Lecture 22 Flashcards
What does the gastrointestinal system act to do and what are its general structures?
The gastrointestinal system brings nutrients into the internal environment of the body so they can be used for processes such as growth or work. It consists of a long tube which is hard to tangle from the mouth to the anus and is open to the outside (meaning its lined with epithelium and connective tissue underneath it), it also contains many modifications to tissue structure and outgrowths (known as the accessory organs).
What are the outgrowths of the GI system and what are the general functions all organs will fit into.
The outgrowths (accesory organs) are the salivary glands, pancrease, liver and gallbladder and the appendix. The overall function of all parts of the GI system can generally be linked to motility, secretion, digestion and absorption.
What do the four general functions of the GI system involve?
Motility requires patterns of muscle movement, this contributes to digestion and absorption, secretion occurs throughout the GI tract via mucous, enzymes and hormones and involves the GI tract and accessory organs. Digestion breaks down food to allow absorption and is mechanical or chemical. Absorption is the transport of material from the intestinal lumen into the body, occurs in the small intestine mainly (nutrients and salt and water), the large intestine is for salt and water).
How is regulation done in the GI system?
Regulation of the GI system is done by the nervous system via the enteric nervous system (automatic and peripheral, this is the primary one). The CNS is involved when blood flow is wanted to be changed. Hormones are also present with receptors on the epithelial cells.
What is the structure of intestines at a cellular level and how is it held in place?
The intestines are slippery and structures of the gut are covered in peritoneum and held in place to the body wall by the mesentry (a thin moist membrane made from a double layer of peritoneal membrane). The peritoneum is a serous membrane (simple squamous epithelium with underlying thin layer of connective tissue, secretes serous fluid).
There is parietal peritonem over the body wall and visceral over the organs, between the two is a small space between known as the peritoneal cavity. The pancrease and deodenum have peritoneum on the dorsal surface but not the ventral and are known as retroperitoneal.
What is the omentum? How does it differ from a mesentry?
A double layer of peritoneal membrane from organ to organ. It differs because the mesentry is from body wall to organ instead.
What are the main vessels for the GI system and where do they go? Why does so much go to the GI tract?
There are three main vessels for the GI system, these are the celiac trunk (foregut, the left gastris, splenic and common hepatic), superior mesenteric(midgut, colic arteries, intestinal arteries and ileocolic artery) and inferior mesenteric (hindgut, left colic artery, sigmoid arteries and superior rectal artery). This was arranged by four weeks of development.
Lots of blood goes to the GI system despite the thinness of the GI tract, this is because the hepatic portal vein travels from here to the liver (hepatic circulation), this is where it is then metabolised.
There is a splenic vein, superior mesentric vein and inferior mesentric vein which flows into the hepatic portal vein.
