The digestive system Flashcards
alimentary canal
- technically “outside the body”
- runs from the mouth to the anus and is sectioned off by sphincters
sphincters
circular smooth muscles around the canal that can contract to allow compartmentalization of function
Mechanical Digestion
Physical breakdown of large food particles into smaller food particles, but does not involve the breaking of chemical bonds
Chemical Digestion
Enzymatic cleavage of chemical bonds, such as peptide bonds in proteins, or glycosidic bonds of starches
Absorption
the transport of products of digestion from the digestive tract into the circulatory system
Pathway That Food Follows
Oral Cavity (Mouth) Pharynx Esophagus Stomach Small Intestine Large Intestine Rectum Anus
Role of parasympathetic and sympathetic nervous system?
The parasympathetic nervous system increases secretions from all of the glands of the digestive system and promotes peristalsis. The sympathetic nervous system slows peristalsis
What two main enzymes are found in saliva? What do these enzymes do?
- Salivary amylase(ptyalin)- digests starch into smaller sugars
- Maltose and dextrin- digests fast
Bolus
Mass of chewed food made by the tongue
Esophagus
Long muscular tube that carries food to stomach
Pharynx
Cavity between mouth and esophagus that serves as a passageway for food (and air)
“Throat”
Epiglottis
Covers the voice box to make sure food is routed to the esophagus
Mucous cell
Secretes: Mucus
Function: Protects lining of stomach, increases pH (bicarbonate)
Chief cells
Secretes: Pepsinogen
Function: Digests proteins, once activated by H+ from HCl released by parietal cell
Parietal cell
Secretes: HCl, intrinsic factor
Function: HCl decreases pH, kills microbes, denatures proteins, some chemical digestion; intrinsic factor absorption of vitamin B12
G-cell
Secretes: Gastrin
Function: Increases HCl production, increases gastric motility
Sucrase
Enzyme
- Brush-border hormone enzyme; breaks down sucrose into monosaccharides
Secretin
Hormone
-Increases pancreatic secretions, especially bicarbonate, reduces HCl secretion, decreases motility
Dipeptidase
Enzyme
-Brush-border enzyme; breaks dipeptides into free amino acids
Cholecystokinin
Hormone
-recruits secretion from gallbladder and pancreas; promotes satiety
Enteropeptidase
Enzyme
-Activates trypsinogen, which initiates an activation cascade
How do bile and pancreatic lipase work together?
Bile accomplishes mechanical digestion of fats, emulsifying them and increasing their surface area. Pancreatic lipase accomplishes chemical digestion of fats, breaking their ester bonds.
Anatomy of Small Intestine
- Duodenum
- Jejunum
- Ileum
Salivary Amylase
Produced by: Salivary glands
Site of Action: Mouth
Optimum pH: Neutral
Digests: Carbohydrates
Pancreatic Amylase
Produced by: Pancreas
Site of Action: Small Intestine
Optimum pH: Basic (8.5)
Digests: Carbohydrates
Functions of Pancreas
- Secretes enzymes into small intestine
- Secretes bicarbonate into small intestine to neutralize stomach acid
- Secretes insulin into the blood to keep blood sugar under control
What enzymes digest Carbohydrates
Salivary amaylase Pancreatic amaylase maltase isomaltase sucrase lactase
What enzymes digest Proteins
Pepsin(ogen) Trypsin(ogen) Chymotrypsin(ogen) (pro)carboxy peptidases A and B Aminopeptidase Dipeptidases Enteropeptidase
What enzymes digest fats?
Bile
Lipase
What are the main components of bile
- Bile salts- emulsify fats
- Pigments (bilirubin from the breakdown of hemoglobin)
- cholesterol
Where is bile synthesized, stored, and where does bile carry our its digestive function
Bile is synthesized in the liver, stored in gallbladder, and serves its function in the duodenum
What is the function of the liver?
Liver processes nutrients (through glycogenesis and glycogenolysis, storage and mobilization of fats and gluconeogenesis), produces urea, detoxifies chemicals, activates or inactivates medications, broduces bile, and synthesizes albumin and clotting factor
The accessory organs of digestion originate from wheat primary germ layer?
Embryonic endoderm
What are the two circulatory vessels in a villus? What biomolecules are absorbed into each?
- Capillaries - absorbs water soluble nutrients, like monosaccharides, amino acids, small fatty acids, water-soluble vitamins and water
- Lacteals- absorbs fat-soluble nutrients, like fats, cholesterol and fat-soluble vitamins
What are the 4 fat soluble vitamins?
“Karen Eat Apples Daily”
K, E, A, D
3 sections of large intestine and their functions?
- cecum- out-pocketing that accepts fluid from the small intestine through the ileocecal valve and is the site of attachment of the appendix
- colon- divided into ascending, transverse and sigmoid portions; absorbs salts and water
- rectum- stores feces which are then extracted through he anus
What does gut bacteria do?
produces vitamin K and biotin (Vitamin B7)
