digestive system Flashcards
ingestion
the first stage of digestion
- the process of taking in food/drink through the mouth
propulsion
movement of food through the digestive tract through both voluntary and involuntary processes
through:
- deglutition (swallowing)
- peristalsis
- gastric emptying
mechanical digestion
the physical breakdown of food into smaller pieces (with no alteration of its chemical composition)
increases surface area of food, making it easier for enzymes to chemically digest it
chemical digestion
breaking down food into simpler molecules using enzymes and digestive secretions
changes the chemical structure of food molecules so it can be absorbed by the body
areas:
- mouth (salivary amylase breaks down carbohydrates from starch -> maltose)
- stomach (pepsin (activated by stomach acid) breaks downs proteins -> peptides)
- small intestine (pancreatic amylase (continues carb digestion), trypsin chymotripsin and peptidase (breaks into amino acids), lipase (with bile from liver, breaks down fats -> fatty acids and glycerol)
absorption
digested food passing into the bloodstream or lymph to be transported to the body
* maybe add more
defecation
final stage of digestive process, where the body eliminates undigested food, waste products, and toxins from the digestive tract through feces
extracellular digestion
process of breaking down food outside the cells
intracellular digestion
food particles being taken by phagocytosis
peristalsis
involuntary wave like contractions that moves food, liquids, and other substances down the digestive tract:
- the GI tract has 2 layers of muscle (stomach has 3)
- circular muscles contact, squeezing the tube
- at the same time in the section inferior to the circular muscles, longitudinal muscles contract, widening tube and shortening it
deglutition
the process of swallowing, moving food from mouth to stomach
has 3 phases:
1. oral phase (voluntary) - the tongue pushes the food (bolus) towards the back of the mouth
2. pharyngeal phase (involuntary) - the bolus moves through the pharynx, the epiglottis closes over the trachea to prevent choking
3. esophageal phase (involuntary) - the bolus is pushed down by the esophagus by peristalsis into the stomach
chyme
when bolus is mixed with gastric juices in the stomach that moves into the small intestine
understand and label:
- organs in digestive system
- stomach
- intestines
- liver & gallbladder
roles it plays in food related functions in the buccal cavity:
- lips
the entrance to the mouth, with very vascular thin layer of keratin
- regulates what comes and goes in the mouth
roles it plays in food related functions in the buccal cavity:
- cheeks
confines food between teeth
- allows food to be chewed evenly during mastication
roles it plays in food related functions in the buccal cavity:
- hard palate
the bony structure that forms the roof of the mouth and separates the oral from the nasal cavity
- plays roles in digestion, speech, and breathing:
1. aids in chewing - lets the tongue have a space to press down on food
2. facilitates swallowing - helps push food toward the pharynx during swallowing
3. separates cavities - prevents food/liquids from entering the nasal passages
roles it plays in food related functions in the buccal cavity:
- soft palate
the flexible, muscular part at the back of the roof of the mouth
- plays a crucial role in swallowing, breathing, and speech
1. closes off the nasal cavity when swallowing- moves upwards to block the nasopharynx
2. prevents choking - works with the epiglottis to direct food down the esophagus and away from the airway
roles it plays in food related functions in the buccal cavity:
-uvula
the small dangly thang at the back of the back of ya throat (love u cardi)
1. aids in swallowing - helps close off the nasal cavity during swallowing
2. triggers gag reflex - acts as a protective mechanism to prevent choking by inducing a reflex when touched by large/foreign objects
3. assists in lubrication - produces saliva to keep throat most
roles it plays in food related functions in the buccal cavity:
- teeth
organs similar to bones that tears, grinds, and mechanically breaks down food
roles it plays in food related functions in the buccal cavity:
- tongue
a WORKHORSE????
