gI motility Flashcards
Name the three main salivary glands and their relative contribution to saliva production
Parotid (25%)
Submandibular (70%)
Sublingual (5%)
What is the largest part of the small intestine?
Ileum
What are the three main methods of movement seen in the GI tract?
Propulsive movement, mixing movement and tonic contraction.
Describe propulsive movements?
Peristalisis (contraction of the muscle behind and dilation in front)
Describe tonic contractions
A large amount of skeletal muscle contracts simultaneously, for example in defecation.
What is the purpose of secretion throughout the GI tract?
Digestion and protection
What do digestive secretions contain?
Water (from plasma)
Electrolytes
Organic compound (bile salts, mucus etc)
What is the purpose of mixing movements?
To break down and give a larger surface area, for enzymatic attack
Describe the layers of the gut wall front he lumen outwards:
- Mucosa
- Muscularis mucosae
- Submucosal plexus
- Submucosa
- Circular muscle
- Myenteric plexus
- Longitudinal muscle
- Serosa
What are the major physiological functions associated with the mouth?
Lips: containment of food
Teeth: Chewing to break down food, stimulation of taste buds
Palate: Separates mouth from nasal passages
Tongue: Guides food and allows swallowing, contains taste buds
Pharynx: Common passageway for reparatory and digestive tracts.
Give 6 functions of saliva
- Lubrication
- Solvent
- Antibacterial
- Beginnings of complex carbohydrate digestion
- Neutralization of acid
- Facilitates sucking by infants
What does saliva contain that gives it is antibacterial properties?
Lysozyme, lactoferrin and antibodies
What does saliva contain that allows it to neutralise acid?
Bicarbonate
What are the two stages of saliva formation and where do they occur?
- Primary secretion by acinus
2. Secondary modification by the duct cells
How are the components necessary for primary secretion moved?
Active transport
What is the main purpose of the secondary modification stage?
A diluting stage.
Sodium and chlorine are removed to a large extent and potassium and bicarbonate are added but to a lesser degree.
There is no addition of water.
How much saliva do we usually produce whilst asleep, normally and during active salivation?
Sleep = 0.05 ml/min Rest = 0.5ml/min Active = 5ml/min
By what two neuronal reflexes int he rate of saliva production increased by?
- Simple reflex
2. Conditioned/acquired reflex
Describe the simple reflex for saliva production
Chemo/pressure receptors in mouth sense presence of food
Impulses are then sent via afferent nerves to the salivary centre in the medulla
This then sends impulses via extrinsic autonomic nerves (sympathetic and parasympathetic)
Salivary glands will increase production
Describe the conditioned reflex for saliva production
Though/smell of food is sensed in the cerebral cortex
This is then sent to the salivary centre in the medulla
This then send impulses via autonomic nerves
Salivary glands increase production
What is the dominant tone in normal saliva production? What receptor mediates this?
Parasympathetic.
M3 muscarinic acetylcholine receptors
Whate nerves are part of the parasympathetic stimulation of saliva?
Glossopharyngeal and facial
What is the consistency of the saliva in the parasympathetic response?
Large volume
Watery
Rich in enzymes
What nerves mediate the sympathetic response for salivary production? What receptor is the mediator of this?
Postganglionic fibres from superior cervical ganglia
Beta 1 adrenoreceptors
