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DVM 521 - PHYSIO II > Gastrointestinal Physio L1-3 > Flashcards

Gastrointestinal Physio L1-3 Flashcards

1
Q

What is the digestive system composed of?

A
  • GI tract - concentric muscle clinders lined w/an epithelium (from esophagus to rectum)
  • Accesory organs - teeth, tongue, salivary glands, liver, pancreas
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2
Q

Name acessory organs of the digestive system.

A

Teeth, tongue, salivary glands, liver, pancreas

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3
Q

True or False. The proximal stomach has many contractions and serves to break down food.

A

False
* The proximal stomach serves as a storage.
* The gastric pump contracts and mixes the food w/acid and enzymes.

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4
Q

Explain the general route of which food travels through the digestive system.

Include hypotheticals from a ruminant.

A
  • Salivary glands produce the first secretion of the GI
  • Then moves to fermentation chamber in ruminants (omasum, rumen, & reticulum)
  • Then to stomach (abomasum)
  • Receives secretions from liver, gallbladder, and pancreas
  • Then small intestine to colon to rectum
  • The nutrients travel into blood and unwanted stuff travel to lymphatics
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5
Q

What are identifying characteristics for carnivore GI tracts?

A

A big stomach and a relatively short GI tract.
* proximal part for food storage

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6
Q

What are identifying characteristics for ruminant GI tracts?

A

Fermentation in the forestomachs
* prior to the abomasum (true stomach)
* Rumen is the huge fermentation chamber (reticulum & omasum other components)

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7
Q

What are identifying characteristics for equine GI tracts?

A

Fermentation in the large intestine
* Horses = Simple-stomached herbivores
* Small stomach, huge large intestine

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8
Q

What are identifying characteristics for avian GI tracts?

A

Food storage (the crop), a glandular stomach (pro-ventriculus), and a muscular stomach (gizzard)
* crop + pro-ventriculus + gizzard = true stomach of a monogastric animal

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9
Q

What are the major functions of the GI tract?

A
  • Transportation of food
  • Secretion of digestive juices & digestion of food in absorbable particles
  • Absorption of food components & transport into the blood
  • Regulation of water & electrolyte balance
  • Immunologic barrier (GALT)
  • Thermoregulation (fluid intake, panting in dogs)
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10
Q

What is prehension?

A

How food is grabbed. Each species differ in feeding behaviors.

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11
Q

How does prehension occur in Horses?

A

Lips (when eating from manger) or incissors (when grazing)

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12
Q

How does prehension occur in Cattle?

A

Tongue (wrap the tongue around forage) & incissors

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13
Q

How does prehension occur in Goat & Sheep?

A

Tongue & Lips

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14
Q

How does prehension occur in Pigs?

A

Snout & Mandible

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15
Q

How does prehension occur in carnivorous animals?

A

Canines, incisors, and forelimbs.

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16
Q

What is mastication?

A

The first act of digestion, involves the actions of the teeth, jaws, tongue, and cheecks.

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17
Q

What are the key features of mastication in carnivorous animals?

A
  • Very sparsely, movement of the mandible are vertical
  • Molars & premolars in the upper & lower jaws move against each other like scissor blades
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18
Q

What are the key features of mastication in herbivorous animals?

A
  • Spend a long time masticating
  • Upper & lower jaws are large, providing room for teeth w/large chewing surfaces
  • Mastication movements are horizontal
  • Ruminants –> Regurgitation, Remastication
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19
Q

True or False. When carnivores chew, they mostly use their canines.

A

False
* Canines are used to hunt/kill
* Carnassials are used to eat & act like scissors

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20
Q

How does the structure of herbivorous teeth allow for a lot of chewing?

A
  • Enamel is the hardest material in body
  • Folds provide inner cutting surface
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21
Q

During/after mastication, ____________ of different GI tract segments is activated.
a. ridgidity
b. absorption
c. storage
d. motility

A

(D) - During/after mastication, MOTILITY of different GI tract segments is activated.

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22
Q

What are the functions of movements of the GI tract?

A
  • To propel ingesta from one location to the next
  • To retain ingesta at a given site for digestion, absorption, or storage
  • To break up food material physically & to mix it w/digestive secretions
  • To circulate ingesta so that all portions come in contact w/absorptive surfaces
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23
Q

DOUBLE CHECK WHERE THIS IS ???

