GI Flashcards
0
Q
What is starch digested by?
What pH does it work at?
A
Amylase
pH greater than 6
1
Q
What is the definition of digestion?
A
Enzymatic breakdown of nutrient macromolecules into smaller units that can be absorbed
2
Q
What is protein digested by?
What pH does it work at?
A
Pepsin
Low pH
3
Q
Which bonds are present in starch?
A
a-glycosidic
4
Q
How have pigs adapted their stomachs to allow longer starch digestion?
A
No acid secretion in fundus, only mucous is secreted
5
Q
What does gastric juice consist of?
A
HCl and pepsinogen (inactive pepsin)
6
Q
What do chief (peptic) cells secrete?
A
Pepsinogen
7
Q
What are the functions of HCl?
A
Converts pepsinogen to pepsin
Provides acidic environment for pepsin
Prevents fermentation by killing micro-organisms
Degrades large chunks of connective/muscle tissue into smaller units
8
Q
What do parietal (oxyntic) cells secrete?
A
HCl
9
Q
What are the 3 phases of regulation?
A
Cephalic, gastric, intestinal
10
Q
Where is secretin released from?
A
Duodenum, in response to H+
11
Q
Define microbial fermentation
A
Chemical breakdown of a substance by micro-organisms under anaerobic conditions
12
Q
Why must rumination be under anaerobic conditions?
A
Under aerobic conditions food substances would be completely broken down to CO2 and H2O which don’t provide energy to the host.
13
Q
When FFAs are transported in the bloodstream, what are they bound to?
A
Albumin
14
Q
What are the microbial products of equine fermentation?
A
VFAs, CH4, CO2
15
Q
How is water absorbed in the large intestine of the horse?
A
Secretion of H+ in exchange for Na+ converts VFA ions to respective acids (more easily absorbed as acids)
HCO3- exchanged for Cl-
Net absorption of NaCl
This enhances water reabsorption by solvent drag and osmotic pressure
16
Q
How does fungi aid digestion in the horse and ruminant?
A
Spores attach to lignin and split it apart, (by hyphae), making it susceptible to digestion by cellulolytic bacteria
17
Q
Where does colonic impaction usually occur?
A
Pelvic flexure
18
Q
What is the definition of motility?
A
Contraction of muscles that mix and propel the contents in the GI tract
19
Q
What is the difference between egestion and excretion?
A
Egestion= elimination of undigested material eg faeces Excretion= elimination of waste products that have been formed by chemical reactions in the body eg sweat, urine
20
Q
Which kind of saliva is present in simple and complex stomached animals?
A
Simple=mucous to lubricate passage of food
Complex=serous to provide optimum conditions for fermentation
21
Q
What is the pH of saliva of simple and complex stomached animals?
A
Simple=neutral for amylase action
Complex=alkaline to buffer the forestomach for fermentation
22
Q
In which species is amylase present in saliva?
A
Omnivores (high) and horses (low; not carnivores and ruminants)
23
Q
What are the components of saliva?
A
Mucin Amylase (omnivores and horses) Bicarbonate (neutralisation/buffer) Phosphate (ruminants) Lysozyme/antibodies (reduce infection) Protein-binding tannins (leaf and bud-eaters) Urea (ruminants)
24
How do the following nervous systems affect saliva secretion:
Sympathetic
Parasympathetic
Sympathetic-decreases during fight or flight
| Parasympathetic-increases during digestion
25
Why are anti-peristaltic contractions used?
Slow down the transit of digesta to allow sufficient digestion/absorption
To allow rumination in ruminants
Protective (vomitting)
26
What pH is required for protein digestion in the stomach?
2
27
What pH is required by digestive enzymes in the small intestine?
6-7
28
Where does digestion of smaller food components occur?
Mucosal surface, to facilitate absorption
29
Which enzymes break down:
| Carbohydrates, protein, fat
Carbohydrate: amylase, disaccharidases
Protein: pepsin, trypsin, peptidases
Fat: lipase, phospholipase
30
What is the peritoneum?
