GASTRO Flashcards
what is the foregut
mouth to the proximal 1/2 of the duodenum
what is the midgut
the distal 1/2 of the duodenum to the right 2/3 of the transverse colon
what is the hindgut
the left 1/3 of the transverse colon to the anal canal
where is the foregut blood and nerve supply from
the coeliac trunk and the greater splanchnic nerve T5-9
what is the midgut blood and nerve supply
the superior mesenteric artery and the lesser splanchnic nerve T10-11
what is the hindgut blood and nerve supply
the inferior mesenteric artery and the least splanchnic nerve T12
what is McBurney’s point
it is 2/3 on the way from the umbilicus to the anterior superior iliac spine
what is McBurney’s point used to find
where the appendix lies in the abdomen
what are the horizontal lines used to divide the abdomen
the subcostal and intercristal plane
what is the vertical line used to separate the abdomen
the midclavicular line
what does the transpyloric plane of addison cross
it crosses at the level of T1
crosses the gallbladder, pancreas, pylorus, duodenal-jejunal flexure and kidneys
what are the three muscles found in the abdominal wall
- external oblique - runs inferomedially
- internal oblique - runs superomedially
- transverse abdominis
what do the muscles of the abdomen form at the midline
an aponeurosis - forms the rectus sheath
what are retroperitoneal organs
they sit directly on the posterior abdominal wall and are covered by the peritoneum on its anterior surface only
what are intraperitoneal organs
these are organs that care completely surrounded by peritoneum
what is the blood supply of the stomach
the greater curvature is supplied by the right and left gastroepiploic artery. the lesser curvature is supplied by the right and left gastric arteries (the left is directly from the coeliac trunk)
short gastric arteries supply the fundus which are branches of the splenic artery
what are the features of the stomach
there are two openings, the cardiac and the pyloric orifices
there are two curvatures the greater and lesser
there are two surfaces, the anterior and posterior
there is antrum, body, pylorus, fundus
what are the basic features of the duodenum
it is a C shape, and there are 4 parts; the superior, descending, inferior and ascending. the main section is the descending curve where you have bile duct emptying into the duodenum. this is via the major papilla and the flow is controlled by the sphincter of oddi
what are the basic features of the large intestine
there is the caecum, ascending, transverse, descending, sigmoid colon, rectum and anus.
what is the blood supply to the ascending colon
the right colic artery from the superior mesenteric artery
what is the blood supply for the transverse colon
proximal 2/3 is the middle colic from the superior mesenteric. distal 1/3 is from the inferior mesenteric
what is the blood supply for the descending colon
the left colic artery from the inferior mesenteric artery
what is the blood supply for the sigmoid colon
the sigmoid arteries from the inferior mesenteric artery
what is the epithelia found in the oesophagus
stratified squamous epithelium
what is the epithelium found in the stomach
simple columnar epithelium
what are the three muscle layers of the stomach
longitudinal, oblique and circular
how many muscle layers are there in the GI system
there are normally two, longitudinal and circular. the exception for this is in the stomach
what are brunners glands and where are they found
they are only found in the duodenum, and they secrete alkaline mucus which neutralises chyme
from the top the bottom what are the structures in the GI tract
pharynx (naso/laryngo), upper oesophagel sphincter, Oesophagus, cardiac notch, lower oesophageal sphincter, stomach, pyloric sphincter, duodenum, jejunum, ilium, coecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anus
what are the three arteries that come off the coeliac trunk
common hepatic, left gastric and splenic
what is present on the inside of the stomach
Rugae which are folds in the stomach that increase its surface area. it allows for expansion
what are the unique features of the colon
teniae coli, haustra and epiploic appendages
what is the epiploic foramen of winslow
it is between the stomach and the liver and it is a pocket into the retroperitoneal space
what occurs in the voluntary phase of swallowing
when food is being chewed and then pushed to the back of the oropharynx by the tongue
what happens during the first phase of involuntary swallowing
the nasopharynx closes and the hyoid bone elevates. the epiglottis is closed and the pharynx becomes shorter and wider through longitudinal muscle contraction
what happens during the second phase of involuntary swallowing
food passes from the mouth to the oesophagus, and the upper oesophageal sphincter opens. there is sequential movement of food down and there is contractions of the circular muscle.
