Chapter 18: Digestive system

what is the digestive system also called?

the gastrointestinal system

what does the word "gastro" refer to?

the stomach

what is the overall function of the digestive systm?

To process food into molecular form in order for the circulatory system distributes among the cells in the body.

what is 'motility'

the general movement of food within the digestive tract
(ex. mastication, deglutition and contraction of smooth muscle)

what does digestion refer to?

the chemical AND mechanical breakdown to smaller and smaller pieces for absorption

[chemical = enzymes, mechanical = mastication]

what dies 'secretion' refer to?

the release of exocrine and endocrine secretions into the lumen of GI tract for digestion
[think bile, hormones, enzymes... to help aid digestion]

define 'lumen'

the hollow interior of an autonomical structure

what is 'absorption'

the movment of digested end products into the blood and lymph

what does 'storage and elimination' refer to?

temporary storage following by elimination of indigestible food molecules
(waste like urine feces n sweat)
[ex. fiber, additives in food = indigestible ]

what is the 'immune barrier' and give me an example.

Physical barrier to pathogens and toxins due to tight junctions in the epithelial lining of the intestine

[ex. GI mucosa (aka mucous membrane) has 80% of total immune system cells in the body]

digestion of food molecules occur through what type of reaction?

digestion occurs by hydrolysis reactions

[hydrolysis reaction = chemical breakdown involving reaction with water]

where does the most digestion happen?

in the small intestine

what structures are in the gastrointestinal (GI) tract?

(or in other words, where does the food pass through?)

mouth ,pharynx , esophagus, stomach, small intestine, large intestine

what is the GI tract also known as?

the Alimentary canal

What are the accessory organs/tissues in the digestive system?

teeth, tongue, salivary glands, liver, gallbladder and pancreas

why are the accessory organs called accessory organs?

because the food/chyme doesn't pass though these structures, but they help digestion

[ex.. gallbladder = food doesn’t pass through here but it will secrete bile to help digest food]

where does most absorption of nutrients occur and what does this tell you?

most absorption occurs in the Small Intestine
... this tells you that most digestion happens before or inside the small intestine

name the four layers/tunics of the gut wall
(innermost to outermost pls :)

Mucosa, submucosa, muscularis externa, serosa)

(think... MSMS

what is the mucosa and what are it's functions?

it is the innermost layer
functions: absorption, section and mucus secretion

when referring to mucus in the digestive system, what is its main function?

protects gut wall from digesting itself!!

[think whenever you see mucus, always think protection]

what are the two layers in the mucosa?

lamina propria and muscularis mucosae

what is the muscularis mucosae and what does it do?

it is the smooth muscle layer in the mucosa and has lots of folds
-the folds help increase surface area for better absorption
-the smooth muscle layer helps produce movement to move the chyme

what does the submucosa contain and what does it help do?

it is the 2nd most inner-layer

contains blood/lymph vessels and the submucosal plexus ( plexus=a collection of neurons). These neurons help control the smooth muscle in the mucosa

what is the muscularis externa and what does it do

it is the 2nd OUTERmost later
helps segmental and peristaltic contraction of the muscles to move food throughout the tract. This also mixes it with digestive enzymes

what are the two layers of the muscularis externa?

inner circular layer and the outer longitudinal layer
(both made with smooth muscle)

what is the serosa and explain it's structure.

-Sersoa is the outermost layer of the gut wall
-it is made with connective tissue and cover with epithelium

define mastication

chewing of food in mouth

even though mastication is a mechanical process, how does it help with chemical digestion?

chewing mixes the food with saliva. Inside the saliva are salivary amylase (an enzyme)

salivary amylase is secreted by what?

salivary glands

what does salivary amylase help digest? is it full digestion or partial?

it partially digest starch (a carbohydrate)

where does digestion of carbs start and by what enzyme?

in the mouth by salivary amylase

define deglutition and what does it refer to?

Deglutition is swallowing and it refers to when food/drink stimulate receptors in the pharynx with pressure, thus telling the brain to swallow

define bolus

food that is mixed with saliva and is ready to be swallowed

t/f the upper esophageal sphincter needs to contract in order to swallow.

false, the sphincter needs to relax in order to let the food in the esophagus

what is the main function of the esophagus?

Motility, it transports the bolas from the mouth the to stomach.

t/f absolutely no digestion occurs in the esophagus

true

[remember, its main function is motility]

define peristalsis and name the two types of muscles it uses.

the wavelike muscular contractions that push the bolus down the esophagus to the stomach.

uses circular smooth muscle and longitudinal muscle

how do circular and longitudinal work together to transport the bolus?

the circular muscle contracts above the bolas and relaxes below it while the longitudinal muscle shortens and lengthens to move it down.

(refer to picture

t/f the most digestion occurs in the stomach

FALSE,
the most happens in the small intestine

Stomach turns the bolus into ____

chyme

[chyme = chewed food w/ gastric juice]

after the stomach, where does the chyme go?

to the small intestine

what are the main functions of the stomach?

-stores food (moves chyme slooooowly)
-kills bacteria w/ acidity of gastric juice
-starts digestion of proteins

what do proteins digest into?

amino acids, the building blocks of proteins

[think... you have to eat protein in order to gain muscle (aka protein) ]

where does carb digestion start?

in the mouth (with salivary amylase)

what are special about the cells in the stomach?

they synthesize and secrete...
-mucus
-enzyme precursors (enzymes that are in an inactive state)
-hydrochloric acid (HCl) (aka. stomach acid)
-hormones

what are the folds in the side of the stomach called and what are they used for?

gastic rugae are used for gastic motility

what type of glands are found in the stomach?