A serous membrane that lines the abdominal cavity and envelops the abdominal organs
31
What are the 3 types of peritoneum?
Parietal (closely adherent to abdominal wall)
Visceral (closely adherent to organ surface)
Connecting (dictates where organs stay within the abdomen)
32
What are the 4 kinds of connecting peritoneum?
Mesentery (connects bowel to body wall)
Omentum (connects stomach to something)
Fold (connects bowel/organ to one another)
Ligament (connects organ, usually non-GI, to body wall/bowel)
33
Where does the diaphragm attach?
Attaches to body wall at level of last rib
| Extends into thorax to level of 5th intercostal space
34
Why are organs lobed?
To enable them to move with the diaphragm
35
Name the 4 lobes of the liver
Left
Right
Caudate
Quadrate
36
What did the falciform ligament used to be?
Umbilical vein
37
What are the 3 areas of the canine stomach?
Fundus (blind-ending)
Corpus (body)
Pylorus (pyloric antrum)
38
Which epithelium is present in the oesophageal region during development of the stomach?
Which region does this form in the horse and ruminant?
Stratified squamous
Horse=fundus
Ruminant=fore-stomach
39
Which ducts exit onto the major duodenal papilla?
Bile duct and pancreatic duct
40
Which duct empties onto the minor duodenal papilla?
Accessory duct
41
How many lobes does the pancreas have?
Two:
Right runs in cranio-caudal direction
Left runs in medio-lateral direction
42
Where is each lobe of the pancreas located?
Right=within meso-duodenum
| Left=within deep leaf of greater omentum
43
Where does the ileum enter the large intestine?
At the caeco-colic junction
44
Why do pigs only need minimal hair cover on their skin?
Subcutaneous fat provides insulation instead
45
What does the superficial fascia (under the skin) contain?
Adipose (all over in pigs, inguinal area on others)
| Cutaneous trunci muscle (skin twitch)
46
What is the function of the deep fascia/yellow abdominal tunic in the ox/horse?
Gives extra strength to support the massive weight of the abdominal organs
47
What are the 4 muscles of the abdominal wall?
External abdominal oblique
Internal abdominal oblique
Transverse abdominal muscle
Rectus abdominis
48
What are the motor functions of the abdominal wall muscles?
Contraction of the muscles causes an increase in intra-abdominal pressure (vomiting, defaecation, urination)
If larynx is closed, also causes an increase in intra-thoracic pressure via diaphragm (breathing, coughing, sneezing)
49
Where does the external abdominal oblique muscle originate and insert?
Which direction do the fibres run?
Originates: lateral surface of ribs, from 4th rib, and lumbodorsal fascia
Inserts: linea alba and prepubic tendon
Fibres run obliquely from cranio-dorsal to caudo-ventral
50
Where does the rectus abdominis muscle originate and insert?
Originates: ventral surface of sternal ribs and sternum
Inserts: cranial border of pubis via pre-pubic tendon
51
Where does the internal abdominal oblique muscle originate and insert?
Originates: tuber coxae of pelvis and lumbodorsal fascia
Inserts: linea alba, last rib and cartilages of caudal ribs
52
Where does the transverse abdominal muscle originate and insert?
Originates: medial surfaces of ventral parts of caudal ribs and deep lumbodorsal fascia
Inserts: linea alba
53
Which spinal nerves innervate the abdominal wall muscles?
T13 and L1-L5
54
Which are the 3 branches of the ventral root nerves that supply the abdominal wall muscles?
Medial-runs between transverse and internal oblique down to rectus abdominis
Lateral-runs between internal and external oblique down to midway
Lateral cutaneous-perforates external oblique to innervate skin
55
What is the inguinal canal?
Potential space between the deep inguinal ring (internal oblique) and superficial inguinal ring (external oblique)
56
What does the foregut differentiate into?
Pharynx, oesophagus, stomach and initial duodenum
57
What does the midgut differentiate into?
Rest of duodenum, jejunum, ileum, caecum, ascending/transverse colon
58
What does the hindgut differentiate into?
