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Veterinary medicine year 2 > Gastrointestinal > Flashcards

Gastrointestinal Flashcards

1
Q

What are the functions of the large intestine?

A
  1. Microbial fermentation (CH) and protein)
  2. Water absorption and electrolyte balance
  3. Faeces production
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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

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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

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4
Q

What are sacculations?

A

Taeniae of longitudinal muscle can contract to form haustra

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5
Q

Define haustra

A

sacculations between the taenia
dynamic not fixed

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6
Q

Define taenia

A

Visible bands of smooth muscle and external elastic fibres

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7
Q

Where does the ileum connect?

A

Joins between the caecum and the colon

In horses ileum -> caecum -> colon

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8
Q

What are the 3 parts of the Large intestine?

A

Colon
Caecum
Rectum

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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

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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)

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11
Q

What are the tunics of the large intestine?

A

Tunica mucosa
Tunica submucosa
Tunica muscularis
Tunica serosa

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12
Q

What is found within the mucosa of the large intestine?

A

Epithelium
Peyers patches
Lamina propria
Muscularis mucosa

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13
Q

Which animal is the appendix most well developed in?

A

Hind gut fermenters
Appendix = narrow extension at the tip of the caecum

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14
Q

What does the caecum comminicate with?

A

Ileum via ileocaecal orifice
Colon vi caecocolic orifice

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15
Q

What is the role of the caecum

A

Microbial digestion of cellulose
Absorption of water and electrolytes
Source of bacteria

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16
Q

Describe the equine caecum

A

Large capacity with 4 taenia
has a base, body and a blind ending appendix

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17
Q

Describe the caecum in the pig

A

3 taenia
cylindrical and blind ending
Left side of abdomen

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18
Q

Describe the caecum in the dog

A

Spiralled

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19
Q

Describe the caecum in cats

A

comma shaped

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20
Q

Describe the caecum in the ruminant

A

No taenia
No haustra
Relatively small

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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

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22
Q

Where is the GALT found?

A

Submucosa and mucosa

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23
Q

Describe the colon in dogs

A

Ascending
Transverse
descending

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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

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25
Q

Describe the colon in pigs

A

Cone shaped w coiled ascending
Base is attached to left abdominal
apex points ventrally
2 taenia and 2 rows of sacculations

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26
Q

Describe the colon in horses

A

Large ascending ( right vent-> left vet-> left dorsal-> right dorsal)
Short transverse and large descending
right dorsal is spot for impactions

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27
Q

What are the exocrine components of the stomach?

A

Mucin producing cells
Parietal cells
chief cells

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28
Q

What are the 3 muscle layers of the stomach?

A

Oblique muscle
Longitudinal muscle
Circular muscle

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29
Q

What are the endocrine components of the stomach?

A

ECL cells
Gastrin producing cells

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30
Q

Outline the neural stimulation of the stomach in secretion (long reflex)

A

LONG REFLEX
Expansion of stomach -> sensory nerve endings -> CNS impulse via vagal nerve = acetylcholine release from submucosal plexus
= stomach secretion

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31
Q

Describe the hormonal stimulation of the stomach

A

SHORT REFLEX
Stomach expansion = peptide release = gastrin release
Sensory nerve endings send impulse to stomach via vagal nerve releasing acetylcholine

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32
Q

What cells is responsible for stomach emptying?

A

Cajal cells

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33
Q

What is the process of regulating contraction in the stomach?

A

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

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34
Q

What are the phases of degluttination?

A

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

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35
Q

What is large intestine contraction stimulated by?

A

Stomach and the duodenum long reflex arc via the mesenteric nervous system

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36
Q

How is appetite controlled?

A

Modulating signal are read in the satiety centre which leads to feeding behaviours

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37
Q

What are the movements of the small intestine?

A

Segmentation
Peristaltic waves
Antiperistaltic waves
Mass movement

Driven by stretch measures by the mesenteric plexus and CNS/PNS

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38
Q

How is pancreatic juice and bile increased?

A

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

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39
Q

What factors affect stomach emptying?

