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BIOL 112 > Lecture 8: The Digestive System > Flashcards

Lecture 8: The Digestive System Flashcards

1
Q

what does the digestive system do

A

-acquires nutrients from the environment
-anabolism: essential compounds
-catabolism: yield energy for cells

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2
Q

what is anabolism

A

a biochemical process in metabolism where the simple molecules combine to generate complex molecules

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3
Q

what is catabolism

A

breaking down body tissues and energy stores to get more fuel for body functions

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4
Q

what are the categories of components of the digestive system (DS)

A
  1. Gastrointestinal (GI) tract: alimentary canal (AC)
    -continuous muscular tube that runs from the mouth to anus
    -digests food: breaks down into smaller fragments
    -absorbs fragments through lining into blood
  2. Accessory Organs: teeth, tongue, gall bladder and various glandular organs (salivary glands, liver, pancreas)
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5
Q

what are the 6 primary functions of the digestive system

A
  1. ingestion
  2. secretion
  3. motility
  4. digestion
  5. absorption
  6. defecation
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6
Q

what is ingestion

A

eating: occurs when food enters oral canal

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7
Q

what is secretion

A

-release of water, acids, enzymes, buffers, and salts
-by epithelium of GI tract, glandular organs, and gallbladder

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8
Q

what is motility

A

-food mixed; peristaltic movement of food along the GI tract
-food is propelled to the anus

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9
Q

what is digestion and the two types of breakdown mechanisms

A

-digestion: breakdown of ingested food into smaller pieces that are useable by body tissue
-mechanical breakdown: mastication (chewing) and shearing of food, churning food, bolus formation
-chemical breakdown: catabolic processes mediated by digestive enzymes, macromolecules are hydrolyzed into small fragments for absorption by digestive epithelium

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10
Q

what is absorption

A

-movement of digested products across digestive epithelium into interstitial fluid and lymph
-some absorbed with digestions- organic molecules, electrolytes, vitamins, minerals, and water

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11
Q

what is defecation

A

elimination of wastes (indigestible substances), microbes, cells sloughed from GIT wall, from body

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12
Q

how many layers are there in the GI tract

A

-four layers from inside-out: mucosa, submucosa, muscular layer (muscularis externa), and serosa/adventitia
-lining of AC varies by region: empty stomach= longitudinal folds, small intestine= permanent transverse fold (circular folds)

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13
Q

what are the different parts (3 sublayers) of the mucosa layer

A

inner lining of DT, made up of three sub layers:
1. digestive epithelium (moistened by glandular secretions)
2. lamina propria of alveolar tissue
3. muscularis mucosae

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14
Q

describe the digestive epithelium (in mucosa layer)

A

-epithelium is simple or stratified: depends on location, function, and stresses
a) oral cavity, pharynx, esophagus, anal canal: stratified squamous epithelium
b)stomach, small intestine, most of large intestine: simple columnar epithelium
-enteroendocrine cells which are disperesed among the columnar cells: secrete hormones that coordinate activities of GIT

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15
Q

describe the lamina propria (in the mucosa layer)

A

a layer of areolar tissue containing:
-blood vessels, lymphatic vessels, sensory nerve endings
-binds epithelium to overlying muscularis mucosae
-has mucosa-associated lymphatic tissues (MALT) for protection

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16
Q

describe the muscularis mucosae (in the mucosa layer)

A

-deep to lamin propria
-a narrow sheet of smooth muscle and elastic fibers
-give rise to folds-increase surface area for digestion and absorption

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17
Q

what is the submucosa layer of the GIT

A

-connects mucosa to muscular layer
-numerous blood and lymphatic vessels
-contain exocrine glands which secrete enzymes
-contains the submucosal neural plexus which innervates mucosa and submucosa

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18
Q

what is the muscular layer (muscularis) of the GIT

A

-mainly smooth, and some skeletal muscle cells: inner circular and outer longitudinal layers
-involved in mechanical disgestion and peristalsis
-between two muscle layers is myentric plexus
-movements coordinated by enteric nervous system (ENS)

