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A&P Winter > 24. Digestive System > Flashcards

24. Digestive System Flashcards

1
Q

Are 2 anatomical subdivisions of the digestive system

A 
Gastrointestinal Tract (GIT)
includes the mouth, pharynx, esophagus, stomach, small intestine, large intestine

Accessory Digestive Organs
includes the teeth, tongue, salivary glands, liver, gall bladder, pancreas

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2
Q

digestive system Involves 6 essential functions:

A 
Ingestion
Secretion
Mixing and propulsion
Digestion – mechanical/chemical
Absorption
Defecation
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3
Q

Histology of 4 layers

A
  1. Mucosa (lines the lumen)
    • epithelium + areolar CT + thin layer of smooth muscle
  2. Submucosa
    • areolar CT
    • containing blood vessels, lymph vessels, nerves and glands
  3. Muscularis
    • two layers of smooth muscle – inner circular fibers and outer longitudinal fibers
  4. Serosa (outermost)
    • visceral peritoneum – areolar CT + simple squamous cells
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4
Q 
Define 
• Parietal peritoneum:
• Visceral peritoneum: 
• mesentary:
• greater omentum: 
• lesser omentum: 
• falciform ligament:
• mesocolon:
A
  • Parietal peritoneum: lines the abdominopelvic cavity
  • Visceral peritoneum: covers some organs
  • mesentary: suspends small intestine from posterior body wall
  • greater omentum: extends from greater curvature of stomach and drapes over intestines
  • lesser omentum: extends from lesser curvature of stomach to the liver
  • falciform ligament: attaches liver to anterior body wall and diaphragm
  • mesocolon: suspends large intestine from posterior body wall
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5
Q

Mouth

  • formed by
  • epithilium type
A
  • Formed by the lips, cheeks, hard and soft palates and tongue
  • nonkeratinized stratified squamous epithelium
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6
Q

Salivary glands

A

• produce and secrete saliva into mouth – parotid, sublingual and submandibular glands
• SALIVA - dissolves some ingested material for taste identification
> contains mucus to lubricate and form bolus
> contains salivary amylase that starts breakdown of starch → sugar
> contains lysozyme (antibacterial)

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7
Q

Fancy word for swallowing & what happens during it

A

deglutition

1) Tongue pushes food against hard palate
2) Bolus is forced into oropharynx
3) Receptors are stimulated that initiate swallowing reflex in medulla and pons
4) Soft palate and uvula rise and close off nasopharynx
5) Larynx elevates and epiglottis covers glottis and food/liquid passes through upper esophageal sphincter
6) Peristaltic contractions propel bolus down
7) Lower esophageal sphincter opens

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8
Q

Esophagus

-how does food pass?

A

• Muscular tube lined with nonkeratinized stratified squamous epithelium (25-30 cm long)
• Alternating waves of contraction and relaxation of the muscularis propel bolus to stomach (peristalsis)
> Above bolus: circular muscle fibers contract constrict
> Below bolus: longitudinal fibers contract to shoten/expand

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9
Q

4 regions of stomach

A

cardia, fundus, body and pylorus

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10
Q

Stomach overview

A

• food holding area
> empty: volume is 50ml
> capacity: 1.5-2.5 L
> very distended: 4L
• Mucosa: simple columnar epithelium, when emply forms folds (rugae)
• Muscularis has 3 layers (added inner oblique) allows the stomach to compress, knead and twist

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11
Q

Cell Types in Stomach

A

1) mucus neck cell – produce mucus
2) parietal cells – produce HCl & intrinsic factor for vitamin B12 absorption
3) chief cells – produce pepsinogen
4) enteroendocrine cells – G cells secrete gastrin

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12
Q

Stomach Function

A
  • Serves as a storage and mixing chamber (mechanical digestion)
  • PROTEIN DIGESTION BEGINS IN THE STOMACH (pepsin activated by HCL)
  • Absorb some water, ions, alcohol, drugs (aspirin)
  • Periodically about 3 ml of chyme is forced through pyloric sphincter into duodenum with a mixing wave
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13
Q

Small intestine:

  • epithilim
  • 3 things to increase absorption
A
  • a simple columnar epithelium
  • villi in mucosa
  • microvilli, extensions of epithelial cells – form a “brush border”
  • plicae circulares, permanent folds of the mucosa and submucosa
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14
Q

Small intestine Mucosa cell types - 5

A

1) Absorptive Cells – absorb and digest nutrients
2) Goblet Cells – produce mucus
3) Secretory Cells – secrete alkaline intestinal juice (water & mucus; NO enzymes)
4) Paneth Cells – secrete lysozyme
5) Enteroendocrine Cells – S cells secrete the hormone secretin; CCK cells secrete the hormone cholecystokinin

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15
Q

Functions of the Small Intestine

A
  • FAT DIGESTION BEGINS HERE!!
  • mechanical digestion occurs
  • segmentation mixes chyme with intestinal juice, pancreatic juice and bile
  • completes carbohydrate, protein and lipid digestion
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16
Q

Pancrease endocrine gland sectetion pathway

A

secrete pancreatic juice into small ducts → pancreatic duct → hepatopancreatic ampulla → duodenum

17
Q

What’s pancreatic Juice composed of?

