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Oral Cavity
- 1. Salivary glands
- a. Mammals have three major sets of salivary glands
- i. Parotid
- 1. Under ear
- ii. Sublingual
- 1. Under tongue
- iii. Submandibular
- 1. Around mandible
- b. Saliva and salivary amylase
- i. Salivary amylase is the enzyme that begins digestion of carbohydrates
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Stomach
- J-shaped
- 1.
Main part is the fundus - 2. Narrow part is the pylorus, where the pyloric sphincter is
- 3. Flattened mucosa has holes, openings into gastric glands, called gastric pits (beneath lumen)
- a. Contain chief cells, which secrete pepsinogen
- b. Contain parietal cells, which secrete hydrocholoric acid
- c. Contains cells that release the hormone, gastrin
- d. Secretes mucus
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Chief cells
- a. secrete pepsinogen
- i. Pepsinogen generally is called a Zymogen
- 1. Inactive form of an enzyme
- a. Not active; won’t digest anything
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parietal cells
- a. secrete hydrocholoric acid
- i. HCl is needed to activate pepsinogen to pepsin which is a protein-splitting enzyme that begins the digestion of protein
- ii. Because of acidity, chyme has an acidity of 2
- Needs to be acidic to activate pepsinogen
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gastrin and mucus
- i. Hormone that increases gastric motility (enhances churning and peristalsis) and also increases gastric juice release
- 1. Gastrin and parasympathetic do the same thing and work at the same time
Mucus:protectslining
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Small Intestine
- 1. All of the enzymes present in the small intestine come from the small intestinal gland, pancreas, have bile
- a. They won’t function in acidic environment
- i. Acid chyme has to be neutralized
- 1. It’s the sodium bicarbonate salts from the pancreas that neutralize the acid chyme when it comes in the small intestines
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Small Intestine Villi
- 1. The small intestine projects the villi and sends a small part below the villus
- a. The portion of the mucosa that dips below the luminal surface are the intestinal glands
- i. Called Krypts of Lieberkuhn
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Small Intestine Krypts
- 1. Name of small intestinal glands
- 2. Secrete lots of enzymes
- a. Lipases, nucleases, peptidases
- 3. Also secretes some hormones
- a. One is secretin
- i. An intestinal hormone which is released when acid chyme enters the small intestines
- ii. Goes out and affects pancreas, causing pancreas to secrete sodium bicarbonate salts
- iii. Secretin controls sodium bicarbonate salt release (acts when acid chyme enters the small intestine)
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Small Intestine structure
- i. Duodenum is a C-shaped structure
- ii. Jejunum and Ileum
- 1. Highly coiled region of the small intestine
- 2. Loose
- iii. Ileocolic (ileocecal sphincter)
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Small Intestine and Associated Glands
- a. All of digestion is completed in the small intestines, which is the reason why the accessory glands, the pancreas and liver, have to send juices in there
- 1. Not all of the enzymes that work with the small intestine come from the small intestines, or juices
- a. Additions Enzymes from pancreas
- b. Juices from pancreas and liver (sodium bicarbonate and bile, respectively)
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One function of the small iintestine
- a. Most absorption in small intestine
- i. All the nutrients are absorbed
- ii. Lots of water is absorbed
- b. Anything not absorbed is moved to the colon
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Small Intestine Modifications
- i. Plicae: circular or pleated folds that distend when chyme starts entering
- ii. Villi: Simple columnar has undulating waves within the wall
- 1. Villi: fingerlike projections of the lumen
- a. Goes below into submucosa; doesn’t stop at mucosal region
- i. Portion that goes below forms the glands of the small intestine, called the Krypts of Lieberkuhn
- iii. Microvilli
- 1. Each simple columnar cell, on apical (free) border, have microvilli
- b. All increase surface area in the small intestine
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Small Intestine Krypts of Lieberkuhn and hormones
- reaction to chyme entering
- i. Where you have the intestinal glands
- ii. Produce a variety of enzymes
- iii. Releases hormones
- 1. Chyme entersà distension of small intestineà causes parasympathetic to stimulate release of digestive juicesàenterokinase
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Small intestine and enterokinase
- 1. Enterokinase—hormone like substance
- a. Function: to activate trypsinogen that is released by the pancreas
- b. Comes from small intestine
- c. Once there is chyme in the small intestine, pancreas and glands release their material
- i. Trypsinogen (protein-splitting enzyme in inactive form active by enterokinase and forms trypsin)
- ii. Two other zymogens released by pancreas
- 1. Procarboxypeptidase
- 2. Chymotrypsin
- iii. Both are activated by trypsin
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CKP
- 1. Cholecystokininpancreozymin (CSK or CKP)
- a. Controls release of bile from the gallbladder and pancreatic enzymes (trypsinogen, chymotrypsinogen) from those structures into the duodenum
- i. Produced by small intestine when chyme enters
- 1. Distension causes parasympathetic stimulation
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i. No enzymes in small intestine function under __ conditions
1. Requires __
a. Done by __, secreted by __
- acidic
- neutralization
- secretin
- Krypts
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Secretin
- i. Hormone released by glands of small intestine; travels to pancreasà causes pancreass to release sodium bicarbonate salts, which are going to travel through pancreatic duct and into duodenum and neutralize the chyme
- ii. Due to reaction of acidic chyme coming in (control)
- ii. Only when chyme enters does the hormones be released; secretin is released in response to acidity
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beauty of invagination of the submucosa
- i. Design brings the submucosa up into the core of each villus
- 1. Brings capillaries of those two systems close to the area where absorption will occur because absorption is going to go through the simple comlumnar cells into the core
- a. They’ll be picked up by either the lymphatic or blood vascular system
- ii. Each villus has a core of submucosa, whose function is to bring blood capillaries and nerves in close proximity to the systems
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Core of the Villus
- i. Core of the villus
- 1. Connective tissue containing BV and LV and nerves
- a. In that core, we bring the capillaries close to the area where absorption is going to take place
- b. Facilitates absorption
- 2. If it were empty, we’d have to somehow transport it down the submucosal layer
- b. We’re bringing the mucosa up and filling the submucosa in there
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Colon
Function
- a. Functions:
- i. Absorption of some necessary water, drugs, some vitamins, and formation of the feces
- b. NO DIGESTION
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parts of the Small Intestine
- i. cecum- blind pouch
- 1. In man, off blind pouch is the appendix
- 2. No function; place where undigested seeds and junk can get caughtà appendicitis
- ii. Ascending colon:
- 1. Goes up right side of body until it gets to liver and turns
- iii. Transverse: straight (across abdominal)
- 1. Hits spleen
- iv. Descending
- 1. Down left
- v. When it hits the lower lumbar vertebrae, it makes an S-shaped curveà sigmoid colon
- vi. Rectum
- vii. Anus
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