the gut and its derivatives Flashcards
1
Q
what is the arterial supply of the oseophagus
A
oseophageal arteries arise from the thoracic aorta, bronchial arteries and ascending branches of left gastric artery in the abdomen
2
Q
what is the venous drainage of the oseophagus
A
small vessels returning to the azygous vein, hemiazygous vein, oesophageal branches to the left gastric vein in the abdomen
3
Q
what is the lymphatic drainage of the oseophagus
A
posterior mediastinal and left gastric nodes
4
Q
how is the oseophagus innervated- list three components of the innervation
A
autonomic nervous system
thoracic part-oesophageal plexus which recieves parasympathetic supply from the vagus nerve and sympathetic innervation from the cervical sympathetic trunk
abdominal part
afferent
5
Q
where does the thoracic part get innervated from
A
oseophageal plexus which recieves parasympathetic supply from the vagus nerve and sympathetic innervation from the cervical sympathetic trunk
6
Q
where does the abdominal part get innverated from
A
parasympathetic innervation- arises from thoracic esophageal nervous plexus while its sympathetic component originates from fifth to twelth thoracic spinal nerves t5-t12
7
Q
where does the afferent part get innervated from
A
travel via vagus nerve can sense osmo,chemo, thermo and mechanical stimulus
8
Q
what are the three layers of the stomach
A
mucosa- innermost layer, releases stomach acid
submucosa- second layer, contains nerve endings and blood vessels
muscularis- muscles-circular muscle layer, longitudinal muscle layer
serosa- outer lining of gi tube
9
Q
what are gastric folds or gastric rugae
A
ridges of mucosal and submucosal layers allow for the stomach to expand
sphincter- ring of smooth muscle that can relax to allow passage of some contents
10
Q
list and explain two spincters in the stomach
A
cardiac sphincter
pyloric sphincter
11
Q
what is the function of the cardiac sphincter
A
trpa and keep acid inside stomach, prevents acidic contents of stomach moving upward to eosphagus (acid reflux)
12
Q
what is teh function of the pyloric sphincter
A
separates stomach from small intestine
13
Q
hiatal hernia
A
14
Q
what is the primary function of the small intestine
A
primary site of absorption of nutrients from food
consists of three parts dudodenum, jejunum, ileum
15
Q
explain the dudodenum
A
shortest- c shaped retroperiotoneal secondary retroperitoneal is where preparation for absorption through small finger like protusions called villi begins secndarily retroperitoneal
16
Q
explain the jejunum
A
specialised for absorption of nutrients interperitoneal
17
Q
explain the ileum
A
absorbs vitamin b12 bile salts and remaining products of digestion interperitoneal
18
Q
what is the dudodenum
A
where acidic chyme from the stomach mixes with bile (emulsifier) from the gall bladder and bicarbonate (Neutralises acid) digestive enzymes from pancreas
19
Q
what are the four parts of the dudodenum
A
superior
descending
horizontal
ascending
20
Q
which part of the dudodenum is intraperitoneal
A
the first part if intraperitoneal whereas the other three parts are secondary retroperitoneal
21
Q
what are the three main arteries that branch off the aorta and supply the gut
A
coeliac trunk
superior mesenteric artery-distal part of dudodenum all of jejunum and ileum and ascending colon and proximal 2/3 of transverse
inferior mesenteric artery
22
Q
what are the vertebra levels of the three main arteries that branch off aorta and supply teh gut
A
coeliac t12
superior mesenteric artery l1
inferior mesenteric artery l3
23
Q
what does the superior mesenteric artery supply
A
distal part of duodenum all of jejunum and ileum, ascending colon and proximal 2/3 of transverse colon
24
Q
what are the three named branches of the superior mesenteric artery
A
middle colic artery
right colic artery
ileocolic artery
25
what is the blood supply of the appendix
the appendicular artery is a branch of the ileocecal artery
26
what does the inferior mesenteric artery supply
supplies distal 1/3 of the transverse colon, descending colon, sigmoid colon, poximal rectum
27
what are the three veins that make up venous drainage of the gut
splenic vein
superior mesenteric vein
inferior mesenteric vein
they all drain into hepatic portal vein
they bring nutrients and toxins to the liver for processing
28
what are the two venous drainage systems in the abdomen
left and right iliac veins join to form the inferior vena cava,
inferior vena cava recieves blood from the low limbs, abdominal wall, gonads, kidneys and adrenal glands
