Lecture 25 Flashcards
What are the folds in the small intestine called?
Folds of Kerckring
What are the general layers of the GI tract working from the lumen out
Mucosa : Lamina propria (loose layer of connective tissue containing capillaries, lymph and immune cells, Muscularis mucosae (smooth layer), epithelia
Submucosa: loose collagenous connective tissue
larger blood vessels, lymphatics and nerves
glands
Muscularis externa: longitudinal smooth muscle
circular smooth muscle & enteric nerves are present between the muscle layer
Serosa: outermost layer Enveloping layer of connective tissue
Covered with layer of squamous epithelia cells
Describe the enteric nervous system
Consists of over 100miliion neurones. It is a reflex circuit that controls motility, secretion and absorption.ENS is located only in the GI tract, primarily the myenteric and submucosal plexus
Describe the structure of the stomach
It is hollow with gastric pits
What are the cells present in the gastric pits and their functions
Chief cells secrete pepsinogen (zymogen) hydrolyse peptide bonds
Parietal cells secrete acid
G-cells secrete gastrin
D-cells secrete somatostatin
How is HCL secretion regulated?
Vagus nerve stimulates parietal cell
Vagal stimulation of enterochromaffin-like cell (ECL) increases histamine release
G-cells secrete gastrin which promote acid secretion directly and indirectly
Somatostatin inhibits acid secretion
What is the function of mucus neck cells and surface epithelium cells?
Mucus neck cells and surface epithelial cells are important for protection
Mucus is secreted by mucus neck cells
HCO3- is secreted by surface epithelia
Mucus traps HCO3- forming a protective ‘mucus gel layer’
