lecture 17/18: the digestive system Flashcards
what are the basic functions of the digestive system
- Ingestion
- Secretion
- Mixing and propulsion
- Digestion
- Absorption
- Defecation
what are the 4 layers f=if the GI tract
Mucosa
• Submucosa
• Muscularis
• Serosa
arrange these fom innermost to outmost: muscularis, serosa, mucosa, submucoa
mucosa
submucosa
musclaris
serosa
which layer of the GI tract allows movement
sersa
which anchors organs: serosa or adventiationn
adventia
whta is the only organ that has 3 muscualis layers
stomach
what are the 3 layers of the mucosa of the GI tract
1) lining epithelium
2) lamina propira
3) muscularis mucosa
what layer is inn direct contact with the GI tract
lining of the epithelium
epithelium in the mouthm, pharynx, esophaus and anal canal serves what function
protective function n(against highly acidic food)
what do lining epithelium in the stomach and intensites functions in
secretion and absoprtion
every 5-7 days what happens to epithelial eclls
they are repalced by new ones
within the absorptive epithelial cells, what ar the 2 subsets of cells
exo and endocrine
what is the function of the exocrinne cells in the epithelium of GI tract
Exocrine cells which secrete mucous and fluid into the
lumen
what is the function of endocrine cells in the epithlial cells of the GI tract
Endocrine cells which secrete hormones into the
bloodstream
what is the function nof lamina propria
Supports epithelium and binds it to the muscularis
mucosa
what does lamina propira conntainn that serves a protetctive function
mucosa-associated lymph tissue (MALT)
what is the function of muscualris musocsa
Increases the surface area for digestion and absorption
• Movement of muscle ensures that all absorptive cells
are fully exposed to contents of the GI tract
the subvcua of the GI tract contains what plexus
meissner plexuer
what is the meissners plexus
portion of the entreric nerve plexus (brain of the gut)
what does the meissners plexus contai (neurons) and what is the functtion
• Contains sensory and motor enteric neurons and
parasympathetic and sympathetic postganglionic
fibers that innervate the mucosa and submucosa
• Important in controlling secretions of the GI tract
the meissner;s plexus is only located in what layer of the GI
submucosaa
what areas contrain skeletal muscle that produce voluntary swallowing
mouth
pahrynx and superior and meiddle parts of the esophagus
skeletal muscles of the GI permit voluntary control of swalloingn and what else
control of defecation
throughout the GI tract, is it skeletal or smooth msucle
smooth
what ar the 2 layers of muscualr smooth in the msuclris muscle
outer longitnal and inenr circulae
which is more outer in the muscularis of the Gi tractt, longitdunal or circulat
longuatial
what tis the function of involuntary contcations of the muscularis in the GI
Involuntary contractions help break down food physically, mix
it with digestive secretions and propel it along the tract
where is the myenteric nerve pelxus location (in what layer)
muscualris
what plexus is located in the muscualr layer of the GI
myenteric nerve plexis
what are the fibers found i nthe myenteric nerve plexus and what do they control
- Parasympathetic ganglia
- Sympathetic postganglionic fibers
• Controls primarily the frequency and strength of
contraction of the muscularis
what is the most superfical layer of the GI tract
seosa
what is another name of the serosa of the GI tractt
Also called the visceral peritoneum on structures inferior to the
diaphragm
what is the peritoneum
enveloppe that surrounds the digestive organs
what does parital paritoneum line
lines the walls of the abdominopelvic cavity
whatt does the vscieral peritoneum cover
some organs in the cavity and form their serosa
what is the peritoneal cavity
thin spcae in between the patietal and visceral perionem (contain serous fluid)
be able to udnerstand diagram in peritoneum
.
