GI Flashcards
5 functions of the stomach
- disolve and continue digestion
- secrete pepsinogen/proteases
- activate the proteases
- kill microbes- HCL
- regulate emptying into the duodenum
- store and mix food; mechanical digestion
- lubrication
- priduce muous for mucosal defense against proteases and HCL
what cell secretes HCL in the stomach
parietal cell
apart from HCL, what else does the parietal cell secrete?
intrinsic factor, to help v. b12 absorption
what cell secretes pepsinogen in the stomach
chief cell
what is pepsinogen an example of?
a zymogen
what cell secretes pepsin
none. always secreted as the pepsinigen zymogen
is pepsin essential for protein digestion
no. only does 20% of total protein digestion. it only accelerates protein digestion
5 factors that decrease gastric emptying in the DUODENUM
- increased amino acids
- increased fat (most effective chemical stimulus)
- increased acidity
- increased duodenal distension
- increased hypertonicity in the duodenum
what 2 factors follow on from the duodenal factors to reduce gastric emptying
- increased neural stimlation of receptors that then act via short (enteric) neural pathways on the stomach & via long neural pathways on the parasympathetic and sympathetic nervous system
- increased release of enterogastrones
name 2 enterogasteones
cck, cholecytokinin
secretin
what is the main parasympathetic neurotransmitter acting on the stomach
acetylcholine
give one hormone and one paracrine agent that increases HCL production in the stomach
Hormone= gastrin
Paracrine agent= histamine
in terms of peptic ulcers, what is an ulcer
a breach of the mucosal surface
give 4 causes of peptic ulcers
- helicobacter pylori
- NSAIDs
- Gastrinomas- ie malignancies of G cell
- chemical irritants: alcohol, bile salts, dietary factors
3 things to treat peptic ulceration by helicobacter pylori
- 1 antibiotic
- another antibiotic
- proton pump inhibitors
what do H2 receptor antagonists do in the parietal cell
block the action of histamine, so reducing HCL production
a disease that involves delayed gastric emptying
gastropAresis
what is exchanged for cl- in the basolateral membrane of the parietal cell, in HCl secretion, to achieve electrical neutrality of the blood but also causes the alkaline tide
HCO3-
how is the alkaline tide affected by excessive vomiting and why
it is made more alkaline. because loss of H+ in the stomach lumen to vomiting reflexively increases the HC03- secretion into the blood at the basolateral membrane. so increasing the alkalinity of the blood leaving the stomach.
how do prostaglandin analogues stop NSAIDs like aspirin, causing peptic ulcers
provides prostaglandins ( so no need to rely on cyclo-oxygenase 1 to synthesise prostaglandins), so mucous secretion can still be stimulated by the pristaglandins, to act as a barrier agaist HCl and pepsin
what is the inherent rate of gastric motility by longitudinal muscle in the fundus and body?
3 contractions per minute. increased by the vagus nerve
which muscle layer is outermost in the stomach? longitudinal or circular
circular
what 2 substances are released by the enteric nerves to mediate stomach muscle relaxation, receptive relaxation on swallowing
nitric oxide and serotonin
where in the stomach are parietal cells most abundant
body and fundus
where in the stomach are chief cells most abundant
body and fundus
where in the stomach does the most contraction take place due to a thicker muscle layer
the antrum (between the body and pyloris)
which enteroendocrine cell secretes:
- gastrin
- somatostatin
- histimine
- G cells
- D cells
- enterochromaffin cells (ECL cells)
what cells secretes mucous in the stomach
goblet cells
where in the stomach are goblet cells most abundant
cardia and pylorus. which also lack parietal and chief cells
what zymogen is secreted into the small intestine, by the pancreas, to digest polypeptides and what is its active form
trypsinogen; trypsin
in the normal, free of ulcers, state, how does the stomach protect against HCl and pepsin. namw 4
- alkaline mucous
- replacement of damaged epithelial cells of the stomach
- tight junctions between the epithelial cells
- feedback loops that ensure mucous secretion is always sufficient
out of the: cephalic, gastric and intestinal phase of acid secretion in the stomach, which one is purely inhibitory and what substances cause this
intestinal phase; cck (cholecytokinin) ans secretin
what does secretin do in the intestinal phase of inhibiting HCl release
inhibits gastrin release, promotes somatostatin release
what part of the small intestine is prone to peptic ulceration
the duodenum just beyond the pyloric sphincter of the stomach
what artery can duodenal peptic ulcers erode into and cause to bleed
the gastroduodenal artery
give 3 structure in the small intestine and not the large intestine
plicae circularis, peyer’s patches, fat in the mesentery of the small bowel
where in the small intestine does most absorption take place
the jejnum
what are peyers patches
small submucosal lymph nodes in the wall o the ileum
in the intestine, which layer of muscle is on the outside
longitudinal muscle
is the jejnum inta or extraperitoneal?