Descending colon and rectum
59
What supplies the blood supply to the foregut?
Branches of the celiac artery (off aorta)
60
Which primordia (ventral and dorsal) form which lobes of the pancreas?
Dorsal primordia becomes the left lobe with the pancreatic duct
Ventral primordia becomes the right lobe with the accessory pancreatic duct
Both eventually fuse
61
What supplies the blood supply to the midgut?
Branches of the cranial mesenteric artery
62
What supplies the blood supply to the hindgut?
Branches of the caudal mesenteric artery (off the aorta)
63
Which kind of feedback is digestion mainly regulated by?
Negative feedback
64
What do sensory cells in the ENS respond to?
Contents of lumen
| Degree of wall stretch
65
What do motor cells in the ENS stimulate?
```
Smooth muscle cells (motility)
Epithelial cells (secretion of digestive juices/hormones)
```
66
What does a simple reflex arc consist of?
A single sensory cell and a single motor nerve cell
67
What does a complex reflex arc consist of?
Simple reflex arcs connected by interneurons
| nerve impulse is propagated wider
68
How does the sympathetic nervous system prevent digestion?
Post-ganglionic fibres synapse with ENS or reduce acetylcholine release at parasympathetic pre-synapses. They are adrenergic (transmitter=noradrenaline) to inhibit secretion and motility, and decrease blood supply to the GI tract
69
What effect does gastrin have on the GI tract?
Stimulates HCl
| Stimulates growth of intestinal/gastric mucosa
70
What effect does secretin have on the GI tract?
Stimulates pancreatic HCO3-
71
What effect does cholecystokinin (CCK) have on the GI tract?
Stimulates pancreatic enzymes
| Contracts gall bladder
72
What effect does GIP (gastric inhibitory peptide) have on the GI tract?
Inhibits HCl
| Stimulates insulin production
73
Where is appetite controlled?
Hypothalamus:
Appetite centre causes food searching and voracious eating
Satiety centre causes refusal of food, inhibits appetite centre
74
What are the 4 types of muscle contraction in the GI tract?
Segmental-mixes lumen contents
Peristalsis-moves contents in aboral direction
Anti-peristalsis-moves contents in oral direction
Mass movement-empties entire sections of GI tract
75
What is the name of the pacemaker cells in the GI tract?
Interstitial cells of Cajal
76
Where is the swallowing reflex initiated?
Swallowing centre in medulla
| Involuntary control
77
Which cranial nerves supply the cranial and caudal oesophagus?
Cranial: Recurrent laryngeal of accessory nerve
Caudal: Vagus
78
In which species is the lower oesophageal sphincter an anatomical sphincter rather than a physiological one?
Horse
79
How does the diaphragm aid in closure of the lower oesophageal sphincter?
There is higher pressure in the abdomen than the thorax. This causes the stomach to exert pressure on the diaphragm, thus re-enforcing closure
80
What are the 4 functions of the simple stomach?
Digestion-continuation of starch digestion, initiation of protein digestion
Protection-stomach acid kills bacteria ingested with food
Storage-ensures food is delivered to the SI at a controlled rate
Mechanical breakdown/mixing-breaks down food and mixes it with gastric juice to form chyme
81
How does motility occur in the stomach?
Peristaltic contractions start in fundus then propogate down corpus.
Pyloric sphincter open to allow chyme into duodenum.
When contractions reach pylorus, the pyloric sphincter closes.
Food is forced back into the corpus-helps mixing
82
Why is pepsinogen present in gastric juice as opposed to pepsin?
Pepsinogen=inactive form of pepsin
| As organs are made out of protein, pepsin needs to be inactive until it comes into contact with foreign protein
83
Which 3 substances stimulate the secretion of acid and gastric juices?
Acetylcholine
Histamine
Gastrin
84
How is the stomach mucosa protected from HCl?
Secretion of mucous layer
Epithelial cell membrane and interconnecting tight junctions (impenetrable to H+)
Epithelial cells are replaced every 2-3 days
85
What are the 4 layers of the GI tract?