where is the greater omentum located
on greater curvatture of stomach
what is the greater omentum made of
visceral peritoeum and fat
what is the alrgets peritoneal fold
greater omentum
where does the greater ommentum hang
loosely over the transverse colonn and coils over the SI
TRUE or false: the greater omentum is a double sheet that folds back onto ittself
true
what does the falciform ligament attach
Attaches the liver to the anterior abdominal wall and diaphragm
true or false: the falciform lig is an extension of visceral peritenum
true
where is the falciform lig located
snteior between right and left loves
what does the lesser omentum suspend
suspends stomach and duodemun from liver
wher is the lesser omentum located
on lesser curv of stomach
what does the lesser omentum arrise as
arrises as 2 folds in the serosa of the stomach and duodenum
what does the mesentery do
bidns the SI to the posterioral abdominal wall
what perotoneal folds are continous with each other
mesentery and mesocolon
what is the mesocolon
fold of the periotoneum which binds the LI to tthe posterior abdominnal wwall
what are 2 specific regions of the mesocolon
sigmoid and transverse
how are the Lips (labia) are attached to their corresponding gums
by a fold
of mucous membrane called the labial frenulum
what is the hard palate formed by
maxilla and palatine bones
what is the soft palate
Muscular separation between oropharynx and nasopharynx
what is the uvula
• Uvula – muscular process hanging from the free border of the soft
palate
explain the movement of the soft palate and uvual during swalling and what does that preventt
During swallowing, the soft palate and uvula are drawn superiorly
closing off the nasopharynx, preventing food and liquid from entering
the nasal cavity
where are the palatine tonsils location
stim between the arches in oropharyn
where are the lingnual tonsils locationn
at the base of the tongue
what are the fauces
opening between the oral cavity and the pharynx (throat)
witthout food, how much saliva do the salivary glands profuce
Secrete just enough saliva to keep mucous membrane of mouth and
pharynx moist and to cleanse the mouth and teeth
when food enters the mouth, what happens to secretion
secrettion increases and chemical breakdoqn od food begins
what are some small salivaty galnds
Labial, buccal, and palatal glands in the lips, cheeks and palate as well as
lingual glands in tongue
where are parotid glands located and what is their function
- Located inferior and anterior to the ears, between the skin and masseter muscle
- Secrete saliva into the oral cavity via the parotid (Stensen’s) duct
where does the facial neve pass through
parotid gland
where are the submandibular glands found
Found beneath the base of the tongue in the posterior part of the floor of the
mouth
Where do the submandibular ducts entetr
the oral cavity lateral to the lingual frenulum
are the sublingual glands superior or inferior tto submandibular glands
superior
what are the ducts of the sublingual glands and where do they open
Lesser sublingual (Rivinus’) ducts open into the floor of the mouth
true or false: the salivary glands receive both para and sympathic innevation
true
what do sympatheitc fibers of the salivary glands do
Sympathetic fibers initiate vasoconstriction which decreases saliva
production
what type of stimualtion domincates the salivary glands during stress and what does that cause
sympathic
causes dry mouth, stops secrete of saliva to connserve h20
what do parasympathtic fibers of salivty galnds do
Parasympathetic fibers of the glands produce vasodilation and increases the production of saliva
what is saliva mostly made by
water
what are the solutes in salivty
Solutes include mucous, lysozyme (a bacterolytic enzyme), digestive enzymes
(salivary amylase and lingual lipase) and traces of salt, protein and other
organic compounds
what is salivary amylase
causes breakdon=wn of carbs in the mouth but do not get activatted intil somach
explain lingual lipase
Receptors for taste buds in the tongue are stimulated by
chemicals in food and convey impulses to two salivary nuclei
(sup. and inf.) in the brain stem resulting in an increase in saliva
secretion
• Smell, sight, sound, and/or thought of food may also stimulate
secretion of saliva
true or false: the tongue is a primary digestive organ
false, accessory
what is the tongue and what is is attached to
Composed of skeletal muscle covered by a mucous membrane
• Attached to the hyoid bone, styloid process and mandible
what are the extrinsic muscles fo the tongue and what do they do
hyoglossus, genioglossus and
styloglossus
• Move the tongue form side to side and in & out to maneuver food
explain the or/ins or intrinsic muscles of tongue and their function
n• Intrinsic muscles originate and insert into the connective
tissue within the tongue and alter its shape and size for speech
and swallowing
how is the tongue atached to the mandible
lingual frenulum
what is ankyloglossia
condition where a persons lingual frenulum is
abnormally short or rigid impairing eating and speech
what are the dorsum and lateral srufaces of the tongue covered with
papillae
what are the 4 types of papillar
- Fungiform Papillae
- Filliform
- Circumvallate
- folliate papilla
do the foliate papilla contrain traste buds>
yes
which papilla does not contain taste buds
filliform
where does the pharynx enter from and to
The pharynx extends from the internal nares to the esophagus
and larynx
true or false: Oropharynx and laryngopharynx have digestive and respiratory
functions
true
what does the muscualr conntent of the Oropharynx and laryngopharynx help with
help
propel the food into the esophagus and then into the stomach
what is deglutitionn
is the mechanism that moves food from the mouth
to the stomach = swallowing
what is the esophagus
muscular tube thatt lies posterior to tthe trachea
does the esophaus lie anterior or psoterior to trache
posterio
does the esophagus stop at the diaphram?
no it oasses through the diapprahm at the esophangeal hiates
what is it called when a portion of the stomach protrudes through the esophgeal
hiatal hernia
what are the4 layers of the esophaus
adventia
muscularis
submusoa
mucosa
what is the difference between adventiat and serosa in the esophagus.
