Unit 5: Digestive System Flashcards
What are the 5 functions of the digestive system?
Ingestion
Digestion
Propulsion
Absorption
Defecation
What are the 2 types of digestion?
Mechanical and chemical
Describe mechanical digestion and the methods
Physical breakdown of food into smaller particles
Chewing
Stomach churning
Bile action
Segmentation and peristalsis
Describe chemical digestion and 4 macromolecules it breaks down
Breaking chemical bonds in food to convert macromolecules to monomers
Polysaccharides (carbs) break down to monosaccharides (sugars)
Protein breaks down into amino acids
Fat/Lipids break down into monoglycerides and fatty acids
Nucleic acid breaks down into nucleotides
What is the chemical reaction called in chemical digestion?
Catabolism which uses hydrolysis to break down food
What are the 3 processes of digestion?
Motility
Secretion
Membrane transport
Describe motility of the GI tract
Muscle contractions break up food, mix it with enzymes, and move it along the tract
Describe secretion in the GI tract
Release of digestive enzymes and hormones into the GI tract
Describe membrane transport in the GI tract
Absorption of nutrients into epithelium, blood vessels, and lacteals
The GI tract stretches from
mouth to anus
What are the 6 accessory organs to the GI tract
Teeth
Tongue
Salivary glands
Liver
Gallbladder
Pancreas
What are the 4 layers of the GI tract walls (inner to outer)
Mucosa
Submucosa (with blood vessels and lymph vessels)
Muscularis
Serosa
What do the cheeks and lips do for the GI tract?
Keeps food in between the teeth for mastication
What does the tongue do for the GI tract?
Has sensory papillae and moves the bolus back toward oropharynx
What do the hard and soft palate do for the GI tract?
Soft palate - separates oral cavity from nasopharynx
Hard palate - separates oral cavity from larynx
What do teeth do for the GI tract?
Mastication and increasing surface area of food particles for enzyme penetration
What are the 4 components of saliva
Water
Amylase
Mucus
Lysozyme
Amylase is primarily for
starch digestion
What neutralizes the pH of saliva?
Bicarbonate
What do intrinsic salivary glands do?
Are inside mucosa of oral cavity
Constantly secrete saliva
What do extrinsic salivary glands do?
Connect to the oral cavity through ducts (parotid, submandibular, and sublingual)
Mainly to assist with digestion
What are the 2 phases of swallong?
Buccal phase (voluntary)
Pharyngeal-Esophageal phase (involuntary)
Describe the buccal phase of swallowing
Tongue pushes bolus towards the oropharynx
Describe the pharyngeal-esophageal phase of swallowing
Soft palate blocks nasopharynx and hard palate blocks larynx
Pharyngeal muscles push bolus to esophagus
Where does the esophagus stretch to/from
From the laryngopharynx to the cardiac region of the stomach
What kind of contractions does the esophagus use to move food
Peristalsis
What prevents acid reflux
Lower esophageal sphincter
What are the functions of the stomach?
Mechanical churning to break up/liquify chyme
Chemical digestion of proteins with pepsin
Absorbs water and some drugs, NOT nutrients
Describe the layers of the muscle wall
Inner mucosa layer has gastric glands/pits
Muscularis has 3 layers (instead of 2) for churning
What are the 5 gastric gland cells?
Goblet
Regenerative
Parietal
Chief
Enteroendocrine
Describe goblet cells
Secrete akaline mucus (protect lining from acid)
Describe regenerative cells
Do rapid mitosis and new cells migrate to surface
Describe parietal cells
Make HCl and intrinsic factor
Describe chief cells
Make pepsinogen
Describe enteroendocrine cells
Secrete hormones (like GASTRIN)
What does HCl do in stomach
Drops the stomach pH to 2-4 (acidic)
Activates pepsinogen to become pepsin
Breaks up tough cell walls and tissue
Converts iron to an absorbable form
Kills pathogens
What does intrinsic factor do
Secreted by parietal cells to help absorb B12 in the small intestine
What does B12 help with
RBC production
Brain and nerve function
Memory
DNA synthesis
What is the function of pepsin
Pepsinogen (from chief cells) are converted to pepsin by HCl, which activates more pepsin
Pepsin digests proteins into small polypeptide chains and amino acids
Describe the body’s coordination of gastric motility
Swallowing center in brain signals the stomach to relax
Once food arrives in stomach, receptive-relaxation response occurs which further relaxes stomach
Churning from contractions help move chyme
What are rugae
The wrinkles in the lining of the stomach which allow for expansion
Where is stomach churning the strongest
Pyloric region to squeeze chyme into the duodenum
What are the 3 phases of gastric secretion?