intra
what marks the end of the small intestine
the iliocecal valve
what are the 4 parts of the duodenum
superior, descending, horizontal, ascending
at which division of the duodenum is the major papilla
the descending duodenum
where does the large intestine start
the iliocecal valve, with the ioliocecal orifice in between
are the ascending and descending colon intra or extraperitoneal?
extraperitoneal
what is the longidudinal muscle in 3 bands in the colon?
taenia coli
at what point along the colon do the taenia coli become a continuous layer of longitudinal muscle
the recto-sigmoid junction
give 3 things in the large intestine not in the small intestine
haustrations, taenia coli and appendices epiploicia
what do the appendices epiploicia mark?
where the blood vessels penetrate the bowel wall, to supply the mucosa and submucosa.
what is at mcburney’s point
the base of the appendix
why do different people get different symptoms with appendicitis
because the appendix is mobile and so can hit alot of different structure when inflamed depending on the position of its apex
where does the hindgut end
the distal part of the anal canal
give 3 things that the ileum has that the jejnum doesnt
peyer’s patches, more arcades, shorter vasa recta
give 3 divisions of the superior mesenteric artery
the middle colic artery, the right colic artery, the iliocolic artery
what artery vascularises the ascending colon
the right colic artery, a branch off the superior mesenteric
what are the 2 divisions of the right colic artery
ascending and descending
what are the 2 branches of the the iliocolic artery
superior and inferior
what does the inferior branch of the iliocolic artery supply?
the structures of the right iliac fossa. it has 4 branches, ileal branch supplying the distal ileum, the coecal branch supplying the caecum, the appendicular branch supplying the apendix and the colic branch to supply the start of the ascending colon (which is then continued by the right colic artery and the descending branch of the middle colic artery)
what artery off the abdominal artery supply the small bowel
the superior mesenteric artery
what does he middle colic artery supply
the proximal 2 3rds of the transverse colon
hat part of the pancreas does the superior mesenteric artery and vein travel over
the uncinate process
at what level does the inferior mesenteric artery arise form he abdominal aorta
L3
what part of the large intestine does the inferior mesenteric artery supply
left colic flexure to to the upper part of the rectum, so including the descending colon, sigmoid colon and part of the rectum
give the 3 divisions of the inferior mesenteric artery
left colic artery, the lower left colic artery, sigmoid artery
what artery forms the connection between the superior and inferior mesenteric arteries
the middle colic artery
what 2 horizontal lines is the flank/lumbar region of the abdomen between
subcostal plane and transtubercular plane
what are the 3 abdominal regions below the intetubercular plane
right and left iliac and hypogastric/suprapubic
what 2 pints does the intertubercular plane join?
the tubercles of the iliac crests
what does the subcostal plane join
the lowest part of the costal margins on both sides
what vertebra is on the same plane as the subcostal plane and what does it demarcate
L2, the emergence of the superior mesenteric artery and the lower limit of the spinal cord in the adult
at what vertebral level does the abdominal aorta bifurcate and what plane/ line is here
L4. the intertubercular plane
where is the intercristal plane and what part of the pelvis does it run through
the junction between L4 and L5. the most superior portion of the pelvis posteriorly
why is the intercristal plane relevant?
it is used during lumbar puncture and epidural anasthesia
the transpyloric plane of addison is located half way between what 2 landmarks
the jugular notch (top of the manubrium) and the upper border of the pubic symphysis
name 3 structures that line on the transpyloric plane
the pyrloris of the stomach, pancreas, and the gall bladder
at which costal cartilage and vertebra is the transpyloric plane
9th and L1
bcburneys point is a point 2 3rds of the way along a line that joins the umbilicus to the anterior superior iliac spine on the or right of the body?
right as the appendix is in the right iliac fossa
in a thin patient, at what level is the umbilius, and why is this point special?