Unlike the serosa, the connective tissue merges with the
connective tissue of surrounding structures of the
mediastinum attaching the esophagus to them
the superior 1/3 of the esophagus is made of what type of muscle
skeletal
the middle 1/3 of esphaus is made from what msucle
skeletal and smooth muscle
the infeior 1/3 of esopgus is amde from
smooth muscle
what does the submucosa of the esophagus cotnain
Contains areolar connective tissue, blood vessels and
mucous glands
the mucosa of the esophagus is near wher
near the stomach ,contain muucous gland
what is the function of mucosa of the esophaugus
Offers protection against abrasion and wear & tear from
food particles that are chewed, mixed with secretions and
swallowed
what is the function of the esophahus
Secretes mucous and transports food into the
stomach
what does the upper esophageal sphinctor control
passage of food from laryngopharyngeal
what does the elevation of the larunx cause the upper esophanial sprincter todo
to relax and the bolus enters the esophagus
during exhalation, what is happening to the upper esophageal spnincter
it is relatxed
how is food pushed fhrough esophagus
peristatlsis
explain the profucess of moving food throug hesohagus
progression of involuntary contraction and relaxation of
the circular and longitudinal layers of the muscularis
• Controlled by the medulla oblongata
• Circular muscle contraction constricts the esophageal wall and
squeezes the bolus towards the stomach
• Longitudinal muscle fibers inferior to the bolus also contract
shortening the inferior section and pushing its wall outward so it
can receive the bolus
• Mucous secretes by esophageal glands lubricate the bolus and
reduces friction
what is another name for lower esophgeal spnincter
gastroesophageal/cardiac shincnter
what is the lwer esopheal spnincter
narrowing of the esophagus just superior to the diaphram
when does the loer esophageal relax
Relaxes during swallowing allowing the bolus to pass
into the stomach
what is the position of the stormach in relation to the diaphram
inferior
whatt connects the esophagus to the duodenum
the stomach
what is the 1st part of the SI
dudodeum
what forces the food intto thte dudoenum
stromach
does the stomach force large or small quantities into tthe duodenum
small
explain the position of the stomach during inhalation and exhalation
The diaphragm pushes it inferior with each inspiration and pulls it up with
each expiration
when the stomach is empty ,what is the side a
large sausagee
true or false: digestion of starch starts in the stomach
false, starts in mout hwith saliva
where dos the digestion of protein and triglycerides begin
stomach
what happens to the semi bolus in hte stomach
gets converted to a liquid and certain substances are absrobed
what is it called when the bolus becomes liquid
chyme
what surrounds the superior opening of the stomach
cardia
what is the fundus of the stomach
rounded portion superior and to the L. of the
cardia
is the fundus to the right or left of the cardia
to tthe left
in the body of tthe stomach inferior or superior to the fundus
inferior
the pylorus are thee regions that conenct to where
the duodenum
the pyloric antrum connects to where
the body of stomach
to pyloric canal leads to what
duodenum
what is the passageway from pyloris to duodenum called
pyloric sphincter
what is the pyloric sphincter made of
thickneing of the circular muscle
When the stomach is empty, the mucosa lies in large
folds called what
Rugae
explain the lesser curvature
concave medial boder
what is the gerater curvative
concave lateral border
what is the artrerial supply to the stomach
Arterial supply: R / L gastric arteries ( form an
anastomoses along the lesser curvature) , R /L
gastroepiploic (form an anastomoses along the greater
curvature) and short gastric (supplies fundus)
R/L gastric ateries from an anastomoses along what
lesser curvature
R/L gastroepiploic form an anastomeses along where
greater curvature
what does the short gastric a suppy
funfus
what is the parasympathtic inenrvation of the stmach
vagus
what is the sympathteic inenrvatiton of the stoamch
celiac ganglia
the greater curvatture lies around what organ
against spleen
the lesser curvature lies close to what organ
liver
what region of the stomach is considered the “storage: region and why
fundus
less muscle and curning
what are the 4 layers of the stomach (deep to superficial)
1) mucosa
2) submucosa
3) muscularis
