Instant anatomy - Anatomy lecture made easy - Anterior abdominal wall
Anterior abdominal wall
Any incision made through the anterior abdominal wall will usually pass from the skin to subcutaneous fat tissue, to the superficial fascia, later to the deep fascia, to the muscle (dependent on the type of incision), to the transversalis fascia, to the extra peritoneal fat and finally passing the peritoneum.
Skin > subcutaneous fat tissue> superficial fascia> deep fascia > muscle> Transversalis fascia> extra peritoneal fat > peritoneum.
The skin is the outermost layer of the anterior abdominal wall. The skin consists of Langer’ line which runs in a horizontal line. The dermatomes also run in a transverse band on the skin.
Superficial fascia is divided into the Camper’s fascia or fatty layer of superficial fascia and a membranous layer of superficial fascia ( Scarpa’s fascia ). Camper‘s fascia appears to be thicker and superficial than Scarpa’s fascia. Membranous layer of superficial fascia / Scarpa’s fascia will fuse with the deep fascia inferior to the inguinal ligament on the leg. The superficial fascia will continue with Colles fascia which form a tubular sheath for clitoris and penis and as well as sac like structure that enclosing the labia and scrotum. It is prominent in children and often it is mistaken for external oblique . However it is absent laterally and above the anterior abdominal wall.
The next layer after superficial fascia is deep fascia. Deep fascia consists of vestigial layers of areolar tissue which covers the muscle underneath.
Muscle is the next layer. The amount and type of muscle present in anterior abdominal wall vary and depends on the type of incision.
In Kocher’s incision, the incision will pass through the skin, subcutaneous fat, superficial fascia and medially will pass through the anterior rectus sheath, rectus abdominus muscle and posterior rectus sheath. The incision will pass through the external oblique muscle follow later by internal oblique muscle and finally reach transversus abdominus muscle laterally. This will follow with transversalis fascia, extra peritoneal fat and peritoneum.
In Gridiron appendectomy incision, the incision will pass through the skin, subcutaneous fat, Scarpa’s fascia followed by external oblique muscle then the internal oblique muscle and finally it will reach transversus abdominus muscle ( no passing through the medial muscle layer ). This will later follow with transversalis fascia and pre peritoneal fat and finally a parietal peritoneal layer.
In a mid line laparotomy, the incision will pass through the skin, subcutaneous fat, Scarpa’s fascia, Linea Alba, transversalis fascia, extra peritoneal fat and parietal peritoneal layer with no muscle involvement.
The muscle involved generally in the anterior abdominal wall incision includes, external oblique muscle, internal oblique muscle, transversus abdominus, linea alba, rectus abdominus and pyramidalis.
EXTERNAL OBLIQUE MUSCLE
External oblique muscle is a large sheet of superficial muscle fibre of the anterior abdominal wall. It overlies the internal oblique muscle. It stands on the principle of ‘Hand in the pocket’ where the external oblique muscle runs downwards from lateral to medial position. Medially fibrous aponeurosis is formed from the muscle fibre of the external oblique. The fibrous aponeurosis form part of the anterior rectus sheath. The anterior rectus sheath will lie over the rectus abdominus muscle.
Anatomically, external oblique muscle is originated from the lower 8th ribs and inserted to the linea alba, xiphoid process, pubic crest, pubic tubercle and iliac crest. It is supplied by lower six thoracic nerves and ilioinguinal and iliohypogastric nerves (L1). The function of this muscle is to compress and support abdominal content, to help in rotating and flexing of the trunk, assists in micturition, defecation, vomiting, parturition and forced expiration.
INTERNAL OBLIQUE MUSCLE
Internal oblique muscle is the next layer of a large muscle fibre which run at the right angle to the external oblique muscle fibre. It overlies the transversus abdominus muscle fibre and lies deep to the external oblique muscle. The medial portion of the internal oblique will form fibrous aponeurosis which later splits to cover the middle portion of the muscle of rectus abdominus while forming part of posterior and anterior rectus sheath.
Anatomically, internal oblique muscle originates from the lateral two third of the inguinal ligament, iliac crest and lumbar fascia, the muscle is inserted to line alba, xiphoid process, symphysis pubis and costal cartilage as well as lower three ribs. It is supplied by lower six thoracic nerves and ilioinguinal and iliohypogastric nerves ( L1 ). The function of this muscle is to compress and support abdominal content, to help in rotating and flexing of the trunk, assists in micturition, defecation, vomiting, parturition and forced expiration.
