Gastrointestinal Flashcards
1
Q
What are the functions of the large intestine?
A
- Microbial fermentation (CH) and protein)
- Water absorption and electrolyte balance
- Faeces production
2
Q
What is the arterial supply to the large intestine?
A
Cranial and caudal mesenteric artery
Coeliac artery to the prox duodenum
Pudendal artery to the caudal rectum
3
Q
What is the venous drainage from the large intestine?
A
usually supply the hepatic portal vein
Caudal rectum and anal region drain into the caudal vena cava
4
Q
What are sacculations?
A
Taeniae of longitudinal muscle can contract to form haustra
5
Q
Define haustra
A
sacculations between the taenia
dynamic not fixed
6
Q
Define taenia
A
Visible bands of smooth muscle and external elastic fibres
7
Q
Where does the ileum connect?
A
Joins between the caecum and the colon
In horses ileum -> caecum -> colon
8
Q
What are the 3 parts of the Large intestine?
A
Colon
Caecum
Rectum
9
Q
What innervates the large intestine?
A
Intramural ganglia form plexi at submucosa ( submucosal plexus) and between the smooth muscle layers (myenteric plexus)
Meissners plexi in the submucosa
Auerbachs plexi between the smooth muscle
ENS control
10
Q
How does the mucosa of the large intestine appear histologically?
A
Thinner than the small intestine
No villi or microvilli
Crypts deeper down than in the SI
mucous glands are long and straight
Goblet cells (most in rectum least in caecum)
11
Q
What are the tunics of the large intestine?
A
Tunica mucosa
Tunica submucosa
Tunica muscularis
Tunica serosa
12
Q
What is found within the mucosa of the large intestine?
A
Epithelium
Peyers patches
Lamina propria
Muscularis mucosa
13
Q
Which animal is the appendix most well developed in?
A
Hind gut fermenters
Appendix = narrow extension at the tip of the caecum
14
Q
What does the caecum comminicate with?
A
Ileum via ileocaecal orifice
Colon vi caecocolic orifice
15
Q
What is the role of the caecum
A
Microbial digestion of cellulose
Absorption of water and electrolytes
Source of bacteria
16
Q
Describe the equine caecum
A
Large capacity with 4 taenia
has a base, body and a blind ending appendix
17
Q
Describe the caecum in the pig
A
3 taenia
cylindrical and blind ending
Left side of abdomen
18
Q
Describe the caecum in the dog
A
Spiralled
19
Q
Describe the caecum in cats
A
comma shaped
20
Q
Describe the caecum in the ruminant
A
No taenia
No haustra
Relatively small
21
Q
Why do horses require caecal valves?
A
Because ileum empties directly into the caecum
Ileocaecal valve
Caecocolic valve
Separated by a raised fold of mucosa
22
Q
Where is the GALT found?
A
Submucosa and mucosa
23
Q
Describe the colon in dogs
A
Ascending
Transverse
descending
24
Q
Describe the colon in ruminants
A
Long ascending w 2 sigmoid flexures and double spiral
Short transverse and straight descending with a sigmoid flexure at the end
25
Describe the colon in pigs
Cone shaped w coiled ascending
Base is attached to left abdominal
apex points ventrally
2 taenia and 2 rows of sacculations
26
Describe the colon in horses
Large ascending ( right vent-> left vet-> left dorsal-> right dorsal)
Short transverse and large descending
right dorsal is spot for impactions
27
What are the exocrine components of the stomach?
Mucin producing cells
Parietal cells
chief cells
28
What are the 3 muscle layers of the stomach?
Oblique muscle
Longitudinal muscle
Circular muscle
29
What are the endocrine components of the stomach?
ECL cells
Gastrin producing cells
30
Outline the neural stimulation of the stomach in secretion (long reflex)
LONG REFLEX
Expansion of stomach -> sensory nerve endings -> CNS impulse via vagal nerve = acetylcholine release from submucosal plexus
= stomach secretion
31
Describe the hormonal stimulation of the stomach
SHORT REFLEX
Stomach expansion = peptide release = gastrin release
Sensory nerve endings send impulse to stomach via vagal nerve releasing acetylcholine
32
What cells is responsible for stomach emptying?
Cajal cells
33
What is the process of regulating contraction in the stomach?
Food = homeostatic change
inc gastric pH + wall distension
Stretch stims mechanoreceptors = influx into submucosal plexus
PNS nerve influx to stomach affectors via parietal cells
Evacuation of food in the stomach
34
What are the phases of degluttination?
Oral phase
Bolus -> pharynx as tongue thickens
Pharyngeal phase
food -> oes when mechanoreceptors in pharynx wall send afferent to brain -> efferent to tongue
Reduction in pharynx vol= inc in pressure pushes food
Oesophageal phase
The peristaltic movement pushes food to stomach
35
What is large intestine contraction stimulated by?
