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Anatomy 2 > Chapter 16 Digestive System > Flashcards

Chapter 16 Digestive System Flashcards

1
Q

Abdominal cavity tract layers

A

*Serous membrane: outer layer, connective tissue
*Muscaris- Smooth muscle tissue
* Submucosa
* Mucosa

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2
Q

Absorption of All Nutrients

A

 Macronutrients - digestion is required
 Micronutrients – nutrient molecules so small that no digestion is required before being absorbed
*Vitamins
* Minerals
* Water

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3
Q

Animals Groups Based on Stomach Anatomy

A

 Monogastric
*Simple, single stomach
* Dogs
* Cats
* Horses

 Ruminant
* Complex stomach consisting of 4 chambers
* Cattle
* Goats
*Sheep
* Deer
*Antelope
* Moose

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4
Q

Basic Function of the GIT

A

Digestion of macronutrients (there are 3)
Absorption of all nutrients (there are 6)
Elimination of wastes
Steps:
Prehension—Grasping food with the lips or teeth
Mastication—Mechanical grinding and breaking down of food (chewing)
Digestion—Chemical breakdown of food
Absorption—Movement of nutrients and water into the body
Elimination—Removal of waste materials

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5
Q

Basic Structure of the GIT

A

 Tube that runs from oral cavity to the anus
 Structures included
* Oral cavity – food swallowed
*Esophagus - Dorsal to the trachea**
*Stomach – food becomes chyme
*Small intestine
* Large intestine – chyme becomes feces

Side note- food changes chemically twice -Food to chyme, chyme to feces

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6
Q

Classification of Teeth

A

 Brachyodont teeth
* Carnivores, humans, pigs
*Also ruminant incisors
*Small crowns, well-developed roots
* Do not grow continually

 Hypsodont teeth
* Horse’s incisors and cheek teeth, boar’s canine teeth, rodents, lagomorphs
* Large reserve of crown beneath gingiva
* Grow continually

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7
Q

Composition of Saliva

A

 Mainly water
 Protein
 Electrolytes
 Antibodies
 Glycoproteins
 Salivary bicarbonate
 Enzymes
* Lysozyme
* Amylase - beginning of carb digestion

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8
Q

Deciduous Teeth

A

= Milk Teeth = Baby Teeth

 All domestic species have 2 sets of teeth
* Deciduous and permanent (adult teeth)
 Deciduous teeth
*Smaller and whiter
*Present in the jaw at birth
*Erupt through gums at different times, depending on species

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9
Q

Dental Formula

A

 Represents typical number of each type of tooth found on one side of the upper and lower jaws

Puppy: I3/3, C1/1, P3/3 = 28
Dog: I3/3, C1/1, P4/4, M2/3 = 42
Feline kitten I3/3, C1/1, P3/2 = 26
Feline: I3/3, C1/1, P3/2, M1/1= 30
Equine Adult: 13/3, c1/1. P3-4/3, M3/3= 40 or 42
Porcine I3/3, C1/1, P4/4, M3/3 = 44
Bovine: I0/3, C0/1, p3/3, M3/3 = 32

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10
Q

Digestion

A

Think Macronutrients
 The part of the process where large molecules are broken down into their smaller components
 When small enough, molecules enter the body
 Breakdown processes
* Mechanical digestion
– GI tract movements
* Chemical digestion
– Chemical reactions cronutrients - Carbohydrates, Lipids (Fats), Proteins

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11
Q

Digestion of Macronutrients

A

 Definition – large nutrient molecules that require breakdown into smaller molecules before being absorbed
*“Energy” nutrients (Calories)
** Carbohydrates
** Lipids (Fats)
**Proteins

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12
Q

Elimination of Wastes

A

Food –
 Chyme –
 Feces – waste product from animal’s digestive tract expelled through the anus during defecation
* Water (75%)
*Bacteria
* Fiber
* Undigested/unabsorbed nutrients
* Waste products

