Overview of the Digestive tract and Peritoneal Coverings

Question 1

Identify the important landmarks defining the bounderies of the abdominal cavity

Answer 1

Sup- diaphragm

Inf- pelvic brim

anterolateral- internal oblique, external oblique, transversus abdominus

ant- rectus abdominus

posterolateral- lower ribs, psoas major, quadratus lamborum, transversus abdominus

Question 2

What is the transpyloric plane?

Answer 2

Lies halfway between the suprasternal notch and top of pubis

lower part of body of L1

Approximately one hand’s breadth below the xiphisternal point

Structures passing through the transpyloric plane:

9th costal cartilage

pyloris

neck of pancreas

origin of Superior mesenteric artery from aorta

beginning and upper limit of duodenum

Question 3

Where is the subcostal plane?

Answer 3

passes through the body of L3 vertebra, lower border of 10th costal cartilage, lowest parts of the costal margins

Origin of inferior mesenteric artery

3rd part of duodenum lie on this plane

The umbilicus passes below it at level of L3/4 intervertebral disc

Question 4

Where is the transtubercular/ intertubercular plane?

Answer 4

passes through the tubercles of iliac crests and the body of L5

halfway between transpyloric plane and pubic symphysis

Question 5

How are the nine regions of the abdomen formed and what are the names of the regions?

Answer 5

Question 6

How are the four abdominal quadrants formed?

Answer 6

Vertical- median plane- imaginary line following linea alba from xiphoid process to pubic symphysis

Horizontal- transumbilical plane- imaginary horizontal line at the level of the umbilicus

Question 7

What is the peritoneum?

Answer 7

The serous membrane that lines the abdominal cavity and the organs within it

Serous membrane produces fluid can be seperated into parietal and visceral, however these two layers are one continuous sheet

Parietal- lines and surrounds the abdominal cavity

visceral- surrounds the viscera

space between peritoneum- peritoneal cavity- contains peritoneal fluid- helps lubricate the movement and expansion of the gut

Question 8

What is omentum and where are the greater omentum and lesser omentum located?

Answer 8

Omentum- double layered fold of peritoneum

Greater omentum

• hangs down from greater curvature of stomach and proximal duodenum
• folds back on itself to attach to transverse colon

Lesser Omentum

• goes from the lesser curvature of the stomach and the proximal part of the duodenum to the liver
• consists of two parts
  
  • hepatogastric ligament
  • hepatoduodenal ligament

Question 9

What is a mesentery?

Answer 9

when viseral peritoneum doubles up around an organ and attaches it to the posterior abdominal wall

• provides pathway for neurovascular supply between organ and body wall
• contains lymph nodes and variable amount of fat
• Mesentery is mesentery of small intestine
• Mesocolon is mesentery of large intestine

Question 10

Where are the greater sac and lesser sac located?

Answer 10

Greater sac- extending from surface of liver all the way to pelvic cavity

Lesser sac- behind stomach and liver

The greater and lesser sac communicate via the epiploic foramen

Question 11

What is the difference between intraperitoneal and retroperitoneal organ?

Answer 11

Intraperitoneal organ

• any organ covered by visceral peritoneum and is suspended within the peritoneal cavity
• i.e. stomach, liver, spleen

Retroperitoneal organ- parietal peritoneum covering only the anterior surface

Mneumonic- SAD PUCKER

• Suprarenal (adrenal) gland
• Aorta/IVC
• Duodenum ( except the proximal 2cm, the duodenal cap)
• Pancreas (except the tail)
• Ureters
• Colon (Asc. and Desc)
• Kidneys
• Eosophagus
• Rectum
• Primary retroperitoneal- organs that develop and remain beneath parietal peritoneum- only kidneys
• Secondary retroperitoneal- organs that develop with short mesentery. The mesentery become fused with the parietal peritoneum

Question 12

What is the difference in afferent nerve supply between parietal and visceral peritoneum?