Mucosa
Submucosa
Muscularis
Serosa
86
What are the 3 sub-layers of the mucosa of the GI tract?
Lamina epithelialis mucosae (glandular, increases SA)
Lamina propria mucosae (connective tissue layer)
Lamina muscularis mucosae (smooth muscle)
87
How is the stomach able to expand?
Mucosa layer is in folds to allow expansion
88
What does pancreatic juice contain?
Bicarbonate and digestive enzymes
89
What does a hepatic portal triad contain?
Hepatic artery
Hepatic portal vein
Bile duct
(+/- lymphatic vessel)
90
What are the 2 phases of digestion in the small intestine?
Luminal-enzymes are secreted by the salivary glands/pancreas
| Membranous-enzymes are attached to epithelial surface of intestinal cells
91
What are the 4 types of intestinal epithelial cells?
```
Goblet cells (secrete mucous)
Enteroendocrine cells (release of hormones)
Paneth cells (defence against microbes)
Enterocytes (absorption)
```
92
How do segmental contractions occur in the small intestine?
Circular contractions occur along distended intestine
Divides intestinal contents into small segments
New contractions occur in centre of distended segment
Repeated many times
Mixes contents with digestive juices
Moves contents towards mucosal surface for digestion/absorption
93
What is the name of the pacemaker cells that regulate mobility in the stomach and small intestine?
Interstitial cells of Cajal
94
How are glucose/galactose absorbed in the small intestine (from lumen into cells)?
Sodium-glucose co-transporter (SGLT1)
95
Which transporter enables glucose/galactose to diffuse from the small intestinal cells to the bloodstream?
GLUT2
| facilitative transporter
96
How are glucose and galactose absorbed into the bloodstream?
Secondary active transport from lumen into cells via SGLT1 (sodium-glucose co-transporter).
Sodium and glucose/galactose bind to transporter on luminal side.
Conformational change in transporter moves them into the cell and into cytosol.
Conc. of glucose/galactose within cytosol is high, so they diffuse down conc gradient into bloodstream via facilitative transporter GLUT2
97
How is fructose absorbed in the small intestine (from lumen into cells)?
GLUT5
| Diffuses into bloodstream via GLUT2
98
What are the end products of protein digestion?
Di/tri-peptides and amino acids
99
In neonates, what adaptions are present to enable absorption of intact antibodies?
Epithelial cells of intestine are permeable to intact protein
Stomach produces negligible amounts of HCl
Pancreatic enzyme secretion is low
Colostrum contains trypsin inhibitors
100
What is the main source of lipase?
Pancreatic juice
101
What are chylomicrons?
Mono-glycerides and FFAs are re-esterified in the ER to form tri-glycerides.
These coalesce with phospholipids and cholesterol to form chylomicrons.
102
What are the 2 main routes of water transport?
Para-cellular: across tight junctions between epithelial cells
Trans-cellular: across cell membranes via transporter proteins
103
How is iron transported in blood?
Binds with transferrin
104
What is active transport of calcium stimulated by?
Calcitrol
| Increases vitamin D-dependant synthesis of calcium-binding proteins (calbindin)
105
What are transporter proteins for water called?
Aquaporrins
106
What is iron bound to when in the cells?
Apoferritin to form ferritin
107
Why does the large intestine have no digestive enzymes?
Only digestion here is microbial
108
What are the 2 major cell types of the large intestine?
```
Colonocytes (absorptive, predominate at luminal surface)
Goblet cells (secrete mucous and HCO3-, predominate in crypts)
```
109
What is sodium absorption enhanced by?
Aldosterone
110
What is diarrhoea?
When water is lost in faeces through:
Increased secretion of water
Decreased absorption of water
Causes distension which increases motility, further reducing absorption
111
How would you treat nutritional diarrhoea?
Starve for 24 hours-rest the gut
| Bland diet for about 5 days to allow the gut lining to heal
112
What is present in intravenous fluids?