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19
Q

what is the serosa- visceral peritoneum layer of the GIT

A

serous membrane of areolar CT covering the muscular layer

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20
Q

what does the enteric nervous system (ENS) do in the digestive system

A

enteric neurons make up bulk of the two interconnecting intrinsic nerve plexuses
-submucosal plexus: glands and smooth muscle in mucosa
-myenteric plexus: between circular and longitudinal smooth muscle layers of the muscularis- GI tract motility

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21
Q

what does the autonomic nervous system (ANS) do in the digestive system

A

-parasympathetic: vagus and sacral nerves
-sympathetic: thoracic and upper lumber segments

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22
Q

what is the protective function of the lining of the GI tract

A

-safeguards surrounding tissues against: corrosive effects of digestive acids and enzymes, mechanical stress such as abrasion, and bacteria either ingested with food or that reside in the tract

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23
Q

what is the peritoneum

A

-largest serous membrane in the body
-parietal and visceral peritoneum form the peritoneal cavity
-ascites: acculumation of fluid in the peritoneal cavity
-retroperitoneal organs: kidneys, pancreas, duodenum, ascending and descending colon
-peritonitis:

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24
Q

what are the 5 peritoneal folds

A

greater omentum, falciform ligament, lesser omentum, mesentery, and mesocolon

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25
Q

what is the greater omentum (peritoneal fold)

A

-enlargement of dorsal mesectery
-double-layered membrane (folds back on itself)
-site of adipose tissues-> beer belly

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26
Q

what is the falciform ligament (peritoneal fold)

A

stabilizes position of liver relative to diaphragm and anterior abdominal wall

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27
Q

what is the lesser omentum (peritoneal fold)

A

-conntects stomach and duodenum to the liver, stabilizing them in position
-route for blood vessels and other structures entering or leaving the liver

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28
Q

what is the mesentery (peritoneal fold)

A

-double layers of peritoneal membrane, laden with fat
-hold jejunum and ilium to posterior abdominal wall
-between the layers are blood and lymphatic vessels

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29
Q

what is the mesocolon (peritoneal fold)

A

-holds transverse and sigmoid colon to posterior abdominal wall
-route for blood and lymphatic vessels

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30
Q

what are the functins of the oral cavity

A

-sensory analysis: before swallowing
-mechanical digestion: teeth, tongue, and palatal surfaces
-lubrication: mucus and saliva
-limited chemical digestion: carbohydrates and lipids

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31
Q

what is the oral mucosa

A

-lining of oral cavity: stratified squamous epithelium
-cheeks, lips, and inferior surface of tongue: relatively thin and non-keratinized

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32
Q

content of the oral cavity

A

superior lip, superior labial frenulum, gingivae, fauces, palatoglossal arch, palatopharyngeal arch, palatine tonsil, tongue, lingual frenulu, inferior labial frenulum, oral vestibule, incisors, canines, premolars, molars, cheek, uvula, soft palate, hard palate

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33
Q

what is the superior labial freulum

A

attaches superior lip to gum (the little flap of skin at front of mouth)

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34
Q

what are gingivae

A

gums which cover tooth sockets and help to anchor teeth

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35
Q

what is the fauces

A

the opening between the oral cavity and the oropharynx

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36
Q

where is the palatoglossal arch

A

between the soft palate and base of the tongue

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37
Q

where is the palatopharyngeal arch

A

from soft palate to pharyngeal wall

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38
Q

what is the tongue

A

forms the flood of the mought, manipulates food for chewing and swallowing, shapes food, and senses taste

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39
Q

what is the lingual frenulum

A

limits the movment of the tongue posteriorly (the line of skin under your tongue (where babies can be “tongue tied”)

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40
Q

what is the inferior labial frenulum

A

attaches inferior lip to gum

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41
Q

what is the oral vestibule

A

is the space between the cheeks, lips, gums, and teeth

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42
Q

what do the incisors do (teeth)

A

cut food

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43
Q

what do the canines do (teeth)

A

tear food

44
Q

what do the premolars do (teeth)

A

crush and grind food

45
Q

what do the molars do (teeth)

