Upper GI tract Structure & Function Flashcards
How is chewing controlled?
Voluntarily: Somatic nerves act on skeletal muscles of the mouth and jaw
Reflex: pressure of food against gums,hard palate and tongue causes mechanoreceptors to inhibit jaw muscles so reduced pressure causes contraction etc
What pairs of glands secrete saliva?
parotid, submandibular and sublingual
What’s in saliva?
Water, mucins (protein component), alpha-amylase (breaks polysaccharide into disaccharide),electrolytes and lysozyme (bacteriocidal)
What types of alveoli are there?
Mucous alveoli, serous alveoli and mixed
What controls salivation?
Parasympathetic: Cranial nerves 9 and 7 (glossopharyngeal and facial) to create watery salivary secretion
Sympathetic: High mucus content from alpha 1 adrenoreceptors and high amylase content from beta 2 adrenoreceptors
Reflex control: Presence of food in mouth causes stimulation of chemical and pressure receptors
What are the layers of the oesophagus?
Mucosa, submucosa (contains glands), muscularis externa and adventitia
What cells found in mucosa?
stratified squamous epithelium (non-keratinised).
What layers of muscle are found in muscularis externa?
- upper 1/3 (superior) = skeletal muscle
- lower 2/3 (inferior) = smooth muscle
What regulate movement of material into and out of oesophagus?
Upper and lower oesophageal sphincters
In pahryngeal phase of swallowing what hapens>
Sequence fo reflex contactions of pharyngeal muscle that is coordinated by the medulla so that the soft palate reflects backwards and upwards to close off nasopharynx
What happens as blous approaches oesophagus?
Upper oesophageal sphincter relaxes and epiglottis covers opening to larynx (prevents food from entering trachea) and after food enters oesophagus UOS contracts to prevent reflux
How does food move along oesophagus?
Peristalsis
What happens as bolus nears stomach?
Lower oesophageal sphincter relaxes
what do vagal reflexes do?
Relaxation of thin, elastic smooth muscle of gastric fundus and body in order for stomach volume to change
What are the functions of the stomach?
Temporary store of ingested material, dissolve food particles and initiate digestive process, controls delivery of contents into small intestine, Sterilise ingested material, Produces intrinsic factor
