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Digestive system Flashcards

1
Q

Digestive activities
6 essential activities

A
  1. Ingestion
  2. Propulsion
  3. Mechanical digestion
  4. Chemical digestion
    * Involves secretion
  5. Absorption
  6. Defecation
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2
Q

Alimentary Canal

A

Gastrointestinal or GI tract
* Mouth
* Pharynx
* Esophagus
* Stomach
* Small intestine (SI)
⬧ Duodenum
⬧ Jejunum
⬧ Ileum
* large intestine (LI)

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3
Q

Accessory Glands/organs

A

Teeth, tongue
Salivary Glands
Gallbladder
Liver
pancreas

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4
Q

digestive tract
- same general structure from esophagus to anus
- 4 major tissue layers

A

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 and pH changes
* Digestive substrates and end products (ie. Food)

Both Initiate reflexes that
* Activate or inhibit digestive glands
* Stimulate smooth muscle to mix and move lumen
contents

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6
Q

Four digestive process

A

Motility, secretion, absorption, digestion

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7
Q

-Motility

-Two types

A

-Muscular contractions that mix and move forward the contents of the digestive tract

1) Peristalsis
* Propulsive

2) Segmentation
* Mixing movements
⬧ promotes digestion of foods
⬧ Facilitates absorption

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8
Q

Secretion

Hormones

Digestive Enzymes

Mucous

A
  • CCK, gastrin, secretin
  • Affect motility and secretions
  • mouth, Stomach, Small intestine
  • Mouth, stomach, S. Intestine
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9
Q

Absorption

A

-Villi and microvilli
Increase surface area for absorption

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10
Q

Digestion - Mechanical digestion by chewing

Digestion of carbs
- types
- enzymes

A
  • Chemical break-down by enzymes of
    Carbohydrates, Proteins, Fats

Starch – usually 2/3 of carbohydrates
Dissaccarides (eg. Sucrose, Lactose)
Monosaccarides (eg. Glucose)
Complex carbohydrates (i.e. fibre)

Amylase
* From salivary glands (acts in Mouth)
* From pancreas (acts in SI)

SI enzymes (from SI wall ; acts in SI)
* Lactase
* Maltase

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11
Q

Starch digestion process

A
  • Starch to Maltose using Amylase (Mouth, SI)
  • Maltose to glucose using Maltase (SI), absorbed directly into blood
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12
Q

Complex carb digestion

  • what do humans lack

Fibre moves…

A
  • Humans lack enzyme to digest complex carbohydrates (eg. oligosaccarides)
    α - galactosidase

-Fibre moves to LI for E.Coli Digestion
Fermentation
* Gas production

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13
Q

Protein digestion
- how much per day needed

  • enzymes
  • many enzymes needed…
A

-50-60 g per day needed
Essential Amino acids

Pepsin (Stomach)
From Pancreas (acts in SI)
* Trypsin / chymotrypsin
* Carboxypepsidase
* Aminopeptidase
Dipeptidases (SI)

  • Many enzymes needed to break the bonds between the different amino acids
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14
Q

Protein digestion progress

A
  • Protein to polypeptides using Pepsin
    (Stomach), Trypsin, Chymotrypsin (SI)
  • Polypeptides to dipeptides using Carboxypepsidase, Aminopepsidase
    (SI)
  • Dipeptides to amino acids using Dipeptidase, Brush border enzymes
    (SI) to be absorbed directly into blood
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15
Q

Fat digestion
- Non polar and needs emulsifier
- enzymes

Fat digestion process

A

Bile (emulsifier)
* Made in liver, stored in gall bladder
* Increases surface area for lipase
- lipase (from pancrease, acts in SI)

  • fat to smaller fat globules using bile (SI)
  • smaller fat globules to glycerol + fatty acids using lipase (SI). Into lymph then blood
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16
Q

Fat absorption

-Lipase acts on emulsified droplets

A
  • Get monoglyceride and fatty acids
  • Can enter absorptive cells or form micelles
  • Within cell – forms chylomicron
  • Absorbed into lymph
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17
Q

Nucleic acids and vitamins

Nucleic Acids

Vitamins

A

-Digested by Nucleases
* From pancreas, act in small intestine
* SI enzymes

-Absorbed whole by carriers

18
Q

Mouth

  • Chewing
  • Secretion of

Swallowing Reflex

A

↑ surface area
↓ choking

Mucous
* Lubrication
Salivary Amylase
* Starch digestion

Triggered by food in pharynx
Contractions coordinated by Medulla

19
Q

Esophagus

  • Long muscular tube separated by..
    • Heartburn (Acid reflux) cause by
A

Separated from stomach by
Gastroesophageal (cardiac) sphincter or valve

  • Faulty valve, stomach content may backflow into stomach
20
Q

Stomach

Sections

Spincters

Rugae

4 functions

storage

A

Fundus
Body
Antrum

Gastroesophageal
Pyloric

Deep folds
Allow for expansion

Storage, Mixing, Secretion, Absorption

Mostly in body of stomach
Can expand 20 x
* 50 mL → 1 L

21
Q

stomach secretion
- acid
- pepsin
- mucous
- intrinsic factors
- pepsinogen (chief cells)
- Converted to pepsin by

A

Acid
* Activates pepsin
* Parietal cells

Pepsin
* Protein digestion
* Chief cells

Mucous
* Protects wall from acid

Intrinsic factor
* Helps in absorption of B12 in SI

Pepsinogen (chief cells)
Inactive form

Converted to Pepsin by
HCl (parietal cells)