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13
Q

Functions of the Liver –

A

Manufacturing Plant, Warehouse, Detox Facility
 Secretes substances essential for digestion and absorption of nutrients
 Synthesizes nutrients and regulates their release into the bloodstream
 Stores glycogen
* Where else in the animal body is glycogen stored?
 Excretes toxic substances
* Those originating within and from outside the body
 Produces plasma proteins, cholesterol, and blood coagulation factors
 Largest digestion gland in the body

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14
Q

Gastric Pits

A

Found on rugae
Different glandular cells, each with different secretions:
Mucus neck cells
Chief cells
Parietal cells

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15
Q

GIT

A

*Gastrointestinal tract, digestive tract, alimentary canal - all names for the same thing
-digestive tract, not accurate though because not all 6 nutrients require digestion
*tube that runs from mouth to anus; has accessory digestive organs

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16
Q

Glandular Portions of the Pancreas

A

 Endocrine portion = pancreatic islets- Regulates sugar
* Contain several different cell types
* Beta cells secrete insulin
* Alpha cells produce glucagon
 Exocrine portion = groups of acini - Aids in digestion
* Ducts merge to converge into pancreatic duct
* Excretions contain bicarbonate and digestive proenzymes
* Anticipation of food causes increase of secretions
* Neural and endocrine stimuli increase secretions

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17
Q

Glycogen Processing in the Liver

A

 Excess glucose can be stored as glycogen
* In liver
* In skeletal muscle and adipose cells
 Glycogenolysis
* Glycogen can be broken down to glucose when needed
 Gluconeogenesis
* Synthesis of glucose from non-carbohydrate sources – amino acids, fatty acids
* Ketosis – Atkins diet, Keto diet BAD!

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18
Q

Heterodont Dentition

A

4 types of teeth of different shapes and sizes each has a different function
 Incisor
 Canine
 Premolar
 Molar

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19
Q

Hypsodont Teeth

A

 Radicular hypsodont
*Apices of roots remain open for a long time
*Apices eventually close and stop growing
* Found in cheek teeth of horses
 Aradicular hypsodont
* Lack a true root
* Grow continuously throughout life of animal
* Found in lagomorphs and some rodents

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20
Q

Lacteals and Blood Capillaries

A

 Lacteals = lymphatic capillaries
* Carry absorbed lipids and fat-soluble substances to thoracic duct, and into vena cava
 Blood capillaries
* collect some absorbed nutrients and transport them to the liver

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21
Q

Liver Overview

A

 Mammalian liver consists of five lobes
 Strategically placed to process blood leaving GI tract
* Prevents toxic substances from entering general circulation
* Area known as the triad
 Hepatic artery and hepatic portal vein come together and empty their blood into sinusoids
* Kupffer cells engulf foreign objects
 Proteins made by hepatocytes enter bloodstream through pores in adjacent sinusoids
 Bile is excreted by hepatocytes into canaliculi

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22
Q

Lumen

A

Tube of a tract

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23
Q

More Functions of the Liver

A

 Protein production
* Nearly all the plasma proteins, including albumin and blood clotting proteins
 Conversion of amino acids into ketoacids
* Energy production
* Lipid synthesis

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24
Q

Nutrient Processing by the Liver

A

Vital role in keeping blood glucose levels normal
 #1 Glucose absorbed from small intestine
* Enters hepatic portal vein
* Arrives in liver
* Metabolized to produce energy
 #2 Fructose and galactose (milk sugar breakdown) can be converted to
glucose by the liver

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25
Q

omentum

A

A double layer Connects the peritoneum that links the stomach to abdominal wall or to other organs:
Lesser omentum
Greater omentum

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26
Q

Oral cavity anatomy

A

 Lips
 Tongue
 Teeth
 Salivary glands
 Hard palate
 Soft palate

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27
Q

Organs That Contribute Secretions to the GIT

A

SALIVARY GLANDS
PANCREAS
LIVER

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28
Q

Peristalsis

A

Pattern of muscle contraction that propels food through the GI tract
As soon as an animal swallows it begins a wave of peristalsis

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29
Q

Rugae

A

Transient folds in gastric mucosa
Allow stomach to expand when filled with food
Increase surface area for absorption
“have ridges”

