Quiz 3

Question 1

what takes place inside the gastrointestinal tract (GIT)?

Answer 1

ingestion: intake of food
digestion: physical and chemical breakdown of food in the GI tract
absorption: movement of nutrients from within the digestive tract into circulation
elimination: the removal of undigested food (solid waste) from the body in the form of feces

Question 2

what are primary organs of the GIT?

Answer 2

1. structures associated with the oral cavity (teeth, tongue, hard and soft
   palate), pharynx: the shared region between the oral and nasal cavities towards the back of the mouth
2. esophagus
3. stomach
4. small intestine
5. large intestine

Question 3

what are accessory organs of the GIT?

Answer 3

accessory organs participate in digestion by producing and releasing digestive secretions, are not part of the GI tract (part of the digestive
system)
1. salivary glands
2. biliary system (liver, gallbladder,
and bile ducts)
3. pancreas
accessory organs release secretions into ducts that empty into the lumen of the GI tract

Question 4

what are the two types of digestion?

Answer 4

1. physical digestion accomplished by GI movement (GI motility), muscular movements that mix food with
   digestive secretions and moves food through the GI tract
2. chemical digestion of food accomplished by digestive secretions
   released from exocrine glands

Question 5

where do digestive secretions originate from?

Answer 5

digestive secretions come exocrine glands embedded in the lining of the GI tract and from accessory organs
accessory organs:
1. salivary glands: saliva
2. biliary system (liver and gallbladder): bile
3. pancreas: pancreatic Juice
GI tract:
stomach: gastric Juice
goblet cells embedded in the lining of the GI tract: mucus

Question 6

exocrine glands vs. endocrine glands

Answer 6

endocrine glands release hormones into the blood that regulate the process of digestion
exocrine glands release secretions into ducts that empty into the lumen of the GI tract and facilitate chemical digestion

Question 7

what are the sources of digestive enzymes?

Answer 7

saliva, pancreatic juice. gastric juice, and lining of the small intestine

Question 8

what do digestive enzymes do?

Answer 8

facilitate a specific chemical reaction called
hydrolysis (breaking chemical bonds by the addition of water)
proteins, triglycerides, and carbohydrates undergo chemical digestion by hydrolysis, forming small, simple molecules that can
be absorbed
proteins -> amino acids
triglycerides -> fatty acids
carbohydrates –> sugar molecules (glucose)

Question 9

what are the four tissue layers of the GIT?

Answer 9

mucosa: inner lining
submucosa: layer between mucosa and muscularis
muscularis: smooth muscle
serosa: outer covering

Question 10

what does the mucosa of the GIT do?

Answer 10

the mucosa is in direct contact with ingested food and exocrine glands release secretions needed for chemical digestion
goblet cells that produce mucus (thick, sticky, viscous material) that protects the
mucosal lining
endocrine glands that release hormones

Question 11

what is the function of the mucosal lining?

Answer 11

mucosal lining consists of epithelial cells, forms a barrier that regulates the movement of substances from the GIT into the bloodstream, allow nutrients to be absorbed and can block harmful substances from
entering the blood, depending on location GIT, mucosal lining can be highly permeable or highly restrictive, disruption of tight junctions can lead to disease states (celiac disease, inflammatory bowel disease, food
allergies)

Question 12

what does the submucosa of the GIT do?

Answer 12

submucosa is a highly vascularized layer
that lies between the mucosa and
muscularis, here blood vessels circulate
nutrients to and away from GI tract, lymphatic vessels circulate fat-soluble
nutrients away from the GI tract and an embedded network of nerves that regulate
digestion

Question 13

what does the muscularis of the GIT do?

Answer 13

muscularis consists of two layers of muscle with an embedded network of nerves, muscularis promotes physical digestion by mixing food with digestion secretions and keeps food moving through the entire
length of the GI tract

Question 14

what is peristalsis?

Answer 14

rhythmic wave-like series of muscular contractions followed by muscular relaxation that propels food forward in the GI tract

Question 15

what is segmentation?

Answer 15

process of mixing food contents in the
digestive tract with secretions to create a more uniform mixture, in the process, food is slowly propelled forward

Question 16

what does the serosa of the GIT do?

Answer 16

serosa is the outer layer of connective
tissue that encloses the GIT and anchors it in the abdominal cavity, it secretes fluid that lubricates and prevents friction between the
digestive organs (protection)

Question 17

what hormones regulate digestion?

