E-learning 6 GI system Flashcards
GI tract consists of
- oral cavity
- oesophagus
- stomach
- small intestine (duodenum, jejunum, ileum)
- large intestine (caecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum)
- anal canal and anus
what are associated with the GI tract
the liver, gall bladder and pancreas
what epithelium is the mouth and tongue covered in
stratified squamous epithelium with and underlying submucosa containing salivary glands
what are the 3 main salivary glands
parotid
submandibular
sublingual
which gland is below the tounge
sublingual
which glad is below the jaw bone (the mandible)
submandibular
which gland is close to the ear
parotid gland
which gland secretes both serous and mucous saliva
submandibular
which gland secretes serous saliva
parotid
which gland secretes mucous saliva
sublingual
where is saliva produced in the saliva glands
the acini
how is saliva produced
by active filtration of ions from blood
where is the composition of the saliva modified within the gland
in the ducts
what type of saliva does parasympathetic stimulation produce
large volumes of watery saliva
what type of saliva does sympathetic stimulation produce
small amount of mucous saliva
the functions of saliva
- lubrication due to mucin content
- digestion due to presence of a-amylase
- protection of oral mucosa through lubrication, rinsing action and alkaline pH
- antibacterial through actions of antimicrobial thiocyanate
- thirst stimulation
- speech
- absorption in the mouth
what are the muscles of the tongue and cheeks called
buccinator muscles
what do buccinator muscles do
aid pulveristation and bolus formation
the muscles of mastication move the mandible (lower jaw bone) bringing its teeth into contact with the teeth of the..
maxilla (upper jaw bones)
what is the joint that moves known as
temporomandibular joint (TMJ)
what are the four muscles of mastication
temporalis
masseter
lateral pterygoid
medial pterygoid
which muscle is the main effector
temporalis
what does the masseter do
elevated and protrudes the lower jaw
what do the pterygoids do
help protrude the lower jaw unilaterally which creates side to side movements
(1st) pharyngeal stage of swallowing:
is the initiation of swallowing voluntary or involuntary
voluntary
what pushes the bolus posteriorly
the muscles of the tongue
the oral cavity opens into the
oropharynx
when is the swallow reflex triggered
when the bolus contacts the back of the pharynx
what rises to block off the nasopharynx
the soft palate (palatine muscles covered in mucosa)
what blocks the laryngeal opening
the elevation of the larynx moves the epiglottis over the laryngeal opening
which muscles lift the larynx to close off the airway
muscles of the neck (suprahyoid muscles)
what pushes the food down the pharync and into the oesophagus
the pharyngeal constrictors contracting sequentially
(2nd) the oesophageal stage of swallowing:
what pushes the food towards the stomach once the food has entered the oesophagus
the involuntary action of the smooth muscle
what level does the oesophagus pass through the diaphragm
T10
at the junction between the oesphagus and stomach there is the
lower oesophageal sphincter
the lower oesophageal sphincter generally has a high tone which means what
is has a degree of sustained contraction
it has to relax when we swallow to allow food to enter into the stomach
bands of muscle from the diaphragm further increases…
tension
the oesophagus enters the stomach at what angle
and acute angle
all the above features prevent what
reflux
what epithelium is the oesophagus lined with throughout its length
squamous epithelium
the stomach is J-shaped and it lies just below the
diaphragm to the left of the abdominal cavity
the stomach opens into the duodenum (proximal part of the SI) at the
pyloric orifice
the fundus is at the ___ of the stomach
top
greater curvature is the
outside curve of the stomach
the lesser curvature is the
inside curve of the stomach
antrum is the _______ of the stomach
bottom
what is after the antrum
pylorus and pyloric sphincter
the fundus and body of the stomach secrete acid from
parietal cells
they secrete pepsin from
peptic/chief cells
the antrum of the stomach produces
endocrine secretions which control gastric secretions itself as well as gastric motility
the endocrine secretions are
gastrin
histamine
somatostatin
the epithelium of the stomach consists of columnar epithelia. Tight junctions in this layer prevents
damage to underlying tissues from acid secretions
the small intestine is divided into three parts
duodenum
jejunum
ileum
the duodenum loops round and can be divided into four parts
superior, descending, horizontal and ascending
superior part travels
superiorly and posteriorly at the side of the vertebral column (L1)
the descending part travels
