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Anatomy and Physiology-DNP > Structure and Function of Digestive System > Flashcards

Structure and Function of Digestive System Flashcards

1
Q

GI Tract

A
  • Small intestine: breakdown to absorbable components; export to liver for further process/storage
  • substances that aren’t absorbed are passed along the large intestine; fluid waste is excreted by the kidney, solid waste is excreted in feces
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2
Q

GI histology

A
  • 4 layers: vary in thickness
  • Mucosa (inner most layer)
  • Submucosa
  • Muscularis:
  • Serosa or adventitia (outer most layer) : Connective tissue, peritoneum
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3
Q

GI tract plexus

A

-Enteric plexus: intrinsic nerves located solely in GI tract and controlled by ANS-this compromises three nerve plexuses-located in different layers
-Submucosal plexus: located in muscularis
-Myenteric plexus
-Subserosal plexus
These nerve circuits regulate motility reflexes, blood flow, absorption, secretions, and immune response

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4
Q

Taste buds

A

-Sour, salty, bitter and sweet

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5
Q

Salivary glands

A
  • Submandibular, sublingual, parotid
  • secrete 1L of saliva a day
  • Salivation is controlled by sympathetic and parasympathetic
  • Cholinergic pathways stimulate salivation
  • pH of saliva is around 7.4 to neutralize bacterial acid and prevent tooth decay
  • Contains IgA which helps prevent infection
  • Water w/ mucus, Na, bicarbonate, chloride, K, and salivary a-amylase (carb digestion)
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6
Q

Swallowing

A
  • reticular formation of the brainstem, includes insula/claustrum and cerebellum
  • Swallowing and respiratory center provide coordinating innervation
  • Superior constrictor muscle of pharynx contracts, prevents movement of food into nasopharynx
  • Respiration inhibited and epiglottis slides downward to prevent bolus from entering larynx and trachea
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7
Q

Peristalsis

A
  • Mix of muscles: striated/smooth which are activated in downward sequence
  • Stimulated afferent fibers distributed along the length of esophagus
  • Done in two phases
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8
Q

Upper esophageal sphincter

A
  • Aide in swallowing

- prevents entry of air into the esophagus during respiration

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9
Q

Lower esophageal sphincter

A
  • Aid in swallowing
  • prevents regurgitation from stomach
  • Esophageal phase of swallowing is involuntary
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10
Q

Stomach

A
  • muscle layers: longitudinal, circular (most prominant), oblique (least complete)
  • Muscle layers are thicker in the body and antrum where food is mixed
  • supplied w/ blood via celiac artery-very vascular
  • Spleen and gastric veins empty into stomach
  • innervated by PSN and SNS of the ANS systems. Some fibers are extrinsic-controlled by brain and intrinsic controlled by local stimuli
  • Mucosa is impermeable to water but can absorb ETOH and ASA
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11
Q

Boundaries of the stomach

A
  • Cardiac orifice, pyloric sphincter-lower end leading to duodenum, pylorus
  • Functional areas: fundus(upper), body (middle) and antrum (llower)
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12
Q

Musclaris of the stomach

A
  • Contains the oblique, circular and longitudinal muscle layers
  • Serosa, musclaris, mucosa and submucosa layers by outer to inner
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13
Q

Gastric motility

A
  • swallow
  • Gastrin
  • cholecystokinin
  • Motilin
  • Secretin
  • Gastric emptying
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14
Q

Gastrin and Motilin and vagus nerve

A
  • Aid in gastric motility

- increase contractions by making the threshold potential of muscle fibers less negative

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15
Q

Cholecystokinin

A
  • aid in gastric motility
  • stimulated by fat digestions by the duodenum and the pancreas; inhibits gastric motility and decreases gastric emptying so fats aren’t emptied at a rate faster than rate of bile and enzyme secretion
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16
Q

