Gastro-Intestinal Flashcards
What are the main functions of the stomach?
Store food
Mix and disrupt
Secrete acid and enzymes
What are the 4 main processes of the digestive tract?
Secretion, digestion, motility and absorption
What are the 4 parts of the stomach?
Cardiac, fundus, body, pyloric antrum
How is reflux prevented?
Acute angle
Lower oesophageal sphincter
Positive intra abdominal pressure compresses the walls
What are the cell layers that make up the alimentary canal?
Mucosa - epithelium, connective tissue and smooth muscle
Sub mucosa
Muscularis external
Serosa/adventitia
What is the muscle and nerve supply for mastication?
Masseter
Trigeminal nerve
What are the functions of saliva?
Lubricate
Start digesting carbohydrates
Protection - moist, wash teeth and alkaline
What are the components of saliva?
Water, alkali, electrolytes, enzymes, mucus, bacteriostats
What is xerostomia and the consequences of it?
Low saliva production
Can only eat moist food and teeth/mucosa degrades very quickly
What are the 3 salivary glands and the type of saliva they produce?
Parotid - serous - high enzymes low mucus
Sub-lingual - mucous - high mucus no enzymes
Submandibular - mixed - produce 70% of saliva
What do the acinar cells and ductal cells do?
Acinar secretes saliva and ductal cells modify the composition
What is the effect of increased saliva production?
More produced = less modified so
Higher volume, alkalinity and enzyme levels
Less hypotonic
Outline the process of swallowing
Voluntary phase - bolus formed and moved to pharynx
Reflex - pressure receptors stimulated causing: respiration inhibited, raise larynx, close glottis, open upper oesophageal sphincter, rapid peristaltic wave and opening of lower oesophageal sphincter
What are some potential causes of dysphagia
Motility problems - achalasia
Obstruction - tumor
What does lateral folding and craniocaudal folding accomplish?
Lateral - ventral body wall and tubular primitive gut
Craniocaudal - creates pockets
What are the derivatives of the foregut? What is its blood supply?
Oesophagus, stomach, pancreas, liver, gall bladder and duodenum
Celiac trunk
What are the derivatives of the midgut? What is its blood and nerve supply?
Duodenum, jejunum, ileum, cecum, ascending colon and transverse colon
Superior mesenteric artery/vein
Vagus nerve/superior mesenteric ganglion and plexus
What are the derivatives of the hind gut? What is its blood and nerve supply?
Transverse colon, descending colon, sigmoid colon, rectum, upper anal canal, lining of bladder and urethra
Inferior mesenteric artery/vein
Pelvic nerve/inferior mesenteric ganglion and plexus
What does the splanchnic and somatic mesoderm become?
Somatic - muscle and fasciae of the abdominal wall
Splanchnic - smooth muscle of the gut wall
Describe the muscle and fascia of the abdominal wall
Lateral folding creates linea alba in the middle
External oblique, internal oblique and transversus abdominis. Rectus abdominis anteriorly.
Deep is transversalis fascia. Superficial is superficial fascia and skin
What do the dorsal and ventral mesenteries do?
Dorsal - attach entire gut to roof of abdominal cavity
Ventral - attach foregut to the floor
What do the left and right sac become?
Greater peritoneal sac
Lesser peritoneal sac
What is the greater omentum derived from? And the lesser omentum? And what do they connect?
Greater - dorsal mesentery. Greater curve to transverse colon
Lesser - ventral mesentery. Lesser curve to liver
What does retroperitoneal mean and give an example of some organs which are
Never in the peritoneal cavity and never had a mesentery. Aorta, vena cava and kidney
What does secondary retroperitoneal mean and give an example of organs which are
Began development in the peritoneum but lost mesentery. Ascending and descending colon and duodenum
What are the three vertical muscles of the abdominal wall?
External oblique, internal oblique, transversalis
What are the two flat muscles of the abdominal wall?
Rectus abdominis and pyramidalis
What is the rectus sheath?
The aponeurosis of the vertical muscles combine at the linea alba and enclose the flat muscles
What are the layers of the abdominal wall from superficial to deep?
Skin
Superficial fascia
Muscles and their associated fascia
Peritoneum
What is the arcuate line?
The point where posterior wall of the rectus sheath disappears
What are the 3 main types of incision?
