1. Digestive System
And Excretory System

2. Diagram

3. 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

4. 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)

5. 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

6. The stomach

7. 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.

8. Small intestine
Between 6-10 m long in an adult

9. 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

10. The large intestine

11. 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.