A

Inhibited by duodenal factors stimulating SYMP fibres =
Secretin release, gastric inhibiting peptide and cholecystokinin (CCK)

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40
Q

What is the biological mechanism for ion exchange across the smooth muscle membrane?

A

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

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41
Q

Compare smooth and skeletal muscle

A

Smooth = no sarcomeres
Skeletal= stimulated by acetylcholine from motor neurones
Smooth and cardiac = use gap junctions to transmit signals for coordinated contraction

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42
Q

Compare the membranous and luminal phases of digestion

A

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

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43
Q

Define Secretory diarrhoea

A

Increase in active secretion or inhibition in the absorption
No structural damage

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44
Q

Define osmotic diarrhoea

A

Too much water taken into the bowels

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45
Q

Define Motility related diarrhoea

A

Rapid movement of food through the intestine

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46
Q

Define inflammatory diarrhoea

A

Damage to the lining of the intestine = loss of protein rich fluid and decrease in the ability to absorb

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47
Q

Outline the digestive physiology of rabbits

A

Proximal colon separating ingesta
Two types of faecal pellets (large= indigestible to colon) (small= retrograde to caecum for microbial fermentation= caecotrophs)

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48
Q

What is the role of the proximal colon and the ampulla coli together?

A

Location of mixing and separating ingesta
Large particles continue to the colon

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49
Q

What is the role of the appendix in the rabbit?

A

Secretes bicarbonate ions
Buffering role for volatile fatty acids

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50
Q

What are haustra in the rabbit?

A

Outpouchigns along the proximal colon
Increase SA and separate ingesta

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51
Q

What is the role Warzen? §

A

Increase SA ( small protrusions in rabbits)

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52
Q

Compare the internal anatomy of the proximal colon and the distal colon in rabbits.

A

In proximal colon there are 3 taeniae, haustra and warzen will be seen

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53
Q

What is the role of the fusus coli?

A

Mucous producing and highly muscular found towards the distal end of the proximal colon in rabbits

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54
Q

What drives caecal fermentation in rabbits?

A

Bacteria, protozoa and yeast
Most common is Bacteriodes spp

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55
Q

What are the products of caecal fermentation in rabbits?

A

VFAs
Amino acids
Water soluble vitamins

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56
Q

What can change the pH of a rabbit caecum?

A

Changes diurnally

Volatile fatty acids
Ammonia
Bicarb ions from the appendix buffer

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57
Q

How do the contents in the rabbit GI separate?

A

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

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58
Q

What is the name of the T section where the rabbit ingesta is separated?

A

Ampulla coli

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59
Q

What are the faecal production phases for rabbits?

A

Hard faeces = fusus coli contracts to squuez out water with mucous production
Soft faces = rest

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60
Q

Motility in the soft faeces phase in rabbits?

A

Caecum and prox colon motility ddecreases
distal colon increases
Fusus coli adds mucous but does not squeeze out the water

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61
Q

What are the properties of a caecotroph?

A

Outer greenish membrane
Proein> fibre
Protein from fermentation or bacteria
Undigested nutrients
Vitamin B and K

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62
Q

Where is lysosome added to caecotrophs and why?

A

Added in distal colon to digest bacterial cell walls allowing rabbits to utilise the proteins from the bacteria

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63
Q

What is the pacemaker of rabbits large intestine?

A

Fusus coli
Initiates peristaltic waves in the colon as it is highly innervated and has hormonal influence from aldosterone and prostaglandins

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64
Q

How does diet affect rabbits gut motility?

A

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

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65
Q

What is the palatal ostium?

A

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

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66
Q

Describe the chinchilla GI tract

A

Large coiled caecum
Sacculated colon
Caecotrophs produced

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67
Q

Describe the cheek pouches of hamster

A

Thin walled highly distensible
Immunologically privileged
Pre gastric fermentation

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68
Q

Describe ferret GI tract

A

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%

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69
Q

Approach to horse with colic:

A

History
Physical exam
Diagnostic techniques
- rectal palp
- nasogastric intubation
- abdo paracentesis

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70
Q

What are the issues with equien grazing diets?