4) serosa
what is the deepest layer of the stomach
mucuosa
what are the contents of the muscoa of stomach
lamina propria
muscularis mucosa
gastric glands
gastric galnds are located in what layer of the stomach
mucosa
where is the lamina located (what layer)
mucosa
gastric glands are what kind of cells
exocrine, secrete their products into the stomach lumen
what do the mucous neck cells secrete
mucous
because gastric juices are very acidic
what do cheif cells in the stomach secrete
secrete pepsinogen and gastric lipase
what does gastric lipase inittiate
initiates breakdown of fat
what do the parietal cells in the gastric glands of the stoamch produce
HC1 and intrinsic factor (needed for absorption of b12)
what are the 3 exocrine cells found in the gastric galnds
mucous neck cells
cheif cells
parietal cells
what forms the gastric juice
secretions from the exocrine cells of the gastric galnds
give an example of the enteroendocrine cell i nthe mucosa layer of the stomach
g cell
where are g cells located
pyloric antrum
what does the g cell secrete
gastrin (hormone) into the blood stream 0
what is the function of gastrin secrete by G cells
• Stimulates growth of gastric glands and secretion of
large amounts of gastric juice
• Also strengthens contraction of the lower esophageal sphincter, increases mobility of stomach and relaxes
pyloric and ileocecal sphincter
what is submucosa of the stom
areolar connective tissue
how many layers of muscles are there in the muscularis muscle of the stomach
3
what are teh 3 layers of the staomch (outer to inner )
outer longitudinal
middle circualr
inner oblique
where are the smooth muscles of the stomach mostly located
in the body
true or false: in every organ, there are 3 layers of smooth muscle
false, only place there are 3 is in the stomach
what is the innermost muscualr layer (smooth) of the stomach
oblique
the serosa is the portion covering the stomach and is part of the BLANK
visceral peritoneum
• At lesser curvature, visceral peritoneum extends superior to what organ
liver
• At lesser curvature, visceral peritoneum extends superior to the liver - to form what
lesser omentum
• At greater curvature, the visceral peritoneum continues inferiorly as what
as the greater
omentum and drapes over the intestines
the food mixes with the gastric juice reducing it to a liquid called BLANK
chyme
true or false: The pyloris remains partially closed and as food reaches it,
trtue
each wave/contraction of the stoamch forces what
forces several ml of chyme into the duodeum
digestion of proteins begins where
stomach
digestion of proteins is done mainly by what enxyme
pepsin
proteien chains of many amino acids can be broken down into what
peptides
pepsin can help in digestion of what types of proteins
milk
what is the function of gastric lipase
splots the short chain trsis (fats) found inmilk
=limited role in ttthe adult stomach
=rely more on pancreatic lipase
true or false: Within 2-9 hours after eating a meal, the stomach usually has
emptied its contents into the duodenum
false, 2-4
where does chyme pass after the stomach
into the duodenum of the small intenstine
what does chemical digestion in the SI depend on
activity of the pancrease, liver and gall bladder
the pancreas is considered what type of gland
retroperitoneal glands
where is the head of the pancrease
Head: expanded portion of the organ which lies near the
duodenum
where is the body of the pancreas
Body: superior and to the left of the head
where is the tail of the pancreas
closer to the spleen, tapering of the body
what part of the pancreas is closer to the spleen
tail
pancreatic duct joints with what other duct
common bile duct
where does the pancreatic duct empty
in the greater duodenal papilla
where does the accessoru pancreatic duct empty
lesser duodonal papilla
the common bile duct and pancreastic duct meet up and empty where
greater duodenal papilla
what is the arterial supply of the pancreas
sup. and inf. pancreaticoduodenal aa, splenic artery, and superior
mesenteric aa.
the inferior pancreaticoduondal branches off what artery
supeerior mesenteric a
what is the innervation of the pancreas donee by
Celiac and superior mesenteric plexuses
true or false: innervation is the main controller of pancreatic secretion
Innervation is presumed to influence enzyme formation but pancreatic secretion is largely controlled by the hormones secretin and cholecystokinin (CCK) released by the small intestine.