Stomach and the duodenum long reflex arc via the mesenteric nervous system
36
How is appetite controlled?
Modulating signal are read in the satiety centre which leads to feeding behaviours
37
What are the movements of the small intestine?
Segmentation
Peristaltic waves
Antiperistaltic waves
Mass movement
Driven by stretch measures by the mesenteric plexus and CNS/PNS
38
How is pancreatic juice and bile increased?
Vagal activity leads to HCl and pepsinogen production and pancreatic juice and bile excretion
Food enters stomach = stretch = long and short reflex leading to gastrin and histamine
Increase in pancreatic juice production and bile
Chyme enters the duodenum decreasing pH, proteins and fatty acids leading to CCK and secretin release
Increases pancreatic juice and bile as stomach empties
39
What factors affect stomach emptying?
Inhibited by duodenal factors stimulating SYMP fibres =
Secretin release, gastric inhibiting peptide and cholecystokinin (CCK)
40
What is the biological mechanism for ion exchange across the smooth muscle membrane?
Depolarisation of membrane = neurotransmitter release
L-type voltage-gated channels open so Ca+ induced Ca+ release from the sarcoplasmic reticulum
Increases intracellular Ca+ and Ca+ binds to calmodulin
Myosin light chain kinase action and phosphorylation
Increase in MLC ATPase activity
Myosin-P binds to actin forming cross bridge = muscle tone
41
Compare smooth and skeletal muscle
Smooth = no sarcomeres
Skeletal= stimulated by acetylcholine from motor neurones
Smooth and cardiac = use gap junctions to transmit signals for coordinated contraction
42
Compare the membranous and luminal phases of digestion
mem- Enzymes bound to surface
relies on the brush border for transport of the digested products
Luminal- free enzyme
Hydrolyses and solubilised CHO, proteins and lipids by enzymes and bile
43
Define Secretory diarrhoea
Increase in active secretion or inhibition in the absorption
No structural damage
44
Define osmotic diarrhoea
Too much water taken into the bowels
45
Define Motility related diarrhoea
Rapid movement of food through the intestine
46
Define inflammatory diarrhoea
Damage to the lining of the intestine = loss of protein rich fluid and decrease in the ability to absorb
47
Outline the digestive physiology of rabbits
Proximal colon separating ingesta
Two types of faecal pellets (large= indigestible to colon) (small= retrograde to caecum for microbial fermentation= caecotrophs)
48
What is the role of the proximal colon and the ampulla coli together?
Location of mixing and separating ingesta
Large particles continue to the colon
49
What is the role of the appendix in the rabbit?
Secretes bicarbonate ions
Buffering role for volatile fatty acids
50
What are haustra in the rabbit?
Outpouchigns along the proximal colon
Increase SA and separate ingesta
51
What is the role Warzen? §
Increase SA ( small protrusions in rabbits)
52
Compare the internal anatomy of the proximal colon and the distal colon in rabbits.
In proximal colon there are 3 taeniae, haustra and warzen will be seen
53
What is the role of the fusus coli?
Mucous producing and highly muscular found towards the distal end of the proximal colon in rabbits
54
What drives caecal fermentation in rabbits?
Bacteria, protozoa and yeast
Most common is Bacteriodes spp
55
What are the products of caecal fermentation in rabbits?
VFAs
Amino acids
Water soluble vitamins
56
What can change the pH of a rabbit caecum?
Changes diurnally
Volatile fatty acids
Ammonia
Bicarb ions from the appendix buffer
57
How do the contents in the rabbit GI separate?
Large indigestible products-> lumen of prox colon -> distal colon -> anus
Small digestible particles-> collect in the haustra of prox colon-> retrograde peristaltic movements push back to the caecum
58
What is the name of the T section where the rabbit ingesta is separated?
Ampulla coli
59
What are the faecal production phases for rabbits?
Hard faeces = fusus coli contracts to squuez out water with mucous production
Soft faces = rest
60
Motility in the soft faeces phase in rabbits?
Caecum and prox colon motility ddecreases
distal colon increases
Fusus coli adds mucous but does not squeeze out the water
61
What are the properties of a caecotroph?
Outer greenish membrane
Proein> fibre
Protein from fermentation or bacteria
Undigested nutrients
Vitamin B and K
62
Where is lysosome added to caecotrophs and why?
Added in distal colon to digest bacterial cell walls allowing rabbits to utilise the proteins from the bacteria
63
What is the pacemaker of rabbits large intestine?
Fusus coli
Initiates peristaltic waves in the colon as it is highly innervated and has hormonal influence from aldosterone and prostaglandins
64
How does diet affect rabbits gut motility?
