Lect. 4: GI System Flashcards
1
Q
What is the blood supply to the foregut?
A
celiac trunk
2
Q
What is the blood supply to the midgut?
A
superior mesenteric artery
3
Q
What is the blood supply to the hindgut?
A
inferior mesenteric artery
4
Q
What provides parasympathetic innervation to the foregut?
A
vagus nerve
5
Q
What provides parasympathetic innervation to the midgut?
A
vagus nerve
6
Q
What provides parasympathetic innervation to the hindgut?
A
pelvic splanchnic nerves (S2-S4)
7
Q
What provides sympathetic innervation to the foregut?
A
Preganglionics: greater thoracic splanchnic (T5-T9)
Postganglionics: celiac and superior mesenteric ganglia
8
Q
What provides sympathetic innervation to the midgut?
A
Preganglionics: lesser thoracic splanchnic (T10-11)
Postganglionics: celiac and superior mesenteric ganglia
9
Q
What provides sympathetic innervation to the hindgut?
A
Preganglionics: lumbar splanchnics (L1-L2)
Postganglionics: inferior mesenteric ganglia
10
Q
What are the adult derivatives of the foregut (primitive gut tube)?
A
1) pharynx
2) esophagus
3) stomach
4) 1st and 2nd parts of duodenum
5) liver
6) pancreas
7) biliary apparatus
8) gallbladder
11
Q
What are the adult derivatives of the midgut (primitive gut tube)?
A
1) 2nd, 3rd, and 4th part of duodenum
2) jejunum
3) ileum
4) cecum
5) appendix
6) ascending colon
7) transverse colon (proximal 2/3)
12
Q
What are the adult derivatives of the hindgut (primitive gut tube)?
A
1) transverse colon (distal 1/3) to splenic flexure
2) descending colon
3) sigmoid colon
4) rectum
5) anal canal (above pectinate line)
13
Q
The primitive gut tube is made of what primary germ layer?
A
endoderm (inner wall of gut tube)
14
Q
What marks the transition between the foregut and midgut?
A
ampulla of Vater
15
Q
What marks the transition between the midgut and the hindgut?
A
splenic flexure
16
Q
Where do the lateral body folds fuse?
A
ventral midline (at linea alba)
17
Q
Is the amniotic cavity dorsal or ventral on the week 4 embryo?
A
dorsal
18
Q
Is the yolk sac dorsal or ventral on the week 4 embryo?
A
ventral
19
Q
What is pulled into the body of the embryo to form the gut tube? What lines this?
A
part of the endoderm-lined yolk sac is pulled into the body of the embryo forming the gut tube
20
Q
What is the name of the closed captured space that surrounds the gut tube?
A
coelom (forerunner of cavities)
21
Q
What are the future divisions of the coelum?
A
1) pleural cavity
2) pericardial cavity
3) peritoneal cavity
22
Q
What is the consequence of head to tail body folding in the development of the gut tube?
A
folding at the head and tail makes posterior recess and anterior recess that divide the gut tube into its 3 parts: foregut, midgut, and hindgut
23
Q
What maintains a connection between the yolk sac and midgut?
A
vitelline duct
24
Q
How long does the connection exist between the yolk sac and the midgut?
A
around the 9th-10th week, the vitelline duct closes and the gut sac gets excluded from the embryo
25
Describe the rotation of the foregut.
Rotates 90 degrees to the right (clockwise) along the longitudinal axis
26
Describe the characteristics of the midgut.
midgut is represented by gut loop (very simple structure that will grow over 20 feet)
27
Describe the rotation of the midgut.
Rotates 270 degrees to the left (counterclockwise)
28
What is the important landmark of the colon (dilated sac in hindgut)?
cloaca
29
Where does the vitelline duct extend?
patent diverticulum that connects midgut loop to umbilical ring/stalk
30
Describe the herniation of the midgut.
there is not enough room in the abdominal cavity for both the foregut and midgut, so the midgut is forced to move out of abdominal space into the connecting stalk for around 4 weeks (and 90 degrees of the 270 degree rotation occurs at this time)
31
When does the midgut retract back in?
at 10th week, abdominal space is large enough for the midgut to retract back in (and the rest of the rotation (180 degrees) occurs at this time)
32
Does hindgut rotate?
NO, it septates
33
What is the outermost, continuous, single layer of peritoneum around the body wall/periperty called?
parietal peritoneum
34
What is found somewhere in the course of the parietal peritoneum?
a reflection off the dorsal body wall and formation of visceral peritoneum
35
Other than location, what is different about parietal and visceral peritoneum?
visceral refections are 2-4 layers, parietal peritoneum is only 1 layer
36
What is significant about the multiple layers of visceral reflections?
double layered extension is conduit for arteries/nerves/veins/lymphatic extensions to come off the dorsal body wall and come into contact with viscera
37
Does the parietal peritoneum change names?
NO
38
Does the visceral peritoneum change names?
yes, named by location (ex. omenta, mesocolon, etc.)
