Development Of The Gut Flashcards
1
Q
Gut is formed of
A
Endoderm (mucosa) and splanchnic mesoderm (lateral mesoderm: smooth muscle, connective tissue, serosa)
2
Q
Gut endoderm parts
A
Gut endoderm separates from yolk sac endoderm during embryo folding; defined as foregut, midgut, hindgut
3
Q
Foregut arterial supply
A
Celiac artery
4
Q
Midgut arterial supply
A
Cranial mesentery artery
5
Q
Hindgut arterial supply
A
Caudal mesentery artery
6
Q
Foregut components
A
Stomach, cranial duodenum, and foregut diverticula (liver, gallbladder, bile ducts, ventral and dorsal pancreas)
7
Q
Midgut components
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Caudal duodenum, jejunum, ileum, cecum, ascending colon, right transverse colon
8
Q
Hindgut
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Left transverse-colon, descending colon, rectum, cranial anal canal
9
Q
Gut suspension dorsal abdominal wall
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Suspended within the coelom (peritoneal cavity) by the dorsal mesentery
10
Q
Ventral mesentery attachment
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Found only attached to the stomach (ventral mesogastrium)
11
Q
Greater omentum
A
Forms when stomach rotates left and dorsal megogastrium grows
12
Q
Lesser omentum
A
Ventral mesogastrium becomes lesser omentum, and connects stomach to liver and liver to body wall via falcifor ligament
13
Q
Falciform ligament
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Connects stomach to liver and liver to body wall
14
Q
Omental bursa
A
Pouch/ fold formed by greater omentum; ventral side is superfical leaf (holds spleen); dorsal side is deep leaf (holds pancreas)
15
Q
Midgut loop
A
Rotates 270 degrees counter clockwise from ventral vein about cranial mesenteric arterial axis
16
Q
Most specialized part of the gut
A
Ascending colon and rumen are most specialized part of the gut modified in domestic species to accomidate specialized diet
17
Q
Digestive enzymes in stomach come from what type of gland
A
Exocrine
18
Q
Nutrient absorption digestive tract
A
Absorption takes place across the mucosal wall (villi) into associated capillary beds of the blood vascular system and into lymphatic system
19
Q
Lymphatic system digestive system
A
Absorbs all dietary fats including fat-soluble vitamins via lacteals (lymphatic capillaries) located inside each intestinal villus
20
Q
Tunics of gut tube
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Mucosa, submucosa, muscle, and serosa
21
Q
Peritoneal organs serosa or adventitia
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Serosa
22
Q
Retroperitoneal organs serosa or adventitia
A
Adventitia
23
Q
Main function of adventitia
A
Bind structures
24
Q
Main function of serosa
A
Lubrication (reduce friction due to muscle movement)
25
Serous cavities
Pericardial, pleural, peritoneal
26
Organs with in a cavity serosa vs adventitia
Generally bounded by serosa
27
Organs bound to body wall
Generally covered by adventitia (more restricted in terms of movement)
28
Epithelial lining of alimentary canal
(Mucosa closest to lumen); includes specialization that increase absorptive area from folds in luminal wall to villi in mucosa and microvilli on the absorptive epithelial cells
29
Mesoderm gut
Mesoderm (derived from splanchnic mesoderm) forms the tunica submucosa, tunica muscularis, tunica adventita/ serosa
(These make up muscle, connective tissue, vessels, mesenteries, and serosa)
30
Muscularis externa adventita or serosa
Serosa
31
Oral cavity, thoracic, esophagus, ascending colon, descending colon, and rectum adventita or serosa
Adventita
32
Embryonic gut
Composed of endoderm and mesoderm in tubular arrangement
33
Endoderm embryonic gut
Forms epithelial lining of gut (tunica mucosa) where villi form; exceptions: oral cavity and anus have epithelial lining derived from ectoderm
34
Embryonic gut tube formation
Forms during embryo folding bc embryo disc grows more rapidly than extraembryonic tissue with which embryo is continuous, disk buckles up while edges fold under; gut endoderm recruits adjacent splanchnic mesoderm to form rest of gut (smooth muscle, connective tissue ect)
35
Dorsal mesentery
