DEVELOPMENT DIGESTIVE Flashcards
1
Q
What are the divisions of a 4 week embryo’s abdominal cavity/GI tract?
A
Foregut
Midgut
Hindgut
2
Q
What attaches the midgut to the abdominal wall?
A
Oropharyngeal membrane
3
Q
What are the main branches of the abdominal aorta?
A
Celiac trunk
Superior mesentery artery
Inferior mesentery artery
4
Q
What are secondary retroperitoneal viscera?
A
Viscera that transition from intraperitoneal –> retroperitoneal
5
Q
What derives from the foregut?
A
Esophagus Stomach 1st & 2nd portions of duodenum Pancreas Liver Gallbladder Spleen (not derivative but categorised as it)
6
Q
What derives from the midgut?
A
Duodenum Ascending & superior 2/3 of transverse colons Ileum Appendix Jejunum
7
Q
What derives from the hindgut?
A
Superior rectum
Inferior 1/3 of transverse colon
Descending colon
Sigmoid colon
8
Q
What supplies the foregut derivatives?
A
Celiac trunk
9
Q
What supplies the midgut derivatives?
A
Superior mesenteric artery
10
Q
What supplies the hindgut derivatives?
A
Inferior mesentery artery
11
Q
What is the mesentery and what is its function?
A
Peritoneum fold that connects intraperitoneal viscera to abdominal wall
12
Q
What is the hepatic first effect?
A
Orally administered drugs will be metabolised in the liver and may change their composition
Slower effect than rectal drugs
13
Q
What parasympathetically innervates the foregut, midgut and hindgut?
A
Foregut - vagus nerve
Midgut - vagus nerve
Hindgut - pelvic splachnic nerves (S2-S4)
14
Q
What sympathetically innervates the foregut & midgut?
A
Thoracic splanchnic nerves (T5-T12)
15
Q
Where do the nerves that sympathetically innervate the foregut & midgut synapse at?
A
Level of main arches of abdominal aorta
16
Q
What sympathetically innervates the hindgut?
A
Lumbar splanchnic nerves (L1-L2)
17
Q
Where do the nerves that sympathetically innervate the hindgut synapse at?
A
Inferior mesenteric artery
18
Q
What is the crura?
A
Tendinous bands that attach posteriorly the diaphragm to lumbar vertebrae
19
Q
What is the crura composed of?
A
Right crus
Left crus
20
Q
What are the parietal branches of the abdominal aorta?
A
Inferior phrenics
Lumbars
Common iliac
Median sacral
21
Q
What are the visceral branches of the abdominal aorta?
A
Celiac trunk (T12) Superior mesenteric (L1) Inferior mesenteric (L3) Renal arteries (L1) Gonadal arteries (L2)
22
Q
What are the abdominal branches (direct tributaries) of the IVC?
A
Right inferior phrenic vein Right suprarenal Renal Right testicular (gonadal) Lumbars Common iliac Hepatic
23
Q
Mnemonic to remember direct tributaries
A
Portal System Returns To Liver In Humans
24
Q
What drains onto the left renal vein?
A
Left suprarenal
Left inferior phrenic
Left gonadal
25
Where does the right suprarenal vein drain onto?
IVC
26
What are the posterior & anterior vagal trunks (nerves)?
Branches of right & left vagus nerves (respectively)
27
What is the pathway of the anterior and posterior vagal trunk (nerves)?
Pass posterior to esophagus
| Reach celiac branch
28
Where does the foregut extend from and to?
Starts with abdominal esopahagus
| Ends halfway through descending part of duodenum
29
What is located halfway through the descending part of the duodenum?
Major duodenal papilla
30
What does the foregut encompass?
```
Abdominal oesophagus
Stomach
Duodenum (superior to major papilla)
Liver
Pancreas
Gallbladder
```
31
What does the respiratory diverticulum split into in its dorsal portion?
Esophagus & trachea
32
What separates the esophagus from the trachea?