What type of meal moves through the GI tract quicker, a hypocaloric meal or a hypercaloric meal?

A

Hypocaloric meal - less to digest

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24
Q

What is Deglutition?

A
  • The first motility pattern in the GI tract is the deglutition
  • Deglutition involves voluntary & involuntary stages & occurs after food has been masticated
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25
Q

What occurs in the voluntary phase (oral phase) of deglutition?

A
  • Food is in the oral cavity & is molded into a bolus
  • Using the tongue it will be pushed back into the pharynx
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26
Q

What occurs in the involuntary phase (swallow reflex) of deglutition?

A
  • It occurs within the pharynx & esophagus –> it directs food into the digestive system (away from the upper airways)
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27
Q

True or False. During deglutition, breathing stops momentarily.

A

True

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28
Q

Explain the step-by-step process of deglutition.

A
  1. The soft palate is elevated closing the pharyngeal opening of the nasopharynx preventing that food gets into the internal openings of the nostrils
  2. The tongue is pressed against the hard palate closing off the oral opening
  3. the epiglottis is moved backwards covering the entrance to the trachea preventing the movement of food into the respiratory system
  4. The upper esophageal sphincter opens & the food is transported through the esophagus by peristaltic contractions; the entrance to the trachea is reopened & respiration continues
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29
Q

How long is the transit time in dogs from the oral cavity to stomach?

A

4-5 seconds

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30
Q

What are some disorders of deglutition?

A

Dysphagia - difficulty in swallowing which may result from neuromuscular disorder or mechanical obstruction

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31
Q

What are the classification of Dysphagia?

2 distinct types + additional

A
  • Oropharyngeal Dysphagia - Due to malfunction of the pharynx & upper esophageal sphincter
  • Esophageal Dysphagia - Due to malfunction of the esophagus
  • Aspiration - A dysphagia in which food particles/fluids or stomach contents (acid reflux) reach the upper airways
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32
Q

Why is aspiration harmful?

A

B/C the airways are not protected from the acidity of the GI system

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33
Q

What is the regulatory center for energy homeostasis?

A

Hypothalamus

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34
Q

What is within the hunger center?

A

Nucl. paraventricularis, lateral hypothalamus fields, perifornical region

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35
Q

What is within the satiety center?

A

Nucl. ventromedialis

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36
Q

What are the stimulatory neuropeptides (Hunger) from the hypothalamus?

A

Neuropeptide Y (NPY) & Orexin

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37
Q

What are inhibitory (Satiety) neuropeptides from the hypothalamus?

A

Melanocyte-stimulating hormone (MSH)
* Inhibits hunger & increases energy consumption
* Think of Labradors

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38
Q

What are stimulatory (Hunger) non-hypothalamic hormones?

A

Ghrelin

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39
Q

What are inhibitory (Satiety) non-hypothalamic hormones?

A

Cholecystokinin (CCK), Peptide YY (PPY), Leptin (fat cells –> inhibits NPY release & activates MSH release & activity), Insulin (pancreas –> glucose availability)

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40
Q

What are the major salivary glands?

A
  • Parotis (parotid gland)
  • Mandibularis (madibular gland)
  • Sublingualis (sublingual gland)
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41
Q

What are the small salivary glands?

A
  • Ventral jaw glands
  • Palate, pharyngeal glands
  • Lips glands (labiales)
  • Zygomatic glands
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42
Q

What are the types of secretions?

A
  • Serous
  • Mucous
  • Seromucous (mixed)
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43
Q

Which salivary glands provide the largest amount of secretion?

A

Parotis & Mandibularis account for 90% of salivary secretion.

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44
Q

What are the primary functions of saliva (digestive functions)?

A
  • Protection of the bucal mucosa & teeth
  • Facilitation of deglutition
  • Initiation of enzymatic carbohydrate digestion (human & pigs –> amylase, destroys cellulose)
  • pH regulation (HCO3-, bicarbonate)
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45
Q

What are the secondary functions of saliva?

A
  • Immunologic function (Lysozyme, Ig’s)
  • Thermoregulation (panting in dogs)
  • Defense mechanism in some species (llamas, alpacas - spit w/high accuracy)
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46
Q

True or False. Cattle produce 60-160 L of saliva per day.