A

grind food

46
Q

what is the cheek

A

forms lateral wall of oral cavity

47
Q

what is the uvula

A

prevents swallowed food from entering the nasal cavity

48
Q

what is the soft palate

A

(muscular) forms the rest of the mouths roof

49
Q

what is the hard palate

A

(bony) forms most of the roof of the mouth

50
Q

what are the functions and contents of the tongue

A

forms floor of oral cavity
~Functions: chewing,secretion of lingual lipase, analysis by touch/ temerature/ and taste receptors
~content
-anterior body
-posterior root
-frenulum of tongue (along inferior midline)
-extrinsic tongue muscles (perform all gross movements)
-intrinsic tongue muscles (smaller; perform precise movements speech, swallowing)

51
Q

what are the three sections of a tooth

A

crown, neck, and body

52
Q

what are the components of teeth

A

enamel, dentin, pulp cavity, cemetum, root canal, periodontal ligament, apical foramen, nerves, and blood supply

53
Q

what is enamel (forms occusal/biting surface?????)

A

made of calcium salts, protects the tooth from wear and tear

54
Q

what is dentin

A

calcified connective tissue
makes up the majority of the tooth

55
Q

what is the pulp cavity

A

contains pulp (connective tissue containing nerve and blood vessels)

56
Q

what is cementum

A

a bone-like sibstance that attaches the root to the periodontal ligament

57
Q

what is a root canal

A

is an extension of the pulp cavity that contains nerves and blood vessels

58
Q

what is the periodontal ligament

A

helps anchor the tooth to the underlying bone

59
Q

what is the apical foramen

A

is an opening at the base of a root canal through which blood vessels, lymphatic vessels, and nerves enter a tooth

60
Q

what are the 4 types of teeth

A

incisor, canine, premolar, and molar

61
Q

what are the incisor teeth

A

-middlemost, blade or chisel-shaped; single-roots
-clipping or cutting

62
Q

what are the canine teeth (cuspids)

A

-conical with single pointed cusp; single rooted
-tearing or slashing

63
Q

what are the premolar teeth (bicuspids)

A

-two prominent rounded cusps
-crushing, mashing, and grinding
-one or two roots

64
Q

what are the molar teeth

A

-very large, flattened crowns
-4-5 prominent, rounded cusps
-crushing and grinding
-2-3 roots

65
Q

slide 21

A
66
Q

what is the composition of saliva

A

three pairs that secrete saliva
-mostly water (97-99.5%) so hypo-osmotic
-slightly acidic (pH 6.75 to 7.00)
-electrolytes: Na+, K+, Cl-, PO4-2, HCO3-
-salivary amylase and lingual lipase
-proteins: mucin, lysozyme, and IgA
-metabolic wastes: urea and uric acid
-lysozyme, IgA, defensins, and nitric oxide from nitrates in food protect against microorganisms

67
Q

how many primary teeth are there (deciduous, milk or baby teeth)

A

20
(2I, 1C, 2M) x2 (this is upper jaw)
(2I, 1C, 2M) x2 (this is lower jaw)

68
Q

how many permanent teeth are there

A

32 teeth
(2I, 1C, 2M, 3M) x2
(2I, 1C, 2M, 3M) x2

69
Q

what are the cells of the salivary glands

A

slaivary glands are composed of two types of secretory cells
-serous cells: produce watery secretion, enzymes, ions, but of mucin
-mucous cells: produce mucus
-parotid and aubmandibular glands contain mostly serous cells, but sublingual gland consists mostly of mucous cells

70
Q

what is the pharynx

A

throat
-passageway for food
-skeletal muscles
-food moves from mouth to oropharynx

71
Q

what are the regions of the pharynx

A

pasopharynx, oropharynx, and laryngopharynx

72
Q

what is the esophpagus

A

-a flot hollow muscular tube
-from laryngopharynx to stomach
-posterior to cricoid cartilage, trachea, and heart
-collapsed when not involved in food propulsion

