Transcript Digestive System - Mercer Island School District

Digestive System
Alicia C, Binali, Cole, and Tom
Main Function of the Digestive System
The function of the digestive system is
digestion and absorption. Digestion is
the breakdown of food into small
molecules, which are then absorbed
into the body. The digestive system is
divided into two major parts: The
digestive track is a continuous tube
with two openings: the mouth and the
anus.
Main Organs and
their Functions
Mouth
The teeth chew up food and break the food into pieces. Saliva in the mouth assists
in breaking down the food.Chewing breaks the food into pieces that are more
easily digested, while saliva mixes with food to begin the process of breaking it
down into a form your body can absorb and use.
Esophagus
The esophagus is a muscular tube extending from the pharynx (throat) to the
stomach. By peristalsis, a series of contractions, the esophagus delivers food to the
stomach. The lower esophageal sphincter prevents food from passing backwards
into the esophagus.
Stomach
The stomach holds the food while it secretes acid and powerful enzymes that
continue the process of breaking down the food. When it leaves the stomach, food
is the consistency of a liquid or paste. From there the food moves to the small
intestine.
Liver
The liver has multiple functions, but its main
function within the digestive system is to process
the nutrients absorbed from the small intestine.
Bile from the liver secreted into the small intestine
also plays an important role in digesting fat. In
addition, the liver is the body’s chemical "factory."
It takes the raw materials absorbed by the
intestine and makes all the various chemicals the
body needs to function. The liver also detoxifies
potentially harmful chemicals. It breaks down and
secretes many drugs.
Small Intestine
There are three segments of the small intestine, the duodenum, jejunum, and ileum.
The small intestine uses enzymes released by the pancreas and bile from the liver.
Bile is a compound that aids in the digestion of fat and eliminates waste products
from the blood. Peristalsis moves food through and combines it with digestive
secretions. The duodenum is largely responsible for continuing the process of
breaking down food, with the jejunum and ileum being mainly responsible for the
absorption of nutrients into the bloodstream.
Large Intestine (Colon)
Stool, or waste left over from the digestive process, is passed through the colon.
First in a liquid state and ultimately in solid form as the water is removed from the
stool. A stool is stored in the sigmoid colon until a "mass movement" empties it into
the rectum. The stool is mostly food debris and bacteria. These bacteria synthesize
vitamins, process waste products and food, and protect against bacteria. When the
descending colon becomes full, it empties its contents into the rectum to begin the
process of elimination.
Rectum
The rectum connects the colon to the anus. It receives stools from the colon, to
hold the stool until evacuation happens. When anything enters the rectum, sensors
send a message to the brain. The brain decides if the rectal contents can be
released. If they can, the sphincters (muscles) relax and the rectum contracts,
expelling its contents. If the contents cannot be expelled, the sphincters contract.
Anus
It consists of the pelvic floor muscles and the two anal sphincters. The lining of the
upper anus detects rectal contents. The pelvic floor muscle creates an angle that
stops stool from coming out when it is not supposed to. The anal sphincters provide
control of stool. The internal sphincter prevents us from going to the bathroom
when we are asleep, or unaware. When we get an urge to go to the bathroom, we
rely on our external sphincter to keep the stool in.
The Digestive System & Homeostasis
Review: Homeostasis is the balance the body maintains to continue to
function properly.
The digestive system breaks down food into a chemical form (simpler
molecules) that can be absorbed by the body. These molecules can be
used to fuel cellular activities and regulate body temperature.
The liver, which monitors the blood, is a very important organ of
homeostasis. The liver breaks down toxic substances like alcohol and other
drugs, and it produces urea, the end product of nitrogenous metabolism.
The liver produces the plasma proteins and stores glucose as glycogen
after eating. In between eating it releases glucose, thereby keeping the
blood glucose concentration constant. The liver destroys old blood cells
and breaks down hemoglobin--hemoglobin breakdown products are
excreted in bile.
Digestive System Interaction with Other
Systems
Cardiovascular System
Lymphatic System
Nutrients broken down from digested food
absorbs into the bloodstream. The bloodstream
carries the nutrients to all the other cells in the
body.
The lymphatic system is the absorbs fats and
fat-soluble vitamins from the digestive system
and transports these substances to the venous
circulation. Blood capillaries absorb most
nutrients, but the fats and fat-soluble vitamins
are absorbed by the lacteals.
Endocrine system
Excretory System
Sends chemical signals that control the speed of
digestion
While the digestive system collects and
removes undigested solids, the excretory
system filters compounds from the
bloodstream and collects them in urine.
Disorders and Diseases
1. Crohn’s Disease: A chronic disease that causes inflammation in the
gastrointestinal tract.
2. Celiac Disease: A disorder where the individual cannot tolerate gluten because
it harms the inner liner of the small intestine which prevents the absorption of
nutrients.
Pathway of food in the digestive tract
1) Mouth
2) Esophagus
3) Stomach
4) Small Intestine
5) Large Intestine (Colon)
Major Digestive Enzymes:
Function and Location
Salivary Amylase
Salivary Glands in the Mouth
Begins carbohydrate digestion by breaking down starch and
glycogen to disaccharides
Peptidase
Small Intestine
Breaks down peptides into amino acids
Intestinal Lipase
Small Intestine
Breaks down fats into fatty acids and glycerol
Enterokinase
Small Intestine
Converts trypsinogen into trypsin
Bile, also called gall
Liver
Sucrase, Maltase, Lactase
Released during digestion when fats enter the first part of the small
Small Intestine
intestine (duodenum). Bile emulsifies fats preparing them for further
Breaks down disaccharides into monosaccharides
digestion and absorption in the small intestine.
The Digestive System’s Interaction with
the Circulatory System
The digestive system works very closely with the circulatory system to get the
absorbed nutrients distributed through your body. The circulatory system also
carries chemical signals from your endocrine system that control the speed of
digestion.
Villi
Villi are small finger like objects that extends from the lining of the small intestine
walls. The villi increases the absorption of nutrient molecules that are passing
through the small intestine by creating more surface area for absorption. The
absorbed nutrients can then enter the bloodstream through diffusion and are
transported through the body to be used or stored.
Bibliography
http://www.biology4kids.com/files/systems_digestive.html
http://www.daviddarling.info/encyclopedia/L/lymphatic_system.html
http://faculty.southwest.tn.edu/rburkett/interactions_of_the_digestive_system.htm
http://www.webmd.com/heartburn-gerd/your-digestive-system
http://www.mhhe.com/biosci/genbio/maderbiology/supp/homeo.html
http://my.clevelandclinic.org/health/diseases_conditions/hic_The_Structure_and_Function_of_the_Digestive_System
http://www.theherbspecialist.com/6_5.html
http://sciencelearn.org.nz/Contexts/Digestion-Chemistry/Looking-Closer/Digestive-enzymes
http://www.niddk.nih.gov/health-information/health-topics/digestive-diseases/celiac-disease/Pages/facts.aspx
http://www.niddk.nih.gov/health-information/health-topics/digestive-diseases/crohns-disease/Pages/facts.aspx
http://livehealthy.chron.com/importance-villi-small-intestine-digestion-nutrients-3923.html
http://www.niddk.nih.gov/health-information/health-topics/Anatomy/your-digestive-system/Pages/anatomy.aspx
http://www.webmd.com/heartburn-gerd/your-digestive-system