The Digestive System
How many pairs of major salivary glands are there?
3-These include the parotid, sublingual and submandibular.
If the glands of the cardiac region and the pylorus were damaged, what would you expect to happen?
A decrease in mucus production. The cells of the cardia region and pylorus are primarily mucus-secreting cells.
One way that the GI tract maximizes its function is by:
Adjusting the secretions based on the nutrients ingested. For example, the types of enzymes produced will vary with the intake.
The main digestive enzyme secreted in saliva is
Amylase is secreted in high concentration in the saliva and is involved in starch digestion
Saliva can contain all of the following :
Antibodies Mucus Amylase Pepsinogen is an enzyme secreted in the stomach and not as part of saliva.
What are the regions of the colon, in order, from proximal to distal?
Ascending colon, right colic flexure, transverse colon, left colic flexure, descending colon, sigmoid colon.
Which molecules listed below would best be able to digest the oil in your salad dressing or the butter on your bread?
C. Bile from the gallbladder. D. Lipase from the pancreas. Lipids are digested through a process of emulsification and then chemical digestion.
The enzyme amylase chemically digests
Carbohydrates are digested by amylases.
If a person was not secreting saliva, what would their main problem be?
Difficulty swallowing.
Shortest and least mobile, receives substances from stomach, liver and pancreas:
Duodenum-Food enters through pyloric sphincter, while bile and pancreatic juice enters through hepatopancreatic sphincter.
In which segment of the small intestine does bile enter?
Duodenum-The hepatopancreatic sphincter opens into the duodenum.
One of the byproducts of bacterial digestion in the large intestine is:
Flatus is a mixture of gases produced via anaerobic respiration of the bacterial cells.
If a person has their gallbladder removed, they may want to eat smaller amounts of which of the following foods to make sure everything is properly digested and absorbed?
French fries-These are fried in fats (a type of lipid), and a lot of fries can contain a lot of fat, which may not be readily absorbed without a large influx of bile. Those without gallbladders don't receive large influxes of bile into their small intestine.
Before you burp, gas associated with swallowing and digestion will first accumulate in what superior portion of the stomach?
Fundus-The dome of the fundus allows gas to accumulate above the chyme that is mixing in the body of the stomach.
In which section of the GI tract is the most vitamin B12 absorbed?
Ileum=The distal part of the small intestine is responsible for absorbing vitamin B12.
The two major functions of the large intestine are water absorption and defecation. As the chyme moves toward the rectum, water and electrolytes are absorbed and feces is formed. What is found in feces?
Indigestible food material such as cellulose. Dead cells Mucus Bacteria Feces contain much more than just indigestible food.
Mixing waves
Mixing waves are a gentle type of peristalsis that soften and moisten food. They also combine food with gastric juice and create chyme. Initial gentle mixing waves are followed by more intense waves that break down food into smaller pieces and further mix with digestive juice, starting at the body of the stomach and increasing in force as they reach the pylorus.
Which of the following is absorbed in the small intestine?
Monosaccharides Amino acids Lipids
Chicken has a high protein content. Which of the following enzymes help to digest the chicken?
Pepsin in the stomach. Proteases from the pancrease. Brush border peptidases of the small intestine Proteins are digested by many different enzymes from various sources.
Muscularis externa
Peristalsis Defecation reflex Contractions of circular and longitudinal muscles propel contents along length of colon; Contractions in sigmoid colon and rectum eliminate feces.
Coordinated smooth muscle contractions that move substances through the GI tract is called:
Peristalsis-Peristalsis is an involuntary, well controlled migration contraction of smooth muscle.
Chemical digestion mainly occurs
The lumen is where food is mechanically and chemically digested.
How do mixing waves differ from normal peristalsis?
They do not always move food in one direction. Normal peristalsis moves food in one direction. Mixing waves in the stomach can move food "back and forth".
The main benefit of the villi and microvilli are that:
They increase surface area for absorption. They greatly increase the surface area, benefitting absorption.
Which of the following statements is true about the location of the hard and soft palate in the mouth?
