Transcript Digestive System

Digestive System
And Excretory System
Diagram
The role and the fate of a
meal
• The purpose of the digestive system is to
chemical and mechanically break down food
to produce nutrient molecules that our cells
can absorb
• When we eat, digestion begins in the mouth.
Saliva (amylase enzyme) begins the
digestion process and our teeth and mouth
create a mass of crushed up food called a
bolus
• The food passes through the esophagus (a
muscular tube that pushes the food down to
the stomach
Gastric juices
• Gastric juices are secreted by the epithelial
tissues in the stomach. They are very acidic
including hydrochloric acid. These fluids
surround the food and help to break it down
further. The stomach needs to be acidic
because an important enzyme for breaking
down protein (pepsin) needs an acidic
environment to function
• The stomach wall also secretes mucus to
protect the lining. Acid reflux is when acid
splashes up the esophagus which lacks the
mucus protection. Also ulcers are areas in the
stomach where the acid is creating sores
(holes)
The stomach
• Nerves in the stomach wall receive a
signal when food enters which starts the
churning action of the muscles of the
stomach wall. There are groves and
ridges in the stomach to allow for
enhanced mechanical breakdown of
food. When the food leaves the
stomach it is in liquid form
The stomach
The Small Intestine
• The bottom of the stomach has a sphincter an
opening with a muscle around it. When the
muscle relaxes processed food can enter the
intestine. The first meter is the
duodenum=where most digestion takes
place.
• The chemical breakdown of food is
completed here with the aid of extra digestive
enzymes released through ducts connecting
the pancreas, gall bladder and liver.
• The intestine is covered in tiny folds called
villi or microvilli. These increase the surface
area allowing for extra absorption.
Small intestine
• Between 6-10 m long in an adult
The Large Intestine
• Colon, rectum and anus
• In humans it has a large diameter and shorter
length
• Main function is to absorb water back into the
body as well as vitamins and salt. And to
release wastes
• Most material in cell walls of plants cannot be
digested and is released as waste after going
through our digestive system
• Here are bacteria as well helping in digestion
and releasing nutrients such as vitamin K
The large intestine
Excretory System
• Liquid waste is filtered through the
kidneys by traveling in the blood. Extra
liquid is released as urine with
unneeded salt included. The urine is
stored until the bladder is full.