Digetsive System Physiology Flashcards

1
Q

Alimentary canal

A
GI tract 
Mouth 
Pharynx 
Esophagus 
Stomach 
Small intestine (duodenum, jejunum, ileum)
Large intestine
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2
Q

Accessory glands

A
Teeth 
Tongue 
Salivary glands 
Gallbladder 
Liver 
Pancreas
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3
Q

Digestive activities

A
6 essential activities 
Ingestion 
Propulsion 
Mechanical digestion 
Chemical digestion (involves secretion)
Absorption 
Defecation
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4
Q

Digestive tract

A

Same general structure from esophagus to anus
4 major tissue layers
Mucosa = innermost layer, secretions, absorption
Submucosa = blood/ nerve supply
Muscularis externa = motility
Serosa = outer CT layer

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5
Q

GI tract sensory receptors

A

Mechanoreceptors = respond to stretch (as food moves through)
Chemoreceptors = respond to osmolarity, pH changes, and digestive substrates and end products (food)
Both initiate reflexes that activate or inhibit digestive glands and stimulate smooth muscle to mix and move lumen contents

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6
Q

Extrinsic/intrinsic controls

A

Extrinsic = from outside digestive tract
Intrinsic = within digestive tract
Both affect motility and secretion of enzymes and hormones

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7
Q

GI tract regulatory mechanisms

A

Intrinsic and extrinsic controls
Short reflexes = enteric nerve plexuses (gut brain) respond to stimuli in GI tract
Hormones = from stomach and small intestine, stimulate target cells in same or different organs
Long reflexes = respond to stimuli inside or outside GI tract (eg - smell or thoughts of food), autonomic control/central nervous system

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8
Q

Four digestive processes

A

Motility
Secretion
Absorption
Digestion

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9
Q

Motility

A

Muscular contractions that mix and move forward the contents of the digestive tract
2 types
Peristalsis = propulsive
Segmentation = mixing movements, promotes digestion of food, facilitates absorption

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10
Q

Secretion

A

Hormones = CCK, gastrin, secretin, affect motility and secretions
Digestive enzymes = mouth, stomach, small intestine
Mucous = mouth, stomach, small intestine

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11
Q

Absorption

A

Villi and microvilli = increases surface area for absorption

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12
Q

Digestion

A

Mechanical digestion by chewing

Chemical break-down by enzymes of carbohydrates, proteins, and fats

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13
Q

Digestion of carbohydrates

A

Starch = usually 2/3 of carbohydrates
Disaccharides = sucrose, lactose
Monosaccharides = glucose
Complex carbohydrates = fibre
Enzymes = Amylase from salivary glands that act in the mouth and pancreas that act in the small intestine
Small intestine enzymes = from the small intestine, act in the small intestine, lactase, maltase

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14
Q

Complex carbohydrates digestion

A

Humans lack enzymes to digest complex carbohydrates (eg - oligosaccharides, galactosidase)
Fibre moves to large intestine for E.Coli digestion (fermentation, gas production)

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15
Q

Protein digestion

A

50-60g per day needed
Essential amino acids
Enzymes = pepsin (stomach), trypsin/chymotrypsin, carboxypepsidase, aminopeptidase (from pancreas, acts in small intestine)
Dipeptidase (from small intestine)
Many enzymes needed to break the bonds between different amino acids

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16
Q

Fat digestion

A
Non-polar 
Need emulsifier (bile = made in liver, stored in gallbladder, increases surface area for lipase)
Enzymes = lipase (from pancreas, acts in small intestine)
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17
Q

Fat absorption

A

Lipase acts on emulsified droplets
Get monoglyceride and fatty acids
Can enter absorptive cells or form mice,small
Within cell - forms chylomicron (absorbed into lymph)

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18
Q

Nucleic acids and vitamins

A

Nucleic acids = digested by nuclease (from pancreas, acts in small intestine)
Vitamins = absorbed whole by carriers

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19
Q

Mouth

A

Chewing = increases surface area, decreases choking
Secretion of
Mucous = lubrication
Salivary amylase = starch digestion