Fluid to maintain blood pressure and volume
Ions to replace excessive secretion/insufficient reabsorption
HCO3- to counteract metabolic acidosis caused by excessive HCO3- secretion/insufficient reabsorption
113
In the exocrine pancreas, where do the excretory ducts terminate?
Pancreatic duct
114
What is the function of somatostatin and where is it produced?
Inhibits insulin and glucagon secretion
| Produced by delta cells in Islets of Langerhans in endocrine pancreas
115
What are:
Gluconeogenesis
Glycogenolysis
```
Gluconeogenesis= formation of glucose from non-carbohydrate substrates
Glycogenolysis= breakdown of glycogen to glucose
```
116
How is insulin deactivated in the liver?
Cleavage of di-sulphide bonds
117
What are the main actions of insulin?
Increases amino acid uptake, triglyceride synthesis, protein synthesis, glycogen synthesis, glucose uptake.
Decreases gluconeogenesis.
Decreases blood glucose
118
Describe how the ionic composition of pancreatic juice is achieved?
HCO3- is actively transported into the duct lumen in exchange for Cl-
Water follows by osmosis
H+ is transported into bloodstream, negates alkaline tide
119
What are the 4 lobes of the liver?
Right (medial and lateral)
Left (medial and lateral)
Quadrate
Caudate (papillary process and caudate process)
120
In which species is the gall bladder absent?
Horse
121
What is the Bile Canaliculus?
Dilate inter-cellular space between cells.
| Bile is secreted across the canalicular membrane
122
All substances absorbed from the GI organs pass through the liver via which vessel?
Hepatic portal vein
123
What is the function of bile?
Aids digestion of lipids by lipase
124
What is haem broken down into in the liver?
Bilirubin, excreted in bile
125
What are the 3 functions of bile?
Exit route for waste products and drugs
Promotes hydrolysis of lipases (emulsifies them)
Facilitates intestinal absorption of lipids (micelles)
126
Where is bile emptied into the duodenum?
At the major duodenal papilla, controlled by Sphincter of Oddi
127
What happens to glucose in the liver?
Stored as glycogen until glycogen reaches 5% of total liver mass
Remaining glucose is then converted to tri-glycerides
Some stored in liver, most exported to blood as VLDL (very low-density lipoproteins)
128
What happens to urea formed by amino acids in ruminants?
Secreted in saliva
Transferred to fore-stomach and LI
Microbial protein synthesis
Excess excreted by kidneys
129
In herbivores, which acid is the only VFA that can serve as a pre-cursor for gluconeogenesis/ be converted to glucose?
Propionic acid
130
How are VLDL (very low-density lipoproteins) synthesised in:
Absorptive state
Post-absorptive state
Absorptive state: synthesised from excess glucose
| Post-absorptive state: synthesised from plasma FFA
131
What are the 3 nutritional strategies/types of feeders in ruminants?
Browsers-concentrate selectors eg deer
Grazers-grass/roughage eaters eg cattle, sheep
Intermediates-adaptable feeders eg goats
132
What is the function of the oesophageal/ventricular groove?
Allows milk to bypass the fermentation chamber in all young ruminants.
Remains functional in browsers but not grazers
133
Where is the site of glucose absorption in ruminants?
SI, via SGLT1
134
What is meant by regurgitation?
Passive transfer of stomach contents to oral cavity for re-mastication
135
What is the definition of rumination?
The entire process of regurgitation, re-mastication and re-deglutition (chewing the cud)
136
What do the papillae in the rumen absorb?
VFAs, ions, water
137
What epithelium is present in the abomasum?
Columnar epithelium with glands
138
What epithelium is present in the fore-stomach?
Stratified squamous (keratinised stratum corneum)
139
What is the difference between primary contractions and rumination contractions?
An extra reticular contraction precedes the normal biphasic reticular contractions
(Normal primary contractions then follow)
140
How many times a day does rumination occur?
| When does it occur?
6-10 times per day, requiring approx 60 mins/kg roughage eaten
Occurs at night and afternoon rest period
141
What is a problem regarding ruminants eating fresh clover?