They separate the nasal cavity from the oral cavity. This allows us to breathe while chewing food.
The hemorrhoidal veins do contain valves. How does this increase their risk for becoming distended?
This increases their colloid osmotic pressure, drawing fluid into the vein. Valves increase the resistance to flow, decreasing the hydrostatic pressure in the vessels. Lack of veins increases the hydrostatic pressure. Valves normally limit the flow of blood into the veins. Lack of valves increases the flow of blood into the veins.
Which of the following does not have to be chemically digested prior to being absorbed in the small intestine?
Vitamins are ingested in absorbable form.
A frenulum is:
a fold of tissue that acts as an attachment-Associated with the mouth, there is a labial frenulum and lingual frenulum.
The mouth is lined with:
a mucous membrane-This membrane produces mucus to lubricate food for swallowing.
The cheeks, tongue, hard palate, and soft palate frame the mouth, also called
the oral cavity or buccal cavity. The mouth is involved in both mechanical and chemical digestion. Mechanical digestion consists of mastication (chewing), in which the tongue manipulates food, the teeth grind it, and saliva mixes with it. Mastication turns food into an easy-to-swallow bolus and breaks the food into smaller pieces so that there is more contact area for digestive enzymes.
Voluntary phase occurs when the bolus of food is pushed by the tongue to the posterior part of the mouth.
yes -This is also called the oral phase or buccal phase.
Pharyngeal phase occurs when muscles move the bolus through the oropharynx, laryngopharynx and through the upper esophageal sphincter.
yes- This is one of the two involuntary phases of swallowing.
Bile contributes to the absorption of: Fat-soluble vitamins::
yes-Fat-soluble vitamins are absorbed along with other lipids and aided by bile.
Bile contributes to the absorption of: Lipids:
yes-Large lipids need to be "emulsified" by bile before they can be digested and absorbed.
Breakdown of food into smaller pieces.
yes-The stomach is responsible for some mechanical digestion.
How many sphincters are located in the anal canal?
2-There is an internal anal sphincter and an external anal sphincter.
The colon is:
A portion of the large intestine. The large intestine includes the cecum, colon, rectum and anus.
Which of the following would be modifications of the lining of the GI tract that aids in the absorption of nutrients?
A. Projections in the epithelium, called villi, provide a large absorptive surface. B. Projections in the plasma membrane of the epithelial cells, called microvilli, provide a large surface area for absorption.
Different organs of the digestive system secrete substances into the lumen of the gastrointestinal tract. These secretions have which of the following functions?
A. Secretions can assist with the movement of food from one organ to another. B. Secretions can assist with the chemical digestions of food.
Which of the following would describe best the function of the small intestine?
A. With the aid of secretions from the liver and pancreas, the small intestine completes the chemical digestion that began in the mouth and continued in the stomach. B. The small intestine is the primary site of nutrient absorption. C. The peristaltic waves propel indigestible materials into the large intestine
Why would the last section of the small intestine (ileum) have greatest concentration of lymphatic tissue for immune response to bacteria?
Bacteria live in the large intestine and could enter the ileum through the ileocecal sphincter. The chyme entering the duodenum has just come from the acidic environment of the stomach which will kill most bacteria.
Lumen
Bacterial degradation of chyme components. Bacteria provide limited break down undigested nutrients, preparing them for absorption. Bacteria also synthesize vitamin K and some B vitamins.
The main digestive function of the liver is to:
Bile contributes to fat (lipid) digestion and absorption.
If someone can't make and secrete bile, the main waste product that would build up in the body would be:
Bilirubin-This breakdown product of hemoglobin would accumulate in the body, causing the person to be jaundiced (have a yellow tint).
The pancreatic duct joins the common bile duct just before it empties into the duodenum in a structure called the hepatopancreatic ampulla. If the ampulla becomes blocked by a large gallstone, what problems might occur?
Both the flow of bile and pancreatic juice could be greatly reduced. These would contribute to decreased chemical digestion of most macromolecules, especially lipids, which require bile to break up fat globules as well as absorb them.