TRANSVERSUS ABDOMINUS MUSCLE
Transversus abdominus muscle is a muscle which lies deep to the internal oblique muscle and run horizontally. Medially, the transversus abdominus muscle will form fibrous aponeurosis that lies posteriorly to the rectus abdominus muscle and form part of the posterior rectus sheath.
Anatomically, transversus abdominus muscle originating from the lateral third of the inguinal ligament, iliac crest, lumbar fascia and lower six costal cartilages. The muscle is inserted to the symphysis pubis, linea alba and xiphoid process. It is supplied by lower six thoracic nerves and ilioinguinal and iliohypogastric nerves (L1). The muscle is involved in compression of the abdominal content.
RECTUS ABDOMINUS MUSCLE
Rectus abdominus muscle lies within the rectus sheath. The rectus sheath is formed from the fibrous aponeurosis of all the muscle such as external oblique muscle, internal oblique muscle and transversus abdominus muscle ) . Rectus abdominus muscle consists of a pair of muscles which joins at the linea alba forming a wide strap that run longitudinally downward through the anterior abdominal wall. The rectus abdominus muscle will only attach to the anterior part of the rectus sheath via three points of tendinous insertion that present on the xiphisternum, halfway between the xiphisternum and umbilicus and umbilicus. These three points of tendinous insertion provide a six pack appearance of the individual, Rectus abdominus is supplied by the superior epigastric artery form the terminal branch of the internal thoracic artery and the inferior epigastric artery from the branch of the external iliac artery. The inferior epigastric artery and the superior epigastric artery will anastomose to form a connection between external iliac and subclavian system. The superior epigastric artery forms a pedicle where a TRAM flap is raised for breast construction.
Anatomically, rectus abdominus muscle originated from the pubic crest and symphysis pubis. It is inserted to the xiphoid process, fifth, sixth and seventh costal cartilage. It is supplied by lower six thoracic nerves. The Rectus abdominus muscle involved as part of accessory muscle that involved in forced expiration and flexion of the vertebral column as well as compression of abdominal content.
Line alba is a fibro tendinous raphe which runs longitudinally down the anterior abdominal wall and divides the rectus abdominus muscle into right and left parts. Linea alba an avascular and bloodless plane where mid line laparotomy is performed. Linea alba consists of fibrous aponeurosis of all the muscle (external oblique, internal oblique and transversus abdominus) which fuse interdigiting / interlocking. (Epigastric hernia may present here and protrude in this site). Any incisions will usually perform above the umbilicus mid line as the line alba is wider, thicker, bloodless as well as avascular.
Pyramdalis is a small sheet of muscle fibres, which is 4 cm long. Pyramidalis is originating from pubic crest / anterior surface of the pubis and inserted into the linea alba. It is supply by twelfth thoracic nerve and involves tensing the linea alba ( tenses the linea alba). It is located behind the anterior rectus sheath. Pyramidalis muscle lies under linea alba. It is the muscle that will be passed through during the below umbilicus / lower midline laparotomy.
ANATOMY OF THE RECTUS SHEATH
Rectus sheath is formed by the fusion of fibrous aponeurosis from external oblique , internal oblique and transversus abdominus muscles. Rectus sheath consists of anterior portion that form from the aponeurosis of external oblique and internal oblique muscles while the posterior portion of rectus sheath consists of aponeurosis form transversus abdominus and internal oblique muscles.
Rectus sheath encloses the rectus pyramidalis muscle, rectus abdominus muscle, superior and inferior epigastric arteries, segmental nerves and the segmental vessel at the level of T7 and T 12.
The arrangement rectus sheath is best described and explained based on the following orders:
-Above costal margin
-Between costal margin and umbilicus
-Below the line of Douglas.
ABOVE COSTAL MARGIN
Above costal margin, the rectus sheath consists of anterior portion of rectus sheath and absence of posterior portion of rectus sheath. This means that there are no internal oblique muscle and transversus abdominus muscle lining and aponeurosis forming the posterior portion of rectus sheath. The rectus abdominus will lie directly to the costal cartilage 5 - 7 with no posterior portion of rectus sheath.
