GI tract structure and motility Flashcards
what are the layers that make up the GI tract?
(starting with innermost) the mucosa (lines the lumen), the submucosa, muscularis externae, serosa.
there are also mesenteries
what are the layers of the mucosa?
mucous membranes, lamina propria and muscularis mucosae
what is structure of the mucous membranes of the mucosa?
it is made of enterocytes which include absorptive cells, exocrine cells, endocrine cells and G cells.
what is the structure of the lamina propria of the mucosa layer?
connective tissue, contains small blood vessels and lymph vessels and nerves, allowing it to protect against disease.
what is the structure of the muscularis mucosae of the mucosa layer?
it is a thin layer of smooth muscle that fold the mucosa to aid with mixing of the lumen contents.
how is the mucosa specialised for the stomach vs the small intestine?
stomach mucosa is thicker to protect against low pH and also has a smaller surface area than the small intestine as less absorption takes place here. small intestine has lots of villi to increase the surface area.
what is the structure of the submucosa?
thick layer of connective tissue, it is elastic and distensible. contains large blood vessels and lymph vessels and nerves which make up the submucosal plexus
what is the structure of the muscularis externae?
has 2 layers of smooth muscle. function of motility. has inner circular muscle and outer longitudinal muscle which contract and push lumen content along GI tract.
coordination of these muscles is done through myenteric plexus of the ENS
what is the structure of the serosa?
has 2 layers: inner fibrous connective tissue and an outer mesothelium layer. mesothelium secretes fluid allowing organs to glide.
what is the enteric nervous system?
a system of nerves embedded within the GI tract. consists of the submucosal plexus and the myenteric nerve plexus.
controls motility.
outline motility of the GI tract.
largely automatic (controlled by ANS) it involves reflex arcs which control action reflexes.
what happens when GI receptors detect a stimulus?
signal is received by the GI effectors (smooth muscle, exo/endocrine glands) this produces an effect which leads to movement of the GI tract to mix stomach contents
what is meant by segmentation?
muscle contractions occur in alternating segments
what is meant by peristalsis?
GI content is pushed along GI tract through circular muscle contraction (restricts lumen diameter) and longitudinal muscle contraction (shortens GI tract).
