Anatomy of the anterior abdominal wall Flashcards
What are the different layers of the anterior abdominal wall?
1) Skin
2) Superficial fascia
3) Muscle (laterally there is 3, however medially there is one “rectus abdominus”)
4) Transversalis fascia
5) Extraperitoneal connective tissue
6) Peritoneum
- If we cut open the peritoneum we will be in the greater sac
What are the two components/layers found in the superficial fascia?
1) Superficial fatty layer (camper’s fascia)
2) Deep membranous layer (Scarpa’s fascia)
What is langer’s lines/cleavage lines?
- They are abdominal skin lines that runs parallel with the neurovascular structures, and split the muscles in the direction of their fibers
- These lines are important for surgeons as incisions are made by them
What is the water shed line?
It is the same as the transumbilical plane, where the venous blood and lymphatic fluid drains upwards above the plane or below the plane of the umbilicus
- Lymphatic drainage above the water-shed line is the axillary lymph nodes, while the superficial inguinal lymph nodes drains below the water-shed line
What happens to the superficial fascia at the anterior superior iliac spine?
- The superficial fascia splits into two (fatty layer, and a membranous layer)
1) Superficial fatty layer (campers fascia)
- The superficial fatty layer (camper’s fascia) below the superior iliac spine is the site of liposuction and it is continuous with the superficial fascia of the thorax and thighs
- In obesity excess fat accumulates here
- Continuous into the scrotum as dartos fascia (responsible for the wrinkling of the scrotum)
2) Deep membranous layer (Scarpa’s fascia)
- Below the superior iliac spine the deep membranous layer will pass over the inguinal ligament blending with the fascia of the thigh (fascia lata) forming holden’s line
- It is continuous with the fascia of the perineum (Colles fascia)
What is holden’s line?
It is the line formed by the joining of the deep membranous layer with the deep fascia of the thigh
If a urethra is ruptured and the fluid accumulates deep to the fascia can it escape to the thigh?
NO
To which fascias is the deep membranous layer (Scarpa’s fascia) connected?
1) Fascia lata of the thigh
2) Colles fascia of the perineum
What are the muscles of the anterior abdominal wall?
1) External oblique
2) Internal oblique
3) Transversus abdominis
- The first three muscles become aponeurotic between the midclavicular line and the midline, and the aponeurosis interweave to form the sheath around the rectus abdominis muscle
4) Rectus abdominis
5) Pyramidalis
6) Cremaster
what is meant by the rectus sheath?
It contains the rectus abdominis and the pyramidalis if present, formed by the anterior and posterior covering of the transversus muscle and the forward covering of the external oblique and backward covering by the internal oblique
What is the origin of the external oblique muscles?
The outer and lower border of the lower 8 ribs (5-12)
What is the insertion of the external oblique muscles?
1) Anterior half of the outer lip of the iliac crest, It gets attached to the ASIS till the pubic tubercle forming the inguinal ligament
2) The posterior margin is free, compared to the other two flat abdominal muscles which are attached to the thoracolumbar fascia
3) Anteriorly the aponeurosis decussates at linea alba and becomes continuous with the aponeurosis of the contralateral external oblique
What is the linea alba?
- A groove in the midline
- It is made of a strong fibrous raphe (collagen fiber)
- Decussating and interweaving of the aponeuroses of the 3 flat abdominal muscles
- It extends from the xiphoid process till the pubic symphysis
- It contains the umbilical ring (which has a low blood supply)
Why is a median incision through the linea alba a common surgical approach?
1) It consists of connective tissue only
2) It does not contain important nerves or blood vessels
- However due to the low blood supply healing will take more time
What is the inguinal ligament (Poupart’s ligament)?
- It is the thickened lower border of the external oblique aponeurosis
- It extends between the pubic tubercle and the anterior superior iliac spine
- Its lateral part is oblique while its medial part is horizontal
- It serves as a retinaculum for the femoral nerve, artery and vein
What is the lacunar ligament?
