Anterior Abdominal Wall and Inguinal Region

Question 1

What are some of the general layers of the abdominal cavity?

Answer 1

Skin and superficial fascia overly three flat layers of muscle followed inferiorly by more fascia called transversalias fascia and intraperitoneal fascia. The abdominal midline also has another muscle layer interiorly called rectus abdominus.

Question 2

What is the peritoneum?

Answer 2

The peritoneum is the lining of the internal cavity of the abdomen

Question 3

What are the attachments of the anterior abdominal muscles?

Answer 3

Abdominal muscles are bridging the thoracic cage above with the pelvic bony structures below the abdomen. They attach to the costal margin above and the superior aspect of the bony pelvis below (anteriorly; the pubic tubercle and posteriorly; the iliac spine). There are three layers of flat muscles to attach to the costal margin which is not easily fit so the superiormost layer attaches to the superior aspect of the ribs and the deepest layer attaches to the inferior surface of the ribs with the middle layer attaching to the edge.

Question 4

Explain the differences in the abdominal muscles medially to laterally?

Answer 4

The muscle fibres are fleshy laterally and aponeurotic medially.

Question 5

What happens to the abdominal muscles in the midline of the body?

Answer 5

The muscles interdigitate (knit together) in the midline and extend posteriorly to the thoraco-lumbar fascia. The vertical line were the aponeurosis from each side meet is called the linear alba.

Question 6

Give some features of the outermost layer of anterior abdominal muscles.

Answer 6

Outer layer: External Oblique (front pocket muscles). It overlaps the thoracic cage and there is a free interior edge and it attaches to the anterior half of the iliac crest (to the ASIS) and then attaches to the pubic tubercle and pubic crest –> there is a part that is not attached to anything; this area is thickened and almost turns under itself –> called the inguinal ligament. Beyond the pubic tubercle, there is a triangular deficiency in the aponeurosis that leads into the spermatic cord.

Question 7

What is the outermost layer of anterior abdominal muscles?

Answer 7

External Oblique

Question 8

What is the second to most superficial later of anterior abdominal muscle?

Answer 8

Internal Oblique

Question 9

Give some features of the second to most superficial later of anterior abdominal muscle

Answer 9

Middle Layer: Internal Oblique (back pocket muscle). It attaches directly to the costal margin above. The lowermost fibres attach to the iliac crest as far as the ASIS, but there is also some fibres taking origin beyond this, taking origin from the lateral 2/3 of the inguinal ligament and then arching (upwards, over and down) to insert into the pubic crest.

Question 10

What is the deepest layer of the anterior andominal muscles?

Answer 10

Transversus Abdominus

Question 11

Give some features of the deepest layer of the anterior andominal muscles

Answer 11

Deepest Layer: Transversus Abdominus (horizontal) The three different directions of the muscle allow for greatest strength. Contraction of theses muscles are important because they protect the viscera but also help in processes such as defication, urination etc. These muscles attach to the interal aspect of the thoracic cage, posteriorly to the thoraco-lumbar fascia, the linear alba anteriorly and attach to te iliac crest as far as ASIS. The lowermost fibres arise from the lateral 1/3 inguinal ligament and then arch to insert into the pubic crest via conjoined tendon (called the conjoined tendon) with the internal oblique muscles. (this means that these fibres do not extent to the linear alba.

Question 12

What is the fourth set of ant. abdomial muscles?

Answer 12

rectus abdominus.

Question 13

Where does rectus abdominus run?

Answer 13

There is another pair of muscles anteriorly along the midline of the abdomen called rectus abdominus.

Question 14

What are the attachments of rectus abdominus?

Answer 14

They attach to the body and crest of the pubus below and gets wider as it extends up to attach to costal cartilages 5, 6 and 7 to become edge to edge with pectoralis major.

Question 15

What is the significance of the tendinous intersections/disruptions (fibrous) to the decent of the muscle fibres on rectus abdominus?

Answer 15

increase the power/strength of the abs.

Question 16

What is the rectal sheath?

Answer 16

The aponuerosis of the three flat muscles form a rectal sheath that encloses rectus abdominus to approach the linea alba. There is also a posterior sheath part of the way down behind rectus abdominus in which some vessels run.

Question 17

Explain the changes in the rectal sheath from superior to inferior?

