9 Health - 'The Digestive System'

pgs. 82-90

What is digestion?

The process by which the body breaks down food into small molecules that it can use.

Where does the process of digestion take place?

In the gut or alimentary canal.

What is the alimentary canal?

A continuous tube that is about 9 meters long, extending from the mouth to the anus, through which food passes during digestion.

What is ingestion?

The intake of food into the body through the mouth.

What is mechanical digestion?

The process by which food is broken down physically.

What is the bolus?

A ball-like mass of moistened food is rolled into by the tongue before it is swallowed.

What is chemical digestion?

The process by which food is broken down by enzymes.

What does the epiglottis do?

This covers the opening of the windpipe, preventing food from entering the lungs.

What is the esophagus?

The tube that connects the mouth and stomach.

What is the esophagus made of?

Smooth muscles that contract and relax, allowing the bolus to pass from the mouth into the stomach.

What is peristalsis?

A series of wave-like muscle contractions that move food along the digestive tract.

What is the stomach?

A small muscular sac that stores and digests food. This secretes digestive juices that contain enzymes and hydrochloric acid that help to break down protein in food and kill bacteria.

What is chyme?

A semi-fluid mass of undigested food that is produced by the stomach after the food is mixed with digestive juices.

Where does digestion end?

The small intestine.

What is the small intestine?

A coiled tube approximately 5-6 meters long.

What is absorption?

The process by which nutrients from food is taken into the bloodstream.

What are villi?

Tiny finger-like projections of tissue in the small intestine that increase surface area and contain specialized cells that transport substances into the bloodstream.

What is assimilation?

The process by which digested food molecules are absorbed and transported by the blood to body tissues and enter the cells.

What happens in the large intestine?

Here, water is absorbed into the blood from undigested food, producing feces. Feces are stored in the rectum. Eventually the feces will pass out of the body through the anus.

What is egestion?

The passing of undigested food or feces through the anus.

What are accessory organs?

The organs of the digestive system that are found outside of the alimentary canal.

What are the accessory organs of the digestive system?

• Salivary glands

• Pancreas

• Gallbladder

• Liver

What are salivary glands?

Exocrine glands that are found in and around the mouth and throat that produce saliva.

What is saliva used for?

Used for lubricating the mouth, moistening food, and aiding in swallowing.

What does the pancreas produce?

This produces pancreatic juice, a digestive juice containing enzymes.

What is the gallbladder?

A small organ found beneath the liver that stores bile.

What is the liver?

The largest internal organ found below the diaphragm in the abdominal cavity that is dark red or brown in color.

What are the functions of the liver?

• Produces bile

• Produces blood protein that helps with clotting

• Stores vitamins A, D, B and mineral iron

• Stores excess glucose as glycogen

• Breaks down harmful substances like alcohol

• Produces urea

What is bile?

A greenish-yellow secretion which breaks down or emulsifies fat.

What is urea?

A toxic substance made when protein is broken down.

What are enzymes?

Proteins that speed up the rate of chemical reactions in the body.

What is a catalyst?

Any substance that increases the rate of a chemical reaction.

What is a biological catalyst?

An enzyme that accelerates chemical reactions in living organisms.

How do enzymes work?

These work by using a lock and key method on substances called substrates. The substrate must fit exactly into an enzyme’s active site that allows the substrate to bind into it for a reaction to take place, making new products.

What are the types of enzymes?

Breakers and builders.

What is a breaker enzyme?

Enzymes that break down large molecules into smaller molecules that the body can use.

What is a builder enzyme?

Enzymes that join small molecules together to make one large molecule.

What are the five properties of enzymes?

• These are proteins

• These are reusable

• These are specific

• These are affected by temperature

• These are affected by pH

Enzymes are reusable

Because enzymes are not changed during a reaction, they can be used again.

Enzymes are specific

Only one type of enzyme can act on one type of substrate.

Enzymes are affected by temperature

Enzymes work best at body temperature. If it gets too cold or too hot, the enzyme will become denatured or deformed and not work properly.

Enzymes are affected by pH

Most enzymes work best at a neutral pH of 7. However, some enzymes prefer acidic or alkaline conditions.