It is an extension of the inguinal ligament, on its deep medial aspect, it is slightly convex as the fascia lata of the thigh is attached to it pulling it downwards
What is the superficial inguinal ring?
- It is a small opening in the external oblique aponeurosis, antero-medially, this will allow some structures to pass by but the fibers of the external oblique muscle will attach to it
- Basically a triangular deficiency in the external oblique aponeurosis
- It serves as an opening for the passage of testes in males and round ligaments in females
What forms the superficial inguinal ring?
1) Apex: Points laterally
2) Base: Pubic crest
3) Borders: Lateral and medial crura of the aponeurosis of the external oblique muscles
What are all of the ligaments that are formed by the external oblique muscle?
1) Inguinal ligament
2) Lacunar ligament (some fibers of the inguinal ligaments that are attached to the pectinal line)
3) Pectineal ligament (continuation of the inguinal/lacunar ligament along the pectineal line)
4) Reflection of the inguinal ligament (fibers in the floor/between the lateral and medial crus of the superficial inguinal ring, these fibers passes upwards and medially from the lateral crus to under cover of the medial crus)
What is the origin of the internal oblique muscle?
1) Thoracolumbar fascia
2) The intermediate lip of the iliac crest
3) Lateral 2/3rd of the inguinal ligament
What are the site of internal oblique muscle insertion?
- The fibers runs upwards and medially
1) Inserted to the lower 3/4 ribs, costal cartilage and the remaining end into the aponeurosis
What is the origin of the transversus abdominis muscle?
1) Lower 6 ribs and costal cartilage (7-12)
2) Thoracolumbar fascia
3) Inner lip of iliac crest
4) Lateral 1/3rd of the inguinal ligament
What is the insertion of the transverse muscle?
- The inguinal fibers will form the roof of the inguinal canal then it becomes aponeurotic and inserts into
1) Pubic crest
2) Medial part of pectin pubis/pectineal line
- The remaining part is aponeurotic
Iliac crest is the origin of which abdominal muscles?
1) Outer lip gives attachment to external oblique
2) Intermediate lip gives attachment to internal oblique
3) Inner lip gives attachment to Transversus abdominis
What is the function of the external oblique muscles?
It helps in the forward flexion
What are the blood vessels that anastomoses in the rectus sheath?
1) Superior epigastric (a branch of the internal thoracic artery)
2) Inferior epigastric
What is the conjoint tendon formed of?
It is formed by the joining of the aponeurosis of the inferior arching fibers of the internal oblique and transverse abdominis, arising from the inguinal ligament
- It gets attached to the pubic crest and the pectineal line
What is the inguinal canal?
- It is a inter-muscular canal between the deep to the superficial ring (passage between the deep and superficial inguinal openings)
- It is about 4cm in length
- It is superomedial to the inguinal ligament
What forms the posterior wall of the superficial inguinal ring?
The reflected part of the inguinal ligament
Why does the inguinal canal oblique?
- In order for it to act like a valve when there is an intra-abdominal pressure
- Otherwise if it wasn’t oblique and we had a intra-abdominal pressure then whatever inside will pop off
Where is the inguinal canal located?
We have to look at the mid-point of the inguinal ligament, where we will also see a femoral nerve
Does the transverse abdominal muscle pass in front of the deep inguinal ring?
No
What is the interfoveolar ligament?
It is a thickening of the fascia transversalis (it is found at the medial side of the internal ring and anterior to the inferior epigastric vessels)
- it’s nothing but a part of the transversalis fascia. It’s also partially attached to the transverse abdominis muscle; when it contracts it goes more horizontal so it pulls the opening more laterally
- The transverse abdominis muscle is attached to the superior crus of the deep inguinal ring, in order for it to pull the ring laterally and increase the obliquity of the exit
- When u reduce the hernia they play around those ligaments to tighten it up.
What is the shape of the rectus abdominis muscle?
- It is a vertically running muscle, wider above than below, formed of two heads a medial one and a lateral one
- It is covered by a rectus sheath
What is the origin of the rectus abdominis muscle?
