1. Digestion and Excretion
Chapter 15

2. Lesson 1: Nutrition

3. Food provides your body with energy and nutrients it needs to survive
Every activity you do requires energy, even sleeping
Digestive system processes food and releases energy that is used for cellular processes and all activities you do
Why do you eat?

4. eNERGY The amount of energy in food is measured calories
A Calorie (Cal) is the amount of energy it takes to raise the temperature of 1kg of water by 1°C
Each food contains a different amount of energy
For example:
Grape = 2 Cal
Slice of cheese pizza = 220 Cal
The amount of energy a person requires depends on the person (weight, gender, activity level)
eNERGY

5. Nutrients Food is made of nutrients
Nutrients are substances that provide energy and materials for cell development, growth, and repair
Groups of Nutrients:
Proteins – Build and repair tissue
Carbohydrates – Major source of energy
Fats – Stored energy
Vitamins – regulation of body functions
Minerals – help body regulate many chemical reactions
Nutrients

6. Lesson 2

7. Types of digestion Mechanical digestion: Chemical digestion:
Food is physically broken down into smaller pieces (chewing, mashing and grinding food)
Chemical digestion:
Chemical reactions break down pieces of food into smaller molecules
Chemical digestion cannot occur without the help of enzymes
Types of digestion

8. Enzymes:
Proteins that help break down larger molecules into smaller molecules.
Enzymes speed up, or catalyze the rate of chemical reactions
Without enzymes, some chemical reactions would be too slow or would occur at all
enzymes

9. Many molecules are too big for your body to use, they must be broken down.
The digestive system produces enzymes that are specialized to help break down each type of food molecule
The enzyme doesn’t break apart just the food particle.
The enzyme is ready for use immediately
The role of enzymes

10. Organs of the digestive system
In order for your body to use nutrients in the food you eat, nutrients must pass through digestive system
Digestive system has 2 parts:
Digestive tract
Other organs that help the body break down and absorb food
Other organs include the tongue, salivary glands, liver, gallbladder, and pancreas
Organs of the digestive system

11. Mouth Digestion begins in your mouth
Teeth and tongue mechanically digest food by chewing
Salivary glands produce saliva
Saliva contains an enzyme that helps break down carbohydrates
Mouth

12. Esophagus After swallowing, food enters your esophagus
Esophagus is a muscular tube that connects the mouth to the stomach.
Food moves through the esophagus by waves of contractions called peristalsis
Partially digested food is pushed down the esophagus into the stomach
Esophagus

13. stomach

14. Stomach The stomach is a large hollow organ
2 functions of the stomach:
Temporarily store food – can expand like a balloon
Chemical digestion:
Walls of the stomach are folded
The cells in these folds produce chemicals that help break down proteins
Contains “Gastric Juice” which makes stomach acid and contains pepsin, an enzyme that helps break down proteins into amino acids.
As food mixes with gastric juice in the stomach, it forms a thin, watery liquid called Chyme
Stomach

15. Small intestine

16. Small intestine Most chemical digestion occurs in the small intestine
The small intestine is a long tube connected to the stomach
This is where chemical digestion and nutrient absorption occur
Like the stomach, the walls of the small intestine are folded
The folds of the small intestine are covered with fingerlike projections called villi
Each Villus contains small blood vessels
Nutrients in the small intestine diffuse into the blood through these blood vessels.
Small intestine

17. Parts of food that are not absorbed in the small intestine move by peristalsis into the large intestine, also called the colon
Large intestine bigger in diameter than small intestine but much shorter
Water absorbed in the large intestine
Materials that pass through large intestine are waste products of digestion
Waste products become more solid as excess water is absorbed
Peristalsis continues to force the remaining semisolid waste material into the last section of the large intestine, called the rectum.
Muscles in the rectum and anus control the release of this semisolid waste, called feces
Large intestine

18. Large intestine

19. Bacteria and digestion
Not all bacteria are harmful
Some bacteria have an important role in the digestive system
Some digest food and produce important vitamins and amino acids
Bacteria in the intestines are essential for proper digestion
Bacteria and digestion

20. Digestive system and Homeostasis
Nutrients from food are absorbed in the small intestine
Digestive system must function properly for absorption to occur
These nutrients are necessary for other body systems to maintain homeostasis
Example:
The blood in the circulatory system absorbs the products of digestion
Blood carries the nutrients to all other body systems, providing them with energy
Digestive system and Homeostasis

21. Lesson 3: The Excretory system

22. Function of the excretory system
Collects and eliminates wastes from the body
Regulates the level of fluids in the body
Function of the excretory system

23. Collection and elimination
Your body collects wastes:
The digestive system collects waste products in the intestines
The circulatory system collects waste products from the blood
If waste is not removed or eliminated from your body it could become toxic and damage your organs.
Collection and elimination

24. Regulation of liquids Water is an essential nutrient for your body
Some water is lost when waste is eliminated
Excretory system controls how much water leaves the body
This ensures that neither too little nor too much water is lost
Regulation of liquids

25. Digestive system collects and removes undigested solids from foods you eat
Urinary system processes, transports, collects, and removes liquid waste from the body
The respiratory system removes carbon dioxide and water vapor from the body
The integumentary system, secretes salt and water through the sweat glands
Types of excretion

26. Organs of Urinary system
Kidneys
Bean shaped organ that filters, or removes, wastes from blood
Contain blood vessels and Nephrons
Nephrons are networks of capillaries and small tubes where filtration of blood occurs.
When blood is filtered, a fluid called urine is produced
Organs of Urinary system

27. Nephrons Kidney is made up of about 1 million nephrons
Nephrons filter the blood twice
Your entire blood supply is filtered by the kidneys about 60 times each day
Nephrons

28. Ureters, bladder and urethra
Urine cannot stay in the kidney
It leaves each kidney through a tube called a ureter
Both ureters drain into the bladder
Bladder holds urine until it is excreted
Urine leaves the bladder after it is full through a tube called the urethra
Ureters, bladder and urethra

29. Excretory system and homeostasis
Excretory system filters wastes from the blood
If wastes were able to build up they would become toxic
Also, removal of wastes from the digestive system maintains homeostasis
Excretory system and homeostasis