Digestion Overview Flashcards
Function of Oral cavity, teeth and tongue
Mechanical processing, moistening, mixing with salivary secretions
Function of Salivary glands
Secretion of lubricating fluid containing enzymes that break down carbohydrates
Function of Liver
Secretion of bile (lipid digestion), storage of nutrients, many other vital functions
Function of pharynx
Muscular propulsion of materials into the esophagus
Function of gallbladder
storage and concentration of bile
Function of esophagus
transport of materials to the stomach
Function of pancreas
Exocrine cells secrete buffers and digestive enzymes
Endocrine cells secrete hormones
Function of Stomach
chemical breakdown of material via acid and enzymes
Mechanical processing through muscular contraction
Function of Large Intestine
Dehydration and compaction of undigestiible material in prep for elimination
Function of Small Intestine
enzymatic digestion and absorption of water, organic substrates, vitamins and ions
Major salivary glands
Parotid
Submandibular
Sublingual
Function of the 2 main salivary glands
Lubrication
Oral hygiene
Digestion (amylase, lipase)
Lipase breaks down
fats
Amylase breaks down
carbs
How does saliva secretion occur?
Cl- is excreted into apical membrane of secretary epithelial cells building an electrochemical gradient which is maintained by Na-K-ATPase in the basolateral membrane
When Cl- is excreted, it draws Na, K, and Ca from the plasma into the lumen
This flux generates an osmotic gradient that draws water into the saliva until the osmolality of secretion equals the plasma
What are the salivary glands controlled by?
Autonomic nervous system
How are the salivary glands controlled?
Sympathetic and parasympathetic innervations
What does the sympathetic stimulation lead to?
Secretion of small volume of viscous saliva containing high enzyme concentration
“dry mouth”
What does parasympathetic stimulation lead to?
Accelerates secretion by all the glands resulting in large amounts of watery saliva
Phases of swallowing
Buccal (chewing)
Pharyngeal
Esophageal
Plica function
Have villi on them to help food flow in one direction
Help with absorption
Define Peristalsis
Combination of circular and longitudinal muscles to move the food
How do the muscles contract?
CIrcular contract first to mix and move the food and then longitudinal contract ahead of the food and then circular contract again to propel it down
Fundus where and what does it do?
Top of the stomach where gastric acid is produced
Parietal cells secretion
Produce HCL and intrinsic factor
Mucous cell secretion
Mucus which protects the epithelia from the acidic gastric acid
- Lack = ulcers
Chief cells secretion
Pepsinogen which is the precursor to pepsin which helps break down the food
Also produced in Brunner’s gland of duodenum
Enteroendocrine cell secretion
Hormones
G cell secretion
Gastrin
A cells secretion
Glucagon
D cell secretion
Somatostatin
Gastric lipase secretion
Helps break down fat
Acid secretion depends on:
Carbonic anhydrase and chloride/bicarbonate exchange
FInal pH of the stomach
1.5-3.5
Hydrochloric acid does what
Lowers the pH of gastric juice
Kills microorganisms
Breaks down cell walls and connective tissues in food
Activates chief cells (pepsinogen)
Acid secretion is inhibited by:
Somatostatin and prostaglandins (PGE2)
Enterochromaffin-like cells function
After gastrin stimulation due to food enter the fundus, release histamine which stimulates acid production
Parts of the small intestine:
Duodenum
Jejunum
Ileum
Duodenum
Where food enters
Acidic in nature
Reabsorption
Jejunum
Longest portion
Ileum
Connected to the large intestine (colon) via the cecum
Parts of the Large intestine
Ascending
Transverse
Descending
Goblet cells produce
Fat
Two ducts come together, what are they?
Common bile duct (gallbladder)
Pancreatic duct
Passage of food takes:
4-9 hours to reach the cecum
12-25 hours to travel from cecum to rectum
Chyme and water:
500-1500 mL of chyme enters large intestine
Less than 200 mL water is lost in feces