Tracoesophageal septum
33
What does the respiratory diverticulum split into in its ventral portion?
Larynx
Trachea
Bronchi
Lungs
34
What are possible malformations of the esophagus?
Tracoesophageal fistula
Stenosis
Congenital hiatal hernia
35
What does a trachoesophageal fistula consist of?
Connection btw. esophagus and trachea
36
What does a tracoesophageal fistula manifest as?
Prenatally - Polyhydramnios
| Postnatally - regurgitation
37
What is the cause of esophageal stenosis?
Incomplete recanalization of esophagus (incomplete degeneration of epithelium & hollow gut tube
38
What does the recanalization of the esophagus consist of?
Gut tube is initially hollow
Endoderm proliferates rapidly & occludes lumen of gut tube
Apoptosis of endoderm causes recanalisation
Lumen open again (9th week)
39
What does the stomach initially appear as?
Dilation of foregut endoderm
40
3 key steps in development of stomach
1) Dilation
2) 90º clockwise rotation
3) Dorsal grows faster than ventral
41
What is the result of the rotation of the stomach?
Left side becomes anterior
| Right side becomes posterior
42
How does the rotation of the stomach affect the orientation of the vagus nerves?
Left vagus becomes anterior
| Right vagus becomes posterior
43
What is the final axis of the stomach?
Up & left
| Down & right
44
Why is the stomach not floating?
Because it is attached to dorsal and ventral mesogastrium
45
Why is the liver on the right?
Due to stomach rotation
46
Why is the pancreas a secondary retroperitoneal viscera?
Attached by dorsal mesogastrium --> pushed towards dorsal wall
Derivative of dorsal mesogastrium
47
What forms the omental bursa?
Greater omentum
48
Why is there a decrease in the size of the omental bursa?
Because 2 of the 4 layers of the greater omentum fuse
49
What does the hematopoietic function rely on before the 6th week of development?
Extraembryonic mesoderm
50
What does the hematopoietic function rely on after the 6th week of development?
Liver
51
Why are the pancreas & duodenum secondary retroperitoneal viscera?
Because they rotate to the right into the dorsal mesentery
52
What are the 3 key steps in the development of the pancreas?
1) Formation of dorsal & ventral pancreatic buds
2) Rotation of pancreas to the right
3) Fusion of dorsal & ventral pancreas
53
What does the midgut initially consist of?
U-shaped loop
| Superior & inferior branches Connected to dorsal wall by mesentery
54
What supplies the midgut loop and how does it do so?
Superior mesenteric artery
| Perforates through mesentery
55
What does the superior branch of the midgut loop give rise to?
Intestinal loops
56
What does the inferior branch of the midgut loop give rise to?
Large intestine derivatives
57
What does physiological umbilical herniation imply?
Superior branch of midgut loop grows too much
Not enough space in abdominal cavity for intestinal loops
Intestinal loops herniate (perforate) into extra embryonic coelom in umbilical cord
90º counterclockwise rotation
58
What occurs as a result of physiological umbilical herniation?
Superior branch = right
| Inferior branch = left
59
How and when does the reduction of the physiological midgut hernia take place?
180º counterclockwise rotation
| 10th week
60
What anomalies are associated with malrotation of gut?
Non rotation
Midgut volvulus
Reversed rotation
61
What occurs due to the anomaly of reversed rotation?
Duodenum anterior to colon
| Superior mesenteric artery compresses transverse colon
62
What midgut anomalies are NOT associated with rotation?
Meckel's diverticulum
Umbilical hernia
Omphalocele
Gastroschisis
63
Why does meckel's diverticulum occur?
Persistence of vitelline duct
64
Why do umbilical hernias occur (prenatally)
Abdominal musculature does not close properly
65
Why does an omphalocele occur?
Failure in reduction of physiological midgut hernia --> intestinal loops do not return to body cavity
66
Why does gastroschisis occur?
