GI Flashcards
The foregut contains? (7)
Esophagus, Fundus, Body, Antrum of the stomach, pylorus, duodenal bulb, proximal descending duodenum
The Midgut contains?
Distal descending duodenum, transverse duodenum, ascending duodenum, jejunum, ileum, cecum, Ascending and proximal transverse colon
The Hindgut contains?
Distal transverse colon, Descending colon, sigmoid colon, and rectum.
Explain the embryological rotation and fixation of the foregut, midgut, and hindgut
The foregut rotates clockwise, the midgut rotates counterclockwise. Then the bowel is fixerd into position, either intra or retroperiotoneal.
Normally the stomach and duodenal bulb are intraperiotneal/extraperiotneal? And the Descending and transverse duodenum are retroperitoneal/intraperitoneal?
Stomach and duodenal bulb are normally intraperitoneal
Descending and transverse duodenum are retroperitoneal.
The Jejunum and ileum are intra/extraperitoneal?
Intraperitoneal.
Describe the normal positioning of the cecum and large intestines
The cecum can be intra or retroperitoneal. The ascending colon is retroperitoneal and the transverse colon is intraperitoneal. The descending colon is retroperitoneal, the sigmoid colon is intraperitoneal and the rectum is extraperitoneal.
Together the ascending colon, descending, and rectum are extra or retroperitoneal
The transverse and sigmoid colon are intraperitoneal.
The cecum can be extra or intra
If ligament of treitz is not present what could this mean?
There was a malrotation in the formation of the intestines. All small bowel ends up on the right side of the abdomen instead of where they are supposed to be.
Intestinal malrotation with midgut volvulus presents with?
Presents with billius vomiting. Obstruction is distal to where the bile duct enters the duodenum.
Complex folding during development results in what?
Creates the peritoneal cavity and the subcomponents of the lesser sac (omental bursa) and the greater sac)
The greater omentum is created from the greater curve of the stomach
The Vitelline duct has what clinical significance?
This is a remnant of the yolk stalk that is in the area of the umbilicus and attached to the small bowel (in 2% of population). It can persist as Meckel’s diverticulum and become inflammed, hemorrhage, intusscept, obstruct or ulcerate
Groin is a weak area in the anterior abdominal wall secondary to?
Secondary to the descent of the gubernaculum - inguinal hernias.
Inguinal hearnias result from?
Weakness in the abdominal wall secondary to the gubernaculum and the descent of the testes and the round ligament.
What does the solar plexus contain?
There are extensive nerve plexes that supply the abdomen. - Solar plexus contains
Celiac ganglia and plexus
Prevertebral plexus
Superior and inferior hypogastric PP
The abdominal viscera have extrinsic and intrinsic components of the nervous system.
Function of the extrinsic system in the gut?
Involves sensory and motor nerves that communicate with the CNS - visceral afferent and visceral efferent (SNS and PSNS) fibers
PSNS innervation to the abdominal GIT via vagus nerve (foregut and midgut) and the Pelvic splanchnic nerve (hindgut)
SNS innervation via the splanchnic nerve.
Function of the intrinsic system of the gut?
Involves regulation of the digestive tract by a generally self sufficient network of sensory and motor neurons.
These work with coordinated contraction and relaxation of intestinal smooth muscle (peristalsis) and regulation of gastric secretion and blood flow.
Local neuronal circuit in wall of GI - myenteric and submucosal plexes
Generally independent but can be modified by SNS and PSNS.
Splanchnic nerve function?
Sympathetic fibers to the thoracic, lumbar, and sacral splanchnic nerves to prevertebral plexus.
Parasympathetic fibers to the pelvic and sacral splanchnic nerves from inferior hypogastric plexus (pelvic plexus)
The Preverteral plexus recieves?
PSNS fibers from visceral afferents from Vagus N
SNS and visceral afferents from the thoracic and lumbar splanchnic nerve
PSNS fibers from pelvis splanchnic nerves to the inferior hypogastric plexus.
The celiac artery supplies
Supplies the foregut in the abdomen - esophagus, to proximal duodenum inferior to major duodenal papilla.
The superior mesenteric artery supplies?
The midgut (lower L1) duodenum distal to the major papilla to the proximal 2/3 of the transverse colon
All venous drainage from the GI tract passes through?
Passes through the liver. Note, there are anastomoses with the systemic venous circulation - this is where the collaterals form when there is portal hypertension
The inferior mesenteric artery supplies?