Midline - through linea alba
Transverse - through the oblique muscles
Grid iron - split the muscle fibres
What is a Meckel’s diverticulum?
Remnant of the vitelline duct
2% of the population, 2” in length, 2:1 male/female ratio, found in under 2’s
What are the following conditions: vitelline fistula, omphalocoele, gastroschisis?
Direct communication between umbilicus and GI resulting in faecal matter out of the umbilicus
Persistence of physiological herniation
Gut tube outside body with no covering
What is a hernia?
Abnormal protrusion of an organ or fascia through the walls of the cavity that contain it
What are the 3 main types of herniation?
Inguinal
Femoral
Umbilical
What are the borders of the inguinal canal and what does it normally contain?
Lateral - deep inguinal ring
Medial - superficial inguinal ring
Anterior and superior - aponeurosis of external oblique
Posterior - transversalis fascia
Inferior - inguinal ligament
Males - spermatic cord and ilioinguinal nerve
Females - round ligament and ilioinguinal nerve
What is the difference between a direct and indirect inguinal hernia
Direct goes through Hesselbachs triangle. Indirect goes through the deep ring
What are some complications of hernias?
Strangulation - poor blood supply
Incarceration - not easily reversed
What are the functions of the stomach?
Store food
Digest food
Break food down into chyme
What are the “attack” and “defence” secretions by the stomach?
HCl and proteolytic enzymes
Mucus and HCO3-
What are the 4 cells in gastric pits and what do they produce?
Parietal - acid
Chief - enzymes
Endocrine - gastrin
Neck - mucus
Outline the method of acid production and secretion
The mitochondria produces H+ and OH- ions from water in the mitochondria. OH- becomes HCO3- and is secreted into the blood. H+ enters the stomach via a proton pump using ATP
What effects acid secretion?
Gastrin - increased by peptides, ACh. Decreased by acid
Histamine - increased by gastrin and ACh
ACh - increased by CNS and distention
Outline the 3 phases of control
Cephalic - detect and ingest food. Autonomic
Gastric - food reaches stomach and via pH rising, stomach distending and peptides being released more acid is produced
Intestinal - as stomach empties gastrin antagonists and pH lowering reduces acid secretion
How are the stomachs defences promoted?
Prostaglandins which are stimulated by the same mechanisms stimulating acid secretion thus matching attack and defence
What are some problems with stomach defences and what is the result?
Alcohol - dissolve mucus
H. pylori
NSAIDS - inhibit prostaglandins
Leads to peptic ulcers
How can you reduce acid secretion?
Proton pump inhibitors - omeprazole
Histamine antagonists - cimetidine
What inhibits stomach emptying?
Fat, hypertonicity and low pH in the duodenum
Explain the primary intestinal loop and it’s function
The midgut herniated into the umbilical cord to accommodate the growing liver and undergoes 3x 90 degree anticlockwise rotations around the SMA resulting in the final positions of the midgut.
What are some malformation problems?
Incomplete - left sided colon
Reverse - transverse colon posterior to duodenum
Volvulus - abnormally twisted bowel = blockage, strangulation and ischaemia
What is the purpose of recanalisation and what can its failure result in?
Gut cell growth is so rapid in the oesophagus, bile duct and small intestine the lumen can become obliterated
If it fails you can get atresia or stenosis
What is the difference between an umbilical hernia and omphalocoele?
Umbilical hernia has a skin covering
How is the anal canal and urogenital canal separated?
Urorectal septum separates them
What are the differences above and below the pectineal line?
Above - IMA, columnar epithelium, parasympathetic, internal inguinal nodes, stretch sensation only
Below - pudendal a, stratified squamous, sympathetic, superficial inguinal nodes, pain/touch/temperature sensation
Where is visceral foregut, midgut and hind gut pain felt?
Epigastric, peri umbilical, suprapubically
How is gastric reflux normally prevented?
Lower oesophageal sphincter
Abdominal pressure>thoracic pressure
Right crus of diaphragm
Oblique entrance angle
What are the symptoms of acid reflux and when are they worse?
Dyspepsia - heart burn
Lying down and hot drinks
How do is reflux managed?
Lifestyle - stop smoking, weight loss, reduce alcohol
Medicate - antacids, PPIs, H2 antagonist
What is an ulcer?
Break in the superficial epithelial cells down to muscularis mucosa
Where are stomach ulcers and duodenal ulcers most likely to be found?