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20
Q

Swallowing reflex

A

Triggered by food in pharynx

Contractions coordinated by medulla

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21
Q

Esophagus

A

Long muscular tube
Separated from stomach by gastroesophageal sphincter or valve
Heartburn or acid reflux = faulty valve

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22
Q

Hiatal hernia

A

Part of stomach moves into chest
Symptoms = heart burn (increased with age) or asymptomatic
Treat = avoid large food intake and spicy food, surgery may be required

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23
Q

Stomach

A
Sections = fundus, body, antrum 
Sphincters = gastroesophageal, pyloric 
Rugae = deep folds, allow for expansion
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24
Q

4 functions of the stomach

A

Storage
Mixing
Secretion
Absorption

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25
Q

Storage in stomach

A

Mostly in body of stomach
Can expand 20x
50ml-1L

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26
Q

Secretion in stomach

A
Acid = activates pepsin, parietal cells, breaks down connective tissue and muscle, kills pathogens 
Pepsin = protein digestion, chief cells 
Mucous = protects wall from acid (stomach wall also protected by tight junctions and high cell replacement)
Pepsinogen = inactive form, converted to pepsin by HCl, stomach pH can drop to 2-3
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27
Q

Intrinsic factor of stomach

A

Helps in absorption of B12 in small intestine

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28
Q

Mixing and emptying in stomach

A

Formation of chyme (glop/slop)

Some moves into small intestine, rest is stored

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29
Q

Absorption in stomach

A

Aspirin and alcohol

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30
Q

Gastric emptying and mixing as a result of Antral peristaltic contractions

A

Peristaltic contraction from fundus sweeps towards pyloric sphincter
Contraction becomes more vigorous as it reaches thick-muscled antrum
Antral peristaltic contraction propels chyme forward
Small portion of chyme is pushed through partially opened sphincter into duodenum (strong contraction = more chyme emptied)
When peristaltic contraction reaches pyloric sphincter the sphincter is closed
Chyme that was being propelled forward hits sphincter and is tossed back into the antrum (mixing is accomplished)

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31
Q

Stomach - hormones

A

Gastrin = increased HCl secretion, increased pepsinogen, increased motility
Stimulated by = proteins, distension, smell

32
Q

Gastritis

A

Inflammation of stomach
Irritating agents = aspirin, alcohol, coffee, tabcco
Helicobacter gastritis = bacterial cause
Symptoms = epigastric pain, bloating, nausea, blood in vomit

33
Q

Peptic (gastric) ulcer

A

Hole caused by inflammation and necrosis
Caused in part by pepsin
Helicobacter pylori
Stomach and duodenum
Symptoms = pain, bleeding (hematemesis or melena)
Treatment = reduction of contributory factors, antacids, surgery in severe cases

34
Q

Small intestine

A

21 feet long
1cm diameter
Duodenum
Jejunum
Ileum
Site of digestion, secretion, and absorption
Alternate between segmentation and peristalsis

35
Q

Small intestine digestion

A

Secretions from pancreas and gallbladder dump into duodenum
Gallbladder (bile)
Pancreas (amylase, trypsin/chymotrypsin, pepsidases, lipase, nucleases, bicarbonate (neutralizer))

36
Q

Pancreatic enzymes, substrates, and action

A

Act on duodenum
Trypsin/chymotrypsin/elastase = proteins, break peptide bonds in proteins to form peptide fragments
Carboxypeptidase = proteins, splits off terminal amino acid from carboxyl end of protein
Lipase = fats, splits off two fatty acids from triglycerides forming free fatty acids and monoglycerides
Amylase = polysaccharides, splits polysaccharides into glucose and maltose
Ribonuclease/deoxyribonuclease = nucleic acids, splits nucleic acids into free mononucleotides

37
Q

Cholecystokinin (CCK)

A

A small bolus of food enters the small intestine and triggers the release of the hormone CCK
CCK acts on pancreas and gallbladder to increase release of enzymes and bile
CCK is released if duodenum is distended or if fat content in the small intestine increases

38
Q

Gastric inhibition

A

Distinction of duodenum inhibits gastric emptying

Allows time for digestion and absorption in the small intestine

39
Q

Secretion (hormone)