blood from the gut and spleen drain into hepatic portal vein then in to hepatic veins to connect to the ivc
29
what is the function of the liver
filter blood from gi tract
before returning it to venous drainage
30
what are the four lobes of the liver
right, left, caudate, quadrate
31
what are the liver ligaments
double layer folds of peritoneum that attach body wall to organs
32
what does the falciform ligament do
divides the left and right lobes and connects liver to body wall
33
what is the round ligament of the liver
ligamentum teres hepatis
remnants of embryonic umbilical vein
34
what is the coronary ligament
attaches the liver to the diaphragm and the right kidney to the adrenal gland
35
what is the bare area of the liver
the region of the liver not covered with the peritoneum where the liver is connected to the diaphragm directly with loose connective tissue
36
what is the portal triad
hepatic portal vein
hepatic artery
bile duct
sits inside the hepatodudodenal ligament on the edge of the lesser omentum
37
how does hepatic segmentation work
functional sub division of the liver
2 functionally independent portal lobes called left and right livers divided based on the primary branches of hepatic artery and hepatic portal vein
liver can be divided into 8 sgements
38
what is the portal caval anastomoses
bottom of esophagus- some veins that go down into portal vein some that go directly into ivc
portal veins- superficial veins directly into caval systsem
top part of rectum drains into portal system whereas bottom part drains into caval system
this is where portal caval system interact,
39
40
GI smooth muscle
Gi motility depends on smooth muscle contractions
functions of gi motility-
mixing
propulsion
Gi motility determines transit time in different gi regions
41
how long does smooth muscle and gi motility in esophagus
7-10 seconds
42
how long does smooth muscle and gi motility
2-4 hours
43
how many hours does smooth muscle and gi motility small intestine
3-5 hours
44
how many hours does smooth muscle and gi motility in the colon
12-24 hours
45
what is the structure of the gi tract wall
muscularis externa
circular smooth muscle
longitudinal smooth muscle
muscularis muscosa
serosa
submucosa
lamina popria
lumen of gi tract
46
what is gi motility dependent on the interactions between
smooth muscle
autonomic nervous system
enteric nervous system
hormones
47
what is transmission of information along the gi smooth muscle referred to as
syncitial conduction
gap junctions
autonomic neuron varicosity
48
what is slow wave rhythm
basal electrical rhythm
generated by cells cajal
the frequency depends on the region
-stomach - 3 min in body
dudodenum 12/min
ileum 8/min
colon 3/min
propogation of slow waves generates
segmental and peristaltic conditions
49
how does control of gi motility work
autonomic/enteric nervous system
parasympathetic nervous system is dominant during digestive phase
excitatory enteric fibres (acetylcholine)
sympathetic nervous system
inhibitory effects (noreadrenaline)
activation of myenteric plexus exerts greatest influence on motility
hormones- gastrin, cck, motilin, glucagon like peptides
50
what are the three parts of the swallowing reflex
oval voluntary
pharyngeal (involuntary)
oesophageal (involuntary)
51
how does the oral voluntary reflex work
tongue pushes bolus against soft palate and back of mouth triggering swallowing reflex
52
how does the pharyngeal involuntary reflex work
upper esophageal sphincter relaxes while epiglottis closes to keep swallowed material out of the airways
53
how does oeseopheageal involuntary reflex work
food moves downwards into the esophagus propelled by peristaltic wavesand aided by gravity
54
explain the normal swallow
deglutination intiated by swallowing centres in the medulla
peristaltic waves pass down the oesophagus and last 7-10 seconds
lower esophageal sphincter relaxes to allow food to pass into stomach
55
what does the term achalasia mean
failure to relax
55
what are the symptoms of achalasia
difficulty swallowing
food sticks on the way down
solids worse than liquids
55
what are the causes of achalasia
unknown
56
what is the treatment of achalasia
physical distension of lower esophageal sphincter
surgical cutting of lower esophageal sphincter
57
how can achalasia be diagnosed
by barium swallow
58
what are the motor functions of the stomach
recieves food
stores food (volume empty -50ml full 2 litres)
breaks up food and mixes it up with gastric juice to form chyme
delivers chyme at a controlled rate into the dudodenum
59