1) Medial head: The anterior surface of the pubic symphysis
2) Lateral head: The lateral part of the pubic crest and the pubic tubercles
Where does the rectus abdominis muscle insert?
Medial-xiphoid process, and 5th-7th costal cartilages
How is the rectus sheath fomed?
- We have external first going around the rectus then
- The internal splits into two and surrounds the rectus muscle
- The transverse goes behind it
- So external in front and transverse in the back and internal in between it from both sides
What is the arcuate line?
- It is the lower free edge of the posterior wall of the rectus sheath
- It is located between the umbilicus and pubic symphysis
- Arcuate line is where all the 3 layers the external interior and transverse they are in front of the rectus abdominis. No splitting all is escaping in front
What forms the rectus sheath above the costal margin?
1) Anterior wall: The aponeurosis of the external oblique only
2) Posterior wall: Deficient so that the rectus muscle rests on the 5th-7th costal cartilage
What forms the rectus sheath between the costal margin and the arcuate line?
1) Anterior wall: The aponeurosis of the external oblique muscle and the anterior lamina of the internal oblique aponeurosis
2) Posterior wall: Internal oblique aponeurosis and the transversus abdominis aponeurosis
What forms the rectus sheath below the arcuate line?
1) Anterior wall: The aponeurosis of all the three muscles
2) Posterior wall: the transversalis fascia and peritoneum
What makes the rectus abdominis muscle unique?
1) It present 3 tendinous intersections
- At the tip of the xiphoid process
- At the umbilicus
- Midway between them
Why do we make a vertical incision in the tendinous intersections?
To avoid damaging the epigastric vessels
Why do we pull the rectus muscle laterally?
Because if we pull it medially we might as well pull the inferior epigastric artery and it might snap
What are the contents of the rectus sheath?
1) Rectus abdominis muscle and the pyramidalis
2) Superior and inferior epigastric vessels
3) 7TH-1TH Intercostal and subcostal nerves
4) Lymphatic vessels
What happens to the intra-abdominal pressure when we perform crunches?
The pressure increases
What is the pyramidalis?
- Found in the rectus sheath
- It is a small triangular muscle
- It lies anteriorly to the inferior part of the rectus abdominis
- It extends from the pubis to the linea alba
What is the function of the pyramidalis muscle?
It tenses the linea alba
What are the actions of the muscles of the anterior abdominal wall?
1) Increases the intra-abdominal pressure
- The internal and external oblique muscles:
- Flexion of the trunk (done by the muscles of both sides)
- Lateral flexion of the trunk (muscle of one side)
- The oblique muscle rotates the trunk
Where is the neurovascular plane found?
- It lies between the middle and deepest layers of muscles (where the neurovascular structure lays)
- It corresponds to the neurovascular plane in the intercostal spaces
What are the nerves of the anterolateral abdominal wall?
1) Supplied by the ventral rami of the lower six thoracic nerves in addition to the L1
2) Subcostal nerve (T12 innervates the skin above the inguinal ligament, the inferior part of the external oblique, internal and transversus, it also innervates the rectus abdominis and pyramidalis)
3) Iliohypogastric nerve L1 (It supplies the obliques, transversus abdominis muscle, skin over the inguinal and hypogastric regions
4) Ilioinguinal nerve L1 (Supplies the obliques, transversus abdominus muscle and the skin of the scrotum/labia majora, and finally the upper medial thigh
What nerve supplies the skin near the umbilicus?
The 10th thoracic nerve, and it is the place of an appendix referred pain
What nerves innervates the inferior part of the external, internal obliques and the transversus?
Subcostal nerve
What nerve innervates the rectus abdominis?
The subcostal nerve
What nerve innervates the pyramidalis muscle?
The subcostal nerve
What nerve innervates the Obliques, and the transversus abdominis muscle?
Both the iliohypogastric and the ilioinguinal nerves (L1)
Which nerve supplies the skin over the inguinal and hypogastric regions?
The iliohypogastric nerve (L1)
Which nerve supplies the skin of the scrotum/labia majora, and the upper medial thigh?