L3. emergence of the inferior mesenteric artery from the abdominal aorta
in the lower quarter of the rectus abdominis, which side do the aponeuroses pass?
anterior only
what name is given to the 3 aponeurosis that act to enclose the rectus abdominis
the rectus sheath
what is the linea alba
this is in the middle of the abdomen formed by the meeting of the aponeuroses of: external oblique, internal oblique and transverse abdominis
what vertebra is the xiphoid considered to be at
the 9th thoracic vertebra
what vertebral level is the posterior superior iliac spine at?
S2
what levels of the anterior rami innervate the abdominal mucles
T7-L1
what does rectus abdominis muscle attach to superiorly
the xiphoid process
what are the 5 functions that the abdominal muscles can be involved in
micturition, giving birth, assisting in breathing, vomiting, dificaction, protection of the abdominal viscera
what is an aponeurosis
a flat tendinous sheath that continues on from a muscle
what muscle is inferiorly attached to the tubis bone and in not present in everyone in the abdomen and what is its presumed action
the pyramidalis muscle. thought to tense the linea alba
how many stages of deglutition are involuntary
2
what is the mainn step of stage one of swallowing
pushing of the food in the mouth against the hard palate towards the oropharynx by the action of the tongue
what stage of swallowing is brought to consciousness and why
stage 1. so that we can use our memory to decide whether we should swallow the food if we’ve had it before
what is the role of the masseter and buccinator muscles in the 1st stage of swallowing
pushing the food away from the vestibules, towards the oral cavity/tongue
why must the mouth be closed in the 1st stage of swallowing
to have a rigid floor that the tongue can act against, as it is the movement of the tongue upwards and backwards that forms this stage
at which anatomical position does swallowing now become involuntary
once past the oropharyngeal isthimus
what is another name for the 2nd stage of deglutition
the pharyngeal stage
what must relax to allow for the 3rd stage of deglutition to start and how does this take place?
the superior oesophageal sphincter. relaxation of the inferior constrictor
what closes off the nasopharynx in the 2nd stage of swallowing to prevent food going the wrong way?
the soft palate
is the hyoid bone depressed or elevated in the 2nd stage of deglutition? and what group of muscles are responsible for this
elevated. the suprahyoid muscles
which is the fastest phase of swallowing and why
the pharyngeal phase because you must stop breathing for it
what is the sequence of impulses that results in the raising of the soft palate and uvula in the 2nd stage of swallowing
receptors in the oropharynx are stimulated b y food there, these then send impulses to the deglutition centre of the medulla, this then send impulses back to cause contraction of muscles that elevate the soft palate and uvula, closing the nasopharynx
what is the 3rd stage of swallowing called
the oesophageal stage
does the hyoid bone rise or depress in the 3rd stage of deglutition
depresses, such that tract below it is made wider and shorter
what is peristalsis in relation to deglutition
a continued and coordinated contraction of the longitudinal and circular muscle of the muscularis externa that pusshes the bolus towards the stomach
in peristalsis, which muscle layer contracts above the bolus?
circular
which sphincter is a physiological rather than anatomical sphincter? the lower oesophageal or pyloric one?
the lower/ inferior one
what types of gland are in the oesophagus and what do they mainly secrete, why?
seromucous. mucous, to act as a lubricant for the bolus
are the suprahyoid or infrahyoid muscles involved in the third stage of deglutition
infrahyoid
name 4 infrahyoid muscles. what do these do during the 1st and 3rd stage of swallowing
sternothyroid, sternohyoid, omohyoid, thyrohyoid. they fix the hyoid bone, so allowing opening of the mouth by the suprahyoid muscles; depress the hyoid bone in the 3rd stage
name the suprahyoid muscles in order from top to bottom
styloglosus, genioglossus, geniohyoid, mylohyoid, digastric, stylohyoid
what plexuses innervates the constrictors
pharyngeal plexus, which involves the vagus and accessory CNs (10 and 11) that innervate the middle and inferior constrictors specifically
((5 does superior))
the levator muscles is what helps to raise the soft palate in the 2nd sage of swallowing, what cranial nerve innervates it?