what is the portal triad
hepatic portal vein
hepatic artery
bile duct
sits inside hepatodudodenal ligament on the edge of the lesser omentum
60
what is the proximal unit aided by
shape of the stomach
receptive relaxation-
vago-vagal inhibitory reflex
muscle fibres increase length without changing the tone
minimal increase in intragastric pressure
61
where do hunger pangs originate from
the body of the stomach
occurs after more than 8 hours of the stomach being empty
intense rhythmic peristaltic contractions
contractions may merge and last 2-3 minutes
maximum intensity after fasting for 3-4 days
62
what is the distal motor unit
compromised of the antrum and pyloric sphincter
63
what is the function of the distal motor unit
propulsion of chyme
mixing of chyme with gastric secretions
regulation of gastric emptying
64
what does gastric emptying depend on
composition of a meal
65
what does the stomach empty at a rate that is proportional to
the gastric volume
stomach empties on a rate proportional to gastric volume
66
how is gastric emptying regulated
by two phases gastric and intestinal
gastric phase- stimulation
intestinal phase- inhibition
67
explain the gastric phase of gastric emptying
distension of the stomach, presence of partially digested proteins, alcohol and caffeine in the stomach
increased generation of parasympathetic impulses in vagus nerves
stimulation of gastric emptying
contraction of lower eosphageal sphincter increased stomach motility
relaxation of pyloric sphincter (valve)
68
increased secretion of gastrin is paired with what increase in the gastric phase of gastric emptying
increased generation of parasympathetic impulses in vagus nerves
69
explain the intestinal phase of gastric emptying
1) distension of dudodenum presence of fatty acids, glucose and partially digested proteins in the dudodenum
increased secretion of cck
intiation of enterogastric reflex
inhibition of gastric emptying
decreased stomach motility
70
in the intestinal phase of gastric emptying, what is increased secretion of cck paired with
intitation of enterogastric reflex
71
what is the role of gastrin in gastric emptying
stimulates contraction of the antrum and increases constriction of pyloric sphincter- no impact on gastric emptying but enhances mixing
72
what is emesis
vomiting-forceful expulsion of upper gi contents
73
what can trigger emesis
certain smells or sights
touch receptors at the back of the throat
reflexes involving semi circular canals motion sickness
emotional factors
migraine
stimulation of the chemoreceptor trigger zone by circulating emetics
endocrine factors e.g hormones of pregnancy morning sickness
74
what is segmentation in terms of gi motility
mixing movements-
segmentation contraction
principally in the small intestine
12/min in dudodenum
8/min in jejunum and ileum
contraction of circular smooth muscle facilitates the mixing
segmentation lasts 5-6 seconds and occurs throughout the digestive period
no net forward movement
75
explain peristalsis
peristalsis is propulsive movements
throughout intestine
11-12/min in the colon
3-4/min in colon
waves of contraction and relaxation of circular and longitudinal smooth muscle facilitates propulsion
net forward movement of chyme at a rate of 1cm/min
76
how are peristalsis and both segmentation regulated
both movements are intitated by distension
require enteric nervous pathways
influenced by the autonomic nervous system
-increased by parasympathetic activity
reduced by sympathetic activity
influenced by some gi and other hormones
77
how does the migrating motor complex work
occurs during the interdigestive phase
initiated every 70-90 mins
passes from the stomach through the gi tract
takes 80-120 mins for one activity
77
what are two non digestive roles of intestinal motility
migrating motor complex-plays a house keeping role
the ileal brake reflex- prevents unabsorbed nutrients entering the colon
78
what is the significance of the migrating motor complex
mechanism for cleaning indigestible debris from the small intestine
plays a housekeeping role in preventing overgrowth of micro-organisms in the small intestine
78
how does chyme move into the cecum
controlled by the illocecal sphincter
under feedback control
pressure and chemical irritation relax sphincter and excite peristalsis
fluidity of contents promotes emptying
pressure of chemical irritation of cecum inhibits peristalsis and excites the ileocecal sphincter
exciting the ileocecal sphincter makes it contract and close
78
what are the regulators of the migrating motor complex
