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Anatomy & Physiology > Chapter 23 > Flashcards

Chapter 23 Flashcards

1
Q

Peristalis

A

Adjacent segments of GI tract organs alternately contract and relax moving food distally.

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2
Q

Segmentation

A

Nonadjacent segments of alimentary tract organs alternately contract and relax, moving food forward then backward.
Food mixing and slow food propulsion occur.

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3
Q

Alimentary Canal

A

Gastrointestinal tract

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4
Q

What do GI mechanoreceptors and chemoreceptors respond to?

A

Respond to stretch, changes in osmolarity, pH, and presence of substrate and end products in digestion.

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5
Q

What do GI mechanoreceptors and chemoreceptors do in digestion?

A

Initiate reflexes, activate and inhibit digestive glands, stimulate smooth muscle to mix and move contents in lumen

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6
Q

What is peritonitis

A

Inflammation of the peritoneum via piercing wound, perforating ulcer, ruptured appendix, peritoneal coverings sticking together.

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7
Q

3 layers of Mucosa

A

Epithelium - simple columnar epithelium and mucous secreting cells. Secretes mucus: Protects organs from enzyme and eases food passage. May secrete enzymes and hormones (e.g., in stomach and small intestine)

Lamina Propria - Loose areolar connective tissue, Capillaries for nourishment, absorption 
Lymphoid follicles (part of MALT), Defend against microorganisms

Muscularis Mucosae - smooth muscle – local movements of mucosa

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8
Q

Submucosa

A

Areolar connective tissue surrounds mucosa

Blood and lymphatic vessels, lymphoid follicles, and submucosal nerve plexus

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9
Q

Muscularis Externa

A
  • Segmentation and peristalsis
  • Inner circular, outer longitudinal layers
  • Circular layer thickens sphincters
  • Myenteric nerve plexus between layers
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10
Q

Serosa

A

Visceral peritoneum
• Areolar connective tissue covered with mesothelium in most organs
• Replaced by adventitia in esophagus

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11
Q

Hard palate

A

palatine bones and maxillae

Corrugated to create friction with tongue

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12
Q

Soft palate

A

Mostly of skeletal muscle
Closes nasopharynx during swallowing
Uvula projects downward from free edge

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13
Q

Tongue

A

Skeletal muscle
Repositioning,mixing food during chewing
Formation of bolus
Initiation of swallowing, speech, and taste
Lingual lipase is secreted by serous cells
Fat-digesting enzyme functional in stomach

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14
Q

Functions of Saliva

A

Cleanses mouth
Dissolves food
Moistens food
Enzyme breakdown starch

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15
Q

Two types of secretory cells in the salivary gland

A

Serous cells- Watery, enzymes, ions, bit of mucin

Mucous cells- Mucus

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16
Q

Composition of Saliva

A

97–99.5% water, slightly acidic
Electrolytes: Na+, K+, Cl–, PO4 2–, HCO3–
Salivary amylase and lingual lipase
Mucin
Metabolic wastes: urea and uric acid
Lysozyme, IgA, defensins, and a cyanide compound protect against microorganisms

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17
Q

Dental Caries

A

Cavities - - demineralization of enamel and dentin from bacterial action

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18
Q

Teeth

A

Tear and grind food for digestion
- 20 deciduous teeth erupt (6–24months)
Roots resorbed, teeth fall out (6-12years)
Permanent dentitions formed by age21
- Third molars at 17–25, or may not erupt

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19
Q

Gingivitis

A

Plaque calcifies to form calculus (tartar) which disrupts seal between gingivae and teeth
Anaerobic bacteria infect gums

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20
Q

Periodontitis

A 
(from neglected gingivitis)
Immune cells attack intruders, tissues
Destroy periodontal ligament
Activate osteoclasts  dissolve bone
Possible tooth loss; may promote atherosclerosis and clot formation in coronary and cerebral arteries
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21
Q

Esophagus

A

Flat muscular tube from laryngopharynx to stomach
Pierces diaphragm at esophageal hiatus
Joins stomach at cardial orifice
Gastroesophageal (cardiac) sphincter

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22
Q

Heartburn

A

Stomach acid regurgitates into esophagus

Excess food/drink, extreme obesity, pregnancy, hiatal hernia: Part of stomach above diaphragm

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23
Q

Cellular Layers of Esophagus

A

Mucosa
Submucosa
Muscularis Externa
Adventitia (fibrous connective tissue)

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24
Q

Deglutition

A

Swallowing

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25
Q

Step 1: Buccal Phase of Eating

A 
During the buccal phase, the upper 
esophageal sphincter is contracted. 
The tongue presses against the hard 
palate, forcing the food bolus into the 
oropharynx.
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26
Q

Step 2: pharyngeal-esophageal phase of eating

A

The pharyngeal-esophageal phase
begins as the uvula and larynx rise to prevent
food from entering respiratory passageways.
The tongue blocks off the mouth. The upper
esophageal sphincter relaxes, allowing food
to enter the esophagus.

