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
2
Q
Name acessory organs of the digestive system.
A
Teeth, tongue, salivary glands, liver, pancreas
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.
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
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
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)
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
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
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)
10
Q
What is prehension?
A
How food is grabbed. Each species differ in feeding behaviors.
11
Q
How does prehension occur in Horses?
A
Lips (when eating from manger) or incissors (when grazing)
12
Q
How does prehension occur in Cattle?
A
Tongue (wrap the tongue around forage) & incissors
13
Q
How does prehension occur in Goat & Sheep?
A
Tongue & Lips
14
Q
How does prehension occur in Pigs?
A
Snout & Mandible
15
Q
How does prehension occur in carnivorous animals?
A
Canines, incisors, and forelimbs.
16
Q
What is mastication?
A
The first act of digestion, involves the actions of the teeth, jaws, tongue, and cheecks.
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
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
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
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
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.
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
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
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
25
What occurs in the voluntary phase (oral phase) of deglutition?
* Food is in the oral cavity & is molded into a bolus
* Using the tongue it will be pushed back into the pharynx
26
What occurs in the involuntary phase (swallow reflex) of deglutition?
* It occurs within the pharynx & esophagus --> it directs food into the digestive system (away from the upper airways)
27
True or False. During deglutition, breathing stops momentarily.
True
28
Explain the step-by-step process of deglutition.
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
29
How long is the transit time in dogs from the oral cavity to stomach?
4-5 seconds
30
What are some disorders of deglutition?
**Dysphagia** - difficulty in swallowing which may result from neuromuscular disorder or mechanical obstruction
31
What are the classification of Dysphagia?
| 2 distinct types + additional
* **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
32
Why is aspiration harmful?
B/C the airways are not protected from the acidity of the GI system
33
What is the regulatory center for energy homeostasis?
Hypothalamus
34
What is within the hunger center?
Nucl. paraventricularis, lateral hypothalamus fields, perifornical region
35
What is within the satiety center?
Nucl. ventromedialis
36
What are the stimulatory neuropeptides (Hunger) from the hypothalamus?
Neuropeptide Y (NPY) & Orexin
37
What are inhibitory (Satiety) neuropeptides from the hypothalamus?
Melanocyte-stimulating hormone (MSH)
* Inhibits hunger & increases energy consumption
* Think of Labradors
38
What are stimulatory (Hunger) non-hypothalamic hormones?
Ghrelin
39
What are inhibitory (Satiety) non-hypothalamic hormones?
Cholecystokinin (CCK), Peptide YY (PPY), Leptin (fat cells --> inhibits NPY release & activates MSH release & activity), Insulin (pancreas --> glucose availability)
40
What are the major salivary glands?
* **Parotis** (parotid gland)
* **Mandibularis** (madibular gland)
* **Sublingualis** (sublingual gland)
41
What are the small salivary glands?
* Ventral jaw glands
* Palate, pharyngeal glands
* Lips glands (labiales)
* Zygomatic glands
42
What are the types of secretions?
* Serous
* Mucous
* Seromucous (mixed)
43
Which salivary glands provide the largest amount of secretion?
**Parotis & Mandibularis** account for **90%** of salivary secretion.
44
What are the primary functions of saliva (digestive functions)?
* Protection of the bucal mucosa & teeth
* Facilitation of deglutition
* Initiation of enzymatic carbohydrate digestion (human & pigs --> amylase, destroys cellulose)
* pH regulation (HCO3-, bicarbonate)
45
What are the secondary functions of saliva?
* Immunologic function (Lysozyme, Ig's)
* Thermoregulation (panting in dogs)
* Defense mechanism in some species (llamas, alpacas - spit w/high accuracy)
46
True or False. Cattle produce 60-160 L of saliva per day.
True
47
According to the research article, what breed of dogs is more likely to have problems w/weight & appetite?
Labrador retrievers & related Flat coat retrievers
48
According to the research article, a mutation in what gene causes an association w/greater weight, adiposity, & food motivation?
| What neuroactive peptides are disrupted?
* 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
49
True or False. The POMC mutation is more often found in service dogs than average companion animals.
**True**
* B/C a highly food-motivated dog is more easily trained w/treats using positive reinforcement
50
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?
Hypothalamic leptin melanocortin
51
What makes up saliva?