Gastric secretion

A
  • mucus, acid, enzymes, hormones, intrinsic factor, gastroferrin
  • Intrinsic factor is necessary for absorption of vit. B12 and gastroferrin facilitates the small intestine absorption of iron
  • Intrinsic factor is required for absorption of Vit. B12
  • Pernicious anemia is caused by the failure to absorb Vit. B12.
  • Composition of gastric juices depends on volume and flow rate (K levels higher in gastric juices than in plasma)
  • Rate of secretion higher pm lowest in am
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17
Q

Mucus in gastric secretion

A
  • Mucus: covers the mucosa, acid sensors form a protective barrier against acid and proteolytic enzymes which would otherwise damage the mucosa
  • Provides a barrier and protects
  • Quality and quantity of mucus and the tight junction between the epithelial cells makes the gastric mucosa impermeable to acid-could break from exposure to ASA, NSAIDS, H. Pylori, ETOH
  • Can cause inflammation and ulceration
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18
Q

Acid in gastric secretion

A
  • Dissolves food, act as a bacteriocide, convert pepsinogen to pepsin
  • acid secretion is stimulated by acetylcholine, gastrin, and histamine
  • Vagus nerve releases acteylcholine and stimulates the secretion of histamine
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19
Q

Pepsin

A
  • acteylcholine is the strongest stimulation for pepsin secretion
  • Pepsinogen is broken down to pepsin
  • one of the main digestive enzymes
  • located in stomach
  • breaks down proteins to amino acids
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20
Q

Gastric Pits and Gastric glands

A
  • gastric pits: glands empty into. Found in the mucosa of the fundus and body of stomach
  • Gastric glands: parietal cells (hydrochoric acid and intrinsic factor), chief cells (pepsinogen), G cells (gastrin), Enterochromaffin (histamine), D cells (somatostatin)
  • All aid in gastric secretion
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21
Q

Hormones and Gastric secretion

A
  • inhibited by unpleasant odors and taste
  • rage, fear, or pain inhibit PSN impulses
  • Increased secretions w/ aggression, hostility-may contribute to gastric pathology
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22
Q

Histamine (gastric secretion)

A
  • stores in gastric mucosa. Histamine receptors in gastric mucosa are H2 receptors
  • Histamine plays a role in gastric secretion by helping to induce the production of acid in the stomach
  • Enterochromaffin-like cells or ECL cells release histamine
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23
Q

Prostaglandins and gastric secretion

A

-inhibit gastric motility secretion-inhibit acid secretion

24
Q

Phases of gastric secretion

A
  • Cephalic phase
  • Gastric phase
  • Intestinal phase
25
Q

Cephalic phase

A
  • Anticipatory and sensory experiences. Mediated by vagus nerve through the myenteric plexus
  • Acetylcholine stimulates the parietal and chief cells to release pepsinogen and acid
  • G cells of the antrum release gastrin into the bloodstream which goes to gastric glands stimulating acid and pepsinogen secretion
26
Q

Gastric phase

A
  • food moves into the stomach via 2 stimuli have a stimulatory effect
  • -distention of the stomach
  • -presence of digested proteins
  • Vagus and enteric nerve plexus are stimulated by the distention and contribute to gastric secretion.
  • Can be blocked by atropine
  • Protein breakdown stimulating the release of gastrin from G cells in the antrum
  • proteins in the stomach buffer the acidic gastric juice and increase gastric ph. Caffeine can stimulate secretion
27
Q

Intestinal phase

A
  • movement of chyme to the duodenum
  • this phase indicates the slow down of gastric secretory response and appears to be normally mediated by a hormone-entero-oxyntin
  • Gastric inhibitory peptide decrease gastric motility and secretion of pepsin and acid
  • Intestinal phase is limited by acidic chyme in the duodenum that tends to imhibit gastric secretion and gastric motility
  • Acid in the duodenum stimulates the release of hormones that inhibit acid secretion while stimulating pepsinogen secretion. On of these hormones is cholecystokinin which inhibits gastrin stimulated by acid production
28
Q

Small intestine

A
  • 5-6m long
  • three segments: duodenum, jejunum, ileum
  • peritoneum
  • ileocecal valve
  • ANS innervates small intestine
  • PSN: Mediates secretion, motility, pain sensation, and intestinal reflexes
  • SNS: inhibits motility and produces vasoconstriction
29
Q

Duodenum

A
  • located behind peritoneum.