1. facilitates ingestion
2. aids in mastication (chewing) - positions food between teeth for proper grinding
3. assists in swallowing (deglutition) - moves food towards the pharynx, initiating swallowing process
4. has taste buds to detect flavours
5. cleanses mouth - moves food particles away and helps stimulate saliva production for oral hygine
6. chemical digestion (lingual lipase for fat digestion)
muscles of the tongue perform 3 digestive functions in the mouth:
1. position food for optimal chewing
2. gather food into a bolus (rounded mass)
3. position food so it can be swallowed
roles it plays in food related functions in the buccal cavity:
- salivary glands
housed within mucous membranes of the mouth and tongue
- these minor exocrine glands constantly secrete saliva, directly into oral cavity of indirectly through ductws
- secretions increases when eating, because saliva is essential to moisten food and initiate the chemical breakdown of carbs
- small amts of saliva is also secreted by the labial glands in the lips
roles it plays in food related functions in the buccal cavity:
- lingual glands
located on the top and sides of the tongue, secretes a mucus and watery serous fluid that contains the enzyme lingual lipase, that plays a minor role in breaking down triglycerides (fats)
salivary amylase
produced by: salivary glands
function: breaks down polysaccharides (starch, glycogen) -> maltose
sucrase
produced by: small intestine
function: sucrose -> glucose + fructose
maltase
produced by: small intestine
function: maltose -> glucose
pepsin
produced by: stomach
function: proteins -> peptides
chymotrypsin
produced by: pancreas
function: proteins/ polypeptides -> peptides
trypsin
produced by: pancreas
function: proteins/polypetides -> peptides
carboxypeptidase
produced by: pancrease
function: amino acids at the ends of proteins -> amino acids + peptides
aminopeptidase
produced by: small intestine
function: peptides -> amino acids
dipeptidase
produced by: small intestine
function: double amino acids -> single amino acids
lipase
produced by: pancreas (pancreatic lipase), mouth (lingual lipase), stomach (gastric lipase)
function: triglycerides -> fatty acids/diglycerides
nucleotidase & phosphatase
produced by: small intestine
function: nucleotides -> phosphate ions, nitrogenous bases, pentose
ribonuclease
produced by: pancreas
function: RNA -> nucleotides
deoxyribonuclease
produced by: pancreas
function: DNA -> nucleotides
glucose
enters by: co-transport with Na+
leaves by: facilitated diffusion
fructose
enters by: facilitated diffusion
leaves by: facilitated diffusion
galactose
enters by: co- transport with Na+
leaves by: facilitated diffusion
amino acids
enters by: co-transport with Na+
leaves by: facilitated diffusion
monoglycerides
enters by: simple diffusion
leaves by: exocytosis of chylomicrons
fatty acids
enters by: simple diffusion
leaves by: exocytosis of chylomicrons
nitrogenous bases, pentose sugars, phosphates
enters by: active transport
leaves by: facilitated diffusion
oral cavity (function)
- ingests food
- chews and mixes food (mechanical digestion)
- begins chemical breakdown of carbs (via salivary amylase)
- begins some breakdown of lipids (via lingual lipase)
- moves food into pharynx
- moistens food
pharynx
- propels food from oral cavity to esophagus
esophagus
- propels food from oral cavity to stomach via peristalsis
-> has upper and lower sphincters that relax during swallowing to regulate the passage of food into the esophagus
stomach
- gastric juice produced via gastrin from gastric pits
- mixes and churns food with gastric juices to form chyme (mechanical digestion)
- begins chemical breakdown of proteins (pepsinogen released from walls, activated by HCl, now pepsin, turning protides into polypeptides)
- enhances activity of lingual lipase (lipids-> triglycerides)
- absorbs some fat-soluble substances
- releases food into duodenum as chyme
