GI Flashcards
Properties of the enteric nervous system and it’s relationship to the autonomic nervous system
Post ganglionic plexuses which can work independently to control motility and secretions. Activity is controlled by autonomic innervation with the brain
Describe the fluid balance of the gut
1l of food
1.5l of saliva
2.5l gastric secretions
9l alkali and water
12.5 small intestine
1.35 large
Deficate 150g
Why might a patient have dysphasia?
Anaesthetic, neurological defect, oesophageal blockage/ defect in musculature or a tumour tumour
Functions of saliva
Protection- contains I-, alkaline and Ca to protect teeth, contains lysozyme.
Moistens food to assist swallowing
Digestion- amylase
Prevents xerostomia
Components of saliva secreted by each salivary gland
Sub maxillary - serous and mucus 70% Parotid - serous 25% Sublingual - mucus 5% Hypotonic. Mucous contains mucins Contains Ca, I, low Cl, K, low Na, hCO3, enzymes, bacteriostats
Mechanism of secretion of serous saliva. Different with STIM?
Secreted isotonically by acini
Ducts impermeable to h2o and have Na ATPase on Basolateral surface creating conc gradient.
More Na reabsorbed so hypotonic
HCO3 secreted via h+ reabsorption on Basolateral NHX co2 back into cell, HCO3 into lumen via anion exchanger.
Acini secrete I and enzymes. Secretes Cl so ions and h2o follow.
Resting saliva is neutral or slightly acid
Stimulated then
More hco3
Less hypotonic so more Na and less k
More enzymes
Control of salivary secretion and effect of atropine
Largely nervous control
Sympathetic decreases volume - from the superior cervical ganglion, decreases blood flow
Parasympathetic stimulates acinar secretion, ductal secretion of HCO3 and co-transmitters increase blood flow.
From the medulla - afferent information from nose, mouth and tongue but also conditioned reflexes
Describe the process of swallowing
Voluntary phase- formation of a bolus, move into pharynx
Pharangeal phase- pressure receptors in palate and anterior pharynx afferent to brain stem swallowing centre. Causes larynx to lift, glottis to close, upper oesophageal sphincter to open and inhibits respiration.
Oesophageal phase- first 1/3 is voluntary. Rapid peristalsis conducted by extrinsic nerve via the swallowing centre. Lower oesophageal sphincter opens.
Outline how disordered swallowing may occur
Anaesthesia/ surgery may affect the brain stem so that swallowing I not coordinated- risk of aspiration.
Motility problem e.g. Achalasia- smooth muscle does not relax, diffuse oesophageal spasm (DES), scleroderma
Obstruction/ compression e.g. Tumours, squamous cell carcinoma, adenocarcinoma or lymphoma
Categorise different types of dysphasia based on pathology
Dysphgia - difficulty swallowing solids
Oesophageal dysphagia- difficultly swallowing liquids as they cannot form a bolus so harder to coordinate. Due to problems in lower sphincter or cardia.
Mechanical obstruction often solids then liquids.
Motility then both.
Odynphagia - pain on swallowing
Investigate with barium swallow (especially solids), endoscopy
Mechanisms that prevent GORD
Lower oesophageal sphincter physiological.
Right Cruz of the diaphragm has a pinch cock effect
horizontal connection of oesophagus to cardia at an acute angle.
Positive intra abdominal pressure closes
Folds in mucosa occlude lumen at the gastro oesophageal junction
Results in Barrett’s oesophagus, cough, hoarseness of voice and asthma.
Describe the development of the muscular and fascial layers of the abdominal wall including the inguinal canal
Rectus muscles grow within the transversalis fascia
Two sides of developing abdominal wall meet at the linear alba. Develop from somatic mesoderm.
Inguinal canal- oblique through the layers of abdominal wall, testes pushes wall through during development which become the fascial covering of the spermatic cord
Explain the developmental basis of umbilical and inguinal herniea
Weakness in umbilicus due to malformation after the gut grows outside of the abdominal canal.
Weakness at inguinal rings due to the passage.
Describe how the coelomic cavity and peritoneal cavity develop
Cephalocaudal folding causes the gut tube to pinch leaving a cranial and caudal section with only he vitaline duct.
Lateral folding creates an endoderm tube. Around this the intra coelomic space gets pinched off to create one cavity or coelom. This later surrounds the viscera and in the abdomen is called the peritoneum.
Describe the fate of the embryonic dorsal and ventral mesenteries
Ventral in foregut becomes liver, gall bladder and biliary tree and the head of the pancreas and lesser omentum.