5, V3
which of the tongue muscles is not innervated by the hypoglossal nerve (CN 12)
palatoglossus. it is innervated by the vagus nerve instead
contraction of what 2 muscles of the tongue cause the fauces (openings either side of the uvula) to close/ move closer together
palatoglossus and palatopharyngeus. both of which are innervated by the vagus nerve!
at what level along the vertebra does the forgut change from being called the pharynx to the oesophagus and why
c6 because the pharynx has both striated voluntary muscle and non striated smooth muscle, but the oesophagus only has smooth muscle
the gag reflex is between which 2 cranial nerves
9 and 10
what is choking due to?
a failure to coordinate actions, so muscles and nerves aren’t coordinated. eg due to intoxication or brainstem lesions
through which membrane is a tracheostomy done and what structure does this avoid
cricothyroid membrane. the isthmus of the thyroid gland
GERD/GORD is gastroeosophageal reflux disease and what is it caused by? what pathology can it then cause? and what is the change occurring?
the lower oesophageal sphincter not closing. Barrett’s syndrome, due to dysplasia of the epithelium, a change from stratified squamous epithelium to simple columnar.
what is given to treat heartburn
over the counter histamine, H2 blockers
what are the layers of fascia called in order from behind the constrictors
buccopharyngeal, prevertebral and retropharyngeal fascia.
where does the superior constrictor originate from
medial pterygoiod plate and pterygomandibular raphe
where does the middle constrictor originate from?
the hyoid bone
what are the 2 inferior constrictors
cricopharyngeus, thyropharyngeaus
what fascia lines the inner surface of the constrictors and where does it rise up to above the constrictors
the pharyngobasilar fascia. the base of the skull
what is the weak point in the inferior constrictor and why is it relevant
killian’s dehisscence. food can form in a pouch of mucosa if it goes through this weakness- called the pharyngeal diverticulum
what nerve wraps around the stylopharyngeaus muscle
the glossopharyngeal nerve
what action does the hypoglossal muscle cause to the tongue
depresses the tongue
what nerve and artery pierce the thyroHYOID membrane to get to the larynx
the internal laryngeal nerve and the superior laryngeal artery
what is the superior laryngeal artery a branch off?
the superior thyroid artery, which is a branch off the external carotid artery itself
which tracheal ring cartilages are behind the thyroid gland’s isthmus?
2nd to 4th
what is the inferior thyroid artery a branch off? and where did this come off originally
the thyrocervical trunk, which is a branch off the subclavian artery
above what anatomical landmark is innervation by the internal laryngeal nerve and below it is innervation by the external laryngeal artery?
the vocal cords
does the right recurrent nerve do sensory or motor?
motor
what is the superior, middle and inferior thyroid veins a branch off
superior and middle=internal jugular vein. inferior= brachiocephalic
what is the uvula a continuation of?
the soft palate
what 3 muscles attach to the thyroid cartilage (extrinsic ones)
thyropharyngeus, sternothyroid, thyrohyoid
when stretched, so tension, of the vocal ligaments, is lower or higher pitch sound produces?
higher
what joint does the cricothyroid muscle operate?
the cricothyroid joint (a synovial joint)
what intrinsic muscle attaches to the side of the vocal cords?
the thyroarytenoid muscle, part of it is called the vocalis muscle and actually inserts all the way along the vocal cords and is to adjust the tension of the fibres, it makes small adjustments
what action does the transverse arytenoid muscle produce and how does this affect the vocal cords
adducts the arytenoid cartilages. widens the space between the vocal cords, so slackens them, leading to lower pitch sounds
what nerve innervates the transverse arytenoid muscle
right recurrent laryngeal nerve
what muscle is the only one that adducts the vocal cords? so opening the rima glottidis
the lateral cricoarythenoid muscle
what 3 muscles abduct the vocal cords
oblique and transverse arytenoid and posterior cricoarytenoid