gastric juice components
HCl - increases the acidity of the stomach and activates pepsinogen into pepsin
Intrinsic factors - allows for the absorption of vitamin b12 in small intestine
Gastrin - triggered by presence of proteins and stretching of stomach walls
small intestine
- most important site of chemical digestion
- absorption of most water and nutrients (90%)
-> facilitated by increased surface area (villi and microvilli) - releases secretin (triggered by acid presence, causes pancreas to produce more pancreatic juice)
- releases CCK (triggered by digested protein and fat presence, initiates gallbladder contractions, increases liver output of bile and pancreqase output of pancreatic juice
components of intestinal juice
- bicarbonate ions: further neutralization of acidic chyme
- hormones: secretin, CCK
- mucus: lubrication
- enzymes:
carbs-> sucrase, lactase, maltase
proteins: aminopeptidase, dipeptidases (peptides to amino acids)
large intestine
- further breaks down food residues
- absorbs most residual water, electrolytes, vitamins
- propels feces towards rectum
- eliminates feces
liver
- produces bile (emulsifies lipids into smaller fatty droplets to aid digestion and absorption by increasing surface area)
- regulates blood glucose level (too much-> stores as glycogen,, too little-> releases as glucose)
- protein metabolism
- stores fat
- detoxifies alcohol and drugs
hepatic portal system
- allows modification of nutrients absorbed from the digestive tract by the liver cells
blood to liver is from:
1. the heart via the hepatic artery
2. from the intestine via the hepatic portal vein
bile leaves the liver via the hepatic duct that splits into:
1. cystic duct -> to the gallbladder for storage
2. common bile duct -> to the duodenum
pancreas
- islets of langerhans(cells) produces:
1. insulin -> cells take in glucose
2. glucagon -> causes liver to store as glycogen - creates pancreatic juice containing sodium bicarbonate to neutralize stomach acid
- makes pancreatic amylase (starch to maltose)
- makes pancreatic lipase (lipids to triglycerides)
- makes trypsinogen, chymotrypsinogen and other SHIT (in an inactive form, but digests proteins into peptides)
gallbladder
stores, concentrates, and releases bile
bile
- made from cholestoral
- not an enzyme (does mechanical, NOT chemical digestion)
- molecules are polar at one end and nonpolar at the other
- emulsify fats by breaking large globules of fat into smaller ones, preventing fat from reforming larger droplets
gastrin
- hormone produced by the stomach wall
- release triggered by the stretching of stomach/presence of proteins
- causes the gastric pits to secrete more gastric juice
secretin
-produced by the small intestine
- release triggered by the presence of acid in duodenum
- causes pancrea to produce more pancreatic juice (especially sodium bicarbonate)
cholecystokinin (CCK)
- produced by the small intestine
- released by the presence of digested protein and fat in small intestine
- initiates gallbladder contractions, increases liver output of bile and pancreas output of pancreatic juice
intestinal glands
- specialized glands in the mucosa of the small intestine
describe the 3 phases involved with the process of swallowing, including why food does not end up in the respiratory system (annotated diagram)
- buccal phase
- in the mouth (voluntary phase)
- tongue pushes against the hard palate
- forces the bolus to move into the pharynx - pharyngeal phase
- tongue continues to block off the mouth
- soft palate and uvula move to close nasopharynx
- larynx rises so that the epiglottis covers trachea (avoid respiratory system) - esophageal phase
- upper esophageal sphincter relaxes (opens)
- blus moves into the esophagus (and continues to move via peristalsis)
how do the tissue layers of the stomach differ from the rest of the alimentary canal? how does this difference allow it to better perform its function?
