Gastrointestinal System Flashcards
What are the two functions of the gastrointestinal system?
Digestion (processes food) and absorption (transfers nutrients to circulation)
What are the 2 groups of organs in the GI system?
Digestive tract
Accessory organs
List the accessory organs and give their functions:
Salivary glands - secrete mixed watery mucous which buffers mouth pH, protects surface of mouth, antibacterial, maintain tooth structure
Gall bladder - store and concentrate bile produced by liver and aids in fat digestion
Liver
Pancrease
List the components of the GI tract in order:
Oral cavity
Pharynx
Oesophagus
Stomach
Small intestine
Large intestine
Rectum
Anus
Describe the structure of the pharynx and its function
12-15cm long muscular tube
Divided into 3 parts: nasopharynx, oropharynx, laryngopharynx
Air and food passes through it to oesophagus, conducts air
Describe the structure of the oesophagus and its function
20-25cm long muscular tube
Mucosa membrane made from strattified sqauamous epithelium, the lamina propria and muscularis mucosae
Submucosa contains glands and lymphoid follicles
Muscularis mucosae/ externa coprised of cirular and logitudinal
- Changes from skeletal in top 1/3, then both skeletal and smooth and only smooth in bottom 1/3
Serosa
Passes food from pharynx to stomach
Passes behind the heart and trachea
What are the 9 areas of the abdomen called?
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1: right hypochondrium
2: epigastric
3: Left hypochondrium
4: Right lumbar
5: Umbilical
6: Left lumbar
7: Right iliac fossa
8: Suprapubic
9: Left iliac fossa
What organ is found in the right hypochondrium?
liver
What organ is found in the epigastric?
duodenum, liver, gall bladder, pancreas, stomach
What organ is found in the left hypochondrium?
Spleen and stomach
What organ is found in the right lumbar?
ascending colon, kidney
What organ is found in the umbilical?
Stomach, head of pancreas, small intestine (duodenum), transverse colon, lower aspects of right and left kidneys
What organ is found in the left lumbar?
descending colon, left kidney
What organ is found in the right iliac fossa?
caecum, appendix, part of ascending colon
What organ is found in the suprapublic?
bladder, uterus, parts of small intestine
What organ is found in the left iliac fossa?
sigmoid colon, descending colon
What are the 4 layers of the GI tract?
Mucosa/ mucous membrane
Submucosa
Muscularis propria
Adventitia
What makes up the mucosa/ mucous membrane? What is the function of each layer?
Epithelium: lines cavity
Lamina propria: thin layers of loose connective tissue, contain inflammatory cells and provides support
Muscularis mucosae: smooth muscle continous thoughout GI tract
What is the submucosa formed from?
Dense, irregular connective tissue
Contains many blood, lymphatic vessels and nerves
Structure and function of muscularis propria:
Inner circular layer and outer longitudinal layer of smooth muscle
Responsible for peristalsis (movement of food)
What is the adventitia? Where is it found?
Outer layer of fibrous connective tissue surrounding an organ
Oral cavity in gut, upper end of oesophagus, ascending and descending colon, rectum
What is the serosa/ serous membrane?
Part of tissue that is fixed
Found in the remainder of the GI tract and allows for reduction of friction
How does the histology change throughout the GI tract?
Same layers just speicilised in different areas:
- Stomach: epithelium changes to simple columnar (this remains for rest of GI tract), oblique muscle as part of muscularis propria which lie in different direction
- Duodenum: vili increase SA for adsorption, Brunner’s glands secrete bicarbonate ions to neutralise acid from stomach
- Ileum: payer’s patches, lymphoid follicules part of the immune system, prevent growth of harmful bacteria
What are the different parts which comprise the stomach?
- Top section = fundus (lets out air)
From entrance to exit:
1. Oesophagus
2. Cardia
3. Body
4. Pylorus
5. Pyloric sphincter
6. Duodenum
Greater and lesser curve
What are rugae in the stomach? What is their funtion?
Muscular folds in stomach
Allow for distention and reduction depending on volume of food in stomach
What cells are present in the mucosa in the stomach? What are their function?
Endocrine cells: produce gastin which stimulates parietal cells
Parietal cells: produce HCl which breaks pepsinogen into active pepsin
Chief cells: produce pepsinogen
Surface mucous cells: secrete mucous to help protect mucosal lining
3 parts of small intestine:
Duodenum
Jejunum
Ileum
Structure of small intestine epithelium:
Simple columnar
Villi increase SA (x30) to increase digestion and absoption (most prevelant in duodenum, decrease towards ilium)
Function and specialisations of the duodenum:
Recieves chyme
Contains Brunner glands which secrete bicarbonate secretions to reduce stomach acids
Recieves common bule duct (fat digestion) which is controlled by Sphincter of Oddi (via opening callled major duodenal papilla)
Pancreatic juices enter
What are the folds in the small intestine that are naked to the human eye called?
Plicae
What are the 2 functions of the pancrease?
Exocrine gland (99% of pancreate): produces digestive enzymes and bicarbonate ions
Endocrine part/ Islets of langerhans: produce hormones which control maintainance and stabilisation of glucose levels
- Insulin: promotes glucose adsorption and conversion of glycogen
- Glucagon: conversion of glycogen to glucose
- Somatostatin: reduce acid secretion, slow digestive process, other function
How many lobes does the liver have?
4
Major functions of the liver (5)
- produces bile which is stored an concentrated in gall bladder, duct passes out of gall bladder through cystic duct
- Detoxification of everything from GI tract
- Regulates blood glucose
- Synthesises proteins involved in platelet regulation and clotting factors
- Drug metabolism: inactivates hormones and drugs, as well as insulin and waste products.
Blood supply to liver:
75% is deoxygenated and comes from hepatic portal vein from gut, spleen and related organs
25% is oxygenated and comes from hepatic arteries
Parts of the large intestive:
– Ileocecal junction/ ileocecal valve –
Caecum (resevoir for chyme)
Ascending colon
(hepatic flexure)
Transverse colon
(splenic flexure)
Descending colon
Sigmoid colon
Specialisation of large intestine
Taenia coli: incomplete layers of longitudinal muscle, circular contractions, anatomical landmarks
Haustra/ haustrations: ring-like circular muscle
Apendices epipoicae: pouches of peritoneum filled with fat mainly on transverse and sigmoid colon but not rectum
3 main vessels supplying GI tract
- Coeliac trunk - supplies foregut (oesophagus, stomach, liver, spleen and first half of duodenum)
- Superior mesenteric artery - supplies midgut (last half of duodenum, jejunum, ileum, caecum, appendix, ascending colon and first half to first 2/3 of transverse colon
- Inferior mesenteric artery - hind gut (last 1/3 transverse colon, descending colon, sigmoid colon and rectum)
Venous drainage of the gut:
- Inferior mesenteric vein - drains hindgut, passes into splenic vein
- Superior mesenteric vein - drains midgut , joins splenic vein
- Splenic vein and superior mesenteric vein combine to form portal vein
- Portal vein is for unpaired abdominal organs (e.g. gut and spleen
- Portal vein passes to liver for detoxification, blood ultimately passes back to heart from hepatic vein
