D2 Digestion
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Define alimentary canal.
D.2.U2 Exocrine glands secrete to the surface of the body or the lumen of the gut.
D2 Digestion
State to mechanisms by which secretion of gastric juices is controlled.
D.2.U1 Nervous and hormonal mechanisms control the secretion of digestive juices.
1. Food in the stomach causes the stretch activating stretch receptor proteins
2. Nerve Signal from stomach to brain ‘I’m Stretching”
3. Nerve Signal from your brain ‘You’re Stretching”
4. Endocrine glands made up of parietal cells in the stomach (and duodenum) secrete gastrin into the blood
5. Gastrin moves into the stomach and around the body and back to the stomach
6. When Gastrin is in the stomach, exocrine glands secrete gastric juice and increases motility
1. When the food leaves the stomach, it enters the duodenum (Small Intestine)
2. Secretin and CCK are secreted from the S. Intestine
3.1 When fats and proteins enter your small intestine, cholecystokinin triggers your gallbladder and pancreas to contract and deliver bile and enzymes
3.2 When acidic food enters the duodenum, Secretin triggers bicarbonate to be released from the pancreas
Secretin Inhibits Gastrin
Composition of Digestive Juices�Highlight names of enzymes
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GLAND | COMPOSITION of “JUICE” |
Salivary gland (mouth) | Water, salts, amylase, mucus |
Gastric glands (stomach) | Water, mucus, HCl, enzymes (i.e. pepsin) |
Pancreas | Water, bicarbonate (buffers acid from stomach), enzymes (i.e. amylase, lipase) |
D2 Digestion
State the composition of saliva, gastric juice and pancreatic juice.
D2 Digestion
Cholecystokinin (CCK) is a hormone produced in your small intestine. It plays a fundamental role in the digestive process.
When fats and proteins enter your small intestine, cholecystokinin triggers your gallbladder and pancreas to contract.
They deliver bile and enzymes to your duodenum to help break down the food for absorption.
D2 Digestion
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D.2.U3 The volume and content of gastric secretions are controlled by nervous and hormonal mechanisms.
So what do gastric juices do?
1. Activates Pepsin (enzyme)
2. Prevents Pathogenic Infection
3. Assists in the digestion of food
D2 Digestion
Outline three roles of acid in the stomach.
D.2.U4 Acid conditions in the stomach favour some hydrolysis reactions and help to control pathogens in ingested food.
Hydrochloric acid (HCl)
●Maintains a pH of 2 in the stomach
●Kills microorganisms
●Converts pepsinogen to pepsin
●Helps dissolve food
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Mucus
●Mucus protects the stomach lining from the acid and digestive enzymes in the stomach.
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Enzymes
●Pepsinogen, which is converted to pepsin, which digests proteins into smaller polypeptides.
●Pepsinogen production is stimulated by the presence of gastrin in the blood.
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Acid-
secreting cell
Enzyme-
secreting cell
Pepsinogen
Pepsin
HCl
Stomach lumen
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D.2.U4 Acid conditions in the stomach favour some hydrolysis reactions and help to control pathogens in ingested food.
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D.2.A3 Helicobacter pylori infection as a cause of stomach ulcers.
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To protect the stomach wall from its own acid and digesting enzymes, a mucus lining covers the surface.
D.2.A3 Helicobacter pylori infection as a cause of stomach ulcers.
D2 Digestion
Contrast endocrine glands with exocrine glands.
D.2.U2 Exocrine glands secrete to the surface of the body or the lumen of the gut.
Secrete other stuff (sweat, oil, wax, enzymes etc) into ducts (a pipe or tube)
Secrete hormones directly into the bloodstream
Common ENDOCRINE GLANDS
D2 Digestion
Contrast endocrine glands with exocrine glands.
D.2.U2 Exocrine glands secrete to the surface of the body or the lumen of the gut.
Common EXOCRINE GLAND that connects with the pancreatic duct and eventually… the duodenum
D2 Digestion
Contrast endocrine glands with exocrine glands.
D.2.U2 Exocrine glands secrete to the surface of the body or the lumen of the gut.
Exocrine Gland Acinus:
D2 Digestion
Label a diagram of an exocrine gland with the following terms: secretory cells, lumen, duct, secretory vesicles, basement membrane and acinus.
D.2.U2 Exocrine glands secrete to the surface of the body or the lumen of the gut.
The blood vessel supplies the cells of the acinus with the nutrients for their functioning, and takes away their waste
D2 Digestion
Label a diagram of an exocrine gland with the following terms: secretory cells, lumen, duct, secretory vesicles, basement membrane and acinus.
D.2.U2 Exocrine glands secrete to the surface of the body or the lumen of the gut.
Secretory Cells:
A single layer of cells that synthesize molecules for secretion (i.e. digestive enzymes that are released from the cell)
D2 Digestion
Label a diagram of an exocrine gland with the following terms: secretory cells, lumen, duct, secretory vesicles, basement membrane and acinus.
D.2.U2 Exocrine glands secrete to the surface of the body or the lumen of the gut.
Lumen:
The hollow space inside a gland or tube
D2 Digestion
Label a diagram of an exocrine gland with the following terms: secretory cells, lumen, duct, secretory vesicles, basement membrane and acinus.
D.2.U2 Exocrine glands secrete to the surface of the body or the lumen of the gut.
Duct:
A tube structure for passage of the secreted material
D2 Digestion
Label a diagram of an exocrine gland with the following terms: secretory cells, lumen, duct, secretory vesicles, basement membrane and acinus.
D.2.U2 Exocrine glands secrete to the surface of the body or the lumen of the gut.
Vesicle:
Small, membrane bound sacs in the cell that store and transport the molecule that will be secreted.
