Digestive System lab10 Flashcards
which two parts of the digestive system can participate in the mechanical breakdown of food?
mouth and stomach
what is the stomachs role in mechanical breakdown?
churning and mixing action of the smooth muscle in the organ wall pummel the food and physically breaks it down into smaller pieces.
does chemical breakdown happen in the mouth and stomach if so, how?
yes.
mouth: salivary glands
stomach: pepsin, HCl, and acid
the pharynx contributes to the process of digestion by….
swallowing
the esophagus’ role in digestion is
delivering the food to the stomach
the small intestine is responsible for
chemical digestion, some mechanical digestion (segmentation) and absorption of nutrients
the large intestine is primarily involved in
the absorption of water and elimination of feces
what is the process by which food is propelled from the pharynx to the stomach?
peristalsis in esophagus
esophagus:
long muscular tube that delivers food from the pharynx to the stomach by the process of peristalsis.
peristalsis:
alternating waves of contraction and relaxation of muscles in the organ walls.
main effect: squeeze food along the tract
where does the majority of digestion and absorption occur in the gi tract?
the small intestines
secretions from the liver, gall bladder, and pancreas are delivered to which organ?
small intestines.
the duodenum (first part of small intestine)
food is tasted by the ______ in the tastebuds of the tongue
chemoreceptors
what are the three sets of tonsils that are a part of the lymphatic system
pharyngeal, palatine, and lingual
the pharynx is what kind of muscle
skeletal muscle
the pharynx is commonly called the throat and is divided into 3 regions
nasopharynx (posterior to nasal cavity)
oropharynx (posterior to oral cavity)
laryngopharynx (posterior to the larynx)
what are the four layers that make up the wall of the digestive tract? list in order starting with the layer closes to the food in the lumen of the GI tract
mucosa, submucosa, muscularis externa, serousa (adventitia)
the mucosa can be further divided into three layers….
epithelium, lamina propria, and muscularis mucosae
what is another name for serosa?
visceral peritoneum
which structures are part of the enteric nervous system?
submucosal plexus and myenteric plexus
what do the submucosal plexus and myenteric plexus contribute to the digestive process?
nerve fibers are located in the wall of the GI that communicate widely with one another to regulate and coordinate digestive system activity.
the enteric nervous system
over 100 million neurons that communicate widely throughout the digestive system to regulate digestions
‘gut brain’
the submucosal nerve plexus is located in the
submucosa
the myenteric nerve plexus is located
between the circular and longitudinal muscle layers of the muscularis externa.
which nervous plexus is located between the layers of the muscularis externa?
myenteric plexus
located between the muscle layers
the muscularis mucosae is part of which layer?
mucosa
segmentation:
contractions that lead to mixing- no forward mixing
peristalsis:
contractions that propel food forward in the tube
where does peristalsis happen?
muscularis externa
the outer tunic is called
serousa or adventita depending on whether the organ is wrapped by the peritonium
serosa is the term used for organs that…
are suspended in the mesentery (peritoneum)
serosa:
a connective tissue layer with an outer simple squamous epithelium called the mesothelium
adventitia belongs to organs that….
are not suspended in mesentery and instead are embedded in the body wall
adventitia:
a connective tissue layer that blends in with the rest of the connective tissue of the body wall
which layer of the alimentary canal or gastrointestinal tract can include either a stratified squamous or simple columnar epithelium?
mucosa
the mucosa contains two types of epethilium.
what are they and why?
the inner lining of the mucosa is composed of columnar epithelium for most of the GI tract,
but
areas that experience more abrasive forces the epithelium is stratified squamous
which part of the digestive tract have stratified squamous in the mucosa
esophagus, oral cavity, anus
which layer of the alimentary canal is responsible for segmentation and peristalsis
muscularis externa
what is the job of the esophagus?
to transmit food from the pharynx to the stomach
how does the esophagus transmit food bolus to the stomach?
peristalsis
which type of epithelium lines the esophagus?
stratified squamous
(the protective epithelium) because of undigested food that must pass through the lumen.
is the stratified squamous epithelium of the esophagus keratinized?