As embryonic folding is completed a neck of splanchnic mesoderm remains; connects gut tube along entire axial length to dorsal portion of abdominal body wall; primitive gut tube is suspended within the coelom/ coelomic cavity from dorsal abdominal body wall by dorsal mesentery
36
Dorsal mesentery product of
Fusion of left and right splanchnic mesoderm layers and is therefore a double-layer mesoderm with one side derived from left side and one from right side
37
Formation of dorsal mesentery
Separates coelom into left and right cavity
38
Ventral mesentery
Only attaches stomach to ventral body wall
39
Peritoneal cavity comes from
Coelomic cavity, forming parietal peritoneum and visceral peritoneum which are continuous
40
Tube with in a tube body plan
Outer tube is ectodermal forms skin inner tube is endodermal forms gut; space between two tubes is filled mainly with lateral mesoderm
41
Somatopleure
Outer tube (body wall) formed from this (composed of somatic mesoderm external to coelom plus ectoderm); also origin of amnion and chorion
42
Splanchnopleure
Inner tube (gut) composed of splanchnic mesoderm internal to coelom plus endoderm; also origin of allantois and yolk sac
43
Parietal peritoneum mesoderm
Derived from somatic mesoderm will line body wall
44
Visceral peritoneum
Derived from splanchnic mesoderm, will line organ
45
Lateral mesoderm
Somatic and splanchnic mesoderm both derived from lateral mesoderm as are extraembryonic membranes
46
Foregut
Supplied by branches of celiac artery; abdominal esophagus, stomach, and cranial half of duodenum, liver, and pancreas (diverticula of foregut)
47
Midgut
Supplied by branches of cranial mesenteric artery; include caudal part of duodenum, jejunum, ileum, cecum, ascending colon, right side of transverse colon
48
Hindgut
Supplied by branches of caudal mesenteric artery; left part of transverse colon, descending colon, rectum, and anal canal
49
Unpaired arteries in abdominal region
Off of the dorsal aorta 3 main unpaired arteries are celiac artery, cranial mesenteric artery, and caudal mesenteric artery
50
Peritoneum histology
Consists of a layer of simple squamous epithelial cells called mesothelium and secretes lubricating fluid
51
Peritoneal ligaments, mesenteries, and omertà
Serve as boundaries for disease processes and conduits for disease spread (flow of peritoneal fluid determines route of spread of intraperitoneal disease in abdominal cavity)
52
Oxygen and nutrient supply to looping gut
Derived by vessels of dorsal mesentery (mesentery is the conduit for blood and lymphatic vascular channels as well as nerves)
53
Transport of dietary fats
Lymphatic system in the gut is sole conduit for transport of dietary fats via lacteal capillaries within the villi
Lacteal capillaries within villi -> packaged into chylomicrons once reach villus-> transported to lacteals -> mesenteric lymphatics -> thoracic duct -> heart -> systemic circulation -> reach liver as chylomicron remnants via the hepatic artery
54
Dorsal mesentery suspending stomach (during development)
Dorsal mesogastrium
55
Dorsal messentery suspending duodenum during development
Mesoduodenum
56
Dorsal mesentery suspending jejunum during development
Mesojejunum
57
Dorsal mesentery suspending ileum during development
Mesoileum
58
Dorsal mesentery suspending colon during development
Mesocolon
59
Dorsal mesentery suspending rectum during development
Mesorectum
60
Dorsal mesogastrium in development
Stomach rotates as it developed attached dorsal mesogastrium comes along for the ride and becomes drawn out caudally and folded on itself (at this stage it is the greater omentum)
61
Omental bursa
Created by folding of stomach and formation of greater omentum this is the space between the superfical and deep leaves of greater omentum
62
Walls of greater omentum
Greater omentum of dog turned caudally between viscera and abdominal floor; superfical leaf faces ventral side, deep leaf faces the dorsal side
63
Epiploic foramen
Aka omental foramen; small opening through which cavity of omental bursa remains in open communication with major part of peritoneal cavity
64
Ventral mesogastrium development
Growth of liver divides ventral mesogastrium into two parts, lesser omentum and falciform ligament
65
Lesser omentum
Part of ventral mesogastrium immediately between the stomach and the liver; connects stomach to liver