Fibre increases and acts as buffer
Fat increases motility
Protein decreases caecotrophs
Carbs form bacteria like C spiroform and E coli by inc glucose therefore inc VFAs
High fibre high fat pos
High protein High carb negative
65
What is the palatal ostium?
Found in guineapigs and chinchillas
soft palate is continous with the tongue so the palatal ostium is a hole/opening in the membrane
CLIN SIG - damage in intubation
66
Describe the chinchilla GI tract
Large coiled caecum
Sacculated colon
Caecotrophs produced
67
Describe the cheek pouches of hamster
Thin walled highly distensible
Immunologically privileged
Pre gastric fermentation
68
Describe ferret GI tract
Simple stomach
short intestine
No caecum or appendix
simple GI flora
10cm large intestine
Short GI tract so need high quality food 30-40% protein Fats> carbs fats = 15-20%
69
Approach to horse with colic:
History
Physical exam
Diagnostic techniques
- rectal palp
- nasogastric intubation
- abdo paracentesis
70
What are the issues with equien grazing diets?
Grass contains silicates - harder than enamel so damage teeth
Cellulose and hemicellulose cannot be digested - microbial digestion only
71
How do horses use different teeth
Lips and incisors - grasp/prehend food
Rigid molars - grinding
Irregular molar surface is better for grinding
Rotational chewing movement
72
What are the main properties of the equine stomach?
2 types of mucosa - squamous and glandular epithelium
5-15 litre capacity
cardiac sphincter and pyloric sphincter
food is held in stomach for short period of time
73
What are the properties of the equine small intestine?
10-30cm long
duodenum, jejunum and ileum - loosely coiled
Mesenteric attachment - no fixed poisition
Digestion
- Carbohydrate: Starch -> glucose and galactose
- Protein: Oligopeptides ->dipeptides, tripeptides and amino acids
- Fat: triglycerides -> fatty acids, monoglycerides
74
How are fructans digested in the horse?
Pass into large intestine and digested by bacteria = acidic env alters the large intestinal flora
75
Describe the equine caecum
Microbial digestion, water + electrolytes
Blind ending sac w two muscular valves
Pacemaker region
76
Describe the equine large colon?
Made up of right and left ventral colon and right and left dorsal colon
77
Role of the equine small colon?
Storage of faeces and absorption of remaining water
78
What can be palpated on the left and right hemisphere of the equine abdomen per rectum
L
Spleen
caudal pole of left kidney
Pelvic flexure
Small colon
R
Caecum
79
What can be analysed from an equine peritoneal tap?
Colour
volume
turbidity
Total protein
cell no. and type
80
What are the components of the extracellular fluid?
Plasma
Lymph
Interstitial GI fluid
Synovial, peritoneal and pleural fluid
81
What are the percentages for ECF and ICF?
ICF= 30-40%
ECF= 20-40%
82
How is blood volume calculated
90-100ml per kg
83
Where is most of the water absorbed in the GI tract?
Proximal small intestine is secretion
Small and large intestine is absorption
Dogs/cats = LI
Ruminant = omasum
Horse= small colon
rabbit = distal colon
84
What is the major site of digestion in dogs and cats?
Small intestine
85
What is the major site of digestion in the ruminant?
Rumen
86
What is the major site of digestion in the horse?
Caecum
And rabbit
87
What is the muscular layer of the small intestine made of?
Outer most layer composed of elastic fibres and smooth muscle cells in circular and longitudinal arrangement
88
Define chyme
Acidic fluid made up of gastric juices and partly digested food
89
Define peristalsis
Involuntary constriction and relaxation of muscles creating wave like motion pushing contents forward
90
Define segmentation
Rhythmic contraction of circular muscles that divides and mixes chyme - mixes food w gastric juices and breaks it down further
91
Define mass movement
Large waves of motility
92
Where are interstitial cells of cajal found?
Found in circular muscle of intestine
93
Compar sacculations in rabbits and horses
In horses they increase SA
In rabbits they are used to collect smaller particles
94
What are the main types of motility in the caecum and the colon?
Haustral contractions and mass movemnt in colon
Caecum have segmentation contractions for mixing
95
What are the sites of the pelvic, sternal and diaphragmatic flexures?
Sternal = RVC- LVC
Pelvic = LVC and LDC
Diaphragmatic = LDC-RDC
96
What is the affect of para and sympathetic stimulation on the gut motility?
Symp decreases
Para increases
97
How is the rectum emptied?
Mass movement of LI fills the rectum = stim pressure sensitive cells
Defecation reflex = forceful contraction of rectum and relaxation of internal anal sphincter
= conscious sensation to empty bowel
98
Which species have voluntary control over emptying rectum?