A

Released if small intestine is acidic
Effects = causes pancreas to release bicarbonate (neutralizes acid), increased bile formation in liver, inhibits gastric motility

40
Q

Motilin

A

Promotes motility in small intestine

41
Q

Small intestine absorption

A

Amino acids/sugars = into villi capillaries
Fatty acids = into lacteals of lymph vessels then into blood
Via carriers
Carbohydrates = quickly absorbed, first 1/2 of jejunum, 2-3 hours to empty stomach
Fats/proteins = slower to digest, 8-10 hours to empty stomach
Fat-soluble vitamins = with micelles
Water-soluble vitamins = by carriers, water reabsorbed by osmosis (follows solute, 95%)

42
Q

Electrolyte and water absorption

A

Along length of small intestine
Iron and calcium are absorbed in duodenum
Na+ is coupled with absorption of glucose and amino acids
Ca++ absorption is regulated by vitamin D and parathyroid hormone (PTH)

43
Q

Malabsorption syndrome

A

Disease of small intestine
Small intestine can’t absorb nutrients (fats and minerals)
Diarrhea, foul feces
Causes = disease of intestinal wall, blocked exocrine ducts
Diet therapy = bleeding (decrease in vitamin K), malnutrition

44
Q

Regional enteritis

A

Disease of small intestine
Crohn’s disease
Inflammatory bowel disease (IBD)
Exacerbation/remission
Symptoms = anorexia, flatulence, pain, diarrhea/constipation
Supportive treatment = low-residue diet, medication, surgery

45
Q

Inguinal hernia

A

Outpouching of small intestine and peritoneum
More common in males
Strangulated hernia = parts of small intestine are caught and twisted, cuts off blood supply to organ
Treatment = surgical repair

46
Q

Large intestine

A
Ileocecal valve 
Cecum and appendix 
Ascending colony 
Transverse colon 
Descending colon
Rectum 
Haustral contractions (slow movement)
Na+/water reabsorption 
E. Coli digestion of fibre (incomplete)
47
Q

Defecation reflex

A

Distension of rectum
Parasympathetic response (relaxes sphincters, contracts rectal walls)
Can override with higher brain centres

48
Q

Daily secretions

A
Food drink = 2L/day 
Saliva = 1.5L/day 
Stomach = 2L/day 
Bile = 0.5L/day 
Pancreas = 1.5L/day 
Small intestine = 1.5L/day 
Total = 9L/day
49
Q

Daily absorption

A

Small intestine = 8.5L/day
Large intestine = 400ml/day
Remaining feces = 100ml/day

50
Q

Appendicitis

A

Disease of the colon
Inflammation of the appendix
Symptoms = abdominal pain (shifts to right lower quadrant), nausea and vomiting, fever, leukocytosis

51
Q

Intestinal obstruction

A
Disease of the colon 
Blockage in intestine or bowel
Tumours
Hernias 
Adhesions 
Volvulus (twisting)
Intussusception (folding) 
Paralytic obstruction 
Symptoms = abdominal pain, distension, nausea and vomiting 
Treatment = nasogastric sectioning, surgery
52
Q

Ulcerative colitis

A

Disease of the colon
Chronic inflammation of the colon
Symptoms = lower abdominal pain, blood in stools, anemia, diarrhea
Treatment = dietary limitations, stress reduction, mild sedatives, anti-inflammatories, surgery

53
Q

Irritable bowel syndrome

A

Disease of the colon
Aka spastic colon
Inflammation of the bowel with chronic lesions
Symptoms = abdominal pain, altered motility, diarrhea or constipation
Causes = spicy foods and seasonings, caffeine, alcohol, stress
Treatment = avoidance of causative factors

54
Q

Dysentery

A

Disease of the colon
Acute inflammation of the colon
Massive diarrhea with blood pus and mucous
Severe abdominal pain
Treatment dependant on cause (antibiotics if bacterial)

55
Q

Diverticulosis and diverticulitis

A

Diseases of the colon
Diverticulosis = condition of diverticula or little out pouches
Diverticulitis = outpouches fill with fecal material, become irritated and inflamed
Symptoms = lower abdominal pain, cramping
Treatment = antibiotics, dietary modification