Dorsal foregut becomes the tail, neck, body and superior head of the pancreas. Connects stomach to transverse colon.
Explain how the omenta and the mesentary of the small intestine form and relate this to their arrangements in the adult
Rotation of the stomach so that ventral mesentary lies to the right. Growth of cells on the left is quicker resulting in anteroposterior rotation of the stomach and greater curvature. The greater omentum on the greater curvature fuses with the transverse colon. Mesenteries of small intestine fuse forming a fan shape.
Why do some abdominal organs possess mesenteries and some are retro peritoneal
Retroperitoneal organs never had a mesentary or had a peritoneum e.g. Kidneys- intermediate mesoderm
Secondary retro peritoneal organs dorsal mesenteries regressed and peritoneum fused so they are attached to the abdominal wall and only have an anterior covering of peritoneum. E.g. Duodenum - posterior peritoneum forms fusion fascia
Describe the respiratory primordium development.
Respiratory diverticulum forms off the pharyngeal gut. Becomes respiratory primordium. Divided by the trachealoesophageal septum
Describe the functions of the stomach
Digestion - pepsin and mechanical break down
Kills pathogens- low pH
Storage
Describe the components of gastric secretion and their cellular origins
HCO3/ mucus - neck cells/ foveolar cells
Pepsin - chief cells
Gastric - G cells/ endocrine cells
HCl- Parietal/oxyntic cells (canaliculi)
Explain the mechanism of stomach acid secretion
Proton pump into lumen from canaliculi, HCO3 into blood stream. Both produced via mitochondrion
Control of gastric acid secretion including phases of control
H+ and prostaglandins (neck cells) Controlled by
Gastrin - distension and peptides increase, H+ decreases
ACh/ parasympathetic - stomach distension and CNS
Histamine- gastric and ACh stim, produced by mast cells and act on H2 receptors to stimulate CAM. Sensitive, antagonists are effective.
Phases:
Cephalic phase- CNS stims acid
Gastric phase- neutralisation and peptides and distension stim gastrin
Intestinal phase - hormones inhibit gastrin secretion, pH and peptides fall. Less distension.
Outline the ways in which gastric acid secretion may be reduced by drugs
Proton pump inhibitors and H2 antagonists
Describe the function of the stomach defenses, what can damage these?
Unstirred layer of mucus and HCO3 prevents degredation of gastric cells by h+ and pepsin.
NSAIDs inhibit prostaglandins which decreases mucus production.
Alcohol dissolves mucus.
H pylori damages via inflam.
Patterns of motility across the stomach
3 squirts a minute.
Rhythmic contraction from fundus to pylorus resulting in contraction of pyloric sphincter so only a squirt into intestine.
Contractions can increase in force not frequency
Decreased by fat, low pH or hypertonicity in duodenum
Describe the role of rotation of the midgut loop in the establishment of the disposition of abdominal viscera
Rapid growth of the primitive gut tube and the liver results in the formation of the midgut loop which herniates through the umbilicus. The SMA lies within. There is rotation of 270 degs so that the cranial part lies to the left of the SMA and caudal part. The small intestine begins to develop in the cranial part and the cecal bud develops in the caudal part.
The caudal part becomes the transverse colon, cecum and distal ileium.
The cranial part becomes the duodenum, juju num and proximal ilieum
The cecal bud descends so that the small intestine lies in the middle and the transverse colon superior in the abdominal cavity
The vitelline duct regresses however may remain as a cyst, vitelline fistula or meckle’s diverticulum.
Lumen of gut tube - oesophagus, bile duct, small intestine - becomes obliterated due to rapid growth and is recannalised later.
Describe the portioning of the cloaca and the development of the anal canal
Urorectal septum divides the cloaca into the urogenital sinus and anorectal canal at the cloacal membrane with the perineal body between. Bottom 1/3 of anal canal has no peritoneum. Pectin ate line where endoderm meets ectoderm.
Superior- columnar, IMA, pelvic parasympathetic nerves S234, stretch only, internal iliac nodes.
Inferior- stat squamous, peudendal artery, peudendal nerve S234, superficial inguinal node, pain and touch
Fate of the dorsal and ventral mesenteries
Dorsal- mesocolon, mesentary proper, greater omentum, gastrolienal ligament from stomach to spleen, lienorenal ligament from spleen to kidney
Ventral - letter omentum, falciform ligament
Innervation and blood supply to midgut and hindgut
Midgut - SMA, vagus nerve S234 para, sympathetic superior mesenteric ganglion and plexus.
