GI Lecture 1 Flashcards
List, in order, the major parts of the GI tract.
Mouth, Pharynx, Esophagus, Stomach, Small intestine, Large intestine
How does the esophagus transfer food to the stomach?
Via peristaltic waves, from the upper esophagal sphincter to the lower esophagal sphincter
What are the three sections of the stomach?
Fundus, body and antrum
What is the sphincter at the end of the stomach called?
Pylorus
What are the two regions of the stomach?
Orad (top), and caudad (bottom)
What is the liquid contents delivered to the duodenum called?
Chyme
What do cells in the stomach secrete?
mucous fluid, enzyme precursors, HCl, and hormones
What are the parts of the small intestine?
Duodenum - a short section that recieves secretions from the pancreas and liver via the pancreatic and common bile ducts
Jejunum - roughly 40% of the small gut
Ileum - empties into the large intestine, about 60%
What are the main structural differences between the jejunum and ilium?
The jejunum has a larger diameter, thicker wall, more prominent circular fold and a less fatty mesentery.
What are the parts of the colon, in order?
(iileum) Cecum, Ascending colon, transverse colon, descending colon, sigmoid colon (rectum)
What are the functions of the colon?
- Re-absorbs water that was used in the digestion process and substances that were used in digestion.
- Stores and concentrates feces before defecation
What are the four main accessory organs to the digestive system?
Salivary glands, liver, gallbladder, and pancreas.
What are acini?
The basic secretory units of salivary glands, which are composed of clusters of secretory cells.
What are the three major salivary glands?
Sublingual, Submandibular, and Parotid
What controls secretion of saliva?
The ANS (volume and type of saliva)
What are the exocrine functions of the pancreas?
Secretion of digestive enzymes that break down nutrients and secretion of HCO3- which neutralizes chyme, both to the duodenum.
What are the endocrine functions of the pancreas?
Insulin and glucagon secretion.
What are two main functions of the liver?
1, Stores and releases nutients that have been absorbed by the digestive tract.
2. Produces and releases bile which is important in fat digestion.
What are the two main functions of the gallbladder?
- Stores and concentrates bile between meals
2. Releases bile to assist in the digestion of fat
What is the submucosa?
The connective tissue, glands, blood vessels and nerve trunks in the GI tract wall
What is the muscularis externa?
The outer region of the GI tract wall, which has two types of contractions:
- Circular muscle contraction to induce a decrease in diameter of gut lumen
- Longitudinal muscle contraction to induce shortening of a segment of the GI tract
What is the muscularis mucosae?
The innermost muscle layer that allows mucosa to fold and form ridges.
What are the myenteric and submucosal plexi?
Two layers of nerve cells in the GI tract wall that comprise the ENS.
How do most molecules get absorbed?
The villus, which they diffuse through, into a capillary network inside the villus, and then get into systemic blood
What does the central lacteal of the villus do?
Transport fats into the lymphatic vessel, to drain the fat from the intestine and rapidly flow into blood via the thoracic duct
Describe blood flow (splanctic circulation)
Blood supply to the intestine carries water soluble nutrients.
Must first flow to the liver via the portal vein (to detoxify any bacteria)
Which sphincters are smooth muscle and under involuntary control?
All but the external anal sphincter and upper esophagal sphincter, which are under the control of the CNS.
Describe the resting pressure of sphincters
Positive
Where is the illeocecal valve?
Between illeum and cecum.
Where is the Sphincter of Oddi?
To gallbladder/pancreas from small gut