The supplies the hindgut, the distal 1/3 of the transverse colon to the superior part of the rectum.
In General FYI
there are extensive anastomoses between the branches of the celiac artery and the superior mesenteric artery around the stomach, pancreas, and duodenum
There are extensive anastomoses between the arterial branches of the small and large bowel supplied by the superior mesenteric artery
There are anastomoses between the arterial branches of the large bowel (right, middle, and left colic arteries) via the marginal artery (arcade) of drummond
There can be an area of vulnerability at the level of the branches to the splenic flexure of the colon (jucntion of the SMA and IMA) where the anastomosses can be limited
Mesenteric ischemia can occur is there is ischemia to the bowel, generally several major branhces of circulation need to be compromised
There are anastomoses between branches of the IMA and the systemic circulation, branches of the internal iliac artery, and the internal pudendal artery.
Portocaval anastomoses?
Caput medusa -umbilical vein to the anterior abdominal wall
Distal esophagus - Esophageal varices
Inferior rectum - enlarged hemorrhoidal veins
Retroperiotneal areas of the large and small intestines
Posterior aspect of the pancreas.
Physical exam marks
L1
L3
L4
Left posteriorly ribs 9-11
Midline
From anterior ililac spine to pubic tubercle
Superolateral to the pubic tubercle
Midway between the anterior iliac spine and the pubic symphysis.
L1 - transpyloric plane
L3 subcostal plane - inferior mesenteric artery
L4 supracristal plane - between the superior iliac crests, bifurcation of the aorta
Spleen is left posteriorly ribs 9 to 11
Liver crosses midline
Inguinal ligament goes from the anterior iliac spine to the pubic tubercle
The inguinal canal and superficial inguinal ring are superolateral to the pubic tubercle
Deep inguinal ring is midway between anterior iliac spine and the pubic symphysis. Just below this and the inguinal ligmanet is the femoral pulse.b
What is the Transpyloric plane?
Landmark
Midway between the jugualr notch and the pubic symphysisi
Midway between the lower body of the sternum and umbillicus
At the level of L1
Beginning of jejunum just distal to plane
Crosses body of the pancreas
approximates the renal hila
Approximates the origin of SMA
Describe Visceral pain
Visceral - cramping, burning, or gnawing pain
Noxiuos stimuli trigger nociceptors in viscera
Pain dull and poorly localized in midline because both sides of the spinal cord are stimulated by afferent impulses. Pain accompanied by sweating, nausea, pallor, and restlessness
Pain roughly corresponds to dermatomes innervating organ with problem
Injuries to visceral tissues may also exhibit referred pain
Describe Somatoparietal pain
Noxious stimuli of parietal peritoneum
More intense and more precisely located than visceral pain
Ex: Mc burneys point in appendicitis in somatoparietal area
Aggravated by moving or coughing
Mediating nerve impulses travel with somatosensory spinal nerves, not Autonomic NS, corresponding to dermatomes.
Lateralizes because only one side of the parietal peritoneum is innervated by somatosenosry fibers at a given location.
Describe referred pain
Referred pain occurs when visceral afferents and somatic afferents from a different anatomic region converge on a second order neuron in the spinal cord at the same spinal segment.
Usually well localized
ex: Diaphragmatic irriation from subphrenic abscess is interpreted as coming from the shoulder.
Appendiciits pain
Visceral afferents carry pain sensations that enter the spinal cord with sympathetic fibers at the T 10 level. The pain is referred to the dermatome of T 10 the umbilical region.
The pain can sometimes begin as a central periumbilical colicky type of pain that comes and goes
AFter 6-10 hours, the pain tends to localize to the RLQ and becomes constant. (McBurneys point pain that is somatoparietal)
Chest films can be valuable in evalulating abdominal pain how?
Lung or pleural disease can manifest as abdominal pain
Free air beneath the diaphragm secondary to perforated abdominal viscus (pneumoperitoneum) will gravitate under the diaphgragm in an upright flim
Where can free intra-abdominal air be?
Can be either within the peritoneum (intraperitoneal) or extra-peritoneal (often retroperitoneal)
The 3 common imaging techniques for Female/male pelvis
Ultrasound - particularly useful for imaging the ovaries, uterus. Also may be used to image the prostate
MRI - particularly useful for imaging the Uterus and cervix, and prostate
CT - images uterus, broad and round ligament, ovaries, seminal vesciles and prostate, but not as well as MRI
Where is Morrison’s pouch?
