6.1: Abdominal Wall

Question 1

What borders define the abdominal wall?

Answer 1

Extends from the thoracic cage (cartilages of ribs 7-10 + xiphoid process) to the pelvis (inguinal ligament, superior margins of pelvic girdle)

Question 2

Describe the layers of the lateral abdominal wall from superficial - deep

Answer 2

Skin

Superficial fascia:

1. Fatty layer “camper’s fascia”
2. Membranous layer underneath “Scarpa’s fascia”

Muscles:

1. External oblique muscle
2. Internal oblique muscle
3. Transverse abdominis muscle

Transversalis fascia;
Extraperitoneal fascia; thinner fatty layer

Parietal Peritoneum: lines the abdominal cavity
Mesentery; blood vessels, nerves, lymphatics, suspends intraperitoneal organs
Visceral Peritoneum: lines the abdominal organs (has pressure receptors, but not somatic - responsible for referred pain patterns)

Question 3

What covers retroperitoneal organs?

Answer 3

Anteriorly covered by visceral peritoneum and the parietal peritoneum continues around posteriorly BUT they are not suspended by mesentery

Question 4

What direction to the external, internal oblique and transverse abdominis muscle fibres point in?

Answer 4

External: Inferior and medial
Internal: superior - medial and transverse
Transverse abdominis: transverse

Question 5

What fascia comes off the external oblique muscle and covers rectum abdominus anteriorly and medially? What happens in the midline?

Answer 5

Aponeurosis, the fibres become very intertwined and strong at the midline dense CT structure called the ‘linea alba’

Question 6

Where is the linea alba?

Answer 6

Straight down the midline extending from the xyphoid process to the pubic symphysis

Question 7

Where are the internal and superficial inguinal rings and what is their role?

Answer 7

Rings are formed by a deficit in the inferior fibres of…
A) Deep inguinal ring: the transverse abdominus
B) superficial inguinal ring: external oblique wall (mainly its aponeurotic sheath).

They form a passageway for vessels to exit the abdominal cavity to the mons pubis called the inguinal canal.

Question 8

What forms the inguinal ligament and where is it? What forms above it and directly underneath it?

Answer 8

Formed by the inferior fibres of the external oblique muscle and stretches from the ASIS - pubic tubercle. Helps create the floor of the inguinal canal (oblique passage). Underneath the femoral canal forms where femoral vessels may pass (nerve, artery and vein)

Question 9

Where is the conjoint tendon and what is its role? Which muscles contribute to it?

Answer 9

The Conjoint tendon is a dense aponeurosis that helps strengthen the abdominal wall. It is created from the medially united tendinous fibres of the internal oblique muscle (mainly) and transverse abdominis. It is attached to the pubic crest and behind to the pectin.

Question 10

Where and what is the transversalis fascia?

Answer 10

Deep fascia that lines the abdominal cavity and continues to the pelvic cavity, lines the deep surface of transversus abdominis

Question 11

Where is the arcuate line and what is its significance?

Answer 11

T10, around the belly button level. It dictates where the posterior layer of the rectum sheath stops (the most inferior portion of rectum abdominis dives deeper into the abdominal cavity and has a lot fewer layers posterior to the arcuate line). Above the line there is more aponeurosis (both in front and behind rectus abdominis, and meeting in the middle at linea alba)

It’s also where the inferior epigastric vessels come off the external iliac artery behind rectum abdominis and pierce into the muscle

Question 12

Describe rectum abdominis muscle

Answer 12

Two vertical enclosed muscles, segmental with lateral tendinous insertions (6 pack look)

Question 13

What comprises the rectum sheath? Where is it most dense?

Answer 13

External oblique, internal oblique (anterior and posterior), transversus abdominis (anterior and posterior), Rectus abdominis in the centre and surrounding aponeurosis.

It is most dense anterior to the rectus abdominis muscle

Question 14

How does one get a rectus sheath hematoma and what is a sign of one?

Answer 14

Since the space of rectus abdominis is so tightly bound by fascia, if there is bleeding in the rectus sheath or within the actual muscle the hematoma has nowhere to expand (very painful). Eventually a bruise will appear not the abdomen

Question 15

As the testis descend from their retroperitoneal position through the abdominal wall musculature and into the scrotum…
A) What is the layer of external oblique that surrounds the testis

B) What is the layer within the spermatic cord that the internal oblique becomes?

C) Is there a layer of transversus abdominis that eventually surrounds the testis?

D) What is the most inferior layer that surrounds the testis?