Carnivores
Ruminants = no control
99
What part of the crypt villus unit digests and absorbs nutrients?
Mature enterocytes on the villi tips
Absorb
CHO
AA
Lipids
Minerals water ions
100
What is the role of the crypts of lieberkuhn?
Produce immature enterocytes and other gut cells from stem cells
101
What is the brush border of the small intestine?
Has a thick mucous layer of microvilli
mature enterocytes are bound to the cell membrane to breakdown nutrients
102
How are small intestine epithelial cells regenerated?
There is renewal and regenerative process driven by intestinal stel cells which reside at the base of the crypts (crypts of lieberkuhn)
3 of the 4 cells migrate up the villus
103
What are the cells of the crypt villus units?
Enterocyte - enzymes and absorption
Enteroendocrine- hormones
Goblet - mucous
Paneth cells = lysosome inhibits bacteria
104
How are goblet cells adapted for mucous secretion?
Lots of ER - protein synthesis and folding
Golgi apparatus- modification and transport
Secretory granules on apical surface- delivery of excretions
Microvili on apical side- increase SA
Can absort soluble antigens from intestinal lumen and deliver to subepithelial dendritic cells
105
What stem cells to goblet cells arise from?
Pluripotent stem cells
found in bone marrow, blood and adipose tissue
106
What is the goblet cell response to inflammation?
Inc production of mucin = more mucous for protection
107
What feedback mechanism operates for the crypt to reform damaged villus?
Homeostatic feedback
positive feedback
108
What does high levels of radiation target?
Genetic material
109
What are the 3 sections of the small intestine?
Ileum
Jejunum
Duodenum
110
What is the blood supply to the ileum?
anitmesenteric and mesenteric
111
Describe the submucosa of the small intestine?
Structural support, BV, nerves, and lymphatics
fine smooth musc layer projects into the lamina propria = alters mucosal folding and pumps villi up and down
112
What are the properties of the mucosa of the small intestine?
Epithelial cell layer = functional
Lamina propria= loos connective tissue and immune cells (presence of crypts of lieberkuhn)
113
What will the affects of hyper and hypomotile muscularis in the small intestine?
Hypermotile segmented contractions = delay passage
Hypomotile segemented contractions = increase passagfe
ileus= lack of motility and bacterial overgrowth
114
What is responsible for the mixing motion in the SI?
Tunica muscularis
115
Describe the blood capillaries of the crypt villus units?
In lamina propria
Large fenestrations = plasma proteins can move into interstitial space
116
What are lacteals in the crypt villus units?
Blind ending lymphatic capillaries that transport emulsified fats (chylomicrons) for lymphatic drainage -> cranial vena cava
117
What is the venous drainage of the small intestine?
Hepaticoportal vein
118
What shape is the duodenum>
U shape
Short mesentery
Sheep and goats = desc limb
Primates = both
Horses, pigs cattle= extend into the jejunum
119
Where is the ileum connected?
Caudal jejunum to the ileum to the caecum
Ileum -> caecum = ileocaecal fold (contains BV)
120
What are the 5 cell types in the small intestine?
Enterocytes
Enteroendocrine
Goblet cells
Paneth cells
M cells
121
What is the cell escalator process in the small intestine?
High energy defence mechanism
Rapidly dividing stem cells in the crypts of lieberkuhn are sent up the villus
Sloughing of cells at the tip
There is crypt neck differentiation
Takes 3-5 days to reach top
122
What happens during crypt neck differentiation?
Stem cell zone
3 of the 5 cells are migrated up the villi
Paneth cells migrate down
M cells source is uinclear but they cover the peyers patches
123
How does the secretory function of the duodenum create the correct environment?
Serous contains bicarb
Mucous = protection
124
How does parvovirus infect as a secondary intestinal infection?
Virus infects and damages epithelial cells
cellular replication using crypts villus occurs
Parvovirus has affinity for rapidly dividing cells = more severe parvovirus infection
Dual infection = acute enteritis with severe symptoms and high mortality
125
What is the structure and function of the enterocytes?
Columnar epithelial cells w microvilli
Smooth ER for transport of nutrients
Pinocytosis for vesicles
Protective function
Tight junctions between enterocytes
126
What is the structure and function of the enteroendocrine cells?
Scattered along GI
Closed and open types
20 different hormones produced
Islet of langerhans cells are EECs
127
What are the paneth cells?
Apical granules with innate mucosal defences (defensins and lysosome) at the bottom of the crypts
Only present in horses and cattle
128
What are M cells?
Specialised epithelial cells that cover peyers patches
Single layer of cells and no mucous layer
Microfold on apical surface and indentation on basal surface for lymphocytes and macrophages
Transport antigen from the lumen to the immune cells
129
What are the properties of the peyers patches in the GIT?