A

Grass contains silicates - harder than enamel so damage teeth
Cellulose and hemicellulose cannot be digested - microbial digestion only

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71
Q

How do horses use different teeth

A

Lips and incisors - grasp/prehend food
Rigid molars - grinding
Irregular molar surface is better for grinding
Rotational chewing movement

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72
Q

What are the main properties of the equine stomach?

A

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

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73
Q

What are the properties of the equine small intestine?

A

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

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74
Q

How are fructans digested in the horse?

A

Pass into large intestine and digested by bacteria = acidic env alters the large intestinal flora

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75
Q

Describe the equine caecum

A

Microbial digestion, water + electrolytes
Blind ending sac w two muscular valves
Pacemaker region

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76
Q

Describe the equine large colon?

A

Made up of right and left ventral colon and right and left dorsal colon

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77
Q

Role of the equine small colon?

A

Storage of faeces and absorption of remaining water

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78
Q

What can be palpated on the left and right hemisphere of the equine abdomen per rectum

A

L
Spleen
caudal pole of left kidney
Pelvic flexure
Small colon
R
Caecum

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79
Q

What can be analysed from an equine peritoneal tap?

A

Colour
volume
turbidity
Total protein
cell no. and type

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80
Q

What are the components of the extracellular fluid?

A

Plasma
Lymph
Interstitial GI fluid
Synovial, peritoneal and pleural fluid

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81
Q

What are the percentages for ECF and ICF?

A

ICF= 30-40%

ECF= 20-40%

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82
Q

How is blood volume calculated

A

90-100ml per kg

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83
Q

Where is most of the water absorbed in the GI tract?

A

Proximal small intestine is secretion
Small and large intestine is absorption

Dogs/cats = LI
Ruminant = omasum
Horse= small colon
rabbit = distal colon

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84
Q

What is the major site of digestion in dogs and cats?

A

Small intestine

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85
Q

What is the major site of digestion in the ruminant?

A

Rumen

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86
Q

What is the major site of digestion in the horse?

A

Caecum
And rabbit

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87
Q

What is the muscular layer of the small intestine made of?

A

Outer most layer composed of elastic fibres and smooth muscle cells in circular and longitudinal arrangement

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88
Q

Define chyme

A

Acidic fluid made up of gastric juices and partly digested food

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89
Q

Define peristalsis

A

Involuntary constriction and relaxation of muscles creating wave like motion pushing contents forward

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90
Q

Define segmentation

A

Rhythmic contraction of circular muscles that divides and mixes chyme - mixes food w gastric juices and breaks it down further

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91
Q

Define mass movement

A

Large waves of motility

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92
Q

Where are interstitial cells of cajal found?

A

Found in circular muscle of intestine

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93
Q

Compar sacculations in rabbits and horses

A

In horses they increase SA
In rabbits they are used to collect smaller particles

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94
Q

What are the main types of motility in the caecum and the colon?

A

Haustral contractions and mass movemnt in colon
Caecum have segmentation contractions for mixing

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95
Q

What are the sites of the pelvic, sternal and diaphragmatic flexures?

A

Sternal = RVC- LVC
Pelvic = LVC and LDC
Diaphragmatic = LDC-RDC

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96
Q

What is the affect of para and sympathetic stimulation on the gut motility?

A

Symp decreases
Para increases

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97
Q

How is the rectum emptied?

A

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

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98
Q

Which species have voluntary control over emptying rectum?

A

Carnivores
Ruminants = no control

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99
Q

What part of the crypt villus unit digests and absorbs nutrients?

A

Mature enterocytes on the villi tips
Absorb
CHO
AA
Lipids
Minerals water ions

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100
Q

What is the role of the crypts of lieberkuhn?

A

Produce immature enterocytes and other gut cells from stem cells

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101
Q

What is the brush border of the small intestine?

A

Has a thick mucous layer of microvilli
mature enterocytes are bound to the cell membrane to breakdown nutrients

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102
Q

How are small intestine epithelial cells regenerated?

A

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

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103
Q

What are the cells of the crypt villus units?

