Digestive System Flashcards
Mouth
Where the start of the digestive process begins, oral cavity is inside
Teeth
Used to mechanically start digesting food. Consist of incisors, canine teeth, premolars, and molars
Tongue
Used to taste food and shapes it into a bolus
Salivary glands
- Secrete saliva into the mouth
- Saliva contains:
- –Glycoprotein to lubricate food for easier swallowing
- –Buffers to neutralize food (prevents tooth decay)
- –Antibacterial agents to get rid of bad bacteria
- –Amylase, which hydrolyzes starch
Pharynx
- The throat, has openings to both the esophagus and the pharynx
- Leads to both the esophagus and the trachea
- Food and air pass through
Epiglottis
A flap of cartilage and fibrous connective tissue over the opening of the larynx
Esophagus
A muscular tube that brings moves boluses from the pharynx to the stomach by peristalsis
Cardiac sphincter
A flap of muscle preventing the acidic contents (and chyme) from the stomach from moving up into the esophagus
Stomach (gastrin?)
- The place where partially digested food is stored, and chemical and mechanical digestion occurs
- Gastrin: hormone that stimulates the secretion of gastric juice
- Acid inhibits the release of gastrin –> less gastric juice
Pyloric sphincter
A flap of muscle controls the flow of partially digested food in the stomach to the small intestine
Liver
- Glucose in blood converted to glycogen and stored in the liver
- Synthesizes many proteins
- Changes toxins into less toxic forms (alchohol/drugs -> inactive form)
- Produces bile
Gallbladder
-Stores and concentrates bile
Pancreas
- Produces pancreatic juice (digestive enzymes + alkaline solution rich in bicarbonate)
- Bicarbonate:
- –Acts as a buffer to neutralize the acidity of chyme as it enter the small intestine (raise pH)
- –Prevents ulcers
- –Activates pancreatic enzymes (amylase, lipase, proteases)
- –Secretes insulin into the bloodstream
Small intestine
-In duodenum, mixing: chyme (from stomach), bile (from gallbladder), pancreatic juice, digestive enzymes (from gland cells in intestinal wall)
-All four types of large molecules are finished being digested here
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Cecum
-A pouch at the beginning of the large intestine, assists feces formation
Appendix
- A small fingerlike extension of the cecum that contains many white blood cells that make a minor contribution to immunity
- Stores beneficial bacteria, reboots intestine after illness, immune functions as well
- Prone to infection
Large intestine / Colon
- Absorbs water from the alimentary canal
- Remains of digestive food become more solid as they move along the colon by peristalsis
- Remaining water is absorbed and undigested solids are compacted into feces
- Home to mutualistic bacteria
Rectum
- The place where excrement is held until the body is ready to release it
- Right above the anus
Anus
-The opening where undigested materials are expelled
***What is the difference between mechanical and chemical digestion? Where does each happen?
-Mechanical: physically breaking the food into smaller pieces
-Chemical: enzymes break apart the food at a molecular level
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Where does hydrolysis of each macromolecule happen? What are the products? What enzymes digest each type of macromolecule?
MOUTH (salivary glands):
Starch —[amylase]–> maltose + other dissac
STOMACH:
Big polypep. —[pepsin]–> small polypep
Starch —[amylase]–> maltose + other dissac (PANCREAS)
Dissac —[sucrase, lactase]–> monosacc (S INT)
Big polypep —[trypsin]–> small polypep (PANCREAS)
Small polypep –[peptidase/protease]–> amino acids (S INT)
Fat globules —[bile salts/emuls.]–> fat droplets (LIVER)
Fats —[lipase]–> fatty acids + glycerol (PANCREAS)
What is the bolus?
-A lubricated ball of chewed food shaped by the tongue
What does the epiglottis do?
- Flap of cartilage and fibrous connective tissue
- Larynx moves upward and tips the epiglottis down over the opening to the larynx
- Prevents food from passing into the trachea
What is peristalsis?
-Waves of muscle contractions
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What is in gastric juice? Gastric glands?
- Gastric juice: mucus, enzymes, and strong acid (pH 2)
- –Mucous cells –> mucus (lubricates + protects cells lining in stomach)
- –Parietal cells –> H ions and Cl (combine in lumen to form HCl)
- –Chief cells –> pepsinogen (inactive form of pepsin)
What is the role of HCL in the stomach?
- HCl converts pepsinogen to pepsin
- Pepsin begins the chemical digestion of proteins
- Pepsin production activates more pepsinogen production
What is chyme? How does it leave the stomach?