A

mostly water
some salts
sodium bicarbonate
digestive enzymes

18
Q

Regulation of pancreatic secretion:

A

• PNS stimulates pancreatic secretion when stomach is active
• amino acids/fatty acids entering duodenum stimulate small intestine enteroendocrine cells to produce hormones CCK and secretin
> cholecystokinin secreted in response to fatty-protein chyme
> secretin secreted in response to acidic chyme

BOTH CCK & secretin:
↓ gastric gland activity
↓ stomach motility
↓ stomach emptying
Want TIME to process food in small intestine before the stomach empties further!
19
Q

Liver Function
• what does it store
• what does it synthesis
• produce

A
  • Stores: glycogen + triglyceride + vitamins A, B12, D, E, K + iron & copper
  • Synthesis: protein + lipoprotein (LDL, HDL) + glucose + urea
  • detoxification of drugs and other toxins
  • produces bile
20
Q

Bile

  • what does it comtain
  • how does it leave the liver?
A 
Contains
• NO enzymes
• mostly water + several ions
• bile pigments (main pigment is bilirubin)
• cholesterol
• bile salts (emulsify lipids)

Bile is continuously produced, draining into bile ducts, leaving the liver in the common hepatic duct

21
Q

emulsification:

A

breakdown of large lipids into a suspension of small lipid globules

22
Q

Gall Bladder

-pathway of release

A

Function: stores and concentrates bile

releases bile when needed into cystic duct → common bile duct → hepato-pancreatic ampulla → duodenum

23
Q

Regulation of bile secretion:

A
  • PNS stimulates liver to increase bile production after a meal
  • CCK stimulates gallbladder to contract and bile enters duodenum
  • secretin stimulates liver to produce bile rich in bicarbonate ions
24
Q

Large Intestine Overview

A
  • Mucosa: simple columnar epithelium + form long, straight intestinal glands (crypts)
  • taenia coli = thickened bands in muscularis
  • haustra = pouches in intestinal wall
25
Q

Function of Large Intestine

A
  • Mechanical digestion and propulsion move chyme towards rectum
  • Chemical Digestion: synthesize some B and K vitamins, ferment carbohydrates, break down protein, decompose bilirubin
  • Absorption: water, ions (Na+, Cl-), vitamins (B & K)
26
Q

Diarrhea

A
  • increase in frequency of bowel movements or looseness of stool
  • chyme passed too quickly through intestine
  • water not reabsorbed
  • may be caused by lactose intolerance, stress, microbes that irritate GIT mucosa
27
Q

Constipation

A
  • infrequent or difficult defecation
  • feces in colon too long due to decreased intestinal motility
  • too much water reabsorbed
  • remedy: increase water intake and exercise, decrease emotional stress
28
Q

Defecation reflex

A
  • PNS stimulates contraction of longitudinal rectal muscles
  • rectum shortens, increases pressure
  • internal anal sphincter relaxes and feces enter anal canal (smooth muscle = involuntary)
  • conscious effort: relax external anal sphincter (skeletal muscle = voluntary)
29
Q

3 Phases of Digestion

A

1) Cephalic (“Stomach Getting Ready”) Phase
2) Gastric (“Stomach Working”) Phase
3) Intestinal (“Stomach Emptying”) Phase

30
Q

Digestion - Cephalic (“Stomach Getting Ready”) Phase

A
  • smell, sight, thought of food, activate neural centers in cerebral cortex, hypothalamus and medulla
  • increase saliva secretion and gastric gland activity
31
Q

Digestion - Gastric (“Stomach Working”) Phase

A
  • arrival of food in stomach stimulates chemoreceptors (monitor pH) and stretch receptors
  • waves of peristalsis occur and stimulate gastric gland activity
  • distension, proteins and high pH stimulate G cells → gastrin release
  • increase gastric gland activity and gastric motility
32
Q

Digestion - Intestinal (“Stomach Emptying”) Phase

A
  • slow the exit of chyme into duodenum to allow time for continued digestion
  • distension of the duodenum inhibits gastric motility and emptying
  • presence of partially digested proteins and triglycerides stimulates release of CCK which inhibits gastric emptying
  • presence of acidic chyme stimulates release of secretin which inhibits gastric secretions

A&P Winter (10 decks)

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