unit 8 digestive
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what does the alimentary canalconsist of?
- known as the GI tract,consists of
what are the accessory organs?
- salivary glands
what is ingestion?
food is taken in to the mouth
what is propulsion?
invovlves swallowing(voluntary),and peristalis(involuntary):
what is peristalsis?
progressive waves ofcontraction that move food along the alimentary canal
what is mechanical digestion?
chewing(teeth) and churning(stomach)of food.
what is segmentation?
involves segments of the sm. intestine contracting and relaxing; this mixes food with digestive juices and increases absorption effiency.
what is chemical digestion?
breakdown of carbs,proteins, and lipids
what is absorption?
transport ofmaterial from the lumen of the alimantary canal to the blood,lymph capillaries.
what is defecation?
removal of undigestible material from the body as feces
what are the:
- 1. covers the digestive organs
- 2.a slit-like potential space
- 3.lines the abdominal wall
what are mesenteries?
double layer of peritoneum;hold organs in place;fat storage
what is the dorsal mesenteries?
and ventral mesenteries?
- 1.most meseteries including the greater omentum
- 2.falciform "ligament"(liver) and lesser omentum(liver,stomach and duodenum)
what are retroperitoneal organs?
- digestive organs not found in the pelvic or abdominal cavity.but are located just on the outside behind the parietal peritoneum.
- 1.fuse to teh dorsal abd. wall during development
- 2.lose their mesentary
ex: parts of the esophagus,duodenum,colon,and rectum. kidneys
what is the mucosa?
- 1.the innermost layer with 3 sublayers
- 2.absorbs nutrients and secretes mucus
- 3.nourishes the lining epithelium and absorbs digested nutrients. contains lymph.tissue for protection.
- 4. thin layer of smooth muscle
what is the submucosa?
contains major blood vessles, lymph. vessles and nerve fibers
what is the muscularis externa?
inner circular layer?
- 1.contains 2 layers of smooth muscle that work 2gether to cause peristalis and segmentation.
- 2.muscle fibers that orient around the circumference of the canal "squeezes" the gut tube
- 3.muscle fibers orient along the length of the canal;shortens the gut tube
what is the serosa?
composed of the viseral peritoneum
what is the oral cavity(mouth) composed of and why?
composed of a thick non keratinized stratified squamous epithelium to help deal with friction/"wear and tear" from digested food.
what is the oral orifice?
what si the vestibule?
- 1.anterior opening
- 2.between teeth and cheeks (and lips)
what muscles are the following formed from?
- 1.lips;formed from the orbicularis oris muscle
- 2.formed from the buccinator muscle
what parts make up the palate?
roof of themouth, hard palate,soft palate,uvula, and palatine tonsils
what si the tongue and what does it contain?
it is a muscle and contains the lingual tonsils and papillae
what is filiform papillae?
"roughen"toungue;provides friction for manipulating food
what papillae contain taste buds?
what do the salivary glands produce?
- saliva(a combo of H20 ions,mucus, and enzymes)
- amylase which begins the digestion of starch in the mouth.
what do ther intrinsic salivary glands do?and where are they found?
- they keep the mouth moist at all times
- found in the tongue palate lips and cheeks
what do the extrinsic salivary glands do?
- they secrete saliva during eating or the antispation of a meal
- they include the parotid,submandibular and sublingual glands
what are mucous cells?
sublingual glands;produce mucus;sublingual glands contain only serous cells
where are the teeth located?
they lie in alveolar sockets of the mandible and maxillary bones
what are the deciduous(primary) teeth?
20 include the incisors,canines(cuspids or eyeteeth)and molars
what are the permanent teeth?
32 include incisors, canines,premolars(bicuspids) molars(including wisdom teeth)
what is gingivae?
- above the gums
- below the gums
what is enamel?
99% mineralized with hydroxyapatite; hardest substance in the body
what is dentin?
like bone but harder and lacking blood vessels;not as hard as enamel.
what is the pulp cavity?
contains "pulp" and the tooths blood vesels and nerves
what si the peridontal ligament?
connects the cementum of the tooth to the alveolar bone;composed of collagen fibers
what is the purpose of the oropharynx and laryngopharynx?
what are they composed of?
