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ASCI 2120 Exam 3 > Digestive System > Flashcards

Digestive System Flashcards

1
Q

What are the functions of the digestive system?

A

Ingestion, mechanical processing, digestion, secretion, absorption, excretion.

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2
Q

What are the parts of the GI tract, and what are the accessory organs?

A

Mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus.
Accessory organs: teeth, tongue, salivary glands, liver, pancreas.

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3
Q

What is the difference between monogastrics and ruminants?

A

Monogastrics have a single true stomach with one chamber. Ruminants have multiple compartments.

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4
Q

What are the four major layers of the GI tract wall, from inside to outside?

A

Mucosa, submucosa, muscularis externa, serosa.

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5
Q

What type of tissue is the mucosa made of? Is it vascular?

A

The digestive epithelium is made of epithelium (obviously) and the lamina propria is areolar tissue, which contains blood and lymph vessels and sensory nerve endings.

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6
Q

What are rugae?

A

Longitudinal folds that disappear as the tract fills

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7
Q

What are plicae?

A

Circular permanent transverse folds

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8
Q

What is the purpose of all the folds in the digestive tract?

A

They increase the surface area available for absorption.

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9
Q

What type of tissue makes up the submucosa? Is it vascular?

A

Dense irregular connective tissue. Contains large blood and lymphatic vessels and exocrine glands, and a network of nerve fibers.

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10
Q

What is the muscularis externa made of? What does it do?

A

It’s made of smooth muscle cells that form an inner circular layer and an outer longitudinal layer. It plays an essential role in mechanical processing and the movement of materials. Its movements are coordinated primarily by neurons of the myenteric plexus.

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11
Q

What is the serosa?

A

A serous membrane

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12
Q

What is peristalsis?

A

Circular muscle contractions that create wavelike movement along the tract and propel digestive tract contents along the tube ahead of them.

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13
Q

What is segmentation?

A

Periodic circular muscle contractions that occur in different adjacent sites and mix digestive tract contents and slow their movement through the tract.

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14
Q

What are the two types of neural mechanisms that control digestive function?

A

Short reflexes and long reflexes.

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15
Q

Tell me about short reflexes.

A

The sensory neurons, interneurons, and motor neurons are all located in the myenteric plexus. They coordinate local peristalsis and trigger the secretion of digestive glands in one region of the digestive tract.

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16
Q

Tell me about long reflexes.

A

They involve interneurons and motor neurons in the CNS, and control large-scale peristaltic waves

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17
Q

Tell me about hormonal mechanisms that control digestive function.

A

There are at least 18 hormones produced by the digestive tract that affect every aspect of digestive function and may affect the activities of the other systems.

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18
Q

Tell me about what local mechanisms do to control digestive function.

A

Local factors, like pH, and physical and chemical stimulations, affect adjacent cells within a small segment of the digestive tract.

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19
Q

What are the functions of the oral (buccal) cavity?

A

Analysis of foods, mechanical processing, lubrication by mixing with mucus and salivary secretions, and initiating the digestion of carbs and lipids by the enzymes of salivary glands.

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20
Q

What are the three pairs of salivary glands and what do they produce?

A

The parotid glands produce amylase, the submandibular glands secrete a mixture of buffers, glycoproteins, and amylase, and the sublingual glands produce lingual lipase.

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21
Q

What are the functions of the monogastric stomach?

A

Bulk storage of ingested food, mechanical breakdown of ingested food, and disruption of chemical bonds in food via acids and enzymes

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22
Q

What is chyme made of?

A

Ingested food + the secretions of the stomach. Highly acidic.

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23
Q

What are the five regions of the monogastric stomach?

A

The cardia, the fundus, the body, the pyloric antrum, and the pylorus.

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24
Q

What do gastric pits contain?

A

Gastric glands, which secrete gastric juices.

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25
Q

What do parietal cells secrete?

A

Hydrochloric acid

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26
Q

What do chief cells secrete?

A

Pepsinogen

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27
Q

What is the active version of pepsinogen?

A

Pepsin

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28
Q

What do G cells secrete?

A

Gastrin, which stimulates the secretion of both parietal and chief cells, and the contraction of the gastric wall

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29
Q

What are the three phases of gastric activity?