73
Q

what is deglutition

A

swallowing

74
Q

how many muscles work in deglutition

A

it involves coordination of 22 muscle groups

75
Q

what are the two phases of deglutition

A

-buccal phase: viluntary contraction of tongue
-pharyngeal-esophageal phase: involuntary phase that primarily involves vagus nerve, controlled by swallowing center in medulla and lower pons

76
Q

what are the 5 steps in deglutition

A
  1. buccal phase: the upper esophageal sphincter is contracted (closed), the tongue presses against the hard palate forcing the food bolus into the oropharynx
    2.pharyngeal-esophageal phase begins: the tongue blocks the mouth, the soft palate and its uvula rise clsoing off the nasopharynx, larynx rises so that the epiglottis blocks the trachea, upper esophageal sphincter relaxes; food enters the esophagus
  2. pharyngeal-esophageal phase continues: the constrictor muscles of the pharynx contract forcing food into the esophagus inferiorly, upper esophageal sphincter contracts after food enters
  3. peristalsis moves food thorugh the esophagus to the stomach
  4. the gastroesophageal sphincter surrounding the cardial orfice opens, after food enters the stomach the sphincter closes preventing regurgitation
77
Q

what is the stomach

A

-extnads between T7 and L3
-mechanical digestion: muscular contractions (breakdown bolus)
-chemical digestion: acids and enzymes (breakdown bolus)

78
Q

what is chyme

A

bolus mixed with acidic secretions of the stomach

79
Q

anatomically the stomach…

A

-short lesser curvature: medial surface
-long greater curvature: lateral surface
rounded anterior and posterior surfaces

80
Q

what are the regions of the stomach

A

-cardia: superomedial part; mucous glands
-fundus: contacts with diaphragm
-body: largest region; food mixes with secretions
-pyloric part: between body and duodenum

81
Q

what is rugae (stomach)

A

-folds in mucosa of empty stomach
-flatten out as stomach fills
-allow for expansion of gastric lumen; up to 50x its empty size

82
Q

histology of the stomach

A

-simple columnar epithelium
-epithelium: secretory sheet
-gastric pits: depressions opening into gastric surface
-mucous cells: meck (base) of each gastric pit; actively divide replacing superficial cells

83
Q

what are gastric pits

A

-gastric pits: depressions opening into gastric surface
-mucous cells: meck (base) of each gastric pit; actively divide replacing superficial cells

84
Q

what are gastric glands

A

fundus and body of stomach
-extend deep into underlying lamina propria
-gastric pits communicate with numerous gastric glands
-parietal cells nad cheif cells

85
Q

what are parietal cells (histology of stomach)

A

proximal portions of gastric glands
-secrete intrinsic factor: glycoprotein that absorbs vitamin B12
-secrete HCl (hP 1.3-3.5)
which activate pepsinogen, denatures proteins, destroys bacteria

86
Q

what are chief cells (histology of stomach)

A

they are at the base of gastric glands
-secrete pepsinogen: converted to pepsin by HCl in gastric lumen and by pepsin itself
-secrete gastric lipase

87
Q

what do chief cells in infants secrete

A

-rennin (chymosin): moagulates milk proteins (casein)
-gastric lipase: digest milk fats

88
Q

where are pyloric glands

A

pyloric part of stomach

89
Q

what are enteroendocrine cells (stomach)

A

produce several hormones

90
Q

what are G cells (stomach)

A

produce gastrin
-stimulates secretion by parietal and chief cells
-stimulates contractions of gastric wall

91
Q

what are D cells (stomach)

A

release somatostatin
-inhibits release of gastrin

92
Q

describe chemical digestion in the stomach

A

-salivar amylase: carbohydrates
-lingual lipase: lipids
-as stomach contents become more fluid: pH approaches 2.0, digestive activities of pepsin increases

93
Q

what are the main functions of the stomach

A
  1. mixez saliva, food, and gastric juice to form chyme
  2. serves as a resevoir for food before release into the small intestine
  3. secretes gastric juice, which contains HCl, pepsin, intrsinsic factor, and gastric lipase
  4. secretes gastrin into the blood
94
Q

what is the digestive activity of the muscularis

A

mixing waves (gentle peristaltic movements)
-churns and physically breaks down food nad mixes it with gastric juice, forming chyme, forces chyme through pyloric sphincter