A

True

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47
Q

According to the research article, what breed of dogs is more likely to have problems w/weight & appetite?

A

Labrador retrievers & related Flat coat retrievers

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48
Q

According to the research article, a mutation in what gene causes an association w/greater weight, adiposity, & food motivation?

What neuroactive peptides are disrupted?

A
  • Gene = POMC
  • The mutation is predicted to disrupt the production of the neuroactive peptides β-MSH and β-endorphin. These are implicated in energy homeostasis
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49
Q

True or False. The POMC mutation is more often found in service dogs than average companion animals.

A

True
* B/C a highly food-motivated dog is more easily trained w/treats using positive reinforcement

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50
Q

According to the article, what signaling pathway is crucial for the appropriate control of food intake w/genetic disruption of most components of the pathway resulting in severe obesity in both mouse & man?

A

Hypothalamic leptin melanocortin

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51
Q

What makes up saliva?

A

99% water & 1% electrolytes (Na+, K+, Cl-, HCO3-)

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52
Q

In the salivary gland, what is produced in the ducts?

A

Secondary saliva (K+ and HCO-)

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53
Q

In the salivary gland, what is produced in the acinus (glandular epithelium)?

A

Primary saliva (Cl-, Na+, H2O)

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54
Q

What can be caused by disturbances in saliva production?

A
  • Xerostomia (dry mouth)
  • Bucal ulcers
  • Dysphagia
  • Proliferation of bacterial population
  • Cavities
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55
Q

How is saliva secretion regulated by the parasympathetic system?

A

Parasympathetic system (N. facialis und glossopharyngeus) acts on M3-receptors causing the contraction of myoepithelial cells to increase saliva secretion. This dilutes the saliva as it is being emptied faster.

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56
Q

How is saliva secretion regulated by the sympathetic system?

A

Sympathetic system (3 first thoracal segments) acts on α-1receptors (by Epi and NEpi) and causes secretion of small volumes of consistent (mucous) saliva

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57
Q

How is the innate (reflex) of saliva secretion stimulated?

A

Through contact w/bucal mucosa (mechanoreceptors)

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58
Q

How is the conditioned saliva secretion stimulated?

A

Through sight, smell, or immagination of food.
* i.e. Close eyes and imagine lemon

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59
Q

Explain Ivan Pavlov’s experiment w/the conditioned stimulus.

A
  • Bell = Salivation
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60
Q

What are the four routes of secretion of the GI tract reach their target tissue?

A
  • Endocrine
  • Paracrine
  • Autocrine
  • Neurocrine
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61
Q

________________ secretions are deposited close to blood vessels, and then blood carries the substances to their target tissues.
a. Paracrine
b. Autocrine
c. Neurocrine
d. Endocrine

A

(D) Endocrine secretions are deposited close to blood vessels, and tehn blood carries the substances to their target tissues.

62
Q

________________ substances diffuse through the interstitial space to affect other cells.
a. Paracrine
b. Autocrine
c. Neurocrine
d. Endocrine

A

(A) Paracrine substances diffuse through the interstitial space to affect other cells.
* NEVER reaches bloodstream

63
Q

________________ substances of a given cell regulate functions of the same cell.
a. Paracrine
b. Autocrine
c. Neurocrine
d. Endocrine

A

(B) Autocrine substances of a given cell regulate functions of the same cell.

64
Q

________________ refers to secretions by enteric neurons that affect muscle cells, glands, and blood cells.
a. Paracrine
b. Autocrine
c. Neurocrine
d. Endocrine

A

(C) Neurocrine refers to secretions by enteric neurons that affect muscle cells, glands, and blood cells.
* NEED a nerve

65
Q

What is the criteria for a hormone to be a hormone (& not just a peptide)?

A

A hormone must…
* Be secreted by one cell & affect another
* Be transported in the blood
* Be stimulated by food & its action must be mimicked by a synthetic analog molecule

66
Q

What are the big 5 GI hormones?

A
  • Secretin
  • Gastrin
  • CCK (Cholecystokinin)
  • GIP (Gastric Inhibitory Polypeptide)
  • Motilin
67
Q

What are the big 5 GI hormone synthesis sites?