A

The cephalic phase, the gastric phase, and the intestinal phase

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30
Q

What triggers the cephalic phase?

A

Sight, smell, taste, or thoughts of food

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31
Q

What is the function of the cephalic phase?

A

To prepare the stomach for the arrival of food

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32
Q

What is the duration of the cephalic phase?

A

Minutes

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33
Q

What mechanisms are involved in the cephalic phase?

A

Neural: via preganglionic fibers in the vagus nerve and synapses in the submucosal plexus

34
Q

What are the actions of the cephalic phase?

A

Primary: increased volume of gastric juice by stimulating mucus, enzyme, and acid production
Secondary: stimulation of gastrin release by G cells

35
Q

What triggers the gastric phase?

A

The arrival of food in the stomach

36
Q

What are the functions of the gastric phase?

A

Enhance the secretion started in the cephalic phase; homogenize and acidify chyme; initiate digestion of proteins by pepsin

37
Q

What is the duration of the gastric phase?

A

3-4 hours

38
Q

What are the mechanisms involved in the gastric phase?

A

Neural: short reflexes triggered by the stimulation of stretch receptors as the stomach fills, and the stimulation of chemoreceptors as the pH increases
Hormonal: stimulation of gastrin release from G cells by parasympathetic activity and presence of peptides and amino acids in chyme
Local: release of histamine by mast cells as the stomach fills

39
Q

What are the actions of the gastric phase?

A

Increased acid and pepsinogen production; increased motility and initiation of mixing waves

40
Q

What triggers the intestinal phase?

A

When chyme starts to enter the small intestine

41
Q

What is the function of the intestinal phase?

A

Controls the rate of chyme entry into the duodenum

42
Q

What is the duration of the intestinal phase?

A

Hours

43
Q

What are the mechanisms involved in the intestinal phase?

A

Neural: short reflexes triggered by the distension of the duodenum
Hormonal (Primary): stimulation of CCK, GIP, and secretin release by the presence of acid, carbs, and lipids.
Hormonal (Secondary): release of gastrin stimulated by presence of undigested proteins and peptides

44
Q

What are the actions of the intestinal phase?

A

Feedback inhibition of gastric acid and pepsinogen production; reduction of gastric motility

45
Q

How much nutrient absorption happens in the monogastric stomach?

A

Very little

46
Q

What are the four compartments of the ruminant stomach (in order)?

A

Reticulum, rumen, omasum, and abomasum

47
Q

What are the four special actions that ruminants do?

A

Regurgitation, remastication, reinsalivation, and redeglutition

48
Q

What is the purpose of reticuloruminal contractions?

A

Coordinated mixing of rumen contents, regurgitation for rumination, and eructation (expelling the built-up CO2 or methane)

49
Q

What nerve generally controls rumen motility?

A

The vagus nerve

50
Q

What stomach compartment is primarily affected by vagal indigestion?

A

The rumen

51
Q

Which stomach compartment has microbes and an anaerobic environment?

A

Rumen

52
Q

Tell me about carbohydrate digestion in the rumen

A

Bacterial cellulases digest cellulose into monosaccharides; which are then converted to VFAs by acetic, proprionic, and butyric acids.

53
Q

Tell me about protein digestion in the rumen

A

Rumen microbes break down RDP (Rumen Degradable Protein) to amino acids, then ammonia, which are used for microbial protein synthesis and growth.
The microbes also convert non-protein nitrogen to ammonia. Some ammonia is absorbed into the bloodstream and converted into urea in the liver.

54
Q

Tell me about lipid digestion in the rumen.

A

Lipolysis, which is the release of constituent fatty acids; and biohydrogenation, which is the conversion of unsaturated fatty acids to saturated fatty acids.

55
Q

Describe the reticulum

A

The smallest compartment; a honeycomb-like lining; coordinates contractions with the rumen (reticulorumen contraction)

56
Q

Describe the omasum

A

Breaks down food particles further, conveys ingesta into the abomasum, absorbs any VFAs, removes bicarbonate ions, and absorbs water

57
Q

Describe the abomasum

A

Functions much the same as a monogastric stomach

58
Q

What is the reticular groove?

