Embryology Flashcards
1
Q
Foregut starts
A
Distal oesophagus
2
Q
Foregut ends
A
Halfway along the duodenum
3
Q
Midgut starts
A
Halfway along the duodenum
(Just distal to the entrance of the bile duct)
4
Q
Midgut ends
A
Junction of the proximal 2/3 of the transverse colon
5
Q
Hindgut starts
A
Distal 1/3 of transverse colom
6
Q
Hindgut ends
A
Upper anal canal
7
Q
Arterial supply of foregut
A
Coeliac trunk
8
Q
Arterial supply of midgut
A
Superior mesenteric artery
9
Q
Arterial supply of Hindgut
A
Inferior mesenteric artery
10
Q
Sympathetic innervation of the foregut
A
Greater splanchnic nerve (T5-9)
11
Q
Sympathetic innervation of the midgut
A
Lesser splanchnic nerve (T10-11)
12
Q
Sympathetic innervation of the Hindgut
A
Least splanchnic nerve (T12) and lumbar splanchnic nerves (L1)
13
Q
Parasympathetic innervation of the foregut
A
Vagus
14
Q
Parasympathetic innervation of the midgut
A
Vagus
15
Q
Parasympathetic innervation of the Hindgut
A
Pelvic splanchnics
16
Q
Visceral pain of the foregut is felt in
A
Epigastric region
17
Q
Visceral pain of the midgut is felt in
A
Umbilical region
18
Q
Visceral pain of the Hindgut is felt in
A
Suprapubic region
19
Q
Gastrulation
A
Epiblast cells migrate to the primitive streak and invaginate through it
Some cells displace the hypoblast and form the endoderm
Some cells create a new layer between the Epiblast and endoderm = mesoderm
Epiblast = ectoderm
20
Q
What does the visceral mesoderm become
A
Muscle walls
Visceral peritoneum
21
Q
What does the endoderm become
A
Gut lining
22
Q
Vitelline duct
A
Closure of the gut tube along its length except for a connection that remains between the midgut region and yolk sac
Narrows and degenerated during gestation
23
Q
Umbilical cord
A
Closure of the ventral body wall complete except at the connecting stalk
24
Q
When does Gut tube differentiation occur
A
Gut tube starts to differentiate whilst lateral folding is bringing the ventral body wall together
25
What causes gut tube differentiation
Concentration gradient of retinoic acid
26
Where are the lowest levels of retinoic acid
Cranially
27
Where are the highest levels of retinoic acid
Distally
28
What specifies how regions of the gut tube develop
Differential expression of transcription factors and genes
29
What does the parietal mesoderm give rise to
Parietal peritoneum
30
Foregut includes
Oesophagus
Stomach
First 1/2 of duodenum (1st and 2nd parts)
31
Formation of primitive gut tube
during week 3-4 by incorporating the yolk sac during craniocaudal and lateral folding of the embryo
primitive gut is formed when a portion of the yolk sac becomes incorporated into the embryo, which occurs due to the cephalocaudal and lateral folding of the embryo. The portions that remain outside the embryo are the yolk sac and the allantois. The primitive gut forms a blind-ended tube on both the cephalic and caudal ends of the embryo, forming the foregut and the hindgut, respectively. The middle part forms the midgut, but remains temporarily connected to the yolk sac via the vitelline duct (yolk stalk).