- Chyme is the end product of digestion in the stomach
- Acidic gastric juices mixed with partially digested food
- Leaves through the pyloric sphincter to the small intestine
What is H. pylori and what role does it play in the digestive system?
- Acid tolerant bacteria
- Burrows beneath the mucus and releases harmful chemicals
- Loss of protective mucus and damages cells in stomach lining
- Stomach wall may erode to create a hole –> infection, internal bleeding
***Where is bile produced? Where is it stored? Where does it eventually go and what is its use (what is it for)?
- Produced in liver
- Stored in gallbladder
- Breaks fat into smaller droplets that lipase can act on (emulsifier)
- It forms micelles around fat droplets to keep them from clumping together and getting larger
- Goes into the small intestine when needed
What does the pancreas do in digestion?
***What are the roles of the liver in food metabolism?
What is the function of villi and microvilli in the small intestine? What would happen if someone’s villi were greatly reduced in size due to illness?
-They increase the surface area of the small intestine for absorption of nutrients
-If a person’s villi were greatly reduced in size, that person may not get enough nutrients to survive and may need to get surgery
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***What is the role of E.coli and other mutualistic bacteria in the large intestine? Are they beneficial or harmful in the L.I? In other parts of the body?
What is our microbiome? How is our intestinal microbiome impacted by the food we eat?
-An ecosystem of different bacteria on our skin and in our body
-Depending on the food we eat the diversity of the microbiome will increase or decrease
-Fibers that cannot be digested by the human body provide a major source of energy for bacteria
-Yogurt
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How can one increase or decrease the diversity of one’s intestinal microbiome? Is more diversity better?
How are the digestive systems of organisms adapted to the type of food they eat? (structural adaptations)
- Carnivore: large, expandable stomach
- Herbivores and omnivores have longer alimentary canals
- Herbivores have special chambers that house great numbers of microbes
- Many herbivorous mammals have cellulose-digesting microbes in the colon (and in a large cecum)
- Rabbits + some rodents eat some of their feces
- Cattle, sheep, deer: ruminants - four chambered stomach
***What are ulcers? What causes them and where do they most commonly occur?
- Ulcers happen when pepsin and HCl destroy cells faster than they can regenerate, eating through the stomach wall
- Mucus can be eroded by several causes: H. pylori bacterium infection or stomach exposure to: NSAIDS, alchohol, gastric hyper-acidity, cigarettes
- Result: damage to cells lining stomach
What is acid reflux / GERD and how can you treat it?
-Gastroesophageal reflux disease is when chyme from the stomach overflows through the gastroesophageal sphincter into the esophagus, irritating the lining of the esophagus
-It can be treated by lifestyle changes, medications, or possibly surgery
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Diarrhea, constipation (cause, treatment)
- Diarrhea: too much water in feces (not enough time in LI), frequent watery elimination, dehydration
- Constipation: not enough fiber in diet (too much time in LI), infrequent elimination and compacted feces
***What prevents HCl from destroying the stomach lining?
-Mucus helps protect against HCl and pepsin
-New cells lining the stomach are produced every 3 days (by mitosis)
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Lactose intolerance (cause, treatment)
- A lack of enzymes that can digest lactose in the small intestine causes digestive problems
- Inability to digest milk sugar, bloating + gas when dairy is consumed (produced by bacteria in intestines that feed on dissach. lactose)
- This leaves enzymes in the large intestine to deal with lactose, which cause gas and other problems
- Digestive enzymes can be taken to help with the problem
IBD (cause, treatment)
- Chronic inflammation of all or part of your digestive tract
- Severe diarrhea, pain, fatigue and weight loss
- Can be debilitating and sometimes leads to life-threatening complications
Intestinal gas
- Foods that produce gas (carbs)
- When partially digested carbs reach the small intestine, bacteria digest them, giving off gas as a by-product
Celiac disease (cause, treatment)
- Auto-immune disease
- Foods that contain gluten
- Gluten triggers an immune system reaction in the SI that causes inflammation, which damages villi and decreases nutrient absorption
- Treatment: gluten-free diet
How are fats, proteins, and carbs absorbed by the small intestine?
- Fatty acids and glycerol absorbed by epithelial cells -> recombined into fats -> transported to lymph vessel -> cells
- Amino acids and sugars -> pass out of intestinal epithelium -> across thin wall of capillaries into blood -> cells
Gallstones
“stones” of bile salts in gall bladder, can be eliminated through narrow bile duct into digestive system (painful)