motilin-increases migrating motor complex
cck and gastrin- decrease migrating motor complex
79
how does chyme move into the cecum in short
ileal distension- sphincter relaxes- peristalsis- chyme moves into the cecum
cecum distension- sphincter excited, inhibits peristalsis and sphincter closes preventing backflow of chyme- defence against bacterial contamination
80
in depth explain how the chyme moves into the cecum
the movement of chyme into the cecum is controlled by the ileocecal sphincter through feedback mechanisms involving both chemical and pressure signals
distension of the ileum from chyme build up triggers peristalsis in the ileum and causes the ileocecal sphincter to relax allowing chyme to flow into the cecum
chemical stimuli such as presence of bile acids and undigested food in the ileum can promote sphincter relaxation and ileum emptying
fluidity of the contents also allows for emptying
once chyme enters the cecum, build up of chyme can cause cecum distension or chemical irritation (by bacterial build up) sends reflex signal to sphincter and sphincter is excited, contracts and closes to prevent backflow of colonic contents into small intestine (defence against bacterial contamination)
distension of chyme also inhibits ileal peristalsis through ileocecal reflex, slows down chyme movement into the colon
81
what is the ileal brake reflex
prevents unabsorbed nutrients from entering the colon
minimises unwanted chemical reactions between nutrients and gut microflora
mechanism- unabsorbed nutrients in the lower ileum delays
gastric emptying
jejunal transit
supresses hunger
GLP 1 hormone and peptide PYY
82
what are the movements of the colon like
normally quite sluggish around 5-10cm/ hour
transit time- 12-24 hours
83
what are the two types of movements of the colon
mixing (haustrations)
propulsive (peristalsis and mass movements)
84
what are mass movements of the colon (propulsive movements)
usually initiated by food intake
stomach and duodenal distension cck and gastrin
moves contents from sigmoid colon to rectum
85
what are colonic haustrations-
similar to segementation but more marked
bulding of the large intestine into baglike sacs because of circular and longitudinal muscle contractions
semi solid faeces are forced against the epithelium promoting electrolyte and water absorption
dependent on interaction between the enteric nervous system and smooth muscle
86
circular and longitudinal muscle are both innervated by the myenteric plexus and contribute to gi motility, how
circular muscle layer wraps around the gut like rings
when the circular muscle contracts the gut narrows (lumen constricts) squeezing the contents forward
its crucial for segmentation movements (mixing contents back and forth) and peristalsis (pushing food forward in waves)
key role of circular muscle is to propel and mix food by pushing it along or breaking it into smaller portions
the longitudinal muscle layer runs lengthwise along the gi tract
when it contracts the gut shortens pulling the tube ahead creating space for the bolus to move into
works closely with circular muscles during peristalsis by shortening the gut just before constriction of the circular muscles helping the food to move along
helps advance food down the tract by shortening and widening the gut movement
87
how does the defaecation reflex work
reflex occurs in response to sudden distension of the rectal wall
voluntary and involuntary process
88
what is the final phase of the defaecation reflex
abdominal muscles contract causing increased intra abdominal pressure
perineal wall is lowered and anorectal angle is decreased from 90 to 15
the internal and external anal sphincter relaxes along with the puborectalis muscle allows the faces to be passed
89
what is the correct way to sit on a toilet seat
squat
in order to maintain continence, the puborectalis muscle chokes the rectum, and the anorectal angle is obtuse . keeps rectum bent
squatting relaxes the puborectalis muscle allowing easier elimination the ano rectal angle when squatting is almost 180 degrees
90
what is step 1 of the vomiting reflex
1) stimulus of the vomiting centre
2) vomiting (emetic centre) coordinates reflex through cranial nerves x, ix, vii, v, xii
3) hypersalivation pallor, sweat, tachychardia
4) glottis closes- soft palate rises to close off airway
5) diaphragm contracts
6)gastroeosophageal sphincter and fundus of stomach relax
7) abdominal muscles contract forcefully
8) anti peristaltic waves
9) increased pressure forces chyme upwards through stomach and out of mouth