- mucosa - specialized for acid and enzyme secretion
- contain gastric pits leading to gastric glands that secrete hydrochloric acid, pepsinogen, and mucus
- mucus for protection, parietal cells for HCl, chief cells for pepsinogens - muscularis external - extra layer for churning
- stomach has 3 layers of smooth muscle
- inner oblique layer (unique to stomach), middle circular layer, outer longitudinal layer
- helps churn food - submucosa - rich in blood vessels and nerves
- contains extensive nerve network that helps regulate secretion and digestion - serosa - outer protective layer
- covers the stomach and connects it to surrounding structures, reducing friction
describe the function of the cells that make up the gastric pits of the stomach and how they contribute to the overall function of the stomach
- mucous cells
- secretes mucus and bicarbonate to protect stomach lining from acidic gastric juices - parietal cells
- secretes HCl and intrinsic factors
- HCl creates a low pH to activate pepsinogen to pepsin, and to also kill bacteria and pathogens in food
- intrinsic factors are essential for vitamin b12 absorption in small intestine - chief cells
- secretes pepsinogen and gastric lipase
- pepsinogen is converted to pepsin to begin protein digestion
- gastric lipase begins the breakdown of fats - enteroendocrine cells
- secretes hormones that regulate digestion
- g hormones secrete gastrin, stimulating HCl production by parietal cells
- regulates acids production
describe the 3 phases of gastric secretion
- cephalic phase (head)
- trigger: thought, smell, taste, or sight of food
- mechanism: brain stimulates stomach to start secreting gastric juices - gastric phase (stomach)
- trigger: food enters stomach, causing distension and chemical stimulation
- mechanism: stomach responds to food by secreting more gastric juices - intestinal phase (small intestine)
- trigger: chyme entering duodenum
- mechanism: small intestine regulates stomach activity
describe how the anatomical structure of the small intestine aids its role in digestive process
- long in shape, allowing sufficient time for digestion and absorption
- has circular folds that increases surface area
- contains villi, that has a capillary network and lacteal to absorb nutrients
- microvilli for further surface area
describe the steps involved in defecation
- mass movement of feces move into rectum, which distends (stretches) it, initiating defecation reflex
- parasympathetic reflexes cause the muscles in the rectum and sigmoid colon to contract
- the internal anal sphincter (involuntary) relaxes (opens) upon pressure and more pressure on the external anal sphincter
- however, motor neurons can cause the external anal spincter to remain contracted
- once these motor neurons are inhibited, the external anal sphincteer relaxes and feces passes through the anus
- contraction of the diaphragm and abdominal muscles can also assist in defecation - if defecation is delayed, the reflex contractions end, until more feces moves into the rectum
describe the regulation of defecation
- stimulus
- feces moves into and distend the rectum - receptor
- stimulates stretch receptors - control center
- the receptors transmit signals along afferent fibers to spinal cord - effector
- spinal relax is initiated
-> parasympathetic motor fiber stimulates the contraction of the rectum and sigmoid colon, and relaxation of the internal anal sphincter - output
- external anal sphincter relax so feces may pass
- pressure goes down
describe the homeostatic mechanism that gets triggered when chyme enters the small intestine and that involves the hormone secretin
- stimulus
- chyme enters small intestine (pH goes down) - receptor
- chemoreceptors detects the lowered pH (acidic) - control center
- secretion producing cells release secretin - effector
- blood stream reaches pancreas
- pancreas releases bicarbonate - output
- pH rises
describe the homeostatic mechanism that gets triggered when chyme enters the small intestine and that involves the hormone CCK
- stimulus
- chyme enters small intestine - receptor
- presence of lipids and proteins stimulates chemoreceptors - control center
- lining releases CCK - effector
- signals gallbladder to contract to release bile via bile duct, bile emulsifiers fats, makes easier for lipase enzymes to digest
- signals pancreas to release digestive enzymes, like lipase, amylase, protease - output
- food digested..?
describe the 6 major processes occurring during digestive system activity, and list all the organs of the gastrointestinal tract that perform each one
- ingestion (taking in food) - mouth
- propulsion (moving food through GI tract) - mouth, pharynx, esophagus, stomach, large and small intestine
- mechanical digestion (breaking down food physically) - mouth, stomach, small intestine
- chemical digestion (breaking down molecules into nutrients) - mouth, stomach, small intestine
- absorption (taking in nutrients into blood and lymph) - small intestine, large intestine
- defecation (eliminating waste) - large intestine, rectum, anus
describe and clearly distinguish between extracellular and intracellular digestion and state the specific locations in the human body where extracellular digestion occurs
breakdown of food outside of cells (using enzymes) vs. breakdown of food inside cells (within lysosomes)
Describe the anatomy of the esophagus by using correct anatomical terms to describe: its location in the human body, its overall structure, and the layers of tissue of which it is composed.
