GI Flashcards
What is a Diverticula?
When pressure is too high in the colon it can produce an abnormal ‘out pouching’ to form a hollow. Most likely in the sigmoid colon as blood supply causes an area of weakness
What is Meckels’ Diverticulum?
Pouch in lower part of the small intestine, a vestigial remnant of the yolk sac. It can produce ectopic gastric mucosa which then produces gastric acid causing irritation
What are Haemorrhoids?
Vascular structures in the anal canal that aid with stool control. When they become swollen + inflamed they are painful, itchy + blood may be present in stool.
Where do you find the Oropharynx?
Below Nasopharynx + above the Laryngopharynx, extends from the uvula to the hyoid bone. Contains the epiglottis
What is Xerostomia?
Insufficient saliva production. You can still eat moist foods but teeth + mucosa degrade very quickly
Name the three paired Salivary Glands + their secretions
- Parotid Glands (Serous Saliva- 25% of volume secreted)
- Sublingual Glands (Mucus Saliva - 5%)
- Submaxillary Glands (Mixed Serous + Mucus - 70%)
Describe the Secretion of Hypotonic Saliva
- Acinar Cells secrete an isotonic fluid containing enzymes, it does this by secreting Cl ions into lumen, water + Na then follow passively.
- Duct cells remove Na + Cl and add HCO3
- Gaps between duct cells are tight so water doesn’t follow the osmotic gradient + saliva remains hypotonic
How does flow rate effect the tonicity + pH of saliva?
- At a high flow rate there is less chance for Na to be removed so saliva is less hypotonic
- Stimulus for secretion promotes HCO3 secretion so at high flow rates you have more alkaline saliva
What is the Parasympathetic Stimulation of the salivary glands?
Glossopharyngeal (9th cranial nerve)
Stimulates increase in production of primary secretion (acinar cells) and increased the addition of HCO3
Describe the process of Swallowing
- Voluntary Phase - Tongue moves bolus up + posteriorly
- Pharyngeal Phase - Triggered when bolus touches anterior tonsillar pillars. Soft Palate moves upwards blocking off nasopharynx from oropharynx, hyoid bone is raised to block airway with epiglottis. Tongue moves upwards + backwards to force bolus into oesophagus
- Oesophageal Phase - Begins when bolus passes upper oesophageal sphincter. When it passes it it initiates peristaltic wave. If primary peristalsis doesn’t clear oesophagus second peristaltic wave is triggered above site of bolus
What muscle lies between the Pharynx + Oesophagus?
Cricopharyngeus Muscle
What is the Arcuate Line (Line of Douglas)?
Line that marks the level at which the posterior part of the rectus sheet disappears
What is a Rectus Sheath Haematoma?
Bleeding into the Rectus Abdominas, as its a tight space this is can be very painful. Sometimes seen in patients of Warfarin
What is a Hernia?
A protrusion of an organ through the wall of the cavity containing it
What is the structure of the Inguinal Canal? What runs through it?
Passage that extends inferiorly + medially through the inferior part of the abdominal wall. Opening is the deep inguinal ring, exit is the superficial Inguinal ring.
In men the Spermatic cord runs through it. In women its the round ligament of the uterus
What is a Direct Inguinal Hernia?
Protrudes into the Inguinal canal through a weakened area of transversalis facia near the medial inguinal fossa within Hesselbach’s triangle.
What is an Indirect Inguinal Hernia? What do most of these result from?
Protrudes through the deep inguinal ring. Most due to failure of embryonic closure of the deep inguinal ring after testicle has passed through it.
Describe Femoral Hernias
Protrusion of abdominal viscera through the femoral ring, appears as a mass in the femoral triangle. Often painful. More common in females due to wider pelvis. Can cause strangulation due to rigid boundaries of femoral ring
What complications can arise from Herniation?
- Strangulation - Constriction of blood vessels prevents blood flow to the herniated tissues
- Incarnation - Can’t be removed or pushed back into place
What do Parietal Cells secrete?
HCL
What do Chief Cells secrete?
Proteolytic enzymes (Pepsin)
Explain the mechanism for secretion of stomach acid
Because most bodily fluids are slightly alkaline they need to produce large quantities of H+ to be able to secrete it. Water is split into H+ and OH- in the mitochondria of parietal cells. OH- is combined with CO2 to form HCO3- which is exported into the blood.