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30
Q

Ruminant Stomach

A

4 chambers
First 3 chambers are the forestomachs: reticulum, rumen, and omasum
▪ The forestomachs are lined by stratified squamous epithelium and are non-glandular.
Last chamber and “true stomach”: abomasum

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31
Q

Saliva

A

 Deposited into oral cavity via ducts
 Production varies depending on species
 Composition: watery or viscous or mixed

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32
Q

Saliva Physiology

A

 Secreted by 3 main paired glands
* Parotid, mandibular, and sublingual
 Lubrication
 Antibacterial action
 pH regulation
 Thermoregulation
 Enzymatic digestion

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33
Q

Small Intestine adaptions

A

 Adaptations help increase surface area
* Organ is long with many loops and coils
*Plications (folds) in mucosal lining
*Villi in mucosa contain microvilli
*Brush border
*Intestinal crypts (crypts of Langerhans)

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34
Q

Stomach anatomy

A

On the left side
 Mucosal lining (rugae)
 Mechanical digestion
 Chemical digestion of protein
* HCl
* Protease (pepsin)
 Pylorus (pyloric valve) - 1 wave valve

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35
Q

Structure of
the Tooth

A

 Crown covered by enamel
*Enamel
* Dentin
–Dentin forms bulk of tooth
— Pulp cavity that contains blood and nerves
 Gingiva - gums
 Root - cemented in gingiva
* Dentin
* Pulp
* Cementum- thin bone that cements
* Periodontal ligament

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36
Q

Surfaces of a Tooth

A

Named by direction the outer surface faces:
 Buccal
 Labial
 Lingual
 Palatal

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37
Q

Teeth

A

The Teeth Embedded in upper maxilla bone and lower mandible bone Parts of a tooth:
Parts of tooth- Crown, Root, Apex, Neck

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38
Q

The Cecum

A

 Blind diverticulum at beginning of colon
*Inconspicuous in carnivores – whipworms in dogs
* Large blind tube in ruminants
* Huge in equines
 3 parts
*Base, main body, apex
 Ileum opens into cecum, colon, or both (depending on species)

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39
Q

The Esophagus (GI physiology)

A

 Muscular tube connecting pharynx to stomach
 Lined with folded mucosa
 Tunica muscularis
* 2 layers (circular and longitudinal) needed to move food

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40
Q

The Exocrine Pancreas

A

 Enzymes are vital to digestion
* lipase, amylase, nuclease, protease
 Proenzyme (or zymogen)
* All proteolytic enzymes secreted in inactive form
* Trypsinogen, chymotrypsinogen, proelastase, procarboxypeptidase A and B
* CCK starts the activation process

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41
Q

The Gallbladder

A

 Concentrates and stores bile until needed
* Bile enters duodenum to emulsify fat - makes fat water soluble
 Provides means for liver to excrete waste products even when animal is not eating
 Composition of bile
* Bile salts
* Phospholipids
* Cholesterol
* Bile pigments

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42
Q

The Large Intestine

A

 Components
* Cecum – blind sac at ileocecal junction
* Colon
* Rectum
* Anus
 Species variation in structure
 Primary functions
* Recover fluid and electrolytes
* Store feces until they can be eliminated

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43
Q

The Monogastric Stomach

A

 C-shaped, located just behind diaphragm
 Glandular portion with gastric pits:
* Cardia
* Fundus
*Body
 Distal portion
*Pylorus

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44
Q

The Oral Cavity

A

= Mouth = Buccal Cavity

 Entrance to the GI tract
 Contains everything in the mouth
 2 parts
*Vestibule
*Space between lips and cheeks, and outer surface of teeth
* Oral cavity
*Bordered by inner surface of teeth, and hard and soft palates

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45
Q

The Pharynx (GI physiology)

A

= Throat/common passageway
 Part of both GI and respiratory tracts
 Swallowing sends food from the oral cavity to the esophagus
 Structures found here
*Eustachian tube
* Tonsils

46
Q

Structure of Small Intestine

A

Tube that carries chyme away from stomach and deposits it in the large intestine
 Suspended from the body wall by mesentery
 Duodenum
* Receives chyme through pyloric sphincter
* Pancreatic duct opens here
* Common bile duct opens here
 Jejunum
* Longest part
* Most chemical digestion and absorption occur here
 Ileum
* Prominent Peyer’s patches
* Empties into large intestine at cecum (horse), at colon (dog and cat), or at cecum and colon (ruminant and pig)

