GUT Flashcards
What is the rough general pathway for food?
- Macstication–> Bolus –> pharynx–> larynx–> Oesophagus–> Stomach–> small intestine –> large intestine–> anus
What are the accessory glands?
- Salivary glands
- Liver (bile)
- tongue
- Pancreas (enzymes breaking down foods)
What is the inner lining of the gut called?
- Mucosa
What are 4 functions of the GI system?
- Nutrient absorption
- release/removal of waster
- Regulation of H2O and electrolytes to MAINTAIN BODY FLUID osmolarity
- Immune function (mucosa contains macrophages-IgA)
What moves food through the gut?
- MOTILITY –> propulsion through gut
- Smooth muscle contracts
How do we get muscle cells to contract?
- Excitation (APs)
- Smooth muscle cells at each section of the gut are COUPLED
What connects each smooth muscle cell?
- Gap junctions (one AP spreads through the whole unit)
- Via wave of excitation
What does the gut tube do when circular muscle contracts?
- It is CONSTRICTED (get narrower)
What does the gut tube do when the longitudinal muscle contracts?
- It SHORTENS
Before the bolus in the gut tube there is ___________ (type of constriction)
Before the bolus there is circular constrction
After the bolus in the gut tube there is ______ (type of constriction)
Longitudinal shortening
What is oesophageal peristaliss?
- Contraction and relaxation of circular and smooth longitudinal muscle layers–> motility
Which two sphincters are made up of skeletal muscle?
Upper oesophageal (1) - External anal sphincter (7)
Which spincters are made up of smooth muscle ?-
- Lower oesphageal
- Pyloric Sphincter (b/w bottom of stomach and start of small intestine)
- Sphincter of Oddi (hepatopancreatic)
- Ileocecal (b/w ileum and cecum)
- Internal anal sphincter
What are the internal sphincters in a constant state of?
- Constant state of constriction (maintained by SNS)
- Maintained by BOTH intrinsic enteric nerves and extrinsic nerves
What does the relaxation of these 5 sphincters result from?
ACTIVATION of parasympathetic nerves and INTRINSIC INHIBITORY nerves in myenteric plexus
Which types of nerves innervate the gut?
- SENSORY NERVES–> Chemoreceptors and mechanireceptors
- SOMATIC MOTOR NERVES –> Skeletal muscle (upper oesophageal and sphincter)
- AUTONOMIC NERVES–> Innervate glands and smooth muscle
- ENTERIC NERVES–> Also innervate glands and smooth muscle
In times of extreme stress what happens to the neuronal controls?
- They all go!!
What are the two intrinsic nerve plexuses that the enteric nervous system is comprised of?
- Myenteric Plexux
2. Submucosal plexus
What is the myenteric part of the ENS involved with?
- b/w circular and longitudinal muscle layers and runs along ENTIRE length of GUT (control MOTILITY)
What is the submucosal plexus involved with?
- in submucosal connective tissue, only in CERTAIN REGIONS, controls SECRETIONS, localised blood flow –> nutrient absorption
What happens to the motility with the sympathetic system and parasympathetic system respecitvely?
- Motility decreases (Sympathetic) and increases (parasympathetic)
What happens to the motility in the submucosal phase?
- There is NO CHANGE
What happens to motility in the myenteric system?
- EXCITATORY