Due to incomplete closure of lateral foldings in 4th week
67
Where does the hindgut extend to and from?
Starts slightly before left colic flexure
| Ends halfway through anal canal
68
What is the cloaca?
Caudal portion of hindgut enclosed by cloacal membrane
69
What is the urorectal septum?
Septum that will grow between the allantois and the hindgut to separate the urogenital sinus from the anorectal canal
70
What develops within the allantois --> urogenital sinus?
Bladder
71
What area is located between the urogenital sinus (genitals) and the rectum (anus?
Perineum
72
What are the 2 divisions of the anal canal?
Anal pit
| Anal columns
73
What separates the anal pit from the anal columns?
Pectinate line
74
What causes an imperforate anus?
Persistence of cloacal membrane
75
What is the most common cause of congenital abnormalities of the hindgut?
Incorrect development of urorectal septum
76
What is Hirschsprung's disease AKA congential aganglionic megacolon?
Distal colon is aganglionic (no communication with CNS) therefore delay in progression of stool through intestines
77
What is the peritoneum?
Thin serous membrane lining abdominal cavity
78
What is the difference between parietal and visceral peritoneum?
Parietal lines walls of abdominal & pelvic cavities
| Visceral covers organs
79
What are intraperitoneal viscera?
Viscera FULLY surrounded by peritoneum
| WITHIN peritoneal cavity
80
What are primary retroperitoneal viscera?
Organs covered by peritoneum only on anterior surface
| Lie WITHIN posterior abdominal wall
81
What are secondary retroperitoneal viscera?
Initially intraperitoneal but lose mesentery due to development
82
What structures are continuous within the peritoneal cavity?
```
Greater sac (peritoneal cavity)
&
Lesser sac (omental bursa)
```
83
What does the greater omentum fuse with?
Transverse mesocolon
84
What does the greater omentum attach to?
Greater curvature of stomach
| 1st part of duodenum
85
What does the lesser omentum attach to and from?
From lesser curvature of stomach & 1st part of duodenum
| To inferior part of liver
86
What is the lesser omentum divided into?
Hepatoduodenal ligament
| Hepatogastric ligament
87
What are peritoneal reflections?
Point where mesenteries connect to the dorsal wall
88
What is the parietal peritoneum innervated by?
Somatic afferent fibers of spinal and phrenic nerves
89
What is the visceral peritoneum innervated by?
Visceral afferent fibers from autonomous N.S
90
What arteries supply the abdominal esophagus (at level of T10)?
Celiac trunk
- Left gastric artery
- Left inferior phrenic artery
91
What are the main regions of the stomach?
Cardia
Fundus
Body
Pylorus
92
What arteries supply the stomach?
Celiac trunk
- Left gastric artery
- Common hepatic artery
- Splenic artery
93
What branches does the left gastric artery give off?
Esophageal branches
94
What branches does the common hepatic artery give off?
Right gastric artery
Gastroduodenal artery
Proper hepatic artery
95
What branches does the splenic artery give off?
Left gastro-mental artery
| Short gastric arteries
96
What innervates the stomach (sympathetically)?
Greater splachnic nerve (T5-T9)
| Lesser splachnic nerve (T10-T11)
97
What innervates the stomach parasympathetically?
Vagus (synapse in wall of stomach)
98
What connects the liver to the anterior wall?
Falciform ligament
99
What is continuous (caudally) with the falciform ligament?
Teres ligament
100
What branches does the falciform ligament give off in the diaphgram?
Posterior (right) and Anterior (left) coronary ligaments
101
What branches do the anterior and posterior coronary ligaments give off?
Right and left triangular ligaments respectively
102
Where does the blood of the liver metabolism drain onto?
Systemic circulation via IVC
103
What do the gastric veins drain?
All of the blood of the foregut directly into portal vein
104
Where are the portosystemic anastamosis located?
1: level of esophageal veins (draining onto left gastric vein) that drain to azygos system
2: level of rectum
105
In which veins are varicosities most common in?