A

Enterocyte - enzymes and absorption
Enteroendocrine- hormones
Goblet - mucous
Paneth cells = lysosome inhibits bacteria

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104
Q

How are goblet cells adapted for mucous secretion?

A

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

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105
Q

What stem cells to goblet cells arise from?

A

Pluripotent stem cells
found in bone marrow, blood and adipose tissue

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106
Q

What is the goblet cell response to inflammation?

A

Inc production of mucin = more mucous for protection

107
Q

What feedback mechanism operates for the crypt to reform damaged villus?

A

Homeostatic feedback
positive feedback

108
Q

What does high levels of radiation target?

A

Genetic material

109
Q

What are the 3 sections of the small intestine?

A

Ileum
Jejunum
Duodenum

110
Q

What is the blood supply to the ileum?

A

anitmesenteric and mesenteric

111
Q

Describe the submucosa of the small intestine?

A

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
Q

What are the properties of the mucosa of the small intestine?

A

Epithelial cell layer = functional
Lamina propria= loos connective tissue and immune cells (presence of crypts of lieberkuhn)

113
Q

What will the affects of hyper and hypomotile muscularis in the small intestine?

A

Hypermotile segmented contractions = delay passage
Hypomotile segemented contractions = increase passagfe
ileus= lack of motility and bacterial overgrowth

114
Q

What is responsible for the mixing motion in the SI?

A

Tunica muscularis

115
Q

Describe the blood capillaries of the crypt villus units?

A

In lamina propria
Large fenestrations = plasma proteins can move into interstitial space

116
Q

What are lacteals in the crypt villus units?

A

Blind ending lymphatic capillaries that transport emulsified fats (chylomicrons) for lymphatic drainage -> cranial vena cava

117
Q

What is the venous drainage of the small intestine?

A

Hepaticoportal vein

118
Q

What shape is the duodenum>

A

U shape
Short mesentery
Sheep and goats = desc limb
Primates = both
Horses, pigs cattle= extend into the jejunum

119
Q

Where is the ileum connected?

A

Caudal jejunum to the ileum to the caecum
Ileum -> caecum = ileocaecal fold (contains BV)

120
Q

What are the 5 cell types in the small intestine?

A

Enterocytes
Enteroendocrine
Goblet cells
Paneth cells
M cells

121
Q

What is the cell escalator process in the small intestine?

A

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
Q

What happens during crypt neck differentiation?

A

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
Q

How does the secretory function of the duodenum create the correct environment?

A

Serous contains bicarb
Mucous = protection

124
Q

How does parvovirus infect as a secondary intestinal infection?

A

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
Q

What is the structure and function of the enterocytes?

A

Columnar epithelial cells w microvilli

Smooth ER for transport of nutrients
Pinocytosis for vesicles
Protective function
Tight junctions between enterocytes

126
Q

What is the structure and function of the enteroendocrine cells?

A

Scattered along GI
Closed and open types
20 different hormones produced
Islet of langerhans cells are EECs

127
Q

What are the paneth cells?

A

Apical granules with innate mucosal defences (defensins and lysosome) at the bottom of the crypts
Only present in horses and cattle

128
Q

What are M cells?

A

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
Q

What are the properties of the peyers patches in the GIT?

A

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
Q

Describe the lymphoid follicles in the GIT

A

Aggregations of lymphocytes and macrophages within the lamina propria
No contact with lumen unlike the peyers patches

131
Q

Where are the lymph nodes in the GIT?

A

Within the mesentery
At different levels according to the species (near the gut or near the root)

132
Q

What is the structure and function of the pancreas in the dog?

A

Two lobes in duodenal flexure
Exocrine function for digestive enzymes and alkaline fluids
Endocrin function - insulin, glucagon, somatostatins and pancreatic polypeptide

133
Q

Where is the pancreas ?

A

Part of pancreas is always between the descending and ascending limbs of the duodenum

134
Q

What is responsible for pancreatic stimulation?

A

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
Q

What blood vessels supply to small intestine and the pancreas?