BETWEEN COSTAL MARGIN AND UMBILICUS
Between costal margin and umbilicus , there are anterior rectus sheath and posterior rectus sheath. The anterior rectus sheath is formed from the aponeuroses of external oblique muscle and the anterior leaf of the split of the internal oblique muscle. The posterior rectus sheath consists of aponeurosis form of the transverse abdominus and the posterior leaf of the spilt of the internal oblique. At this point the rectus abdominus is attached to the anterior portion of the rectus sheath via tendinous insertion.
BELOW THE LINE OF DOUGLAS
Line of Douglas is a line 2. 5 cm below the umbilicus. At the line of Douglas the posterior rectus sheath that consists of transversus abdominus and posterior leaf of the split of internal oblique muscle will pass to the anterior portion of the rectus sheath. This will make the anterior rectus sheath consist of the fusion of the aponeurosis of external oblique, internal oblique and transversus abdominus muscles. Posterior, the rectus abdominus will lie directly to the thickened transversalis fascia which is known as ilio pubic tract.
SURFACE LANDMARKS OF THE ANTERIOR ABDOMINAL WAL
Transpyloric line at the level of first lumbar vertebrae is a line that divides the jugular notch and the symphysis pubis. Transpyloric line will pass through the termination point of spinal cord, fundus of the gallbladder, duodeno- jejunal flexures, Hilla of the kidney, pylorus and neck of the pancreas.
Subcostal line is a line that passes below the lowest rib which is at the third lumbar vertebra (L3) and at the 10th rib.
Trans tubercular / inter tubercular line is the line at the 5th lumbar vertebrae (L5) that pass between tubercle of the iliac crest. Iliac crest is located at the level of the 4th lumbar vertebrae.
The mid clavicular line is a line that passes through the mid inguinal point which is a point between the pubic symphysis and anterior superior iliac spine.
Xiphisternal junction is a xiphoid process that present at the 9th level of the thoracic vertebrae.
Costal margin is a medial margin that consists of true and false ribs. Ribs 7 - 10 present anteriorly while 11 - 12 ribs present posteriorly.
Iliac crest is part of the ileum bone (pelvis bone). It spans from anterior superior iliac spine to posterior iliac spine with the highest level is at the 4th lumbar vertebra (L4). At the 5th lumbar vertebra level is the tubercle of the iliac crest which is 5 cm higher than the anterior superior iliac spine.
From anterior superior iliac spine the inguinal ligament will run from the anterior superior iliac spine to the pubic tubercle. Pubic tubercle is located on the superior surface of the bone of the pubis .Inguinal ligament is attached to the pubic tubercle laterally while medially the lateral sides of superficial inguinal ring attached to the pubic tubercle.
In the superficial inguinal ring, the inguinal hernia will projected to the medial and above the pubic tubercle while femoral hernia will project to the lateral and below the pubic tubercle. Symphysis pubis is a joint which is a midline cartilaginous joint that join the two pubic bones together. Pubic crest is located medial to the pubic tubercle and present as ridges on the pubic bone superior surface.
Linea alba is fibro tendinous raphe that run longitudinally from xiphoid process to symphysis pubis. Linea semilunaris is a line that will pass through the costal margin of the 9th costal cartilage where there is possible to palpate the tip of the gallbladder.
SURFACE MARKING OF THE BLOOD VESSEL
Aortic bifurcation is located to the left of the mid line at the level of the 4th lumbar vertebra while external iliac artery is palpable between the anterior superior iliac spine and the pubic symphysis.
SURFACE MARKING OF ABDOMINAL ORGAN
Along the transpyloric line, the pancreas is palpable which is at the level of the first lumbar vertebra (L1). Tip of gallbladder is palpable at the level of 9th costal cartilage of the costal margin on the right sides where the linea semilunaris intersect.
The base of the appendix is located at 1/3rd of the line joining the anterior superior iliac spine to the umbilicus. ( McBurney point ).
The spleen is palpable in infants. It is located below the ribs 9, 10 and 11 on the left sides of the body.
The kidney is located on the transpyloric line at the level of between T12 - L3. During respiration, kidney moves 2 - 5 cm. Right kidney is lower than left kidney.
The ideal abdominal incision stands on the following principle:
-Allow rapid and easy access to related structures.
-Allow any extension if required.