47
Q

The Stomach physiology

A

 Functions
*Storage of ingested food
* Mechanical and chemical breakdown of food
*Beginning of protein digestion
*Production of intrinsic factor for Vitamin B12 absorption in small intestine
 Food leaves stomach in semi-liquid form = chyme

48
Q

The Stomach

A

 Functions
*Storage of ingested food
* Mechanical and chemical breakdown of food
*Beginning of protein digestion
*Production of intrinsic factor for Vitamin B12 absorption in small intestine
 Food leaves stomach in semi-liquid form = chyme

49
Q

The Tongue

A

 Muscular structure on ventral surface in oral cavity
 3 parts
*Apex, body, and root
 Papillae on dorsal surface
* Mechanical functions
* Grooming and moving food into pharynx
*Specialized functions
* Taste sensations, pain, temperature, touch, and thermoregulation through panting (dogs)
 4 types of taste buds
– sweet, sour, salty, bitter

50
Q

Functions of Pancreas

A

 Only gland in body with both exocrine and endocrine functions!!!
 Production of pancreatic amylase, proteases, and lipase (groups of acini) - Exocrine
 Secretes bicarbonate into the duodenum
* Helps neutralize acidity of contents and maintains the pH in the duodenum needed for proper enzyme function
 Produces insulin and glucagon
* Help regulate blood glucose levels

Adding secretions that enhance digestion

51
Q

Trace a bolus of food

A

1 - Mouth
2- teeth
3 - tongue
4 - pharynx
5 -esophagus
6 -stomach
7 -duodenum (part of small intestine)
8 - jejunum (part of small intestine)
9- ilium (part of small intestine)
(Food doesn’t go in Cecum, but it’s next. Part of large intestine)
10 - Ascending Colon- 2nd part of large intestine
11 Transverse colon - large intestine
12 - Descending colon - large intestine
13- Rectum - large intestine
salivary glands, pancreas, liver contribute to “tube” but aren’t part of GI tube
14 Anus

52
Q

What Animals Eat

A

 Herbivores eat plant material
* Ruminants: cattle and goats
* Non-ruminants: horses
 Carnivores eat meat
* Cats
 Omnivores eat combination of plants and meat
* Humans, pigs, dogs

53
Q

Small intestine adaptions

A

 Adaptations help increase surface area
* Organ is long with many loops and coils
*Plications (folds) in mucosal lining
*Villi in mucosa contain microvilli
*Brush border
*Intestinal crypts (crypts of Langerhans)

54
Q

Salivary Glands

A

Adding secretions that enhance digestion
Parotid- ventral to ear, very large
Mandibular- medial to mandible
Sublingual- below tongue
Zygomatic- cheek bone

55
Q

acini

A

Pancreatic acinar cells synthesize and secrete almost all the digestive enzymes active in the lumen of the small intestine which are necessary for nutrient digestion

56
Q

Lobes of the liver

A

left medial
left lateral
quadrate lobe
right medial
right lateral

57
Q

Ruminants

A

 Herbivores
* Cattle, sheep, goats, deer, reindeer, moose
* Require more food and more complex digestion process than carnivores
 Forestomachs are non-glandular
* Microorganisms for fermentation in rumen and reticulum
* Complex carbohydrates (cellulose) broken down
 Abomasum functions same as monogastric stomach

58
Q

Rumen

A

Part of the Forestomachs
 Each performs a different digestive function and has different anatomical features
 Rumen = “the paunch”
 Occupies most of left side of abdominal cavity
 Microorganisms ferment carbohydrates, so they can digest fiber
 Papillae in mucosa increase surface area for absorption
 Pillars divide rumen
* Dorsal sac, ventral sac, and 2 caudal sacs

59
Q

Reticulum

A

Part of the Forestomachs
 Reticulum = “the
honeycomb”
 Located cranial to the rumen
 Contents easily enter and exit to rumen
*reticulorumen

