Gastrointestinal A&P (11) Flashcards
What are the characteristics of the three salivary glands
parotid - largest, affected by mumps, mostly serous, 25% Submandibular - serous and mucous, 70% Sublingual - mostly mucous, 5%
How do parasympathetics and sympathetics control the salivary glands
parasympathetics stimulate saliva secretion
mild sympathetics inhibit saliva secretion (dry mouth)
strong sympathetics stimulate saliva secretion of mucous (foaming at the mouth)
besides parasympathetics, and sympathetics what can control saliva secretion
tactile stimulation (object in the mouth)
What is the pharynx, and what are its parts
the common passageway for air, foods, and liquids. it is made up of the nasopharynx, oropharynx, and laryngopharynx.
What is the esophagus
a hollow muscular tube that takes food from the pharynx to the stomach
where does the esophagus start, what does it pass through, and where does it end
it starts posterior to the cricoid cartilage with the upper esophageal sphincter, passes through the esophageal hiatus, and ends at the lower esophageal sphincter.
What parts of the esopahgus are controlled by voluntary and involuntary muscle, and what innervates it
the top 1/3 is voluntary
the bottom 1/3 is involuntary
and it is innervated by the esophageal plexus
what is deglutition
swallowing
what are the phases of deglutition
Buccal phase
pharyngeal phase
esophageal phase
what happens in the buccal phase of deglutition
bolus is compressed against the hard palate, and the soft palate which closes of nasopharynx. reflex begins and the bolus is moved toward the stomach
(volulntary)
What happens in the pharyngeal phase of deglutition
bolus comes into contact with posterior pharyngeal wall
bolus passes glottis by elevation of the larynx and folding of the epiglottis
uvula and soft palate block passage into nasopharynx
what happens in the esophageal phase of deglutition
pharyngeal muscles contract and force the bolus into the esophagus
peristalsis moves the bolus to the stomach
what is peristalsis
wave of relaxation followed by a wave of contraction of the circular muscles in the esophagus that propels the bolus toward the stomach.
how many waves of peristalsis is usually needed
1, if the bolus gets stuck stretch receptors will activate and cause more and more forceful peristalsis waves until the bolus is moved into the stomach
What are the 4 major functions of the stomach
store ingested food
mechanically breakdown food
disrupt chemical bonds in food by acid and enzymes
produce intrinsic factor (required for absorption of B12 in small intestine)
What are the 5 regions of the stomach
cardiac fundus body antrum pyloris
what are the two sphincters of the stomach
Gastroesophageal (lets food in) pyloric sphincter (lets food out)
What innervates the stomach
PNS
SNS
Enteric NS
What kind of epithelium lines all of the stomach
simple columnar epithelium (secretes mucus that covers the stomach)
What are the special cells in the gastric pits of the stomach and what is their function
mucous neck cells (produce mucous) parietal cells (produce HCl, and intrinsic factor) Chief cells (pepsinogen) Endocrine cells in pylorus (serotonin, gastrin)
What are the layers of the stomach
mucosa
muscularis mucosae
submucosa
muscularis externae
How does digestion and absorption occur in the stomach
digestion
- food becomes more fluid, pH around 2, pepsin activity increases, protein disassembly begins
Absorption
- None
What are the three phases of Gastric activity
cephalic
gastric
intestinal
what is the cephalic phase of gastric activity
the production of acid and enzymes that are controlled by the CNS, ENS reflexes, and Digestive hormones
What is the gastric phase of gastric activity
food in the stomach
stretch receptors
increase in enzyme release
what is the intestinal phase of gastric activity
small food enters intestine causing gastrin release, peristalsis of the stomach
What happens in the small intestine
complete enzymatic digestion of all foods
90% of absorption
receives pancreatic secretion
What are the three parts of the small intestine
duodenum
jejunum
ileum
What is segmentation (how does it differ from peristalsis)
it is contractions of the smooth muscle that breaks down the food, segments it, and mixes it up with digestive juices to increase absorption (peristalsis doesn’t break up food, just moves it)