-Allow proper short term healing (non dehiscence) and proper long term healing (no hernia)
-Allow the patient to be free dorm any pain post operatively.
-Allow a complete satisfaction of the cosmetic appearance.
12 DIFFERENT ABDOMINAL INCISONS
Mid line incision is made through linea alba. The incision is easily and rapidly accessible. Easy to make and to extend as well as to close. However it is painful compared to transverse incision. It produces a poor cosmetic appearance due to the incision is performed across the Langer‘s line. Linea alba is avascular, the incision is bloodless. Below the umbilicus, the linea alba is narrow with blood vessel across it. Beware of the damage to the bladder.
A sub umbilical incision is an incision performed below the umbilicus which is helpful for the incision of the laparoscopic port and for the repair of the para umbilical hernia.
A transverse muscle cutting incision is performed across all muscles with a chance of disrupting the intercostal nerves.
Transverse incision is performed in children and neonates because of lack / no diaphragmatic and pelvic recess like an adult. It is difficult to perform in an adult due to the presence of sub diaphragmatic and pelvic structure. Longer time is required to make the incision and to close the incision. However it heals quickly and no pain as well as lack of problem in the respiratory tract in comparison with longitudinal incision. It is also heals with satisfactory cosmetic appearance. A lot of blood may be loss due to the incision that passes through a few muscles.
Pfannenstiel incision is a transverse incision which is commonly performed to access the female genitalia for c - section, bilateral repair of the hernia, prostate and bladder operations. An incision is made in a downward convex direction through the skin crease of the supra pubic which is 2 cm above the pubis. Later, the rectus sheath is dissected 1cm cephalic to the skin incision after the upper flap has been raised. This is followed latter by longitudinal division of the Midline of the Rectus.
A Thoraco abdominal incision is rarely performed. The incision is performed in the lower thorax and upper abdomen region. Right thoracic abdominal incision is for liver and biliary surgery and left thoracic abdominal incision is for gastric, esophageal and aortic surgery.
Para median incision is performed 1. 5 cm lateral to the midline through the rectus sheath. It is the only / most effective vertical incision to be performed when the catgut appear to be the only available material. It will take a longer time to perform this incision compare to mid line incision. It is also difficult to close using the Jenkin’ s rule as the suture is 4 times longer than the incision. It has a poor cosmetic appearance with a high risk of infection. It may also leads to the denervation of the medial rectus due to the splits of rectus muscle that is > 1cm from the medial sides which later disrupted the intercostal nerves. Besides that the procedure also requires the division of the falciform ligament on the right sides above the umbilicus and the dissection of the tendinous intersection.
Para rectal battle incision is rarely performed nowadays due to the damage of the nerve entering the rectus sheath. It may lead to poor wound healing and the formation of incision hernia post operatively.
Kocher’s incision is performed 3 cm below and parallel to the costal margin from the midline to the lateral border of the rectus. Kocher’s incision is performed at the right sides for cholecystectomy (removal of gallbladder incision) and on the left side for splenectomy or removal of the spleen. Beware of the superior epigastric artery while performing the incision. Kocher’s incision also cannot extend caudally and if the wound /incision extends laterally many intercostal nerves are damaged.
Double Kocher’s incision line (rooftop incision) is performed for any intra- hepatic surgery. The incision is performed for radical gastric and pancreatic surgeries as well as bilateral adrenalectomy. It provides a good access to the spleen and liver.
Gridiron incision / Mc Burney‘s incision is an incision that is classically performed for appendix / appendicitis cases. The incision point is at the right angle of the junction of the outer middle third at the line that joins the anterior superior iliac spine to the umbilicus. These procedures will lead to the cut of external oblique in a direction of the line of the fibre and split transversely for internal oblique and transversus abdominus in the line of the fibre. Precaution should be taken to avoid any damage to the deep circumflex artery, Ilio inguinal and iliohypogastric nerves. It can be modified into the skin crease horizontal incision.
Rutherford - Morrison incision is made by extending the Mc Burney incision laterally and cephalic which divided the external oblique obliquely to provide access to the appendix, cecum and right colon.
Lanz incision is used to divide the iliohypogastric and ilioinguinal nerves which may leads to inguinal canal denervation and formation of inguinal hernia. Lanz incision is located closer to the anterior superior iliac spine and near / lower to the McBurney points. It provides a better cosmetic appearance.
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