A
  • Antrum
  • Duodenum
  • Jejunum
  • Ileum
68
Q

Where is secretin synthesized?

A

Duodenum & Jejunum

69
Q

Where is gastrin synthesized?

A

Antrum & Duodenum

70
Q

Where is CCK (Cholecystokinin) synthesized?

A

Duodenum, Jejunum, & Ileum

71
Q

Where is GIP (Gastric Inhibitory Polypeptide) synthesized?

A

Duodenum & Jejunum

72
Q

Where is Motilin synthesized?

A

Duodenum & Jejunum

73
Q

What is the action and stimuli of secretin?

A
  • Action: Stimulates bicarbonate secretion & inhibits acid secretion
  • Stimulus: Acid, fat, & protein
74
Q

What is the action and stimuli of gastrin?

A
  • Action: Stimulates acid secretion
  • Stimulus: Protein, high pH
75
Q

What is the action and stimuli of Cholecystokinin (CCK)?

A
  • Action: Stimulates pancreatic enzyme secretion & gallbladder contraction
  • Stimulus: Fats & proteins
76
Q

What is the action and stimuli of GIP (Gastric Inhibitory Polypeptide)?

A
  • Action: Inhibits gastric secretion & stimulates insulin secretion
  • Stimulus: Fats & glucose
77
Q

What is the action and stimuli of motilin?

A
  • Action: Induction of intestinal motility during fasting (MMC)
  • Stimulus: Acetylcholine
78
Q

What are the 4 sections of the monogastric stomach?

A
  • Esophageal part
  • Cardia
  • Fundus & Corpus
  • Pylorus
79
Q

Which section of the monogastric stomach is larger in horses?
a. Esophageal part
b. Cardia
c. Fundus & Corpus
d. Pylorus

A

(A) Esophageal

80
Q

Which section of the monogastric stomach is larger in pigs?
a. Esophageal part
b. Cardia
c. Fundus & Corpus
d. Pylorus

A

(B) Cardia

81
Q

What are the 3 glandular zones of the stomach and their secretions?

A
  • Cardias –> Mucus
  • Fundus –> HCl, Enzymes
  • Pylorus –> Mucus
82
Q

Which animal secretes the most gastric acid?
a. dogs
b. humans
c. pigs
d. horses

A

(D) Horses

83
Q

What are gastric pits?

A

The glandular mucosa of the stomach has invaginations, the gastric pits lined w/mucus-secreting cells at the luminal surface.

84
Q

________ cells produce a thick mucus to protect the stomach from the acid.
a. Mucous neck cells
b. Chief cells
c. Parietal cells
d. Surface mucous cells

A

(D) Surface mucous cells produce a thick mucus to protect the stomach from the acid.

85
Q

________ cells are located in the neck of the gastric glands and secrete HCl.
a. Mucous neck cells
b. Chief cells
c. Parietal cells
d. Surface mucous cells

A

(C) Parietal cells are located in the neck of the gastric glands and secrete HCl.

86
Q

________ cells secrete proteolytic enzyme precursors such as pepsinogen.
a. Mucous neck cells
b. Chief cells
c. Parietal cells
d. Surface mucous cells

A

(B) Chief cells secrete proteolytic enzyme precurosrs such as pepsinogen.

87
Q

________ cells are a progenitor cell for gastric mucosa. They secrete thin mucus unless they differentiate into one of the other cells.
a. Mucous neck cells
b. Chief cells
c. Parietal cells
d. Surface mucous cells

A

(A) Mucous neck cells are a progenitor cell for gastric mucosa. They secrete thin mucus unless they differentiate into one of the other cells. STEM CELLS

88
Q

True or False. Each gastric gland leads into a deep gastric pit.

A

False
* Each gastric pit leads into a deep gastric gland

89
Q

What is the importance of intrinsic factor (IF, a glycoprotein) secreted by parietal cells?

A

Essential for vitamin B12 absorption in the ileum.
* gastric glands & mucous cells

90
Q

True or False. All functional cell types of the gastric pit originate from mucous neck cells in the neck of the gland.

A

True
* Mucous neck cell = Stem cell

91
Q

What do enteroendocrine cells secrete?