Ilioinguinal nerve (L1)
Where is the pain of the appendix gets referred to?
To the skin near the umbilicus which is supplied by the 10th thoracic nerve
What are the arteries of the anterolateral abdominal wall?
1) Superior epigastric artery
- It enters the rectus sheath superiorly, and anastomoses behind the rectus abdominis with the inferior epigastric artery
2) Inferior epigastric artery
- It enters the rectus sheath below the arcuate line, and runs posterior to the rectus abdominis and it anastomoses with the superior epigastric artery
3) Intercostal artery 10 and 11
4) Lumbar arteries
5) Femoral artery (from the lower limb)
The superior epigastric artery is a continuation of which artery?
The internal thoracic artery
The inferior epigastric artery is a branch of which artery?
External iliac artery
What are the superficial veins of the anterior abdominal wall?
- Superficial Veins
1) Drains the lateral thoracic and internal thoracic veins
2) Inferiorly: Drains to the superficial epigastric veins
3) Paraumbilical vein: Drains into the portal vein through the round ligament of the liver
4) Thoracoepigastric vein: it may exist as a result of altered venous flow, between the superficial epigastric vein (a tributary of the femoral vein) and the lateral thoracic vein (an axillary vein tributary)
What are the deep veins of the anterior abdominal wall?
- It corresponds to the arteries mainly, and there is an anastomoses between the inferior epigastric vein (a tributary of the external iliac vein) and the superior epigastric (a tributary of the subclavian vein)
What is the clinical importance of the anastomoses between the superficial and deep veins of the anterior abdominal wall?
They provide collateral circulation (called the thoracoepigastric vein) during the blockage of either vena cava
In which vein does the superficial vein of the anterior abdominal wall drain?
1) Lateral thoracic
2) Internal thoracic
In to which vein does the anterior abdominal wall drain inferiorly?
Superficial epigastric vein
Where does the paraumbilical veins (one of the superficial veins of the anterior abdominal wall) drain to?
Portal vein, through the round ligament of the liver
What are the lymphatic of the abdominal wall?
1) Superficial lymphatics which accompanies the superficial veins
2) Deep lymphatics which accompanies the deep veins
Where are the superficial lymphatics found?
1) Superior to the umbilicus
2) Below the umbilicus
Where does the superficial lymphatics that are superior to the lymphatics drains into?
1) Axillary lymph nodes
2) Superficial inguinal lymph nodes
Where does the deep lymphatics drain into?
1) External iliac
2) Common iliac
3) Lumbar lymph nodes
What are the features of the internal surface of the abdominal wall
1) Median umbilical fold
2) Medial umbilical fold
3) Lateral umbilical fold
4) Round ligament of the liver
What is the median umbilical fold?
- Remnant of the urachus
- Extends from the apex of the urinary bladder
- It covers the median umbilical ligament
What is the medial umbilical fold?
It covers the medial umbilical ligaments (made of the obliterated umbilical arteries)
What does the lateral umbilical fold cover?
The inferior epigastric vessels
What is the round ligament of the liver?
- It is the fibrous remnant of the umbilical vein which extends from the umbilicus to the liver
- Located in the lower free border of the falciform ligament
What are the different ports for abdominal incision?
1) Epigastric port
2) Midclavicular port
3) Anterior axillary port
4) Umbilical port
- These are tiny perforations of the abdominal wall which allows the entry of the remotely operating instruments, with such procedure the risks for nerve injury and hernia are minimized
What is the gridiron (muscle-splitting) incision?
- It is used in appendectomy (and the incisions are done obliquely)
- It is done at the McBurney point (which is 2.5cm supero-medial to the anterior superioriliac spine on the spinoumbilical line)
- The muscle fibers are separated and not cut into
- Iliohypogastric nerve must be preserved (as if it gets damage then the possibility of hernia increases)
What is a incisional hernia?
It is the protrusion of the omentum or and organ through a surgical incisions
What are the causes of incisional hernia?
1) Improper incision
2) Infection
3) Old age
4) Obesity
5) Debility