Raised ovoid areas in the mucosa of the distal small intestine.
1-2 cm diameter
in antimesenteric mucosa
Reactive to changes in the gut flora = immune response
130
Describe the lymphoid follicles in the GIT
Aggregations of lymphocytes and macrophages within the lamina propria
No contact with lumen unlike the peyers patches
131
Where are the lymph nodes in the GIT?
Within the mesentery
At different levels according to the species (near the gut or near the root)
132
What is the structure and function of the pancreas in the dog?
Two lobes in duodenal flexure
Exocrine function for digestive enzymes and alkaline fluids
Endocrin function - insulin, glucagon, somatostatins and pancreatic polypeptide
133
Where is the pancreas ?
Part of pancreas is always between the descending and ascending limbs of the duodenum
134
What is responsible for pancreatic stimulation?
Duodenal enteroendocrine cells = sense acid
Secretin release acts on the pancreas ducts
Epi cells in pancreas= bicarb + water
flushes acinar enzymes into the small intestine lumen
135
What blood vessels supply to small intestine and the pancreas?
Coeliac artery - left gastric, hepatic and splenic
Cranial and caudal mesenteric
136
Where is meissners plexus and auerbachs plexus?
Meissners = submucosa
Auerbachs= Between smooth muscle layers
137
What are the parasympathetic pathways to the GIT?
Vagus nerve -> dorsal vagal trunk -> coeliac and mesenteric gel-> blood vessels-> gut
Sacral part of PNS- Pelvic nerve forms retroperitoneal plexus = descending colon and rectum
138
How is TAG formed?
Triacylglycerol is formed by condensation reaction between glycerol ester and 3 fatty acids
139
How are lipids digested?
Large drop is reduced by bile acids/bile salts
CCK = bile secretion
Phospholipase A2 in pancreas, Lecithin-> lysophospholipids = strong detergent
140
How is the accumulation of lipids in the intestinal epithelium targeted?
Fat components in reticulum so TAG molecules reformed
Con gradient allows for passive absorption into enterocytes
Gradient is maintained by an intracellular fatty acid binding protein
141
What are the roles of lingual and pancreatic lipase?
Lingual lipase generates nonesterified fatty acids (NEFA) from dietary fats during oral processing by lipolysis
Pancreatic lipase catalyses the hydrolysis of triacyglycerols at positions 1 & 3 forming 1,2 diacylglycerol and then 2 monoacylglycerol
142
What is the structure of chylomicrons?
Lipoprotein with Outer skin made of amphipathic phospholipids, cholesterol and protein
TAG and cholesterol esters are carried in the core
Chylomicrons leave the cell via exocytosis into the lymphatic circulation
143
What are the role of chylomicrons?
Apoprotein in the surface activates lipoprotein lipase to attache to the luminal surface of small blood vessels
Lipase catalyses hydrolytic cleavage of fatty acids from TAG and chylomicrons
released FA and MAG are used for energy
144
What are the classifications for chylomicrons?
Chylomicron
VLDL
IDL
LDL
HDL
145
Define pica
A compulsive disorder where an organism eats something it wouldnt usually eat
146
What is EPI?
Exocrine pancreatic insufficiency
Lack of pancreatic enzymes reduce the absorption of nutrients from the food
147
What are oligosaccharides?
Formed from between 309 monosaccharides
148
What is hemicellulose composed of?
xylose
Glucose
Mannose
Arabinose
149
How are carbs digested?
Salivary alpha amylase = maltose, glucose and dextrin
Luminal phase = pancreatic amylase = maltose
Membranous phase = glucosidase enzymes = disaccharides to monosaccharides in brush border
Limiting glucose and maltose absorption is epithelial transport
150
What limits the rate of lactose uptake?
Rate of hydrolysis
151
What is the function of the pancreas?
Secretes zymogens to aid protein digestion
Beta cells = insulin
Alpha cells = glycogen
Delta cells = somatostatin
Acini cells = Digestive enzymes
152
What zymogens are released by the exocrine pancreas?
Trypsinogen
Chymotrypsinogen
proelastase
Procaboxpepitidase
There is a cascade of the zymogens starting with trypsinogen being cleaved into trypsin by enteropeptidase
153
Define protease
Enzyme that carries our proteolysis
154
What are the 6 groups of proteases?
Serine protease
Threonine protease
Cysteine protease
Aspartic acid protease
Metalloproteases
Glutamic acid proteases
155
Define exopeptidase?
Detach terminal amino acids from polypeptide
on membrane of small intestine only
156
Define endopeptidase
Hydrolyse internal peptide bonds of a protein
157
What is the action of serine endopeptidases?
