EXAMPLE Peritoneum and associated structures Stomach ! Abdominal - - PDF document

Stomach

!

• Abdomen: diaphragm to pelvic brim
• Antero-lateral muscular wall: external oblique,

• Posterior: quadratus lumborum, psoas, spine
• Anterior wall supply:
• External iliac → inferior epigastric → superior

• Peritoneum = single-cell layer that covers organs and

• If visceral peritoneum only on anterior =

• Mesentery = double-layer of peritoneum
• Connects small bowel to posterior wall and

• Greater sac divided by the transverse

• Behind gastro-hepatic ligament = lesser sac
• Contains gastro-epiploic foramen (of

• Omentum connects stomach to other organs
• Lesser - liver
• Greater - transverse colon
• Foregut: mid-oesophagus to ampulla of Vater, coeliac

EXAMPLE

• Midgut: to ⅔rd transverse colon,

• Hindgut: to dentate line (rectum),

!

• Anterior: diaphragm, transverse colon,

• Posterior: pancreas, spleen, kidney
• Supply: right & left gastric,

• Drain to splenic and superior

• Extra (external) oblique muscle layer
• Functions:
• Store & regulate release
• Protein & vit B12 digestion
• Immune defence
• Cephalo-gastric and gastro-gastric

• Rugae also help filling

EXAMPLE

• Competent if sphincter pressure exceeds gastric pressure, contributing factors:
• Muscular (physiological) sphincter itself
• Increase in intra-abdominal/-thoracic pressure with coughing, talking, exhalation
• Acute angle between oesophagus & stomach with mucosal flaps
• Gravity relatively minor role
• Gastro-oesophageal reflux disease (GORD): pain, cough, regurgitation
• Chronic oesophagitis may give Barrett's metaplasia (to gastric type)
• Increased cancer risk

• Parietal cells secrete H+ via proton pump (H+-

• Target for proton pump inhibitors (e.g.
• meprazole)
• Basolateral HCO3- excretion (for Cl-) makes alkaline

• Control:
• Vagal innervation of parietal cells increases

• Indirectly: via gastrin from G-cells and

• Gastrin reduced by secretin (from duodenal S-cells in response to acid)
• Histamine (ECL cells) increases acid production at H2-R on parietal cells
• Target for histamine antagonists (e.g. ranitidine)
• Somatostatin inhibits directly on parietal cells
• Indirectly: via reducing histamine production from ECL cells
• Mucus increased by ACh (therefore at same time as acid) using PGE2
• Use of NSAIDs reduce PG production and predisposes to gastritis/ulcers

EXAMPLE

• Gastric motility
• Mixing in corpus
• Propulsion moves towards

• Retropulsion back from

• Pylorus relaxes in response

!

Small bowel

!

• Duodenum: superior (coeliac) &

• Posterior to 1st: common bile

• Posterior to 2nd: right kidney and

• 3rd: around head of pancreas,

• 4th: ligament of Trietz at

• Histology:
• Brunner's glands: deep, alkaline-secreting, only in duodenum

• Bacterium specialised to living in stomach
• Associated with peptic ulcer disease
• Urease produces an alkaline coat
• Flagella to bury into mucus
• Inhibits somatostatin secretion → increases acid

EXAMPLE

• Simple columnar with microvilli
• Jejunum (2/5th): thicker with smaller lumen
• Plicae circulares (/valvulae conniventes) = folds in small bowel
• Villae (= mucosae) with crypts of Leiberkuhn at base (new cells produced at base)
• Peyer's patches = lymphoid aggregates
• B-cells make secretory IgA that prevent pathogen adhesion
• Panneth cells secrete lysozyme

! ! ! ! ! ! ! ! ! !

!

• Basolateral Na+/K+-ATPase gives concentration gradient for apical facilitated diffusion:

• Water via osmosis through leaky occluding junctions in upper GIT and small bowel
• Large bowel through aquaporins and transcellular movement
• More controlled
• K+ and Cl- move by paracellular transport; plus H+/K+-ATPase absorbs K+ in colon

!

• Facilitated uptake in duodenum - binds calbindin inside cells (keeps gradient)
• Basolateral efflux by Ca2+-ATPase or Na+/Ca2+-antiporter
• PTH increases channel activity and vitamin D increases calbindin synthesis

!

• Peritoneal cavity has a greater and lesser sac, separated by the

• Mesentery is double-layered peritoneum containing neurovascular

• Gastric parietal cells produce acid using H+/K+-ATPase
• Duodenum is retroperitoneal and is both fore- & mid-gut

EXAMPLE