digestive system Flashcards
what is deglutination
swallowing
what is digestion
the mechanical and chemical process of breaking down food into smaller components to a form which can be used by the body
how long is the digestive system
around 9 meters
what is involved in digestion
the mixing of food with digestive juices, movement through the digestive tract, breaking down large molecules into smaller ones
where does the digestive tract begin
the mouth
what is the role of saliva in digestion
lubrication and to start digestion as amylase begins starch digestion
swallowing is initiated by what
receptors in wall of pharynx when food or drink is near the back of the mouth
what happens when receptor detect food at the back of the mouth
afferent impulses are sent to swallowing centre in the brain stem, the brainstem the relays the signal to the coordinator of the process. interrupting breathing
what are the 3 layers of the oesophagus
skeletal muscle (upper third), smooth muscle (lower 2 thirds)
what are both ends of the oesophagus closed by
sphincters
what are sphincters
circular muscles that open and close to allow the passage of substances and fluids
how is food moved down the oesophagus
by peristatic waves - which occur every 9 seconds
secondary peristalsis is where multiple peristaltic waves occur to move food down the oesophagus
what does the epiglottis do during swallowing
it moves to cover the trachea to ensure food doesn’t go down the wrong passage causing choking
what is peristalsis
a series of mini contractions which occur in the oesophagus that push food down into the stomach
how does peristalsis push food down the oesophagus
circular muscles contract behind the food pushing it a long, this follows by the contraction of longitudinal muscles ahead of the food mass, then further contraction in circular muscles forces food mass forward
what is the role of the lower oesophageal sphincter
it opens to allow food to pass into the stomach and closes behind it to prevent it coming back up
what are the main parts of the stomach
fundus, body and antrum
give an example for mechanical digestion in the stomach
muscle contractions in the stomach wall
give an example for chemical digestion in the stomach
enzymes and acid, activates enzymes, mucous protection
what are the 4 sections the stomach can be divided into
cardia, fundus, body/corpus, pylorus
what is the cardia section of the stomach
where the contents of the oesophagus empty into the stomach
what is the fundus section of the stomach
formed by the upper curvature of the organ
what is the body/cardia section of the stomach
the main central region
what is the pylorus section of the stomach
the lower section of the organ that facilitates emptying the contents into the small intestine
what are the 3 mechanical tasks of the stomach
Stores the swallowed food and liquids - this is done by the upper muscles relax to allow large volumes of swallowed materials
Mix up the food, liquid and digestive juice produced by the stomach - lower part of the stomach mixes these materials by its muscle action
Empty the contents of the stomach slowly into the small intestine
what enzyme does the stomach secrete
protease (which is a protein digesting enzyme)
what is partially digested food known as
chyme
what does chyme pass down through to get to the location for the extraction of nutrients
through the pyloric sphincter and into the duodenum of the small intestine, where the extraction of nutrients will begin
how long does it take the stomach to digest food into chyme
40 mins to a few hours
what is the movement and flow of chemicals into the stomach controlled by
the autonomic nervous system and by various digestive hormones
what is gastrin released by
G - cells in the stomach in response to distension of the antrum and digestive products
what is gastrin inhibited by
pH less than 4 (high acidity)