Esophageal and gastric veins
106
What is the transpyloric plane?
Imaginary horizontal plane at L1 level
107
What are the segments of the duodenum (in order)?
1) Superior
2) Descending
3) Inferior
4) Ascending
108
Which duodenal segments are intraperitoneal and which are retroperitoneal?
Intra: 1 and 4
Retro: 2 and 3
109
Arterial supply of duodenum
```
Proximal:
- Gastroduodenal
- Superior pancreaticoduodenal
Distal:
- Superior mesenteric
- Inferior pancreaticoduodenal
```
110
What are the main parts of the pancreas?
Head
Neck
Body
Tail
111
Which parts of the pancreas are intraperitoneal and which are retroperitoneal?
Intra: tail
Retro: head, neck and body
112
Where do the main pancreatic duct & bile duct enter into the duodenum?
Level of major duodenal papilla (2nd portion = descending)
113
Arterial supply of pancreas
Posterior wall of pancreas
Splenic artery gives 2 branches:
- dorsal pancreatic artery
- greater pancreatic artery
114
What is the exact location of the spleen?
Left hypochondrium associated with rib X
115
What is the connection between the spleen and the stomach?
Gastrosplenic ligament
116
What is the connection between the spleen and the left kidney?
Splenorenal ligament
117
BLOOD supply of the spleen
Splenic artery
| Splenic vein
118
What are the impressions on the visceral surface of the spleen?
Splenic - colon
Visceral - kidney
Diaphragmatic - stomach
119
How does the splenic vein pass in relation to the pancreas?
Posterior to pancreas
120
What is the main nerve that innervates (sympathetically) the spleen?
Greater thoracic splanchnic nerve
121
Where do the visceral afferent (sensory) neurons originate from?
Dorsal ganglia of afferent fibers from T5-L1 (foregut, midgut, hindgut)
122
What does the referred pain of the foregut address?
Visceral afferent innervation from T5-T9
123
What does the referred pain of the midgut address?
Visceral afferent innervation from T10-T11
124
What does the referred pain of the hindgut address?
Visceral afferent innervation from T12-L1
125
Where does the somatic pain of the diaphragm arise from?
Phrenic nerves from:
- C3 --> C5
- T5 --> T11
126
Where do jejunal and ilieal arteries arise from?
Superior mesenteric artery
127
What kind of loops do jejunum and ileum have?
Jejunum - Horizontal loops
| Ileum - Vertical loops
128
Arterial supply to the small intestine
Superior mesentery
Jejunal and ileal arteries
Vasa recta
129
The vasa recta of which intraperitoneal organ of the small intestine are longer?
Jejunum
130
From outermost to innermost what are the common layers between the jejunum and ileum?
```
Serosa
Longitudinal Muscular
Circular muscular
Submucosa
Mucosa
Circular folds
Solitary lymphoid nodule
```
131
What layer is specific to the ileum?
Aggregated lymphoid nodules
132
Are folds more prominent in the jejunum or in the ileum? Why?
In the jejunum (mucuous) for good absorption
133
What are the segments of the large intestine?
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
134
What segments of the large intestine are intraperitoneal?
Sigmoid colon
| Transverse colon
135
What segments of the large intestine are retroperitoneal?
Ascending colon
| Descending colon
136
What are 3 key characteristics of the colon?
Omental appendices
Taeniae coli
Haustras
137
What are omental appendices?
Small pouches (folds) of peritoneum filled with fat
138
What are taenia coli?
Longitudinal folds of smooth muscle on the outside of "4 colons"
139
What are haustrum?
Pouches of colon caused by sacculation (sacs joined together)
140
What are the transverse colon's relations?
Right colic flexure
| Left colic flexure
141
How are each of the segments of the colon (ascending, transverse, descending, sigmoid) organised in the 9-region organisational pattern?