Swallowing involves:
Both voluntary and involuntary muscle contractions. The first phase of swallowing is voluntarily controlled by skeletal muscles such as those in the tongue. But then there is an involuntary phase.
Milk has a small, two-sugar carbohydrates called lactose that is still too large to be absorbed. In the small intestine, an enzyme called lactase is present that can make the final split of the two-sugar unit into the single sugars. This enzyme comes from the:
Brush border of the small intestine. This is where the final steps of chemical digestion take place for some of the carbohydrates.
The entirety of the structures that frame the mouth are sometimes called the:
Buccal cavity-. Buccal can be used in reference to the mouth or cheeks.
Bile contributes to the absorption of: Carbohydrates:
Carbohydrates do not need to be "emulsified" for absorption.
The four main regions of the large intestine are:
Cecum, colon, rectum and anus. These are the four regions of the large intestine, in order.
The hormone that is most responsible for the amount of bile that enters the duodenum is:
Cholecystokinin (CCK) is released by intestinal cells in response to fat intake.
Gallstones are composed of:
Concentrated bile salts.-Bile salts can crystallize when they become very concentrated. Bilirubin and calcium carbonate can also contribute to crystal/stone growth.
Premolars and molars have cusps on them, instead of being "flat" on top. This is beneficial because
Cusps provide a better mechanism for tearing foods as we grind it between the teeth.
The bile duct is formed by the joining of the:
Cystic duct and common hepatic duct-The bile ducts starts at the point where these two come together.
Soon after a meal the gallbladder contracts and pushes bile into the cystic duct and then into the common bile duct. The bile then flows from the common bile duct into the:
Duodenum-The small intestine is where bile enters.
The teeth wear very slowly because they are covered in:
Enamel is highly mineralized and very hard.
Hormones released from digestive system organs that help regulate digestive function are called:
Enteric hormones-Enteric means "of or relating to the intestines."
The wall of the gastrointestinal tract always contains at least two separate layers of:
Epithelial tissue composes both the inner layer (mucosa) and outer layer (serosa). It is common for epithelium to line both the inner and outer walls of an organ.
The innermost layer of organs of the alimentary canal is composed mainly of:
Epithelial tissue-The mucosa is an epithelial layer.
Which colonic movement would best support water absorption?
Haustral contractions mix the contents, which exposes more of the chyme to the wall, supporting water absorption.
The voluntary phase of deglutition is also called the oral phase or buccal phase
In this phase, swallowing is set in motion when the tongue moves upward and backward against the palate, pushing the bolus to the back of the oral cavity and into the oropharynx. At this point, the two involuntary phases of swallowing begin
The liver is located:
Inferior to the diaphragm. The liver is located "below" the diaphragm.
The gallbladder is located:
Inferior to the liver. It hangs off of the bottom of the liver.
A unique feature of peristalsis in the stomach is:
It will move food "back and forth" instead of just in one direction. These mixing waves ensure that food is fully mixed with acid, mucus and digestive enzymes.
Longest, for increased transit time with continued digestion and absorption of most of the organic compounds:
Jejunum-In addition to length, villi and microvilli also increase surface area for efficient absorption while chyme is in the small intestine.
Mumps is a viral infection that most commonly affects the parotid glands. Where would the physician most easily palpate (feel with touch) the swollen glands associated with mumps?
Just anterior and inferior to the ears. The parotid glands are located near the earlobes.
The esophagus connects the:
Laryngopharynx to the stomach. The laryngopharynx is the inferior region of the pharynx. The esophagus connects it with the stomach.
Which of the following is a digestive enzyme?
Lipase Amylase Pepsin
Along the length of the GI tract there are sphincters that would best be describe as:
Localized constrictions of the smooth muscle layer. Sphincters are not structurally different from the neighboring area of the structure they are found in. But they are functionally different, maintaining contraction of the smooth muscle until passage through the sphincter is beneficial.
The urge to defecate is driven by:
Mass movements are designed to force contents into the rectum, which initiates an urge to defecate.