60
Q

Esophageal Groove

A

Part of the Forestomachs
 Links esophagus with omasum in young ruminant
 Milk for nursing ruminant bypasses reticulorumen
* Goes directly to omasum and abomasum
 If groove didn’t close:
*Bacteria in reticulorumen would ferment milk
* Lactic acid produced would inhibit normal microbial action

61
Q

Omasum

A

Part of the Forestomachs
 Omasum = “many plies” or “book stomach”
 Connects reticulorumen to abomasum
 Folds of mucosa with papillae on surfaces
 Absorption of water and salts here

62
Q

The Abomasum

A

 Elongated “true stomach”
 Lined with glandular tissue
 Released renin causes milk protein coagulation
*Prolongs time for pepsin to break down proteins
 Functions like simple monogastric stomach
*Exception: abomasum is not a storage compartment
 Continuous flow of ingesta into abomasum

63
Q

Contractions in the Reticulorumen

A

Primary contractions = mixing contractions
 Ensure content movements between reticulum and rumen
 Separate particles based on size

64
Q

Rumination

A

Rumination = “chewing the cud”
 Ingesta moves from reticulorumen back into oral cavity for additional saliva and continued chewing
 4-step process
* Regurgitation
* Re-insalivation
* Remastication
* Re-swallowing

65
Q

secondary contractions

A

 Eructation = belching = secondary contractions
 Responsible for the release of gases
* Carbon dioxide and methane produced during
fermentation
 Without gas release, develop condition of bloat
 Area of brainstem controls reticuloruminal activity

66
Q

Reticulorumen Ecosystem

A

 Wide variety of bacteria, protozoa, and fungi in ruminants
 Proper balance between types acquired after birth
* Controlled by diet and amount of food consumed
*Also by interactions between mother and young
 Oxygen ingested along with food

67
Q

Carbohydrate Digestion in Ruminants

A

 Ruminants’ diet – herbivore
* Mostly grasses (roughage): complex carbohydrates
* Cellulose, hemicellulose, and pectin
*Some grains (concentrates): nonstructural carbohydrates
* Starches, fructosans, and simple sugars
 Microorganisms use nutrients consumed for their own growth and development
 Ruminant can digest microorganisms as source of protein
 Complex carbohydrates
* Hydrolysis by catalase enzymes to simple sugars
 Starches and soluble sugars
* Hydrolysis by amylolytic bacteria to monosaccharides and polysaccharides
*Saccharides absorbed by microvilli and further metabolized to pyruvate and converted to volatile fatty acids (VFAs)
* VFAs are main source of energy for the ruminant

68
Q

Lipid Digestion in Ruminants

A

 Lipids found in grasses and plants:
* Triglycerides, glycolipids, free fatty acids
 Lipids constitute small portion of diet
* Too many lipids: decreased appetite, reduced motility of reticulorumen, decreased fermentation of cellulose
 Microorganisms in reticulorumen hydrolyze triglycerides
*VFAs produced, used to produce energy or stored
*Acetic acid (acetate), propionic acid (propionate), and butyric acid (butyrate)

69
Q

Protein Digestion in Ruminants

A

 Fermentation process occurs before enzymatic digestion
 Nutrients in food first available to microbes in reticulorumen
* Microbial peptidase breaks down proteins to peptide chains
* Microbes can synthesize amino acids from ammonium, and by converting non-protein nitrogen
(NPN) compounds
 Further broken down in small intestine by enzymatic action and transported to liver
* Amino acids are metabolized
* Urea is produced; goes back to rumen (and then saliva) for reuse in making microbial proteins

70
Q

Glucose Production in Ruminants

A

 Ruminal microbes process carbohydrates before they are exposed to intestinal enzymes
* potential glucose deficiency
 Gluconeogenesis
* Occurs in liver from non-carbohydrate sources
*Propionate, butyric acid, acetate, absorbed amino acids
 Conservation of glucose

71
Q

Large Intestine Comparative Anatomy

A

 Carnivores: simple, tubular colon; poorly developed cecum
 Nonruminant herbivores: very large colon and cecum (hindgut)
* Fermentation site

72
Q

VFA

A

Volatile fatty acids are the main energy source for ruminants, providing approximately 70% of the total energy requirements. They are used primarily by the microorganisms for reproduction and growth, with the excess production being used by the ruminant itself.