pancreas is made up of small clusters of what types of ceells
glandular epithelial cells
what are 99% of the glandular epithelial cells in the pancreas called
acini
the acini clusters in the pancease make up what portion of the pancreas
exocrine
what do the acini cluster cells secrete in the pancrease
cells secrete a muxture of fluid and digestive enxymes called pancreatic juice
what cells in the pancreas make the pancreastic juice
acini
1% of the cluster glandular epithelial cells are what type
pancreastic islets
the pancreatic islets form what part of the pancreas
endocrine portion
what do pancreatic isletes secrete
secrete the following hormones: glucagon, insulin, somatostatin &
pancreatic polypeptide
what is pancreatic juice made from
Consists of water, salts, sodium bicarbonate and several digestive
enzymes
what gives the pancreatic juice a slighlty alkaline pH
sodium bicarbonate
what buffers the acidic juice in the chyme
pancrease
what stops the action of pepsin in the sotmach
pncrease
true or false: the pancreas Creates proper pH level for action of digestive enzymes in the S.I.
true
what is the Carbohydrate-digesting enzyme
• Pancreatic Amylase
what are the • Protein-digesting enzymes
• Trypsin, Chymotrypsin, Carboxypeptidase, Elastase
what is the • Triglyceride-digesting enzyme
• Pancreatic lipase
what are the• Nucleic-acid digesting enzymes
• Ribonuclease and Deoxyribonuclease
what is the heaevieset gland in the body
liver
what is the largest organ in the body
skin
what is the 2nd larger organ in the body
liver
what covres the liver
Almost completely covered by visceral peritoneum
and completely covered by a dense connective
tissue deep to the peritoneum
what are the right and left lobes of the liver divided by
falciform lig
what are the 4 lobes of the lvier
right
left
caudate
quadrate
what are the functional cells of the liver
hepatocytes
what is the function of hepatocytes
filttering
how are hepatocyes arranged
Arranged in irregular, interconnected plates around a central vein
what are the sinusoids of the liver
Sinusoids contain fixed phagocytes (stellate reticuloendothelial cells –
Kupffers cells) which destroy worn-out leukocytes and RBCs, bacteria,
and other foreign matter from the G.I. tract venous blood
what cells secrete bile in liver
hepatocytes
explain the pathway of bile
enters bile canaliculi which empty into small bile ductules
• the ductules pass bile into bile ducts
• eventually merge into the R/L hepatic ducts
• R/L hepatic ducts unite to form the common hepatic duct
• Common hepatic duct joins the cystic duct and they form
the common bile duct
where does bile first enter and where does that eempty
enters bile canaliculi which empty into the ductules
the bile ductules pass bile where
into bile ducts
bile ducts eventually merge into what
R/L hepattic ducts
RL hepattic ducts unite to form what
common hepatic duct
common hepattic duct joints the BLANK and they form the BLnk
• Common hepatic duct joins the cystic duct and they form
the common bile duct
what does the falciform lig anchor
anchors to tliver tto tthe diaphragm
where is the round lig of the liver located
Located in the free border of the falciform ligament
what ligament isa remnant of the umbilical vein of the fetus
round lig
where does the round lig extend from
Extends from the liver to the umbilicus
what lig suspend the liver from the diaphragm
R/L coronary lig
what is the blood supply for the liver
hepatic artery and hepatic portal vein
branches from the hepatic artery and vein carry blood where
Branches from both the artery and vein carry blood into the sinusoids where O2, most nutrients and certain
toxins are taken by the hepatocytes
what tis the pathwat of Products manufactured by the hepatocytes & nutrients
needed by other cells are secreted back into the blood
(drained into central vein - hepatic vein - IVC)
what is the portal triad
hepatic portal vein, hepatic artery, and bile duct
what is the parasymp innervattion of the liver
vagus
what is the sympathetic innervation of the liver
celiac ganglia
where is the gall bladder located
located in a depression on the posterior surface of the liver
what is the most distal part of the gallbladder
fundus
which part of the gallbladder hangs inferiorly from liver
fundus
the portion where the body of the gallbladder narrows is called what
the neck
what is the function of the gall bladder
store and concentrate bile until it is needed by
the S.I.
what is the blood supply for the gall bladder
cycstic artery
what is the innervation of the gall bladder
branches from the celiac plexus and Vagus
nerve
does the gallbladder produce bile ?
