Gastrointestinal Lecture 1 Part 5 Intestines and Accessory Organs Flashcards
Anatomy of the digestive tract
What is the small intestine the primary site of?
Primary site of digestion and absorption.
- Highly specialized structure, evolved to maximize food absorption
What is digestion in the small intestine aided by?
Digestion aided by hydrolytic enzymes that breakdown dietary macromolecules (protein, fats & carbohydrates)
What is absorption in the small intestine facilitated by?
Absorption across intestinal epithelia facilitated by large surface area
What are the three sections of the small intestine?
- Duodenum (~20 cm)
- Jejenum (~2.5 m)
- Ileum (~3 m)
What are the layers of specialization for the small intestine surface area?
- tube
- circular folds
- villi
- microvilli
What is the surface area size of the small intestine?
Net result of these adaptations
= ~600-fold increase in surface area
= 250 – 300 m2
Increased surface area = ?
Increased surface area = maximized contact between intestinal contents and epithelium, facilitating digestion and absorption
Function of large intestine
Functions to store and concentrate undigested material, prior to its excretion
Large intestine anatomical segments
- Cecum
- Appendix
- Ascending colon
- Transverse colon
- Descending colon
- Sigmoid colon
- Rectum
cecum
“first part”, anatomical definition, where sphincter opens up to
- cellulose digestion in herbivores - have much larger cecum
Appendix
Thought to be vestigial, may act as “haven” for gut bacteria
What happens through the Ascending colon, Transverse colon, Descending colon, and Sigmoid colon
Absorption of ions, water; bacterial metabolism
- Digest what you cannot digest yourself
Rectum
Holds feces; contraction expels feces (defecation)
Function of accessory organs
In general, function is to secrete substances into the gastro- intestinal tract that aid digestion
What are the accessary organs?
- Salivary glands
- Liver
- Gallbladder
- Pancreas (exocrine)
What are the three saliva glands?
- sublingual salivary gland
- submandibular salivary gland
- Parotid salivary gland
Purpose of salivary glands
Secretion of water and mucous & amylase
Purpose of water and mucours secretion
moistens and lubricates food bolus
Purpose of amylase secretion
begins digestion of large carbohydrates into small units
Which accessory organs have related functions?
the liver and gallbladder
Where do the liver and gallbladder empty?
Both empty into small intestine via common bile duct which is where the join
Function of liver and gallbladder
- Liver: secretion
- gallbladder: stores bile (produced in liver), concentrates it (eliminates water), releases it during feeding
What does the liver secrete?
- Bile salts (facilitate fat digestion)
- Bicarbonate (neutralizes acidic chyme coming from stomach) so digestion can continue
- Organic waste products and trace metals (eliminated in feces)
How is the pancreas functionally unique?
part of the digestive system and endocrine system
exocrine pancreas
Exocrine pancreas part of the digestive system.
- Acinar cells secrete into the small intestine via the pancreatic duct
endocrine pancreas
Endocrine pancreas part of the endocrine system.
- Islets of Langerhans secrete hormones into the blood stream
Exocrine pancreatic secretions
- Bicarbonate (HC03-) acts to neutralizes the acidity of chyme
- Digestive enzymes important for breaking down different macronutrients
What are the digestive enzymes released by the pancreas?
> Carbohydrate: pancreatic amylase
> Protein: trypsin, chymotrypsin
> Fat: pancreatic lipase