what is the cardiac notch for
it helps to prevent oesophageal reflux of acid
what happens in GORD
the epithelium of the lower oesophagus changes from stratified squamous to simple columnar epithelium (metaplasia)
what nerves are involved in the gag reflex
CN9 - sensory
CN10 - causes reflex
how much saliva on average does one produce a day
800 - 1500mls
what are the functions of saliva
lubrication, taste, cephalic digestion, oral hygiene
what are the contents of saliva
water, mucus, antibodies, enzymes (amylase)
describe the parotid gland and its secretions
it is the main salivary gland when stimulated. it gives off serous saliva via Stenson’s duct
what nerve supplies the parotid gland
the glossopharyngeal nerve
what structures pass through the parotid gland
the facial nerve and the external carotid artery
describe the submandibular gland and its secretions
it is a mixed saliva secretion (serous and mucous) via the Wharton’s duct.
It has serous demilunes (serous acini forming crescents around mucous acini)
it is continuously secreting
what nerve supplies the submandibular gland
the facial nerve
describe the sublingual gland
it is the smallest out of the main glands, and secretes mucous secretions via Wharton’s duct. it is continuously secreting
anterior to the submandibular gland
what nerve supplies the sublingual gland
the facial nerve
what secretions do the minor salivary glands produce
mucous secreting except the Von Ebner gland which is serous
what is the difference between serous and mucous secretions
serous contains water and alpha amylase and histologically looks dark with a small central duct
mucous contains water and mucous and histologically looks light with a large central duct
what does parasympathetic innervation of salivary glands do
it stimulates saliva production
what are the cell layers in the GI tract
Mucosa
Submucosa - contains the submucosal plexus (ENS)
muscularis externa - myenteric plexus
serosa
how many layers are in the muscularis externa
2 layers the inner circular and the outer longitudinal
- except in the stomach
how many muscularis externa layers are there in the stomach
3
inner oblique, middle circular and outer longitudinal
what cells are present at the cardiac notch of the stomach
foveolar cells - mucous producing cells
what cells are found in the fundus of the stomach
parietal cells, chief cells and ECL cells
what cells are found in the body of the stomach
G cells, D cells and I cells
what do parietal cells produce
HCL and intrinsic factor
what do chief cells produce
pepsinogen
what do ECL cells produce
histamine
what do G cells produce (in stomach)
gastrin
what do D cells in the stomach produce
somatostatin
what do I cells in the stomach/duodenum produce
CCK
where are S cells found and what do they produce
they are in the duodenum and produce secretin
what are the functions of the stomach
digest and store food, activates enzymes, kills microbes, secretes intrinsic factor needed for B12 absorption
how is gastric acid produced in the parietal cells
In the parietal cell CO2 and H2O combine to make H2CO3. this then dissociates into HCO3- and H+.
HCO3- is basolaterally exchanged for Cl- into the cell. H+ is actively transported out the H+K+ATPase pump apically. Cl- diffuses out the apical side of the cell with K+ where it combines with H+ in the stomach to form HCL
what are the phases of gastric acid secretion
- cephalic phase
- gastric on phase
- gastric off phase
- intestinal phase
what happens during the cephalic phase of gastric acid secretion
this is initiated by sight, smell, thinking of food. Ach via the parasympathetic NS increases gastrin and histamine release as well as directly acting on parietal cells to increase HCL secretion
what happens during the gastric on phase of gastric acid secretion
food in the stomach - stimulatory
the stomach distends and there are amino acids found in the stomach. this triggers an increase in gastrin release. this activates more histamine release as well as acting on parietal cells to increase HCL secretion. there is an increase in H+K+ATPase pumps
what happens during the gastric off phase of gastric acid secretion
when there is a low stomach pH and large stomach distension it triggers D cells to produce somatostatin which reduces HCL release
what happens during the intestinal phase of gastric acid secretion
there is inhibition due to the presence of fatty acids and amino acids, low pH and high duodenal distension.
