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Biology Option D > Digestion > Flashcards

Digestion Flashcards

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1
Q

What are exocrine glands?

A
  • They produce and secrete substances via a duct into an epithelial surface either onto the surface of the body OR in the lumen of the digestive tract
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2
Q

What are digestive glands and give four examples.

A
  • They are exocrine glands that secrete substances into the lumen of the digestive tract
    1. Salivary glands - secrete saliva (with amylase)
    2. Gastric glands - secretes gastric juices which includes HCl and protease (enzyme for proteins)
    3. Pancreatic glands - secrete pancreatic juices (contains lipase, protease and amylase)
    4. Intestinal glands - secrete intestinal juices in the intestinal wall
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3
Q

Describe the structure of an exocrine gland cells.

A
  • They are a cluster of secretory cells which collectively form acini
  • The acini are surrounded by a basement membrane and are held together by tight junctions between secretory cells
  • Exocrine products are released by secretory vesicles into a duct which connect to an epithelial surface
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4
Q

What 3 mechanisms control the secretion of digestive juices? What exactly do they control?

A
  • Mechanical, nervous and hormonal mechanisms
  • They control the volume and specific content of secretion
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5
Q

How does the nervous mechanism control the secretion of digestive juices?

A
  • Sight and smell of food may trigger an immediate response
  • Gastric juice is secreted in the stomach and saliva in the mouth
  • Body prepares for the future intake of food
  • When food enters the stomach it causes swelling, detected by stretch receptors in stomach lining
  • Signals are sent to the brain, triggers release of digestive hormones for gastric stimulation
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6
Q

What 3 hormones are involved in the chemical control of digestion?

A
  • Gastrin, Secretin, Cholecystokinin (CCK)
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7
Q

How does Gastrin control the secretion of digestive juices?

A
  • Gastrin is produced by G cells in the stomach, duodenum and pancreas
  • Response to physical stimulation (smell) and chemical stimulation by protein
  • When Gastrin is secreted into the bloodstream, it stimulates release of gastric juices
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8
Q

What does gastric juice contain and what does it do?

A
  • Contains H2O, HCl, inorganic ions, enzymes, mucus, polypeptides and instrinsic factor
  • Instrinsic factor needed for absorbing vitamin B12
  • Gastric juices change pH of food content 6.7 to 2, acidic conditions enhance digestion
  • When enough gastric juice is present, production of gastrin stops
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9
Q

How does Secretin control the secretion of digestive juices?

A
  • Produced in response to presence of acid fluid
  • Presence of gastric acid converts prosecretin into secretin
  • Stimulate the pancreas and liver to release digestive juices to neutralize intestinal components
  • When pH is 8, production of pancreatic juice is stopped
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10
Q

How does CCK control the secretion of digestive juices?

A
  • Produced in small intestine when food is present in this organ
  • Controls release of pancreatic juice from pancreas and bile from the gall bladder
  • Acts as hunger suppressor
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11
Q

How does negative feedback control the secretion of digestive juices?

A
  • This mechanism causes the presence of acid in the lumen of the stomach to stimulate somatostatin secretion, slows acid secretion
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12
Q

How is stomach acid produced?

A
  • Produced by H+ and Cl- ions. These ions are produced by parietal cells of the stomach lining.
  • The H+ ions are released by protein carriers as K+ are taken in from the lumen of the stomach
  • This requires ATP
    Check book
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13
Q

What does stomach acid do?

A
  • Assists in the digestion of food
  • Activates stomach protease
  • Prevents pathogenic infections (destorys microorganisms in ingested food)
  • Normal pH 1.5-2.0, optimum pH for enzymes
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14
Q

What are pepsin and pepsinogen, how is pepsinogen converted?

A
  • Pepsinogen is an inactive form of pepsin
  • Pepsin is an emzyme that breaks polypeptides into smaller monomers
  • Pepsinogen is secreted by exocrine glands called gastric glands
  • When pepsinogen reacts with HCl, it becomes ‘active’ as 44 amino acids are removed and is now pepsin
  • Optimum pH is 2
  • This is a hydrolysis reaction (into smaller pieces)
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15
Q

How is the stomach wall protected from the acid?

A
  • The wall is lined by a layer of mucus, protects it from being damaged
  • The pancreas releases bicarbonate ions which neutralises the stomach to 7-8 pH
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16
Q

What are stomach ulcers? What causes them?

A
  • When excess gastric acid is produced in the stomach, this can damage the mucus layer which can lead to a gastric ulcer
  • The lining of the stomach is disrupted
  • Symptoms: stomach pain, heartburn, nausea)
  • Can also be caused by a bacterium H. pylori that produces toxins that cause gastric inflammation
17
Q

How are stomach ulcers from H. pylori treated?

A
  • Amoxicillin: antibiotic, inhibits synthesis of bacterial cell wall
  • Clarithromycin: antibiotic prevents bacteria from growing (no protein synthesis)
  • Proton Pump Inhibitor (PPI): inhibits acidification of stomach
18
Q

How do proton pump inhibitor drugs treat stomach ulcers?

A
  • It blocks the proton pump responsible for the secretion of H+ ions in the stomach
  • Less H+ in the lumen reduces amount of HCl produced, stomach is less acidic
  • This prevents gastric discomfort caused by high acidity
19
Q

What are the 6 adaptations of villi? Check chapter 6.1

A
  1. Increase surface area, microvilli
  2. Many mitochondria, energy for active transport
  3. Capillaries present, absorption of food into blood
  4. Lacteal for absorption into lymphatic system
  5. Pinocytotic vesicles, help uptake of fluids
  6. Tight junctions, ensure molecules don’t escape, maintain concentration gradient
20
Q

What does the large intestine absorb?

A
  • Absorbs water, minerals and vitamin K
21
Q

What is dietary fibre?

A
  • The non-digestible carbohydrates, especially cellulose, that increase faecal mass, stimulates peristaltic movements
22
Q

What happens to the substances that are not absorbed?

A
  • They are egested as faeces such as cellulose, lignin, bile pigments
  • Peristalsis of the walls of the large intestine push the faecal matter toward the rectum and eventually eliminate through the anus
23
Q

What happens with an inadequate fibre intake?

A
  • May lead to constipation (unsatisfactory defecation, infrequent bowel movement, difficult stool passage)
24
Q

What are the benefits of fibre intake?

A
  • Reduces frequency of constipation, lowers risk of colon cancer
  • Lowers blood cholesterol and regulates blood sugar levels
  • Aids in weight management (volume eating)
25
Q

What is cholera?

A
  • Disease caused by ingestion of food or water contaminated with bacterium V. cholerae
  • When the cholera toxin infects the intestine, triggers endocytosis of the toxin in the epithelial cells
  • Toxin is an active enzyme which activates ions and water to leave, diarrhea
26
Q

What are symptoms of cholera? What is a treatment?

A
  • Vomiting, muscle cramps, diarrhea, cause dehydration, low blood pressure, death, increased thirst, swelling of brain, decreased urine output
  • Treatment: antibiotics to kill bacteria, oral or intravenous rehydration

Biology Option D (6 decks)

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