Abdominal cavity and GIT

Question 1

Where are intraperitoneal and retroperitoneal structures located?

Answer 1

Intraperitoneal structures suspended on mesenteries within the peritoneal cavity
Retroperitoneal structures are within abdominopelvic cavity but outside peritoneum or peritoneal cavity

Question 2

Define the greater and lesser sacs and think about spread of infection

Answer 2

Greater sac is main compartment and extends from diaphragm down into pelvis - think of infection spread or bleeding in cavity or how surface area may be used for dialysis

Lesser sac smaller and lies behind the stomach and lesser omentum but extends slightly into greater omentum. In males the peritoneum is closed cavity but in females there is communication with exterior through thr uterine tubes, uterus and vagina - may allow infection spread from exterior to inside peritoneal cavity

Question 3

Peritoneal spaces

Answer 3

Potential spaces and recesses that can house pus or blood or allow the spread of either
One example is right posterior subphrenic or hepatorenal space (Morison’s pouch)

Question 4

Nerve supply to peritoneum

Answer 4

Parietal peritoneum is sensitive to pain, temp, touch and pressure
Ant abdominal wall supplied by same nerves that supply the skin above - T7-12 and L1
Diaphragmatic peritoneum supplied by phrenic nerves - C3-5 - referred pain to shoulder tip
Parietal peritoneum in pelvis supplied mainly by obturator nerve - L2-4

Visceral peritoneum sensitive only to stretch (distension) and tearing and is not sensitive to touch, pressure or temp
Supplied by autonomic afferent nerves that re travelling with autonomic efferent (usually symp) nerves that are parallel to BVs
Brain cannot localise visceral pain caused by distension and often referred to a dermatome e.g. appendix pain refers to T10 dermatome

Question 5

Describe oesophagus route through body and describe muscle in it

Answer 5

Starts at C6
Inferiorly it swings forwards and to left before piercing diaphragm at T10

Upper third - striated muscle as swallowing is voluntary and rapid
Middle third - mixed
Lower third - smooth muscle, involuntary

Question 6

Describe abdominal oesophagus?

Answer 6

Short distal part in abdominal cavity that passes from oesophageal hiatus of diaphragm to cardiac orifice of stomach
Lined by stratified squamous epithelium with submucosal mucous glands (lubrication) and has smooth muscle walls

Arterial supply is from left gastric artery and inferior phrenic nerve, therefore venous drainege to portal vein

Question 7

Cardiac sphincter of oesophagus

Answer 7

There is no anatomical sphincter at cardiac end of oesophagus, reflux prevented by a physiological cardiac sphincter

1. Contraction of right crus of diaphragm
2. Tonic contraction of circular layer of smooth muscle in lower oesophagus
3. Valvular effect of oblique entry of oesophagus into stomach, augmented by oblique muscle layer

Closure of sphincter under vagal control and augmented by gastrin and reduced in response to secretin, glucagon

Question 8

What are the four parts of the stomach?

Answer 8

Cardia
Fundus
Body
Pyloric part (pyloric antrum and pyloric canal)

Question 9

What is the SI consisted of?

Answer 9

Extends from pylorus of stomach to ileocaecal junction
Divided into duodenum, jejunum and ileum

Duodenum is adjacent to head of pancreas, mainly retroperitoneal and receives openings of bile and pancreatic ducts. Functions are continued digestion, esp of fats and absorption

Jejunum and ileum are intraperitoneal and suspended on variable mesentery so mobile, continues absorption, empties into caecum at ileo-caecal valve

Question 10

Intestinal lymph drainage via mesentery

Answer 10

The mucous membrane of SI is raised in multiple villi to hugely increase absorptive SA
There is a lacteal in centre of each villus for absorption f digested fats and lipids (chyle)
The chyle passes from lacteals into mesenteric lymph channels that do not pass through lymph nodes but converge on cisterna chyli that lies in upper abdomen and passes through diaphragm as thoracic duct

Int wall is packed with lymphocytes, in ileum these aggregate as Peyer’s patches, lymph absorbed from int wall again passes into mesenteric lymph channels, but these filter through the mesenteric nodes

Question 11

The intestinal tract communicated with yolk sac in embryo - what might this leave?

Answer 11

Meckel’s diverticulum
2 inches long, 2 feet from end of ileum

Remnant of vitelo-intestinal duct and may ulcerate causing appendicitis symptoms and signs

Question 12

Colon/LI

Answer 12

From caecum to rectum and anal canal
Consists of caecu, ascending colon, hepatic (right) flexure), transverse colon, splenic (left) flexure, descending colon, sigmoid colon to rectum and anal canal
Ascending and descending parts are retroperitoneal, while transverse and sigmoid colon are on a mesentery i.e. intraperitoneal

Question 13

Appendix

Answer 13

Narrow blind ended tube hanging from caecum
Its submucosa is packed full of lymphoid tissue
Suspended on a short but highly variable meso-appendix that transmits the appendicular vessels

The appendicular artery is derived from superior mesenteric (from aorta at L1) with nerves derived from T10/11. Therefore early appendicitis refers to peri-umbilical region, pain moves to the right inguinal region later when parietal peritoneum involved
Appendicular artery close and parallel to appendix distally so may be affected by inflamed appendix - gangrene and rupture

Question 14

Rectum

Answer 14

Passes downwards following curve of sacrum and coccyx and ends in front of tip of coccyx by piercing pelvic diaphragm levator ani and becoming continuous with anal canal

rectum is retroperitoneal, anal canal is in perineum