Upper GI TRACT Flashcards
6 functions of the GI Tract?
Ingestion Mechanical processing Digestion Secretion Absorption Excretion
What is ingestion?
An active process involving conscious choice where materials enter the digestive tract
What does mechanical processing of the GI entail?
Crushing up of food so it can easily travel along the digestive tract (not needed in liquid foods)
Why is it important for food to be crushed up and therefore increasing it’s surface area?
Makes it easier and quicker for enzymes to break it down so the body can use it
What is digestion?
Chemical breakdown of food into small fragments which are absorbable by the digestive epithelium (protein molecules must be broken down to be absorbed)
What is secretion?
The release of water, acids, enzymes and salts by the epithelium of the digestive tract
What is absorption?
Movement of electrolytes/vitamins/water across the digestive epithelium and into digestive tract (into the interstitial fluid)
What is interstitial fluid?
Body fluid between blood vessels and cells - contains nutrients (from capillaries) and holding waste products (from cells after metabolism)
What is excretion?
The removal of waste from body fluids
What four layers make up the alimentary canal?
Mucosa
Submucosa
Muscularis externa
Serosa
What is the Mucosa?
The inner lining of the digestive tract (a mucous membrane - secretes mucous and hormones)
What is the alimentary canal?
A long muscular tube of organs (esophagus/stomach/intestine) running from the mouth down to the anus
What is the digestive tract made up of?
The alimentary canal and other digestive organs (liver/pancreas)
What is the purpose of the mucosa?
To absorb nutrients from the end products of digestion and also protect the system against infection
What is the mucosa surrounded by?
Digestive epithelium (either simple or stratified depending on which part of the GI tract it is lining)
What are PLICAE?
Transverse folds in the lining of the digestive tract which expand and disappear as the tract fills and empties
What is the purpose of PLICAE?
To increase the surface area - increasing the area available for absorption of liquids and nutrients
What is the LAMINA PROPRIA?
The external part of the mucosa (the inner lining), consisting of blood vessels/nerve endings/smooth muscle cells
What is the submucosa?
The second inner layer of the alimentary canal - joins the mucosa to the overlying covering muscle
What does the submucosa consist of?
Larger blood vessels, lymphatic vessels and exocrine glands
What is the Muscularis Externa?
The third layer of the alimentary canal, surrounding the submucosa
What is the purpose of the Muscularis Externa?
The smooth muscle layers control waves of contractions (peristalsis) which move boluses of matter from one part of the digestive system to another
What is peristalsis controlled by?
The parasympathetic division of the autonomic NS
What is the serosa?
The outer most layer of the alimentary canal
What surrounds the Serosa?
A serous membrane known as the visceral peritoneum
Which structures of the GI Tract do not have an outer Serosa layer?
The oral cavity, pharynx and oesophagus - these are attached to close structures by fibrous connective rissues (adventitia)
What are the two components of the superior (above) boundary of the oral cavity?
The hard palate and the soft palate
What are the 4 components of the posterior (back) boundary of the oral cavity?
Uvula
palatine tonsil
Root of the tounge
Lingual tonsil
What are the components of the inferior (below) boundary of the oral cavity?
The Geniohyoid and the Mylohyoid muscles - support the floor of the mouth
What are the the three components of the anterior (front) and lateral boundary of the oral cavity?
Labium(lip), cheek, body of the tounge
What forms the roof of the oral cavity?
The hard palate
How do the uvula and toungue work together?
The tongue covers the floor of the buccal cavity which joins the uvula to prevent food entering the pharynx prematurely
What are the four functions of the oral cavity?
Sensory analysis
Mechanical processing
Lubrication
Digestion
What lines the oral cavity?
The oral mucosa which has a stratified squamous epithelium
What are the main actions of the mouth/oral cavity?
To sense the food/material before swallowing, mash the materials into a bolus, mix with mucous/saliva to break down carbs and lipids
What is the mucosa of the cheeks supported by?
By pads of fat and buccinator muscles
What is the vestibule of the mouth?
The space between the teeth and the cheeks/lips
What is the gingiva?
The space between the teeth and the gums (small layer on/under bottom of teeth) -
What is the mouth responsible for?
Mechanical breakdown of food into a bolus before swallowing
What process does the mouth start off?
Chemical digestion
What is lingual lipase?
A digestive enzyme
What is the function of lingual lipase?
Starts the process of breaking down larger fatty chains into small bits before they enter the duodenum
What is the duodenum?
The first section of the small intestine, located between the stomach and the middle section of the small intestine
What is salivary amylase?