73
Q

Ascending Colon in various species

A

Equine- Large Colon
Bovine- Coiled Colon
Porcnie - Spiral Colon

74
Q

Elimination of Wastes

A

 Food –
 Chyme –
 Feces – waste product from animal’s digestive tract expelled through the anus during defecation
* Water (75%)
*Bacteria
* Fiber
* Undigested/unabsorbed nutrients
* Waste products

75
Q

Digestion in the Oral Cavity and Pharynx

A

 Prehension
 Chewing = mastication
 Salivary secretion
* Regulated by nervous system
*Also triggered by conditioned responses
 Swallowing = deglutition
*Voluntary
*Pharyngeal stage
*Esophageal stage – initiates peristalsis

76
Q

Pepsin

A

 A proteolytic enzyme
 Essential in the digestive process
*Begins the chemical digestions of proteins
 Activated in the fundus
*Pepsinogen secreted by chief cells
*Pepsinogen converted to pepsin in presence of HCl

77
Q

Pyloric Gland Region of Stomach

A

 Last glandular portion of the stomach
 Regions:
* Pyloric antrum
* Pyloric canal
* Pylorus
 Opens into duodenum through pyloric sphincter
 Cells found here
* Mucous-secreting cells
* G cells secreting gastrin

78
Q

Stimulation of Stomach Secretions

A

 3 substances stimulate secretions by glandular cells
*Acetylcholine from cholinergic neurons
* Gastrin released by G cells
* Histamine secreted by enterochromaffin-like cells
(ECL-cells) in gastric mucosa
 Cephalic phase of secretion – thinking about food!
*Anticipation of eating a meal
 Gastric phase of secretion
*Begins when food enters stomach

79
Q

Cephalic Phase of Secretion

A

 Begins in anticipation of eating
*Enteric nervous system is stimulated
*Acetylcholine is released and binds to receptors
* Parietal cells secrete H+ and Clions
* Chief cells secrete pepsinogen into stomach
* G cells secrete gastrin into bloodstream

80
Q

Gastric Phase of Secretion

A

 Begins when food enters stomach
* Glandular cells stimulated by stretching of stomach wall
*Peptides formed by protein breakdown
* Local enteric reflexes, and vagal reflexes to and
from brain
*Stomach can be as acidic as pH 2.0

81
Q

Digestion of protein, carbs and fats start where

A

Carbs- mouth
Protein - stomach
Fats- small intestine

82
Q

Monogastric Stomach Motility

A

 Muscle contractions of stomach wall help break down food particles
 Gastric contents released at controlled rate
*Specialized smooth muscle pacemaker cells
* Fluctuations in resting membrane potential lead to muscle contraction
*Acetylcholine elevates resting potential
*Entry of Ca++ ions into muscle cell initiates contraction
 Each part differs in degree of movement based on its function
 Fundus expands to accommodate large volumes of food
 Body is a large mixing chamber
 Pyloric antrum acts like a pump

83
Q

Peristaltic Contractions

A

 Movements
* Fragment food into small particles
*Influence rate of gastric emptying
 Weak in fundus and body
 Progressively stronger as food moves toward pylorus
* Larger particles prevented from leaving stomach
* Retropulsion

84
Q

Segmentation

A

Grinding of food.

85
Q

Nutrient Components in a Meal

A

Macronutrients-
 Carbohydrates
 Proteins
 Lipids
Micronutrients-
 Vitamins
 Minerals
 Water

86
Q

Digestion Completed in the Small Intestine

A

 Mechanical digestion
*Essential to increasing amount of food surface area
 Chemical digestion
* Digestive enzymes from exocrine pancreas responsible
* Carbohydrates – amylase
*Proteins – proteases
* Lipids (fats) – lipase

87
Q

Absorption of All Nutrients

A

 Macronutrients- requires digestion
 Micronutrients – nutrient molecules so small that no digestion is required before being absorbed
*Vitamins
* Minerals
* Water

