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HAN 202 > Chapter 23: Digestion > Flashcards

Chapter 23: Digestion Flashcards

1
Q

Digestion

A
  • > to obtain energy for ATP production through food sources
  • > raw materials needed for building and repair
  • > needs to be converted to cellular level
  • > mechanical and chemical digestion
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2
Q

Two groups of organs

A
  1. Alimentary canal (GI tract)

2. Accessory digestive organs

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3
Q

Alimentary canal (GI tract)

A
  • digests and absorbs food

- mouth, pharynx, esophagus, stomach, small intestine, and large intestine

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4
Q

Accessory digestive organs

A
  • teeth, tongue, gallbladder

- digestive glands: salivary glands, liver, pancreas

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5
Q

Digestive processes

A
  1. Ingestion-eating
  2. propulsion-swallowing, peristalsis
  3. mechanical digestion
  4. chemical digestion-enzymes
  5. absorption
  6. defecation
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6
Q

Accessory digestive organs

A

Teeth:
-Teeth do much of mechanical work of digestion.

-Human teeth include sharp incisors & cuspids which tear and grasp food. Molars crush and grind

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7
Q

Accessory digestive organs

A

Tongue:
-Positioning and mixing of food

  • Formation of the bolus
  • Initiation of swallowing, speech, and taste
  • Surface bears papillae for friction, licking, taste buds, secretes lingual lipase
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8
Q

Salivary glands– Intrinsic glands

A

are scattered in the oral mucosa, keep mouth moist

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9
Q

Salivary glands– Extrinsic

A

-produce majority of saliva.
Functions:
-cleanses mouth

  • moistens and dissolves food chemicals
  • contains enzymes (salivary amylase) that begin the breakdown of starch
  • contain chemicals (IgA antibodies and defensins) that protects against micro organisms
  • The brain stem send impulses along parasympathetic fibers to activation secretions. Sympathetic NS inhibits saliva production
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10
Q

Digestive processes: Mouth

A
  • Ingestion
  • mechanical digestion: mastication is partly voluntary, partly reflexive
  • chemical digestion: salivary amylase and lingual lipase
  • absorption- only certain medications
  • propulsion- deglutition (swallowing)
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11
Q

pharynx

A
  • Oropharynx and laryngopharynx (nasopharynx no digestive role)
  • Allow passage of food, fluids, and air
  • Skeletal muscle layers: inner longitudinal, outer pharyngeal constrictors
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12
Q

Histology of alimentary canal

A

4 basic layers (tunics)- from esophagus to anal canal

  • Mucosa: secretes mucous, enzymes & hormones, absorption and protection
  • Submucosa: houses vessels, nerves and lymph vessels, made up of CT
  • Muscularis externa: -2 layers of smooth MM (circular/longitudinal), responsible for segmentation and peristalsis
  • Serosa: outermost layer, made up of CT

**exception: in esophagus the adventia replaces the serosa layer

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13
Q

Esophagus

A
  • flat muscular tube from laryngopharynx to stomach
  • bolus of food (aided by mucous) travels through esophagus by smooth MM contractions -peristalsis
  • joins stomach at the cardiac orifice
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14
Q

Deglutition (swallowing)

A

-> involves the tongue, soft palate, pharynx, esophagus, and 22 muscle groups

  • > Buccal Phase:
  • voluntary contraction of the tongue, forces bolus into oropharynx
  • > Pharyngeal-esophageal phase:
  • involuntary
  • control center in the medulla and lower pons
  • all routes are blocked, soft palate blocks nasoph, epiglottis covers trachea
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15
Q

Deglutition: Buccal Phase

A

*voluntary contraction of the tongue, forces bolus into oropharynx

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16
Q

Deglutition: Pharyngeal-esophageal phase:

A
  • involuntary
  • control center in the medulla and lower pons
  • all routes are blocked, soft palate blocks nasoph, epiglottis covers trachea
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17
Q

Peristalsis

A
  • adjacent segments of alimentary tract organs alternately contract and relax, which moves food along the tract distally
  • video-flouroscopy
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18
Q

Stomach: Gross anatomy

A
  • Cardial region (cardia): surrounds the cardiac orifice
  • Fundus: dome-shaped region beneath the diaphragm
  • Body: midportion
  • Pyloric Region: pylorus is continuous with the duodenum through the pyloric valve (sphincter)
  • greater curvature: convex lateral surface
  • Lesser surface: concave medial surface
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19
Q