27
Q

Step 3: of Eating

A 
The constrictor muscles of the 
pharynx contract, forcing food into 
the esophagus inferiorly. The upper 
esophageal sphincter contracts 
(closes) after food enters.
28
Q

Step 4: of eating

A

Peristalsis moves food through the esophagus to the stomach.

29
Q

Step 5: of eating

A

The gastroesophageal sphincter surrounding the cardial oriface opens, and food enters the stomach.

30
Q

Mesentaries

A

Tether stomach

31
Q

Parietal Cells

A

Secrete: Hydrochloric acid (HCl) pH 1.5–3.5 denatures protein, activates pepsin, breaks down plant cells, kills bacteria
Intrinsic factor: Required for absorption of vitamin B12 in small intestine

32
Q

Chief cell

A

secretions:
Pepsinogen - inactive enzyme
Activated to pepsin by HCl and by pepsin itself (positive feedback)
Lipases - Digest ~15% of lipids

33
Q

Enteroendocrine cell

A

secretions:
Chemical messengers into lamina propria that act as paracrines
Serotonin and histamine
Hormones: Somatostatin and gastrin

34
Q

Mechanisms to Protect Stomach from itself

A 
Harsh digestive conditions in stomach
Has mucosal barrier to protect
Thick layer of bicarbonate-rich mucus 
Tight junctions between epithelial cells
Damaged epithelial cells quickly replaced by division of stem cells
35
Q

Digestive Processes in the Stomach

A

Physical digestion
Denaturation of proteins by HCl
Enzymatic digestion of proteins by pepsin (milk protein by rennin, infants)
Lingual lipase digests some triglycerides Delivers chyme to small intestine
Lipid-soluble alcohol and aspirin absorbed Only stomach function essential to life:
- Secretes intrinsic factor for vit. B12 absorption mature red blood cells
- Lack of intrinsic factor: pernicious anemia, treated with B12 injections

36
Q

3 phases of Gastric Secretion

A

Cephalic (reflex) phase – conditioned reflex triggered by aroma, taste, sight.

Gastric phase – lasts 3–4 hours
Stimulated by distension, peptides, low acidity, gastrin (major stimulus)
Enteroendocrine G cells stimulated by caffeine, peptides, rising pH gastrin

Intestinal Phase:
Stimulatory component: Partially digested food enters small intestine brief intestinal gastrin release
Inhibitory effects: Chyme with H+, fats, peptides, irritating substances

Enterogastrones released
Secretin, cholecystokinin (CCK), vasoactive intestinal peptide (VIP)

37
Q

Stimuli of Gastric Phase

A

Gastrin enzyme and HCl release
Low pH inhibits gastrin secretion (as between meals)
Buffering action of ingested proteins – rising pH – gastrin secretion
Three chemicals - ACh, histamine, and gastrin - stimulate parietal cells

38
Q

Structural Modifications of Small Intestine

A

Circular folds: Force chyme to slowly spiral through lumen more nutrient absorption

Villi: Extensions of mucosa with capillary bed and lacteal for absorption

Microvilli: (brush border) – contain enzymes for carb. and protein digestion

39
Q

Cells of Intestinal Crypts

A

Intestinal crypt epithelium renewed every 2-4 days, containn secretory cells:
Enteroendocrine cells: enterogastrones
Intraepithelial lymphocytes: Release cytokines that kill infected cells
Paneth cells: antimicrobial agents (defensins and lysozyme)

40
Q

Peyer’s patches

A

protect especially distal part of small intestines against bacteria

41
Q

hepatocytes

A 
Liver Cells
increased rough & smooth ER, Golgi, peroxisomes, mitochondria
Process bloodborne nutrients
Store fat-soluble vitamins
Perform detoxification 
Produce ~900 ml bile per day
42
Q

Hepatitis

A

Usually viral infection, drug toxicity, wild mushroom poisoning
Hep C - IV Drugs, Sex, etc.
Hep A - Pathogen, Ingested, replicates in liver CDC

43
Q

Cirrhosis

A

Progressive inflammation from chronic hepatitis or alcoholism
Liver fatty, fibrous – portal hypertension

44
Q

Bile

A

Secreted by the liver and stored in the Gallbladder. Yellow-green, alkaline solution
Bile salts - cholesterol derivatives that function in fat emulsification and absorption
Bilirubin - pigment formed from heme
Cholesterol, neutral fats, phospholipids, and electrolytes

45
Q

Gallstones

A

High cholesterol; too few bile salts
Obstruct flow of bile from gallbladder
May cause obstructive jaundice
Treated with drugs, ultrasound (lithotripsy), laser vaporization, surgery

46
Q

Pancreas

A

Endocrine function: Pancreatic islets secrete insulin and glucagon
Exocrine function: Acini (clusters of secretory cells) secrete pancreatic juicev

47
Q

Pancreatic Juice

A

1200 – 1500 ml/day
Alkaline solution (pH 8) neutralizes chyme
Electrolytes (primarily HCO3–)
Enzymes: Amylase, lipases, nucleases Proteases secreted in inactive form

48
Q

Appendix

A

Part of MALT of immune system
Bacterial storehouse recolonizes gut when necessary
Appenticitis: Blocked or twisted  enteric bacteria accumulate and multiply

49
Q

Large Intestine

A

Thicker mucosa of simple columnar epith.