- Food is mixed w/ digestive juices from liver and pancreas

30
Q

Ileum/jejunum

A

-suspended by the mesentary which facilitates intestinal motility and supportive blood vessels, nerves and lymphatics

31
Q

Peritoneum

A

membrane surrounding the organs of abdominal and pelvic cavities
-Peritonitis: bowel perf or after surgery

32
Q

mucosal folds in the small intestine

A

-slow the passage of food; provide time for digestion and absorption. Seen most in jejunum and upper ileum

33
Q

Microvilli and villi: small intestine

A

-Increase surface area which increases absorption in the GI tract

34
Q

Intestinal digestion and absorption

A
  • hydrochloric acid
  • pepsin
  • pancreatic enzymes
  • intestinal enzymes
  • bile salts
  • Chyme: moves to the duodenum which contains particles of undigested food
  • Intestinal mucosa absorbs nutrients to the bloodstream
  • HCL and pepsin break down food fibers and proteins
35
Q

Pancreatic enzymes

A
  • continue to digest in the small intestine
  • Pancreatic enzymes, intestinal enzymes, and bile salts breakdown carbs to monsaccharides, and diasaccharides, proteins to amino acids and fats to fatty acids
  • Carbs and proteins are transported to the liver via the portal vein.
36
Q

Intestinal digestion absorption: proteins

A
  • protein breakdown in the small intestine by pancreatic enzymes trypsin, chymotrypsin, carboxypeptidases
  • Proteins are broken down to amino acids which are transported by a carrier at the basal membrane
  • Decreased proteolytic enzymes-decreased protein absorption
37
Q

Potassium and small intestine

A
  • most K secretion occurs in the colon
  • b/c of K secretion in the colon and the exchange of Cl- for bicarb, prolonged diarrhea results in hypokalemia metabolic acidosis
38
Q

Intestinal motility

A

-Movements of small intestine facilitate digestion and absorption
-segmentation
-Peristalsis
-ileogastric reflex
intestinoinstestinal reflex
-Gastroileal reflex

39
Q

Large intestine

A
  • cecum,
  • appendix
  • colon (ascending, transverse, descending, sigmoid)
  • rectum, anusl
40
Q

Large intestine

A
  • ileocecal valve and o beirne sphincter prevent backflow
  • Haustra-outpouchings of LI
  • Gastrocolic-promote movement and propulsion of entire colon (gastrin & cholecystokinin help w/ this reflex)
  • absorption and epithelial transport (electrolytes) occurs in cecum and LI (colon)
41
Q

GI absorption

A
  • Chronological order
  • Stomach: water, alcohol
  • Duodenum: Iron, Ca, fats, sugar, water, protein, vitamins, Mg, Na
  • Jejunum: sugars, protein
  • ileum; bile salts, vit. B12, chloride
  • colon: water, electrolytes
42
Q

Intestinal bacteria

A
  • # and types of bacteria differ throughout GI tract-increase number from stomach to colon
  • stomach: kills and inhibits growth
  • bile acid-suppresses growth
  • low concentrations in jejunum and duodenum-streptococci, lactobacilli, staph and enterobacteria,
  • bacteriodes, closteridia, anaerobic lactobacillia and coliforms are found in ileum to cecum
  • Anaerobes constitute 1/3 of solid bulk feces
43
Q

Accessory organs of digestion

A
  • liver, gallbladder, and pancreas

- liver: bile-necessary for fat absorption and digestion-stored in gallbladder

44
Q

Liver

A
  • Largest organ: right and left lobes
  • metabolic functions: large amount of blood via hepatic artery (oxygenated), hepatic portal vein (deoxygenated-70% blood supply)
  • Glisson capsule: contains blood vessels, lymphatics, nerves-liver disease or distention of this-pain and fluid into peritoneal space
45
Q