A

Coeliac artery - left gastric, hepatic and splenic
Cranial and caudal mesenteric

136
Q

Where is meissners plexus and auerbachs plexus?

A

Meissners = submucosa
Auerbachs= Between smooth muscle layers

137
Q

What are the parasympathetic pathways to the GIT?

A

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
Q

How is TAG formed?

A

Triacylglycerol is formed by condensation reaction between glycerol ester and 3 fatty acids

139
Q

How are lipids digested?

A

Large drop is reduced by bile acids/bile salts
CCK = bile secretion
Phospholipase A2 in pancreas, Lecithin-> lysophospholipids = strong detergent

140
Q

How is the accumulation of lipids in the intestinal epithelium targeted?

A

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
Q

What are the roles of lingual and pancreatic lipase?

A

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
Q

What is the structure of chylomicrons?

A

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
Q

What are the role of chylomicrons?

A

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
Q

What are the classifications for chylomicrons?

A

Chylomicron
VLDL
IDL
LDL
HDL

145
Q

Define pica

A

A compulsive disorder where an organism eats something it wouldnt usually eat

146
Q

What is EPI?

A

Exocrine pancreatic insufficiency
Lack of pancreatic enzymes reduce the absorption of nutrients from the food

147
Q

What are oligosaccharides?

A

Formed from between 309 monosaccharides

148
Q

What is hemicellulose composed of?

A

xylose
Glucose
Mannose
Arabinose

149
Q

How are carbs digested?

A

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
Q

What limits the rate of lactose uptake?

A

Rate of hydrolysis

151
Q

What is the function of the pancreas?

A

Secretes zymogens to aid protein digestion
Beta cells = insulin
Alpha cells = glycogen
Delta cells = somatostatin
Acini cells = Digestive enzymes

152
Q

What zymogens are released by the exocrine pancreas?

A

Trypsinogen
Chymotrypsinogen
proelastase
Procaboxpepitidase

There is a cascade of the zymogens starting with trypsinogen being cleaved into trypsin by enteropeptidase

153
Q

Define protease

A

Enzyme that carries our proteolysis

154
Q

What are the 6 groups of proteases?

A

Serine protease
Threonine protease
Cysteine protease
Aspartic acid protease
Metalloproteases
Glutamic acid proteases

155
Q

Define exopeptidase?

A

Detach terminal amino acids from polypeptide
on membrane of small intestine only

156
Q

Define endopeptidase

A

Hydrolyse internal peptide bonds of a protein

157
Q

What is the action of serine endopeptidases?

A

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
Q

What are aminopeptidases?

A

Attack aa terminal of peptides secreted form the small intestine
Considered exopeptidases

159
Q

What are the phases of protein digestion?

A

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
Q

What are the 2 dominant routes for amino acid transport?

A
  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
Q

What are the neurotransmitters and substances involve in the ENS?

A

Acetyl choline
Noreinephrine
Seratonin (5-H)
Purines
Nitric oxide

162
Q

Which fibres terminate in the plexus of the gut?

A

Sympathetic

163
Q

What is the endocrine and paracrine control of the GIT?

A

Endocrine- gastrin and CCK (peptides from mucosa)
Paracrine- Local regulatory peptides such as histamine

164
Q

Which parts of the GI tranct can be modified pharmacologically>

A

Gastric secretion
Mucosal protection
Emesis
Motility
Inflammation
Foam formation
Digestion

165
Q

How can gastric secretions be modified?

A

Local prostaglandins control secretion of mucus and bicarb
modifications (neutralisation, mucosal protection , absorbents)

166
Q

Drugs for neutralisation of gastric secretion?

A

Magnesium hydroxides and trisilicate
Aluminium hydroxide gel
Algniates and simeticone

167
Q

Drug for mucosal protection of the GI tract

A

Sucralfate- can prevent uptake of other drugs

168
Q

What are the properties of the drugs used as absorbents in the GI tract?

A

usually have coating actions that bind to bacteria and toxins
Protect lining of stomach from excess acid

169
Q

What cells on the lumen side of the stomach pump out H+

A

Parietal cells

170
Q

What receptors is the production of HCl in the stomach dependent on? How does this help drug use?