muscular tube located in the thoracic cavity, made of
- mucosa (innermost layer)
- submucosa
- muscularis external
- adventitia
Describe how each tissue layer of the esophagus contributes to the primary function of the esophagus.
Describe the vasculature delivering blood to and from the liver, and explain how this vasculature relates to the functions served by the liver in the body.
Describe and distinguish between the endocrine and exocrine functions of the pancreas.
Name two hormones secreted by the small intestine. For each hormone, state: the stimulus for its production, in which organ its target cells are located, and the effect(s) of its release.
Describe the chemical digestion of the following, specifying the source and the function of the principal enzymes involved: carbohydrates, proteins, lipids, and nucleic acids.
Describe the function of all the enzymes involved in carbohydrate digestion in the gastrointestinal tract. For each enzyme, state its name, source organ, site of action, substrate, and product.
Name the organ in the gastrointestinal tract within which the majority of chemical digestion of carbohydrates occurs.
Specify the end products of the carbohydrate digestion that occurs in the gastrointestinal tract.
glucose, fructose, galactose
Explain where and how each end product of carbohydrate digestion ultimately is absorbed from the lumen of the gastrointestinal tract into the blood.
Name the organ in the gastrointestinal tract within which the majority of chemical digestion of proteins occurs.
Specify the end products of the protein digestion that occurs in the gastrointestinal tract.
Explain where and how each end product of protein digestion ultimately is absorbed from the lumen of the gastrointestinal tract into the blood.
Describe the function of all the enzymes involved in lipid digestion in the gastrointestinal tract. For each enzyme, state its name, source organ, site of action, substrate, and product.
Name the organ in the gastrointestinal tract within which the majority of chemical digestion of lipids occurs.
Specify the end products of the lipid digestion that occurs in the gastrointestinal tract.
Explain where and how each end product ultimately is absorbed from the lumen of the gastrointestinal tract into the blood.
Describe the type(s) of molecules that the end products of lipid digestion can be reassembled into, and what other functions they might serve.
Describe the function of all the enzymes involved in nucleic acid digestion in the gastrointestinal tract. For each enzyme, state its name, source organ, site of action, substrate, and product.
Name the organ in the gastrointestinal tract within which the majority of chemical digestion of nucleic acids occurs.
Specify the end products of the nucleic acid digestion that occurs in the gastrointestinal tract.
Explain where and how each end product of nucleic acid digestion ultimately is absorbed from the lumen of the gastrointestinal tract into the blood.
Describe the type(s) of molecules that the end products of nucleic acid digestion can be reassembled into, and what other functions they might serve.
Describe the pathways by which the nervous system regulates: gastric secretory activity during the cephalic phase of gastric secretion, gastric secretory activity during the gastric phase of gastric secretion, gastric secretory activity during the intestinal phase of gastric secretion.
Describe the hormonal regulation of gastric secretory activity during the cephalic phase of gastric secretion, gastric secretory activity during the gastric phase of gastric secretion, gastric secretory activity during the intestinal phase of gastric secretion, bile production and release, and pancreatic juice production and release.
major salivary glands
- submandibular glands - floor of mouth, secretes saliva thru submandibular ducts
- sublingual glands - lies below the tongue, using the lesser sublingual ducts to secrete saliva into the oral cavity
- parotid glands - lies between the skin and masseter muscle, near ears. secretes saliva through the parotid duct, located near the second upper molar tooth
lingual lipase
produced by: lingual glands
function: breaks down triglycerides (fats)-> free fatty acids