Cephalic
Gastric
Intestinal
Describe the cephalic phase of gastric secretion
Vagus nerve stimulates secretion and motility (senses detect food)
Describe the gastric phase of gastric secretion
Once food enters stomach, gastric secretions triggered by ACh, gastrin, etc.
Stomach stretches and pH lowers
Describe the intestinal phase of gastric secretion
Duodenum inhibits stomach secretion and motility after its activity
Triggered by sensing fat in chyme enter the duodenum, which triggers release of secretin, cholecystokinin, and gastric inhibitory peptide
Describe cholecystokinin
Release in response to fat in the chyme entering duodenum
Causes gallbladder to contract, relaxes hepatopancreatic sphincter, and secretes pancreatic enzymes
Describe secretin
Released in response to acid in chyme entering duodenum
Increase bicarbonate secretion to neutralize the acids
Describe gastric inhibiting peptide
Released to decrease gastric motility and secretions
What does the liver do for digestion?
Produces bile which mechanically digests fat
What does the gallbladder do for digestion?
Stores and concentrates bile from the liver
What does the pancreas do for digestion?
Exocrine gland secretes digestive enzymes and pancreatic juice into duodenum
What are the 6 enzymes in pancreatic juice?
Trypsin
Chymotrypsin
Lipase
Amylase
Nuclease
Peptidases
How are carbohydrates digested?
Pancreatic lipase takes over for salivary amylase, finishes starch digestion
Brush border enzymes act on oligosaccharides and disaccharides
Those sugars are absorbed via active transport into cells and then use facilitated diffusion to move into the blood
How are proteins digested?
Begins in stomach with pepsin, when reaches sm. intestine pepsin is deactivated by pancreatic juice
Trypsinogen converts to trypsin which digests proteins and activates peptidases and chymotrypsinogen to further break peptides into amino acids
How are amino acids absorbed?
Active transport into cells and then into blood
How are lipids digested?
Bile acids emulsify fat globules
Lipases further break down triglyceride to fatty acid and monoglyceride
Absorb into cell through simple diffusion (because its a lipid) and then into LACTEALS through exocytosis
Nuclease hydrolyzes ______ into ______
DNA/RNA into nucleotides
Do vitamins change when absorbed?
No
Where are minerals absorbed?
Small intestine
What does the colon do?
Reabsorbs water, electrolytes, and bile salts
Mass movement
Defecation
Describe the process of defecation
Stimulated by stretched rectum
Internal anal sphincter relaxes involuntarily
External anal sphincter relaxes voluntarily
What does the lower esophageal sphincter do?
Prevent acid reflux back up esophagus
What does the pyloric sphincter do?
Regulates amount of chyme being moved from stomach into the duodenum
What does the ileocecal sphincter do?
Regulates the movement of feces into the cecum
What is the difference between peristalsis and segmentation?
Peristalsis moves in one direction
Segmentation moves in both directions
Where does peristalsis occur?
Esophagus and small intestine
Where does segmentation occur?
Small intestine and mostly large intestine
What is Celiac Disease?
Symptoms?
Risk groups??
Genetic and autoimmune disorder resulting in malabsorption of nutrients due to immune system attacking villi in small intestine when gluten present
Bloating, diarrhea, vomiting, weight loss
Genetic, other endocrine disorders such as Type 1 diabetes or thyroid disorder
What is Irritable Bowel Syndrome?
Symptoms?
Risk groups?
Disorder of large intestine, cause is unknown but can be linked to motility issues, faulty brain-bowel communication, and pain
Diarrhea OR constipation, cramping, bloating
Common, especially in women and those under 45
What are Peptic Ulcers?
Symptoms?
Risk groups?
Sore in the lining of the stomach or duodenum because of H. Pylori bacteria
Burning stomach pain between meals and at night, can be helped by antacids
Anyone who contracts H. Pylori, especially children
What is Hepatitis?
Symptoms?
Risk groups?
Inflamed liver from STI, autoimmune disorders, drugs or alcohol, or food virus
Vomiting, diarrhea, loss of appetite, change in urine/feces color, pain, and jaundice
Varies by cause and type of hepatitis contracted
What is Diverticulosis? Diverticulitis?
Symptoms?
Risk groups?
Deep pouches that bulge from colon, which can develop into diverticulitis if inflamed or infected
Asymptomatic, bloating, cramps, constipation, but can develop into severe symptoms like bleeding, tears, or blockages
Elderly, lack of fiber in diet
What is Lactose Intolerance?
Symptoms?
Risk groups?
Inability to digest lactose sugars because you have insufficient lactase enzymes
Gas, diarrhea, bloating after eating food with lactose
More common in African, Asian, Hispanic, and Native American population, elderly, prematurely born babies, or people with other intestinal diseases
