Anatomy GIT overview-Witwer (Exam 2) Flashcards
Foregut= (contains)
Esophagus; Fundus,
Body, and Antrum of Stomach, Pylorus,
Duodenal bulb and Proximal Descending
Duodenum.
Midgut=
Distal Descending Duodenum,
Transverse Duodenum, and Ascending
Duodenum, Jejunum, Ileum, Cecum,
Ascending and Proximal Transverse Colon
Hindgut=
Distal Transverse Colon,
Descending Colon, Sigmoid Colon,
And Rectum
Embryological Rotation and Fixation of the Foregut, Midgut, and Hindgut
- the foregut rotates _____
- the midgut rotates _______
- clockwise (stomach)
- midgut–> counterclockwise
Embryological Rotation and Fixation of the Foregut, Midgut, and Hindgut:
-Then the bowel is fixed into position, either ____ or _______
intra or retroperitoneal.
Normally, the Stomach and Duodenal bulb are ________, the Descending and Transverse Duodenum are _______
intraperitoneal
retroperitoneal.
The Jejunum and Ileum are _________
Intraperitoneal.
the cecum is intra or retroperitoneal?
The Cecum can be either intra or retroperitoneal
Ascending and descending colon are ______
retroperitoneal
transverse colon and sigmoid colon are _______
intraperitoneal
Rectum is _______
extraperitoneal
Describe the Normal Rotation of the midgut (slide where Witwer wrote out the steps)
- Midgut loop has a cranial limb and a caudal limb
- Midgut loop rotates around the axis of the **superior mesenteric artery
- Midgut loop rotates first 90 degrees to bring the cranial limb to the right & caudal limb to the left during the physiological hernia
- the cranial limb of the midgut loop elongates to form the intestinal coiled loops (jejunum and ileum).
- This rotation is counterclockwise and it is completed to 270 degrees, so after reduction of physiological hernia it rotates to about 180 degrees
Where is the ligament of treitz located?
**LUQ
-if the ligamentum of treitz IS NOT there, you know you had a malrotation. This causes the small bowel to be on the right (when it should be on the left) and you have a thing called Ladd’s band. It pinches the arteries and veins and you get increased edema and blockage of the vessels. You end up with arterial infarction and DEAD bowel. Tx: they go in and cut the Ladd’s band, and reattach the bowel to where it SHOULD be
Intestinal Malrotation with Midgut Volvulus:
-Clinical Sx?
- **billious vomiting
- Hemodynamic instability
- Abdominal distension
(Pts present with: bilius vomiting!!! because the bile duct from the liver comes in and inserts on the lesser curve side of the duodenum. Bile gets in their (its an emulsifier) and it breaks down the fat cells –any time you see bilius vomiting: you know the obstruction is distal to where the common bile duct enters the duodenum )
Intestinal Malrotation with Midgut Volvulus:
Associated congenital defects?
- congenital diaphragmatic hernia
- Congenital heart disease (heterotaxy syndrome)
- Omphalocele
Intestinal Malrotation with Midgut Volvulus:
-management/tx?
*surgical (Ladd procedure)
2 times when you get a malrotation of the midgut Volvulus:
- when you’re a year old or 2 OR after 50 yo
- *high risk for associated congenital defects
- Tx: management= surgical (Ladd Procedure)
Creation of the Peritoneal Cavities and Mesenteries
The complex folding and changes described above during development create the peritoneal cavity and its subcomponents–> the Lesser Sac (Omental Bursa) and the Greater Sac
The Greater Omentum is created from?
the greater curve of the stomach
The Vitelline duct:
- is a remnant of?
- present in __% of the population
- the yolk stalk that is in the area of the umbilicus and attached to the small bowel
- 2%
The Vitelline duct can persist as a _____
*Meckel’s Diverticulum–> and become inflammed, hemorrhage, intussuscept, obstruct or ulcerate
(Normally the vitelline duct disappears in ppl–> if it remains it persists as meckel’s diverticulum)
*Meckel’s diverticulum: KNOW. These PPl have gastric fluid in there and they can present with GI bleeding.
Normally the mesenteric root goes from the left upper abdomen to the _____
right lower abdomen
Note Gastrosplenic and
Splenorenal ligaments and
the Porta Hepatis
?