What are the features of the small intestine that increase absorption
- length
- circular folds (plicae circulares) (increase surface area, slows down chyme)
- vili (movable, enhance efficiency)
- Microvili (increase absorptive surface, contain enzymes to complete digestion)
What are the intestinal glands of the small intestine
mucous cells between epithelial cells that secrete mucus,
What are the brush border enzymes
sucrase lactase glucoamylase (maltase) alpha dextrinase (isomaltase) peptidases (cytosolic, enterokinase, enteropeptidase)
What are the cells in the small intestine, and what do they do
enterocytes - absorption
goblet cells - mucin to lubricate and protect
Enteroendocrine cells - CCK stimulates pancreatic enzymes and bicarbonate
paneth cells - defensive functions (defensins)
Duodenal (brunner’s) glands - alkaline mucous to protect from low pH
What happens in the duodenum
mixing
what happens in the jejunum
chemical digestion
What happens in the ileum
absorption
what are peyers patches, and where are they found
they are pouches of lymphatic tissue (like nodes) in the walls of the ileum
What are the accessory organs of the digestive system
pancreas
liver
gall bladder
what attaches the pancreas to the duodenum
the pancreatic duct
what is 90% of the pancreas composed of
ductal and exocrine cells (acinar)
What are the endocrine secretions of the pancreas
insulin and glucagon
what are the exocrine (pancreatic Acini) secretions of the pancreas
pancreatic alpha amylase (breaks down starches) pancreatic lipase (breaks down complex lipids) Nucleases (breaks down Nucleic acids) proteolytic enzymes - trypsin
What are proteases and peptidases, where are they from and where are they active
proteases are enzymes the break down large proteins
peptidases break down small peptides into AA
they are from the pancreas, but only active in the small intestine
is pancreatic juice alkaline or acidic
alkaline
what is the liver organized into
hexagonal lobules with a cental vein in the middle, and a triad at each corner
- hepatic portal vein branch
- hepatic artery branch
- bile duct branch
what is the main type of cell in the liver
the hepatocyte
what are the functions of the liver
- metabolic regulation
- detoxification
- plasma protein synthesis
- production and storage of glycogen
- removal or hormones and antibodies
- partial activation of vit D
- removal of bacteria and RBC
- excretion of bilirubin
- bile formation and secretion
What does the liver make bile salts from
cholesterol
what is the common bile duct that goes into the duodenum
the duct composed of the common hepatic duct and the cystic duct (from gall bladder)
where does the common bile duct enter the duodenum
at the duodenal ampulla with the pancreatic duct
what is the function of the gall bladder
stores and concentrates bile, then secretes it when CCK stimulates it
What is the function of bile
emulsifies fats
What are the enzymatic steps of digestion
- gastrin (stomach) = acid production and mixing
- GIP (SI) = release of insulin
- secretin and CCK (SI) = pancreatic buffers and enzymes, and bile
- VIP (SI) = dilation of intestinal capillaries
all of which lead to absorption and utilization by the tissues
what are the parts of the large intestine (in order)
appendix ascending colon transverse colon descending colon sigmoid colon rectum anus
What are the functions of the large intestine
absorb water from food
absorb salts and some vitamins
forms, stores, and expels feces
what part of the small intestine receives material from the ileum
cecum
what are haustra
pouches in the large intestine that allow for expansion and elongation
does the colon have vili or enzyme secretions
nope
what happens to 94% of the bile salts secreted by the liver
they are reabsorbed in the terminal ileum, then the rest are absorbed in the cecum
What are the three vitamins produced in the large intestine
Vitamin K - liver needs it for making clotting factors
Biotin - used in glucose metabolism
Vitamin B5 - used in steriod and neurotransmitter production
what is produced by bacteria breaking down feces in large intestine
ammonia
indole and skatole - nitrogen “smelly”
hydrogen sulfide - rotten egg smell
gas
What is the rectum
the anus or last 6 inches of the large intestine, which is expandable to store feces and causes urge to deficate
