3.4: Physiology of the GI Tract Flashcards
The digestive system has four main roles that it performs what are they?.
ingestion, digestion, absorption, and defecation
______ is when food enters the mouth.
Ingestion
______ occurs when food is moved, mixed, and exposed to enzymes along the gastrointestinal tract.
Digestion or food breakdown
Digestion can be divided into two parts what are they?
mechanical digestion and chemical digestion
______ digestion occurs when food is physically broken down into smaller pieces.
Mechanical
______ digestion occurs when the teeth chew food, when the stomach churns and mixes food, and as food is moved and squeezed along the gastrointestinal tract.
Mechanical
_____ digestion is the chemical breakdown of food by enzymes into smaller nutrients.
Chemical
______ is the process of moving digested food into the bloodstream.
Absorption
______ is the excretion of indigestible food from the anus.
Defecation
True or False: The mouth is where digestion begins, but only mechanical.
False. The mouth is where digestion begins, BOTH mechanical AND chemical.
How does the mouth Chemically digest food?
Chemically, saliva is released by the salivary glands. NOTE the locations of the parotid, sublingual, and submandibular glands
The enzyme___1___ contained in the saliva begins the chemical breakdown of ___2___.
- salivary amylase
- starches
How does the mouth Mechanically digest food?
Mechanically, the food is broken down into smaller physical pieces by both the teeth and tongue.
What is the food in the mouth called after it has been chewed?
The food is then called a bolus.
______, rhythmic muscular contractions, moves the food along the esophagus to the stomach.
Peristalsis
What is Peristalsis?
Rhythmic muscular contractions that moves food along the esophagus to the stomach.
True or False: No ingestion, digestion, absorption, or defecation takes place in the pharynx or esophagus. These structures only transport the food from the mouth to stomach by peristalsis.
True
Midsagittal view of the oral cavity and associated salivary glands (parotid, sublingual, and submandibular)
Once in the stomach, mechanical and chemical breakdown of food continues with the secretion of ______.
digestive juices
True or False: Substantial nutrient absorption occurs in the stomach.
False. Very little to no nutrient absorption occurs in the stomach.
The stomach’s main function is for ______.
mechanical and chemical breakdown of food
The ___1___ stimulates the stomach to secrete gastric juices, which contains: ___2___, ___3___, and ___4___
- hormone gastrin
- pepsinogens
- mucus
- hydrochloric acid
The ___1___ secrete hydrochloric acid, generating a pH of ___2___.
- parietal cells (located in the wall of the stomach body)
- 1.3-3.5
The parietal cells (located in the wall of the stomach body) secrete ______, generating a pH of 1.3-3.5.
hydrochloric acid
True or False: The very acidic pH of the hydrochloric acid produced by the Parietal cells of the stomach kill many of the bacteria ingested along with food. In addition, the low pH stops the activity of salivary amylase.
True
The secretion of hydrochloric acid is essential in the activation of ______.
pepsin
______ is secreted by the chief cells in the stomach.
Pepsinogen (a pro-enzyme)
Hydrochloric acid converts the___1___ into the active enzyme pepsin, which begins the breakdown of ___2___.
- inactive pepsinogen (secreted by the chief cells)
- proteins
______ protects the stomach lining from the hydrochloric acid and pepsinogens.
Mucus
The ______ churns and mixes the food, breaking it into smaller pieces.
muscularis externa
The smaller pieces allow for more ___1___ of the food to be exposed to the enzymes in the stomach to form ___2___.
- surface area
- chyme
___1___ moves the food toward the small intestine where the ___2___ controls the slow release of chyme into the ___3___.
- Peristalsis
- pyloric sphincter
- duodenum
In the small intestine digestion continues and ______ begins.
absorption
Enzymes from the ___1___ enter the small intestine to continue digestion of ___2___, and begin digestion of ___3___.
- pancreatic juices
- starches and proteins
- fat
______, which result from the first step in protein digestion, are digested by peptidases to amino acids.
Peptides
Peptides, which result from the first step in protein digestion, are digested by ___1___ to ___2___.
- peptidases
- amino acids
______, which results from the first step in starch digestion, is digested by maltase to glucose.
Maltose
Maltose, which results from the first step in starch digestion, is digested by ___1___ to ___2___.
- maltase
- glucose
Pancreatic juice includes three enzymes. What are they and what do they digest?
- amylase digests starch
- trypsin digests proteins
- lipase digests fats
______, which is also contained in the pancreatic juice, neutralizes the acidic chyme.
Bicarbonate
Bicarbonate, which is also contained in the pancreatic juice, neutralizes the ______.
acidic chyme
Chyme stimulates the small intestine to secrete two hormones:
cholecystokinin and secretin
______causes the gallbladder to secrete bile.
Cholecystokinin
______ causes the liver to secrete bile.
Secretin
Both Cholecystokinin and Secretin cause the ___1___ to ___2___.
- pancreas
- secrete its juices
______ breaks down fat into smaller pieces and is needed for the absorption of fats.
Bile
True or False: When food reaches the end of the small intestine, digestion is complete and most absorption of nutrients into the bloodstream has happened.
True
When food reaches the end of the small intestine, ___1___ is complete and most ___2___ has happened.
- digestion
- absorption of nutrients into the bloodstream
What remains of the food enters the large intestine by the ______.
ileocecal valve
In the large intestine, the undigested food is compacted in order to be prepared for ______.
defecation
Water is absorbed to form ___1___. ___2___ are absorbed as well.