56
Q

Colon polyps

A

Disease of the colon
Inward projections of mucosal lining
Suspicious polyps excited
Pre cancerous? Colo-rectal cancer

57
Q

Hemorrhoids

A

Disease of the rectum
Varicose veins in rectum (internal or external)
Causes = pressure in anal area, constipation, prolonged standing, pregnancy and childbirth
Prevention = good bowel habits (fibre and fluids), exercise, avoid laxatives
Treatment = medications, warm sitz baths, manual reduction, cryosurgery, hemorrhoidectomy

58
Q

Pancreas

A

Exocrine and endocrine functions
Duct cells = secrete bicarbonate
Acinar cells = secrete enzymes
Endocrine cells = secrete insulin and glucagon

59
Q

Pancreas diseases

A

Pancreatitis = inflammation of pancreas
Symptoms = pain radiating to back, nausea and vomiting, foul feces, necrosis, bleeding
Alcohol, women over 40

60
Q

Liver

A

Largest organ
Receives blood via hepatic artery and hepatic portal vein (from gut, rich in nutrients)
Hepatocytes = liver cells, arranged in sinusoids

61
Q

Liver functions

A

Not related to digestion
Metabolic processing of the major nutrients
Detoxifying or degrading body wastes and hormones, drugs, and other foreign compounds
Synthesizes plasma proteins
Stores glycogen, fats, iron, copper, and vitamins
Makes clotting factors
Activates vitamin D
Removes bacteria and worn-out red blood cells
Excretes cholesterol and bilirubin

62
Q

Formation of bile

A
~900ml/day 
Cholesterol based 
Stored in gallbladder between meals 
Bilirubin (porphyrin rings from Hb) gives bile yellow colour 
Cholesterol
Lecithin 
Bile salts (important in fat digestion, derived from cholesterol)
Water
63
Q

Bile salts

A

Recycled within gut

64
Q

Gallbladder

A

Stores and concentrates bile

Contracts with CCK

65
Q

Hepatitis

A

Liver disease
Symptoms = jaundice and liver enlargement, myalgia and abdominal pain, clay or light coloured stools, dark coloured urine, malaise, anorexia, fever, ascites
Treatment = rest, good nutrition, anti-virals, transplant
Prevention = good hygiene, vaccination, special care when handling needles and body fluids
Viral hepatitis most common, 5 types = A,B,C,D,E

66
Q

Hepatitis A

A
Aka infectious hepatitis 
Benign 
Incubates for 2-6 weeks 
Oral-fecal spread 
Contaminated food
67
Q

Hepatitis B

A

Aka serum hepatitis
Can lead to chronic hepatitis or cirrhosis
Spread by blood, urine, feces, saliva, and semen
Incubates 2-6 months

68
Q

Hepatitis C

A

Spread by blood or sexual contact
Persists for months or years
Can lead to cirrhosis (~20%)
May require transplant

69
Q

Hepatitis D

A

Delta virus
Needs hepatitis B to replicate
Spreads like B
Leads to chronic disease

70
Q

Hepatitis E

A

Uncommon in North America
Oral-fecal spread
Often water contamination

71
Q

Cirrhosis

A
Liver disease 
Chronic 
Irreversible 
Degenerative 
Alcohol 
Toxins
Disease
Loss of normal liver cells 
No organization 
Scar tissue 
Symptoms = nausea, weight loss, weakness, inflammation then degeneration (hobnailed (nodular)), ascites (high abdominal venous pressure, organs swell, bleeding)
Treatment = transplant
72
Q

Liver cancer

A

Primary and benign tumours are rare (metastasis)

Discovered late or end stage

73
Q

Gallstones

A

Gallbladder disease
Consists of cholesterol, bilirubin, and calcium
Can block ducts
If small = gravel
5 f’s for risk = female, fair complexion, fat, fertile, forty and over

74
Q

Cholelithiasis

A

Gallbladder disease
Gall stones in gallbladder or bile ducts
Symptoms = nausea and vomiting, right upper quadrant pain with fat intake

75
Q

Cholecystitis

A

Inflammation of gallbladder (eg-blockage)
Symptoms = right upper quadrant pain, nausea and vomiting after eating
Treatment = surgical excision