Synthesised by panc acinar cells secreted into small intestine
Chymotrypsin = cleaves bonds following large hydrophobic aa residue
Trypsin= cleaves bonds after +vely changed aa residue
Elastase = cleaves bonds after small neutral aa residue (alanine etc)
158
What are aminopeptidases?
Attack aa terminal of peptides secreted form the small intestine
Considered exopeptidases
159
What are the phases of protein digestion?
Luminal - non specific
non specific proteases hydrolyse protein to short chain poly p
Membranous-
Hydrolysed further to di/tripeptides and some free aa
Specific membrane proteins transport across gut wall by secondary active transport
160
What are the 2 dominant routes for amino acid transport?
1. Peptide transported with high affinity for tri/dipeptides
Peptides w L amino acids are driven by electrochemical gradient by Na pump
2. Single aa transport from lumen using sodium and a carrier mediated co transport system
161
What are the neurotransmitters and substances involve in the ENS?
Acetyl choline
Noreinephrine
Seratonin (5-H)
Purines
Nitric oxide
162
Which fibres terminate in the plexus of the gut?
Sympathetic
163
What is the endocrine and paracrine control of the GIT?
Endocrine- gastrin and CCK (peptides from mucosa)
Paracrine- Local regulatory peptides such as histamine
164
Which parts of the GI tranct can be modified pharmacologically>
Gastric secretion
Mucosal protection
Emesis
Motility
Inflammation
Foam formation
Digestion
165
How can gastric secretions be modified?
Local prostaglandins control secretion of mucus and bicarb
modifications (neutralisation, mucosal protection , absorbents)
166
Drugs for neutralisation of gastric secretion?
Magnesium hydroxides and trisilicate
Aluminium hydroxide gel
Algniates and simeticone
167
Drug for mucosal protection of the GI tract
Sucralfate- can prevent uptake of other drugs
168
What are the properties of the drugs used as absorbents in the GI tract?
usually have coating actions that bind to bacteria and toxins
Protect lining of stomach from excess acid
169
What cells on the lumen side of the stomach pump out H+
Parietal cells
170
What receptors is the production of HCl in the stomach dependent on? How does this help drug use?
Muscarinic receptors
Histamine 2 receptors
Gastrin receptors
To decrease HCl production just block any of these receptors
171
Acetyl choline antagonist?
Atropine
Not a selective drug so can affect other areas
172
What is the best target for stopping HCl production in gastric secretion?
Proton pump inhibitors
173
Regulatory process that maintains homeostasis in stomach and reduced production of HCl
Production of Prostaglandin E2
Binds to receptor on parietal cell to reduce HCl production
174
What are prostaglandins produced from?
Arachidonic acid
175
Main proton pump inhibitors
Omprazole
Lasoprazole
176
How do histamine antagonists affect gastric secretion?
Inhibit gastrin, histamine and acetylcholine stimulated by secretion
Pepsin secretion falls
177
Histamine antagonists
Ranitidine
Cimetidine
178
Action of cimetidine
Inhibits cytochrome P450 and slows metabolism
179
How does misoprostol modify gastric secretion?
Stable analogue of PGE1
Inhibits acid sec
increase mucosal blood flow
increases uterine contraction
180
What are the emesis centres?
Chemoreceptor trigger zone
Vomiting centre in the brainstem
181
What does the chemoreceptor trigger zone respond to for emesis?
Relies on chemical stimuli
BBB is permeable in CRTZ
Motion sickness there is input from the vestibular apparatus
Impulses are sent to vomiting centre
182
Vomiting centre in the brainstem?
coordinates and integrates vomiting
183
What is the pathophysiology of vomiting?
Nerve impulses -> emetic centre from central or peripheral-> converge together
Substance P binds to NK-1 receptors = signal to vagus nerve and abdo musc and diaphragm
184
What receptors are involved in vomiting?
Substance P = neurotransmitter
NK-1 receptor found on cell membranes in vomiting centre
`Correct ligand to NK-1 rec= conformational change
185
Pharmacological emetics?
Apomorphine- dopamine agonist (IV or mucosal)
Alpha 2 agonists - Xylazine
Syrup of Ipecac - Direct irritant
186
What are the 2 main groups of dopamine antagonists?
Phenothiazine derivatives - centrally acting dopamine antagonists
Metaclopramide and domperidone - short action
187
What type of drug is chlorpromazine?
Dopamine antagonist
Phenothiazine derivative
188
The action metraclopramide and domperidone together in dopamine antagonism
Metra- mainly works centrally
Domperidone works peripherally
Increase gastric emptying and motility
189
How does Cerenia act as an anti emetic?