Answer 15

A) External oblique layer becomes the external spermatic fascia

B) Internal oblique layer becomes the cremasteric fascia

C) As the testis descend they don’t punch through transversus abdominis but passes underneath it’s muscle fibres

D) Instead of transversus abdominis, the spermatic chord’s most internal layer is derived from the transversalis fascia, the internal spermatic fascia

Question 16

Where is the inguinal canal and what is within in it in males and females?

Answer 16

Begins at deep inguinal ring and continues 4cm medial and downward to the superficial inguinal ring:

Male: spermatic cord, ilioinguinal nerve

Female: ilioinguinal nerve, the round ligament of the uterus (exits the inguinal canal and dissipates at the labia majora)

Question 17

Where do the lowest fibres of transversus abdominis and the internal oblique muscle arise from?

Answer 17

Thickening of the underlying iliopsoas fascia

Question 18

What ligaments help support the superficial ring and what are the fibres above and below the ring called?

Answer 18

Superficial ring is partly reinforced by the lacunar ligament (branching medially off the inguinal ligament)

The fibres above and below are called the inferior/superior crus

Question 19

What causes a hernia? Name five different types an individual can have in the abdominal wall

Answer 19

Hernias are caused by deficits (weakenings, potentially due to trauma to abdominal wall nerves or openings)

1. Inguinal hernia; protrusion of intestine through weak spot in inguinal canal or inguinal triangle
2. Umbilical hernia; through umbilical ring which is a gap in the linea alba, occurs in babies
3. Femoral hernias; through femoral canal
4. Epigastric hernias: in epigastric region through linea alba
5. Incisional hernias: protrusion of abdominal viscera through surgical incision if it doesn’t heal correctly

Question 20

What are the borders of Hasselback’s triangle and what is its other name?

Answer 20

Hasselback’s triangle/inguinal triangle

Medially: lateral edge of rectus abdominis/Linea semi lunaris
Inferior: inguinal ligament/inferior aponeurosis of external oblique
Lateral: inferior epigastric vessels (vein and artery)

Question 21

What are the differences between an indirect and a direct inguinal hernia?

Answer 21

Indirect: intestines worm their way through the deep inguinal ring, (inguinal canal and out into the scrotum or labia majora). This happens lateral to the inferior epigastric vessel (lateral border of Hasselback’s triangle), and therefore this hernia is lateral to a direct inguinal hernia, is often a congenital weakness

Direct: through the Hasselback’s triangle/abdominal wall and layers of tissue (often disappears when laying down). Usually due to acquired muscle weakness

Question 22

What does the processes vaginalis surrounding the testicle become?

Answer 22

The Tunica vaginalis

Question 23

What innervates the skin, muscle and parietal peritoneum of the anterolateral abdominal wall?

Answer 23

Mainly T7-T12 and L1 spinal nerves that give off lateral cutaneous branches on the way

• mainly intercostal (T7-T11)
• subcostal T12

L1:

• iliohypogastric; terminates on mons pubis/upper groin
• ilioinguinal: sensation to external genitalia

Question 24

Which arteries supply the anterolateral abdominal wall?

Answer 24

1. Intercostal arteries
2. Lumbar arteries
3. Epigastric’s: anastomose behind rectus abdominis
   Superior epigastric - superior part of rectus abdominis, branches off internal thoracic artery
   Inferior epigastric - inferior parts of rectus abdominis, branches off external iliac

Question 25

What is the significance of the “watershed” line?

Answer 25

Where the arcuate line is, above this all superficial lymph drainage goes the axillary lymph nodes and below goes to the superficial lymph nodes

Question 26

Which lymph nodes are involved in the deep lymphatic drainage of the abdomen

Answer 26

1. Parasternal nodes
2. Pre-aortic; celiac, superior and inferior mesentery
3. Externally iliac nodes along the external iliac artery

Question 27

What are the criteria in choosing which abdominal incision to make?

Answer 27

Closest to the area and can provide long-lasting strength to minimize chances of a hernia. Consider stomas, previous abdominal operations, patient status and speed operation must be preformed.

There is better healing if incisions are made parallel to the skin’s natural tension lines called Langer lines

Question 28

What are some advantages to making a midline or paramedical incision?

Answer 28

Mostly aponeurosis/linea alba so is should be bloodless, low risk of nerve or muscle fibre damage. It also provides good access to the upper abdomen

Question 29

What are some advantages to making a transverse abdominal incision and what are the two types?

Answer 29

1. Kocher incision (higher up): Better for obese patients, exposes gall bladder and biliar tract (cholecystectomy)
2. A Pfannenstiel incision (lower down): often used in C sections

Question 30

What is a gridiron approach in abdominal incisions and when is this approach often chosen?

Answer 30

A decision to ‘split’ muscle (spread them apart to access the abdomen), often chosen in appendectomies