Answer 17

About an inch below the umbilicus, the aponeurosis do not form the posterior rectus sheath anymore, instead all running anterior to the rectus abdominus muscles

Question 18

What is the arcuate line?

Answer 18

The acuate line is this line of demarkation where the posterior rectus sheath ends and arches.

Question 19

Where is the neurovascular plane in the abdomen?

Answer 19

The Neurovascular plane is between the internal oblique muscles and transversus abdominus muscle laters.

Question 20

Explain the general innervation of the abdomen?

Answer 20

• segmental innervation of the anterior abdominal wall.
• T10 is the umbilicus and L1 is the groin
• T 7, 8, 9 is the anterior wall above the umbilicus and T11 and 12 are between the umbilicus and the groin.

Question 21

Explain generally the blood supply of the abdomen

Answer 21

Blood supply: the main arterial supply comes from the superior epigastric (branch of internal thoracic artery) from above and the inferior epigastric (branch of iliac artery) from below. They run in the rectus sheath.

Question 22

What is the situation in the abdomen for venous drainage?

Answer 22

There is dual venous drainage from the abdomen (portal and systemic) The areas of overlap between these two venous systems become important when a patient has portal hypertension. The abdominal wall is a site of this portosystemic anastomoses.

Question 23

What are some features of the inguinal ligament? Extensions?

Answer 23

The inguinal ligament extends from the ASIS to the pubic tubercle.
There is a cresentic extension of the inguinal ligament toward the pectineal line (marks the pelvic inlet) of the pubic bone –> Lacunar Ligament. There is also a linear extension from the lacunar ligament called the Pectineal ligament.

Question 24

Explain the development of the testis and the requirement for testicular decent?

Answer 24

Testes develop in the layers of extraperitoneal fat quite high up on the posterior abdominal wall and then descend into the scrotum through the inguinal ligament.

Skin and superficial fascia are continuous with the scrotum but the testis need to get through the fascia transversalis layer and muscles to reach the scrotum.

Question 25

Explain the path of the testis through the inguinal canal.

Answer 25

the testes travel from their position posteriorly in the extraperitoneal fat to a more anterior location where then migrate through fascia transversalis. They create a deficiency in fascia transversalis halfway between ASIS and the pubic tubicle a finger’s breadth above the inguinal ligament. This deficiency is called the deep inguinal ring.

Transversus abdominus and internal oblique are such that they arch over the medial aspect of the inguinal ligament. So the testis travel through the inguinal canal. There is an anatomical deficiency in external oblique (called the enternal inguinal ring) naturally so the testis are able to get through this layer easily.

Question 26

What layers help to make up the spermatic cord?

Answer 26

The testis takes the vessels, nerves, lympahtics etc with it to make up the spermatic cord. When they exit the inguinal canal, they have collected internal and premasteric fascia which contains some muscles (responsible for retraction of testis when it is cold, dangerous etc. and external spermatic fascia with each layer it penetrates –> becomes the spermatic cord.

Question 27

What is the inguinal ligament?

Answer 27

Inguinal Ligament: folded inferior border of the external oblique aponeurosis extending between ASIS and pubic tubercle

Question 28

What are the deep and superficial rings of the inguinal canal?

Answer 28

Superficial Ring: medial opening in external oblique aponeurosis
Deep Ring: deficiency (outpouching) in fascia transversalis

Question 29

What are the landmarks of the inguinal canal?

Answer 29

Inguinal Canal: slit-like passage extending downwards and medially above and parallel to medial half of the inguinal ligament.

• -> Floor: inguinal ligament
• -> Roof: Arching fibres of the internal oblique and transversus abdominus
• -> Ant. Wall: external oblique aponeurosis, internal oblique muscle laterally
• -> Post. Wall: transversalis fascia, conjoint tendon medially

Question 30

Explain abdominal and inguinal herniation.

Answer 30

When intrabdominal pressure increases and the contents are trying to escape, it can form an abdominal hernia. One area of weakness where herniation can occur commonly is the inguinal canal. Protrusion of abdominal contents through the abdominal wall is called an abdominal hernia.
Sites of weakness can be congenital or may be due to post operative mechanisms.

An abnormal protrusion of contents through the deep ring and into the inguinal canal is called an inguinal hernia. Indirect herniation occurs when the herniation follows the path of the inguinal canal. Direct herniation is when the inguinal canal is breached by the abdominal contents through an area of weakness in its posterior wall and will not enter the scrotum.