inferiorly over part of the kidney (L3)
the horizontal part travels
medially to the left crossing the aorta (L3)
the ascending part travels
superiorly on the left of the aorta where it becomes jejunum (L2)
the descending duodenum receives further digestive secretions from the liver and gallbladder via the common bile duct and the pancreas via the main pancreatic duct
the jejunum begins at the
duodenojejunal junction to the left of L2 vertebrae
the jejunum is the middle part of the small intestine and becomes the
ileum
the majority of the small intestine (jejunum and ileum) are anchored to the
posterior abdominal wall
whats the main function of the large intestine
to absorb ions and water
intestinal contents are liquid as the enter the large bowel, absorption of water in the colon produces
a more solid mass
the muscles of the colon act to move the intestinal contents towards the
anus
there are three bands of longitudinal smooth muscle found in the large intestine known as
taeniae coli
the large intestine is split into regins
caecum
ascending colon
transverse colon
descending colon
sigmoid colon
rectum
anal canal
caecum
the first section of the large intestine
begins at the ileocaecal junction
it is a pouch of the large intestine and it contains the vermiform appendix
colon
the ascending colon travels superiorly from the right lower to right upper quadrant which then forms a 90 degree bend to the left into the transverse colon, this angle is the colic flexure
the transverse colon travels from the right upper quadrant where it forms a 90 degree bend into the
descending colon, this angle is known as the left colic flexure
the descending colon travels from the left upper quadrant to the left lower quadrant then becomes the sigmoid colon which is s shapes and connects the descending colon to the
rectum
the rectum and anal canal sit within the pelvic cavity posterior
to the vagina/prostate
where is the liver is found
right upper quadrant of the abdomen, directly beneath the diaphragm.
the liver consists of four lobes
right
left
caudate
quadrate
It is made up of a fundus (top), body (middle) and neck (bottom). the neck leads to the ____ ____ which transports bile to and from the gallbladder
cystic duct
Bile has multiple functions in the body. Its bicarbonate content produces an alkaline pH that serves to decrease the acidity of gastric contents released from the stomach, thus preventing damage to the intestines. Decreased pH also facilitates the emulsion of fats from the stomach by salts contained in the bile. The emulsification of fats by bile salts increases the surface area of these insoluble nutrients and increases the rate of their digestion.
what cells produce bile
hepatocytes in the liver
Hepatocytes or liver cells are epithelial cells that are arranged to form a…
3D lattice
in the liver, ______ run between each layer of hepatocytes.
sinusoids
what do sinusoids allow
close contact between the hepatocytes and the portal blood supply
The products of hepatocyte function are removed via small channels between the cells, called…
canaliculi
The canaliculi then drain into the….
bile ducts
Bile drains from the liver via the right and left hepatic ducts which join to form the…
common hepatic duct.
the common hepatic duct is joined by the _____ _____ that drains bile from the gallbladder.
cystic duct
This unity forms the…
common bile duct
The presence of food in the duodenum stimulates the gallbladder to do what
contract
Bile travels down the cystic duct to the common bile duct and then to the….
duodenum.
All of these ducts combine to form the biliary tract.
The main pancreatic duct joins the common bile duct at the __________ _________ (enlarged portion) which opens into the duodenum.
hepatopancreatic ampulla
where is the pancreas located
It lies horizontally across the posterior abdominal wall. It sits posterior to the stomach.
what 5 regions is the pancreas split into
uncinate process
head
neck
body
tail
Exocrine tissues of the pancreas release…
pancreatic juice
Pancreatic juice has two components:
Alkaline secretion
Enzyme rich secretion
what does the Alkaline secretion consist of
high bicarbonate
low enzyme content
what does the enzyme rich secretion consist of
contains the major enzymes involved in digestion
It is secreted as pre-enzymes that are activated in the gut so that they don’t digest the pancreas.
sympathetic stimulation _______ secretions parasympathetic stimulation ________ secretions
decreases
increases
Pancreatic juice is transported to the duodenum via the…
main pancreatic duct
the main pancreatic duct joins the common bile duct to form the
hepatopancreatic ampulla (known as the ampulla of vater)
Their entrance to the descending duodenum is controlled by what
the Hepatopancreatic Sphincter (of Oddi).