A

Secrete hormones and paracrine messengers that regulate digestion
* gastrin

92
Q

How do parietal cells secrete HCl (mechanisms involved & structures that help)?

A
  • Inside the cell, there is a hydration reaction that will produce bicarbonate & a proton from water & carbon dioxide
  • The proton can either be secreted to form HCl or it can be used to bring Na+ in
  • There is an antiporter that brings Cl- into the cell & releases bicarbonate, the Cl- can be released to form the HCl
  • There is a Na+, K+, ATPase as well, which pumps Na+ out and brings K+ in, although there is a channel that allows leakage of K+
  • Parietal cells have a lot of intercellular canaliculi to increase SA for secretion
93
Q

Why is HCl important in nature?

A
  • Acid is important to start digestion
  • Animals that eat bone need HCl to break down and demineralize it so it will not cause any issues & can be digested
94
Q

How is the structure of a chief cell related to its function and what they secrete? How is it different in calves and lambs?

A
  • The chief cell has a defined Golgi apparatis & RER
  • **It secretes pepsinogen **(proenzyme or zymogen) which is activated in the acidic pH into pepsin called autoproteolysis and the pepsin will perform hydrolysis of proteins.
  • In calves and lambs, the cells secrete prochymosine. This turns into chymosine in the acidic pH of the abomasum. This does hyrolysis of milk protein.
95
Q

What are enteroendocrine cells?

A
  • Old name = enterochromaffine
  • Current name describes the function of theses cells which is secretion of endocrine substances
  • They are names according to the hormone they produce
96
Q

What are some enteroendocrine cells and their secretions?

A
  • G cells –> Gastrin
  • D cells –> Somatostain
  • I cells –> CCK
97
Q

Where do enteroendocrine cells secrete their granule content and where do they go from there?

A

They secrete their granule content (gastrin, histamin, somatostain) into the lamina propria. From there, some will reach the blood capillaries and travel to other parts of the GI tract.

98
Q

What are mucins?

Mucus-producing cells

A

Glycoproteins secreted by exocytosis.
* Nt & Ct possess serveral Cysteine residues –> Disulfide bridges btwn monomers –> Protection & lubrication of the mucosa

99
Q

How long do surface mucus cells live?

A
  • Regenerate every 3-5 days
  • Do not live long
  • ↑ mitotic activity in the isthmus of the gastric pit
100
Q

What are the purpose of mucus cells?

A

Protection and lubrication of the mucosa

101
Q

What are the 3 levels that regulate HCl?

A
  • Neural (mediated by acetylcholine)
  • Hormonal (mediated by gastrin & somatostain)
  • Paracrine (mediated by histamine)
102
Q

REWORD???

For each stimulatory substance, what is the mediator for HCl secretion to be regulated?

A
  • Acetylcholine –> Vagus nerve
  • Histamine –> Enterochromatin like cells (ECL)
  • Gatrin –> Vagus nerve
103
Q

REWORD???

What is released from D cells that inhibits gastrin production?

A

Somatostatin –> D cell
* endocrine regulation
* inhibitory substance = somatostain

104
Q

At what pH is HCl production inhibited?

A

< 3 (less than 3)

105
Q

What kind of feedback mechanism is the HCl secretion of parietal cells?

neg/pos

A

Negative feedback mechanism

106
Q

How is gastric acid secretion related to the ATPase pump under resting conditions?

A

The H+, K+, ATPase has limted access to the apical membrane

107
Q

What occurs in the apical membrane after acid secretion?

Stimulated Cell

A

Canaiculi fuse w/the apical (luminal) membrane and vesicles containing H+, K+, ATPase are targeted to the apical membrane increasing HCl secretion.

108
Q

What are the 2 levels that stimulate the secretion of gastric enzynes?

A
  • Neural (Ach, NA)
  • Hormonal (Secretin, CCK)
109
Q

What is released from the small intestine when food particles are present?

A

CCK & Secretin
* amino acids & fatty acids –> CCK
* ↓ pH –> Secretin

110
Q

True or False. Mucus secretion is dramatically altered by the presence of food as gastric acid and enzymatic secretion.

A

False
* Mucus secretion is NOT dramatically altered by the presence of food as gastric acid and enzymatic secretion.