  • Stomach pH can drop to 2-3
22
Q

Formation of acid

  • Hydrochloric Acid
  • stomach acid
  • mixing and emptying
A
  • Activates pepsin
    Breaks down connective
    tissue and muscle
    Kills pathogens

Stomach wall protects itself with mucous, tight junctions, and high cell replacement

Formation of chyme (Glop / slop)
Some moves into SI – rest is stored

23
Q

Stomach

  • absorption

hormones
- gastrin
- stimulated by

A

-Aspirin
- Alcohol

Gastrin
↑ HCl secretion
↑ pepsinogen
↑ motility

Stimulated by
Proteins, Distension, smell

24
Q

diseases of the stomach

-peptic ( gastric) ulcer
- symtoms
- treatment

A

Hole caused by inflammation and necrosis
* Caused in part by pepsin
* Helicobacter pylori
* stomach and duodenum

  • Pain
  • Bleeding (hematemesis or melena)

Treatment:
* Reduction of contributory factors
* Antacids
* Surgery in severe cases

25
Small intestine - Length - parts - site of
21 feet long -1 cm diameter - Duodenum, jejunum, and ileum Site of digestion, secretion, and absorption -Alternate between segmentation and peristalsis
26
SI digestion - Secretion from - gall bladder - pancrease
Secretions from pancreas and gall bladder dump into the duodenum Gall bladder * Bile Pancreas enzymes - acts on duodenum * Amylase * Trypsin, chymotrypsin * Pepsidases * Lipase * Nucleases * Bicarbonate (neutralizer)
27
Cholecystokinin (CCK) - small bolus of feed enters the SI.. - where released and why
-Triggers release of the hormone, CCK - CCK acts on pancreas and gall bladder to increase release of enzymes and bile CCK is released if duodenum is distended or if fat content in SI increases
28
Secretion (hormone) - released if SI is acidic, effects of secretin Motilin
- Allows time for digestion and absorption in SI Effects of secretin, causes pancreas to release bicarbonate * Neutralizes acid ↑ bile formation in liver Inhibits gastric motility - promotes motility of SI
29
SI absorption - amino acids and sugars - fatty acids via... Carbs Fats, proteins Fat-soluble vitamins Water-soluble vitamins Water reabsorption by osmosis
Amino acids, sugars - Into villi capillaries -Fatty acids Into lacteals of lymph vessels. Then into blood -Via Carriers Quickly absorbed First ½ of jejunum 2-3 hours to empty stomach Slower to digest 8-10 hours to empty stomach - With micelles - By carriers - Follows solutes (95%)
30
Electrolyte and water absorption - along length of SI - Iron and calcium..
- Iron and calcium are absorbed in duodenum Na+ is coupled with absorption of glucose and amino acids Ca2+ absorption is regulated by vitamin D and parathyroid hormone (PTH)
31
Diseases of the small intestine Regional enteritis - what it is - symptoms - supportive treatment
- Crohn’s disease inflammatory bowel disease (IBD) * Often SI Exacerbation / remission Symptoms: * Anorexia * Flatulence * pain * Diarrhea and constipation Supportive treatment: * Low-residue diet * Medications * surgery
32
Large intestine - parts - contractions - reabsorption - e. coli
leocecal valve Cecum and appendix Ascending colon Transverse colon Descending colon Rectum Haustral contractions - Slow movements Na+ reabsorption Water reabsorption E. Coli digestion of fibre -incomplete
33
Defecation reflex -Distention of rectum -Can over-ride with higher brain centres daily secretions
Parasympathetic response -Relaxes sphincters -Contracts rectal walls Food Drink - 2 L/day Saliva - 1.5 L/day Stomach - 2 L/day Bile - 0.5 L/day Pancreas -1.5 L/day Small Intestine – 1.5 L /day Total – 9 L /day
34
Daily absorption - small and large intestine Diseases of the colon - appendicitis
Small intestine 8.5 L / day Large Intestine 400 mL/day Remaining Feces ~100 mL /day Inflammation of appendix Symptoms: * Abdominal pain ⬧ shifts to right lower quadrant (RLQ) * Nausea and vomiting * Fever * Leukocytosis
35
Diseases of the rectum - hemorrhoids -causes - prevention - treament
Varicose veins in rectum * Internal or external Causes: * Pressure in anal area * Constipation * Prolonged standing * Pregnancy and childbirth Prevention: * Good bowel habits – fluids, fibre * Exercise * Avoid laxatives Treatment: * Medications * Warm sitz baths * Manual reduction * Cryosurgery * hemorrhoidectomy
36
Pancreas - function - different cells
-Exocrine and Endocrine Function Duct cells -Secrete bicarbonate Acinar cells -Secrete enzymes Endocrine cells -Secrete insulin / glucagon
37
- Liver - receives blood - hepatocytes
Largest organ Receives blood via Hepatic artery Hepatic portal vein * From gut * Rich in nutrients Liver cells -Arranged in sinusoids
38
Liver function - 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, vitamins -Makes clotting factors -Activates vitamin D -Removes bacteria and worn-out red blood cells -Excretes cholesterol and bilirubin
39
Gall bladder Formation of bile - how formed - whats in it
Stores and concentrates bile Contracts with CCK ~ 900 mL per day Cholesterol based Stored in Gall bladder between meals Bilirubin (porphyrin rings form Hb) * gives bile a yellow color Cholesterol Lecithin Bile salts * important in fat digestion * derived from cholesterol - recycled within gut water
40
Gall bladder diseases - gallstones - 5 f
consist of cholesterol, bilirubin, and calcium Can block ducts * If small – gravel Five Fs for risk: * Female * Fair complexion * Fat * Fertile * Forty or older

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