Unit 5 Flashcards
What is the main function of the digestive system?
To acquire nutrients.
What are the seven GI tract organs from beginning to end?
- Oral cavity
- Oropharynx
- Esophagus
- Stomach
- Small intestine
- Large intestine
- Anus
What are the four accessory organs (outside the GI tract)?
- Salivary glands
- Pancreas
- Liver
- Gallbladder
What are the three GI tract layers from inner to outer layer?
- Mucosa
- Submucosa: submucosal plexus
- Muscularis externa: smooth muscle, myenteric plexus
What are the seven main digestive processes?
- Ingestion
- Motility
- Secretion
- Digestion
- Absorption
- Compaction
- Defecation
Explain ingestion.
Consumption. Eating.
Explain motility.
Movement of food through the GI tract.
Muscle contractions:
- Peristalsis: wavelike contractions
- Segmentation: various parts contract at the same time (net movement is distally)
Explain secretion.
Fluid and chemicals are entering the lumen of the GI tract:
- Mucus
- HCl from stomach
- Bicarbonate from pancrease
- Enzymes
- Hormones (not secreted in lumen, secreted in bloodstream)
- Bile
Explain digestion.
Chemical breakdown of large polymer molecules into small monomer molecules.
In digestion, carbohydrates (starch and sugars) are broken down by these six enzymes:
- Salivary amylase
- Pancreatic amylase
- Dextrinase
- Sucrase: located on microvilli
- Maltase: located on microvilli
- Lactase: located on microvilli
In digestion, proteins are broken down by these four peptidases enzymes:
Peptidases:
- Pepsin: stomach
- Trypsin: pancrease
- Chymotrypsin: pancrease
- Other peptidases located on microvilli of small intestine
In digestion, lipids are broken down by:
Bile and lipid emulsification
Breaking large fat globules into smaller fat droplets
Function of bile salts makes it easier to breakdown
Three enzymes that help breakdown lipids:
- Salivary lipase
- Gastric lipase
- Pancreatic lipase
In digestion, nucleic acids are broken down by this enzyme:
Nucleases
Explain absorption.
The movement of molecules and ions from the lumen into the body fluids.
Three types:
- Sublingual absorption of medicines (oral): nitroglycerin
- Gastric absorption (stomach): aspirin, alcohol
- Small intestine absorption: glucose, amino acids, vitamins and minerals are absorbed into CAPILLARIES; fatty acids absorbed into LACTEALS
Travel in bloodstream attached to lipoproteins: high-density lipoproteins and low-density lipoproteins
Explain compaction.
Dehydration of the chyme into fecal material by the absorption of water.
Explain defecation.
Pooping!
What are three sensors in stomach and intestines used for GI regulation?
- Mechanoreceptors: actiated by distension of the digestive walls by food (bolus or chyme)
- Chemoreceptors: activated by H+, proteins, and lipids in chyme
- Osmoreceptors: activated by amino acids and glucose
What are three sensory regulatory phases (based off of location) for GI regulation?
- Cephalic phase (activation in head): smell, taste, or thought of food stimulates CNS (brain) involvement… which stimulates digestive processes
- Gastric phase (activation in stomach): stimuli arising in stomach influences short and long pathways
- Intestinal phase (activation in small intestine): stimuli arising in small intestine influences short and long pathways and hormones
What are three integration and outputs (ways to influence effectors) for GI regulation?
1. Autonomic nervous system (parasympathetic and sympathetic):
- Long pathway
2. Enteric nervous system:
- Separate nervous system located within the GI wall
- Short pathway
- Submucosal and myenteric plexuses.
- Influenced by autonomic system.
3. Gastrointestinal hormones:
- Gastrin (stomach): releases HCl and pepsinogen, activates gastric motility, induces gall bladder and pancreatic secretions
- Cholecystokinin (CCK) (duodenum): contraction of gall bladder, stimulates pancreatic enzyme release, slows gastric motility
- Secretin (duodenum): stimulates bicarbonate release from pancreas and duodenal glands, inhibits gastrin production
- Glucose dependent insulinotropic peptide (GIP): stimulates insulin release, fatty acid metabolism
ANS → ENS → endocrine cells → hormones → blood → effectors
What are two neural pathways for GI regulation?
- Short pathway (stays w/in digestive system): receptor to intrinsic enteric plexuses out to effector (muscles and glands)
- Long pathway: receptor to CNS to autonomic to effector (muscles and glands)
What are two effectors for GI regulation?
- Secretory cells within digestive organs for production of HCl, bicarbonate, enzymes, and hormones.
- Smooth muscles within digestive organs used for motility.
Explain muscle activity or motility.
Self-generating graded potentials or slow waves… can produce action potentials.
STRENGTH of motility is influenced, not the RATE of contractions.
Autonomic nerves and hormones.
What are the four functions of the oral cavity and salivary glands?
- Mastication
- Taste
- Digestion of carbohydrates: salivary amylase digests starch and glycogen
- Cephalic phase and chemoreceptors (taste buds and olfactory) activate salivary secretion through parasympathetic stimulation
Describe the esophagus.
Muscular tube.
Upper esophageal sphincter.
Lower esophageal (cardiac) sphincter.
Acid reflux (heartburn) occurs here. Stomach acid leaks back into esophagus.
H2 antagonists (Zantac) slows down acid production. They’re histamine receptors.