Liver lobules

A
  • hepatocytes: functional cells of liver-regeneration-
  • lipocytes-store lipids, vit,.A
  • sinusoids-
46
Q

Liver cells

A
  • kuffer-line sinusoids-phagocytic-tissue macrophages which are bacteriocidal and important in bilirubin production
  • stellate-contain retinoids (vit. A)-contribute to liver injury, remove foreign substance
  • pit-NK-important for tumor defense
47
Q

Secretion of bile salts

A
  • conjugated bile salts-required for intestinal emulsification and absorption of fats
  • most bile salts-absorbed in terminal ileum and removed to liver through portal circulation
  • Recycled-enterohepatic circulation
48
Q

metabolism of bilirubin

A
  • byproduct of destruction of aged RBC (heme and globin)
  • Globin is degraded to amino acids and recycled to make new proteins
  • Heme is converted to billverdin by cleavage of iron. Iron is attached to transferrin is stored in the liver or used to make new RBC’s
  • Biliverdin is converted to bilirubin released into the plasma.
  • In the plasma, bilirubin binds to albumin-termed unconjugated (free) and is lipid soluble
49
Q

unconjugated bilirubin

A
  • Unconjugated bilirubin moves from the plasma to the sinusoids and into the hepatocytes where it binds with glucuronic acid to form conjugated bilirubin.
  • Conjugated bilirubin reaches the distal ileum and colon, its deconjugated by bacteria and converted to urobilinogen-excreted in the urine.
50
Q

Vascular and Hematologic Liver Functions

A
  • Can release blood in time of need-hemorrhage
  • Kuffer cells destroy intestinal bacteria which helps prevent infection
  • Prothombin/Fibrinogen-> clotting factors
51
Q

Vit. K

A

Vitamin K-essential for clotting factors; need bile salts for reabsorption of fats-vitamin K absorption depends on adequate bile production. Impaired vitamin K absorption diminishes production of clotting factors and can increase the risk of bleeding

52
Q

Liver and hematologic metabolism

A
  • Proteins: Plasma proteins-albumins and globulins are synthesized by the liver; AST/ALT/LDH are markers
  • Mineral/Vitamin: stores iron, copper, Vitamin B12
53
Q

Liver metabolism of carbs

A

-Carbs: liver contributes to stability of blood glucose by releasing glucose during hypoglycemia and taking up glucose in times of hyperglycemia (stores as glycogen)
If glycogen is all used up, liver can convert amino acids to glycerol for glucose.

54
Q

Liver detoxification

A

Detoxification: Alters exogenous and endogenous chemicals, foreign substances, and hormones to make them less toxic;

  • Metabolic detoxification diminishes intestinal or renal tubular reabsorption of potentially toxic substances and facilitates renal or intestinal excretion.
  • ETOH, barbituates, steroids, and hormones are detoxified preventing accumulation and adverse effects
  • Excessive ETOH intake-end product is toxic which can cause liver damage
55
Q

Gallbladder

A
  • Function is to store and concentrate bile between meals
  • Gallbladder holds about 90 ml of bile
  • Mucosa absorbs water and electrolytes, leaving bile salts, pigments, and cholesterol
56
Q

Exocrine pancreas

A
  • Composed of acini and networks of ducts that secrete enzymes and alkaline fluids to assist in digestion
  • Located behind the stomach; head by the duodenum and tail by the spleen
  • Secretions: Potassium, sodium, bicarbonate, magnesium, calcium, and chloride
57
Q

Exocrine pancrease enzymes

A
  • Trypsinogen, chymitrypsinogen, and procarboxypeptidase (elastase protect the pancreas from the digestive effects of its own enzymes)
  • Trypsin inhibitor:
  • Pancreatic (alpha)-amylase: active form digests carbohydrates
  • Pancreatic lipase: hydrolyzes triglycerides, cholesterol, and free fatty acids

Anatomy and Physiology-DNP (18 decks)

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