99% water & 1% electrolytes (Na+, K+, Cl-, HCO3-)
52
In the salivary gland, what is produced in the ducts?
Secondary saliva (K+ and HCO-)
53
In the salivary gland, what is produced in the acinus (glandular epithelium)?
Primary saliva (Cl-, Na+, H2O)
54
What can be caused by disturbances in saliva production?
* Xerostomia (dry mouth)
* Bucal ulcers
* Dysphagia
* Proliferation of bacterial population
* Cavities
55
How is saliva secretion regulated by the parasympathetic system?
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.
56
How is saliva secretion regulated by the sympathetic system?
Sympathetic system (3 first thoracal segments) acts on α-1receptors (by Epi and NEpi) and causes secretion of small volumes of consistent (mucous) saliva
57
How is the innate (reflex) of saliva secretion stimulated?
Through contact w/bucal mucosa (mechanoreceptors)
58
How is the conditioned saliva secretion stimulated?
Through sight, smell, or immagination of food.
* i.e. Close eyes and imagine lemon
59
Explain Ivan Pavlov's experiment w/the conditioned stimulus.
* Bell = Salivation
60
What are the four routes of secretion of the GI tract reach their target tissue?
* Endocrine
* Paracrine
* Autocrine
* Neurocrine
61
________________ 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
**(D) Endocrine** secretions are deposited close to blood vessels, and tehn blood carries the substances to their target tissues.
62
________________ substances diffuse through the interstitial space to affect other cells.
a. Paracrine
b. Autocrine
c. Neurocrine
d. Endocrine
**(A) Paracrine** substances diffuse through the interstitial space to affect other cells.
* NEVER reaches bloodstream
63
________________ substances of a given cell regulate functions of the same cell.
a. Paracrine
b. Autocrine
c. Neurocrine
d. Endocrine
**(B) Autocrine** substances of a given cell regulate functions of the same cell.
64
________________ refers to secretions by enteric neurons that affect muscle cells, glands, and blood cells.
a. Paracrine
b. Autocrine
c. Neurocrine
d. Endocrine
**(C) Neurocrine** refers to secretions by enteric neurons that affect muscle cells, glands, and blood cells.
* NEED a nerve
65
What is the criteria for a hormone to be a hormone (& not just a peptide)?
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
What are the big 5 GI hormones?
* Secretin
* Gastrin
* CCK (Cholecystokinin)
* GIP (Gastric Inhibitory Polypeptide)
* Motilin
67
What are the big 5 GI hormone synthesis sites?
* Antrum
* Duodenum
* Jejunum
* Ileum
68
Where is secretin synthesized?
Duodenum & Jejunum
69
Where is gastrin synthesized?
Antrum & Duodenum
70
Where is CCK (Cholecystokinin) synthesized?
Duodenum, Jejunum, & Ileum
71
Where is GIP (Gastric Inhibitory Polypeptide) synthesized?
Duodenum & Jejunum
72
Where is Motilin synthesized?
Duodenum & Jejunum
73
What is the action and stimuli of secretin?
* **Action:** Stimulates bicarbonate secretion & inhibits acid secretion
* **Stimulus:** Acid, fat, & protein
74
What is the action and stimuli of gastrin?
* **Action:** Stimulates acid secretion
* **Stimulus:** Protein, high pH
75
What is the action and stimuli of Cholecystokinin (CCK)?
* **Action:** Stimulates pancreatic enzyme secretion & gallbladder contraction
* **Stimulus:** Fats & proteins
76
What is the action and stimuli of GIP (Gastric Inhibitory Polypeptide)?
* **Action:** Inhibits gastric secretion & stimulates insulin secretion
* **Stimulus:** Fats & glucose
77
What is the action and stimuli of motilin?
* **Action:** Induction of intestinal motility during fasting (MMC)
* **Stimulus:** Acetylcholine
78
What are the 4 sections of the monogastric stomach?
* Esophageal part
* Cardia
* Fundus & Corpus
* Pylorus
79
Which section of the monogastric stomach is larger in horses?
a. Esophageal part
b. Cardia
c. Fundus & Corpus
d. Pylorus
(A) Esophageal
80
Which section of the monogastric stomach is larger in pigs?
a. Esophageal part
b. Cardia
c. Fundus & Corpus
d. Pylorus
(B) Cardia
81
What are the 3 glandular zones of the stomach and their secretions?