The defecation reflex is initiated by:
Mass movements-These movements push feces into the rectum, stretching it, and initiating the reflex.
Emptying of the stomach is best described by which of the following statements?
Meals high in carbohydrates empty more quickly than those high in fats. Carbohydrates digest more easily in the small intestine than fats do.
Of the roles of the digestive system organs, which of the following best describes the role of teeth in the digestive process?
Mechanical and/or chemical digestion-The teeth mechanically grind food, increasing the surface area of the food pieces.
Pasta is mostly carbohydrates in the form of starch. Starch is a long chain of single sugars (glucose) that is too large to be absorbed. Breakdown of this long chain into smaller units (mostly a two glucose unit called maltose) begins in the _____ because of the digestive enzyme ______.
Mouth; salivary amylase Amylases are enzymes that break down long chains of sugars.
Which of the following is secreted in the stomach?
Mucus Acid Pepsin
Mucosa
Mucus secretion Absorption Lubricates colon and protects mucosa. Absorbs water, solidifies feces, and helps maintain water balance in body; absorbed solutes include ions and certain vitamins.
Gastric secretions of the stomach include which of the following?
Mucus, hydrochloric acid, gastric lipase, pepsin and intrinsic factor These are the secretions of the stomach.
The main secretion of the large intestine is:
Mucus-The large intestine secretes mucus to aid in the movement of chyme through the intestine.
The major secretion of the large intestine is:
Mucus-There is a high density of mucous glands in the large intestine.
Which layer changes it thickness the most in various organs of the alimentary canal?
Muscularis-In some regions of the alimentary canal, there are three layers of smooth muscle within the muscularis layer, while in other regions there are two.
Which of the following statements describes the location of the tonsils in the mouth?
On, and just lateral to, the root of the tongue. The lingual tonsils are located on the base of the tongue while the palatine tonsils are just lateral to the lingual tonsils on the wall of the oral cavity.
The structure(s) that form the roof of the mouth is/are the:
Palate-The roof of the mouth is formed by the hard and soft palate.
Which of the following is an accessory digestive organ?
Pancreas Liver Gallbladder The main role of the spleen is the breakdown of old red blood cells and to contribute to immune surveillance of the blood.
Which of the following cell types secrete acid?
Parietal-These cells are responsible for the low pH of the stomach.
Which of the following is a salivary gland?
Parotid Sublingual Submandibular
The process of moving the food or chyme bolus in one direction along the length of the GI tract is mainly carried out by:
Peristalsis is the process by which a segment of the "tube" behind a bolus will contract while the region in front of the bolus will relax. This repeats along the length of a segment in coordinated fashion.
The entry of food into the esophagus marks the beginning of the esophageal phase of deglutition
Peristalsis propels the bolus through the esophagus and toward the stomach. The circular muscle layer of the muscularis immediately superior to the bolus contracts, pinching the esophageal wall, forcing the bolus forward. At the same time, the longitudinal muscle layer of the muscularis inferior to the bolus also contracts, shortening this inferior area and pushing out its walls to receive the bolus. Waves of contractions keep moving the food toward the stomach. When the bolus nears the stomach, relaxation of the lower esophageal sphincter allows the bolus to pass into the stomach. During the esophageal phase, esophageal glands secrete mucus that lubricates the bolus and minimizes friction. Peristalsis is completely involuntary even though there is skeletal muscle in the first 2/3 of the esophagus.
The population of trillions of bacteria in the large intestine is called the intestinal flora. Which of the following is an effect of these bacteria?
Produce vitamin K Produce gases Prevent infections
The Digestion of Proteins
Proteases are a family of enzymes that digest proteins. Protein digestion starts in the stomach, where the enzyme pepsin breaks down proteins (long, complex amino acid chains) into peptides (short, linear amino acid chains). In the small intestine, the enzymes trypsin and chymotrypsin also hydrolyze (cleave with a hydrolysis reaction) proteins and polypeptides into smaller peptides
Which of the following is a sphincter found along the gastrointestinal tract?
Pyloric Ileocecal Esophageal There is an anal sphincter but not a rectal sphincter.