88
Q

Carbohydrates

A

 Starches
* Made of repeating glucose monosaccharides
 Sugars
*Simple monosaccharides (glucose)
* Multiple monosaccharides linked together
* Disaccharides, sucrose and lactose
 Cellulose
* Complex carbohydrate

89
Q

Proteins

A

 Proteins
 Made of repeating amino acid units
 Chain of >50 amino acids = protein
 Chain of <50 amino acids = peptide

90
Q

Lipids

A

 Majority of fat found in animal’s diet
 Made of a glycerol backbone and 3 fatty acids

90
Q

Lipids

A

 Majority of fat found in animal’s diet
 Made of a glycerol backbone and 3 fatty acids

91
Q

Chemical Digestion

A

Carbohydrate digestion
 Begins with amylase in saliva
 Continues in stomach and small intestine
 Protein digestion
 Begins in the stomach; continues in small intestine
 Pepsinogen activated by HCl to pepsin

92
Q

Mucosa

A

*Innermost layer of GIT
*made of epithelium, lamina propria and muscularis mucosae
-epithelium is made of stratified squamous and simple columnar epithelium
-mucosa is made of loose areolar connective tissue
-muscular mucosae is a thin layer of smooth muscle

93
Q

Prostaglandins

A

*Hormonelike substances that regulate biochemical activities in the tissue they are formed.
*Produced from lipids (eicosanoids)
*Important role in controlling blood pressure and smooth muscle contraction

94
Q

Serous Layer of GIT

A

–Visceral peritoneum
–Parietal peritoneum
–Mesentery
–Omentum

95
Q

Non-fermentative Digestion

A

▪ Monogastric animals, including the dog, cat, and horse
▪ Muscle contractions of the stomach wall contribute to
the mechanical breakdown of food particles
▪ Mechanical digestion in the oral cavity and in the stomach is essential to increase the amount of food surface area that can be exposed to the digestive enzymes
▪ Digestive enzymes are responsible for the second phase of digestion, chemical digestion
▪ Luminal chemical digestion breaks down macromolecules being broken down through hydrolysis
▪ Hydrolysis is then repeated in membranous chemical digestion, where the short chain polymers are completely broken down into their most basic component parts
▪ In some animals, such as omnivores, chemical digestion begins with amylase (breaks down starch CHOs) in the saliva.
▪ In animals that do not have amylase in their saliva, the digestion of starch does not begin until the food has reached the small intestine and pancreatic amylase is released.
▪ Protein digestion, on the other hand, begins in the stomach.

96
Q

Chemical Digestion Monogastric

A

▪ Chemical digestion is divided into two phases:
➢ Luminal chemical digestion
▪ Occurs in the lumen of the stomach or intestine
▪ Digestive enzymes mix with food and acid or alkaline fluids
to digest free-floating food particles in the lumen
➢ Membranous chemical digestion

97
Q

Fermentative Digestion

A

▪ Mastication breaks larger food mixing them with saliva to create a rounded mass called a bolus that the ruminant swallows.
▪ Saliva is alkaline and contains both bicarbonate and phosphate which help buffer the rumen during fermentation
▪ As food leaves the forestomachs, it enters the fourth chamber or the “true” stomach, the abomasum
▪ The rumen and the reticulum are where the majority of cellulose is degraded.
*contain a large number of microorganisms (bacteria,
protozoa, and fungi) that are responsible for a fermentation
* During fermentation, complex CHOs such as cellulose and hemicellulose are broken down
▪ The omasum is where the absorption of water and salts take place.
▪ The abomasum (” true stomach”) functions in the same way as the monogastric simple stomach. However, The flow of ingesta into the abomasum is continuous.
▪ CHO digestion – starch end product is volatile fatty acids (main source of energy for the ruminant)
▪ Lipid digestion – triglycerides are hydrolyzed producing VFAs
▪ Protein digestion – the end product are amino acids used to make microbial protein, ammonium to proAnuduce VFAs.

