Answer Key to Session 37 Worksheet

Supplemental Instruction
Iowa State University
1. What are the three purposes of intestinal motility?
 Churns chyme
The Digestive System
Session 37
AN S 214
Dr. Selsby
Mixes chyme with intestinal juice, bile, and pancreatic juice
Moves residue towards large intestine
2. Intestinal motility has two primary motive forces. The first, responsible for churning
contents, consists of random ring-like constrictions, is called ______segmentation_____.
The second consists of _____peristaltic____ waves that push chyme towards the large
intestine. These waves begin in the _______duodenum_____ and move progressively
downward, can be inhibited by _____refilling of stomach_____________.
3. What is the frequency of segmentation?
12 times/min
How long does it take to move chyme down the SI?
2 hours
4. What is the gastroileal reflex?
Relaxing of valve and filling of cecum
5. What is the working pH range of salivary amylase?
Stops working at pH below 4.5
What portion of ingested dietary starch is digested in the mouth? Absorbed in the mouth?
50%, 0%
6. Below, trace the digestion of starch through the small intestine. Above the arrows, write
the names of the enzyme(s) responsible for each step of the breakdown.
maltose and
maltase, dextrinase
7. What channel is responsible for transport of glucose and galactose into the cell?
Sodium-glucose transport proteins (SGLT)
What ion is required to facilitate this transport?
Sodium ion Na+
What category of transports does this sort of channel fall into?
8. How does fructose enter the cell? What is the fate of some of the entering fructose
Facilitated diffusion, converted to glucose
9. How do digested carbohydrates exit the cell into portal circulation?
Facilitated diffusion
Supplemental Instruction
1060 Hixson-Lied Student Success Center  294-6624 
10. Fill in the table below with the steps involved in protein digestion:
.... DIGESTED TO .....
Smaller peptides
Polypeptides into
Amino acids
11. What is the active pH range of pepsin?
Peptide bonds
Big bites (peptide bonds)
Big bites (peptide bonds)
Carboxyl end
Amino end
Split dipeptide into two amino acids
12. Large fat globules are ___emulsified_____ by bile salts in the duodenum. Digestion of
fat by the pancreatic enzyme ___lipase______ yields free fatty acids and monoglycerides.
These then associate with bile salts to form ___micelles_____ which “ferry” them to the
intestinal mucosa. Fatty acids and monoglycerides leave micelles and ___diffuse_____
into epithelial cells. There they are recombined with proteins to form
____chylomicrons____. These are extruded from the epithelial cells by
_____excocytosis_____. The chylomicrons enter ____lacteals______ and are carried
away from the intestine by lymph.
13. What two main enzymes are involved with the digestion of nucleic acids?
Pancreatic ribonuclease and deoxyribonuclease
What kind of transport is required to transport them into enterocytes?
Active transport
14. What are the three components of the large intestine?
Cecum, colon, rectum
15. What structural differences exist between the small and large intestine?
Small intestine: Anatomy differences, enzyme production
Large intestine: Fermentation
16. What main movement type characterizes intestinal motility?
Haustral contractions
17. Define the gastro-colic reflex.
Peristaltic waves: 3 to 4 times per day when food is present in stomach
18. ____Distension____ in one area leads to _____motility_____ in another.
19. Name the 3 classes of ruminants discussed and give 2 examples for each:
1. Concentrate Selectors
a. Deer
b. Giraffes
2. Intermediate Feeders
a. Sheep
b. Goats
3. Roughage Grazers
a. Buffalo
b. Cattle
20. What is the primary difference between saliva of cattle and species previously discussed?
Salivary amylase
21. How much saliva do cattle produce in a given day?
150 L
22. T/F: Ruminants have four stomachs
23. Calves are unique in having a(n) _____esophageal groove______ used to shuttle milk
directly past the _____rumen___ and ___reticulum____to the __omasum__ to prevent
24. Name and describe, in order, the four gastric chambers of the ruminant:
Distinguishing Anatomy
Left side of body
Papillae lined
Highly vascular
Microbial fermentation
No secretions
Honeycomb appearance
Narrow, deep compartment
Large opening
Initiates regurgitation
Can collect hardware (hardware disease)
