Gastro-Intestinal System Flashcards
State the three stages of swallowing
Voluntary stage, pharyngeal stage and oesophageal stage
What happens during the voluntary stage of swallowing
The tongue pushes food towards the ortho-pharynx
What happens during the pharyngeal stage of swallowing
The soft palate and uvula seal off the nasopharynx.
The larynx is raised and the glottis is covered and sealed by the epiglottis.
Breathing is suspended for 1-2 seconds
What happens during the oesophageal stage of swallowing
Mucous is produced to aid swallowing.
Food is moved via peristalsis.
Lower oesophageal sphincter opens to allow entry to the stomach
What is peristalsis?
The propulsion of food along the GI tract
What happens during perstalisis?
Food presses on the gut wall causing tension. This tension stimulates sensory neurons which is connected to neurons on either side. The muscle “behind” the stimulus contracts pushing the food along while the muscle “in front” relaxes to facilitate movement
What are the three salivary glands present in the mouth?
Parotis, submaxillary and sublingual
What does saliva contain and what is its function?
Mucous - lubricates food
Alpha-amylase - initiates digestion of carbohydrate
Give a brief summary of saliva production
Saliva is originally produced as an isotonic fluid. As the saliva passes through the salivary duct, ions are added and removed via ion channels present in the duct. The final composition of saliva depends on the rate of flow through the salivary duct
How is saliva production regulated in regards to the autonomic nervous system?
Parasympathetic - watery saliva, rich in amylase and mucous is produced
Sympathetic - blood flow to salivary ducts is reduced resulting in reduced secretion
Give an explanation for how a drug could cause dry mouth as a side effect.
If the drug interacts with the autonomic nervous system in a way that increases sympathetic output, dry mouth may be seen as a side effect.
Give a brief summary of the anatomy of the oesophagus
The upper third is made of skeletal muscle to aid swallowing. The middle third is made of a combination of skeletal and smooth muscle. The lower third is made up entirely of smooth muscle.
State the 4 levels of the anatomy of the GI tract
Mucosa, submucosa, muscularis and serosa
What are the three layers that make up the mucous and what are their functions
Epithelium - Absorbs digested food and secretes GI fluid
Lamina Propria - Contains blood vessels, lymph tissue and lymph nodes
Muscularis mucosa - Smooth muscle that folds, increases surface area
What makes up the submucosa?
Connective tissue, large blood vessels, secretory glands, meissners plexus (has ANS supply and partially controls secretions)
