GI Flashcards
Foregut
Pharynx → duodenum
Midgut
Duodenum → proximal 2/3 of transverse colon
Hindgut
Distal 1/3 of transverse colon to anal canal above pectinate line
Midgut development
- 6th week → physiologic midgut herniates through umbilical ring
- 10th week → returns to abdominal cavity + rotates around superior mesenteric artery (SMA), total 270 degree counterclockwise
Defect rostral fold closure
Sternal defects
Defect lateral fold closure
Omphalocele, gastroschisis
Defect caudal fold closure
Bladder exstrophy
Duodenal atresia
- Failure to recanalize
- Dilation of the stomach and proximal duodenum (“double bubble” on x-ray)
- Associated with Down syndrome
Jejunal and ileal atresia
- Disruption of mesenteric vessels
- Ischemic necrosis
- Segmental resorption (bowel discontinuity or “apple peel”)
Hypertrophic pyloric stenosis is associated with exposure to
Macrolides
Hypertrophic pyloric stenosis is associated with what type of alkalosis
Results in hypokalemic and hypochloremic metabolic alkalosis (secondary to vomiting of gastric acid and subsequent volume contraction)
Annular pancreas
Ventral pancreatic bud abnormally encircles 2nd part of the duodenum. Forms a ring of pancreatic tissue that may cause duodena narrowing and nonbilious vomiting.
Pancreas divisum
Ventral and dorsal parts fail to fuse at 8 weeks. Common anomaly, mostly asymptomatic but may cause chronic abdominal pain and/or pancreatitis
Embryology of spleen
Arises in mesentery of stomach (hence is mesodermal) but has foregut supply (celiac trunk → splenic artery)
Retroperitoneal structures
Include GI structures that lack a mesentery and non-GI structures. Injuries to retroperitoneal structures can cause blood or gas accumulation in the retroperitoneal space.
- Suprarenal (adrenal) glands
- Aorta and IVC
- Duodenum (2nd through 4th parts)
- Pancreas (except tail)
- Ureters
- Colon (descending and ascending)
- Kidneys
- Esophagus (thoracic portion)
- Rectum (partially)
“SAD PUCKER”
Superior mesenteric artery syndrome
Characterized by intermittent intestinal obstruction symptoms (primarily postprandial pain) when transverse (3rd) portion of duodenum is compressed between the SMA and aorta. Typically occurs in conditions associated with diminished mesenteric fat (eg low body weight/malnutrition)
Branches of celiac trunk
Common hepatic, splenic, and left gastric
Kupffer cells
Specialized macrophages that form the lining of sinusoids
Hepatic stellate (Ito) cells
Located in space of Disse and store vitamin A when quiescent and produce extracellular matrix when activated.
Zone I
- Periportal zone
- Affected 1st by viral hepatitis
- Ingested toxins (eg cocaine)
Zone II
- Intermediate zone
- Yellow fever
Zone III
- Pericentral vein (centrilobular) zone
- Affected 1st by ischemia
- Contains cytochrome P450 system
- Most sensitive to metabolic toxins
- Site of alcoholic hepatitis
Painless jaundice
Usually caused by tumors that arise in the head of pancreas (usually ductal adenocarcinoma) that can cause obstruction of the common bile duct
Layers of spermatic cord and their derivatives
- Internal spermatic fascia (transversalis fascia)
- Cremasteric muscle and fascia (internal oblique)
- External spermatic fascia (external oblique)
“ICE tie”
Carbohydrate absorption
- Only monosaccharides (glucose, galactose, fructose) are absorbed by enterocytes
- Glucose and galactose are taken up by SGLT1 (Na+ dependent)
- Fructose is taken up by facilitated diffusion by GLUT-5
- All are transported to blood by GLUT-2
- D-xylose absorption test: distinguishes GI mucosal damage from other causes of malabsorption
Where is iron absorbed
Duodenum
Where is folate absorbed
Small bowel, therefore clinically relevant in patients with small bowel disease or after resection.
Where is B12 absorbed
Terminal ileum along with bile salts, requires intrinsic factor
Pleomorphic adenoma
- Salivary gland tumor
- Benign mixed tumor
- Most common salivary gland tumor
- Composed of chondromyxoid stroma and epithelium and recurs if incompletely excise or ruptured intraoperatively
Mucoepidermoid carcinoma
- Salivary gland tumor
- Most common malignant tumor
- Has mucinous and squamous components