Laminae-manyply lining
No secretions
Absorb water ~60%
Grind food material
Absorption of fatty acids ~10%
True stomach
Smooth surface
HCl production
Pepsinogen production
Rennin production
25. List, in order, the 4 stages of the rumination cycle:
1. Regurgitation
2. Remastication
3. Reinsalivation
4. Redeglutition
26. Following redeglutition, material enters the _____omasum_____.
27. Name 5 functions of rumination:
 Increase intake
 Reduce particle size
 Increase surface area
 Breakdown plant walls
 Stimulate saliva production
28. What is the end product of rumination?
29. What are the three types of fatty acids produced by the rumen microbes?
Acetate, butyrate, and propionate
30. What condition results from failure to eructate?
31. T/F: Ruminants and monogastrics have similar small and large intestines.
32. In hind gut fermenters, the fermentation vat is located in the _______Cecum______.
33. What is the main difference between horses and rabbits when it comes to digestion?
Cecatrops or coprophagy
34. Name and describe the major parts of the hind gut digestive tract:
Distinguishing Anatomy
20-30% of large intestine
4 feet long
1 foot in diameter in the horse
Microbial fermentation
Absorption of nutrients
Same as monogastric
Water and ion absorption
Same as monogastric
Forms characteristic shape of fecal
35. List the 6 factors influenced by feed intake levels:
 Energy
 Homeostasis
 Growth
 Reproduction
36. What are the 4 variables that influence levels of feed intake?
 Climate
 Metabolic state of the animal
 Nutritional value of food
 Stress
37. As the number of stressors increases, what happens to feed intake? What effect does this
have on protein deposition and fat deposition?
Decrease, Decrease
38. What environmental conditions and temperature range promote the highest level of intake?
What % of regular intake can these values reach?
Cool, dry; 120%
39. At this same temperature range, what environmental conditions will cause a steep drop in
feed intake?
Hot day, muddy and wet, too cold
40. As average temperature increases, feed intake ___decreases___. A cool night with hot days
will result in a ___lesser__ drop in feed intake, than a hot night with hot days.
41. Name 6 characteristics of feed that have an impact on intake.
 Energy density
 Fiber
 Palatability
 Avoidance compounds
 Gut fill
 Viscosity of food structure
42. In ruminant animals, reticulo-rominal signaling of fill to the hypothalamus is mediated by
___tension receptors___ located in the cranial sac of the rumen. Fill in these compartments are
determined by the rate of __digestion___ and the rate of __passage___.
43. What three specific feed characteristics influence reticulo-ruminal fill?
Kind of starch or fiber, lignifications of plant material, modification of feed
44. What are three commonly used feed processing methods and what are their significance?
 Grinding: reduces particle size
 Chemical: increase rate of digestion
 Grinding and Pelleting: omasumal filtration
45. Given the choice, animals will choose feeds with ____higher____ energy densities.
However, many animals will over eat energy, if it is required to satisfy their net ____protein____
46. What are the 4 effects of fiber on food intake and appetite?
Slow absorption, improve metabolism, control appetite, feeling of fullness
47. Palatability influences the degree of feed ____intake____. Appealing smell, taste and
textures will increase palatability, while compounds such as ____tannins___, ____alkaloids____,
and ____toxins_____ will cause feed avoidance. Palatability can be increased by the addition of
48. What effect does gastric peristalsis have on hunger control?
Stimulate hunger and contractions mean stomach is empty
49. What are the 3 modes of communication influencing appetite control?
 Brain center
 Hormones
 Sensory and motor pathways
50. For each of the tissue types below, indicate what appetite-controlling chemicals are
Pancreas: insulin
Adipose tissue: leptin
Brain (3): NPY, AgRP, POMC/CART
Stomach and intestines (4): Ghrelin, GLP-1, PYY, CCK
51. Satiety signals are generated both before and during meals in order to relay to the brain the
__mechanical__ and ___chemical______ characteristics of the feed. These are conveyed by
sensory neurons in the _____vagus____ and __sympathetic_____ nerves into the brain stem.
52. Name the 2 hypothalamic centers involved in appetite control:
Lateral hypothalamus: hunger center
Ventromedial hypothalamus: satiety
53. Animals with lesions in the _____satiety___ center of the hypothalamus have uncontrollable
intake and become obese because they are unable to feel ____full____. Animals with lesions in
the ____lateral____ center of the hypothalamus stop eating and waste away because they are
unable to feel ___hunger____.
54. Orexigenic hormones/neuropeptides ___increase___ appetite and ____decrease___ energy
expenditure. Anorexigenic hormones/neuropeptides ____decrease_____ appetite and
____increase____ energy expenditure.
55. Examples of orexigenic hormones: Ghrelin, NPY, AgRP
Examples of anorexigenic hormones: Leptin, Insulin, CCK, PYY, POMC/CART
56. What are the 4 hormones involved in neuropeptide secretion?
Leptin, Ghrelin, Insulin, PYY