Layers Of The Alimentary Canal Flashcards
What are the 4 layers of the alimentary canal? (These have same structural arrangement throughout length)
Innermost to outermost
Mucosa
Submucosa
Muscularis exrterna
Serosa/adventitia
What are the 3 layers of the mucosa?
Epithelium
Lamina propria (loose connective tissue)
Muscularis mucosa (not much function)
What does stratified squamous mean
Squamous = cell that’s wider than it is high
Stratified = in layers that can be rubbed away
Where would you find stratified squamous epithelium
Mouth
Esophagus
Anal canal
What does simple columnar mean
All cells are in contact with base membrane (no stratification)
Columnar = taller than they are wide
Where would you find simple columnar epithelium
Stomach, small and large intestine
What is the role of the epithelium (3)
- forms barrier separating the lumen of alimentary canal from body
- synthesis and secretion of digestive enzymes, hormones and mucous
- absorb products of digestion
NOTE: epithelium differs along the length of the gut tube depending on function required
What is contained in the lamina propria
Glands, blood/lymph vessels
The epithelium sits on top of this
What is the role of Muscularis mucosae
Thin smooth muscle layer - only function is to support
What kind of tissue is the submucosa
Thick, irregular connective tissue
what does the submucosa contain and what’s its role
Supports mucosa:
- neurones
- blood vessels
- lymphatic vessels
what do submucosal glands in the oesophagus secrete
Mucous
What do submucosal glands in the duodenum secrete
Bicarbonate to neutralise stomach acid
What is the Muscularis externa
2 concentric thick layers of smooth muscle
Role of Muscularis externa
Produce motility (peristalsis and segmentation)
What is the serosa/adventitia
Connective tissue outer layer of alimentary Canal
What 2 autonomic reflexes control alimentary function
Long reflexes (parasympathetic)
Short reflexes (ENS)
What are long reflexes
Parasympathetic control of alimentary function
Afferent pathway goes all the way to CNS and back
What are short reflexes
ENS
Both afferent and efferent pathways don’t leave the gut
What does the parasympathetic control of alimentary function do
Rest and digest
What nerve parasympathetically controls everything below head and neck
CN 10 (vagus)
Exceptions to this is salivations (CN VII) & glossopharyngeal (CN IX)
What does parasympathetic (rest and digest) do to gut function
Stimulatory
Increased secretion & increased motility
What does sympathetic system do to the alimentary canal
Fight or flight
Inhibitory to gut function (except salivation)
Decreased secretin & decreased motility