66
Falciform ligament
Part of ventral mesogastrium between liver and ventral abdominal body wall (connects liver to abdominal floor)
67
Stomach attachment and location
Stomach always on left side; cranial attachment to esophagus at cardia inflow; caudal attachment to duodenum at pyloric sphincter; suspended dorsally by dorsal mesogastrium (becomes greater omentum); suspended ventrally by ventral mesogastrium (becomes lesser omentum and falciform ligament)
68
Greater curvature and lesser curvature of stomach
Dorsal wall grows much faster than ventral wall of the stomach results in greater curvature of initially dorsal side and lesser curvature on the ventral side
69
Fundus
Forms because of differential growth leading to formation of greater and lesser curvature
70
Stomach rotations
First rotation rotates 90 degrees to left, carries dorsal aspect left (greater curvature always rotates to left side); second rotation 90 degrees caudally (carries greater curvature to caudal position and original ventral margin the lesser curvature is now oriented cranially)
(Lesser curvature faces up and greater curvature faces down)
71
Inflow and outflow stomach
Inflow is on the left and dorsal outflow is on the right and mid-ventral
72
Greater omentum
Rotations of stomach take dorsal mesogastrium along with them and it rotates and becomes drawn out caudally and folded on itself and dorsal mesogastrium is now greater omentum
73
Greater omentum in adult dog
Huge surface area and lace-like (fat deposits) first structure to appear when abdominal wall is opened in adult along ventral midline
74
Greater omentum extends caudally
Forms a pocket (omental bursa), ventral side (superfical leaf; holds spleen), dorsal side (deep leaf; holds pancreas)
75
Pneumogastrogram
Radiograph of airfilled stomach
76
Primary midgut loop
Size of developing gut exceeds capacity of embryonic body cavity primary midgut loop forced ventrally into umbilicus (in mammals yolk sac in birds) and forms physiological hernia
77
Cranial mesenteric artery during rotation of midgut
Primary midgut loop forms physiological hernia, midgut loop remains attached to dorsal abdominal wall by dorsal mesentery, cranial mesenteric artery courses ventrally through this dorsal mesentery
78
Cranial half of midgut loop
Will form small intestine (distal part of duodenum, jejunum, and ileum
79
Caudal half of midgut loop
Will form terminal ileum, cecum, ascending and right side of transverse colon; with rotation cranial half of loop will shift caudally and caudal half of loop will shift cranially
80
Conserved 90 degree counterclockwise rotation in midgut rotation
This comes after primary midgut loop formation; initiates midgut rotation and brings caudal half of loop cranially on the left side of the cranial mesenteric artery with cranial part on right
81
Second rotation of midgut
180 degrees follows subsequent retraction of gut into body cavity
82
Additional loops of midgut
Additional loops are formed along original cranial half of midgut loop as small intestine elongates to further acomidate efficient packing; original cranial half of the loop forms the small intestine; caudal half forms the ascending transverse colon
83
First 90 degree rotation direction
Direction of this is critical for proper positioning of the small intestine with respect to the large intestine and for all other aspects of asymmetrical visceral placement
84
Direction of first 90 degree rotation of midgut directed by
Left right asymmetries in dorsal mesentery (left side of dorsal mesentery shortens while right side lengthens); serves as directional bias for subsequent counterclockwise corkscrewing of gut as it herniated
85
Midgut volvulus or gastric dilation volvulus
Arise due to malrotaiton of the gut tube
86
Hepatic portal circulation
Drains the gut
87
Lympattic vasculature
Transport all dietary fat
88
Liver development
Endodermal diverticulum (hepatic diverticulum); forms at junction of hindgut and midgut; diverticulum = outpocketin of a structure; divided into two branches cranial branch and caudal branch; major stem of liver diverticulum is bile duct
89
Cranial branch of hepatic diverticulum
Forms liver and hepatic ducts of the liver (transport bile from the liver)