Cardial region (cardia)

A

surrounds the cardiac orifice

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20
Q

fundus

A

dome-shaped region beneath the diaphragm

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21
Q

body

A

midportion

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22
Q

Pyloric region

A

pylorus is continuous with the duodenum through the pyloric valve (sphincter)

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23
Q

Greater curvature

A

convex lateral surface

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24
Q

Lesser curvature

A

concave medial surface

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25
Q

Stomach: microscopic anatomy

A
  • Mucosa (lining of stomach):
  • produces mucus which traps bicarbonate-rich fluid beneath it

*gastric pits lead into gastric glands (produce stomach secretions)

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26
Q

Gastric glands

A

Cell types:
* Mucous neck cells (secrete thin, acidic mucus)

  • parietal cells secrete HCl and intrinsic factor
  • chief cells- pepsinogen
  • enteroendocrine cells (g cells): gastrin
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27
Q

gastric gland secretions: parietal cell secretions

A

-Glands in the fundus and body produce most of the gastric juice

  • Parietal cell secretions:
  • HCl: pH 1.5–3.5 denatures protein in food, activates pepsin, and kills many bacteria

*Intrinsic factor: protein required for absorption of vitamin B 12 in small intestine

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28
Q

Chief cell secretions;

A
  • produce pepsinogen
  • activated to pepsin by HCl and by pepsin itself (positive feedback mechanism)
  • secrete lipases (fat digestion)
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29
Q

enteroendocrine cells

A
  • Paracrines (act locally)
    • Serotonin and histamine
  • Hormones
    • Somatostatin and gastrin (G cells) (regulates secretions and mobility)

*gastric secretion is controlled by both neural and hormonal mechanisms

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30
Q

Mucosal Barrier

A
  • Layer of bicarbonate-rich mucus
  • Tight junctions between epithelial cells
  • Damaged epithelial cells are quickly replaced by division of stem cells
  • Peptic or gastric ulcers: erosion of the stomach wall
    • Most are caused by H pylori bacteria
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31
Q

digestive processes in the stomach

A
  • Physical digestion (3 layers of muscle)
  • Denaturation of proteins (HCl)
  • Enzymatic digestion of proteins by pepsin
  • Secretes intrinsic factor required for absorption of vitamin B12
  • *Lack of intrinsic factor-> pernicious anemia

-Delivers chyme (product of its activity) to the small intestine

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32
Q

Neural reflex pathways

A

-control of digestive activity are both intrinsic and extrinsic

cephalic phase: initiated by stimuli arising inside or outside the GI tract and involve CNS centers. usually from stimuli outside the GI tract

gastric phase: mediated inside GI tract by local stimuli (local distention, pH, presence of substrates). 3-4 hrs after food enters stomach

intestinal phase: controls rate of emptying into intestines

33
Q

cephalic phase

A

initiated by stimuli arising inside or outside the GI tract and involve CNS centers. usually from stimuli outside the GI tract

34
Q

Gastric phase

A

mediated inside GI tract by local stimuli (local distention, pH, presence of substrates). 3-4 hrs after food enters stomach

35
Q

intestinal phase

A

controls rate of empyting into intestines

36
Q

Response of the stomach to filling

A
  • stretches to accomodate incoming food
  • reflex-mediated receptive relaxation: coordinated by the swallowing center of the brain stem
  • gastric accommodation: Plasticity (stress-relaxation response) of smooth muscle, can stretch without contracting
37
Q

Intestinal phase-stimulatory

A

brief filling of initial part of small intestine of partially digested food

38
Q

Intestinal phase: inhibitory

A

enterogastric reflex” – a trio of reflexes that puts “brakes” on gastric activity to protect sm intestine from excessive acidity

39
Q

dumping syndrome

A

seen in stomach volume reduction surgeries (nausea/vomiting)

40
Q

gastric contractile activity

A
  • Peristaltic waves move toward the pylorus
  • Basic electrical rhythm (BER) initiated by pacemaker cells (cells of Cajal)
  • Distension and gastrin increase force of contraction
  • Most vigorous near the pylorus
  • Chyme is either:
  • Delivered in ~ 3 ml spurts to the duodenum, or
  • Forced backward into the stomach
41
Q

Vomiting (emesis)

