GI Flashcards
What is gastroschisis?
Congenital malformation of the anterior abdominal wall causing extrusion of abdominal contents.
Not covered by peritoneum
What is derived from the foregut?
Midgut?
Hindgut?
Foregut - Pharynx to duodenum, liver, gallbladder, pancreas
Midgut - Duodenum to transverse colon
Hindgut - Distal transverse colon to rectum
What is an omphalocele?
Failure of intestines to return to body cavity after herniation into the umbilical cord. Covered by peritoneum
What causes intestinal atresia?
Duodenal atresia - failure to recanalize
Jejunal, ileal, colonic atresia - vascular accident in-utero
Vascular accident can cause apple peel syndrome where distal atrophic gut is wrapped around an artery.
When does midgut rotation occur?
6th week –> midgut herniates through umbilical ring
10th week –> abdominal cavity is large enough & midgut returns to it & rotates around SMA
Failure can cause malrotation of midgut or omphalocele
What are the possible types of tracheoesophageal abnormalities?
Which is most common?
Most common is EA with distal TEF
Others:
Pure EA
Pure TEF (H-type; fistula present but esophagus still patent)
What is seen with EA+TEF?
Drooling Choking with first feeding Cyanosis (laryngospasm to prevent reflux aspiration) Air in the stomach on CXR Failure to pass NG tube into stomach
What can result from malformation of the pancreas?
Annular pancreas - ventral pancreatic bud encircles 2nd part of duodenum & may cause narrowing. Due to failure of migration.
Pancreas divisum - Common; dorsal & ventral buds fail to fuse so that most pancreatic acini drain to minor sphincter. Predisposes to chronic pancreatitis.
From where does the spleen arise?
Arises from mesoderm but is supplied by foregut (celiac artery)
The other gut structures are all endodermal.
What are the retroperitoneal structures?
SAD PUCKER
Suprarenal glands Aorta & IVC Duodenum (2nd & 3rd parts) Pancreas (except tail) Ureters Colon (ascending & descending) Kidneys Esophagus (lower 2/3) Rectum (lower 2/3)
What is the falciform ligament?
Connects the liver to the anterior abdominal wall
Contains ligamentum teres (derivative of fetal umbilical vein)
What ligament contains the portal triad?
Hepatoduodenal ligament
Portal triad = hepatic artery, portal vein, common bile duct
What is the difference between an erosion and an ulcer?
Erosion = mucosa only
Ulcer = submucosa or deeper
What is the frequency of electrical rhythm along the GI tract?
Stomach = 3 waves/min
Duodenum = 12 waves/min
Ileum = 8 waves/min
What are the layers of the gut wall?
1) Mucosa (epithelium, lamina propria, muscularis mucosa)
2) Submucosa (includes Submucosal/Meissner’s plexus)
3) Muscularis externa (includes Myenteric/Auerbach’s plexus)
4) Serosa (intraperitoneal) or Adventitia (retroperitoneal)
What is the duodenum composed of histologically?
Villi & microvilli
Brunner’s glands (unique to duodenum; HCO3-)
Crypts of Lieberkuhn (throughout small & large intestine)
What is the histology of the ileum?
Peyer’s patches (unique to ileum)
Largest # of goblet cells in SI
Plicae circularis (along with jejunum)
Crypts of Lieberkuhn
What can result from failure of the vitelline (omphalomesenteric) duct to obliterate?
When should it obliterate?
Meckel diverticulum
Persistent vitelline duct
Vitelline cyst
Vitelline sinus
Should obliterate during the 7th week
What does an acid fast stain bind to?
Mycolic acid (TB, Nocardia)
What can cause papillary necrosis?
Sickle cell disease or trait
Analgesic use
Diabetes
Acute pyelonephritis
When is a child at risk for hemolytic disease of the newborn?
Anti-A or Anti-B Ig’s are formed early in life. If a mother is A or B, she will form IgM (cannot cross placenta). If she is O, she will form IgG (can cross placenta). Thus, even her first child is at risk.
Mothers must be inoculated (with the first birth) against Rh. Subsequent births are at risk.
What is the difference in mechanism between unfractionated heparin and LMW heparin?
Unfractionated heparin binds Xa & IIa equally
LMW heparin preferentially binds Xa
*Antithrombin is needed in both cases to form the ternary inactive complex (heparin, AT, Xa/IIa)
What is the function of human Placental Lactogen (hPL)?
Insulin resistance –> fetus gets more of the glucose
^Lipolysis, proteolysis –> energy for both mom & fetus
hPL levels rise throughout gestation to support a growing fetus
What can be seen as a side effect of massive amounts of blood transfusions?