Answer 17

GI hormones are produced by endocrine cells embedded in the mucosal lining of the stomach and small intestine, GI hormones are released into the blood that regulate digestion by:
- ↑↓GI motility
- ↑↓ release of GI secretions
- some GI hormones ↑↓ hunger/satiety

Question 18

what is the enteric nervous system?

Answer 18

embedded in the lining of the GI tract (submucosa and muscularis) are millions of nerves, signals play a critical role in maintaining optimal digestive functions, gathers information from sensors within the
lining of the GI tract
- ↑↓GI motility
- ↑↓ the release of GI secretions

Question 19

what are the types of receptors in the ENS?

Answer 19

mechanoreceptors: detect stretching caused by the presence of food in the GI tract
chemoreceptors: detect the chemical composition of food
osmoreceptors: detect how much liquid is present in the GI tract
these send signals to other regions of the GI tract and by sending signals to the CNS via the vagus nerve (brain-gut axis)

Question 20

what is the cephalic response?

Answer 20

in response to sensory stimuli the brain sends neural signals to GIT which trigger the release of GI secretions and increases gastric motility, prepares the GIT to begin receiving food

Question 21

what neurotransmitters does the ENS release?

Answer 21

serotonin is a neurotransmitter that regulates both GI and CNS
functions, ~90% of the body’s serotonin is
in the GIT, where it influences GI motility, secretion, and pain sensation
altered levels of serotonin may be a contributing factor in IBS, affecting
stool consistency, elimination frequency, and increased pain sensitivity in the colon

Question 22

what is a functional disorder?

Answer 22

disorders that affect physiological functions but cannot be explained by structural or biochemical abnormalities (no one identifiable cause)

Question 23

what are the 3 major functions of the digestive system?

Answer 23

digestion, nutrient absorption, the formation and elimination of unabsorbed food residue

Question 24

what triggers the release of saliva?

Answer 24

1. presence of objects (food) in the mouth (mechanoreceptors)
2. acidic beverages/foods (lemons, coffee, soft drinks)
   that damage tooth enamel particularly strong trigger
   saliva release
3. thought, sight, smell of food trigger release of saliva
   (cephalic response)

Question 25

what are the functions of saliva?

Answer 25

moistens food making it easier to swallow, dissolves food components, which enables taste, enzymatic digestion protects teeth by neutralizing acids produced by bacteria and acidic food/beverages

Question 26

what is xerostomia?

Answer 26

the (feeling of dry mouth) often (but not always) associated with insufficient saliva production, caused by parkinson's, some drugs, and aging

Question 27

what is flavor?

Answer 27

the combined sensory signals of taste (gustation) and smell (olfaction) perceived by the brain

Question 28

how is taste detected?

Answer 28

the surface of the tongue is covered with protuberances called papillae, embedded within papillae are hundreds of taste buds (taste cells) that contain gustatory (taste) receptors, saliva dissolves food, which releases molecules, referred to as tastants, that stimulate gustatory receptors that trigger neural signals that are sent to the brain where they are identified as sweet, sour, bitter, salt or savory

Question 29

what are the 5 tastants that stimulate gustatory receptors?

Answer 29

1. monosodium glutamate: umami (savory) 2. hydroxyl groups (-OH): sweet 3. hydrogen ions (H+): sour 4. alkaloids: bitter 5. sodium, potassium, chloride ions (Na+, K+, Cl-): salty

Question 30

how is smell detected?

Answer 30

olfactory receptors are embedded in the lining of the nasal cavity, aroma molecules in food (referred to as odorants) are detected by olfactory receptors, stimulation of olfactory receptors send signals the brain, the brain (frontal cortex) interprets gustatory and olfactory signals to create the true flavor of food, majority of flavor determined by olfaction

Question 31

what is mastification?

Answer 31

chewing, the process whereby teeth grind food into smaller pieces, begins the process of physical digestion

Question 32

how does swallowing work?

Answer 32

soft mass of chewed food is called a bolus, tongue pushes bolus against the hard palate and eventually towards the back of oral cavity, initiate swallowing, soft palate and uvula rise, blocking the nasal passage, this prevents food from entering nasal cavity

Question 33

what is dysphagia?