A
  • Protective reflex: removes toxic material from GI tract before being absorbed
  • triggered by extreme stretching of stomach or irritant such as bacteria, excessive alcohol, spicy foods and certain drugs
  • vomiting reflex located in medulla (emetic center)
  • Prior nausea, diaphragm & abdominal muscles contract increasing intra-abdominal pressure, gastroesophageal sphincter relaxes, contents are forced out of stomach
42
Q

Stimuli that regulate gastrointestinal tract activity are generated by

A

the CNS, chemoreceptors in the gut, the enteric nerve plexus

43
Q

small intestine: gross anatomy

A
  • major organ of digestion and absorption
  • 2-4 m long; from pyloric sphincter to ileocecal valve (6-7 m long in cadaver- height of 2 story building)
  • subdivisions:
    1. duodenum- chemical digestion
    2. jejunum- absorption
    3. ileum- vitamin absorption
44
Q

Duodenum- chemical digestion

A

-small intestine

  • the bile duct and main pancreatic duct
  • join at the hepatopancreatic ampulla
  • enter the duodenum at the major duodenal papilla
  • hepatopancreatic sphincter controls entry of bile and pancreatic juice
45
Q

structure of small intestine

A
  • increase surface area of proximal part for nutrient absorption
  • Circular folds: force chyme to slowly spiral through lumen
  • villi: motile fingerlike extensions
  • villus epithelium: simple columnar absorptive cells (enterocytes), goblet cells

-microvilli: projections (brush border) of absorptive cells, brush border enzymes (further breakdown of proteins and carbs )

46
Q

small intestine: Circular folds

A

force chyme to slowly spiral through lumen

47
Q

small intestine: Villi

A

motile fingerlike extensions

*villus epithelium: simple columnar absorptive cells (enterocytes), goblet cells

48
Q

small intestine: Microvilli

A

projections (brush border) of absorptive cells, brush border enzymes (further breakdown of proteins and carbs )

49
Q

intestinal crypts

A

Intestinal crypt epithelium (like gastric pits)

-Secretory cells:
produce intestinal juice (peptidase, maltase, lactase, sucrase)

  • Enteroendocrine Cells – (not to be confused with enterendocrine of stomach)
  • secretin & cholecystokinin (CCK)

Lymphocytes:
T-cells that release cytokines that kill infected cells

Paneth cells:
Secrete antimicrobial agents (defensins and lysozyme)

Stem cells:
Dividing cells which become specialized

50
Q

intestinal crypts: Secretory cells

A

produce intestinal juice (peptidase, maltase, lactase, sucrase)

51
Q

intestinal crypts: -Enteroendocrine Cells

A

(not to be confused with enterendocrine of stomach)

*secretin & cholecystokinin (CCK)

52
Q

intestinal crypts: Lymphocytes

A

T-cells that release cytokines that kill infected cells

53
Q

intestinal crypts: Paneth cells

A

Secrete antimicrobial agents (defensins and lysozyme)

54
Q

intestinal crypts: stem cells

A

Dividing cells which become specialized

55
Q

liver

A
  • Largest gland in the body (3 lbs)
  • Four lobes

Functions:

  • Stores glycogen and vitamins (fat soluble)
  • Detox of ammonia
  • Produces bile

Exceptional regenerative capacity of liver, can regenerate to former size in 6-12 months. This is why live donor transplants are a viable option.

56
Q

bile

A
  • Missing ingredient to attack fatty foods, contains:
  • Bile salts: cholesterol derivatives that function in fat emulsification and absorption
  • Bilirubin: waste product from heme
  • Facilitate fat and cholesterol absorption
57
Q

The gallbladder

A
  • Thin-walled muscular green sac on the ventral surface of the liver
  • Stores and concentrates bile
  • Releases bile via the cystic duct, which flows into the bile duct

Bile extracts cholesterol from body, if too much cholesterol it crystallizes forming gallstones

58
Q

pancreas

A

->Endocrine function: Secrete insulin and glucagon

  • > Exocrine function
  • Secrete pancreatic juice
  • Pancreatic juice consisting of enzymes for digestion (digests carbohydrates, fats, proteins)
  • Pancreatic juice consisting of bicarbonate ions (neutralizes chyme)
59
Q

Pancreatic juice

A
  • Watery alkaline solution (pH 8) neutralizes chyme
  • Electrolytes (primarily HCO3–)
  • Enzymes
  • Proteases (trypsin) - proteins
  • Amylase - COH
  • Lipase - lipids