- Feces
- Vitamins and ions
Bacteria metabolize the remaining nutrients, producing vitamins ___1___ and ___2___ in the process.
- K
- B
Feces travel to the ___1___ where it is defecated via the ___2___.
- rectum
- anus
Overview of digestive processes carried out from the mouth to the small intestine.
______ is the internal drive to find and eat food and is often experienced as a negative sensation such as churning, growling, or a painful sensation in the stomach.
Hunger
The ______ is a region of the brain that plays a role in hunger, satiety, and the feeling of “being full”.
hypothalamus
The amount of ______ in the blood begin to decline if a person has not eaten in a long period of time.
nutrients
The drop in nutrients in the blood stimulates the ______ in the hypothalamus and signals the body to feel “hungry” and desire to eat.
feeding center
True or False: If a portion of the hypothalamus is damaged or destroyed, from certain chemicals, trauma, surgery, or cancers, the regulation of hunger and satiety can be lost. In such an instance, the body no longer receives signals to stop eating and weight gain is almost certain.
True
Midsagittal view of the brain and brainstem. The hypothalamus (blue) is responsible for the regulation and monitoring of many processes in the body, such as hunger and satiety.
As the stomach expands from food intake and the nutrients consumed are absorbed, receptors within the stomach wall ______.
send signals to the brain and the desire to eat declines
The human body produces a variety of ______ that work together to balance our hunger and satiety.
hormones
______are compounds secreted into the bloodstream by one type of cell that acts to control the function of another type of cell.
Hormones
What are Hormones?
Compounds secreted into the bloodstream by one type of cell that acts to control the function of another type of cell
What are the types of Hormones related to increased hunger?
Hormones that increase hunger – Ghrelin, Endorphins, Neuropeptide-Y
What are the types of Hormones related to satiety or decreased hunger?
Hormones that cause satiety (decrease hunger) – Leptin, Serotonin, Cholecystokinin (CCK)
There are two key hormones in relation to hunger and satiety, what are they?
leptin and ghrelin
Leptin is produced by ______.
adipose tissue (fat cells)
The role of ______ is to alert the brain to turn off the hunger center in the brain and activate the satiety center when consuming a meal.
leptin
Ghrelin is produced by ______.
the stomach
______ travels to the brain and stimulates the hunger center as it deactivates the satiety center.
Ghrelin
True or Fales: Ideally, leptin and ghrelin work together to balance hunger and satiety.
True
What are the three major biochemical categories of food that the body needs in large amounts?
Carbohydrates, proteins, and lipids
True or False: Vitamins and minerals are also needed by the body but in much smaller amounts.
False: Vitamins and minerals are also needed by the body but in much LARGER amounts.
______ are classified as starches and sugars.
Carbohydrates
Milk and fruits, such as apples or peaches, contain ______.
sugar
Grains such as wheat and vegetables such as potatoes contain ______.
starches
Lipids can be divided into three categories what are they?
saturated fat, unsaturated fat, and cholesterol
Meat and dairy products, such as butter, contain ___1___ fats, while nuts and vegetable oils, such as olive oil, contain ___2___.
- saturated
- unsaturated fats
______ is made by our bodies but can also be ingested by eating animal products, such as meat (beef), cheese, and eggs (yolk).
Cholesterol
Proteins (which are made up of amino acids) can be categorized as ___1___ proteins or ___2___ proteins.
- complete
- Incomplete
Examples of ______proteins are meat, poultry, eggs, milk, dairy products, and soybeans.
complete
______ proteins are food such as grains, legumes, seeds, and nuts.
Incomplete
There are ___1___ amino acids called ___2___ amino acids required in an adult human diet (with ___3___ required in an infant’s diet).
- 9
- essential
- 10
They are called essential amino acids because ______.
the body is unable to make these amino acids
True or Fales: Incomplete proteins contain all nine essential amino acids but complete proteins do not.
False. COMPLETE proteins contain all nine essential amino acids but INCOMPLETE proteins do not.
______ are organic compounds that are not consumed in metabolic reaction but help enzymes carry out the metabolic reactions, which convert nutrients to materials needed by the body.
Vitamins
Vitamins can be classified as ___1___ soluble or ___2___ soluble.
- water
- Fat
______soluble vitamins are not able to be stored in the body and are excreted in urine.
Water
______soluble vitamins are stored in body fat.
Fat
True or False: Ingestion of excessive amounts of fat-soluble vitamins can be problematic.
True
True or False: Vitamins are not needed in the diet to maintain growth and good cellular health.
False. Vitamins ARE NEEDED in the diet to maintain growth and good cellular health.
______are inorganic compounds that, like vitamins, are not used as fuel in metabolic reactions but are combined with other nutrients to form necessary body substances.
Minerals
What are minerals?
Inorganic compounds that, like vitamins, are not used as fuel in metabolic reactions but are combined with other nutrients to form necessary body substances.
Humans need what seven minerals in their diets?
calcium
chloride
magnesium
phosphorus
potassium
sodium
sulfur
How many other minerals outside the 7 necessary ones are needed in trace amounts?
There are twelve other minerals needed in trace amounts.
True or False: Foods such as milk, some meats, legumes, and vegetables are the best sources of minerals.
True