A

Muscarinic receptors
Histamine 2 receptors
Gastrin receptors

To decrease HCl production just block any of these receptors

171
Q

Acetyl choline antagonist?

A

Atropine

Not a selective drug so can affect other areas

172
Q

What is the best target for stopping HCl production in gastric secretion?

A

Proton pump inhibitors

173
Q

Regulatory process that maintains homeostasis in stomach and reduced production of HCl

A

Production of Prostaglandin E2
Binds to receptor on parietal cell to reduce HCl production

174
Q

What are prostaglandins produced from?

A

Arachidonic acid

175
Q

Main proton pump inhibitors

A

Omprazole
Lasoprazole

176
Q

How do histamine antagonists affect gastric secretion?

A

Inhibit gastrin, histamine and acetylcholine stimulated by secretion
Pepsin secretion falls

177
Q

Histamine antagonists

A

Ranitidine
Cimetidine

178
Q

Action of cimetidine

A

Inhibits cytochrome P450 and slows metabolism

179
Q

How does misoprostol modify gastric secretion?

A

Stable analogue of PGE1
Inhibits acid sec
increase mucosal blood flow
increases uterine contraction

180
Q

What are the emesis centres?

A

Chemoreceptor trigger zone
Vomiting centre in the brainstem

181
Q

What does the chemoreceptor trigger zone respond to for emesis?

A

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
Q

Vomiting centre in the brainstem?

A

coordinates and integrates vomiting

183
Q

What is the pathophysiology of vomiting?

A

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
Q

What receptors are involved in vomiting?

A

Substance P = neurotransmitter
NK-1 receptor found on cell membranes in vomiting centre
`Correct ligand to NK-1 rec= conformational change

185
Q

Pharmacological emetics?

A

Apomorphine- dopamine agonist (IV or mucosal)
Alpha 2 agonists - Xylazine
Syrup of Ipecac - Direct irritant

186
Q

What are the 2 main groups of dopamine antagonists?

A

Phenothiazine derivatives - centrally acting dopamine antagonists
Metaclopramide and domperidone - short action

187
Q

What type of drug is chlorpromazine?

A

Dopamine antagonist
Phenothiazine derivative

188
Q

The action metraclopramide and domperidone together in dopamine antagonism

A

Metra- mainly works centrally
Domperidone works peripherally
Increase gastric emptying and motility

189
Q

How does Cerenia act as an anti emetic?

A

NK-1 antagonist
Competes with substance P
Completely shuts down final step of vomitings
Specifically designed for dogs

190
Q

What clinical signs may require modification of intestinal motility>

A

Diarrhoea
Colic and stress

191
Q

What aspects of SI motility are modified?

A

increase or decrease transit time = affects water absorption
Reduced pain

192
Q

What are the common spasmolytic antimotility drugs and how do they work?

A

Opiates
Muscarinic antagonism

193
Q

Main opiates to treat diarrhoea

A

Morphine
Codeine
Loperamide (imodium) - doesnt cross BBB so no psychoactive effects

194
Q

How can muscarinic antagonists act as antimotile drugs for GI tract?

A

Motility is under neuronal control
Inhibit acetylcholine stimulatory effects from the vagus nerve

195
Q

What are the different types of laxatives?

A

Saline and hyperosmotic agents
Bulk producing agents
Irritants

196
Q

Bulk laxatives

A

methylcellulose
Agar bran
- Not easily digested so hold water in gut = promotion of peristalsis

197
Q

Osmotic laxative

A

Lactulase
Broken down in GI to lactic acid
Alters pH more acid
Traps ammonia and therefore water

198
Q

What receptors do prokinetics act on for gut motility?

A

Seretenergic 5-HT receptor agonist
Cisapride

199
Q

When are anti inflammatories used in GI?

A

Idopathic inflammatory bowel disease
- Steroid= predisnolone
- Sulphasalazine - pro drug converted to salicylic acid in gut

200
Q

When are antifoaming agents used?

A

Treatment of frothy bloat in ruminants
- Surfactants which cause bubbles to break down

201
Q

What is the rectum?