The region of the stomach that connects with the small intestine is the:
Pylorus-It is named because it contains the pyloric sphincter (valve) that separates the stomach from the small intestine.
The folds that allow the stomach to expand after a large meal are called:
Rugae are folds of the mucosa and submucosa.
Which of the following statements best describes the type of motility in the small intestine that best promotes absorption?
Segmentation waves mix chyme. The mixing action of segmentation waves brings food into contact with the intestinal wall, which promotes absorption.
The small intestine brings nutrients into contact with the wall through the process of:
Segmentation-This "mixes" the substances in the small intestine and brings them into contact with the intestinal wall.
Which of the following digestive system structures is most inferior?
Small Intestine - Inferior refers to "toward the feet," which would best describe the small intestine on this list.
Which of the following organs would be best adapted to absorption of nutrients?
Small intestine because it has large surface created by villi and microvilli. The large surface area is beneficial to absorption. This is also seen in the lungs where a large surface area contributes to gas exchange.
Sphincters
Sphincters are typically contracted and relax only to allow food to move from one organ to the next. The majority of sphincters along the length of the GI tract are involuntary smooth muscle structures. The esophageal sphincter helps separate the esophagus from the stomach to maintain linear movement of the food bolus and to protect from acidic chemicals of the stomach moving backward (i.e. in a retrograde direction) into the esophagus. The pyloric sphincter separates the stomach from the small intestine; again there is a physical separation for compartmentalization and to maintain directionalized movement.
During swallowing (deglutition):
Stimulation of receptors in the oropharynx sends impulses to the deglutition center in the medulla oblongata causing the uvula and soft palate to close off the nasopharynx.
"Heartburn" occurs when:
Stomach acid passes through the lower esophageal sphincter and damages the esophagus. If the lower esophageal sphincter does not stay closed (except when swallowing), stomach acid can reflux into the esophagus, creating a painful, burning sensation.
Which of the following would describe best the function of the stomach?
Storage of food with some mechanical and chemical digestion of food with a limited amount of absorption.
The layer of the alimentary canal that contains the majority of blood and lymphatic vessels is the:
Submucosa-This layer has a lot of blood vessels and lymphatic vessels for the absorption of nutrients. RETURN TO COURSE
If a person was unable to produce digestive enzymes, in order to adequately absorb nutrients, they would need to?
Supplement with digestive enzymes. Digestive enzymes are necessary in order to convert food to absorbable components.
The Digestion of Carbohydrates
The break down of carbohydrates is facilitated by the enzyme amylase. The mouth is where the chemical digestion of starch begins. Salivary amylase acts to break down the polysaccharide starch (complex sugars) smaller saccharides that are usually 2 or 3 saccharides (sugars) long.
Which portion of the large intestine is located directly inferior to the ileocecal valve?
The cecum is a small sack like region that is inferior to the ileocecal valve.
The small intestine is divided into three sections.
The duodenum receives the stomach contents, pancreatic juice and bile and participates in chemical digestion. The jejunum is the next portion (3.5 - 5.5 ft or 110-170 cm) of the small intestine and is responsible for the absorption of a majority of nutrients. In the last section of the small intestine, the ileum, vitamin B12 and bile salts are absorbed as well as materials not absorbed by the jejunum.
The Esophagus
The esophagus is a collapsible tube located posterior to the trachea. This muscular tube is about 10 inches long that runs a mainly straight route through the thorax. To enter the abdomen, the esophagus goes through the diaphragm (the muscle that separates the thoracic and abdominal cavities) at an opening called the esophageal hiatus, where it then joins the stomach.
Which of the following is properly matched with its description?
The jejunum is the second portion of the small intestine and responsible for the majority of absorption. The ileum is the last part of the small intestine and contains aggregated lymphatic follicles. All of these are properly matched.
Which of the following enzymes is/are secreted into the large intestine?
The large intestine does not actively secrete any digestive enzymes.
