BIO Exam 2: Digestion (2) Flashcards
Partially digested food has left the stomach…
Joined in small intestine by
- HCO3- from pancreas
- Proteases from the pancreas
- Lipase from pancreas
- Amylase from the pancreas
- Bile from liver/gallbladder
Hormonal Control of Digestion (1)
Coordination through hormone signals
Lowered pH in the small intestine causes some specialized cells to release secretin
Increases pancreas secretions including bicarbonate
pH raises, secretin production stops
Negative feedback regulation:
A stimulus produces a response that shuts off the stimulus
Hormonal Control of Digestion (2)
Presence of lipids causes other cells to release cholecystokinin (CCK)
Causes gallbladder to contract
Presence of nutrients later in the intestine leads to secretion of GLP-1
Inhibits stomach emptying
Decreases appetite
Small Intestines: 3 regions
Small intestine will give time for enzymes to finish digestion
Major site of absorption
Three regions:
duodenum, jejunum, and ileum
Small Intestine: Mucosa and Submucosa and Serosa
The mucosa secretes enzymes and absorbs nutrients
The submucosa contains blood vessels and nerves
Muscle layer, both circular and longitudinal
Serosa is a protective layer
Small Intestines: Function
Material is moved and mixed by segmentation
Rings of muscle
Every other one contracts
Moves food back and forth, mixing
Faster segmentation in duodenum leads to net forward movement
Small Intestine:____ and ____ to dramatically increase surface area
Villi and microvilli
Colon: Functions
Essentially all nutrients are absorbed in the small intestine
Indigestible material are left over
Large intestine (colon): recovers water and stores waste in rectum
Colon: Absorbtion
Epithelial cells absorb Na+ by simple active transport
Water follows by osmosis
Continuous cell loss
Stem cells in crypts
Microbiome: Definition
Home to a huge microbe community – gut microbiome
bacteria, fungi, viruses
500+ species, trillions of cells
Mutualistic & Commensal