NK-1 antagonist
Competes with substance P
Completely shuts down final step of vomitings
Specifically designed for dogs
190
What clinical signs may require modification of intestinal motility>
Diarrhoea
Colic and stress
191
What aspects of SI motility are modified?
increase or decrease transit time = affects water absorption
Reduced pain
192
What are the common spasmolytic antimotility drugs and how do they work?
Opiates
Muscarinic antagonism
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Main opiates to treat diarrhoea
Morphine
Codeine
Loperamide (imodium) - doesnt cross BBB so no psychoactive effects
194
How can muscarinic antagonists act as antimotile drugs for GI tract?
Motility is under neuronal control
Inhibit acetylcholine stimulatory effects from the vagus nerve
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What are the different types of laxatives?
Saline and hyperosmotic agents
Bulk producing agents
Irritants
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Bulk laxatives
methylcellulose
Agar bran
- Not easily digested so hold water in gut = promotion of peristalsis
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Osmotic laxative
Lactulase
Broken down in GI to lactic acid
Alters pH more acid
Traps ammonia and therefore water
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What receptors do prokinetics act on for gut motility?
Seretenergic 5-HT receptor agonist
Cisapride
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When are anti inflammatories used in GI?
Idopathic inflammatory bowel disease
- Steroid= predisnolone
- Sulphasalazine - pro drug converted to salicylic acid in gut
200
When are antifoaming agents used?
Treatment of frothy bloat in ruminants
- Surfactants which cause bubbles to break down
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What is the rectum?
Terminal part of the large bowel
Arbitarialy delineated
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What are the histological layers of the rectum?
Mucosa - columnar epi, lots of goblets, lymphoid nodules
Submuc
Muscularis
Serosa
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Describe the organisation of the rectum muscularis muscle fibres
Stratum longitudinale - fibres dorso caudally = RECTOCOCCYGEYS MUSC
Stratum circulare = caudally = INTERNAL ANAL SPHINCTER MUSCLE
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Where is the caudal rectum and anal canal in relation to caudal peritoneum?
Retroperitoneally
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Describe the mesorectum
Extension of the mesocolon
Wider cranially
Tapers away with the serosal layer at 2 coccygeal vertebrae
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What is the blood supply to the rectum?
Caudal mesenteric
Left colic
Cranial rectal
Internal pudendal-> caudal rectal and middle rectal arteries
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Venous drainage from the rectum?
Cranial rectal-> caudal mesenteric-> hepatic portal vein
Middle rectal + caudal rectal-> internal pudendal vein -> internal iliac
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What is the anus
Specialised junction between mucosa and integumentary
Surrounded by smooth and striated muscle sphincters
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What are the 3 anal zones
Columnar
Intermediate
Cutaneous
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Properties of the cutaneous anal zone
Hairless skin
Squamous stratified epi
Ext and int components
Anal sac ducts open in this region
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WHat are the properties of the intermediate anal zone?
Narroe mid section
Transition from columnar- skin epi
1 mm wide
Anocutaneous margin
Stratified columnar cells
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What are the properties of the columnar anal zone?
Series of longitudinal ridges
Folds= anal sinuses
Prox = anorectal junction
Lined with columnar epi
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What is the internal sphinter and external sphincter made of?
Internal= smooth musc from circular layer
External = skeletal muscle
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What is the role of the anal sphincters?
Covers anal sacs in Dogs and cats = compresses during defacaetion
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Innervation of the internal anal sphincter?
Autonomic
PNS via pelvic and hypogastric plexuses
SNS via hypogastric via caud mesenteric ganglion
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What is the innervation of the external anal sphincter?
Somatic control
Innervated bilaterally by the anal branch of the pudendal nerve
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What is the defaecation reflex?
Feaces-> rectum = stretch receptors= faeces into descending colon and rectum
Tension crosses threshold so receptors transmit signal along afferent -> spinal cord
Spinal reflex = PNS motor contraction of rectum and sigmoid colon + relaxation of internal sphincter
Voluntary motor neurones inhibited allowing external sphincter to relax
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What is the gastro colic reflex?>
Causes onward passage of facecal material from colon to rectum
= anorectal reflex
219
What is colitis and what are the main clinical signs?
Irritation of rectum causes repeat attempts to defaecate with no faeces presetn
220
What supports the rectum?
Pelvic diaphragm
Group of muscles
221
What does rectal function rely on during defaecation?
Calais of the pelvic diaphragm muscles to compress the pelvic contents
222
What are the major muscles of the pelvic diaphragm?
Coccygeus muscle
Levator ani
223
Origin and insertion of levator ani
Origin - medial ilium and pelvic symphysis
Inserts on tendons to caudal vertebrae 3 to 7
Innervated by branches of the sacral plexus and pudendal nerve
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What is the insertion and origin of the coccygeus muscle
Originates at the ischiatic spine
Inserts on the transverse processes of caudal vertebrae 2 - 4
225
3 groups of perianal glands
Anal glands
Circumanal glands
Anal sacs have secretory epi lining
226
What anal glands are present in dogs and cats and where are they located?
