Anterior Abdominal Wall and Inguinal Region

Question 1

What are the 3 muscle layers of the abdominal wall?

Answer 1

• external oblique
• internal oblique
• transversus abdominis

Question 2

What direction does the external oblique travel in and attach to?

Answer 2

• Fibres run in an anterior-infection direction
• attaches to iliac crest, to ASIS and pubic tubercle so inbetween ASIS and pubic tubercle external oblique is not attached to anything = inguinal ligament
• finish at mid-clavicular line where it becomes an aponeurosis

Question 3

What direction does the internal oblique travel in?

Answer 3

middle layer, fibres run in anterior-superior direction

- finish at mid-clavicular line where it becomes an aponeurosis

Question 4

In what direction does the transversus abdominis travel in?

Answer 4

Deep layer, fibres run in a transverse direction

- finish at mid-clavicular line where it becomes an aponeurosis

Question 5

What are some features of the rectus abdominis?

Answer 5

• runs from xiphoid process superiorly to pubic symphysis inferiorly
• has tendinous intersections along muscle length
• enclosed by aponeurotic sheath derived from aponeuroses of external oblique, internal oblique and transversus abdominis
• linea alba down the middle
• strengthens middle part of abdominal wall where it becomes aponeurotric

Question 6

What blood supply is there to the rectus sheath?

Answer 6

inferior epigastric from external iliac from inguinal ligament coming up
superior epigastric from internal thoracic

Question 7

What nerves supply the abdominal wall muscles?

Answer 7

T7 - xiphoid
T10 - umbilicus
T12 - subcostal
L1 - iliohypogastric and ilioinguinal branches
(all are motor to these muscles and sensory to the skin of that area)
Genitofemoral nerve which arises from L1/L2 and has a genital branch and a femoral branch (sensory to thigh only)

Question 8

What are the roots of the subcostal, iliohypogastric and ilioinguinal nerves?

Answer 8

Subcostal nerve root is T12

Iliohypogastric and ilioinguinal nerve root is L1

Question 9

How is the inguinal ligament formed?

Answer 9

the inferior border of external oblique’s aponeurosis rolls under itself

Question 10

What does the spermatic cord contain?

Answer 10

• structures running to and from the testes suspending the testes within the scrotum
• testicular artery, ductus deferens, pampiniform venous plexus, genital branch of genitofemoral nerve, ilioinguinal nerve

Question 11

What surrounds the spermatic cord?

Answer 11

Layers of the abdominal wall - external spermatic fascia, cremaster muscle, internal spermatic fascia

Question 12

In which layers does the genitofemoral nerve lie?

Answer 12

Between the internal spermatic fascia and the cremaster muscle

Question 13

Where does the ilioinguinal nerve lie?

Answer 13

Outside the external spermatic fascia

Question 14

Where is the superficial inguinal ring?

Answer 14

point at which the spermatic cord emerges from the abdominal wall

Question 15

Where is the deep inguinal ring?

Answer 15

point at which the contents of the spermatic cord enter the abdominal wall

Question 16

How do the testes develop?

Answer 16

• on the posterior abdominal wall and descend through the inguinal canal to reach the scrotum around the 9th month of development

Question 17

What is an inguinal hernia?

Answer 17

Protrusion of peritoneum and viscera such as small intestine through an opening or weakness
Count for 75% of abdominal hernias
By themselves are usually harmless but nearly all have potential risk of becoming strangulated (having blood supply cut off)

Question 18

What is direct inguinal canal?

Answer 18

acquired
commonly in males over 40 years old
hernia passes directly through abdominal wall (Hasselbach's triangle)
rarely enters scrotum
medial to inferior epigastric vessels

Question 19

What is indirect inguinal canal?

Answer 19

• congenital (patent process vaginalis)
• more common (2/3 of cases)
• transverses canal within the processus vaginalis (patent processus vaginalis as doesn’t fibrose and deteriorate)
• commonly enters scrotum
• lateral to inferior epigastric vessels

Question 20

What are the borders of Hasselbach’s triangle?

Answer 20

inferior epigastric vessels
lateral border of rectus abdominis
inguinal ligament

Question 21

What other hernias are there?

Answer 21

• incisional: following surgery to abdomen scar creates weakness in abdominal wall
• umbilical: usually in babies, rectus abdominis is not fully joined in the midline
• femoral: herniation into femoral canal, most common in females

Question 22

Where is the femoral canal?

Answer 22

beneath the inguinal ligament so below and lateral to pubic tubercle

Question 23

What is the significance of the arcuate line?

Answer 23

Above the arcuate line: internal oblique splits so one layer goes behind the rectus abdominis (with transversus abdominis and transversalis fascia) and one goes in front (with external oblique)
Under the arcuate line: all aponeuroses pass anterior to the rectus abdominis and posteriorly is only transversalis fascia

Question 24

Where do the femoral artery, vein and nerve pass?

Answer 24

Through a gap between the pelvis and inguinal ligament

Question 25

What passes through the inguinal canal?

Answer 25

Males - spermatic cord

Females - round ligament of the uterus

Question 26

Why is the inguinal canal more of a weak region for men rather than women?

Answer 26

Round ligament of uterus passing through is a much smaller structure than the spermatic cord and so there is much less pressure

Question 27

What is the pampniform venous plexus?

Answer 27

Collection of the testicular veins

Question 28

What are the spermatic cord surrounding layers derived from?

Answer 28

layers of the abdominal wall

Question 29

What does each abdominal wall layer give off to the spermatic cord?

Answer 29

External oblique - aponeurosis part
Internal oblique - muscle fibres
Transversus abdominis - nothing as it is absent when spermatic cord goes through

Question 30

What is the mechanism of the testes descending?

Answer 30

• first start in the abdomen between the peritoneum and the tranversalis fascia
• descends towards the inguinal canal dragging its blood supply with it as well as the peritoneum (as it is stuck to it - retroperitoneal)
• descends through first layer (transversalis fascia covering testes and structures so it becomes the internal spermatic fascia)
• passes underneath transversus abdominis but does not get any layer from this as absent
• goes through internal oblique getting muscle layer which becomes the cremaster muscle
• goes through external oblique giving it a layer of fascia so it becomes the external spermatic fascia
• testes have now picked up 3 layers and pulled the peritoneum along with it forming the processus vaginalis which fuses together and the end bit degrades so there is no connection

Question 31

What is the function of the cremaster muscles?

Answer 31

Helps to regulate the temperature of the testes
When the temperature rises the testes descend and vice versa allowing control of temperature
Innervated by the genital branch of the genitofemoral nerve

Question 32

What is the distinguishing factor between direct and indirect hernias?

Answer 32

Relation of hernia to inferior epigastric vessels
Direct hernias - medial to inferior epigastric vessels
Indirect hernias - lateral to inferior epigastric vessels