Is the entire liver covered by peritoneum?
There is a bare area of the liver= that’s NOT covered with peritoneum
Glisson’s capsule=
has lot’s of pain fibers, so when it’s stretched its painful
–Behind the liver is the lesser omentum and the omental bursa
-bigest no no in surgery– you never transect the ____
common bile duct cuz it DOES not heal
Lesser omentum= attachment b/w the stomach and the ____
liver
pouch of douglas=
retrouterin pouch or vesicoretro pouch (in males)
–pus and cancer ends up in those pouches
Right posterior retroperitoneal space=
Morrison’s pouch!!!! KNOW!
=subhepatic posterior recess- behind liver, most dependent space- where ascites/tumors will go. It’s Intraperitoneal
Groin is a weak area in the anterior abdominal wall secondary to the descent of the ________
gubernaculum
—>inguinal hernias
(Gubernaculum= “governs the descent of the testicle” . Hernias can occur in this area)
Hernias can also occur in which areas?
- umbilical
- femoral
- para-umbilical
- incisional
- spigelian
- internal (obturator, greater sciatic, and piriformis) areas
–MC hernias are inguinal hernias**
Muscles of anterior abdominal wall are innervated generally in patterns reflected by:
the dermatomes
How do inguinal hernias form?
There is a weakness in the anterior abdominal wall secondary to the gubernaculum and descent of the Testes and Round Ligament
notes: (There are direct inguinal hernias and indirect
-guys are more prone to getting hernias
-note the superficial inguinal ring: spermatic cord comes through it
-external oblique muscle orientation= “putting something in your pocket”
-transverse abdominus= deepest muscle
-linea alba= “white line in the middle of the 6 pack”
-we uncover the inguinal canal
-inguinal ligament goes form the in anterior interior iliac crest to the
-internal oblique, there is the inguinal ligament and deep to that is the external canal with the spermatic cord
NEED TO KNOW THIS ANATOMY
Indirect Inguinal Hernia=
indirect hernia: comes from the deep inguinal ring and down the inguinal canal and out the superficial inguinal ring (ductus deferens=
Direct Inguinal Hernia=
goes straight out and there’s weakness In the inguinal triangle (or hasselbach’s triangle!!!
Hasselbach’s triangle=
- hasselbach’s traiangle= lateral border of the rectus abdominus, inferior epigastric vessels and iliopubic tract, located superior to the inguinal ligament.
- where 2 types of hernias MC form (indirect and direct hernias)
Abdominal Innervation:
-Which nerves innervate the abdomen?
Extensive nerve plexes supply abdomen – Solar Plexus
Solar plexus=
Celiac Ganglia and Plexus, Prevertebral Plexus, Superior and Inferior Hypogastric PP(plexi)
The abdominal viscera have _____ and ______ Components of the Nervous System
extrinsic and intrinsic
Describe the Extrinsic system of the abdominal viscera (nervous system)
-The Extrinsic System involves sensory and motor nerves that communicate with the CNS – via Visceral Afferent and Visceral Efferent (SNS and PSNS) Fibers
—PSNS innervation to the abdominal GIT is via Vagus N (fore and midgut) and Pelvic
Splanchnic NN (hindgut)
—SNS innervation via the Splanchnic nerves
Craniosacral aka ______
parasympathetic
What is a major nerve that innervates the diaphragm?
vagus nerve
Describe the Intrinsic system of the abdominal viscera (nervous system)
The Intrinsic System (Enteric Nervous System) involves regulation of the digestive tract by a generally self-sufficient network of sensory and motor neurons – coordinated contraction and relaxation of intestinal smooth muscle (peristalsis) and regulation of gastric secretion and blood flow.
- –A local neuronal circuit in wall of GIT – **myenteric and submucosal plexes
- –Generally independent but can be modified by SNS and PNS
Splanchnic nerves are _____ fibers to the…
(BOTH)
-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 Plexes (Pelvic Plexus)
Prevertebral Plexus receives:
(3 things)
-PNS fibers and visceral afferents from Vagus N
-SNS and visceral afferents from the
thoracic and lumbar splanchnic nn
-PNS fibers from pelvic splanchnic nn
to the inferior hypogastric plexus
The Celiac Artery:
- What level is it at?