Lesser curve
Duodenal cap
What can cause peptic ulcers and why?
NSAID - inhibit prostaglandins which produce the defences
What are the symptoms of peptic ulcers?
Recurrent burn in epigastric pain worse at night and when hungry
Nausea
Weight loss
How are ulcers managed?
PPI - omeprazole
H2 antagonist - cimetidine
Antibiotics - clarithromycin H. Pylori
Stop using NSAIDS
What type of bacteria is H. pylori? How is it able to survive in the stomach?
Gram negative aerobic
It has urease which produces ammonia to neutralise the acid
How is H. pylori diagnosed?
IgG
Urea breath test
Biopsy
In what state does Chyme leave the stomach and how is that corrected?
Acidic - HCO3- added
Hypertonic - H2O added
Partly digested - enzymes and bile acids added
What do the exocrine glands of the pancreas produce? Which part produces which?
Alkaline juice - ducts
Enzymes - acinar
What stimulates the release of enzymes and alkaline juice respectively?
CCK
Secretin
What are the four main functions of the liver?
Energy metabolism, detoxification, plasma proteins and bile
Describe the blood and bile flow in the liver
Blood enters from the hepatic portal vein into sinusoids lined with hepatocytes into the central vein. Bile enter canaliculi and flows to the bile duct
What are the two components of bile?
Bile acid dependent - bile acids and pigments
Bile acid independent - alkaline juice
What do bile acids do?
Help with fat digestion by emulsifying them to increase surface area
What does the gall bladder do?
Store recycled bile and concentrate it. When CCK is their the muscle contracts emptying it
What are the defences the GI has to toxins?
Innate - physical and cellular
Adaptive
List the physical defences
Sight, smell, memory, saliva, gastric acid, mucus, anaerobic, small intestinal secretions, peristalsis/segmentation
What conditions can arise due to salivary problems?
Xerostomia - mucus and teeth degradation
Parotitis - staph aureus
What can cause achlohydria and what conditions can then develop?
PPI, pernicious anaemia
Shigellosis, cholera, salmonella, clostridium difficile
How is the small intestine protected?
Bile, enzymes, anaerobic environment, epithelial shedding and segmentation
What can survive gastric acid?
TB - resist acid
H. Pylori - protective ammonia
Hep A
Polio
What are the cellular defences?
Neutrophils, macrophages, natural killer cells, mast cells, eosinophils
What can cause liver failure?
Viral hepatitis Alcohol Drugs Solvent Mushrooms
What are the GIs adaptive defences?
B lymphocytes
T lymphocytes
Lymphatics - MALT/GALT
Explain mesenteric adenitis
Right iliac fossa pain - adenovirus
Mistaken for appendicitis
Explain appendicitis
Obstruction of appendix leads to stasis and infection
Usually due to lymphoid hyperplasia (chickenpox) or facecloth
What would you see in the blood for: hepatocellular damage, cholestasis, reduced synthetic function?
ALT, AST, gamma glutamyl transpeptidase
Bilirubin, alkaline phosphatase
Reduced albumin and increased clotting time (prothrombin)
What are the 3 classifications of jaundice?
Pre hepatic - haemolytic
Hepatic - parenchymal
Post hepatic - cholestatic
Explain pre hepatic causes of jaundice
Excess haemolysis - membrane defects, infections, Gilbert’s syndrome
Explain hepatic jaundice
Decreased function - drugs, viruses, cirrhosis
Explain post hepatic jaundice
Obstruction - intrahepatic - hepatitis, cirrhosis, drugs
Extra hepatic - gallstones, cancer
What would you see in the blood for acute and chronic hepatitis?
Raised AST/ALT and jaundice
Reduced clotting and albumin
What are risk factors for gallstones?
Female
Old
Obese
What can gallstones be made of?
Cholesterol, calcium and bile
Explain pancreatitis
Inflammation of the pancreas due to released enzymes. A duct obstruction causes acinar damage and release of proteases, lipase sand elastase
What are some causes and clinical features of pancreatitis?
Gall stones, ethanol, trauma
Acute - Increased amylase, ALP, pain, vomiting, SIRS
Chronic - pain, steatorrhea, reduced albumin and jaundice
What is the structure of the small intestine?
Mucosa folded into villi separated by crypts. Cells multiply and then migrate and mature on the way to villi tips Micro villi (brush border) to increase surface area
In broad terms how is absorption done in the small intestine?
