LESSON 1TRANSPORT AND DEFENSE

Chapter 7

Body’s Organization

Groups of organs work together in an Organ system

The organs systems work together to maintain homeostasis

Homeostasis- maintaining constant internal conditions when external conditions change

Digestion

The body needs nutrients and substances from food

Digestion is the process that breaks down food into small molecules so they can be absorbed and moved into the blood. Two types of Digestion Mechanical Chemical

Mechanical Digestion

Food is chewed, churned, mixed, grinded etc.Major organs that use mechanical digestion

are the teeth, mouth, and stomach

Chemical digestion

Chemical reactions occur that break down large molecules of food into smaller molecules

There are several enzymes that help digestionAn enzyme is a special protein that speeds up

a chemical reaction but does not get used up or changed in the reaction

Ex- amylase in saliva

Organs of Digestion

Digestive TractMouthEsophagusStomachSmall intestineLarge intestineRectumAnus

Accessory organsTongueTeethSalivary glandsLiverGall bladderPancreas

Mouth

Both mechanical and chemical digestionFood is chewed, grinded, and made into smaller

pieces with the help of the tongue (mechanical)Saliva mixes with the food to moisten it and to start

the breakdown of carbohydrates (amylase and chemical)

Saliva is produced by three sets ofglands

Esophagus

The tongue has pushed the food into the back of the mouth

The epiglottis covers the trachea or windpipe so food does not pass into the lungs.

The esophagus is a muscular tube that pushes the food into the stomach by wave like contractions called peristalsis

Mucus lines the esophagus to keep the food moist

No Digestion

Stomach

Both Mechanical and chemical digestionMuscular bag that churns and mixes the food

(mechanical)Mixed with enzymes and hydrochloric acidHydrochloric acid works with an enzyme,

pepsin, to break down proteinsThe acid also kills bacteriaStomach also produces mucus which protects

the stomach from the acid and makes the food slippery

Chyme

Thin, watery liquid mixture of food, acid, and enzymes

Small intestine

Only chemical digestionAbout 30 feet in lengthSmall diameter compared to the large

intestineMost digestion occurs in the upper portion

called the duodenum.Greenish chemical, bile from the liver, is

mixed hereBile emulsifies fatSodium bicarbonate ( baking soda) is added

to neutralize the stomach acid

Small intestine

The pancreas makes the sodium bicarbonate and also produces insulin important in the regulation of the amount of glucose in your body

Absorption of nutrients occurs hereVilli- small finger- like projections increase

the surface area for absorption of nutrients

Large intestine

It is important for the absorption of waterPeristalsis slows down so water can be

absorbedThe material becomes more solid and

remains here until it is released from rectum and anus

Accessory organs

Teeth- chewingTongue- moving food to the back of the throatSalivary glands- produce salivaLiver- produces bileGall bladder- storage for bile until neededPancreas- makes enzymes, sodium

bicarbonate, and insulin for glucose regulation