Ascending - right flank
Descending - left flank
Sigmoid & transverse - pubis
142
Arterial supply of colon arising from the superior mesenteric artery
Branches to the RIGHT
Ileocolic
Right colic
Middle colic
143
Arterial supply of colon arising from the inferior mesenteric artery
Branches to the LEFT
Left colic
Sigmoid
Superior rectal
144
Where do anastomosis branch off in the arterial supply of the colon?
Middle colic artery
| Left colic artery
145
Describe the venous drainage of the colon (in terms of right vs left)
Right to superior mesenteric vein
| Left to inferior mesenteric vein
146
What sympathetically innervates the large intestine?
Thoracic splanchnic nerves (greater T5-T9 & lesser T10-T11)
| Lumbar splanchnic nerves (L3-L4)
147
What parasympathetically innervates the large intestine?
Vagus
| Pelvic splanchnic
148
What is the ileocecal junction?
Junction btw. small intestine & large intestine
149
Where does the teania coli end?
Appendix (subcecal & pelvic orientations)
150
What is the enteric nervous system?
Local nervous system present ONLY in GI tract
Independent of CNS
Controlled by ANS
151
What sympathetically innervates the small intestine?
Greater splanchnic nerve (T5-T9)
| Lesser splanchnic nerve (T10-T11)
152
What parasympathetically innervates the small intestine?
Vagus
153
What are the 3 functions of the enteric system?
Gastric secretion
Gastrointestinal blood flow
Peristalsis
154
What are the plexus of the enteric system?
Myenteric
| Submucosal
155
At what level is the myenteric plexus located?
Level of circular muscle layer
156
At what level is the submucosal plexus located?
Submucosa layer
157
What is the pelvic floor?
Muscles located between coccyx & pubic bone that support bowel, bladder, uterus and vagina
158
What are the main muscles of the pelvic floor?
Iliococcygeous
Pubococcygeous
Puborectalis
159
What is the anorectal junction?
Ring that connects the anus with the rectum
160
What is the anorectal flexure?
A bend at anorectal junction as the rectum passes through the pelvic diaphragm muscles
161
What is the orientation of the anorectal flexure?
80º
162
What is the ischioanal/ischiorectal fossa?
Triangular shaped pyramid filled with fat lateral to anal canal & below pelvic diaphragm
163
In what part is the ischioanal fossa covered COMPLETELY with peritoneum?
Proximal portion
| Lateral sides
164
In what surfaces is the ischioanal fossa covered ONLY ANTERIORLY with peritoneum?
Middle portion
165
In what surfaces is the ischioanal fossa NOT covered at all with peritoneum?
Distal portion
166
What are the transverse mucosal rectal folds?
Folds of the rectal wall (that function as valves) that protrude into the rectum
167
What are prominent transverse mucosal folds?
Superior rectal valve
Middle rectal valve
Inferior rectal valve
168
Arterial supply of the rectum
Superior rectal artery
Middle rectal artery
Inferior rectal artery
169
Arterial supply of the anal canal
Middle rectal artery
| Inferior rectal artery
170
Venous drainage of rectum & anal canal
Upper 2/3: superior rectal vein --> inferior mesenteric vein & portal vein
Lower 1/3: middle rectal vein
171
Where are the anastomosis of the rectum and anal canal located?
Upper part of the anal canal
| Between portal veins (superior rectal veins) and systemic veins (middle & inferior rectal veins)
172
What are hemorrhoids?
Swollen veins in lower rectum
173
What innervates the rectum & anal canal (above pectinate line)?
Visceral innervation via inferior hypogastric plexus
174
What innervates the rectum & anal canal (below pectinate line)?
Sommatic innervation via inferior rectal nerves
175
What allows conscious control of defecation?
External anal sphincter control by somatic nerve supply from inferior anal branch of pudendal nerve
176
How does the involuntary control of defecation work?
Via the rectoanal inhibitory reflex
177
What does the rectoanal inhibitory reflex imply?
Involuntary internal anal sphincter relaxation in response to rectal distension