What is the anal canal
The last part of the rectum
What are the different digestions locations of carbs and sugars
Mouth with salivary amylase
none in the stomach
Small intestine
pancreatic amylase - starches to maltose, maltotriose, and alpha-dextrin
Glucoamylase - short chains to glucose
alpha dextrinase - branched chains to glucose
lactase - lactose to glucose and galactose
sucrase - sucrose to glucose and fructose
what happens to the glucose, fructose, and galactose once it makes it into the blood
they go to the liver, where there are converted into glucose-6-phosphate. then to glycogen or fat (fat if there is excess glycogen)
What are the different locations of protein digestion
none in the mouth
pepsin in the stomach (converts proteins to short peptides)
pancreatic enzymes in the small intestine break those down into AAs or even smaller peptides
2-4 AA peptides can go into the brush border cells, where most are converted into AAs
What happens to the AAs once they are absorbed
they go to the liver, some pass right through, some are stored. if excess amino acids are present, or blood glucose is low they can be converted into glucose or ketone bodies or triglycerides
What are the steps of lipid digestion
- 10% digested in the mouth by lipases
- bile emulsifies the lipid (smaller lipid droplets)
- pancreatic lipases hydrolize the lipid droplet to form monoglyceride and free fatty acids
- those accumulate with bile salts, phospholipids and cholesterol to form micelles
- micelles allow for a lot of lipase activity and it allows the micelle to move right into cells
- in the cell they are resynthesized into triglycerides
- those are packed into a chylomicron which is carried in the lymphatic system into the blood
where is appetite regulated
arcuate nuclei in the hypothalamus
what are the two pathways the arcuate nucleus of the hypothalamus regulated appetite
NPY/AgRP = increase appetite
POMC/CART = decrease appetite
they are usually oppositely activated
how is appetite affected neuronally
fatty acids and amino acids, as well as stretching of the GI tract inhibit appetite by activating affarent vagus nerves and sympathetic nerves
How do hormones affect appetite
Grehlin CCK PP (pancreatic polypeptide) GLP1 and other gut hormones Insulin Amylin glucagon
all inhibit appetite
What is leptin
a hormone produced by fat cells that inhibits appetite
What is the effect of glucocorticoids on appetite (cortisol)
they increase appetite partially by inhibiting the action of leptin.
what causes increased secretion of glucocorticoids and thus causes increased appetite
stress
What mechanical activities happen at each location in the GI tract
mouth - mastication Esophagus - swallowing Stomach - peristalsis, contractions SI - peristalsis and segmentation LI - peristalsis and mass movement
Where does amylase come from and what does it breakdown
saliva and SI
it breaks down carbs
where does maltase come from and what does it break down
the SI and it breaks down maltose
Where does pepsin come from and what does it break down
the stomach
it breaks down proteins
where does trypsin come from and what does it break down
pancreas
proteins
where does peptidase come from and what does it break down
SI
peptides
where does nuclease come from and what does it break down
pancreas
DNA and RNA
where does nucleosidase come from and what does it break down
pancreas
nucleotides
Where does lipase come from and what does it break down
pancreas
lipids
What is the function of gastrin
stimulates peristalsis of the stomach and relaxation of the pyloric sphincter
stimulates pepsinogen secretion
Gastrin
HIstamine
What is the function of CCK
stops peristalsis and contracts pyloric sphincter
it opposes gastrin
What is pepsinogen
the inactive form of pepsin that is converted into pepsin by HCl
What is the affect of alcohol, caffeine, and nicotine on gastric secretion
they increase gastrin, pepsin, histamine, HCl and inhibit mucus and bicarbonate
therefor this causes stomach and heart burn
what increases pancreatic secretion as well as bile secretion
PNS
CCK
Gastrin
Secretin - bicarbonate
What is the function of enteropeptidase
it converts the inactive trypsinogen to the active trypsin, which in turn converts other inactive pancreatic enzymes into active enzymes