39
What is the visceral peritoneum of the stomach?
omenta
40
What is the visceral peritoneum of the colon?
mesocolon
41
Do adults have a large coelom?
NO, peritoneal cavity (coelom) is not very developed in humans, in development in coelom is filled with organs and viscera, the parietal and visceral layers will become opposed (very close together)
42
What does retroperitoneal mean?
between parietal and inner layers of body wall (transversalis fascia, etc.) (external to parietal peritoneal)
43
What is similar about the duodenum and pancreas?
4 parts each, and 1 part is intra, other parts are retro
duodenum (1st part)
pancreas (tail)
44
From what primary germ layer does the spleen develop?
mesoderm* different, only foregut derivative that is from mesoderm and not endoderm
45
Name the retroperitoneal organs.
```
Suprarenal glands
Aorta and IVC
Duodenum (2nd, 3rd,4th parts)
Pancreas (head, neck and body)
Ureters
Colon (ascending and descending)
Kidneys
Esophagus
Rectum
```
46
After body foldings, the foregut is suspended by what?
dorsal AND ventral embryonic mesentery** remember this
47
Mesentery wise, how are the foregut and midgut/hindgut different?
the midgut and hindgut only have a dorsal embryonic mesentery (ventral dissipates)
48
What structures develop within the ventral mesentery?
liver and biliary system
49
Describe the development of the liver.
liver buds off of the endoderm of the foregut and pushed down into ventral embryonic mesentery
50
What adult structure (derived from ventral embryonic mesentery) attaches the liver to the anterior body wall?
falciform ligament
51
What adult structure (derived from ventral embryonic mesentery) attaches the liver to the stomach?
Lesser omentum
52
What 2 ligaments are a part of the lesser omentum?
1) hepatoduodenal
| 2) hepatogastric
53
Why is the hepatoduodenal ligament significant?
transports the portal triad
54
Describe the development of the spleen.
develops from mesoderm and within the dorsal embryonic mesentery
55
What two adult structures are developed from dorsal embryonic mesoderm?
1) splenorenal ligament
| 2) gastrosplenic ligament
56
What organ also moves into the dorsal embryonic mesoderm?
pancreas
57
After the foregut rotates 90 degrees to the right, what occurs?
the liver moves to the right (with ventral mesentery) and the spleen and pancreas move to the left (with dorsal mesentery)
58
Rotation of foregut splits the peritoneal cavity into what 2 parts?
lesser (omental bursa) and greater sacs
59
What is the opening of the omental bursa?
epiploic foramen
60
What is the greater omentum derived from?
dorsal embryonic mesentery (outpocketing of gastrocolic ligament)
61
What are the boundaries of the omental bursa?
* Ant: lesser omentum, posterior surface of stomach, gastrocolic ligament
* Inf: transverse colon and transverse mesocolon
* Sup: left lobe of liver
* Post: parietal peritoneum over pancreas and left kidney
62
What 3 visceral systems are developed as buds of foregut endoderm?
1) lung and lower respiratory tract
2) liver and biliary tract
3) pancreas
63
From what part of the foregut endoderm is the lung and lower respiratory tract derived?
upper esophageal lining endoderm
64
From what part of the foregut endoderm is the liver/pancreas derived?
endoderm lining of the first part of the duodenum
65
What is the lower respiratory system originally (at 4th week)?
single anterior endodermal bud that divides into single respiratory diverticulum
66
What separates the foregut from the trachea?
tracheoesophageal septum
67
How does the respiratory tree develop from the single respiratory diverticulum?
goes around 12 divisions to deelop an elaborate respiratory tree (from trachea to respiratory bronchioles)
68
On the timeline of lung development, what weeks are critical for survival?
minimally 25-28th week (before the 25th week, infant cannot survive)
69
Why can infants not survive if born before the 25th week of gestation?
you need enough development of type 2 pneumocytes (needed for sufactant produciton)
70
What is the most common of all respiratory newborn defects?
Tracheoesophageal (TE) fistula
71
What is a TE fistula?
TE septum does not properly develop-- upper esophagus ends in a blind sac, lower end of the esophagus hooks into the trachea (slightly above slit)
72
What are the signs of a TE fistula?
1) esophageal atresia
2) polyhydramnios (increased volume of amniotic fluid)
3) regurgitation of milk with gagging/cyanosis after feeding
4) abdominal distention after crying
5) Reflex of gastric contents into lungs causing pneumonitis
73
Why does polyhydramnios occur with TE fistula?
because cannot circulate via ingestion, so it builds up in amniotic cavity
74
When does the pancreas develop?
pancreas develops in 5th and 6th weeks
75
What does the pancreas develop from?
from endodermal buds (2 of them, ventral and dorsal sides of the gut tube) ventral bud rotates posteriorly behind the duodenum to insert underneath the dorsal bud and fuses (ducts fuse too)
76
What portions of the pancreas come from the ventral bud?
head and uncunate process
77
What portions of the pancreas come from the dorsal bud?
neck, body and tail
78
What is annular pancreas?
ventral bud splits and forms a ring around the duodenum instead of rotating cleanly around. This causes a duodenal constriction.