NO
what is true about the muscularis externa in the esophagus?
the muscularis externa has skeletal muscle in the upper regions of the esophagus, and smooth muscle in the lower regions.
an empty stomach has a volume of…
50ml
the stomach can hold about ______ of food when it is distended.
4L
when empty, the stomach collapses inward, throwing its mucosa and submucosa into large longitudinal folds called
rugae
what is the name of the large periotoneal fold that contains fat and hangs off the greater curvature of the stomach?
greater omentum
what is the name of the fold in the wall of the stomach that allow the stomach to expand more than 10 times its size in order to accommodate large meals?
rugae
what do parietal cells in the gastric glands secrete?
hydochloric acid and intrinsic factor
what do chief cells secrete?
pepsinogen: an inactive form of the enzyme pepsin
pepsinogen is converted to the active enzyme pepsin how?
the acidic environment of the stomach
what is produced by enteroendocrine cells?
hormones
where do enteroendocrine cells secrete hormones?
into the blood capillaries in the lamina propria of the mucosa.
the hormones travel through the bloodstream and influence the digestive process indirectly.
what layer of the stomach contains gastric pits that secret mucus, acid, and digestive enzymes?
mucosa
which of these structures is found in the stomach but nowhere else in the alimentary canal?
an oblique muscle layer
which area of the stomach empties into the small intestines?
pylorus.
via pyloric sphincter
what is the primary purpose of the small intestine?
chemical digestion and absorption of nutrients
which part of the small intestine receives secretions from the liver, gall bladder, and pancreas?
duodenum
secretions from the liver, gall bladder, and pancreas enter the small intestine (duodenum) through a duct controlled by
hepatopancreatic sphincter
sphincter of Oddi
which part of the small intestine delivers chyme to the large intestine?
ileum.
what is the name of the structure that anchors the small intestine to the posterior abdominal wall?
mesentery
what is the name of the permanent folds seen in the wall of the small intestine?
plicae circulares (circular folds)
what is the function of the plicae circulares
slow down the flow of chyme through the small intestine and increase the surface area in order to increase the efficiency of absorption in the small intestine.
what are the finger-like projections of mucosa in the small intestine that help increase the surface area for absorption?
villi
villi:
finger-like projections of mucosa that are covering the surface of the plicae circularis in the small intestine
the wall of the small intestine has 3 features that help to increase surface area for absorption. what are they? list from largest to smallest.
pilicae ciruclaris, villi, microvilli
what structural modification of the small intestine slows the movement of chyme through the lumen?
circular folds (plicae circularis)
which cells in the small intestine’s mucosa secrete mucus?
goblet cells
which of these bests describes a lacteal?
a lymphatic vessel designed to help introduce fats to the blood.
list the main sections of the large intestine in order
cecum, ascending colon, transverse colon, descending colon, sigmond colon, rectum, anal canal
what is the epithelium in most of the large intestine?
simple columnar (with goblet cells)
notable true characteristic features of the wall of the large intestine:
the outer layer of longitudinal smooth muscle is incomplete in the muscularis externa
(results in the formation to tenia coli)
teniae coli:
longitudinal strips of smooth muscle that are seen on the outer surface of the large intestine
a result of incomplete outer layer of the muscularis externa
what are the 3 longitudinal bands of smooth muscle that can be seen from the external surface of the large intestine?
teniae coli
what is the primary physiological function of the large intestine?
water absorption and feces elimination
which sphincter prevents backwards flow (reflux) from the large intestine into the small intestine?
ileocecal sphincter
which sphincter controls the flow of chyme from the stomach to the small intestines?
pyloric sphincter
which sphincter prevents reflux of gastric contents into the esophagus?
lower esophageal sphincter (LES)
defecation requires
relaxation of both anal sphincters
what is the largest lobe of the liver?
the right lobe