90
Caudal branch of hepatic diverticulum
Forms gallbladder, cystic duct of gallbladder (transports bile) and ventral pancreas
91
Bile duct
Major stem of liver diverticulum where cystic duct and hepatic ducts meet; joins liver with duodenum and carries hepatic bile;
92
Path of bile
Liver -> hepatic ducts -> cystic duct -> bile duct -> duodenum,
93
Hepatic cords
Cranial branch of hepatic diverticulum extend finger like processes into splanchnic mesoderm of adjacent septum transversum the fingers are a result of repetiative branching and represent hepatic cords that later form bile canaliculi
94
Hepatocytes
Endodermal cells that line canaliculi differentiate as hepatocyte (epithelial cells)
95
Hepatic sinusoids
As more vessels pass through liver hepatic cords break venous blood vessels into smaller hepatic sinusoids (endothelial cells, similar to blood capillaries)
96
Site of bile duct
Initially ventral diverticulum but entery into duodenum shifts to dorsal site slightly caudal to pyloris of the stomach bc stomach rotation
97
Gall bladder development
Diverticulum from liver hepatic diverticulum remains attached via cystic duct (no gall bladder in horse)
98
Attenuation of connection between liver and stomach
Forms lesser omentum (ventral mesogastrium)
99
Attenuation of the connection between the liver and ventral abdominal wall
Forms falciform ligament (remnant of umbilical vein)
100
Pancreas development
Arises from same portion of foregut as liver; two primordial form but eventually fuse (dorsal pancreatic diverticulum and ventral pancreatic diverticulum)
101
Dorsal pancreatic diverticulum
Arises from dorsal margin of duodenum close to pylorus and developers along greater curvature of stomach; “left lobe” of pancreas in an adult, head and body of pancreas
102
Ventral pancreatic diverticulum
Comes from base of liver hepatic diverticulum
103
Bile duct during stomach rotation
Shifts dorsally as does ventral pancrease
104
Major duodenal papilla
Ventral and dorsal pancrease fuse and ventral pancreatic duct remains primary exocrine drainage for pancrease and enters duodenum at major duodenal papilla adjacent to bile ducts
105
Synthesis and secretion of the digestive enzymes in pancrease
Occurs within acini at end of each ductule
106
Endocrine function in pancrease
Endocrine function occurs in islets of langerhans (glucagon an dinsulin)
107
Blood supply to liver and pancrease
Achieved via celiac artery bc both derived from foregut
108
Modifications of the gut for specialized diets
- increase length of gut (ascending colon and cecum) (hind gut fermenters)
- modification of the stomach (foregut, rumen) (forgut fermenters)
109
Ascending colon
Most specialized part of intestinal tract; in hind gut fermenters ascending colon and cecum represent fermentation chambers
110
Ascending colon dog
Does not undergo additional rotations, remains as a straight tube within the right dorsal part of abdominal cavity
111
Ascending colon horses
Forms dorsal and ventral (left right) colon separated by flexure and enlarged cecum
112
Sternal flexure
Separates ventral right from ventral left segment of colon in horse
113
Pelvic flexure
Separates ventral left from dorsal left portions of colon in horse
114
Diaphragmatic flexure
Separates dorsal left and dorsal right colon in horses
115
Abdominal topography of horse
Dominated by large intestine
116
Ascending colon in cows
Forms double spiral
117
Abdominal topography of the cow
Dominated by rumen
118
Ascending colon in pigs
Forms spiraling conical set of loops: spins in and down then up and out
119
Cow stomach
Enormous stomach, fills left half and some of right half of abdominal cavity; large chamber is the rumen, dedicated to storing gas and mixing with symbiotic bacteria; opens into reticulum (highly folded inner walls); cow regurgitates cud swallows to third chamber omasum (water is withdrawn for recycling) cud then enters true stomach (abomasum) where chemical digetion begins
120
Bovine calf digestion
Functionally mongastric animal milk bypassses rumen, reticulum, and omasum and goes directly to abomasum; rumen development commences on forage feed
121
Mesenteries in ruminants
Assume farmiliar topography as greater and lesser omenta