Parietal cells have invaginations (Canaliculi) which have proton pumps to excrete H+ into stomach.
For every mol of H+ into stomach there is 1 mol of HCO3- into the blood
What stimulates the production of HCL?
- Gastrin (binds CCK Receptors to insert H/K pumps)
- Vagus nerve stimulates through musclarinic Ach receptor
- Histamine binds to H2 receptors on Parietal cells
What controls the secretion of Gastrin? Where are G-cells located?
- Peptides + Amino acids in stomach
- Ach Stimulation by Vagus nerve
- Gastrin releasing peptide
- Somatostatin released by D-cells when pH is low inhibit gastrin
G-cells found in Antrum of stomach
What are the 3 phases of Digestion and what do they do to HCL production?
- Cephalic (Smelling, tasting, chewing, swallowing. Causes stimulation of parietal cells + G cells via vagus nerve)
- Gastric (Distension of stomach stimulates vagus nerve to increase stimulation of Parietal + G-cells. Presence of Amino acids stimulates G cells. Food acts as a buffer increasing pH decreasing production of somatostatin by D-cells)
- Intestinal (Chyme stimulates Gastrin secretion. Low pH causes somatostatin production by D-cells)
What defences does the stomach have?
Mucus + HCO3 released by surface mucus cells + neck cells in gastric glands. This forms a thick alkaline layer which sticks to epithelial surface keeping it at a higher pH.
Prostaglandins help to maintain a high mucosal blood flow.
What can cause breaches in the stomachs defences + what does this lead to?
- Alcohol - Dissolves the mucus layer
- Helicobacter pylori - Causes Gastritis by invading the stomach lining + producing cytotoxins
- Non Steroidal Anti Inflammatories - Inhibit prostaglandin production
These can all lead to Gastritis, Ulceration + GORD
What pharmacological interventions can be used to combat Stomach ulcers + other problems of the GI tract? How do they work?
- H2 Blockers (Cimetidine, Ranitidine) - Block the binding of Histamine to H2 receptors on Parietal cells
- Proton Pump Inhibitors (Omeprazole) - These block the H/K ATPase which presents H+ from being pumped into the stomach. As its the terminal step its a preferred target.
What is Gastro Oesophageal Reflux Disease? What can it be caused by? What problems can it cause? Whats the treatment for it?
- Its the reflux of stomach contents into the oesophagus, presents with heartburn, cough, sore throat + dysphagia.
- Caused by; Lower oesophageal sphincter problems, Delayed gastric emptying, Hiatus hernia, Obesity
- Treated with lifestyle changes (not lying down after food) H2 blockers, Antacids (neutralise acid), PPI’s
What is Chronic Gastritis? What can cause it?
- Chronic inflammation of the the stomach lining
- H. pylori - infects lining of the stomach + produces cytotoxins
- Autoimmune - Body produces antibodies against Gastric Parietal Cells, this means no Intrinsic factor (Needed to absorb B12) is produced so patients have Pernicious Anaemia.
What can cause Acute Gastritis and why? How does it present?
- Heavy use of NSAID’s - these inhibit prostaglandins which are responsible for maintaining mucosal blood + nutrient supply
- Alcohol - Dissolves protective mucus layer
- Chemotherapy - Damages rapidly dividing cells
- Bile reflux - Bile is an irritant to the stomach lining, can happen with reverse peristalsis
It can be asymptomatic but can also present with pain nausea, vomiting + bleeding which can be fatal
What are Peptic Ulcers? Where are they most common? What can it be caused by? How does it present?
- Defects in the Gastric or Duodenal mucosa, it must extend through the muscularis mucosa.
- Most common in the first part of the Duodenum although can also affect the lesser curvature of the stomach
- Can be caused by; Stomach acid, H.pylori, NSAID’s, Smoking + Massive Phycological stress (Extreme trauma, ITU)
- Present with burning gnawing epigastric pain, often worse after a meal or at night time (more Duodenal than Gastric). More serious causes can have bleeding + anaemia (erodes through artery), Satiety (feeling full early), weight loss + perforated bowel