The primary enzyme in saliva
What is the function of salivary amylase?
Starts the process of breaking down carbohydrates (polysaccharides broken down to disaccharides)
What are the functions of the tounge?
Mechanical processing
Can bring food into the oral cavity
Forms words
Sensory organ for taste
What are the three surface features of the tongue?
Filiform papillae
Fungiform papillae
Circumvallate papillae
What is the purpose of the filiform papillae?
Provide roughness and grip
What is the purpose of the fungiform papillae?
Contains the taste buds
What is the purpose of the circumvallate papillae?
It is the boundary between the body and the root of the tongue
Where about on the tongue are the filiform papillae and the fungiform papillae?
Both are scattered over the main body of the tongue
What two sections can the tongue be divided into?
The pharyngeal (root), and the body (oral portion)
What is the dorsum?
The superior surface of the tongue
What are the lingual papillae?
Small projections on the thick epithelium of the tongue body which help move materials
What is the lingual frenulum?
A thin fold of mucous membrane which joins the inferior surface of the tongue to the base of the oral cavity
What PH does lingual lipase work well at?
3.0 - 6.0
Where can we detect bitter tastes?
Base of the tongue
Where can we detect sour tastes?
Middle of the sides of the tongue
Where can we detect salty tastes?
Extends down the sides from tip to the middle
Where can we detect sweet tastes?
On the tip of the tongue
What are the three pairs of salivary glands which secrete into the oral cavity?
Parotid
Sublingual
Submandibular
What do the parotid glands secrete into the oral cavity?
Salivary amylase
What do the sublingual glands secrete into the oral cavity?
Lubricant (buffer)
What do the submandibular glands secrete into the oral cavity?
Buffer, glycoproteins and amylase
What is a buffer?
Organic substances that maintain a constant PH over a given range by neutralising the effects of hydrogen ions
Where are the parotid glands?
In front of and just below each ear
What is the Stensen’s duct?
Where saliva drains from the duct (parotid gland) into the mouth
Where are the sublingual glands found?
In the floor of the mouth
Where are the submandibular glands found?
On both sides, just under and deep to the jaw, towards the back of the mouth
What is a crown?
Exposed portion of tooth covered with enamel
What is a root
The internal portion of a tooth beneath the gums, anchored by periodontal ligaments
What is the purpose of the teeth?
To further break down food, increasing its SA for digestion
What is the purpose of incisors?
Cutting and shredding food
What is the purpose of canines?
For piercing and tearing food
What is the purpose of premolars?
For grinding and crushing food
What is the purpose of molars?
For grinding food
Where are the incisors found and what is their structure?
The front of the mouth, blade shaped and single rooted
Where are the canines found and what is their structure?
In between incisors and premolars, conical with a pointed tip and single rooted
Where are the premolars found and what is their structure?
In between the canines and the molars, flattened crowns with prominent ridges (can have 1 or 2 roots)
Where are the molars found and what is their structure?
At the far sides, after the premolars - large flattened crowns (can have 3 or 4 roots)
What is the oesophagus?
A muscular tube, connecting the pharynx to the stomach
What characteristics does the oesophagus have?
25-30 cm
Lined with squamous epithelium which is then columnar epithelium when it meets the stomach
What does the oesophagus do?
Propels food from the oral cavity to the stomach
At what point does the bolus enter the stomach?
At the esophageal hiatus
What do the esophageal glands do?
Produce mucus to lubricate
What does the esophageal sphincter do?
Prevent back flow into the oral cavity
What does the cardiac sphincter do?
Prevents back flow into the esophagus
What are the phases of swallowing?
Oral stage
Pharyngeal phase
Oesphageal phase
What is deglutition?
Process of swallowing
What passageway allows for the swallowing of food/liquid and air?
Pharynx
What happens in the oral stage of swallowing?
The upper esophageal sphincter is contracted so the bolus of food remains in the oral cavity
What happens in the pharyngeal phase of swallowing?
The upper esophageal sphincter is relaxed so the bolus can pass down the esophagus
What happens in the oesophageal phase of swallowing?
The upper esophageal sphincter is contracted as there is no bolus of food that needs to pass down the esophagus
What is the purpose of the stomach?
Storage of ingested food
Mechanical breakdown
Action of acids/enzymes to break down food
Production of intrinsic factor
Where is the stomach located?
On the left hand side of the upper abdomen
What is intrinsic factor?
A glycoprotein - the presence is required for absorption of vit b12 in the small intestine
What is chyme?