Answer 12

Parietal peritoneum

• recieves same somatic nerve supply as the region of the abdominal wall that it lines ( lower 6 thoracic nerves and first lumbar nerve)
• Pain- well localised
• sensitive to pressure, pain, laceration and temperature

Visceral peritoneum

• same autonomic nerve supply as the viscera it covers
• Pain- poorly localised
• referred to dermatomes which are supplied by the same sensory ganglia and spinal cord segments as the nerve fibres innervating the viscera

Question 13

What is a recess?

Answer 13

Recess- spaces formed by the peritoneum covering the viscera

Question 14

What are the two compartments of the greater sac?

Answer 14

The greater sac is divided into two compartments by the transverse mesocolon

• Supracolic compartment- above the transverse mesocolon, contians stomach, liver, spleen
• Infracolic compartment- below the transverse mesocolon and contains the small intestine, ascending and descending colon. The infracolic compartment is further divided into left and right infracolic spaces by the mesentery of the small intestine
• The compartments are connected by the paracolic gutters which lie between the posterolateral abdominal wall and the lateral aspect of ascending and descending colon

Question 15

Where are the left and right subphrenic recess found and what are their clinical relevance?

Answer 15

Left and right subphrenic recess are found between the diaphragm and liver, seperated by the falciform ligament

Subphrenic abcess- accumulation of pus, pus from the appendix can track up to the subphrenic space via the right paracolic gutter

Question 16

What is the hepatorenal recess (posterior right subhepatic space) and what is the clinical relavance?

Answer 16

Space between the right kidney and liver

Ascites and haemoperitoneum can occur in this space

Question 17

What is ascites?

Answer 17

• accumulation of fluid in the peritoneal cavity
• may form secondary to peritonitis and infections
• commonly caused by portal hypertension
• abdomen become grossly distended
• Paracentesis- drain ascitic fluid, diagnostic purpose

Question 18

What is peritonitis?

Answer 18

Inflammation of the peritoneum

• localised- i.e. secondary to appendicitis
• generalised- i.e. secondary to bowel perforation
• Reflex tensing (guarding) of the overlying musculature leading to abdominal rigidity ( contraction of ther anterolateral abdominal muscles)

Question 19

Where are the following spaces located:

• Rectovesical pouch
• Vesicouterine pouch
• Rectouterine pouch

Answer 19

Rectovesicle pouch- male, double folding of peritoneum between the rectum and bladder, peritoneal cavity completely closed

Vesicouterine pouch- female, double folding of peritoneum between the anterior surface of the uterus and bladder

Rectouterine pouch- female, double folding of the peritoneum betweeen rectum and posterior wall of the uterus

• The peritoneal cavity is not completely closed in females, the uterine tubes open into the peritoneal cavity- infections of the vagina, uterus or uterine tubes may lead to peritonitis

Question 20

What is the inguinal canal and its clinical relavance?

Answer 20

The inguinal canal is a gap in the inferior part of the anterior abdominal wall just above the medial half of the inguinal ligament

it is of clinical importance as a potential weakness in the abdominal wall, and thus a common site of herniation

Direct inguinal hernia

• usually acquired in adulthood, due to weakening of abdominal musculature
• protrude into the inguinal canal via the posterior wall medial to the epigastric vessels and can enter the superficial ring

Indirect inguinal hernia

• caused by the failure of processus vaginalis to regress
• enters the inguinal canal through the deep inguinal ring, lateral to the epigastric vessel
• may continue through the superficial ring into the scrotum

Question 21

Describe the major incision sites of the abdomen

Answer 21

Midline- incision through the linea alba, linea alba poorly vascularised, minimal blood loss, major nerves avoided

Paramedian- provides access to more lateral structures- kidney, spleen, adrenals, ligates blood and nerve supply to muscles medial to the incision- atrophy

Kocher- begins inf to xiphoid process and extends inferolaterally in parallel to the right costal margin, access to gallbladder and biliary tree

McBurney- Mcburney’s point- 1/3 distance between ASIS and the umbilicus