Physiology Flashcards
What do the words oral and aboral mean?
oral means moving towards the mouth
aboral means moving away from the mouth
What are the parts of the small intestine?
duodenum, jejunum and the ileum
What are the parts of the large intestine?
caecum, appendix and colon (ascending, descending, transverse and sigmoidal)
What are the accessory organs of the digestive tract?
- salivary glands
- pancreas (makes digestive enzymes)
- liver (makes bile)
- gallbladder
What are the layers of the digestive tract wall?
- mucosa
- submucosa
- muscularis externa
- serosa
What does the mucosa consist of?
- mucous membrane (epithelial, exocrine and endocrine gland cells)
- lamina propria (capillaries, enteric neurones and gut-associated lymphoid tissue)
- muscularis mucosae
What does the submucosa consist of?
connective tissue, larger blood and lymph vessels, glands and submucous plexus
What does the muscularis external consist of?
mostly smooth muscle consisting of circular muscle and longitudinal muscle and between is the myenteric plexus
What does serosa consist of?
connective tissue
What are the four main functions of the alimentary canal?
- Motility: mechanical
- Secretion: required for digestion, protection and lubrication
- Digestion: enzymatic hydrolysis of food
- Absorption: transfer of products into blood or lymph
What places use skeletal or smooth muscle?
skeletal= mouth, pharynx, upper oesophagus and external anal sphincter smooth= everywhere else
What type of change does the circular muscle cause?
lumen becomes narrower and longer
What type of change does the longitudinal muscle cause?
intestine becomes shorter and fatter
What type of change does muscularis mucosae cause?
change in area for absorption and secretion and it causes a mixing motion
What is smooth muscle made up of (cells and their connections)?
small cells connected by gap junctions making a low-resistance pathway so there is a single-unit sheet of smooth muscle
What is spontaneous contracting activity driven by in the GI tract and what is it modified by?
driven by pacemaker cells
modulated by intrinsic/extrinsic nerves and hormones
What does slow wave electrical activity determine in the GI tract?
frequency, direction and velocity of rhythmic contractions
What is slow wave activity driven by?
ICCs which are the pacemaker cells in the circular and longitudinal muscle layers which form gap junctions with themselves and smooth muscle cells
What is required for the slow wave activity to cause a contraction?
the depolarising waves only cause a contraction in the wave amplitude reaches threshold
What determines the force of the slow-wave-induced contraction?
the longer the wave is above threshold, the more action potentials will be fired off
the starting potential of the cell also has an effect on how long the wave is above threshold
What is the starting electrical potential of a cell determined by?
neuronal, hormonal and mechanical stimuli causing depolarisation
What is the parasympathetic innervation of the GI tract?
preganglionic fibres that synapse with ganglion cells in ENS
What influences does the parasympathetic part of the GI tract have?
Excitatory influences: increased secretion, blood supply and mechanical activity
Inhibitory influences: relaxing of sphincters and stomach
What is the sympathetic innervation of the GI tract?
preganglionic synapse in the prevertebral ganglia and postganglionic fibres which innervate enteric neurons and others