what is the peritoneum
a layer of connective tissue that covers the walls and all of the viscera of the abdomen
As the peritoneum moves off a structure of the abdomen it will create a reflection. There is a reflection or ‘flap’ of peritoneum that covers the abdominal contents called the
greater omentum
There is also a major reflection of the peritoneum from the posterior abdominal wall surrounding majority of the small intestines. This is known as
the mesentery
the wall of the digestive tract consists of the same 4 layers throughout
mucosa
submucosa
muscularis externa
serosa
the mucosa has three component layers
epithelium -This thin layer lines the lumen of the tube, it may be simple or stratified, squamous or columnar.
lamina propria - This is a layer of loose connective tissue.
muscularis mucosa - This consists of a thin layer of smooth muscle cells causing localised contractions in the mucosa.
submucosa
The submucosa is a layer of dense connective tissue that contains the submucosal plexus (part of the enteric nervous system)
muscularis externa
This section of the GI wall consists of two layers of smooth muscle: an inner circular and outer longitudinal layer. Waves of contraction and relaxation along these layers force food along the digestive tract, an action known as peristalsis.
serosa
This layer of epithelium forms part of the peritoneum.
small intestine:
The recessions between the villi are known as…
crypts
The epithelial surface of the villi is simple columnar. There are numerous microvilli on the surface of these cells that form a…
brush border
Four specialised cells are present within the epithelium of the villi
Absorptive cells: they secrete digestive enzymes and absorb nutrients.
Goblet cells: these produce mucus that lubricates and protects the epithelium from mechanical damage.
Granular cells: these secrete enzymes and protect epithelium from bacteria.
APUD cells: these cells produce endocrine secretions that regulate secretion and motility of the GI tract and associated glands.
The epithelium of the large intestine is not villous as in the small intestines. The epithelium of the large intestine is simple columnar and contains crypts but not villi.
Goblet and absorptive cells are present. APUD cells are present but sparse.
Goblet cells are more numerous here than in the small intestine and therefore the amount of mucus in the large intestine is greater.
Branches of the coeliac trunk supply the foregut structures which includes…
the stomach, superior duodenum, liver, gallbladder, spleen and pancreas.
The coeliac trunk immediately splits into what three smaller branches
common hepatic, left gastric and splenic arteries
what is the stomach supplied by
left and right gastric arteries and the left and right gastroepiploic arteries.
what is the superior duodenum supplied by
the superior pancreaticoduodenal artery.
what is the liver supplied by
the left and right hepatic arteries (branches of the hepatic artery proper).
what is the gallbladder supplied by
the cystic artery (branch of the right hepatic artery)
what is the spleen supplied by
the splenic artery
what is the pancreas supplied by
the superior pancreaticoduodenal artery and the pancreatic branches of the splenic artery.
The superior mesenteric artery supplies midgut structures. These include the…
small and large intestines from the inferior duodenum to the proximal half of the transverse colon.
The inferior pancreaticoduodenal artery arises from the superior mesenteric artery. this supplies…
the inferior part of the duodenum and pancreas
Numerous branches of the superior mesenteric artery form large loops, known as…
arcades
what does these arcades supply
the jejunum and ileum
what does the ileocolic artery supply
the terminal ileum, caecum, vermiform appendix and proximal ascending colon.
what does the right colic artery supply
the distal ascending colon
what does the middle colic artery supply
the distal transverse colon
The inferior mesenteric artery supplies the…
hindgut structures
what are the hindgut structures
the large intestines from the proximal transverse colon to the rectum.
what does the left colic artery supply
the descending colon
what is the sigmoid colon supplied by
the sigmoid arteries
what does the superior rectal artery supply
the proximal rectum
The blood that has flowed through the intestines is now full of amino acids and monosaccharides as well as any poisons and toxins that may have been absorbed.
Before it can be returned to the heart and lungs what happens to the blood
it is filtered by the liver
Blood drains from the capillaries of the intestines into the…
superior and inferior mesenteric veins
the superior and inferior mesenteric veins join the splenic vein to form..
hepatic portal vein
the hepatic portal vein carries deoxygenated blood from the intestines to the…
liver
