasions, the herniation can occur through both the deep and superficial rings at the same time. These defects are referred to as Pantaloon hernias . The astute clinician should also examine the contralateral groin as there is a possibility that the patient may have a bilateral inguinal hernia.

59. Key facts about the inguinal canal Walls Roof -  formed by M uscles: internal oblique, transversus abdominis Anterior -  formed by  A poneuroses: internal oblique, external oblique Floor -  formed by  L igaments: inguinal ligament, lacunar ligament Posterior -  formed by  T endon and transversalis fascia Mnemonic: MALT Openings Deep inguinal ring - at the midpoint of the inguinal ligament Superficial inguinal ring - 'V' shaped defect in the external oblique aponeurosis within the Hasselbach's triangle Content Male: spermatic cord and ilioinguinal nerve Female: round ligament of the uterus and ilioinguinal nerve (*ilioinguinal nerve enters the scrotum through superficial ring, but does not travel through the inguinal canal) Spermatic cord content 3 arteries: testicular, cremasteric, ductus deferens artery 3 fascial layers: external spermatic, cremasteric, internal spermatic 3 nerves: genital branch of genitofemoral nerve, sympathetic fibers, ilioinguinal nerve  Clinical importance Herniations