The large intestine
The large intestine runs from the cecum, where it attaches to the ileum, to the anus. It borders the small intestine on three sides. Despite its being around half as long as the small intestine - 4.9 feet versus 10 feet (1.5 - 3 meters) - it is called the large intestine because it is more than twice the diameter of the small intestine, 2.5 inches versus one inch (6 cm versus 2.5 cm). The large intestine is subdivided into four main regions: cecum, colon, rectum, and anus. The ileocecal valve, located at the opening between the ileum in the small intestine and the large intestine, controls the flow of chyme from the small to the large intestine.
Food is prevented from entering the trachea by:
The larynx moving superiorly. The larynx moves upward to meet the epiglottis. This movement closes off the glottis.
Absorption involves moving substances from:
The lumen to the apical side of the cell. Nutrients start in the lumen and move to the apical side of the cell when absorbed.
The Mucosa
The mucosa is a mucous membrane that makes up the inner lining of the GI tract. It has three layers: the epithelium, made of closely packed cells that are in direct contact with the foodstuffs that enter the GI tract; a layer of connective tissue that supports the epithelial cells; and a thin smooth muscle layer
The Muscularis
The muscularis is a smooth muscle layer, which contracts involuntarily but in a coordinated manner to mix food with digestive juices and move it along the GI tract. Complementary muscles in longitudinal (along the length of the tract) and circular layers create peristalsis, the wave-like muscular movements to move food from the esophagus to the anus.
Under normal conditions, food will not enter the:
The nasopharynx is superior to where food enters the pharynx and does not serve as a passageway for food.
Pancreas
The pancreas produces pancreatic juice and the liver produces bile. The regions of the pancreas include the head, body, and tail. The head is next to the duodenum. The body lies behind the stomach. The tail is in contact with the spleen.
Although a peanut is normally a digestible food, which of the following statements best describes the reason why swallowing a peanut whole will result in a whole peanut being defecated?
The peanut has too small a surface area for the enzymes to digest it and chewing increases the surface area. Without increasing the surface area of the peanut, it will not be chemically digested before being expelled.
The Serosa
The serosa are the outermost layer of the intestine that covers the parts of the GI tract that is exposed to the abdominal cavity. This serous membrane is made up of an inner connective tissue layer and an outer layer of simple squamous epithelium.
The small intestine
The small intestine is a convoluted tube that begins just distal to the pyloric sphincter of the stomach and then loops through the central and inferior region of the abdomen before ending at the ileocecal valve, where it merges with the large intestine. The small intestine is the primary digestive organ in the body. Not only is it the part of the GI tract where digestion is completed, it is also where the majority of absorption occurs.
The Submucosa
The submucosa binds the mucosal layer to the muscularis layer. It is composed of areolar connective tissue and includes blood and lymphatic vessels, which transport absorbed molecules.
What is the name of the cone shaped structure that hangs from the soft palate?
The uvula provides a barrier to food in the oral cavity entering the oropharynx.
The Digestion of Lipids
Triglycerides and their breakdown products do not dissolve in water. Before they can be digested in the watery environment of the small intestine, large lipid globules must be separated into smaller lipid globules, a process called emulsification. This process is greatly aided by bile salts. The bile salts facilitate emulsification of large lipid globules into small lipid globules of about 1 µm in diameter. This emulsification greatly increases the surface area to volume ratio of fat globules, which allows pancreatic lipase to access more lipid molecules. The three lipases involved in the digestion of triglycerides are lingual lipase (in the saliva), gastric lipase, and pancreatic lipase.
What are the phases of deglutition?
Voluntary, pharyngeal and esophageal phases. There are 3 phases of swallowing.
Which of the following statements is true regarding the small intestine?
With the aid of secretions from the liver and pancreas, the small intestine completes the chemical digestion that began in the mouth and continued in the stomach. The small intestine is the primary site of nutrient absorption. The peristaltic waves propel indigestible materials into the large intestine.