111
Q

What substances stimulate mucus secretion?

A

Ach & Prostaglandine E
* ↓ pH stimulate produce of mucus

112
Q

What is the reason that NSAIDs would cause gastric ulcers?

A
  • NSAIDs block the synthesis of prostaglandines as well as several important processes in the gastric mucosa promoting the formation of gastric ulcers.
  • NSAIDs block COX-1 & COX-2 which normally lead to the formation of prostaglandins & leukotrines. So w/out the mucus production decrease, a gastric ulcer can form.
113
Q

True or False. After 3 days on NSAIDs a generally healthy patient is at high risk for a gastric ulcer.

A

False
* It would be with long term use of NSAIDs

114
Q

What does removing COX-1 cause and how can it further worsen gastric ulcers?

A
  • Impairs healing via reduced mucosal blood flow
  • Imparied platelet aggregation
  • Increased bleeding/injury
115
Q

What does removing COX-2 cause and how can it further worsen gastric ulcers?

A
  • Reduced angiogenesis
  • Reduced leukocyte adherence and increased leukocyte activation
  • Increased bleeding/injury
116
Q

What is the pH of gastric acid?

A

1-4

117
Q

What is the function of gastric acid?

A

Acts as a defense system for killing microorganisms.

118
Q

How does H. Pylori evade being destroyed by the gastric acid?

A
  • Colonization of the mucosa (burrows under the mucosal layer)
  • Produces urease which neutralizes acidic pH, thus making the environment more bacteria friendly. This also will destroy the mucus production & the stomach acid will destroy the GI cells.
  • Urease rxn = H2N-CO-NH2 + H2O –> 2NH3 + CO2 –> Neutral microenvironment
119
Q

What is the pH in the proximal part of the stomach in horses & pigs?

A

4-6

120
Q

How are gastric ulcers formed in horses & pigs?

A
  • pH 4-6 making them more prone to colonization of bacteria
  • Leads to hydrolysis of carbohydrates in short chain fatty acids & lactate resulting a more acidic pH, which can damge the mucosa & cause gastri ulcers.
  • This condition is seen more in horses under more stress, such as competition horses which have a 60-90% prevalence, where grazing horses only have a 10% prevalence of ulcers.
121
Q

What are the 3 phases of gastric secretion?

A
  • Cephalic
  • Gastric
  • Intestinal
122
Q

What occurs during the cephalic phase of digestion?

A
  • Before food enters the stomach
  • Stimulated by sight, smell, thought or taste
  • The greater the appetite, the stronger the stimulation
  • Stomach acid is increased due to chief cells releasing pepsinogen & parietal cells secreting HCl b/c of nerve impulses from vagal nerve
  • Gastrin is in blood & indicates the need for more HCl release from parietal cells to prepare for digestion
123
Q

What occurs during the gastric phase of digestion?

A
  • Induced by vagovagal reflexes from the stomach to the brin (through dilatation of the stomach & through the presence of amino acids & peptides in the GI lumen)
  • Presence of peptides in stomach –> cause gastrin producing cells to generate gastrin in the blood which increases the secretion of parietal cells & chief cells to make HCl & pepsinogen respectively
124
Q

What occurs during the intestinal phase of digestion?

A
  • Induced by the presence of food in the duodenum (it works as a feed back)
  • Food makes it to the duodenum & this causes the cycle to repeat due to the presumption more food is going to be coming through the stomach
125
Q

True or False. The small intestine mucosa has a small surface area.

A

False
* The small intestine mucosa has a large surface area.

126
Q

What are the 3 levels of surface convolutions of the small intestine to expand surface area?

A
  • Plicae circulares (in some species)
  • Villi (finger-like epithelial projections)
  • Microvilli
127
Q

What is the name of the gland like structure at the base of the villi of the small intestine?

A

Crypts of Lieberkühn

128
Q

What type of cells are found at the crypts of Lieberkühn?

A
  • Paneth cells
  • Endocrine cells
  • Stem cells
  • Goblet cells
129
Q

What is the secretion of enterocytes/absortptive cells?

A
  • Absorptions of nutrients
  • Secretion of digestive enzymes as well as water, Cl-, & HCO3-
130
Q

What are the secretions of goblet cells?

