Introduction to the GI Tract Flashcards
What organs are included in the GI tract?
The “tube” itself:
- Oesophagus
- Stomach
- Small intestine
- Large intestine (colon)
- Rectum
- Anus
Other organs of digestion also included:
- Liver
- Pancreas
- Galbladder
Purpose of the mouth in the GIT?
- Mastication
- Begins digestion with amylase
- Some absorption
Three stages of the pharynx?
- Nasopharynx
- Oralpharynx
- Laryngopharynx
Tip: Naso - nose
Oral - mouth
Laryngo - close to larynx
Function of the pharynx in the GIT?
Swallowing of food form the buccal cavity to the oesophagus
What is peristalsis?
The process of the involuntary contraction and relaxation of the muscles throughout the GI tract
Muscles of the Oesophagus
- Upper third are striated (voluntary)
- Lower third smooth (involuntary)
- Middle mixed
Sphincters of the oesophagus?
- Upper oesophageal sphincter - stops air getting into the GI
- Lower oesophageal sphincter - stops acid reflux
What is a hiatal hernia?
A hiatal hernia occurs when the upper part of the stomach pushes up into the chest through a small opening in the diaphragm, the muscle that separates the abdomen from the chest.
Sections of the stomach
- Cardia
- Fundus
- Body
- Antrum
- Pylorus (here is the pyloric sphincter after which is the small intestine)
Parts of the gastric mucosa
- Glands: secrete mucous to protect gastic mucosa form acidic environment
- Chief cells: secrete enzymes
- Parietal cells: secrete hydrochoric acid and intrinsic factor
- Endocrine cells: secrete grelin and gastrin
What do the gastric mucosa glands do?
Secrete mucous to protect the gastric mucosa
What do the chief cells do?
Secrete enzymes (pepsinogen)
What is the main enzyme in the stomach?
Pepsin
What do the parietal cells do?
Secrete hydrochloric acid to break down foods and intrinsic factor for b12 absorption
What do the endocrine cells of the gastric mucosa do?
Secrete grelin (hormone which promotes appetite) and gastrin (digestive hormone)
What is grelin?
The hormone that promotes appetite
What is gastrin?
The hormone that tells you body to digest - enhancing gastric mucosal growth, gastric motility (movement) and secretion of hydrochloric acid (HCl) into the stomach
What is the hormone that promotes appetite?
Grelin
What is the hormone that triggers digestion?
Gastrin
Three sections of the small intestine?
- Duodenum
- Jejunum
- Ileum
Hint: All end in “um” for “yum” and Ileum is the closest to the Ilium of the pelvis
What are the villi?
These are the folded mucosa lining the small intestine
Folded to increase surfact area
Contains blood vessels for most nutrient absorption and lymph vessels for fatty (lipid) nutrient absorption. Lympth is part of the immune system but is also fatty
Also secretes mucus and enzymes
Millions of them and looks like carpet (gross, is this the bit of cow I ate in mexico?)
Sections of the large intestine?
- Cecum
- Ascending colon
- Transverse colon
- Descending colon
- Sigmoid colon
What is the rectum?
Last bit of the GI - a repository for stool
What are crypts?
Like the villi but for the colon
Functions of the large intestine vs the small intestine?
- Small intestine is responsible for some digestion as well as nutrient absorption
- Large intestine releases no digestive enzymes. Absorbs water and electrolytes and eleminates faeces
How are the muscles of the colon grouped?
They are grouped into dense strips and rings called taeniae coli, these form pouches
What is the peritoneum?
A continous membrane that cover most abdominal organs
Two layers of the peritoneum?
- Viseral - lines the organs
- Parietal - lines the walls of the abdominal cavity
Where is the gallbladder?
Below the liver
What is the function oft he gallbladder?
Stores bile which is crucial for fat absorption
When triggered by hormone CCK it empties
Where is the pancreas?
Head lies within the curve of the duodenum. Tail touches the spleen.
The exocrine pancreas
- Form majority of pancreatic tissue
- Ductal collecting system that ends in the duodenum
- Secrete pancreatic juice (digesting enzymes and sodium bicarbonate to neutralise stomach acid)
The endocrine pancreas
- Consists of “islands” of endocrine cells called islets
- Secretes hormones intot he capillaries
- Most importantly insulin and glucagon
What do the alpha and beta cells do in the pancreatic islets?
- Alpha makes glucogon
- Beta makes insulin
What do the peritoneum terms mean?
- Intraperitoneal
- Extraperitoneal
- Retroperitoneal
- Mesentry
- Omentum
Why do we need to know about the peritoneum
- Perforation
- Peritonitis