Villi cells secrete enzymes forming an unstirred layer. Nutrients diffuse into it and the enzymes digest them
What enzymes does the body have to digest carbohydrates?
Alpha amylase in saliva and pancreas
Isomaltase, maltase, sucrose and lactase in the unstirred layer
Explain how glucose is absorbed
Sodium pumps generate a sodium gradient and then glucose enters from the lumen along with sodium using SGLT1. Glucose then diffuses into the ECF via GLUT2
What is oral rehydration therapy?
Consuming glucose and salt allows for greater Na+ intake and therefore a greater osmotic gradient
How are amino acids absorbed?
Protein –> oligopeptide via pepsin from the stomachs chief cells and peptidases from the pancreas
Oligopeptide –> amino acids using enzymes in the brush border
Up taken in same manner as glucose
Explain pernicious anaemia
Vit B12 is absorbed in the terminal ileum using intrinsic factor produced in the stomach
Vit B12 deficiency due to stomach damage or ileum removal
Explain segmentation
The intestine is divided into segments which mixes the contents. The pacemakers fire more rapidly at the cephalic end (12–>8) so the gradient moves contents down
What movement mechanisms are in the large intestine?
Haustral shuttling - same as segmentation
Mass movement - once or twice a day a peristaltic propulsion
What factors control defaecation?
Internal anal sphincter - smooth muscle - parasympathetic - relax
External anal sphincter - striated - voluntary - relax
What are the types of inflammatory bowel disease?
Ulcerative colitis - mucosal ulceration in rectum and colon
Crohn’s disease - transmutation inflammation of entire GIT
Microscopic, diversion, diverticular colitis
Contrast Crohn’s disease and ulcerative colitis
Crohn’s - small bowl and colon, skip lesions, peri anal disease, fistulas, granulomas and fibrosis
Ulcerative - only in colon, continuous lesions, rectal involvement and bleeding
What are the roles of normal microbiological flora?
Synthesise vitamins - K, B12 Prevent colonisation by pathogens Kill non-indigenous bacteria Stimulate GALT development Stimulate antibody production
What are the types of bacteria (oxygen) and give an example of each?
Obligate aerobes - need O2 - TB
Obligate anaerobes - die in O2 presence - clostridium (produce spores for protection)
Facultative anaerobes - prefer O2 - E. Coli, staphylococcus
Where are the anaerobic areas of the body?
Mouth, small bowel, colon
Name some microbes found in the mouth and a condition it can cause
Staph aureus - parotitis
Candida albicans - oral thrush
Name some microbes in the throat
Strep viridans/pyogenes/pneumoniae
Staphylococci
Neiserria meningitidis
Haemophilus influenza
Why is abdominal surgery risky? What conditions can occur? And what is done to reduce the risk?
Lots of bacteria in the colon so high risk of wound infection
Faecal peritonitis and perianal abscessw
Prophylactic metronidazole and gentamicin
What microbes are normally in the vagina and what is their physiological function?
Lactobacillus (gram positive)
Produce lactic acid to stop other bacteria colonising
What is the difference between bacteraemia and septicaemia?
Bacteraemia - bacteria are cleared rapidly
Septicaemia - bacteria aren’t cleared and multiply. Cause sepsis
What are the symptoms of oesophageal carcinoma? What is the 5 year survival rate? What investigations are done?
Dysphagia and weight loss
5%
Endoscopy, biopsy, barium
What are the symptoms of gastric cancer? What is the 5 year survival rate? What investigations are done?
Epigastric pain, vomiting, weight loss
20%
Endoscope, biopsy, barium
What are some ways of imaging the GI tract?
X ray Barium swallow/enema/meal follow through Ultrasound CT MRI Angiography
What could cause a small bowel obstruction and what would the symptoms be?
Hernia, adhesion, tumour, inflammation
Vomit, mild distension, absolute constipation, colick pain
What can cause large bowel obstruction and what would the symptoms be?
Colorectal carcinoma, diverticular stricture, hernia, volvulas, pseudobstruction
Pain, distention, constipation, colick pain
Why might an erect chest x ray have to be done for an abdominal problem?
See if diaphragm is elevated due to
Perforated bowl - ulcer, tumour, obstruction, trauma, iatrogenic, diverticular disease