no just stores and concetrates it
bile is mostly an ecretoru product but also partially a blank secretion
digestive
what plays a role in emulsification
bile salts
what happens to the greater duodenal pappila b/w meals
Between meals, the greater duodenal papilla closes off and bile
flows into the gall bladder for storage
• After a meal, parasympathetic impulses along the vagus nerve
stimulate the liver wjat
to increase bile production
Fatty acids and amino-acids in chyme stimulate duodenal
enteroendocrine cells to secrete what
Cholecystokinin (CCK)
in the blood
what are the functions of Cholecystokinin (CCK)
in the blood
1) CCK causes the contraction of the gall bladder ,
squeezing stored bile into the cystic duct and through
the common bile duct
2) CCK also causes relaxation of the sphincter around the
greater duodenal papilla allowing bile to flow into the
duodenum
where does the majority of digestion and absorption occurs
small intesntie
what are the 3 regions fo the SI
duodenum
jejunum
illeum
what are the permanent ridges in the small intenstine mucosa called
circular folds
where do circular folds behing and end
Begin in the duodenum and end in the mid-portion of the ileum
what is the fucntion of circular folds in the SI
Enhance absorption by increasing the S.A. and causing chyme
to spiral as it passes through the S.I.
what is the arterial supply of the SI
superior mesenteric and gastroduodenal
what is the innervation of teh SI
superior mesenteric plexus and vagus n.
two autonomic plexuses are found within the wall of the SI, what are they
1) myenteric plexus
2) meissners plexus
where is the myenteric plexus located
between muscle layers in the SI
where is the meissners plexus locatied
in submucosal layer of the IS
tthe myetneric and meissners plexus are associated with waht system
CNS (enteric)
the epithelium of tje mucosa of the SI is made up of what 4 cells
Absorptive cells
- Goblet cells
- Enteroendocrine cells
- Paneth cells
what is unqiue to the mucosa layer of the SI
contains villi
what is the function of th villi in the SI wall
Greatly increase the S.A. of the epithelium available for absorption and
digestion
each villi of the SI contrains a core called what
lamina propira
within each villi there is what
Within each is an arteriole, a venule, a blood capillary and a central
lacteal (lymph capillary)
Nutrients absorbed by the epithelial cells lining the villi in the SI pass through what
the wall of the capillary or central lacteal to enter the blood or lymph
what is teh function of the absorptive cells in the muscosa of SI
digeset and absorb
what is teh function of the globlet cells in the muscosa of SI
secrette musouc
what is teh function of the enteroendocrine cells in the muscosa of SI
secrete secretin , CCK or GIP (glucose dependanct insulinotrophic peptide)
what do panaeth ceells secrete
Secrete the bacterial enzyme lysozyme and has some
phagocytotic functions
the lamina propria of the mucusa of the SI has many BLANK for immune support
has many mucosa associated lymphoid
tissue (MALT):
what are two MALT
Solitary lymphatic nodules (mostly in distal ileum)
• Peyers patches (also found mostly in distal ileum)
where are peyers patches located (what layers )
mucosa layer of SI
where are brunners galnds located (what layer)
submucosa of duodenum
what do brunners glands secrete
• Secrete an alkaline mucous which helps
neutralize gastric acid in chyme
true or false: in the Si muscualris layer, we have oblique and circular smooth layers
false, longitinal and circular
what is the most superficial layer os the SI
serosa.
is intestinal juice alkaline or acidic
alkaline
what does intesntinal juice aid with
Aids with the absorption of substances as they come in contact
with the villi
Absorptive epithelial cells in the SI synthesize what
many digestive
enzymes (brush-border enzymes) and insert them into the
micovilli
what are the 2 types of movements taht occur inn the SI
Segmentation
• Migrating motility complex (a form of peristalsis)
segmentation mixes chyme with what
digestive juices
segmentation brings food particles in contact with what
in contact with the mucosa for absorption
explain segmentation in the SI
Starts with the contraction of circular muscle
- Constricts intestine into segments
- Segments divide again with the a second contraction of the muscle fibers lining each segment
• Finally, the muscles that initially contracted relax forming large segments
again
does segmentation occur after most of the meal is absorbed
no segnmentation stops and peristalsis begins
explain th migrating motility complex MMC
Begins in lower portion of stomach
• Pushes chyme forward into the S.I.