- passageway for food, fluids and air
- composed of non keratinized,stratified squamous, epitheluium
what does the epiglottis do?
it helpsto block the opening to the larynx and assures that food continues down the esophagus.
what are the properties of the esophagus?
- muscular tube that propelsfood to the stomach
- lies directly posterior to the trachea
- passes through the diaphragm,turns left and connects to teh stomach at the cardia.
why does the esophagus stomach junction narrow at the cardia?
to helpl limit regurgitation of the stomach acid back into the esophagus
what are the functions of the stomach?
- storageof food(for about 4 hours)
- churning of food to turn it into a paste called chyme
- it secretes pepsinogen that converts to pepsin in an acidic envirornment to begin protein digestion
- secretion of hydrochloric acid(HC1)
- very littledigestion occurs in the stomach. mostly in the sm. intestine
what is the stomach composed of?
linner lining composed of simple columnar epithelium
what is rugae?
non permanent fols that allow the stomach to stretch
what si the pyloric sphincter?
controls the passage of chyme into the duodenum of the small intestine
what are gastric glands?and what types ofcells do they contain?
- are invaginations that increase the surface area in the stomach
- mucous cells: secrete mucus
- parietal cells:secrete hydrochloric acid
- chief cells: secrets pepsinogen
- enteroendocrine cells: influence digestive system target organs
what does gastrin do?
regualtesstomach secretion and mobility
the small intestines intestinalwall is lined with what?
where does the most digestion and absorption take place?
- simple columnar epithelium
- in the sm.intestine
what does the villi and microvilli in the sm intestine do?
it greatly increases surface area for digestion and absorption
what are the 3 segments of the small intestines?
- duodenum- short c shape first layer
- jejunum-middle section
- ileum-lastand longest section
what does the duodenum receive?
- chyme from the stomach
- bile from the liver and gallbladder via the hepatopancreatic ampulla
- digestive enzymes from the pancreas via the hepatopancreatic ampulla
what does the ileum connect to?
what does the ileocecal valve do?
- connects to the large intestine
- prevents feces from entering the small intesine
what are the functions of the liver?
- largest gland in the body
- performs over 500 functions including metabolic functions
- converts glucose into glycogen
- detoxifies many poisons and drugs like alcohol
- has hepatocytes(liver cells) that produce bile 2 aide in digestion
what are the 4 lobes of the liver?
- right lobe
- caudate lobe
- quadrate lobe
what are :
- remnant of fetal circulation; in fetusserved as a liver bypass
- remnant of fetal umbilical vein
- a mesentary
what is the hepatic portal vein?
carries blood from the digestive tract to theliver
where is bile made and stored?
its made in the liver and stored in the gallbladder
liver lobules containing _________ radiate out from a ______________
what makes up the portal triad?
- portal arteriole
- portal venule
- a bile duct
what do kupffer cells do?
destroy bacteria and other foreign particles
when the hepatopancreatic sphincter is relaxed?
- bile flows from right and left hepatic ducts of the liver into the common hepatic duct
- then into the common bileduct
- out through the hepatopancreatic ampulla
- and finally into the duodenum where it is needed.
when the hepatopancreatic sphincter is contracted?
bile backs up into the common bile duct and cystic duct and finally the gallbladder where it is stored
what does the hepatopancreatic sphincter control and when is it closed?
- controls whether bile is secreted or stored
- closed when no digestion is occurring
what are the functions of the pancreas?
- both and endocrine gland (enzymes) and exocrine gland(hormones)
- makes stores and secretes enzymes fro digestion
- produces the hormones glucagon and insulin to regulate blood glucose
what is the anatomy of the pancreas?
- has a head and tail: head touches tthe duodenum and tail connects to the spleen
- contains the main panreatic duct and accessory pancreatic duct
- hepatopancreatic ampulla and sphincter control relase of pancreatic secretions
what are the functions of the large intestines?