A

Terminal part of the large bowel
Arbitarialy delineated

202
Q

What are the histological layers of the rectum?

A

Mucosa - columnar epi, lots of goblets, lymphoid nodules
Submuc
Muscularis
Serosa

203
Q

Describe the organisation of the rectum muscularis muscle fibres

A

Stratum longitudinale - fibres dorso caudally = RECTOCOCCYGEYS MUSC
Stratum circulare = caudally = INTERNAL ANAL SPHINCTER MUSCLE

204
Q

Where is the caudal rectum and anal canal in relation to caudal peritoneum?

A

Retroperitoneally

205
Q

Describe the mesorectum

A

Extension of the mesocolon
Wider cranially
Tapers away with the serosal layer at 2 coccygeal vertebrae

206
Q

What is the blood supply to the rectum?

A

Caudal mesenteric
Left colic
Cranial rectal
Internal pudendal-> caudal rectal and middle rectal arteries

207
Q

Venous drainage from the rectum?

A

Cranial rectal-> caudal mesenteric-> hepatic portal vein

Middle rectal + caudal rectal-> internal pudendal vein -> internal iliac

208
Q

What is the anus

A

Specialised junction between mucosa and integumentary

Surrounded by smooth and striated muscle sphincters

209
Q

What are the 3 anal zones

A

Columnar
Intermediate
Cutaneous

210
Q

Properties of the cutaneous anal zone

A

Hairless skin
Squamous stratified epi
Ext and int components
Anal sac ducts open in this region

211
Q

WHat are the properties of the intermediate anal zone?

A

Narroe mid section
Transition from columnar- skin epi
1 mm wide
Anocutaneous margin
Stratified columnar cells

212
Q

What are the properties of the columnar anal zone?

A

Series of longitudinal ridges
Folds= anal sinuses
Prox = anorectal junction
Lined with columnar epi

213
Q

What is the internal sphinter and external sphincter made of?

A

Internal= smooth musc from circular layer
External = skeletal muscle

214
Q

What is the role of the anal sphincters?

A

Covers anal sacs in Dogs and cats = compresses during defacaetion

215
Q

Innervation of the internal anal sphincter?

A

Autonomic
PNS via pelvic and hypogastric plexuses
SNS via hypogastric via caud mesenteric ganglion

216
Q

What is the innervation of the external anal sphincter?

A

Somatic control
Innervated bilaterally by the anal branch of the pudendal nerve

217
Q

What is the defaecation reflex?

A

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

218
Q

What is the gastro colic reflex?>

A

Causes onward passage of facecal material from colon to rectum
= anorectal reflex

219
Q

What is colitis and what are the main clinical signs?

A

Irritation of rectum causes repeat attempts to defaecate with no faeces presetn

220
Q

What supports the rectum?

A

Pelvic diaphragm
Group of muscles

221
Q

What does rectal function rely on during defaecation?

A

Calais of the pelvic diaphragm muscles to compress the pelvic contents

222
Q

What are the major muscles of the pelvic diaphragm?

A

Coccygeus muscle
Levator ani

223
Q

Origin and insertion of levator ani

A

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

224
Q

What is the insertion and origin of the coccygeus muscle

A

Originates at the ischiatic spine
Inserts on the transverse processes of caudal vertebrae 2 - 4

225
Q

3 groups of perianal glands

A

Anal glands
Circumanal glands
Anal sacs have secretory epi lining

226
Q

What anal glands are present in dogs and cats and where are they located?

A

ANal glands - cranial to the anocutaneous line = fatty secretion

Scattered apocrine glands around anus in cutaneous zone = caudal to anocutaneous line

227
Q

Where are the circumanal glands located in the dog?

A

around anus and cutaneous zone for water proofing
Sebaceous glands

228
Q

Describe the anal sacs

A

Paired diverticula present in carnivores
In submucosa - lined by apocrine and paranal sinus glands

Open into the anal canal
prone to occlusion

229
Q

Where are the anal sacs located?