Hindgut- IMA, pelvic S234 and inferior blah
Describe the developmental basis for common congenital defects including atresias, stenosis, malrotation, incomplete rotation, omphalocele, exomphalos, imperforate anus and gastroschisis
Atresias e.g. Imperforate anus - failure of anal membrane to rupture. Anal/anorectal agenesis. Hindgut fistulae e.g. Into bladder.
Stenosis- failure of Recanalisation normally in duodenum, vascular accidents may contribute e.g. Volvulus from malrotation. Pylori stenosis due to hyperplaisia without recan. Leads to projectile vomiting,
Malrotation is 90 deg wrong way so duodenum is over TC so volvulus likely/ strangulation or incarceration.
Incomplete rotation- left sided colon only 90 deg
Omphalocele/ examphalos- gut herniates through umbilical chord
Gastroschisis- failure of closure of abdominal wall, rupture through amniotic sac so no covering.
Describe the structure and layers of the abdominal wall
Peritoneum Extra peritoneal Fat Transversalis fascia/ endo abdominal fascia Transver oblique Deep fascia Internal oblique Middle fascia External oblique Scarper fascia Camper fascia (fatty) Skin
Landmarks of the abdominal wall
Arcuate line - 1/3 between umbilicus and pubic crest
Linear alba
Linear semilunaris
McBurney’s point 2/3 umbicilus and asis
Tendinosus intersection
Umbilicus- L2
Epigastric fossa- depression in epigastric region just inferior to xiphoid process
Describe the musculature of the abdominal wall
External oblique- spinal nerve roots and intercostal nerves T7-11. Flexion of trunk, rotation, compress and support abdominal viscera
Internal oblique - anterior rami T6-12 and first lumbar nerves same function as EO.
Transversus - same inn as IO. Compresses and supports abdominal viscera
RA - IO, flexion, compression, stabalises and tilts pelvis - antilordosis
Pyramidalis in RS
Developmental defects and consequences in abdominal wall. Divariation of recti, Rectus sheath Haematoma, ectopia cordis, patent urachus, Urachal cyst, patent vitellointestinal duct, meckle’s diverticulum, examphalos, gastroschisis
Di variation of recti- loss of linear alba, e.g. Pregnancy
Rectus sheath haematoma- blood in Rectus sheath may cause abdo pain with or without lump, surgery no normally needed, pregnancy or trauma
Ectopia cordis- failure of maturation of ventral mesoderm, heart outside thoracic cavity, often with other CHD
Meckle’s diverticulum- 2 types of mucosa- gastric and pancreatic, 2 feet from ilealceacal valve, 2 inches, 2% of pop, 2:1 men:women
Describe visceral and somatic referred pain
Somatic referred pain - damage/ stimuli in proximal part of a sensory neurone where the pain is felt in the more distal structures/ dermatome that the nerve innervates.
Visceral- pain in the region of an afferent nerve is perceived in the region of the efferent sympathetic nerves of the same spinal chord segment
Visceral refered pain and development
Foregut - epigastric
Midgut- periumbilical
Hindgut- suprapubic
Cardiac refered pain?
Chest (left) neck, left shoulder
Oesophageal referred pain
Chest - epigastric
Gastric referred pain?
Epi gastric, back
Duodenal referred pain
Epi gastric or umbilical
9 abdominal division
R and l hypochondriac
Right and left lateral/ lumbar and umbilical
Pubic/ hypogastric and right and left inguinal/iliac
Gall bladder
Right hypochondriac/ lumbar and right shoulder
Hepatic referred pain
Right hypochondriac/ epigastric, right neck/ shoulder and back (similar to kidney)
Splenic referred pain
Left lateral
Retro peritoneal referred pain?
Back pain e.g. aorta and pancreas ( also epigastric)
Appendix refered pain
Begins in periumbilical. Peritoneum involved then superficial to appendix.
Small bowel colic pain
Pain every 40 seconds, periumbilical
Large bowel colic pain
Severe pain every 20-30 mins. Suprapubic region
Renal/ ureteric colic
Most severe pain.
Ureteric follows inguinal ligaments
Renal found in loin
Uterine and bladder pain
Hypogastric
Causes of diaphragmatic pain
Spleen, ectopic pregnancy, perforated ulcer
Regions the transverse colon is found in
Also spleen.
Periumbilical and left and right lumbar
What landmarks divide the abdomen into 9?
Either sub costal plane or transpyloric or transtubercular (iliac tubercule) or Interspinous plane.