Gastric glands

[remember.. gastric refers to the stomach]

Cells of the gastic glands in stomach

refer to my "cells of gastric glands in stomach" knowt or the matching game.

(pls this part is important)

how does bicarbonate effect the stomach?

bicarbonate protects the stomach from acid damage

where can you find the small intestine?

in between the stomach and large intestine

What are the two main functions of the small intestine?

digestion and absorption

what organic molecules does the small intestine digest?

carbohydrate, lipids, proteins

After molecules are absorbed into the small intestine, where do they go?

into the blood stream to be transported to other cells that need nutrients

t/f the small intestine ABSORBS proteins

false, they absorb amino acids because protein molecules are too big

what are the folds in the mucosa called?

villi

the folds on the villi called what?

micovilli (or brush border)

what is the function of the villi/microvilli?

to increase surface area for more efficient absorption

what is embedded into the microvilli?

brush boarder enzymes to help digestion

t/f all digestion must be finished in the small intestine

true

t/f digestion in the small intestine is fast

false, it is slow to ensure proper absorption of all nutrients in chyme

what is the main contraction in the smooth muscle of the small intestine?

segmentation... contraction of the small intestine in different segments but occurring simultaneously

( like a wave ~~~~~)

how does segmentation help digestion and how is it controlled?

-helps by mixing and moving chyme
-controlled by autonomic nervous system in the gut wall (not voluntary)

t/f some digestion happens in the large intesine

false, no digestion occurs here

what is the large intestine also called?

the colon

t/f the large intestine has villi

false,
(villi is used for digestion and no digestion happens here)

instead of villi, the large intestine has _____

Haustra... pouches on the outer surface

( looks like --u-- instead of __n__)

what are the main functions of the colon?

-absorption of electrolytes, water and vitamins
-excretion of waste in the form of feces

what does the liver produce?

bile

how are the liver and gallbladder connected?

the liver produces bile and the gallbladder stores the bile

what is the function of the pancreas?

synthesizes pancreatic juice for digestion
(ex. Pancreatic lipase)

what are the main functions of the liver?

-detoxifies blood
-carbohydrate metabolism
-lipid metabolism
-protein synthesis
- secretes bile
-stores carbs and lipids

t/f the liver has a lumen

false, has tight junctions and is highly vascular

What are hepatocytes and what happens in them?

hepatocytes are liver cells
-all functions of the liver happen inside the hepatocytes

explain the tract of bile

-bile is produced by hepatocytes --> secreted into bile canaliculi --> canaliculi empties into bile ductules --> ductules empties into gallbladder where it is stored

what is the portal triad explain each one

three tight knit vessels within the liver
- Hepatic artery: where blood enters liver
-Bile canaliculi: brings bile to ductule
-Bile ductule: brings bile to gallbladder

in what structure in the liver does the blood leav?

central vein

what is the most important component of bile?

(pertaining to our class, not the actual most important)

bile salts

what are bile salts and what do they do?

-cholesterol based salts that help emulsify fat for lipid digestion

[has cholesterol bc like dissolves like]

t/f micelles are amphipathic

true, this helps with the breakdown/emulsification of fat

[amphipathic = has both nonpolar and polar sides]

explain emulsification

breakdown of large fat globules by bile salts into smaller globules to help further digestion.


[further digestion is done by lipase enzymes]

through what structure does bile enter the small intestine?

via the common bile duct.

[remember... liver makes bile, gallbladder stores it, small intestine uses it]

the pancreases has endocrine and exocrine functions, name them within their categories.

endocrine functions: synthesizes insulin and glucagon\
exocrine function: synthesizes pancreatic juice

What components make up pancreatic juice?

bicarbonate, ~20 enzymes and water

what are the three enzymes you should know within pancreatic juice and are they active within the pancreases?

amylase, trypsin, lipase
no, they are only activated in the small intestine

why are digestive enzymes only active within the small intestine?

ex. if enzymes were active inside the pancreases, they would digest the pancreases. Enzymes should only be active in the small intestine because it has a mucus layer to protect it from being digested.

what does amylase do?

digests starch

what does trypsin do?

digest protein

what two types of enzymes help accomplish complete digestion in the small intestine?

pancreatic enzymes and bush boarder enzymes help aid digestion in the SI

what are the three main enzymes that help with carb digestion?

Salivary amylase, pancreatic amylase and brush boarder enzymes

where does carb digestion start and where is it mostly completed?

starts in the mouth by salivary amylase and is mostly completed in the Small intestine by the pancreatic amylase

how does amylase help digestion? (more specifically pancreatic amylase)

amylase breaks down big carb molecules into smaller ones for easier absorption.

once small enough, carbs are actively transported into the blood stream

what enzymes help digest proteins?

pepsin, trypsin and brush border enzymes

where does protein digestion start?

it starts within the stomach with pepsin

explain how protein is digested, how does it enter the blood stream

protein is broken down into smaller molecules, amino acids --> then amino enter the epitheial layer of the small intestine through active transport --> then are finally secreted into the ISF to be absorbed into the capillaries.

lipids in chime stimulate what?

Secretion of bile, thus resulting in emulsification of fats

what enzymes digest lipids and what do the lipids turn into?

pancreatic lipase helps lipids turn into fatty acids and monoglycerides

explain the steps of lipid digestion

1. lipids in chyme stimulate secretion of bile into SI
2.bile breaks down lipids into smaller fats (by bile salts)
3. Lipase further breaks down lips into fatty acids and monoglycerides and enter the epithelial cell
4. once in epithelial cell, fatty acid and monoglycerides combine to become trigylcerides
5. tryglycerides combine with cholesterol and protein to form chylomicrons that enter lymphatic vessels (eventually entering blood)