32
Failure of closure during lateral folding in thoracic region
Ectopia cordis
33
Failure of closure during lateral folding in abdomen
Gastroschisis
34
Failure of closure during lateral folding in pelvic region
Bladder exstrophy
35
Foregut derivatives
Liver
Pancreas
36
Foregut mesenteries
Dorsal mesentery
Ventral mesentery
37
Formation of the oesophagus
Lung bud appears at ventral wall of the foregut in the 4th week
Become separated from each other
38
What suspends the gut tube from the posterior wall within the developing embryo
Dorsal mesentery
39
When does the stomach begin to dilate
Week 4
40
Formation of stomach
Section of gut tube starts to dilate
Changes shape due to different rates of growth of different parts
Changes position-rotates 90 degrees clockwise around its long axis; brings the left side to lie anteriorly and the right side to lie posteriorly
Brings duodenum to the right
41
How does the developing stomach rotate
90 degrees clockwise around its long axis
42
When does the liver bud appear
Week 3
43
Development of the liver
Liver bud is an outgrowth from the distal foregut
Cells proliferate into the septum transversum (mesoderm)
Connection between the liver bud and foregut (duodenum) narrows —> bile duct
As the liver grows, endoderm of the septum transversum forms the falciform ligament and lesser omentum
44
How does the bile duct form
Connection between the liver bud and foregut (duodenum) narrows
45
What connects part of the foregut to the anterior wall
Ventral mesentery
46
Tracheoesophageal septum
Forms between the trachea and pharynx/oesophagus to separate them
47
Formation of the gallbladder
Small outgrowth from the bile duct
48
Oesophageal atresia
Oesophagus doesn’t form
49
Tracheoesophageal fistula
Unusual connection between the oesophagus and trachea
50
What does the mesoderm of the liver septum transversum form
Falciform ligament
Lesser omentum
51
What does the ventral mesentery split into
Lesser omentum
Falciform ligament
52
Lesser omentum
Connects the liver to the stomach and duodenum
53
Falciform ligament
Connects the liver to the anterior abdominal wall
54
Development of the pancreas
Dorsal and ventral buds arise from the duodenum
Dorsal bud develops in dorsal mesentery
Rotation of the stomach swings the ventral bud posteriorly
Dorsal and ventral buds fuse
55
Final position of the stomach
Rotation of the stomach brings its left side anteriorly and swings the duodenum right
56
Final position of the dorsal mesentery
Along the greater curvature of the stomach bulges down and grows- greater omentum
Becomes fixed to the mesentery of the transverse colon (and posterior wall)
57
Final position of the pancreas and duodenum
Brought into contact with the posterior abdominal wall and become retroperitoneal
58
Lesser sac
Small space behind the stomach between the stomach and liver
59
Where does the liver develop
In the ventral mesentery
60
Greater sac
Larger part of peritoneal cavity
61
Greater omentum
Dorsal mesentery along the greater curvature bulges down and grows
Becomes fixed to the mesentery of the transverse colon and posterior wall
62
What cause changes to the positions of the mesenteries, omenta, peritoneal ligaments and organs
Rotation of the stomach (90 degrees clockwise)
63
5 stages of midgut development
Elongation
Physiological herniation
Rotation
Retraction
Fixation
64
Elongation of midgut
Formation of primary intestinal loop
Connection to the yolk sac (the vitelline duct) is maintained but narrows
65
2 limbs of primary intestinal loop
Cephalic limb
Caudal limb
66
Cephalic limb of primary intestinal loop
Distal part of the duodenum
Jejunum part of the ileum
67
Caudal limb of the primary intestinal limb
Distal part of the ileum
Caecum
Appendix
Ascending colon
Proximal 2/3 transverse colon
68
Caecal bud
Develops on caudal limb of intestinal loop
69
When does physiological herniation occur
6th week
70
Physiological herniation
Intestinal loops herniate into the umbilical cord as abdominal cavity is too small for the gut loops and the liver which are both rapidly growing
During herniation, gut loop starts to rotate
71
Rotation of midgut
90 degrees anticlockwise as viewed from the front around the axis of the superior mesenteric artery
Brings the caudal limb more cranially
72
What will the caudal limb form