Posterior hepato-renal space (right side)
Free air can locate here secondary to perforated viscus
The Oral prep phase of swallowing is processed by which 2 nerves. (Mastication and salivation)
Cranial nerve V3 for mastication, CN VII for salivation
The oral buccal phase is mediated by what cranial nerves? Bolus moved to back of tongue, anterior tongue lifts hard palate and retracts posterioly to force bolus into oropharynx. Posterior tongue is lifted by mylohyoid m, elevating soft palate and sealing the nasopharynx.
Cranial nerves V, VII, XII
The Pharyngeal phase is initiated by what cranial nerves? Bolus advanced from pharynx to esophagus. Soft palate is elevated to posterior nasopharyngeal wall by levator veli palatini. Superior constrictors bring palatopharyngeal folds together. Larynx and Hyoid are elevated and pulled forward to the Epiglottis to relax Cricopharyngeus m
Cranial nerves V X XI XII
Last phase of swallowing?
Esophageal phase
Trigeminal nerve - CN V function
Important in chewing and sensation (pain, temp, touch) to the outh and anterior 2/3 of the tongue, PSNS to the salivary glands in the mouth and Parotid gland via CN VII
CN VII facial nerve function
Taste on anterior 2/3 of the tongue via the chorda tympani. Also muscles of facial expression
Glassopharyngeal nerve CN IX function
Taste and sensation on posterior 1/3 of the tongue, sensation in the oropharynx and upper pharynx
CN X vagus nerve function
Sensation from mucous membranes of pharynx, larynx, esophagus, and abdominal viscera of foregut and midgut
Taste from epiglottis
Motor of soft palate, pharynx, and larynx and smooth muscle of abdominal viscera
Important for airway protection
CN XI Accessory nerve function
Assists in the swallowing function (traps and sterno as well)
Hypoglossal nerve CN XII function
The hypoglossal nerve innervates all the intrinsic muscles and all but one of the extrinsic muscles (genioglossus, styloglossus, and hyoglossus) of the tongue
Palatoglossus - CN X
What is a functional, but not anatomical, section of the esophagus wall that acts as a sphincter?
Proximal esophageal sphincter
Is the proximal esophageal sphincter skeletal muscle? Is it under conscious control? What triggers it?
The proximal esophageal sphincter is a functional, but not anatomical section of the esophageal wall that acts as a sphincter.
It is skeletal muscle but not under conscious control
Triggered by the swallow reflex
What are the muscles of the proximal esophageal sphincter?
Cricopharyngeus muscle portion of the inferior pharyngeal constrictor
Commonly becomes dysfunctional with aging
Circulation of the liver
Blood from the GIT flows via the Hepatic portal vein to the sinusoids which are in contact with the liver cells (hepatocytes) then to the hepatic vein to the inferior vena cava.
the porta hepatis contains?
The common hepatic bile duct
Hepatic artery proper
Hepatic portal vein
Note the celiac artery supplies the common hepatic artery to the hepatic artery proper to the right and left hepatic aa.
What is the portal triad?
Portal triad within hepatic lobules contains
Arteriolar branch of the hepatic artery
Venule branches of the portal vein
Biliary ductules
Acalculous Cholecystitis and necrotizing cholecystis
Usually seen in patients with other coexistant disease processes
Seen with triad of systemic mediators of inflammatory processes and trauma, biliary stasis, and local or generalized trauma
Usually a fulminant course with high rate of complications such as gangrene and perforation
Chest films can be valuable in evaluating abdominal pain how?
Lung or pleural disease can manifest as abdominal pain
Free air beneath the diagphragm secondary to perforated abdominal viscus (pneumoperitoneum) will graviate under the diaphragm in an upright film
SAD PUCKER - Tells you what is retroperiotoneal)
Suprarenal (adrenal) Glands
A - aorta/IVC
D - Duodenum 2nd and 3rd segments
P - pancreas (except the tail) (Tail is not retroperitoneal)
U - Ureters
C - Colon (descending and ascending) Transverse and sigmoid are not retro.
K - Kidneys
E - esophagus (lower 2/3rds)
R - Rectum (partially)
Diseases of the esophagus can be diagnosed by?
Upper Gi series (barium study or CT)
Pancreatic duct and common bile duct join at?
The ampulla of Vater is a small opening that enters into the first portion of the small intestine, known as the duodenum. The ampulla of Vater is the spot where the pancreatic and bile ducts release their secretions into the intestines.
Small bowel obstructions can be caused by?
When the patient has had prior surgery - think adhesions
No prior surgery - think malignant obstruction