Nucleases – nucleic acids

60
Q

regulation of bile and pancreatic secretions

A
  • > Chyme entering duodenum releases:
  • Secretin and Cholecystokinin (CCK)
  • > CCK induces secretion of pancreatic juice (enzymes) and causes gallbladder to contract
  • > Secretin –secretion of watery bicarbonate rich pancreatic juice
  • > Bile secretion is stimulated by Bile salts
61
Q

Motility of the small intestine: Segmentation (massaging)

A
  • after a meal
  • mixes and moves contents slowly and steadily toward the ileocecal valve
  • intensity is altered by long and short reflexes
62
Q

motility of the small intestine: peristalsis

A
  • between meals
  • occurs late in intestinal phase after absorption has occurs
  • meal remnants, bacteria, and debris are moved to the large intestine
63
Q

This substance secreted by the pancreas helps neutralize chyme.

A

bicarbonate

64
Q

Large intestine (colon)

A
  • shorter but wider than small intestine
  • major digestive function is to absorb remaining water
  • stores indigestible food
  • houses goof bacteria
  • no digestive enzymes, minimal absorption
  • takes 12 to 24 hours to move through the large intestine
65
Q

Large intestine

A
  • Teniae coli: 3 bands of longitudinal smooth muscle in the muscularis
  • Haustra: pocketlike sacs caused by the tone of the teniae coli
  • epiploic appendages: fat-filled pouches which hang from large intestine

Mesenteries of abdominal digestive organs: omentum, mesocolon, mesentary. membrane sheets that anchor the digestive tract

66
Q

large intestine

A

Regions:
*Cecum (pouch with attached appendix)

  • Colon (ascending, transverse, descending, sigmoid)
  • Rectum
  • Anal canal
67
Q

Rectum

A

3 rectal valves stop feces from being passed with gas

-goblet cells-produce mucus

68
Q

anal canal

A
  • the last segment of the large intestine

- superficial venous plexuses

69
Q

sphincters

A

internal anal sphincter- smooth muscle

external anal sphincter- skeletal muscle

70
Q

bacterial flora

A
  • located in colon
  • ferment indigestible carbs
  • release irritating acids and gases
  • synthesize B complex vitamins and vitamin K (needed by the liver to produce clotting proteins)
71
Q

functions of the large intestine

A
  • vitamins, water, and electrolytes are reclaimed
  • major function is propulsion of feces toward the anus
  • colon is not essential for life
72
Q

motility of the large intestine

A
  • > Haustral contractions:
  • slow segmenting movements

*occur every 30 min, move material from 1 haustrum to the next

  • > Mass movements:
  • slow intense peristalsis movement, 3-4/day
  • usually after eating
  • bulk or fiber in the diet strengthens colon contractions (diverticulosis)
73
Q

Why is the small intestine well adapted for nutrient absorption?

A

Large surface area due to the presence of the villi, and microvilli.

74
Q

In terms of gastrointestinal function, the large intestine’s greatest contribution is:

A

absorption of water

75
Q

defecation

A
  • mass movements force feces into rectum
  • distension initiates spinal defecation reflex
  • parasympathetic signals:
  • stimulate contraction of the sigmoid colon and rectum
  • relax the internal anal sphincter

-conscious control allows relaxation of external anal sphincter

76
Q

chemical digestion and absorption of carbs

A

Digestive enzymes:

*Salivary amylase, pancreatic amylase, and brush border enzymes (dextrinase, glucoamylase, lactase, maltase, and sucrase)

*Lactose Intolerant – the undigested disaccharides create osmotic gradient that prevents water from being absorbed -> diarrhea.
Treatment – add lactase enzyme

77
Q

chemical digestion and absorption of proteins

A
  • enzymes: pepsin in the stomach
  • pancreatic proteases: trypsin, chymotrypsin, and carboxypeptidase

-brush border enzymes:
aminopeptidases, carboxypeptidases, and dipeptidases

78
Q

chemical digestion and absorption of lipids

A

Pre-treatment- emulsification by bile salts

  • enzymes: pancreatic lipase
  • absorption of glycerol and short chain fatty acids
79
Q

Malabsorption of nutrients

A

Gluten-sensitive enteropathy (celiac disease)

  • Gluten damages the intestinal villi and brush border
  • Results in bloating, diarrhea, pain and malnutrition
  • Treated by eliminating gluten from the diet (all grains but rice and corn)

HAN 202 (13 decks)

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