When ingested materials combine with stomach acids/enzymes
What four regions is the stomach divided into?
The cardia, the pylorus, the cundus, the body
What is the cardia?
The smallest region of the stomach - contains many mucous glands to help protect the link to the esophagus from harmful stomach acids
What is the cundus?
The main portion of the stomach which touches the posterior diaphragm
What is the body of the stomach (description wise)?
The largest section of the stomach - acts as a mixing tank. Gastric glands are located in underlying mucosa and secrete the acids/enzymes for gastric digestion
What is the pylorus?
It connects the stomach to the duodenum (first part of small intestine)
What does the muscular pyloric sphincter do?
Regulates the release of chyme into the duodenum
What does the hormone gastrin do?
Regulates activity of the gastric glands
What two parts does the pylorus divide into?
The pyloric antrum (connects to body) and the pyloric canal (which empties into the duodenum)
Purpose of goblet cells in the GI tract?
Secrete mucus to coat the stomach and prevent it from being digested itself
Purpose of simple columnar epithelium in the GI tract?
Contains gastric pits which secrete gastric juices
Purpose of parietal cells in the GI tract?
Secretes hydrochloric acid 9converts pepsinogen into pepsin) and intrinsic factor (needed for vit B absorption)
Purpose of chief cells in the GI tract?
They secrete pepsinogen (gets converted into pepsin to help protein digestion)
Purpose of enteroendocrine cells in the GI tract?
Release hormones
Histamine?
Activates parietal cells to release HCI (Hydrochloric acid/gastric acid) - produced by enteroendocrine cells
Serotonin?
Aids contraction of stomach muscle - produced by enteroendocrine cells
Gastrin?
Gastric glands to increase secretion - produced by enteroendocrine cells
Secretin?
Inhibits gastric gland secretion and motility - produced by enteroendocrine cells
Endorphins?
Relieve stress and pain -natural opiates (opiates are drugs to relive pain)
Somatostatin?
Growth hormone-inhibiting hormone - involved in the sympathetic NS & inhibiting gastric secretion and emptying
What does gastric juice consist of?
Water Hydrochloric acid Pepsinogen Intrinsic factor Mucus
Why is water essential in the gastric juice?
Liquefies the food
Why is hydrochloric acid essential in gastric juice?
Acidifies food and provides acidic environment for pepsins activation
Why is pepsinogen essential in gastric juices?
Is converted to pepsin (an enzyme which digests proteins)
Why is intrinsic factor essential in gastric juices?
It is needed to absorb Vit B12 in the small intestine
Why is mucus essential in gastric juices?
Protects the stomach mucosa from any corrosive chemicals/enzymes
What are PPI (proton pump inhibitors)?
Something which stops the production of the H in hydrochloric acid in the stomach (reduces acid produced)
What is an example of a medically used proton pump inhibitor?
Omeprazole, Lansoprazole
How do proton pump inhibitors work?
Turns off proton pumps and reduces the amount of stomach acid
What do H2 blockers do?
Prevents the action of histamine on acid producing cells in the stomach (by blocking the histamine binding sites)
Examples of H2 blockers?
Zantac (Ranitidine)
Tagamet (cimetidine)
What are the 3 phases of gastric secretion?
Cephalic
Gastric
Intestinal
What is the cephalic phase of gastric secretion?
It is the 1st phase - stimulated by sight/taste/thought of food
What happens in the cephalic phase of gastric secretion?
Inputs from taste buds and olfactory receptors are sent to the parasympathetic enteric ganglia to stimulate stomach glands
What is the gastric phase of gastric secretion?
The second phase of gastric secretion
What happens in the gastric phase of gastric secretion?
Stretch receptors are activated
Food chemicals activate chemoreceptors to activate G cells which secrete gastrin
What is the intestinal phase of gastric secretion?
The last phase of gastric secretion
What happens in the intestinal phases of gastric secretion?
The presence of low PH and partially digested foods in the duodenum stimulates intestinal gastrin secretion
What are stomach ulcers?
A localised inflammation which destroys an area of skin/mucous membrane (mouth/stomach/duodenum)
What is a peptic ulcer?
Localised inflammation which has destroyed an area of skin in the duodenum or stomach
What is hepatitis?
Inflammation of the liver (caused by a virus or alcohol abuse)
Can cause jaundice (yellow of skin and eyes)
What is coeliac disease?
An autoimmune disease/intolerance to gluten
Damages villi in small intestine
What is Crohn’s disease?
Chronic inflammation of any parts of the GI tract. Causes pain/diarrhoea and often IBS and ulcers