D2 Digestion
Label a diagram of an exocrine gland with the following terms: secretory cells, lumen, duct, secretory vesicles, basement membrane and acinus.
D.2.U2 Exocrine glands secrete to the surface of the body or the lumen of the gut.
Exocytosis:
Secreted molecules are released from the cell by fusion of the vesicle membrane and cell membrane.
D2 Digestion
Label a diagram of an exocrine gland with the following terms: secretory cells, lumen, duct, secretory vesicles, basement membrane and acinus.
D.2.U2 Exocrine glands secrete to the surface of the body or the lumen of the gut.
The full acinus is surrounded by a “basement membrane”
The basement membrane is a thin, fibrous “extracellular” layer that provides support to the cells, limits contact between cells and the other cell types in the tissue and acts as a filter allowing only water and small molecules to pass through.
D2 Digestion
Label a diagram of an exocrine gland with the following terms: secretory cells, lumen, duct, secretory vesicles, basement membrane and acinus.
D.2.U2 Exocrine glands secrete to the surface of the body or the lumen of the gut.
1. When the food leaves the stomach, it enters the duodenum (Small Intestine)
2. Secretin and CCK are secreted from the S. Intestine
3.1 When fats and proteins enter your small intestine, cholecystokinin triggers your gallbladder and pancreas to contract and deliver bile and enzymes
3.2 When acidic food enters the duodenum, Secretin triggers bicarbonate to be released from the pancreas
Secretin Inhibits Gastrin
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This is a bit of mucus-secreting exocrine gland. Find:
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Can you explain how this deflated balloon can be an analogy for an acinus?
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Checkpoint
Plasma membrane
Secretory vesicles
Golgi apparatus
Rough ER
Mitochondria
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List four features that can be used to identify villus epithelium cell as viewed in electron micrographs.
D.2.S1 Identification of exocrine gland cells that secrete digestive juices and villus epithelium cells that absorb digested foods from electron micrographs.
D2 Digestion
List four features that can be used to identify villus epithelium cell as viewed in electron micrographs.
D.2.S1 Identification of exocrine gland cells that secrete digestive juices and villus epithelium cells that absorb digested foods from electron micrographs.
This is a secretory cell. You can see the nucleus (Nu) and many layers of rough ER. The vesicles (Z) are carrying a product that will be secreted through exocytosis into the lumen (L) of the duct. You can also see some mitochondria (M)
What do you notice about the location of the secretory vesicles relative to the lumen? Why are they like that?
vesicle
Why must secretory cells have so many mitochondria?
Why are secretory cells jam packed full of rough ER and Golgi?
Digestive System Exocrine Glands
HIGHLIGHT
HIGHLIGHT
HIGHLIGHT
Salivary glands secrete saliva
The liver secretes bile (which is then stored in the gallbladder)
The pancreas secrete “pancreatic juice”
Stomach
ADD & HIGHLIGHT
Glands in the stomach secrete “gastric juice”
D2 Digestion
State the name and location of three exocrine glands associated with the alimentary canal.
Can you explain how this collection of balloons can be an analogy for a salivary gland?
D2 Digestion
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Stomach ulcers are areas where the mucus layer has eroded, leaving the stomach muscle layers unprotected and exposed to gastric acids and digestive enzymes.
D.2.A3 Helicobacter pylori infection as a cause of stomach ulcers.
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D.2.A3 Helicobacter pylori infection as a cause of stomach ulcers.
1) H. pylori invading mucous layer�2) H. pylori neutralizing surroundings using the enzymic activity of urease�3) H. pylori colonization mucous layer�4) H. pylori causing inflammation, mucosal degradation, and cell death
D2 Digestion
D.2.A3 Helicobacter pylori infection as a cause of stomach ulcers.
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Stomach cancer can develop from ulcers (however, having an ulcer does not mean you will develop cancer.)
D.2.A3 Helicobacter pylori infection as a cause of stomach ulcers.
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D.2.A1 The reduction of stomach acid secretion by proton pump inhibitor drugs.
• State the role stomach mucus.
• State the cause of ulcer and acid reflux.
D2 Digestion
D.2.A1 The reduction of stomach acid secretion by proton pump inhibitor drugs.
• Outline the role of the H+, K+ -ATPase protein pump in the production of an acidic stomach.
These proton pumps secrete H+ ions (via active transport), which combine with Cl– ions to form Hydrochloric Acid acid
Certain medications and disease conditions can increase the secretion of H+ ions, lowering the pH in the stomach
• Outline the use, function and effect of proton pump inhibitors to treat gastric disease.
D2 Digestion
D.2.A1 The reduction of stomach acid secretion by proton pump inhibitor drugs.
D2 Digestion
Outline the cause and consequences of cholera infection.
D.2.A2 Dehydration due to cholera toxin.
D2 Digestion
Outline the cause and consequences of cholera infection.
D.2.A2 Dehydration due to cholera toxin.
D2 Digestion
Explain the effect of cholera toxin on intestinal cells.
D.2.A2 Dehydration due to cholera toxin.
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D.2.U7 Materials not absorbed are egested.
Dietary fibre, or roughage, is the indigestible portion of food derived principally from plants and fungi (cellulose, chitin, etc.)
D2 Digestion
Define egestion.
D.2.U6 The rate of transit of materials through the large intestine is positively correlated with their fibre content.
Dietary fibre, or roughage, is the indigestible portion of food derived principally from plants and fungi (cellulose, chitin, etc.)
Egestion is the process of removing undigested or indigestible material
D2 Digestion
D.2.U7 Materials not absorbed are egested.
Guts (start at 4:30)
I YOU
What was Beaumont's big discovery?
D.2.NOS
Serendipity and scientific discoveries—the role of gastric acid in digestion was established by William Beaumont while observing the process of digestion in an open wound caused by gunshot.