The lips,
also called labia ("fleshy borders"), encircle the opening of the mouth. Their outer covering is skin, and their inner lining is mucous membrane. The labial frenulum is a midline fold of mucous membrane that attaches the inner surface of each lip to the gum. The lingual frenulum attaches the tongue to the floor of the mouth
Enzymes
are biological catalysts that speed up chemical reactions. Specialized enzymes are a critical part of the digestive process, where they cleave the larger macromolecules found in food into fragments small enough that they can be absorbed and distributed throughout the body. There are three main categories of enzymes used to breakdown the ingested macromolecules, with each category having a slightly different distribution within the GI tract.
The teeth, or dentes,
are secured in sockets of the alveolar processes of the maxillae and mandible. Gingivae (gums; singular gingiva) cover the alveolar processes. Lining each socket is a periodontal ligament, a dense fibrous connective tissue that secures the teeth in place. The teeth are covered by enamel, which is the hardest substance in the body. Enamel helps prevent teeth from being worn down when we chew, and it helps keep out acids that could easily dissolve the interior of a tooth.
The largest region of the stomach is the:
body-This is the large middle portion.
The uvula (Latin for 'little grape')
is a cone-shaped muscular process that hangs from the end of the soft palate. It plays a role in speech and articulation of words. It also plays a small role in preventing foods and liquids from entering the nasal cavity.
The pharynx (throat)
is a funnel-shaped tube that runs from the internal nostrils to the esophagus. The pharynx has three subdivisions: the nasopharynx, the oropharynx, and the laryngopharynx. The nasopharynx acts as a passageway for air during ventilation, while the other two subdivisions participate as conduits for both breathing and swallowing. Superiorly, the oropharynx is connected with the nasopharynx, inferiorly with the laryngopharynx, and anteriorly with the mouth.
The tongue
is a muscular structure that manipulates food, provides sensory information and participates in speech. It is sensitive enough to detect a fragment of bone, or a piece of hair, in food. The surface of the tongue is covered in stratified squamous epithelium interspersed with taste buds and lingual glands that secrete a portion of the saliva (including mucus).
Mastication, or chewing,
is a process that uses the teeth, in coordination with the tongue and other muscle of the mouth, to initiate mechanical digestion. The main roles of mastication include greatly increasing the surface area of the ingested food (which benefits chemical digestion), adding mucus and saliva to initiate chemical digestion and soften the food for swallowing, and generating a bolus of suitable size for swallowing. Mastication occurs via reflexes (consider the lack of thought needed when chewing gum) that alternately relax and contract the muscles of mastication, along with the tongue keeping the food placed between the upper and lower teeth.
The palate
is a septum that separates the oral cavity and nasal cavity. Anatomically, a septum (plural, septa) is a wall within a single organ or cavity that separates the space into distinct sides. For example, the nasal septum divides the nostrils. This is separating two distinct cavities.
The cardia
is a small area surrounding the cardiac orifice through which food from the esophagus enters the stomach. Lying beneath the diaphragm, superior and to the left of the cardia region, is the dome-shaped fundus, which functions as a temporary storage center for food. I
Digestion
is accomplished both mechanically and chemically. Mechanical digestion physically breaks food into smaller pieces, increasing surface area for more efficient chemical digestion. Chemical digestion breaks the larger macromolecules in food down into their chemical building blocks (i.e. their monomers), which can then be absorbed through the intestinal wall for distribution to the body's tissues.
The stomach
is an organ of the GI tract that acts as an expansive container between the esophagus and the first part of the small intestine (the duodenum). Between these fixed upper and lower ends, the walls of the stomach can expand to accommodate our food intake.
The stomach
is an organ that specializes in receiving food from the esophagus, storing it temporarily, and performing chemical digestion and mechanical mixing. Although it has the same four layers as the rest of the GI tract, it has some specific adaptations to the mucosa and muscularis externa layers that contribute to its functions. These include an extra layer of muscle in the muscularis externa and a variety of cells that secrete into the gastric glands.
Deglutition
is another word for swallowing - the movement of food from the mouth and into the stomach. The entire process takes about four to eight seconds for solid or semisolid food and about one second for very soft food and liquids. Deglutition involves the mouth, pharynx, and esophagus. It is facilitated by the secretion of mucus and saliva. There are three stages in deglutition: the voluntary phase, the pharyngeal phase, and the esophageal phase.
