Digestive System - Anatomy and Physiology Laboratory Flashcards
the structures of the digestive system can be placed into two groups:
- organs of the alimentary canal
- accessory digestive organs
organs of the alimentary canal
oral cavity, pharynx, esophagus, stomach, small intestine, and large intestine
accessory digestive organs
teeth, tongue, salivary glands, liver, gallbladder, and pancreas
takes in food, breaks it down into its nutrient building blocks, absorbs the nutrients, and then rids the body of indigestible waste products.
digestive system
is a physical process that increases the surface area of ingested food and prepares it for chemical digestion by enzymes
Mechanical digestion
are examples of the mechanical breakdown of food
chewing of food in the mouth and the churning of food in
the stomach
involves the action of hydrolytic enzymes that chemically break macromolecules (carbohydrates, proteins, lipids, and nucleic acids) into their building blocks.
Chemical digestion
The processes involved in the mechanical and chemical digestion of food.
- Food is ingested and chemically and mechanically digested in the mouth into a bolus.
- The swallowing reflex propels the bolus to the stomach.
- The bolus is churned into chyme and chemically digested in the stomach.
- Chyme enters the duodenum and mixes with the pancreatic juice and bile.
- Nutrients are chemically digested and absorbed as chyme passes through the small intestine.
- Material passes into the large intestine where water, electrolytes, and vitamins are absorbed.
- Indigestible materials are excreted in the feces via defecation.
Building Blocks of Carbohydrates
Simple sugars (monosaccharides)
Building Blocks of Proteins
Amino acids
Building Blocks of Lipids (Triglycerides)
Fatty acids and glycerol
Building Blocks of Nucleic Acids
Nitrogenous base, pentose sugar, phosphate ions
Enzymes That Chemically Digest Carbohydrates
- Salivary amylase
- Pancreatic amylase
- Intestinal amylase
- Sucrase
- Maltase
- Lactase
salivary gland
Salivary amylase
acinar cells of pancreas (carbohydrates)
Pancreatic amylase
small intestine
Intestinal amylase
brush border cells of small intestine
sucrase, maltase, lactase
Enzymes That Chemically Digest Proteins
Pepsin
Trypsin and chymotrypsin
Peptidases
chief cells of stomach (proteins)
Pepsin
pancreas
Trypsin and chymotrypsin
Enzymes That Chemically Digest Lipids (Triglycerides)
Gastric lipase
Pancreatic lipase
Intestinal lipase
brush border cells of small intestine (proteins)
peptidase
chief cells of stomach (lipids)
Gastric lipase
acinar cells of pancreas (lipids)
Pancreatic lipase
brush border cells of small intestine (lipids)
Intestinal lipase
Enzymes That Chemically Digest Nucleic Acids
Nucleases
Nucleosidases
Phosphatases
acinar cells of pancreas (nucleic acids)
Nucleases
brush border cells of small intestine (nucleic acids)
Nucleosidases, Phosphatases
Enzymes exhibit specificity; they act only on particular substances called
substrates
are proteins that function as biological catalysts; that is, they allow chemical reactions to occur very quickly.
enzymes
Each enzyme has an ____________, a pocket on its surface to which a substrate binds to form an ____________________________.
active site; enzyme–substrate complex
Environmental conditions such as increased temperature or decreased pH can cause enzymes to unfold, altering their three-dimensional shapes.
Denaturation
the enzyme can no longer perform its role as a biological catalyst
Denaturation
The type of macromolecule that first begins to be chemically
digested in the alimentary canal is
carbohydrates
breaks down starch (a kind of polysaccharide) into shorter oligosaccharides and disaccharides.
salivary amylase
Starch digestion continues until salivary amylase is inactivated by acidic _________________ in the stomach.
gastric juices
Starches that are not broken down in the oral cavity are
broken down in the small intestine by
intestinal amylase and pancreatic amylase
produce the enzymes sucrase, maltase, and lactase, which hydrolyze sucrose, maltose, and lactose, respectively, into their constituent monosaccharide building blocks.
intestinal brush border cells
Chemical digestion of proteins begins in the
stomach
contains cells that secrete both hydrochloric acid (HCl) and pepsinogen.
gastric mucosa
The gastric mucosa contains cells that secrete both
hydrochloric acid (HCl) and pepsinogen
chemically break down the large polypeptides to smaller polypeptides and peptides
trypsin and chymotrypsin
Lipids include
triglycerides, steroids, and phospholipds
Triglycerides, also called
neutral fats
are the most abundant dietary lipids.
Triglycerides
are difficult to chemically digest because they are hydrophobic and thus tend to aggregate in large spherical droplets within the aqueous fluid in the digestive tract
Lipids
The formation of droplets greatly reduces the surface area of lipid on which the water-soluble _______________ (fat-digesting enzymes) can act, because the enzymes can contact lipid molecules only on the outer surface of the droplets.
lipases
stimulates the gallbladder to contract and release bile (which contains bile salts).
cholecystokinin (CCK)
Bile salts remain associated with the digested fats to form small spheres of lipids called
micelles
Most digestion of triglycerides occurs in the
small intestine