98
Q

CHO

A

Carboydrates

99
Q

Anus

A

The opening of the GI tract for elimination of stool
➢ At the junction of the rectum and anus, the mucosa changes from glandular villi to flattened squamous epithelial tissue
➢ Two large muscle sphincters surround the anus to help retain the stool before defecation
➢ The inner anal sphincter is under smooth muscle control while the outer anal sphincter is under skeletal muscle control.

100
Q

Rectum

A

➢ When chyme passes through the large intestine much of
the water is absorbed, leaving a semisolid material called feces.
➢ When feces are transported to the rectum, sensory receptors are stimulated. This stimulates the defecation reflex ➢ The animal then perceives the need to defecate

101
Q

Colon

A
  • some microbial digestion
    —Ascending
    —Transverse
    — Descending
  • most variety between species
    *reabsorbs fluids and prepare wastes for elimnation
102
Q

Carbohydrate digestion

A

▪ Majority of chemical CHO digestion occurs in small intestine
▪ Starches are one of the few CHOs broken down in the luminal phase
▪ In the membranous phase enzymes in the brush border:
–there are specific enzymes for each type of polysaccharide
– Sugars, such as sucrose and lactose, are degraded

103
Q

Protein digestion

A

*Luminal protein digestion began in the stomach with pepsin and is completed in the small intestine.
*The pancreas releases proenzymes that are activated in the lumen of the small intestine.
— the endopeptidases and the exopeptidases
➢ Free amino acids are yielded
➢ Some peptide chains are incompletely hydrolyzed and form
dipeptides and tripeptides.
—-These are small enough to be absorbed into the intestinal wall

104
Q

Luminal Digestion

A

*First phase of chemical digestion
*Large macromolecules broken into short polymers through hydrolysis

105
Q

Membranous Digestion

A

*Second phase of chemical digestion
*Hydrolysis is repeated to completely break down the short chains of polymers formed through luminal digestion

106
Q
A

▪ Fats and fat-soluble vitamins are also digested in and absorbed from the small intestine.
▪ Triglycerides are the primary dietary lipids; other lipids include cholesterols, phospholipids, and esters
▪ Lipids are not water soluble and cannot be dissolved in the watery medium of the GI fluids.
▪ In order to digest and absorb fats, a four-step process must occur:
➢ Emulsification
➢ Hydrolysis
➢ Micelle formation
➢ Absorption

107
Q

Emulsification

A

Begins in the stomach where lipids are warmed to body
temperature and thoroughly mixed. This process helps
break lipids into smaller droplets. Emulsification is then
completed in the small intestine by the detergent action of
bile salts and phospholipids.

108
Q

Hydrolysis of Lipids

A

▪ Bile salts coat the lipid droplets, causing them to repel one
another and remain small individual droplets. Decreasing
the size of lipid droplets increases the surface area
available for the hydrolytic pancreatic enzymes, lipase and
colipase, to break down each triglycerid

109
Q

Micelle formation

A

▪ The monoglyceride and the two fatty acids are not yet
soluble in water, which again would cause a problem if it
were not for the bile salts forming micelles
▪ The micelles essentially act like tiny ferries, transporting the
fatty acids and monoglycerides to the enterocyte surface. At
this point the monoglyceride and fatty acids diffuse into the
cell and the bile salts do not. This keeps the bile salts
available to transfer other monoglycerides and fatty acids

110
Q

Absorption of Lipids

A

▪ Inside the enterocyte, the monoglyceride and the two fatty
acids are reassembled into a triglyceride and packaged into
chylomicrons.
▪ Chylomicrons are spherical structures that are made up of
triglycerides, cholesterol, phospholipids, and proteins
▪ The Golgi apparatus packages the chylomicrons into
vesicles, which are transported to the cell membrane, from
which they are released into the interstitial fluid by
exocytosis.
▪ Chylomicrons cannot enter the capillaries because of their
large size; instead they are picked up by the lymphatic
system and transported to the

111
Q

Bird stomachs

A

The stomach of birds consists of a glandular portion (proventriculus) and a muscular portion (gizzard). The process of chemical digestion begins in the proventriculus. The gizzard is comprised of bands of striated muscles that grind food.

Anatomy 2 (9 decks)

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