• The migrating motility complex (MMC) slowly migrates down the S.I.
• MMC reaches the end of the ileum in 90-120 minutes
Ø Then another MMC begins
when does absorption in the SI occur
Occurs once food has been changed into forms that can pass
through the epithelial cells lining the mucous into blood and
lymphatic vessels
most of the absorption (90%) occurs where
in SI
if 90% of digetion occurs in SI, 10% comes from where else
stomach and large intenstive
what is the terminal portion of the GI traction
the large intenstine
the large intenstine is divided into what 4 mainn regions
cecum
colon
rectum
anal cnaal
what is the function of the large intensine
Functions to complete absorption, produce certain vitamins,
form feces, and expulse feces from the body
how is the large intestine attached to the posterior wall
by the mesocolon
where does the cecum lie
hangs from th ileocecal sphincter
the appendix is atatched to where
cecum
true or false: all 3 portions of the LI are considered retroperitoneal
false, only 2 (ascneding, descnedinng)
what is the right colic (hepatic) flexure
abrupt turn inferior to the liver
what is the lft colic splenic flexure
abrupt turn inferior to the spleen
what is the begininng and ending of the sigmoid colon
begins near L. iliac crest and ends at the level of
3rd sacral vertebrae
the rectum lies anterior to what
anterior to sacrum and oxxygic
what is the last part of the rectum called
anal canal
what is the anus guarded by
Guarded by an internal sphincter of smooth muscle (involuntary) and an
external sphincter of skeletal muscle (voluntary)
true or false: yhe anal sphincters are all voluntarility cotnrolled
false, Guarded by an internal sphincter of smooth muscle (involuntary) and an
external sphincter of skeletal muscle (voluntary)
what is the arterial supply fo the LI
sup. / inf. mesenteric aa.,
sup. , middle, and inf., rectal aa.
what is the sympathetic innnervation of the LI
from the celiac, superior and inferior
mesenteric ganglia
what is the parasymptethic inenrvation of the LI
from the vagus and pelvic
splanchnic nerves
true or false; there are no villi or circualr folds in the mucosa of the LI
ttrue
what does the mucosa of the LI consist of
lamina propria and muscualris mucosa
what are the cells in the mucosa of the LI
Epithelium contains mostly absorptive cells (for water absorption) and goblet cells (secrete mucous)
the mucosa of the LI contrains what types of nodules
Contains solitary lymph nodules
what are the muscularis layers of the LI
Consists of external longitudinal muscle layer and internal circular layer
what happens when the lonngitudinal muscle of the LI wall are thickened
forms 3 bands called the taenia coli
how is the taenia coli made
Some portions of the longitudinal muscle are thickened forming 3 bands
called the taenia coli
what forms the haustra
Tonic contractions of the bands (Tania coil) form a series of pouches called haustrae
Tonic contractions of the bands form a series of pouches called BLANK
haustrae
serosa layer of the LI is part of what
visceral peitoneum
Passage of chyme from the ileum into the cecum is controlled by WHAT
the ileocecal sphincter (slow process)
As food accumulates in the cecum and ascending colon,
what begings
movement of the colon begins
when does movement of the colon begin
As food accumulates in the cecum and ascending colon,
movement of the colon begins
true or false: haustra remain relaxed until they fill up
true
explain haustral churning
Ø Haustrae remain relaxed until they fill up
Ø After distension reaches a certain level, the wall contracts
and pushes the contents into the next haustrae
does peristalsis in the LI occur at a slow or fast rate
slow rate
explain mass peristalsis in the LI
Ø Strong peristaltic wave that begins in the middle of the transverse colon
and rapidly drives the contents into the rectum (3-4 times a day, during or
right after a meal)
how does the final stage of digestion occur
through the activity of
bacteria in the lumen
what are the 4 functions of the LI
Ø Prepares chyme for elimination
Ø Fermentation of remaining carbohydrates, release of H+, CO2, methane gases
Ø Remaining protein are converted into indole, skatole, hydrogen sulfide, and fatty acids
Ø Absorbed and transported into the liver, excreted in urine
where are vit b and k absorbed
in the colon
after 3-10 hours, what happens to the chyme in the LI and why
chyme has become solid/semi-solid as a result
of water absorption
true or false: Large intestine also absorbs electrolytes like Sodium and Chloride and some vitamins
true
