Upper GIT Structure and function Flashcards
What is the voluntary control of chewing?
Somatic nerves - skeletal muscles of mouth/jaw
What is the reflex control of chewing?
Increased pressure of food on gums, hard palate, tongue triggers mechanoreceptors to inhibit jaw muscles
From where is saliva secreted?
3 pairs:
Parotid glands
Submandibular glands
Submental glands
What is in saliva?
Water a-amylase Lysozyme Mucins Electrolytes
What is the role of water in saliva?
Soften/moisten food
Dilute particles
Act as solvent
What is the role of mucins in saliva?
Combine with water to form mucus
Viscous solution acting as lubricant
What is the function of a-amylase in saliva?
Hydrolyse a-1,4 glycosidic bonds
Catalyse polysaccharides
What is the role of electrolytes in saliva?
Maintain tonicity
Regulate roughly neutral pH
What is the role of lysozymes in saliva?
Bacteriocidal
cleaves polysaccharide of bacterial cell wall
What types of glands are the salival glands?
Exocrine
What types of alveolus are present in the salivary glands?
Mucus alveolus
Serous alveolus
Mixed alveolus
What is the function of mucus alveoli?
Produce mucins
What is the function of serous alveolus?
Produce proteins
What nerves control parasympathetic salivary secretion?
VII (Facial)
IX (Glossopharyngeal)
What is the effect of parasympathetic stimulation on the salivary secretion?
Profuse watery salivary secretion
What is the effect of sympathetic stimulation on the salivary secretion?
Small volume of highly viscous saliva
alpha1 adrenoreceptor stimulation has what effect on saliva?
High mucus content
alpha2 adrenoreceptor stimulation has what effect on saliva?
High amylase content
What is the reflex control of salivary secretion?
Presense of food in the mouth triggers chemoreceptors and mechanoreceptors
How long is the esophagus?
25cm
What are the histological layers of the esophagus?
Mucosa
Submucosa
Muscularis externa
Adventitia
What type of epithelium lines the esophagus?
non-keratinised stratified squamous epithelium
Are there glands present in the submucosa of the esophagus?
Yes
What types of muscle is present in the esophagus?
Upper 1/3 - skeletal muscle
Lower 2/3 - smooth muscle
What is the function of the upper esophageal sphincter?
Stops regurgitation
What is the function of the lower esophageal sphincter?
Stopping reflux
Describe the oral phase of swallowing
Voluntary
Bolus pushed to the back of the mouth by the tongue
Describe the pharyngeal phase of swallowing
Presence of bolus causes reflex contractions of pharyngeal muscles
Soft palate reflects backwards (closing nasopharynx)
Where is the pharyngeal phase co-ordinated
Swallowing centre (medulla)
How does the esophagus respond as the bolus approaches?
Upper esophageal sphincter relaxes and epiglottis covers laryngeal opening
How does the esophagus respond as the bolus enters?
Upper oesophageal sphincter contracts, closing the opening
Describe the oesophageal phase of swallowing
Propulsion of bolus via peristaltic wave (10sec)
Describe the peristaltic wave
Contraction of muscle behind the bolus and relaxing muscle ahead
How is the receptive relaxation of the stomach initiated?
Initiated by relaxation of the lower oesophageal sphincter
What is the vagal response of this?
Relaxation of the thin, elastic smooth muscle of the fundus and body
What are the volume changes of the stomach
50ml –> 1500ml
What are the pressure changes of the stomach upon receiving food?
None
What is the non-compensatable factor of the stomach?
Production of Intrinsic Factor
Where does adventitia end and serosa begin?
Passing the diaphragm
What is the most superior, hollow area of the stomach called?
Fundus
How many layers of muscle has the stomach? Name them
3 layers
Longitudinal Muscle
Circular Muscle
Oblique muscle
What is the function of the oblique muscle of the stomach?
Contract to wring out the stomach, creating additional torque
What is the area where the oesophagus reaches the stomach called?
Cardiac region
What is the final part of the stomach called?
Pyloric region
What stomach structure controls outflow of the stomach into the duodenum?
Pyloric sphincter
What are rugae?
Folds in the submucosa and mucosa which stretch when filled