ANal glands - cranial to the anocutaneous line = fatty secretion
Scattered apocrine glands around anus in cutaneous zone = caudal to anocutaneous line
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Where are the circumanal glands located in the dog?
around anus and cutaneous zone for water proofing
Sebaceous glands
228
Describe the anal sacs
Paired diverticula present in carnivores
In submucosa - lined by apocrine and paranal sinus glands
Open into the anal canal
prone to occlusion
229
Where are the anal sacs located?
Pea - bean size
Either side of anal opening at 4 and 8 oclock
Embedded between internal and external anal sphincter muscs
230
What are the properties of the anal glands within the anal sacs?
within the wall of the sacs
Coiled apocrine tubules
cornified stratified epithelium
Secrete foul smelling secretion
231
What is anal furunculosis?
Immune mediated fistula occurs
seen in combination with anal sac abscessation
Causes deep pyoderma
232
What are hepatoid adenomas?
Testosterone dependent benign masses
found in ext region of outer cutaneous zone
233
How can rectal prolapses occur?
endoparasites in young
Tumours or perineal hernias in older
Incomplete prolapse of mucosa
Complete prolapse of entire rectal wall
Can be mm to cm
Everted tisses is oedematous excoriated and can bleed
234
How does a perineal hernia occur?
Degeneration of pelvic diaphragm
Anal sphincter and levator ani separate
Or levator ani and coccygeus musc separate
235
Define atrestia
Absence or abnormal narrowing of an opening or passage in the body
236
Define hernia
Internal part of the body pushes out through a weakness in the muscle or surrounding tissue wall
237
Define atresia ani
Developmental defect of the anal opening or terminal rectum
238
Define faecaloma
Mass of faeces noted in rectum or colon
239
Define steonsis
Abnormal narrowing or passage in the body
240
Define tenesmus
Continual or recurrent inclination to evacuate the bowels = caused by rectum disorder
241
Define reducible hernia
Hernia with bulge that flattens out when you lied down or push against in gently
242
Define imperforate
Lacking normal opening
243
Define rectovaginal fistula
Communication between dorsal wall of vagina and ventral portion of rectum
vulva functions as common opening for uro tract and GIT
244
Define fistula
Abnormal connection between two body parts such as an organ or a blood vessel
245
Where is the inguinal canal located?
Internal oblique musc on one side of the pelvic tendon of the external oblique aponeurosis on the other side
246
What passes through the inguinal canal in males shortly after birth?
Testes
247
What is cryptorchidism?
Retention of testes
Failure to pass through the inguinal canal
248
What anatomical structures are present in the inguinal canal in females?
Round ligament
Genital branch of genitofemoral nerve
Iliolingual nerve
249
What anatomical structures are present in the inguinal canal in males?
Spermatic cord with the genital branch of the genitofemoral nerve and the iliolingual nerve
250
Type 1 atresia ani
Congenital stenosis of patent anus
251
Type 2 atresia ani
Persistence of complete anal membrane alone or a combination of anal membrane with rectum ending as blind pouch to cranial membrane
252
Type 3 atresia ani
Imperforate anus with rectum terminating further cranially
253
Type 4 atresia ani
normal ending of terminal rectum and anus
Cranial rectum terminates as a blind pouch within the pelvis
254
Atresia coli
Incomplete large bowel or colon
255
Inguinal or scrotal hernia?
indirectly herniated organs pass along the tunica vaginalis to the level of the scrotum
256
Umbilical hernia
Incomplete closure of the umbilical ring after birth
257
Diaphragmatic hernia
Hole in the diaphragm means that organs in the abdomen can move upwards into the thorax
258
Which structures can be examined on a small animal rectal exam?
anus, rectal wall, anal glands, reproductive tract, urethra, pelvis, and lymph node
259
emetic agents
Apomorphine
Alpha 2 agonists
Sgruposle
260
Antiemetics
Phenothiazone derivatives
Metaclopramide
Domperidone cerenia
261
What drugs can be used as spasmolytics
Opiates
muscarining antagnosts
262
What are the 3 classes of laxatives?
Bulk
Osmotic
Prokinetics
263
What centres control vomiting
chemo receptors trigger zone which is affected by chemical stimuli the blood brain barrier is permeable in this area. Impulses pass to the vomiting centre in brain stem coordinates and integrates vomitting
264
What is the pathophysiology of vomiting?
pathways can be central or peripheral
substance P is the neurotransmitter which binds to NK-1 receptors at the cell membrane