A

Secretion of mucus

131
Q

What are the secretions of enteroendocrine cells?

A
  • Hormones such as CCK, secretin, & GIP
  • Usually different enteroendocrine cells secrete different substances, not just one cell type secreting all 3
  • Secrete into lamina propria & eventually into blood vessels
132
Q

What are the secretion of paneth cells?

A

Secrete antimicrobial enzymes & peptides that are located in vesicles

133
Q

What are brunner’s glands (function & secretion product)?

A
  • Tubulo alveolar glands (submucosa)
  • Secretion of mucus through exocytosis
  • Secrete glycoproteins & bicarbonate ions (pH of Brunner glands’ secretion is 8.1-9.3)
  • Function is to protect the small intestine mucosa by neutralizing the acid containing chyme delivered to it from the stomach
134
Q

What structures or parts of the small intestine have an immune role?

A
  • Mucus layer is the forst barrier of protection
  • DCs live in the villi
  • Peyer’s patches in the ileum have phagocytic cells
135
Q

True or False. Division and replication of enterocytes occurs in the crypts only.

A

True
* Intestinal crypt cells are among the most rapidly regenerating cells of the body.
* As crypt cells multiply, they migrate upward the villi

136
Q

What is the turnover time of enterocyte regeneration?

A

4-7 days

137
Q

What determines the length of the villi in the small intestine?

A
  • The lenth of villi is determined by the rate at which cells are lost at the tips & at the rate at which they are replaced.
  • An increase in cell loss at the villi tips, relative to the crypt cell replication, results in shortening of the villi.
138
Q

What do progenitor cells arise from?

A

The stem cell compartment and differentiate into absorptive enterocytes or secretory goblet, enteroendocrine, or paneth cells.

139
Q

When the progenitor cells are differentiated into the needed cell, what occurs? What is the exception?

A
  • Most of the differentiated cell populations migrate up the villi.
  • The Paneth cells move downward into the crypt and reside between the crypt base columnar cells.
140
Q

What is the mediator of water secretion in the small intestine?

A

Osmosis

141
Q

What can cause food to be hyperosmotic and how does the small intestine accomodate for that?

A

Food entering the intestine may be hyperosmotic (salty foods & foods w/high sugar contents) or become hyperosmotic after digestion (starchy meal); osmotically active substances draw water from the lateral spaces into the intestinal lumen.

142
Q

As solutes are absorbed in the small intestine, how does water move?

A

Water follows them osmotically back through the epithelium and into the vascular system reaching the blood stream.

143
Q

In general what direction does water move in the small intestine?

A

Water will move in whatever direction to keep ingesta isosmotic.

144
Q

What animals have the highest dry weight of the large intestine?

A
  • Horse
  • Rabbit
  • Guine pig
145
Q

What are the components (& important information) about the large intestine?

A
  • Microbial metabolism (significant in horses & rabbits)
  • One layer cylindric epithel (crypts are also present)
  • Water absorption & vitamins
  • Goblet cells produce mucus
  • Secretion: small volumen, isotonic - isoton to plasma, mucin, bicarbonate & potassium rich (alkaline)
146
Q

What is a large difference between mucosa within the small intestine and the mucosa of the large intestine?

A

The mucosa is composed of crypts but not villi lined by goblet cells (mucus) and some absorptive epithelial cells (absorption of some electrolytes & water)

147
Q

Where do water & nutrients go before entering the vascular system?

A

Water & nutrients first enter the extracellular fluid before entering the vascular system.

148
Q

What forces are responsible for driving the movement of solutes and water between intravascular & extravascular fluids?

A

Osmotic and hydrostatic forces (starling forces)

149
Q

How do absorbed nutrients enter the capillaries?

A

Absorbed nutrients enter the capillaries by diffusion from the interstitium (this drives water to the capillaries too)

150
Q

Where does venous blood from the GI tract collect?

A
  • The hepatic portal vein & passes through the liver before entering the vena cava & returning to the heart.
  • Not including the terminal colon and rectum
151
Q

True or False. Lymphatic drainage from the gut passes through the liver & then is reentered into circulation.

A

False
* Lymphatic drainage from the gut bypasses through the liver entering the bloodstream through the thoracic duct.

DVM 521 - PHYSIO II (6 decks)

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