What happens in the stomach? Absorption & Digestion Flashcards
The digestive system is responsible for the movement:
of nutrients into the body
Synthesizing compounds is
anabolism
Breaking down compounds to provide energy
catabolism
Two main parts of the digestive system are
- digestion
- absorption
What are the accessory organs of the digestive system?
salivary gland
Liver
Pancreas
Gallbladder
The accessory organs produce _____, _____ and _____ ______ that contribute to the breakdown of food
bile, saliva, digestive enzymes
Salivary glands : Secretion of _________ _______ containing enzymes that break down carbohydrates
lubricating fluid
Liver: Secretion of _____ (important for lipid digestion), storage of nutrients, many other vital functions
bile
Gallbladder: _______ and concentration of bile
storage
Pancreas: Exocrine cells secrete _____ and digestive enzymes; endocrine cells secrete hormones
buffers
Transit time:
amount of time it takes food to pass the length of the gastrointestinal tract, (time it takes for food to pass from mouth to anus).
Food Disassembly
______ and ______ processes deconstruct food into polymers
(macromolecules: CHO, Lipids, protein nucleic acid)
These further breakdown into __________
chemical and mechanical
GI tract & accessory organs work together in 6 steps:’
I
P
M
C
A
E
- Ingestion (oral cavity)
- Propulsion (pharynx, esophagus, stomach)
- Mechanical Breakdown (stomach)
- Chemical Digestion (accessory organs)
- **Absorption (small intestine)
- Elimination (large intestine)
Mechanical refers to:
using smooth muscle
Chemical refers to:
being enabled by accessory organs
Layers of GI tract
Plica Circulares: Folds increase _______ _______ for ________
surface area, absorption
Mucosa
Secretes ____
Absorption & ________
mucus
protection
Submucosa: Rich supply elastic fibers that enable stomach to regain ______ _______ after storing large meal
regain the normal shape
Muscularis externa:
Muscularis mucosae:
Smooth muscle cells involved with ________ materials along digestive tract (peristalsis)
moving
Serosa (visceral peritoneum)
Protective covering of muscularis externa
Path of Ingested Food: From Oral Cavity to Stomach
Mastication
Chewing (mastication) helps to do what to surface area?
Chewing helps to INCREASE surface area so its easier for enzymes to attach on. Bolus is then created.
Mastication
Saturates food with _______ ____/______
This forms a ________ and is swallowed
salivary secretions/enzymes
Bolus
Saliva
what is produced by saliva INITIATES the start of the breakdown of ______ _________
salivary amylase
complex carbohydrates
What is produced by the tongue that for the breakdown of ________
lingual lipase
lipids
T/F
Absorption DOES NOT occur in the oral cavity?
T
Pharynx connects to what?
Esophagus
What is the passage way for solid food, liquids, air from oral cavity to esophagus
Pharynx
Esophegeal sphincter:
prevents heartburn
Ingested substances combine with secretions of glands of stomach to form
chyme
Once bolus reaches the stomach, it forms into
chyme
functions of the stomach
S
M
C
I
Storage
Mechanical breakdown
Chemical breakdown
Production of intrinsic factor
intrinsic factor (glycoprotein) :
Required for intestinal absorption of
vitamin B12
4 parts of the stomach
Fundus, Body, Pylorus, Cardia
Fundus and Body: Gastric Glands
Secretes ________ (prevents stomach from being digested)
muscus
Fundus and Body: Gastric Glands
Parietal cells: secretes ____ ____ (required for absorption of vitamin B12) & _______ _____
intrinsic factor, hydrochloric acid (HCL)
Chief cells: produces __________(makes _______ when combined with ______ -> digests proteins)
pepsinogen, pepsin, HCL
Pylorus: Pyloric Glands
secrete ______
mucous
Pylorus: Pyloric Glands
G-cells: secretes ________ (stimulates parietal cells to secrete HCl)
gastrin
D-Cells: secrete
_________ (inhibits release of gastrin)
somatostatin
What does the secretion of gastrin from g-cells do?
stimulates parietal cells to secrete HCL. This HCL is super important because HCL binds with pepsinogen to make pepsin, which is then used to digest proteins.
stomach protects itself from self digestion using a ______ _______
mucosal barrier
ACID reflux from stomach backs up into _________
Under normal conditions your ________ _________
esophagus
esophageal sphincter
Summary:
Digestion from Oral Cavity to Stomach
Salivary amylase & lingual lipase – digestion of _________
Pepsin digestion of the _______
CHO and lipids
proteins
As ph decreases, pepsin activity _________, this is when what begins
increases
protein disassembly
are nutrients absorbed in the stomach?
NOOOO
CHO, lipids, proteins only ________ broken down in the stomach
partially
Stomach Emptying
Large meal: more ________ will stimulate release of _____ ______ and gastric motility. Therefore, gastric emptying is ________
Small meal: absence of ________, little stimulus for gastric motility; gastric emptying ________
distension
gastric juice
Fast
distensions
slow
What stimulates gastric juices and motility?
distension
What is the main source of digestion and absorption?
small intestine
Duodenum
What is released in response to chyme arrival (esp. when high in lipids)
released in response to chyme arrival
secreted when exposed to large quantities of incompletely digested proteins
Cholecystokinin (CCK):
secretin
pepsin
Gallbladder
stores what ?
Bile
Bile necessary for ________of dietary fats
emulsification
Emulsification is when fats are physically ______ into small little fat droplets
separated
Emulsification also increases _______ _______ so enzymes can act on them
surface area
If gallbladder removed:
bile production continues but is more dilute and entry into small intestine not closely tied to arrival of food in duodenum
explain why bile is important in 4 steps:
- Liver secretes bile
- Bile becomes more concentrated the longer it remains in the gallbladder.
3.The release of cck by the duodenum triggers contraction of the gallbladder and opening of a sphincter. the ejects bile into the duodenum - Bile salts then break down lips droplets through a process called emulsification.
Hormone CCK is secreted in response to what arrival at the duodenum?
chyme
When is bile released into the duodenum?
under stimulation of CCK
Pancreatic enzymes
- Pancreatic alpha-amalyse
- Pancreatic lipase
Proteolytic enzymes
- Pancreatic alpha-amalyse breaks down what?
- Pancreatic lipase breaks down what?
Proteolytic enzymes breaks down what?
starches
- lipids
-proteins
Pancreatic duct (enzymes, buffers) and common bile duct (bile) empty into ______ ______ - chemical digestion of food stuffs
duodenal ampulla
Segmentation:
chyme moved back/forth few cm at a time by alternating contraction & relaxation of rings of smooth muscle. This mixes the chyme with bile, pancreatic, and intestinal juices
The Small Intestine ABSORPTION
Where does 90% of absorption occur?
small intestine
Structural Modifications of Small Intestine to Increase Surface Area for ABSORPTION
Plicae circulares: deep circular folds
Villi:
Microvolli:
increase surface area for absorption
fingerlike extensions of the mucosa
tiny projections of absorptive mucosal cells’ plasma membranes
What enzymes are embedded in microvilli?
What do they do?
brush border enzymes
finish the digestion of CHO and proteins in the small intestine
What happens in the duodenum?
Jejunum?
Illeum?
chemical digestion
Nutrient absorption
Vitamin absorption
Where does nutrient absorption occur in the small intestine?
Jejunum
Most digestion happens in what part of the small intestine
duodenum
Large intestine moves what to the anus for defecation?
fecal material
Large intestine has what important function?
reabsorption of water
How much absorption happens in the large intestine?
<10%