If a patient gets an entire body content of blood (5L) in under 24h, citrate from the blood products (additive) can accumulate and chelate the blood calcium causing hypocalcemia.
Where do the nitrogen atoms in urea come from?
Free NH3 (alanine cycle) Aspartate (added into the urea cycle)
How id carbamoyl phosphate synthetase I regulated?
Rate-limiting enzyme in the urea cycle
It is activated by N-acetylglutamate
What physical exam findings are more specific for iron deficiency anemia?
Dysphagia Spoon nails (koilonychia)
What growth factors are responsible for angiogenesis?
FGF
VEGF
This is true both in granulation tissue & in tumorgenesis
What is the receptor for rabies virus in the body?
Nicotinic ACh receptor
What is the cellular receptor for CMV?
Cellular integrins
What is the cellular receptor for Rhinovirus?
ICAM1
What murmurs can be heard better with the patient leaning forward?
Aortic murmurs
It brings the valve close to the chest wall
What can cause Pure Red Cell Aplasia?
Thymoma (auto-Ab's) Lymphocytic leukemia (auto-Ab's) Parvovirus infection
PRCA is selective aplastic anemia seen with erythroblasts but sparing granulopoiesis & thrombopoiesis.
What are the effects of dobutamine?
Selective B1 agonist
Inotropy > Chronotropy
^Contractility
^Cardiac conduction velocity (proarrhythmic)
^Myocardial O2 consumption
What drains the lower limbs & male genitalia?
Testis –> para-aortic
Penis & cutaneous calf –> deep inguinal
Scrotum & rest of leg –> superficial inguinal
Where does HBV acquire its envelope?
Endoplasmic reticulum
How does HBV use its reverse transcriptase?
The viral mRNA transcript is packaged into a capsid & RT acts on it to produce circular DNA that is partially ds. This is the infective form of HBV.
What toxicity is seen with Vincristin/Vinblastine?
Neurotoxicity
They inhibit MT assembly & thus axonal transport in neurons.
What are the vegetations of bacterial endocarditis composed of?
Platelets
Fibrin
Bacteria
What causes bronchiolitis?
Bronchiolitis is viral
It is inflammation of the bronchioles (smallest air passageways).
What is the DDx for absent thymic shadow?
SCID
DiGeorge syndrome
What is the cause of Leukocyte Adhesion Deficiency 1 (LAD1)?
Absence of LFA-1 (CD18), an integrin required for leukocyte tight adhesion.
What is the cause of Leukocyte Adhesion Deficiency 2 (LAD2)?
Impaired formation of Sialyl-Lewis carbohydrate ligands on leukocytes, leading to impaired selectin binding.
It is a milder form of LAD than LAD1 & LAD3. No delayed separation of the umbilical cord.
What is seen with leukocyte adhesion deficiency 3 (LAD3)?
Delayed separation of the umbilical cord (Types 1 & 3)
Recurrent skin infections without pus formation
Bleeding complications
What is the blood supply to the lesser curvature of the stomach?
Greater curvature?
Lesser curvature:
Proximal - Left gastric
Distal - Right gastric
Greater curvature:
Proximal - Left gastroepiploic
Distal - Right gastroepiploic
What are the GI watershed zones?
Splenic flexure
Sigmoid colon/rectum
What are the sites of porto-systemic venous anastomoses?
Portal–>Systemic:
Left gastric–>Esophageal
Paraumbilical–> Epigastric & lateral thoracic
Superior rectal–>Middle & inferior rectal
Together cause esophageal varices, caput medusae, & hemorrhoids
What are means of drug administration that bypass 1st pass metabolism?
IV
SubQ
Sublingual
Rectal suppository
What is the blood supply to/from the anus?
Above pectinate: Superior rectal (IMA)–>Superior rectal (portal)
Below pectinate: Inferior rectal (int. pudendal)–>Inf. rectal (IVC)
What is the lymphatic drainage of the anus?
Above pectinate line - deep nodes
Below pectinate line - superficial inguinal nodes
Where is the most common location of an anal fissure?
On the midline posterior wall of the anus, below the pectinate line
Presents with BRBPR & pain w/ defecation
What are the zones of a hepatic lobule?
Which are affected first by insults?
Zone 1 = periportal - affected 1st by viral hepatitis
Zone 2
Zone 3 = centrilobular - affected 1st by ischemia, EtOH, drugs
Just remember periportal is affected by (zone) 1 thing - viruses
What is the organization of the femoral region?
Going from lateral–>medial: NAVL
Nerve
Artery
Vein
Lymphatics
What is contained in the femoral sheath?
