GI structure and Fx Flashcards
How is chewing controlled?
Voluntary - somatic nerves
Reflex - contraction of jaw muscles leads to mechanoreceptors inhibiting jaw muscles
what are the Three phases of swallowing?
oral, pharyngeal, oesophageal.
What is the oral phase?
Voluntary phase in which the bolus is pushed to the back of the mouth by the tongue.
What is the pharyngeal phase of swallowing?
bolus start a sequence of reflex contractions of pharyngeal muscles, coordinated by swallowing centre in medulla.
soft palate is reflected backwards and upwards to close off the nasopharynx.
UOS relaxes and epiglottis covers larynx -> once entered UOS contracts blocking reflux
What is the oesophageal phase?
Bolus propelled down via peristalsis LOS relaxes
Bolus enters stomach
What innervates the stomach to relax and expand?
The vagus nerve
Name 5 fx of stomach?
Temp Storage Digestion Prod of B12 via Intrinsic factor Sterilise Control delivery to SI
What extra muscular layer is in the stomach?
Oblique = inner most
What constitutes saliva?
Water, mucin, alpha amylase, electrolyes and lysozymes
What is salivary secretion controlled by?
Parasympathetic Crn 7 and 9
Sympathetic = small volume of viscous secretion (high mucous (alpha 1 adrenoreceptors) and amylase (beta 2 adrenoreceptors))
Reflex control prod by mechano and chemoreceptors on mouths walls
Which salv gland is the biggest?
Parotid
what is the of lysozymes?
Bactericidal - cleaves polysacharide cmpnt of bact cell wall
What are the three main types of salivary alveoli?
Serous, mixed and mucous
What does serous cells secret?
Protein
What do mucous cells secrete?
Mucous and H20