Answer 33

conditions that weaken or damage the muscles and nerves used for swallowing, caused by neurodegenerative diseases (cerebral palsy, Parkinson's disease, Alzheimer's disease), conditions such as stroke and head trauma, anatomical such as scarring, tumors, cleft palate

Question 34

what is a cleft palate?

Answer 34

when the hard palate fails to fuse properly during embryonic development, resulting in an opening, often includes a split upper lip (cleft lip), food can enter the nasal cavity, making feeding difficult, requires surgical correction

Question 34

what prevents food from entering the lungs?

Answer 34

swallow, food passes through the pharynx (shared region between oral and nasal cavities) and into the esophagus, air passes through the pharynx but enters the lungs via the trachea, to prevent the bolus from entering the trachea, a flap-like structure called the epiglottis, covers the trachea and directs the bolus into the esophagus

Question 35

how is the gastroesophageal sphincter regulated?

Answer 35

peristalsis moves the bolus down the esophagus, causes the esophageal wall to stretch detected by mechanoreceptors, the stretching of the esophagus signals the gastroesophageal sphincter to relax, allowing the bolus to enter the stomach, once bolus enters the stomach, gastroesophageal sphincter closes, preventing the contents of the stomach from reentering the esophagus

Question 36

what are the three digestive events in the stomach?

Answer 36

1. chemical digestion: gastric juice 2. physical digestion: gastric motility 3. storage: temporary holding chamber

Question 37

what hormone is released when the stomach is empty?

Answer 37

when the stomach is empty, endocrine cells embedded in the mucosal lining of the stomach release the hormone ghrelin, ghrelin signals the brain, which in turn stimulates hunger and gastric motility (churning)

Question 38

what hormone is released when food enters the stomach?

Answer 38

the arrival of food into the stomach stimulates release of a hormone called gastrin, food causes stomach walls to stretch (mechanoreceptors), which triggers the release of gastrin (hormone from endocrine cells in the mucosal lining of the stomach) gastrin: ↑ release of gastric juice,↑ gastric motility

Question 39

what are gastric pits?

Answer 39

invaginations in the mucosal lining of the stomach that release components of gastric juice (digestive enzyme, HCl, intrinsic factor, goblet cells: mucous producing cells)

Question 40

what are goblet cells?

Answer 40

mucus producing cells located at the surface of gastric pits, secrete mucus that creates the gastric mucosal barrier that protects the gastric mucosal lining from the acidic gastric juice, if gastric mucosal barrier compromised, cause gastritis, ulcers, and increase risk stomach cancer

Question 41

what are stomach ulcers?

Answer 41

lesion in the mucosal lining of the GIT (typically in stomach, duodenum, and/or esophagus), can lead to complications such as bleeding and increase risk of cancer, majority of ulcers not caused by stress, diet, or lifestyle, majority ulcers caused by a bacterium (Helicobacter pylori) that degrades the protective gastric mucosal barrier, causing inflammation and localized damage

Question 42

what is intrinsic factor?

Answer 42

intrinsic Factor (IF) is needed for absorption of vitamin B 12 (vitamin B 12 assists in formation of red blood cells and formation of myelin sheath on nerves (neurons)

Question 43

what is megalobastic anemia vs pernicious anemia?

Answer 43

megalobastic: vitamin B12 deficiency characterized by large (macrocytic) nucleated (immature) red blood cells, which impairs ability to deliver oxygen to tissues, can cause neurological problems since B12 is needed for the formation of myelin sheath pernicious: autoimmune disorder that attacks the cells that make IF which interferes with B12 absorption

Question 44

how does the stomach contribute to digestion?

Answer 44

instead of 2 layers, the muscularis in the stomach has a third muscle layer that helps mix food with gastric juice, as a result of vigorous mixing of food with gastric secretions, food physically/chemically transformed into an acidic, paste-like substance called chyme

Question 45

how is food stored?

Answer 45

rugae: ridges produced by folds in tissue as the stomach fills with food, the rugae unfold and flatten, this allows the stomach to hold large volumes of food (capacity of 1-2 liters), stretching (mechanoreceptors) of stomach walls signal satiety to the brain

Question 46

how does gastric emptying work?

Answer 46

peristalsis pushes chyme towards the base of the stomach (pylorus), the pyloric sphincter regulates the flow of chyme from the stomach into the small intestine, only small amounts of chyme exit the stomach at any one time, large volume increases the rate of gastric emptying (more distention), liquids have a faster rate of emptying than solids (solids must be liquefied), high fat foods decrease gastric emptying rate compared to low fat foods

Question 47

what is pyloric stenosis?