Femoral triangle?
Femoral sheath: Femoral artery, vein, & deep inguinal LN’s
(not the nerve)
Femoral triangle: Femoral nerve, artery, vein (not the femoral canal)
What are the types of diaphragmatic hernias?
Sliding hiatal hernia:
Most common
GE junction displaced upward
“Hourglass stomach”
Paraesophageal hernia:
Fundus protrudes into thorax next to esophagus
Both can cause GERD
What patient populations are the various abdominal hernias associated with?
Indirect - male infants (patent processus vaginalis)
Direct - older males (weakened abdominal wall)
Femoral - women
Where is an indirect hernia located?
What layers cover it?
Lateral to inferior epigastric artery. Goes through deep inguinal ring –> superficial inguinal ring –> scrotum
Covered by all 3 layers of spermatic fascia.
Where is a direct hernia located?
What layers cover it?
Medial to inferior epigastric artery.
Protrudes through Hasselbach’s triangle (through abd wall) –> superficial inguinal ring –> can extend into scrotum
Covered by external spermatic fascia only.
Where is a femoral hernia located?
Below inguinal ligament & lateral to pubic tubercle.
The leading cause of bowel incarceration (smaller hole)
More common in women.
What form the borders of Hasselbach’s triangle?
Rectus abdominus
Inguinal ligament
Inferior epigastric vessels
This is the site of a direct inguinal hernia.
Gastrin
Secreted by:
Effects:
Regulation:
Secreted by: G cells in gastric antrum
Effects: ^acid secretion, motility, growth of gastric mucosa
Regulation: ^ by amino acids, vagal stim, stomach distention, ^pH
Can be ^ with chronic PPI use. Phenylalanine & tryptophan are the strongest stimulators.
Cholecystokinin
Secreted by:
Effects:
Regulation:
Secreted by: I cells of duodenum/jejunum
Effects: ^pancreatic secretion, GB contraction, spincter of Oddi relaxation, decreases gastric emptying
Regulation: ^ by fatty acids & amino acids
Secretin
Secreted by:
Effects:
Regulation:
Secreted by: S cells in duodenum
Effects: ^pancreatic HCO3- secretion, ^bile secretion, inhibits gastric acid secretion
Regulation: ^by acid, ^by FA’s in duodenum
Somatostatin
Secreted by:
Effects:
Regulation:
Secreted by: D cells of pancreatic islets & GI mucosa
Effects: Inhibits secretion of gastric acid & pancreatic secretion, inhibits GB contraction, inhibits insulin & glucagon release
Regulation: ^ by acid, inhibited by vagal stimulation
Glucose-dependent insulinotropic peptide (GIP)
Secreted by:
Effects:
Regulation:
Secreted by: K cells of duodenum & jejunum
Effects: decreases gastric acid secretion, ^insulin release
Regulation: ^by fatty acids, amino acids, oral glucose
Vasoactive Intestinal Peptide (VIP)
Secreted by:
Effects:
Regulation:
Secreted by: Parasympathetic ganglia
Effects: ^intestinal water & electrolyte secretion, ^relaxation of smooth muscle & sphincters
Regulation: ^by vagal stimulation, decreased by adrenergics
What is seen with a VIPoma?
WDHA syndrome:
Watery Diarrhea
Hypokalemia
Achlorhydria
Seen as a non-alpha/non-beta pancreatic cell tumor.
Motilin
Secreted by:
Effects:
Regulation:
Secreted by: Small intestine
Effects: Produces migrating motor complexes (MMC’s)
Regulation: ^during fasting state, stimulated by erythromycin
How is B12 absorbed?
Binds Haptocorrin (R-factor) in saliva –> binds intrinsic factor (parietal cells) –> absorbed in TERMINAL ILEUM
What is secreted by parietal cells of the stomach?
Chief cells?
Parietal cells - Gastric acid, intrinsic factor
Chief cells - Pepsinogen (activated to pepsin by acid)
How is salivation regulated?
Salivation is increased by both sympathetic & parasympathetic activity
How does vagal stimulation cause gastric acid secretion?
1) GRP synapse on G cells –> Gastrin in circulation –> ECL cells release histamine –> parietal cells respond
(most important mechanism)
2) GRP synapse on G cells –> Gastrin stimulates parietal cells
3) Direct ACh synapse on parietal cells
What type of pump is located on the gastric parietal cell membrane?
H+/K+ ATPase exchanger
What substances act on the parietal cell to modulate gastric acid secretion?
Stimulate:
ACh (M3)
Gastrin (Gq)
Histamine (H2)
Inhibit (Gi):
Prostaglandins
Somatostatin