- Supplies the?
- (upper L1)
- supplies the foregut in abdomen –-> esophagus to proximal duodenum inferior to major duodenal papilla
Abdominal Vasculature:
-list 3 main arteries
- celiac artery
- Superior mesenteric a
- inferior mesenteric artery
Superior Mesenteric artery:
- What level is it at?
- Supplies the ?
- (lower L1)
- supplies the midgut –-> Duodenum distal to the major papilla to the proximal 2/3 of transverse colon
Inferior mesenteric artery:
- What level is it at?
- Supplies the ?
(L3) supplies the hindgut – distal 1/3 of transverse colon to the superior part of rectum
Celiac artery is at the level of L1 and so is the _____
conus medullaris
There are extensive anastomoses between branches of the Celiac Artery and the ____
Superior Mesenteric Artery around the Stomach, Pancreas and Duodenum.
There are extensive anastomoses between the arterial branches to the Small and Large Bowel supplied by the _______ _______ artery
superior mesenteric artery
There are anatomoses between the arterial branches to the large bowel (right, middle, and left colic arteries) via the ______
Marginal Artery (arcade) of Drummond.
notes: Arcade of drummond: major anastomoses: the bowel’s fx is to get lots of blood into the bowel for nutrition (signif. Increase in blood flow to bowel after eating) all those anastomoses help maintain high blood flow to the bowel
There can be an area of vulnerability at the level of the branches to _____ flexure of the colon
splenic
The splenic flexure of the colon is the junction of ____ & ____
superior mesenteric a
and inferior mesenteric a
At the splenic flexure of the colon, this is the area where anastomoses can be ______
limited (**an area of vulnerability)
Mesenteric ischemia (Mesenteric Angina) can occur if there is ischemia to the ____
- bowel
* *generally several major branches’ circulation will need to be compromised
There are anastomoses between branches of the inferior mesenteric artery and the _______ circulation, branches of the ______ and ________
systemic, Internal Iliac Artery, Internal Pudendal Artery
slide 23
d
ALL venous drainage from the GI tract passes through the ______
liver
Note anastomoses with the Systemic Venous Circulation – this is where _____
*the collaterals form when there is Portal Hypertension
systemic system and a portal system (the connections here are the =
Portacaval Anatomoses
-hepatic portal vein=
Porta hepatis
Caput Medusa–>
umbilical vein to the anterior abdominal wall
Distal esophagus–> ____ can form 2/2 portal HTN
esophageal varices (think cirrhosis Pts)
Inferior rectum: what can form here 2/2 HTN?
enlarged
hemorrhoidal veins
what part of the pancreas can be involved with portal HTN?
–Retroperitoneal areas of the large and small intestines
Posterior aspect of pancreas
Describe where the costal margin is located in relation to the pubic tubercle
Costal Margin (is above) and the pubic tubercle, anterior iliac spine, and iliac crest below
- abdominal viscera is located ABOVE the costal margins
- subcostal=L3
Transpyloric Line:
-is at which level?
-
**L1= Transpyloric Plane
Abdominal viscera are located _____ the costal margins
ABOVE
Subcostal Plane:
-what level?
L3 –– see below – Inferior Mesenteric a
Supracristal plane:
-what level?
L4 –>– between Superior Iliac Crests – bifurcation of the Aorta occurs here
–supracristal plane= when doing a lumbar tap (draw a line b/w the 2 of those at L4)
- Spleen – left posteriorly, ribs 9 to 11
- liver crosses midline*
Inguinal ligament goes from :
*anterior iliac spine to pubic tubercle
The inguinal canal and superficial inguinal ring (are located?)
superolateral to pubic tubercle)
Deep inguinal ring is midway between:
anterior iliac spine and pubic symphysis. Just below this and inguinal ligament is the femoral pulse.
