GI S1 (Done) Flashcards
Breifly describe the major function of the GI tract
Food (a complex mix of large molecules) is processed into a:
- Sterile
- Isotonic
- Neutral
Solution of:
- Small sugars
- Amino acids
- Small Lipids
- Other small molecules
Ready for absorption and excretion
AKA Digestion
In order what are the smaller processes involved in digestion?
Initial physical disruption
Ingestion and transport to storage
Initial chemical disruption and suspension (chyme)
Disinfection
Controlled release of chyme
Dilution and neutralisation
Completeion of chemical breakdown
Absorption of nutrients and electrolytes
Final absorption of water and electrolytes
Excretion
What are the major functions of the mouth?
Include brief descriptions of how each process works
Mastication
Protection with saliva:
Wetting
Bacteriostatic
Alkaline High Ca2+
Start digestion:
Salivary amylase
Swallowing:
Formation of bolus
Entrance to oesophagus
What are the major function of the oesophagus?
Transport of bolus of food to stomach
What are the major functions of the stomach?
Include brief descriptions of how each process works
Storage:
Expands/relaxes to accomodate food
Initial disruption:
Contracts rhythmically to mix and disrupt food/chyme
Secretes acid and proteolytic enzymes to break down tissues and disinfect
Deliver chyme to duodenum
What are the major functions of the duodenum?
Include a brief description of how this process works
Changes Chyme:
Draws water from ECF to dilute chyme
Enzymes added from Liver and Intestine
Alkali added to the chyme from Liver and Pancreas
What are the major functions of the small intestine?
Include brief descriptions of how each process works
Absorption of nutrients and electrolytes:
Fluid passes through slowly
High surface area
Epithelial cells absorb molecules actively and passively (often coupled to Na+ absorption)
Pass absorbed material into portal vein
Absorbs majority of water (1.5L)
What are the major functions of the Large intestine
Final absorption of water (0.15L)
Slow transit
Forms faeces which accumulate in sigmoid and descending colon
What are the major functions of the rectum?
Accepts faeces periodically propelled into rectum
Urge to defecate
Controlled relaxation of sphincters and expulsion of faeces
Label the boxes
From top left anticlockwise:
Parotid salivary gland
Submandibular salivery gland
Sublingual salivary gland
Oral cavity
Pancrease
Liver
Gallbladder
Duodenum
Common bile duct
Transverse colon
Ascending colon
Descending colon
Cecum
Appendix
Rectum
Anus
Samll intestine (Ileum)
Pancreatic duct
Stomach
Oesophagus
Tongue
Pharynx
What are the 4 layers of the GI tract wall?
Give a very brief description of each
Mucosa:
Epithelium and thin layer of muscularis mucosae
Submucosa:
Fibroelastic tissue with vessels, nerves, leucocytes and fat cells
Muscularis externae:
Inner circular and outer longitudinal layerss of smooth muscle with the myenteric plexus between
Serosa/Adventitia:
Thin outer covering of connective tissue
What is the purpose of variations in the wall structure of the GI tract?
Provide adaptations for specific functions whilst remaining a continuous hollow tube
Describe how the GI tract balances content added and absorbed in the gut
Addition:
We at 1Kg of food a day
Add about 1.5L of saliva
Add about 2.5L of gastric secretions
Add up to 9L of water and alkali in duodenum
Total - 14L
Absorption:
Small intestine absorbes about 12.5L of fluid
Large intestine abosrbs about 1.35L
Leaves 0.15Kg of Faeces
What factors of gut function reguire control and how is control acheived?
Motility and secretion must be controlled
Range of mechanisms:
- Neural
- Paracrine
- Endocrine
How is the gut controlled neurally?
Somatic:
Ingestion and excretion
Autonomic:
Parasympathetic most significant
Post ganglionic neurones for plexuses (Enteric nervous system)
Co-ordinates secretion and motility
Range of neurotransmitters
Give examples of chemicals involved in paracrine control of the gut
Histamine in stomach
Various vasoactive substances
How is Endocrine control involved in gut processes?
Produces its own hormones which travel in the blood within the gut
Range of hormones controlling:
Secretion of stomach acid
Alkali secretion from liver and pancreas
Enzyme secretion
Give a brief description of Dysphagia
Difficulty swallowing
Can be due to musculature or neurological problems or malignancy
Tumours of the oesophagus are squamous cell carcinoma high up and adenocarcinoma lower down
Give a brief description of acid reflux
Sphincter between oesophagus and stomach weakens and acid refluxes into oesophagus causing irritation and pain
Give a brief description of Barret’s oesophagus
Metaplasia of lower squamous epithelium to gastric columnar to protect against acid reflux
Give a brief description of oesophageal varices
Portal venous system is overloaded due to cirrhosis, blood is diverted to the oesophagus throught connecting vessels
This leads to dilation of the submucosal veins in the lower oesophagus
Give a brief description of peptic ulceration
Area of damage to stomach or duodenal mucosa
Usually due to irritation from gastric acid
H. Pylori is a common cuse as it leads to a breakdown of the protective mucous layer in the stomach
Give a brief description of pancreatitis
Inflammation of pancreas cuaing considerable pain
Characterised by release of amylase into bloodstream
Give a brief description of jaundice
Build up of bilirubin in the blood due to pre-hepatic, post-hepatic and hepatic causes
Prehepatic:
excess haemoglobin breakdown
Hepatic:
Liver cells unable to process bilirubin
Post-Hepatic:
Obstructive, due to obstruction of bile duct causing a back up of bile (causing liver damage)
Give a brief description of gallstones and a commonly associated symptom
Precipitation of bile acids and cholesterol in the gallbladder
Movement within the gallbladder or stones blocking the bile duct may lead to Biliary colic a painful condition produces by frustrated peristaltic waves trying to shift the stone
Tumours of the pancreas may also bock the bile outflow
Give a brief description of appendicitis
Inflammation of appendix often due to lymphoid hyperplasia or faeocaliths
Presents as pain in right side which localises to right lower quadrant (Specifically McBurney’s point - 1/3 of the distance from ASIS to umbilicus)
What is peritonitis?
Inflammation of peritoneum
Give a brief description of haemorrhoids
Vascular structures in the anal canal that aid in stool control
Con become swollen and inflammed
Pain, itchiness and haemoatochezia are associated
Give a brief description of Prolapse in regards to the GI tract
Prolapse is when an organ ‘falls out of place’
E.g. Rectum can prolapse
Give a brief description of a diverticulum
High pressure in the colon produces an outpouching to form a hollow
Commonest in the sigmoid colon due to blood supply
Give a brief description of a Meckel’s diverticulum
Pouch in the lower part of the intestine
A vestigial remnant of the yolk sac
Can produce gastric mucosa which may then produce gastric acid, causing irritation