this causes enterogastrone release which induces secretin and CCK to be released
what are 4 things that can cause a peptic ulcer
helicobacter pylori, NSAIDS, chemicals and gastroma
how does helicobacter pylori cause peptic ulcers
helicobacter produces ammonia from urea which is toxic to the mucosa of the stomach
how do NSAIDs cause peptic ulcers
they inhibit COX-1 which is required for prostaglandin production. prostaglandins are needed to make mucous
what is the treatment for a peptic ulcer
proton pump inhibitors
H2 receptor antagonists
how is pepsinogen activated
after it is released it is converted into pepsin by itself as well as HCL
what is gastric motility
peristaltic waves in the stomach which are slow at the fundus and much harder in the antrum. they are about 3 every minute
what causes stomach contractions
interstitial cells of cajal which are in the longitudinal muscle layer
what slows down duodenal emptying
low pH, increased fatty acids, increased amino acids, distension, hypertonicity
what is gastroparesis
duodenal emptying is too delayed and food rots in the stomach
what is the GI water content (on average)
9L
what secretions make up for water content in the GI tract
intestines, saliva, bile, stomach juices and pancreatic juices
what do the alpha, beta and gamma cells of the pancreas produce
alpha - glucagon
beta - insulin
delta - somatostatin
how much water is reabsorbed into the body
98% - about 200mls into the stool
how much water is absorbed in the jejunum, ilium and colon
5500mls - jejunum
2000mls - ileum
1300mls - colon
what ion is the most abundant in chyme
sodium
what vitamins are absorbed in the jejunum
B and C
what vitamins are absorbed in the ileum
A, D, E, K, B12
what is the process of carbohydrate metabolism
starts in the mouth with alpha amylase.
it continues in the duodenum with pancreatic amylase were about 95% starch broken down. this makes oligo/disaccharides. there are membrane bound oligo/disaccaridases which break them down to monosaccharides - glucose, galactose and fructose
how are monosaccharides absorbed in the SI
glucose and galactose via a glucose sodium symporter - SGLT1
fructose is absorbed via facilitated diffusion - GLUTs
all three leave the basolateral side of cells via GLUT2
describe the process of protein metabolism
digestion starts in the stomach with pepsin. most occurs in the duodenum. the pancreas secreted inactive endo and exopeptidases (trypsinogen, chymotryposinogen and carboxypeptidase) which are activated in the duodenum. these then cut peptides mid chain and end of chain respectively.
membrane bound aminopeptidases break down the smaller chains
how are proteins absorbed in the GI tract
they are absorbed via secondary active transport with sodium (or H+ if the fragments are small enough)
describe the process of fat metabolism
starts in the mouth. in the duodenum they are emulsified by bile salts, preventing reaggregation. lipase and colipase bind to the droplets converting the triglycerides to monoglycerides and fatty acids. with the bile salts these are packaged into micelles and transported to the intestinal cell membrane
how is fat absorbed in the GI tract
micelles break down at the cell membrane and the monoglycerides and fatty acids diffuse into the cell. once in the cell they reaggregate into vesicles called chylomicrons. these get exocytosed into lacteals of the lymphatic system
what are the fat soluble vitamins
A, D, E, K
what are the water soluble vitamins
B, C
what are the properties of vitamin A and what is it needed for
called retinol or rhodopsin it is absorbed as a lipid and stored in the liver in ITO cells or in the space of disse. it is needed for night vision
what is a source of vitamin A and what happens if you are deficient in it
carrots
night blindness
what are the properties of vitamin D
known as calciferol. it is required for calcium and phosphate intestinal absorption. it is stored in the liver
- active form of vitamin D is Vitamin D3
how is vitamin D activated in the body
UV converts 7 dehydrocholesterol to cholecalciferol. in the kidney this is converted to vitamin D3
what is the form of vitamin D found in supplements
vitamin D2
what a source of vitamin D and what does deficiency cause
UVb light
bone issues such as rickets
what are the properties of vitamin E
it is an antioxidant. it is found in nuts and seeds and is stored in the liver
what are the properties of vitamin K
it activates clotting factors. it is found in plants as well as in synthetic forms (K3 and 4). deficiency leads to bleeding disorders
what are the clotting factors that vitamin K activates
10, 9, 7, 3
remember 1973
what are the properties of vitamin B12
required for cell metabolism and energy. it is indirectly related to DNA synthesis due to folate.
how is vitamin B12 absorbed
it initially binds to the R protein of transcobalamin 1 in the stomach. in the duodenum it dissociates from this and binds to intrinsic factor
what is a source of vitamin b12 and what happens if you are deficient in it
found in eggs and poultry.
deficiency leads to pernicious anaemia
what are the properties of vitamin C
required for immune system function, Fe absorption and is an antioxidant. found in fresh fruit and veg and a deficiency leads to scurvy
what are the two forms of iron found in the body
transferrin - how its transported in the blood
ferritin - how its stored in the liver
where is copper stored
in the liver
