Digestive System Flashcards
Components, Layers of the Gut & Worms
What is the role of the digestive system?
It’s responsible for chemically and physically digesting large insoluble molecules into smaller soluble molecules, which can be absorbed into the blood stream,
And used for bodily processes (e.g. respiration, protein synthesis).
Buccal Cavity-
Chemical Digestion
Amylase breaks down starch and glycogen into maltose
Buccal Cavity-
Saliva
Moistens food and maintains pH (for enzyme activity)
Buccal Cavity-
Mechanical Digestion
The tongue moves food to the cutting and grinding surfaces of the teeth
Tongue rolls food into a bolus which is swallowed
Bolus
a ball like mixture of food and saliva that forms during chewing (mechanical digestion) which is swallowed into the stomach
It’s the same colour as the food eaten, and saliva gives it an alkaline pH
Oesophagus
A long tube which extends from the buccal cavity to the stomach.
It’s responsible for pushing the bolus into the stomach using peristaltic waves of muscle contraction. It’s also lubricated with mucus.
Layers of the gut
Serosa (outermost)
Muscle Layers
Sub-mucosa
Mucosa
Lumen
Serosa
The outer most layer of the gut made of a thick tough connective tissue to provide protection.
Muscle Layers
The second outer most layer of the gut. Used to contract in waves and squeeze food down (peristalsis)
Sub mucosa
The second inner most layer of the gut. Contains connective tissue, nerves, blood & lymph capillaries
Mucosa
Inner most layer of the gut. This area secretes mucus and can secrete digestive juices.
In the ileum it’s covered with microvilli to increase SA
Stomach
A J shaped organ found at the end of the oesophagus which physically churns up food using muscles from the stomach wall
It also chemically breaks down food by releasing gastric juices
Mucus
Produced by goblet cells throughout the digestive system (e.g. stomach) to lubricate food and protect organ walls from self digestion via enzymes
Gastric Juice
A digestive fluid produced within the stomach lining with an acidic pH made up of mainly HCl, mucus, endopeptidase (pepsin), lipase
What produces gastric juice?
Gastric glands in the mucosa
Oxyntic Cells
Produce hydrochloric acid (HCl) in the stomach which kills bacteria and lowers pH down to 2 (for optimum pepsin enzyme activity)
Pepsinogen
The inactive form of endopeptidase (pepsin) which is activated by HCl to break down polypeptides into peptides
Liver
Produces Bile