Results in small bubbles that don't coalesce and form a foam that doesn't collect in the dorsal sac-"frothy bloat"-hence can't be eructated.
142
Which receptors do sensory cells in the ruminant fore-stomach contain?
Mechano- and chemo-receptors
| Tension receptors
143
How do tension receptor cells affect motility in the ruminant stomach?
Increase motility
144
How do mechano- and chemo-receptor cells affect motility in the ruminant stomach?
Decrease motility
145
What causes closure of the oesophageal groove?
Sucking and chemoreceptors in the pharynx
146
What are the 5 types of bacteria in the rumen?
```
Amylolytic
Cellulolytic
Methanogenic
Proteolytic
Lactate-utilisers
```
147
How can propionate be formed in the ruminant?
From lactate
| Anaerobic glycolysis of pyruvate
148
Protein is degraded by ruminal bacteria into what?
Amino acids
Peptides
NH3 and organic ions
Branched fatty acids
149
What are the caecum and colon separated by in the horse?
Caeco-colic valve
| Ensures no retrograde flow from colon to caecum
150
What is the gut transit time in fore-gut and hind-gut fermenters?
Fore-gut: 24 hours
| Hind-gut: several days
151
In an equine rectal examination, how would you identify a small intestine obstruction?
Normally can't feel SI as empty
If SI is distended by gas=obstruction
Large colon feels hard as it is dehydrated as a result
152
In an equine rectal examination, how would you detect an ileal impaction?
Firm tubular structure in centre of abdomen, coursing towards caecum
153
In an equine rectal examination, how would you identify a caecal impaction?
Taenia become more taut
| Caecum displaced more to midline
154
In an equine rectal examination, how would you identify a large colon impaction?
Occurs at pelvic flexure
Obvious palpable mass in left ventral quadrant
Large colon is enlarged
155
In an equine rectal examination, how would you identify a large colon volvulus/torsion?
(volvulus=loop of bowel is twisted)
Abdomen visible distended
Large colon fills entire abdomen
Colon distended
Volvulus occurs before torsion
156
In an equine rectal examination, how would you identify a small colon impaction?
Caecal and colonic tympani
Solid ingesta palpable in small colon
Faecal balls no longer evident
157
Where is the spleen located in the abdomen?
Left cranial abdomen
158
What are the roles of the spleen?
Lymphocyte production
Blood storage
Phagocytosis of foreign material and damaged red blood cells
159
Through which vessel does the spleen receive its blood supply?
Splenic artery
160
Through which vessel does venous drainage of the spleen occur?
Splenic vein, leads into portal vein
161
What is the function of the thymus in the young animal?
Develops immunocompetence
162
In the thymus, what do the cortex and medulla produce?
Cortex produces T lymphocytes
| Medulla contains epithelial cells which are the source of thymosin (causes maturation of T cells)
163
Give the steps of rumination
Thorax expands, negative pressure in oesophagus
Lower oesophageal sphincter opens
Diaphragmatic muscle contractions force material into oesophagus
Reverse peristaltic contractions to oral cavity
Liquid immediately re-swallowed, additional salivary secretion, re-swallowed
164
What happens in the ruminant stomach during secondary contractions?
```
Eructation
Caudo-dorsal blind sac contracts forward, pushing contents into cranial blind sac and ventral sac
Dorsal sac contracts, gas moves to oesophageal opening
Increased negative pressure in thorax
Oesophagus expands
Cardiac sphincter opens
Reverse peristalsis
Gas escapes via mouth or is inhaled
```
165
Abnormal sounds in colic
Increased frequency: enteritis, spasmodic colic
Tympanitic: gut obstruction, gut distension (gas)
Decreased frequency: ileus, gut obstruction
166
Normal horse abdomen sounds
Left dorsal: SI/small colon, high pitch, fluidy
Left ventral: pelvic flexure
Right dorsal/ventral: caecum, loud, toilet flushing, emptying of caecum via caeco-colic valve