* Cardias --> Mucus
* Fundus --> HCl, Enzymes
* Pylorus --> Mucus
82
Which animal secretes the most gastric acid?
a. dogs
b. humans
c. pigs
d. horses
(D) Horses
83
What are gastric pits?
The glandular mucosa of the stomach has invaginations, the gastric pits lined w/mucus-secreting cells at the luminal surface.
84
________ 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
**(D) Surface mucous cells** produce a thick mucus to protect the stomach from the acid.
85
________ 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
**(C) Parietal cells** are located in the neck of the gastric glands and secrete HCl.
86
________ cells secrete proteolytic enzyme precursors such as pepsinogen.
a. Mucous neck cells
b. Chief cells
c. Parietal cells
d. Surface mucous cells
**(B) Chief cells** secrete proteolytic enzyme precurosrs such as pepsinogen.
87
________ 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) 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
True or False. Each gastric gland leads into a deep gastric pit.
**False**
* Each **gastric pit** leads into a deep **gastric gland**
89
What is the importance of intrinsic factor (IF, a glycoprotein) secreted by parietal cells?
Essential for vitamin B12 absorption in the ileum.
* gastric glands & mucous cells
90
True or False. All functional cell types of the gastric pit originate from mucous neck cells in the neck of the gland.
**True**
* Mucous neck cell = Stem cell
91
What do enteroendocrine cells secrete?
Secrete hormones and paracrine messengers that regulate digestion
* gastrin
92
How do parietal cells secrete HCl (mechanisms involved & structures that help)?
* 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
Why is HCl important in nature?
* 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
How is the structure of a chief cell related to its function and what they secrete? How is it different in calves and lambs?
* 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
What are enteroendocrine cells?
* 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
What are some enteroendocrine cells and their secretions?
* G cells --> Gastrin
* D cells --> Somatostain
* I cells --> CCK
97
Where do enteroendocrine cells secrete their granule content and where do they go from there?
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
What are mucins?
| Mucus-producing cells
**Glycoproteins secreted by exocytosis.**
* Nt & Ct possess serveral Cysteine residues --> Disulfide bridges btwn monomers --> Protection & lubrication of the mucosa
99
How long do surface mucus cells live?
* Regenerate every 3-5 days
* Do not live long
* ↑ mitotic activity in the isthmus of the gastric pit
100
What are the purpose of mucus cells?
Protection and lubrication of the mucosa
101
What are the 3 levels that regulate HCl?
* **Neural** (mediated by acetylcholine)
* **Hormonal** (mediated by gastrin & somatostain)
* **Paracrine** (mediated by histamine)
102
# REWORD???
For each stimulatory substance, what is the mediator for HCl secretion to be regulated?
* Acetylcholine --> Vagus nerve
* Histamine --> Enterochromatin like cells (ECL)
* Gatrin --> Vagus nerve
103
# REWORD???
What is released from D cells that inhibits gastrin production?
Somatostatin --> D cell
* endocrine regulation
* inhibitory substance = somatostain
104
At what pH is HCl production inhibited?
< 3 (less than 3)
105
What kind of feedback mechanism is the HCl secretion of parietal cells?
| neg/pos
Negative feedback mechanism
106
How is gastric acid secretion related to the ATPase pump under resting conditions?
The H+, K+, ATPase has limted access to the apical membrane
107
What occurs in the apical membrane after acid secretion?
| Stimulated Cell
Canaiculi fuse w/the apical (luminal) membrane and vesicles containing H+, K+, ATPase are targeted to the apical membrane increasing HCl secretion.
108
What are the 2 levels that stimulate the secretion of gastric enzynes?
* Neural (Ach, NA)
* Hormonal (Secretin, CCK)
109
What is released from the small intestine when food particles are present?
CCK & Secretin
* amino acids & fatty acids --> CCK
* ↓ pH --> Secretin
110
True or False. Mucus secretion is dramatically altered by the presence of food as gastric acid and enzymatic secretion.
**False**
* Mucus secretion is **NOT** dramatically altered by the presence of food as gastric acid and enzymatic secretion.
111
What substances stimulate mucus secretion?
Ach & Prostaglandine E
* ↓ pH stimulate produce of mucus
112
What is the reason that NSAIDs would cause gastric ulcers?