The convex lateral surface of the stomach
is called the greater curvature; the concave medial border is the lesser curvature. The stomach is held in place by two "sheets" of serous tissue called omenta (singular: omentum). The omenta are folds of the peritoneum, which is the connective tissue lining that encloses the abdominal cavity. The lesser omentum extends from the liver to the lesser curvature. The greater omentum runs from the greater curvature to the posterior abdominal wall.
The digestive system
is generally divided into two main categories: organs of the alimentary canal (aliment = "nourish") and accessory digestive organs. The alimentary canal, also called the gastrointestinal (GI) tract or gut, is a continuous muscular tube that runs from the mouth to the anus.
The liver
is the largest internal organ in the body and plays major roles in digestion, nutrient processing, detoxification of the blood and production of blood proteins. In an adult, the reddish-brown liver weighs about 3 pounds (1.4 kg). This wedge-shaped organ lies inferior to the diaphragm in the right upper quadrant of the abdominal cavity. The liver is almost completely surrounded by the rib cage, which offers it some protection. The main digestive function of the liver is to produce bile.
The large intestine
is the terminal part of the gastrointestinal tract. The primary digestive function of this organ is to finish absorption, produce some vitamins, form feces, resorb water secreted into earlier portions of the alimentary canal and eliminate feces from the body.
The pyloric antrum
is the wider, more superior portion of the pylorus that connects to the body of the stomach. The pyloric antrum narrows into a region called the pyloric canal, which leads into the duodenum.
The organ that generates bile for fat absorption is the
liver-The liver makes bile, which is then stored in the gallbladder.
Esophageal phase occurs when circular muscle inferior to the bolus contract as circular muscle superior to the bolus relax. At the same time, longitudinal muscles contract moving the bolus along the esophagus.
no-If the actions were as described, the bolus would move toward the pharynx instead of toward the stomach
Gastric emptying by forcing chyme through the esophageal sphincter.
no-Motility stimulates gastric emptying, but not through the esophageal sphincter.
Bile contributes to the absorption of: Proteins:
no-Proteins do not need to be "emulsified" for absorption.
Secretion of stomach acid.
no-Stomach acid is not secreted because of motility.
The bile
produced in the liver leaves the liver through the left and right hepatic ducts, which merge into the common hepatic duct. Bile is a liquid that does not contain any digestive enzymes but does contain substances used to digest and absorb lipids, including cholesterol derived bile salts and phospholipids
Most of the ingested water is absorbed in the
small intestine
In the pharyngeal phase
stimulation of receptors in the oropharynx sends impulses to the deglutition center (a collection of neurons that controls swallowing) in the medulla oblongata. Impulses are then sent back to the uvula and soft palate, provoking them to move upward to close off the nasopharynx. Sequential contractions of the pharyngeal constrictor muscles move the bolus through the oropharynx and laryngopharynx. Relaxation of the upper esophageal sphincter then allows food to enter the esophagus.
Gallbladder
the gallbladder stores and concentrates the bile produced by the liver and releases it in response to the hormone cholecystokinin (CCK). It lies in a shallow area on the posterior surface of the right lobe of the liver. The gallbladder appears green because of the bile it contains. In some people, the cholesterol salts in the bile precipitate into crystals in the gallbladder. These crystals might grow into larger stones. Gallbladder removal because of gallstone formation is common
The anterior part of the roof of the mouth is called
the hard palate
The digestive system has three accessory organs
the liver, gallbladder, and pancreas. The liver produces bile for fat emulsification and absorption of fats and fat soluble vitamins. It is also involved in blood detoxification by removing drugs and other chemicals. The gallbladder stores and concentrates the bile produced by the liver. The pancreas produces digestive enzymes and bicarbonate that are secreted into the small intestine. The bicarbonate is a base that neutralizes the acidic chyme entering the small intestine.
Which of the following result from motility of the stomach? Mixing of gastric juice and creation of chyme.
yes-This benefits chemical digestion.