95
Q

what is the digestive activity of the pyloric sphincter

A

opens to permit passage of chyme into duodenum
result: regulates passage of chyme from stomach to duodenum; prevents backflow of chyme from duodenum to stomach

96
Q

check slide 32 from lecture

A
97
Q

what is the site of production, stimulus for production, target organ, and activity of cholecystokinin (CCK)

A

-site of production: duodenal mucosa
-stimulus for production: fatty chyme (also partially digested proteins)
-target organ: stomach, liver, pancreas, gallbladder, hepatopancreatic sphincter
-activity: inhibits stomach’s secretory activity, potentiates secretin’s actions on the organs, increases output to enzyme-rich pancreatic juice, stimulates organ to contract and expel stored bile, relaxes sphincter to allow entry of bile and pancratic juice into the duodenum

98
Q

what is the site of production, stimulus for production, target organ, and activity of glucose-dependent insulinotropic peptide (GIP) (or gastric inhibitory peptide)

A

-site of production: duodenal mucosa
-stimulus for production: fatty chyme
-target organ: stomach & pancreas (beta cells)
-activity: inhibits HCl production (minor effect), stimulates insulin release

99
Q

what is the site of production, stimulus for production, target organ, and activity of gastrin

A

-site of production: stomach mucosa (G cells)
-stimulus for production: food (particularly partially digested proteins) in stomach (chemical stimulation); acytylcholine ACh released by nerve fibers
-target organ: stomach (parietal cells), small intestine, ileocecal valve, large intestine
-activity: increases HCl secretion, stimulates gastric emptying (minor effect), stimulates contraction of intestinal muscle, relaxes ileocecal valve, stimulates mass movements

100
Q

what is the site of production, stimulus for production, target organ, and activity of histamine

A

-site of production: stomach mucosa
-stimulus for production: food in stomach
-target organ: stomach
-activity: activates parietal cells to release HCl

101
Q

what is the site of production, stimulus for production, target organ, and activity of intestinal gastrin

A

-site of production: duodenal mucosa
-stimulus for production: acidic and partially digested foods in duodenum
-target organ: stomach
-activity: stimulates gastric glands and motility

102
Q

what is the site of production, stimulus for production, target organ, and activity of motilin

A

-site of production: duodenal mucosa
-stimulus for production: fasting: periodic release ever 1.5-2 hours by neural stimule
-target organ: proximal duodenum
-activity: stimulates migrating motor complex

103
Q

what is the site of production, stimulus for production, target organ, and activity of secretin

A

-site of production: duodenal mucosa
-stimulus for production: acidic chyme (also partially digested proteins and fats)
-target organ: stomach, pancreas, & liver
-activity: inhibits gastric gland secretion and gastric motility, increases output of pancreatic juice rich in bicarbonate ions; potentiaties CCK’s action, increases bile output

104
Q

what is the site of production, stimulus for production, target organ, and activity of serotonin

A

-site of production: stomach mucosa
-stimulus for production: food in stomach
-target organ: stomach
-activity: causes contraction of stomach muscle

105
Q

what is the site of production, stimulus for production, target organ, and activity of somatostatin

A

-site of production: stomach mucosa; duodenal mucosa
-stimulus for production: food in stomach; stimulation by sympathetic nerve fibers
-target organ: stomach, pncreas, small intestine, gallbladder & liver
-activity: inhibits gastric secretion of all products, inhibits secretion, inhibits GI blood flow; thus inhibits intestinal absorption, inhibits contraction and bile release

106
Q

what is the site of production, stimulus for production, target organ, and activity of vasoactive intestinal peptide (VIP)

A

-site of production: enteric neurons
-stimulus for production: chyme containing partially digested foods
-target organ: small intestine, pancreas, stomach
-activity: stimulates budffer secretion, increases blood flow through intestinal capillaries, relaxes intestinal smooth muscle, increases secretion, inhibits acid secretion

BIOL 112 (21 decks)

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