Gastrointestinal- anatomy Flashcards
Retroperitoneal structures
SAD PUCKER: 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)
Important gastrointestinal ligaments
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Layers of gut wall
MSMS:
Mucosa—epithelium, lamina propria, muscularis mucosa
Submucosa—includes Submucosal nerve plexus (Meissner), Secretes fluid
Muscularis externa—includes Myenteric nerve plexus (Auerbach), Motility
Serosa (when intraperitoneal), adventitia (when retroperitoneal)
*Ulcers can extend into submucosa, inner or outer muscular layer. Erosions are in the mucosa only.
Frequencies of basal electric rhythm (slow waves):
Stomach—3 waves/min
Duodenum—12 waves/min
Ileum—8–9 waves/min
Digestive tract histology
- Esophagus
- Stomach
- Duodenum
Nonkeratinized stratified squamous epithelium.
Gastric glands
Villi and microvilli absorptive surface. Brunner glands (HCO3− secreting cells of submucosa) and crypts of Lieberkühn (contain stem cells that replace enterocytes/goblet cells and Paneth cells that secrete defensins, lysozyme, and TNF).
Digestive tract histology
- Jejunum
- Ileum
- Colon
Plicae circulares (also present in distal duodenum) and crypts of Lieberkühn.
Peyer patches, plicae circulares (proximal ileum), and crypts of Lieberkühn. Largest number of goblet cells in the small intestine.
Crypts of Lieberkühn but no villi; abundant goblet cells.
Abdominal aorta and branches
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Superior mesenteric artery syndrome
Characterized by intermittent intestinal obstruction symptoms (primarily postprandial pain) when SMA and aorta compress transverse (third) portion of duodenum.
Typically occurs in conditions associated with diminished mesenteric fat (eg, low body weight/malnutrition).
Two areas of the colon susceptible in colonic ischemia:
Splenic flexure—SMA and IMA
Rectosigmoid junction—the last sigmoid arterial branch from the IMA and superior rectal artery
Celiac trunk
Branches of celiac trunk: common hepatic, splenic, and left gastric.
Duodenal ulcers
Posterior duodenal ulcers penetrate gastroduodenal artery causing hemorrhage.
Anterior duodenal ulcers perforate into the anterior abdominal cavity, potentially leading to pneumoperitoneum.
Portosystemic anastomoses
- Site of anastomosis + Clinical sign + portal↔ systemic
- Esophagus. Esophageal varices. Left gastric ↔ azygos
- Umbilicus. Caput medusae. Paraumbilical ↔ small
epigastric veins of the anterior abdominal wall. - Rectum. Anorectal varices. Superior rectal ↔ middle and inferior rectal
transjugular intrahepatic portosystemic shunt (TIPS)
between the portal vein and hepatic vein relieves portal hypertension by shunting blood to the systemic circulation, bypassing the liver. Can precipitate hepatic encephalopathy.
Pectinate (dentate) line
- Above
- Below
internal hemorrhoids, adenocarcinoma. Internal hemorrhoids receive visceral innervation and are therefore not painful.
external hemorrhoids, anal fissures, squamous cell carcinoma. External hemorrhoids receive somatic
innervation (inferior rectal branch of pudendal nerve) and are therefore painful if thrombosed.
Anal fissure
Tear in the anal mucosa below the Pectinate line. Pain while Pooping; blood on toilet Paper.
Located Posteriorly because this area is Poorly Perfused.
Associated with low-fiber diets and constipation.
Liver tissue architecture
The functional unit of the liver is made up of hexagonally arranged lobules surrounding the central vein with portal triads on the edges (consisting of a portal vein, hepatic artery, bile ducts, as well lymphatics)
Liver tissue architecture
- Zone I—periportal zone:
- Zone II—intermediate zone:
- Zone III—pericentral vein (centrilobular) zone:
Affected 1st by viral hepatitis
Ingested toxins (eg, cocaine)
Yellow fever
Affected 1st by ischemia
High concentration of cytochrome P-450
Most sensitive to metabolic toxins (eg, ethanol, CCl4, halothane, rifampin)
Site of alcoholic hepatitis
Tumors that arise in head of pancreas (ductal adenocarcinoma)
can cause obstruction of common bile duct enlarged gallbladder with painless jaundice (Courvoisier sign).
Femoral region
Femoral triangle
Femoral sheath
you go from lateral to medial to find your “NAVeL”
- Lateral to medial: Nerve-Artery-Vein-Lymphatics
Contains femoral nerve, artery, vein. (inguinal ligament, sartorious and adductor longus)
Fascial tube 3–4 cm below inguinal ligament. Contains femoral vein, artery, and canal (deep inguinal lymph nodes) but not femoral nerve
Spermatic cord
ICE tie
- Internal spermatic fascia (transversalis fascia)
- Cremasteric muscle and fascia (internal oblique)
- External spermatic fascia (external oblique)
Inguinal canal
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Diaphragmatic hernia
Abdominal structures enter the thorax. Commonly occurs on left side due to relative protection of right hemidiaphragm by liver. Most commonly a hiatal hernia.
Sliding hiatal hernia
gastroesophageal junction is displaced upward as gastric cardia slides into hiatus; “hourglass stomach.” Most common type
Paraesophageal hiatal hernia
gastroesophageal junction is usually normal but gastric fundus protrudes into the thorax.
Indirect inguinal hernia
Goes through the internal (deep) inguinal ring, external (superficial) inguinal ring, and into the scrotum.
Caused by failure of processus vaginalis to close (can
form hydrocele). May be noticed in infants or discovered in adulthood.
Direct inguinal hernia
Protrudes through the inguinal (Hesselbach) triangle.
Bulges directly through parietal peritoneum medial to the inferior epigastric vessels.
Usually occurs in older men due to an acquired weakness in the transversalis fascia.
Femoral hernia
Protrudes below inguinal ligament through femoral canal below and lateral to pubic tubercle.
More common in females, but overall inguinal hernias are the most common. *more likely to present with incarceration or strangulation
Inguinal (Hesselbach) triangle:
Inferior epigastric vessels
Lateral border of rectus abdominis
Inguinal ligament
