Gastro-Intestinal Tract (GIT) 1 Flashcards
Name the 8 components of the GIT
Mouth, Pharynx, Oesophagus, Stomach, Small Intestine, Large Intestine, Rectum, Anus
Name the 6 accessory organs
Tongue, Teeth, 3 pairs of salivary glands, Liver, Gallbladder, Pancreas
Name the 3 pairs of salivary glands
Parotid, Submandibular, Sublingual
The coverings/walls of the GIT are the same from oesophagus to anus, name the 4 layers from inner to outer
Mucosa, Submucosa, Muscularis, Serosa
Describe the mucous lining of the GIT and the function of each layer - 5 points
inner lining, has mucous membrane in direct contact with food contents, has epithelial layer which secretes enzymes and absorbs digested food, connective tissue layer which houses blood vessels & lymphatics, muscular mucosae which contains smooth muscle fibres which throws membrane into folds to increase surface area for digestion
Describe the submucosa lining of the GIT - 3 points
connective tissue which binds mucosa to muscularis, has a rich blood supply, houses part of the autonomic nervous system which controls secretion from GIT
Describe the muscularis lining of the GIT - 5 points
smooth muscle found in 2 sheets - inner, circular fibres / outer, longitudinal fibres - serves to physically break down food and push it through GIT, has nerve supply which controls mobility
Describe serosa lining of GIT - 3 points
serous membrane which has connective tissue layer & epithelial layer, forms the inner layer of the peritoneum = Visceral Peritoneum
Outer layer of the peritoneum = Parietal Peritoneum
Describe the Peritoneum
weaves between structures of the abdomen, binding them together and housing blood/lymphatic/nerve supply
What is the oral cavity formed by
cheeks, lips, gums, teeth
What is the upper portion of the oral cavity formed by
hard palate anteriorly, soft palate posteriorly
Describe the uvula - 2 points
part of the soft palate, drawn superiorly during swallowing to prevent food from entering the nasal cavity
The teeth, tongue and hard palate work together to begin …
initial mechanical breakdown of food = mastication
Chemical breakdown in the oral cavity is where digestion begins, by …
saliva which is secreted from the sublingual glands, the submandibular glands and the parotid glands
Where are the sublingual glands found
under the tongue
Where are the submandibular glands found
posteriorly beneath the base of the tongue
How does saliva from the parotid glands reach the oral cavity
secrete via the parotid duct to an area near the upper molars
Food is swallowed from the oral cavity and passes through …
the oral pharynx on route to the oesophagus
Describe the role of the Epiglottis
prevents food entering trachea during deglutination (the swallowing action)
What 5 things does saliva contain and what is their purpose
Salivary Amylase - acts on starch
Mucus - lubricates food
Water - helps dissolve food, allowing taste and early digestive reaction
Bacteriolytic Enzyme (Lysozyme) - kills bacteria and helps protect mucus membrane
Immunoglobin - prevents attachment of microbes which may attack epithelium
Describe Starch and what must be done for it to enter the bloodstream
found in most carbohydrates, made up of complex glucose chains - polysaccharides & disaccharides - bloodstream only absorbs monosaccharides therefore salivary amylase begins breakdown of these chains
Describe the role of Lingual Lipase - 3 points
secreted by lingual glands in the mouth, stimulated within the acidic environment of the stomach, begins breakdown of triglycerides into diglycerides in the process of fat breakdown
Describe the Oesophagus and its role - 3 points
muscular, collapsable tube which is behind the trachea, propels food to the stomach by muscular contractions of circular/longitudinal layers of the muscularis, secretes mucus & transports food to the stomach
Describe any chemical digestion occurring and describe the role of the fibres of the muscularis layer when it interacts with a bolus of food - 3 points
there is no chemical digestion/absorption in oesophagus, circular fibres above the bolus of food constrict to the push the food downwards, longitudinal fibres inferior to the bolus of food shorten and allow the muscular walls of the oesophagus to be pushed outwards to accept the bolus
Describe Peristalsis
involuntary movement controlled by the medulla oblongata in brain
Describe the placement and role of the cardiac sphincter - 6 points
found at the lower end of the oesophagus, opens to allow food to enter the stomach, it prevents hydrochloric acid (HCl) in stomach refluxing into oesophagus - necessary because the acid is harmful to the lining of the lower end of the oesophagus, if theres a malfunction of the sphincter the patient will present with ‘oesophageal reflux’ - smoking and alcohol relax the sphincter which can worsen the problem
Name the 6 parts of the stomach and their positioning
Cardia - surrounds the lower oesophageal sphincter Fundus - above and left of Cardia Body - large, central portion Pylorus - narrow, inferior portion Lesser Curvature - concave medially Greater Curvature - convex laterally
Describe the walls of the submucosa and serosa of the stomach
similar make up to the remainder of the GIT
Describe the mucosa inner lining of the stomach
lies in folds = rugae (these can become damaged if the stomach is ulcerated), contains gastric glands which secrete digestive enzymes and intrinsic factor (for B12 absorption)
Name the 3 types of fibre that makes up the muscularis layer of the stomach and their collective role
outer longitudinal, middle circular, inner oblique fibres
these help with gastric juices to mix the food into a consistency called Chyme
What does the stomach absorb
water, drugs and alcohol only
Describe the first part of the Mechanical/Chemical Digestion within the stomach (Pyloric and Fundus regions)
Peristaltic waves move the food round the stomach to enable mixing with the gastric juices and pushing the food eventually towards the pylorus and on into the duodenum, Food remains in the fundus for approx. 1 hour so amylase & lingual lipase can continue the breakdown of starch & fat
Describe the role of Hydrochloric Acid (HCl), Pepsin and Gastric Lipase in the mechanical/chemical digestion within the stomach
HCl within the stomach causes partial breakdown of proteins - stimulates the release of hormones to stimulate the bile release at a later stage of digestion
Pepsin is released within the stomach, breaks down peptide bonds within amino acids which make up proteins, works well in acidic environment but stomach lining produces mucous secretions which protect it from acid damage
Gastric Lipase splits triglyceride chains and so continues the breakdown of fats
Describe the basic features of the Small Intestine (SI)
2.5cm in diameter, 6.35m long, consists of duodenum (25cm), Jejunum (2.5m) and Ileum (3.6m)
Describe the Small Intestine (SI) - where it begins/ends - 3 points
opens at the pyloric sphincter from the stomach, curves around the head of the Pancreas - in close proximity to the liver and the gall bladder within this region, Finishes at the ileo-caecal valve where its becomes the large intestine
Describe the Pancreas and its Pancreatic Juice
lies posterior to the greater curvature of the stomach, pancreatic juice is released through the pancreatic duct, - enters the duodenum through the Sphincter of Oddi at the ampulla of Vater (hepato-pancreatic ampulla) - this is the exocrine function of the pancreas, sodium bicarbonate which neutralises acid and stops the action of amylase - also creates optimum conditions for small intestine enzymes to work
What does the pancreatic juice contain and its role
Pancreatic Amylase - to digest carbohydrates
Trypsin - protein digesting enzyme, doesn’t act on the walls of the pancreas and doesn’t become active until it mixes with enterokinase as it enters the small intestine
Pancreatic Lipase - principle triglyceride digesting enzyme
Nucleic Acid - digested by ribonuclease and deoxyribonuclease