More distal parts of midgut
73
What axis does the primary intestinal loop loop around
Superior mesenteric artery
74
At what angle does the midgut rotate
90 degrees anticlockwise
75
Continued elongation of midgut
Elongation continues: the part destined to become small intestine develops coils
Segment destined to become large intestine also elongates but doesn’t coil
76
When does retraction of midgut occur
Week 10
77
Retraction of midgut
Gut loop returns to abdomen
Gut loop rotates a further 180 degrees anticlockwise
78
Total rotation of gut loop
270 degrees anticlockwide
79
Which part of midgut returns to abdomen first during retraction
Jejunum on left side
80
Which part of midgut returns to abdomen second during retraction
Ileum
Settles towards the right
81
Which part of midgut returns to abdomen last during retraction
Caecum
Returns to right upper quadrant then descends to right iliac fossa so ascending limb settles on right
82
Which primary intestinal limb coils
Cephalic limb
83
Fixation of midgut
Some mesenteries come into close contact with the posterior abdominal wall and become fused / fixed to the posterior wall- They are considered ‘retroperitoneal’
Where this happens, a fascial layer – Toldt fascia – develops between the parietal peritoneum on the posterior body wall and the visceral peritoneum on the organ
84
Toldt fascia
A fascial layer that develops between the parietal peritoneum on the posterior body wall and the visceral peritoneum on the organ
85
Final position of Jejunum
Central Upper left
86
Final position of ileum
Central lower right
87
Final position of ileum to caecum
On the right
88
Final position of caecum
Right iliac fossa
89
Dorsal mesentery of small intestine rotates around…
Superior mesenteric artery along with gut loop
90
Caecal bud final position
Once gut returns to abdomen, Caecal bud is first in upper right quadrant
It descends to the right iliac fossa as the ascending colon lengthens
91
When does appendix develop
During descent of Caecal bud
92
Which primary intestinal loop limb retracts into abdomen first
Cephalic limb
93
Meckel’s diverticulum
In up to 4% of people vitelline duct persists to form an out-pouching from the ilium – a ‘diverticulum’
Normally asymptomatic
May ulcerate and bleed
Inflammation can mimic appendicitis
94
Omphalocoele
Midgut loop doesn’t return to the abdomen in the 10th week; remains in the umbilical cord
Gut is covered with a layer of amnion
High mortality – often associated with other congenital and chromosomal anomalies
95
What does the last part of the Hindgut communicate with
Cloaca
96
Urorectal septum
Grows towards the cloacal membrane and separates the urogenital sinus from the cloaca
Separates urinary bladder/ureter and anorectal canal
97
Pelvic splanchnic nerves contain which type of fibres
Parasympathetic
98
Greater, lesser, least, lumbar splanchnic nerves contain which type of nerve fibres
Sympathetic
99
The primary intestinal loop forms during which stage of midgut development?
Elongation
100
Intestinal loops herniate into the umbilical cord during which week?
6th
101
Intestinal loops return to the abdomen in which week?
10th
102
In total, the gut loop rotates:
270 degrees anticlockwise
103
Anorectal canal
Ectoderm invaginates to form anal pit and lower part of anorectal canal
Cloacal membrane ruptures - upper and lower parts of anal canal become continuous with each other
104
What does the anal canal arise from
Endoderm and ectoderm
105
Is the caecum Intraperitoneal or retroperitoneal
Intraperitoneal
[no mesentery]
106
Is the sigmoid colon Intraperitoneal or retroperitoneal
Intraperitoneal
107
Do Intraperitoneal or retroperitoneal viscera have a mesentery
Intraperitoneal
108
Appendix position
Can lie in a variety of position
Base of appendix is constant [McBurney’s point]
109
Congenital abnormalities can occur with midgut development
Gut rotation - clockwise?
Return of the gut loops to the abdomen
Mesenteries formation - Volvulus
110
Cloaca
Blind-ended sac
Receives last part of Hindgut and distal parts of urinary tract
111
Lining of cloaca
Endoderm
112
Cloacal membrane
Ectoderm
Outer wall of embryo
113
Anal pit
Formed by invagination of ectoderm at end of anorectal canal
114
Imperforate anus
Failure of breakdown of cloacal membrane
No continuity of anal pit and rectum