  • No circular folds, villi, digestive secretions
  • Abundant deep crypts with goblet cells
50
Q

Bacterial Flora: Colonize colon

A

Synthesize B complex vitamins, vit. K
Metabolize host-derived molecules (mucin, heparin, hyaluronic acid)
Ferment indigestible carbohydrates
Release acids and gases (~500 ml/day)

51
Q

Processes of Large Intestine

A

Residue remains in large intest.12–24 hrs.
No food breakdown except by bacteria
Vitamins (made by bacterial flora), water, and electrolytes (Na+ and Cl–) reclaimed
Propulsion of feces to anus; defecation

52
Q

Haustral contractions

A

Most contractions Large Intestines
Slow segmenting movements
Haustra sequentially contract in response to distension

53
Q

Gastrocolic reflex

A

Initiated by presence of food in stomach

Activates three to four slow powerful peristaltic waves per day in colon (mass movements)

54
Q

Defecation

A

Assisted by Valsalva’s maneuver
Closing of glottis, contraction of diaphragm and abdominal wall muscles increased intra-abdominal pressure
Levator ani muscle contracts  anal canal lifted superiorly  feces leave

55
Q

Diverticulitis

A

Inflamed diverticula; may rupture and leak into peritoneal cavity.

56
Q

Irritable bowel syndrome

A

Recurring abdominal pain, stool changes, bloating, flatulence, nausea
Stress common precipitating factor

57
Q

Digestion of Carbohydrates

A

Monosaccharides absorbed as ingested
Glucose, fructose, galactose
Digestive enzymes
Salivary amylase, pancreatic amylase, dextrinase, glucoamylase, lactase, maltase, and sucrase
Break down disaccharides sucrose, lactose, maltose; polysaccharides glycogen and starch

58
Q

Absorption of Carbohydrates

A

Glucose and galactose
Secondary active transport (cotransport) with Na+ epithelial cells
Move out of epithelial cells by facilitated diffusion capillary beds in villi
Fructose
Facilitated diffusion to enter and exit cells

59
Q

Digestion and absorption of Proteins

A

Digestion begins in the stomach with HCl denaturing the proteins and pepsin breaking down the proteins. Pancreatic proteases (trypsin, chymotrypsin, and carboxypeptidase), and by brush border
enzymes (carboxypeptidase,
aminopeptidase, and dipeptidase)
of mucosal cells also break down proteins even further. The amino acids are then
absorbed by active transport into the apical membrane of microvilli, and move to the basal side. The amino acids leave the villi via facilitated diffusion and enter the capillary via intercellular clefts.

60
Q

Emulsification, digestion, and absorption of fats.

A

Bile salts in the duodenum emulsify large fat globules (physically break them up into smaller fat droplets). Digestion of fat by the pancreatic enzyme lipase yields free fatty acids and monoglycerides. These then associate with bile salts to form micelles which “ferry” them to the intestinal mucosa. Fatty acids and monoglycerides leave micelles and diffuse into epithelial cells. There they are recombined and packaged with other fatty substances and proteins to form chylomicrons. Chylomicrons are extruded from the epithelial cells by exocytosis. The chylomicrons enter lacteals and are carried away from the intestine in
lymph.

61
Q

Absorption of Vitamins

A

In small intestine
Fat-soluble vitamins (A, D, E, and K)
Water-soluble vitamins (C and B vit.)
Vitamin B12, binds with intrinsic factor

In large intestine
Vitamin K and B vitamins from bacterial metabolism are absorbed

62
Q

Absorption of Electrolytes

A

Most ions along length of small intestine
Iron and calcium in duodenum
Na+ coupled with active absorption of glucose and amino acids
Cl– transported actively
K+ diffuses in response to osmotic gradients; lost if poor water absorption

63
Q

Absorption of Water

A

9L water, most from GI tract secretions, enter small intestine
95% absorbed in the small intestine Most of rest absorbed in large intestine

Water uptake coupled with solute uptake

64
Q

Celiac Disease

A

Immune reaction to gluten
Gluten causes immune cell damage to intestinal villi and brush border
Treated by eliminating gluten from diet

Anatomy & Physiology (26 decks)

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