79
What is a symptom of annular pancreas?
polyhydramnios (build-up of amniotic fluid)
80
Name the 2 connections between the GI tract and the umbilicus. What exactly do these connect?
1) viteline duct: connects midgut with umbilicus
| 2) allantois: connects cloaca (future bladder) with umbilicus
81
What are the fibrous remains of the allantois called?
urachus (median umbilical ligament)
82
When should the viteline duct close?
8th-10th week
83
When should the allantois close?
around 9th-12th week (a week or 2 after the viteline duct closure)
84
What happens if the viteline duct stays patent at birth?
vitelline fistula: leakage of digestive material (meconium)out of umbilical stump
85
What happens if the allantois stays patent at birth?
uracheal fistula: leakage of urine out of umbilical stump
86
What types of mucosa do Meckel's Diverticulum contain?
gastric and pancreatic mucosa
87
What is Meckel's diverticulum?
a 2 inch long remnant part of the vitelline duct that is around 2 feet from the ileocecal junction that occurs in 2% of the population (and is most common GI defect)
88
What is interesting about a vesicouracheal diverticulum?
it is a continuation of the allantois into adulthood that usually closes down, but does not close down tightly, it can push open later in life with increased pressure in the bladder due to prostate problems
89
When does the 270 degree rotation of the midgut occur?
6th -10th week
90
The midgut starts out as a simple loop around what artery?
superior mesenteric artery
91
What are the two portions of the simple midgut loop?
1) cephalic limb
| 2) caudal limb
92
What does the cephalic portion of the midgut loop form?
distal duodenum
jejunum
proximal ileum
93
What does the caudal portion of the midgut loop form?
distal ileum
cecum
ascending colon
proximal 2/3 of the transverse colon
94
Which portion of the loop has the most growth?
cephalic portion of the loop
95
Describe the 4 steps of the midgut retraction.
1) jejunum returns first and lies to the left side of the abdomen
2) ileum follows and lies to right of abdomen
3) cecum enters last and passer to upper right quadrant and movement of cecum pulls transverse colon across upper abdomen
4) sinks to lower right quadrant, forming descending colon
96
What is hypertrophic pyloric stenosis? What part of the gut does this effect?
narrow pyloric lumen (foregut) that does not allow proper drainage from stomach to duodenum
97
What is associated with hypertrophic pyloric stenosis?
polyhydramnios
98
What is the presentation of a patient with hypertrophic pyloric stenosis?
child that will take a normal feeding then experience PROJECTILE, NONbilous (clear) vomiting
99
What is duodenal atresia? What part of the gut does this effect?
lumen of duodenum (midgut) fails to recanalize (constriction of duodenum)
100
What is associated with duodenal atresia?
polyhydramnios
101
What is the presentation of a patient with duodenal atresia?
distended stomach and bile-containing (streaks) vomit (because distal to bile duct)
102
What is omphalocele?
defect of herniation, midgut gets captured in umbilical stalk and won't come back in at 10th week. Occurs at the umbilical ring and the gut is covered by a sac of amnion
103
What is gastroschisis?
defect in body folding (typically weakness in right fold), occurs to the side of the umbilical ring and is NOT covered by sac of amnion
104
Why does omphalocele have such a high mortality rate?
because it is associated with other respiratory, CV, etc. problems
105
What is volvulus?
twisting of the intestine causing an obstruction
106
What is malrotation of the midgut?
when the normal 270 degree rotation is not complete and the cecum/appendix lie in the upper abdomen (commonly associated with volvulus)
107
What must occur in the hindgut during development?
urorectal septum, mass of mesoderm from caudal end of dorsal body wall grows from dorsal to ventral and divides original cloaca space into ventral and dorsal side
108
What is developed on the dorsal side of the urorectal septum?
anorectal canal (until pectinate line)
109
What is developed on the ventral side of the urorectal septum?
urogenital sinus (with urinary bladder, lower vagina and urethra in females, and prostate gland and all of male urethra except penile urethra)
110
What is the "plug" of the anorectal canal that breaks down at the pectinate line in development?
anal membrane
111
What is an imperforate anus?
most common defect of hindgut due to failure of the anal membrane to properly break down (misdirected urorectal septum going slightly dorsal), so no complete opening at anal membrane
112
What primary germ layer does the anal canal BELOW the pectinate line come from?
ectoderm
113
What is colonic aganglionosis?
Hirschsprung Disease
114
What happens in Hirschsprung Disease?
failure of neural crest cells to form the myenteric plexus--usually in the hindgut (so it does not have parasympathetic innervation to pelvic splanchnics)
115
What are the symptoms of Hirschsprung Disease?
loss of peristalsis, fecal (merconium) retention, and abdominal distention of the gut proximal to the usual lesion site (at transverse colon)
116
What is anal agenesis?
lack of anal opening as a result of improper formation of the urorectal septum (may cause rectovesical, rectovaginal, or rectourethral fistula)
