10.1 - Anatomy: Abdominal Wall & Inguinal Region

Question 1

What are the boundaries of the abdomen?

• Superiorly? (3)
• Inferiorly? (4)
• Anterolaterally? (5)
• Posteriorly? (3)

Answer 1

Question 2

What are the layers of the anterior abdominal wall? (superficial to deep)

Answer 2

1. Skin
2. Subcut
3. External oblique muscle
4. Internal oblique muscle
5. Transverse abdominus muscle
6. Transversalis fascia
7. Extraperitoneal fat
8. Parietal peritoneum

Question 3

What is the Rectus Sheath?

Answer 3

The rectus sheath is a tendon sheath (aponeurosis) which encloses the rectus abdominis and pyramidalis muscles. It is an extension of the tendons of the external abdominal oblique, internal abdominal oblique, and transversus abdominis muscles. In addition to these muscles, the rectus sheath also contains neurovasculature of the anterior abdominal wall. Its function is to protect the contents it encloses.

Question 4

What is the difference between the rectus sheath above and below the arcuate line?

Answer 4

The arcuate line of rectus sheath, the linea semicircularis, the arcuate line, or the semicircular line of Douglas, is a horizontal line that demarcates the lower limit of the posterior layer of the rectus sheath. It is commonly known simply as the arcuate line. It is also where the inferior epigastric vessels perforate the rectus abdominis.

Question 5

What forms the anterior and posterior rectus sheaths respectively?

Answer 5

Question 6

What is the arterial supply, venous drainage and innervation of the diaphragm?

• Superior Surface
• Inferior Surface

Answer 6

Question 7

How does the diaphragm develop?

Answer 7

Question 8

What are the clinical consequences of a rupture of the diaphragm?

• What is a hiatal hernia?
• On which side of the body do most hiatal hernias occur? why?
• What is a Congenital diaphragm hernia? What 2 structures fail to fuse that causes this?

Answer 8

Question 9

What is the inguinal canal?

• Length?
• What does it run to and from?

Answer 9

The inguinal canal is a short passage (4cm long) that extends inferiorly and medially through the inferior part of the abdominal wall. It is superior and parallel to the inguinal ligament.

The canal serves as a pathway by which structures can pass from the abdominal wall to the external genitalia. It is of clinical importance as a potential weakness in the abdominal wall, and thus a common site of herniation.

Question 10

Where does the inguinal canal run to and from?

• What is the deep inguinal ring a hole in?
• Where is the deep IR located?
• Superficial IR is a defect in which muscle?
• What is the relationship between superficial IR and the pubic tubercle?

Answer 10

Runs from deep inguinal ring to superficial inguinal ring.

• Deep inguinal ring = hole in transversalis fascia
  
  • Midway between ASIS & pubis symphisis
  • ½ inch above inguinal ligament
  • Lateral to inferior epigastric vessels
• Superficial inguinal ring = V-shaped defect in the lower and medial fibres of external oblique
  
  • Immediately above and medial to pubic tubercle.

Question 11

What are the boundaries of the inguinal canal? (MALT)

• Anterior wall
• Floor
• Roof
• Posterior wall

Answer 11

• Anterior wall = external oblique aponeurosis
• Floor = enrolled edge of inguinal ligament, Lacunar ligament medially.
• Roof = lower edges of internal oblique and transversus abdominus muscles.
• Posterior wall = transversalis fascia (lateral half) and conjoint tendon (medial half) (made of fusion of internal oblique and transversus abdominus aponeuroses).

MALT = muscles (superior), aponeurosis (anterior), ligament (floor), transversalis (posterior)

Question 12

What are the contents of the inguinal canal in men and women?

• Men - SC: 3x4
• 3 contents for women
• What is found in both?

Answer 12

Male - spermatic cord with:

• 3 coverings = external spermatic fascia, cremaster muscle, internal spermatic fascia
• 3 nerves = ilioinguinal nerve, genital branch of genitofemoral nerve, sympathetic fibres
• 3 arteries = testicular artery, artery of vas deferens, cremasteric artery
• 3 other structures = vas deferens, pampiniform venous plexus, lymphatics)

Female:

1. Round ligament of the uterus
2. Ilioinguinal nerve
3. Genital branch of the genitofemoral nerve

Remnant of processes vaginalis found in both male and female.

Question 13

What are the layers of the inguinal canal?

Answer 13

Question 14

How does the inguinal canal develop embryologically?

• What is the gubernaculum? What does it guide?
• What is the inguinal canal a pathway for in men?
• Pocketing of what forms the IC? What is this called?
• What can a failure of the degeneration of processes vaginalis cause?
• What does the gubernaculum link in women?
• Which 2 structures does the gubernaculum become in adult women?

Answer 14

• During development the tissue that will become the gonads (testes/ovaries) establish in the posterior abdominal wall, and descend through the abdominal cavvity.
• A fibrous cord of tissue called the gubernaculum attaches the inferior portion of the gonad to the future scrotum or labia and guides them during their descent.
• The inguinal canal is the pathway by which the testes (in an individual with an XY karyotype) leave the abdominal cavity and enter the scrotum.
• In the embryological stage, the canal is flanked by an out-pocketing of the peritoneum (processus vaginalis) and the abdominal musculature.
• The processus vaginalis normally degenerates, but a failure to do so can cause an indirect inguinal hernia, a hydrocele, or interfere with the descent of the testes.
• The gubernaculum (once it has shortened in the process of the descent of the testes) becomes a small scrotal ligament, tethering the testes to the scrotum and limiting their movement.
• Individuals with an XX karyotype also have a gubernaculum, which attaches the ovaries to the uterus and future labia majora. Because the ovaries are attached to the uterus by the gubernaculum, they are prevented from descending as far as the testes, instead moving into the pelvic cavity.
• The gubernaculum then becomes two structures in the adult: the ovarian ligament and round ligament of uterus.

Question 15

What is the difference between the mid-inguinal point and the mid-point of the inguinal ligament?

• Where can the femoral pulse be felt? Which 2 structures is this halfway between?
• What are the 2 attachment points of the inguinal ligament?

Answer 15

Question 16

• What are most abdominal hernias caused by?
• Which sex experiences more inguinal hernias?
• What is an inguinal hernia?
• What are the 2 types of inguinal hernias? Which is more common?
• What are indirect hernias cause by?
• What is Hesselbach’s triangle? Boundaries?
• What is an indirect inguinal hernia?
• What is the difference between an inguinal and a femoral hernia?

Answer 16

• Inguinal hernias account for approx. 75% of abdominal hernias.
• Occur in both sexes but more in men due to passage of the spermatic cord through the inguinal canal.
• Inguinal hernia = protrusion of parietal peritoneum and viscera, such as the small intestine, through a normal or abnormal opening from the cavity in which they belong.
• 2 types of inguinal hernias:
• Direct inguinal hernia = Passes through abdominal wall to superficial inguinal ring. Does not extend to scrotum = sac formed in peritoneum.
  
  • Occurs due to weakness in anteior abdominal wall in inguinal triangle (Hesselbach’s trraingle) - bouned by the inferior epigastric vessels, inguinal ligament and the lateral border of the rectus abdominus.
• Indirect inguinal herna = most common (males>females).
  
  • Travel from deep inguinal ring - canal - superficial inguinal ring - scrotum (lies within covering of spermatic cord).
• Femoral hernia will occur beneath the pubic tubercle, inguinal = above tubic tubercle

Question 17

• What is a femoral hernia? How do they present?
• Why do femoral hernias occur more frequently in women compared to men?
• Complication?

Answer 17