Lower GI Tract Flashcards
What is the purpose of the small intestine?
Receives chyme from the stomach, performs majority of digestion and absorbs nutrients
What three body parts make up the small intestine?
Duodenum, jejunum/lleuym, plicae circulares
What is the duodenum?
The upper region of the small intestine receives chyme/digestive enzymes/bile
What is the jejunum/lleum?
Lower region of small intestine where absorption occurs
What is the plicae circlares?
Permanent folds in the mucosa/submucosa which slows movement of chyme
What are villi?
Fingerlike projections that increase SA of the small intestine
What are microvilli?
Tiny projections on the plasma membranes of columnar cells (look fuzzy0
Functions of the large intestine?
Reabsorption of water/electrolytes
Production/absorption of vit B and K
Elimination of feaces
Teniae coli?
Bands of smooth muscle creating pocket-like sacs (haustra) in the large intestine
Caecum?
The sac like connection between the small and large intestines
Appendix?
Small structure containing lymphoid tissue
What four types of colon are there?
Ascending
Descending
Transverse
Sigmoid
What is the rectum for?
Temporary storage of food residues
Expandable structure
rectal valves slow movement
What is the anus for?
Regulates defecation
Where is the anorectal canal located?
Begins where the rectum penetrates the levator ani muscle
What are the two sphincters which control movement of faeces?
The internal sphincter (involuntary) and external (voluntary)
What are the 4 secretions of the small intestine?
Secretin, somatostatin, cholecystokinin, brush border enzymes
What is secretin?
Released by the enteroendocrine cells when acidic chyme enters the small intestine
What is somatostatin?
It is secreted by the small intestine and it slows gastric
What is gastric motility?
The movement of food through the digestive tract by rhythmic contractions
What is cholecystokinin?
A hormone released when chyme enters the SI - causes the release of pancreatic juices and bile
What do brush border enzymes do?
They process long peptides/nucleic acids/sugars intro smaller ones
What are the four layers of the GI tract made up of?
The mucosa, Submucosa, Muscularis externa, Serosa
What is the purpose of the mucosa layer of the GI tract?
Secretes hormones/mucus, absorbs end products of digestion and protects against infection
What is the purpose of the submucosa layer of the GI tract?
It contains lymphoid follicles and elastic tissue
What is the purpose of the muscularis externa layer of the GI tract?
Contains inner circular layer and outer longitudinal layer of this both control peristalsis
What is the serosa?
The outer layer of the GI tract surrounded by a serous membrane - also known as visceral peritoneum
What do goblet cells in the crypts do?
Makes surface slippery, protects lining, lubricates faeces
What tissue type primarily makes up the large intestine?
Simple columnar epithelium, except in the anal canal
What tissue type is present in the anal canal?
Stratified squamos
What do goblet cells do in the anal canal?
Lubrication of feces
What is the Teniae Coli?
Bands of smooth muscle that create pocket like sacs (In the LI)
What is the Caecum??
Sac like connection between the small and large intestines
What is the appendix?
Small structure on the bottom end of the ascending colon on the LI - containing lymphoid tissue (small immune function)
What four sections make up the colon in the LI?
Ascending, Descending, Transvers and Sigmoid Colon.
Where are each of the four sections of the colon in order in the LI?
Ascending colon- First section (going upwards)
Transverse colon - Second section (sideways along the top)
Descending colon - Third section (going downwards)
Sigmoid colon - Last section (closet to rectum and anus)
What is the hepatic flexure?
The right colic - separates the ascending and transverse colon
What is the splenic flexure?
The left colic - separates the transverse and the descending colon
What is the rectum?
Temporary storage of faecal matter
What are three functions of the large intestine?
Reabsorption of water and electrolytes
Production and absorption of vitamins B and K
Elimination of faeces
What is the anorectal canal?
It begins where the rectum penetrates the levator ani muscle
What is the structure of the anorectal canal?
Has longitudinal folds (rectal columns)
It has two sphincters which control the movement of faeces out of the body
In the anorectal canal, what is muscle makes up the internal and external sphincter?
Internal sphincter - smooth muscle (involuntary)
External sphincter - Skeletal muscle (voluntary)
What is the main difference between infancy/childhood defecation compared to adulthood defecation?
It is an involuntary act when younger which through learned behaviour becomes a voluntary act
What is the defecation reflex initiated by?
Through mass movements and stretching of rectal wall