A

Conveys swallowed liquid from the esophageal opening directly to the omasum; essentially bypasses the rumen and reticulum

59
Q

What is rumen lactic acidosis (grain overload)?

A

A decrease in pH in the rumen of cattle; develops when ingesting large amounts of unaccustomed feeds rich in ruminally fermentable carbs (creates large quantities of VFAs); causes ruminitis, lameness, metabolic acidosis, pneumonia, and death

60
Q

Describe bloat

A

Happens when animals are grazing young, lush pasture, particularly if the pasture has high legume content; large volumes of gas cannot escape from the rumen

61
Q

What are the three segments of the small intestine, and which is the main site for digestion and nutrient absorption?

A

Duodenum, jejunum (main site), and ileum

62
Q

What are crypts?

A

Invaginations of mucose around villi

63
Q

What do goblet cells do in the small intestine?

A

Produce mucus; help protect the intestinal mucosa

64
Q

Where are intestinal glands and what do they do?

A

At the bases of villi; lined by enteroendocrine cells; produce intestinal hormones (CCK, secretin, and GIP)

65
Q

What does CCK (cholecystokinin) do?

A

Stimulates production of pancreatic enzymes

66
Q

What does GIP (gastro inhibitory peptide) do?

A

Stimulates release of insulin by pancreatic isles

67
Q

What does secretin do?

A

Inhibits gastric secretion and stimulates production of alkaline buffers

68
Q

Where are submucosal glands and what do they do?

A

In duodenum, produce mucus and buffers; help elevate the pH of chyme from 1-2 to 7-8

69
Q

Where does intestinal juice come from?

A

Arrives by osmosis out of the mucosa, and is secreted by the glands

70
Q

What makes up the endocrine portion of the pancreas?

A

Pancreatic islets

71
Q

What does the exocrine portion of the pancreas do?

A

Secretes water, ions, and digestive enzymes (alpha amylase, lipases, nucleases, proteases, and peptidases) into the duodenum

72
Q

How many hepatic lobes are there in humans? In cattle?

A

4 in humans, 7 in cattle

73
Q

What are hepatic lobules?

A

Basic functional units of the liver; hepatocytes form a series of irregular plates arranged as wheel spokes; sinusoids between the adjacent plates empty into the central vein

74
Q

What are the functions of the liver?

A

Filters materials absorbed from the GI tract; removes toxins and old/damaged RBC’s from the blood; stores nutrients and regulates metabolites levels in blood; produces plasma proteins; secretes biles

75
Q

What are the functions of the gallbladder?

A

Storage of bile; concentration of bile fivefold to tenfold; ejection of the concentrated bile into the duodenum

76
Q

What are the functions of bile?

A

Acids and salts emulsify fats for absorption across the wall of the small intestine; the water and ions assist in the dilution and buffering of acids in chyme

77
Q

Tell me about carbohydrate digestion in the small intestine.

A

Starch is converted into disaccharides by pancreatic amylase; which are then further digested by enzymes in microvilli cell membranes. The resulting monosaccharides are transported across the microvilli cell membrane and absorbed into the blood.

78
Q

Tell me about protein digestion in the small intestine.

A

Gastric pepsin breaks apart some protein chains into smaller polypeptides. Pancreatic proteases partially digest peptides, which are further digested by peptidases in microvilli cell membranes. Amino acids, dipeptides, and some tripeptides are then absorbed across the cell membrane.

79
Q

What are the five pancreatic proteases?

A

Trypsin, chymotrypsin, elastase, aminopeptidase, and carboxypeptidase

80
Q

Tell me about fat digestion in the small intestine.

A

Pancreatic lipases penetrate the bile acid coating around fat droplets and digest fat molecules to produce glycerol, fatty acids, and monoglycerides. The droplets fragment into smaller particles called micelles.

81
Q

What do the sympathetic and parasympathetic nervous systems have to do with the GI system?

A

Parasympathetic innervation stimulates gastric activity, and sympathetic innervation inhibits gastric activity.

82
Q

What are the major functions of the large intestine?

A

The reabsorption of water and compact materials into feces, absorption of vitamins produced by bacteria, storage of fecal material prior to defecation

ASCI 2120 Exam 3 (4 decks)

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