- small amount of digestion by bacteria
- absorption of water and electrolytes to form feces
what is the:
- first portion of the large intestine;connects to the ileum at the ileocecal valve
- worm shaped; has some lymphatic function
what are the segments of the colon?
where is the rectum located?
- ascending,transverse, descending,sigmoid
- locaterd in the pelvic region
what type of muscleare the internal anal sphincter and external sphincter made of and what control are they under?
- internal:smooth muscle involuntary control
- external: skeletal muscle voluntary control
what are the teniae coli?
maintain constant muscle tone to constrict the large intestine and form pouches called haustrae
what is then lining of the small intestine lined with?
are there villi or microvilli and why?
- composed of simple columnar epithelium
- no because there is no need digestion and absorption take place elsewhere
what are the 2 purposes of motility?
what can alter it and increase it?
- moving food from mouth to anus
- mechanically mixing food to break it down into smaller pieces to increase surface area for exposure to digestive organs
- hormones and paracrines can alter it
- parasymphathetic input from the vagus nerve increases it.
what do the autorhythmic cells do?
spontaneously depolarize to cause contraction of the smooth muscle in the wall of the GI tract
what do segmental contractions do?
segements of the sm intestine contract to churn the contents bakc and forth
typically about __ _______ of fluid pass through an _______ GI tract in one day;most is __________ and thus not lost to the external environment.
fluid input = about_____ from ____and drink; ______from _________.
- digestive secretions
fluid removal from the GI tract= about______ absorbed from the ________and ______ absorbed from the _______ intestine; _____excreted in the feces.
- 7.5 L
- small intestine
what is mucus?
a viscous secretion it forms a protectice coating over the mucosa of the GI tract, and helps lubricate the contents of the gut.
what are goblet cells?
part of the simple columnar epithelium of the intestine. secretes mucus in the sm. and lg. intestine
digestion of macromolecules( carbs, proteins, fats.) is accomplished by a combination of what 2 processes?
mechanical and chemical
what is a disacharides? and example?
surcose (table sugar)
what is lactose? example?
what are monosaccharides? example
simple sugars like glucose and fructose
- cellulose (fiber)
are we able to digest fiber and why?
no because we lack the neccessary enzymes
what protein is the least digestable?
animal protein is the least. animal protein is the most digestable.
egg protein is the best with 85-90%digested and absorbed.
what are the 2 gropus of protein enzymes? and what do they do?
endopeptidases and exopeptidases.
- endopeptidases attack peptide bonds in the anterior of the amino acid chain
- whereas exopeptidases chop off single amino acid from the ends of the chain.
on average hoew much of our ingested fats come from triglycerides and why?
- about 90%
- becasue they are the primary form found in both plants and animals.
what is gastroesophageal reflux disease (GERD)? and symptoms?
abnormal relaxation or weakness of esophageal stomach junction. exposure can lead to a esophageal ulcer
heartburn regurgition belching
what is a peptic ulcer?
a crater like erosion of the mucosa of any part od the GI tract that is exposed to acid. usually i the pyloric region of th stomach or duedenum
what are gallstones?
either 2 much cholestrol or 2 little bile salts can lead to crystalization of cholesterol in the gallbladder producing gallstones; thye can block the cystic duct which require surgery to remove the gallbladder.
what is cirrhosis of the liver?
a progressive inflammation of the liver that usually results from chronic alcohol; resulting scar tissue can impede the floewo f blood through the liver
wha is diarrhea?
pathalogical state in which the intestinal secretion of fluid is not balanced by absorption, resulting inwatery stools. in extreme cases can cause severe dehydration and even death if not treated
what si constipation?
caused by consciously ignoring the defacation reflex or through increased motility; continued water absorptin creates hard dry feces that are difficult to expel
what is vomiting?
forceful expulsion of gastric and duodenal contents from the mouth; protective reflex designed to remove toxic material from the GI tract before it can be absorbed
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