If you can palpate the spleen this is ______
abnormal
*Transpyloric Plane
- Landmark
- Midway between jugular notch and pubic symphysis
- Midway between lower body of Sternum and umbilicus
- **Note relation to rib cage R9
**At L1
-Note beginning of Jejunum
Just distal to plane
- Crosses body of Pancreas
- Approximates renal hila
- Approximates origin of SMA
Describe the Organizational patterns of the Abdomen
=A Four Quadrant or a Nine Regional pattern
Subcostal plane at ____
L3
Intertubercular Plane at ___
L5 (iliac crests)
Epigastric region=
above the stomach
1 of the question
-what is the ddx of pain in each of the 4 quadrants!!! KNOW for exam (clin med and anatomy)
?
Abdominal Pain: 3 kinds of pain
Visceral, Somatoparietal, and Referred
Describe visceral abdominal pain
**Visceral= cramping, burning or gnawing pain
- Noxious stimuli trigger nociceptors in viscera
- Pain is dull and poorly localized in the 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 (see below)
Describe Somatoparietal Abdominal Pain
- _______ stimuli?
- more or less intense than visceral pain?
- Ex?
- *Noxious stimuli of parietal peritoneum
- *More intense and more precisely localized than Visceral Pain
- Example: McBurney’s point pain in appendicitis is somatoparietal
- Aggravated by moving or coughing
- *Mediating nerve impulses travel with Somatosensory spinal nerves, not Autonomic NS, corresponding to dermatomes
- SOMATOPARIETAL does not travel with ANS**
-*Lateralizes because only one side of parietal peritoneum is innervated by somatosensory fibers at a given location
(Know McBurney’s point pain= CLASSIC finding of ap[endicitis!!!! KNOW (it begins as a visceral pain and then localizes at mcburney’s point (1/2 way b/w umbilicas and
-jumping up and down is a stress test for appendicitis– send them to the hospital
)
Describe Referred Pain (of abdominal pain)
- Referred Pain (Pain remote from diseased organ):
- Referred Pain occurs when visceral afferents and somatic afferents from a different anatomic region converge on second order neurons in the spinal cord at the same spinal segment.
- **Usually well localized
- Example: Diaphragmatic irritation form subphrenic abscess is “interpreted” in the brain as “coming” from the shoulder
notes: (-classic one is heart disease, reflux, GERD, )
Visceral afferent= ____ order neuron
first
Spinal cord= ____ order neuron
second order neuron
Somatic afferent= ____ order neuron
first
Heart Referred pain–>
shoulder and arm
Stomach referred pain–>
Gallbladder — pain is referred to superior and lateral right shoulder, offset superior similar in size and circular shape to the superficial distribution of the axillary nerve.
Liver — pain is referred in a similar pattern to the heart, but only on the right hemi-body.
Stomach — pain is referred just to the right of midline in the epigastric area and to the mid-back, just below the referred angina from T7 to T9.
Ovaries — pain is referred to the skin area immediately over the ovaries anteriorly and directly posteriorly, but more lateral.
Appendix — pain is referred to Mcburney’s point in the right hypogastric area.
Kidneys — pain is referred to the skin area somewhat below the kidneys, posteriorly only, and medial to the posterior referred ovarian pain; there is also an area half way down the right lateral thigh, the right chest just to the right of the lower sternum.
Ureters — pain is referred to an anterior band across the pelvis, including the groin and the genitals, but not extending around to the back.
Colon pain–> suprapubic
Bladder — pain is referred to a continuous area encompassing the sacrum from S2 down to the upper medial thighs.
- Liver gallbladder trouble= RUQ
- classic referred pain= uretocalculus passing (starts up in liver and feel it go down and the pain goes down to the bladder, scrotum or labia)
- passing a kidney stone: followed it down
Appendicitis:
- describe the pain fibers?
- at what level?**
*Appendicitis – Visceral afferent fibers carry pain sensations that enter the spinal cord with sympathetic fibers at the T10 level (umbilicus)**. The pain is referred to the dermatome of T10, the umbilical region
-The pain in appendicitis 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 (McBurney’s point pain that is somatoparietal)
Abdominal Pain:
Some authors use the terms Visceral Pain and _______ pain in an overlapping way, ie “Visceral Referred Pain” (Netter) and “Referred pain from different visceral organs” (Guyton).
Referred Pain
-Referred Pain maps similar to the Visceral pain maps of Feldman are found in Netter, Guyton, and Gilroy Atlas of Anatomy.