* 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
True or False. After 3 days on NSAIDs a generally healthy patient is at high risk for a gastric ulcer.
**False**
* It would be with long term use of NSAIDs
114
What does removing COX-1 cause and how can it further worsen gastric ulcers?
* Impairs healing via reduced mucosal blood flow
* Imparied platelet aggregation
* Increased bleeding/injury
115
What does removing COX-2 cause and how can it further worsen gastric ulcers?
* Reduced angiogenesis
* Reduced leukocyte adherence and increased leukocyte activation
* Increased bleeding/injury
116
What is the pH of gastric acid?
1-4
117
What is the function of gastric acid?
Acts as a defense system for killing microorganisms.
118
How does H. Pylori evade being destroyed by the gastric acid?
* 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
What is the pH in the proximal part of the stomach in horses & pigs?
4-6
120
How are gastric ulcers formed in horses & pigs?
* 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
What are the 3 phases of gastric secretion?
* Cephalic
* Gastric
* Intestinal
122
What occurs during the cephalic phase of digestion?
* 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
What occurs during the gastric phase of digestion?
* 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
What occurs during the intestinal phase of digestion?
* 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
True or False. The small intestine mucosa has a small surface area.
**False**
* The **small intestine mucosa** has a **large surface area.**
126
What are the 3 levels of surface convolutions of the small intestine to expand surface area?
* Plicae circulares (in some species)
* Villi (finger-like epithelial projections)
* Microvilli
127
What is the name of the gland like structure at the base of the villi of the small intestine?
Crypts of Lieberkühn
128
What type of cells are found at the crypts of Lieberkühn?
* Paneth cells
* Endocrine cells
* Stem cells
* Goblet cells
129
What is the secretion of enterocytes/absortptive cells?
* Absorptions of nutrients
* Secretion of digestive enzymes as well as water, Cl-, & HCO3-
130
What are the secretions of goblet cells?
Secretion of mucus
131
What are the secretions of enteroendocrine cells?
* 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
What are the secretion of paneth cells?
Secrete antimicrobial enzymes & peptides that are located in vesicles
133
What are brunner's glands (function & secretion product)?
* 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
What structures or parts of the small intestine have an immune role?
* Mucus layer is the forst barrier of protection
* DCs live in the villi
* Peyer's patches in the ileum have phagocytic cells
135
True or False. Division and replication of enterocytes occurs in the crypts only.
True
* Intestinal crypt cells are among the most rapidly regenerating cells of the body.
* As crypt cells multiply, they migrate upward the villi
136
What is the turnover time of enterocyte regeneration?
4-7 days
137
What determines the length of the villi in the small intestine?
* 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
What do progenitor cells arise from?
The stem cell compartment and differentiate into absorptive enterocytes or secretory goblet, enteroendocrine, or paneth cells.
139
When the progenitor cells are differentiated into the needed cell, what occurs? What is the exception?
* 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
What is the mediator of water secretion in the small intestine?
Osmosis
141
What can cause food to be hyperosmotic and how does the small intestine accomodate for that?
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
As solutes are absorbed in the small intestine, how does water move?
Water follows them osmotically back through the epithelium and into the vascular system reaching the blood stream.
143
In general what direction does water move in the small intestine?
Water will move in whatever direction to keep ingesta isosmotic.
144
What animals have the highest dry weight of the large intestine?
* Horse
* Rabbit
* Guine pig
145
What are the components (& important information) about the large intestine?
* 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
What is a large difference between mucosa within the small intestine and the mucosa of the large intestine?
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
Where do water & nutrients go before entering the vascular system?
Water & nutrients first enter the extracellular fluid before entering the vascular system.
148
What forces are responsible for driving the movement of solutes and water between intravascular & extravascular fluids?
Osmotic and hydrostatic forces (starling forces)
149
How do absorbed nutrients enter the capillaries?
Absorbed nutrients enter the capillaries by **diffusion from the interstitium** (this drives water to the capillaries too)
150
Where does venous blood from the GI tract collect?
* 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
True or False. Lymphatic drainage from the gut passes through the liver & then is reentered into circulation.
**False**
* Lymphatic drainage from the gut **bypasses** through the liver entering the bloodstream through the thoracic duct.