Vertically - mid clavicular to mid inguinal point
Describe structure and relationship of supracolic and infra colic compartments
A
Common surgical incisions
Midline Transverse Need strong closure Appendincpectomy at my burneys point Gridiron incision
What is a peritoneal ligament?
A double layer of peritoneum that connects an organ with another organ or to the abdominal wall e.g. Hepatogastric, hepatoduodenal
What are the supra/infracolic compartments? Are they connected?
Above and below the transverse mesocolon.
Infra colic divided into left and right by small intestine mesentary. It is also below the greater omentum.
Communication by the parabolic gutters
Subphrenic spaces?
Right- under diaphragm and above right side of the live, bounded behind by coronary ligament and on the left the falciform ligament
Left- between diaphragm and anterior superior left liver, anterosuperior aspect of stomach and diaphragmatic surface of spleen. Right is falciform. Behind is anterior layer of left triangular ligament
Recto- uterine and vesico uterine pouches?
Rectouterine puch- fold of peritoneum between the posterior vaginal fornix, uterine cervix and rectum.
Vesico- uterine pouch- smaller between fundus of uterus and bladder.
Rectovesicle pouch in males- between rectum and bladder.
Developmental defects and consequences in abdominal wall. Divariation of recti, Rectus sheath Haematoma, ectopia cordis, patent urachus, Urachal cyst, patent vitellointestinal duct, meckle’s diverticulum, examphalos, gastroschisis
Di variation of recti- loss of linear alba, e.g. Pregnancy
Rectus sheath haematoma- blood in Rectus sheath may cause abdo pain with or without lump, surgery no normally needed, pregnancy or trauma
Ectopia cordis- failure of maturation of ventral mesoderm, heart outside thoracic cavity, often with other CHD
Meckle’s diverticulum- 2 types of mucosa- gastric and pancreatic, 2 feet from ilealceacal valve, 2 inches, 2% of pop, 2:1 men:women
Mesentary of the small intestine?
Fan shape, divides left and right infracolic, moves inferiorly obliquely to the right. Crosses major structures including the duodenum.
Where are the areas of potential weakness in the abdominal wall?
A
Describe the areas of potential weakness in the abdominal wall
Myopectineal oriface, epigastric at midline, umbilical, incisional, femoral, direct and indirect inguinal. Hesselbacks triangle
Describe the MPO
Divided anteriorly by the inguinal ligament and posteriorly by the iliopubic tract (binds external iliac vessels, thickening of transversalis fascia). Medially by the lateral boarder of the Rectus muscle, superiorly by the arching fibres of the transversus abdominus and internal oblique muscles, laterally by iliopsoas and inferiorly by the Cooper/ Pectineal ligament (extension of lacunar ligament).
Superiorly the spermatic cord perforated and inferiorly, the femoral vessels .
Protected by aponeurosis of transversus abdominus and the transversalis fascia
Boarders of Hesselbach’s triangle
Lateral inferior epigastric arteries,
Medial Rectus sheath/ linear semilunaris
Inferior - inguinal ligament
Structure of the inguinal canal
Anterior- aponeurosis of external oblique and internal oblique (lateral 1/3)
Posterior- transversalis fascia
Inferior- inguinal ligament (rolled by external oblique aponeurosis)
Superior- aponeurosis of internal oblique and transverse abdominus and transversalis fascia.
Deep ring is superior to midpoint of the inguinal ligament and formed by invagination of transversalis fascia
Superficial is just above pubic tubercle formed by invagination of external oblique. Inter rural fibres prevent from opening.
Spermatic cord and round ligament of the uterus. 3 arteries in males, 3 nerves
Distinguish direct and indirect hernias and describe their position
Direct Through Hesselbach’s triangle
Indirect inguinal hernia trough deep inguinal ring result of failure of embryonic closure.
Describe epigastric, umbilical and femoral hernias
Epigastric- between xiphoid process and umbilicus at linear alba - pregnancy and obesity make it more common
Umbilical- associated with weakness or failure to close, can be acquired- female/ obese.
Femoral hernia - through femoral ring/ canal. May grow- travel t saphenous opening. More likely to strangulated than inguinal. Tender, in femoral triangle. Common in females as they have a wider pelvis. StrangulTion due to rigid boundaries of femoral ring.
Richter’s hernia- only one half of lumen
Describe the prevalence and incidence of common disorders affecting the stomach
Gastritis common with dyspepsia
Ulcers- 10% of cases
Gastric cancer less than 1%- malt lymphoma or adenocarcinoma