A

Pea - bean size
Either side of anal opening at 4 and 8 oclock
Embedded between internal and external anal sphincter muscs

230
Q

What are the properties of the anal glands within the anal sacs?

A

within the wall of the sacs
Coiled apocrine tubules
cornified stratified epithelium
Secrete foul smelling secretion

231
Q

What is anal furunculosis?

A

Immune mediated fistula occurs
seen in combination with anal sac abscessation
Causes deep pyoderma

232
Q

What are hepatoid adenomas?

A

Testosterone dependent benign masses
found in ext region of outer cutaneous zone

233
Q

How can rectal prolapses occur?

A

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
Q

How does a perineal hernia occur?

A

Degeneration of pelvic diaphragm
Anal sphincter and levator ani separate
Or levator ani and coccygeus musc separate

235
Q

Define atrestia

A

Absence or abnormal narrowing of an opening or passage in the body

236
Q

Define hernia

A

Internal part of the body pushes out through a weakness in the muscle or surrounding tissue wall

237
Q

Define atresia ani

A

Developmental defect of the anal opening or terminal rectum

238
Q

Define faecaloma

A

Mass of faeces noted in rectum or colon

239
Q

Define steonsis

A

Abnormal narrowing or passage in the body

240
Q

Define tenesmus

A

Continual or recurrent inclination to evacuate the bowels = caused by rectum disorder

241
Q

Define reducible hernia

A

Hernia with bulge that flattens out when you lied down or push against in gently

242
Q

Define imperforate

A

Lacking normal opening

243
Q

Define rectovaginal fistula

A

Communication between dorsal wall of vagina and ventral portion of rectum
vulva functions as common opening for uro tract and GIT

244
Q

Define fistula

A

Abnormal connection between two body parts such as an organ or a blood vessel

245
Q

Where is the inguinal canal located?

A

Internal oblique musc on one side of the pelvic tendon of the external oblique aponeurosis on the other side

246
Q

What passes through the inguinal canal in males shortly after birth?

A

Testes

247
Q

What is cryptorchidism?

A

Retention of testes
Failure to pass through the inguinal canal

248
Q

What anatomical structures are present in the inguinal canal in females?

A

Round ligament
Genital branch of genitofemoral nerve
Iliolingual nerve

249
Q

What anatomical structures are present in the inguinal canal in males?

A

Spermatic cord with the genital branch of the genitofemoral nerve and the iliolingual nerve

250
Q

Type 1 atresia ani

A

Congenital stenosis of patent anus

251
Q

Type 2 atresia ani

A

Persistence of complete anal membrane alone or a combination of anal membrane with rectum ending as blind pouch to cranial membrane

252
Q

Type 3 atresia ani

A

Imperforate anus with rectum terminating further cranially

253
Q

Type 4 atresia ani

A

normal ending of terminal rectum and anus
Cranial rectum terminates as a blind pouch within the pelvis

254
Q

Atresia coli

A

Incomplete large bowel or colon

255
Q

Inguinal or scrotal hernia?

A

indirectly herniated organs pass along the tunica vaginalis to the level of the scrotum

256
Q

Umbilical hernia

A

Incomplete closure of the umbilical ring after birth

257
Q

Diaphragmatic hernia

A

Hole in the diaphragm means that organs in the abdomen can move upwards into the thorax

258
Q

Which structures can be examined on a small animal rectal exam?

A

anus, rectal wall,anal glands, reproductive tract, urethra, pelvis, and lymph node

259
Q

emetic agents

A

Apomorphine
Alpha 2 agonists
Sgruposle

260
Q

Antiemetics

A

Phenothiazone derivatives
Metaclopramide
Domperidone cerenia

261
Q

What drugs can be used as spasmolytics

A

Opiates
muscarining antagnosts

262
Q

What are the 3 classes of laxatives?

A

Bulk
Osmotic
Prokinetics

263
Q

What centres control vomiting

A

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
Q

What is the pathophysiology of vomiting?

A

pathways can be central or peripheral
substance P is the neurotransmitter which binds to NK-1 receptors at the cell membrane

Veterinary medicine year 2 (23 decks)

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