Answer 47

a thickening of the pyloric sphincter, typical age of onset between 2 – 8 weeks when milk is unable to pass through the pyloric sphincter which prevents milk from leaving the stomach and entering the small intestine (symptoms: projectile vomiting, weight loss, hungry after feeding, and dehydration)

Question 48

what are the three sections of the small intestine?

Answer 48

duodenum: chyme mixes with secretions from the pancreas and gallbladder, where the majority of chemical digestion takes place jejunum: where majority of nutrient and water absorption takes place ileum: absorption of remaining nutrients, mostly vitamin B12

Question 49

how do hormones regulate gastric emptying?

Answer 49

cholecytokinin (CCK): communicates satiety to the brain and decreases gastric motility and the release of gastric secretions gastric inhibitory peptide: decreases gastric motility and the release of gastric secretions

Question 50

what does GLP-1 do?

Answer 50

the presence of food in the stomach (gastric stretching) and nutrients in the SI stimulates the release of GLP-1 which acts on the hypothalamus to: - increases feelings of fullness - reduces overall food intake - helps regulate body weight - GLP-1 acts on the stomach to decrease gastric emptying

Question 51

what is the enterogastric reflex?

Answer 51

the presence of chyme in the duodenum causes the duodenum wall to stretch (mechanoreceptors), in response, a neural signal is sent to the brain, the brain responds by sending a neural signal to the stomach that slows gastric motility and release of gastric juice, slows gastric emptying, giving the SI time to carry out its digestive functions

Question 52

what does pancreatic juice do?

Answer 52

aid in chemical digestion in the small intestine, pancreatic juice is alkaline (bicarbonate), which neutralizes chyme as it enters the duodenum, pancreatic juice contains enzymes needed for the digestion of CHO, protein, and lipids, pancreatitis (inflammation of the pancreas) can impact digestive enzymes from reaching the duodenum leading to nutrient malabsorption

Question 53

what does bile do?

Answer 53

bile is produced by the liver, transported through bile ducts to the gallbladder, where bile is stored, in response to the presence of fat in chyme, the hormone CCK causes the gallbladder to contract and release bile, bile aids in fat digestion by breaking large fat globules into small droplets (emulsification)

Question 54

what is enterohepatic circulation?

Answer 54

the liver is unable to synthesize enough bile acids to replenish bile, therefore it depends on the return of bile acids via enterohepatic circulation, enterohepatic circulation is the route where components of bile (bile bile acids) are recycled and reused bile flows liver ⇉ gallbladder ⇉ SI (emulsification) bile components flows SI ⇉ liver ⇉ (bile synthesized)

Question 55

what are gallstones?

Answer 55

pieces of solid material (cholesterol and bile pigments) that can lodge in bile ducts and block the release of bile, often results in the surgical removal of gallbladder, liver assumes role of gallbladder post-surgery, initial low-fat diet recommended

Question 55

what happens to undigested food?

Answer 55

undigested food residue passes from the SI into the large intestine where: 1. excess fluids are removed 2. microbial breakdown of undigested food residue 3. formation and elimination of solid waste the ileocecal sphincter regulates the movement of undigested food residue from the ileum into the cecum

Question 56

what are the three sections of the large intestine?

Answer 56

extends from the ileocecal sphincter (between ileum and cecum) to the anus 1. cecum 2. colon 3. rectum

Question 57

what are haustra and haustral contractions?

Answer 57

bands of connective tissue run along the wall of the LI, cause puckers (haustra) to form along the colon wall, when a haustrum (singular) fills with feces, it stimulates muscles to contract, pushes the feces to the next haustrum, referred to as haustral contractions (a specific type of motility that takes place in the colon), haustral contractions allow maximum absorption of water and electrolytes

Question 58

what are mass movements stimulated by?

Answer 58

1. stretching of the colon wall by feces (why high fiber diet, increases fecal bulk, promotes regular bowel movements) 2. gastrocolic reflex: a neural reflex that stimulates mass movements in the colon in response to eating

Question 59

what is diverticular disease?

Answer 59

when stool is too hard or too little fecal material, muscles strain to move feces, increased straining can cause weak spots in the colon to bulge outwards (diverticula), if fecal matter becomes trapped and inflamed then it turns into diverticulitis