Week 11 - Healthy Human Body Systems

Lesson 10

Science in Action 8
Pages 135-140

ScienceFocus 8
Pages 146-147

Every circulation system needs a pump to circulate materials around. Our heart is a four chambered pump. If you look at the diagram of the heart in your text you will find that part is red and the other part is blue. Do you know what that means? When blood carries fresh oxygen from the lungs it is quite a bright red so the diagrams show the oxygen rich blood flow in and away from the heart as bright red. This blood flows out to all the cells in your body. The blood arriving back at the heart that is low in oxygen is more purplish in colour and is indicated by the blue part of the diagram.

Click on the above image to learn about your heart

	Blood Pressure Blood pressure can be defined as the measure of the pressure in the circulatory system. There are two pressure levels; the pressure in the system when your heart is beating - the systolic pressure, and the pressure when your heart is momentarily at rest - your diastolic pressure.
As we get older the pressure tend to climb higher. This can be dangerous as it can lead to heart disease and strokes. It is important to remain active, eat a balanced diet and try not to gain weight as we get older as these are the major variables that can affect blood pressure. The sphygmomanometer, otherwise know as a blood pressure cuff is displayed at the right.

Lesson 11

Science in Action 8
Pages 126-130

ScienceFocus 8
Pages 149-150

Like all living organisms we need energy to carry on our day to day activities. At peak times of activity, like these women playing rugby, large amounts of energy are needed by our cells over a short period of time. So it is important that we eat a well balanced diet that includes proteins, carbohydrates and lipids. But the food we eat is much too large to be useful to our cells. The purpose of the digestive system is to break down the food we eat into smaller pieces that can be carried by the circulation system and used by our cells.

Try This! Find a cracker and scrap off all the salt. If its an unsalted cracker all the better. Chew the cracker but do not swallow it. After one minute how does it taste? After five minutes how does it taste? What do you think happened to the cracker as you chewed it over the five-minute period?

Examine the diagram below. By the end of this lesson you should be able to identify the major parts of the digestive system.

Both your trachea and your esophagus begin at the back of your throat. Swallowing food into your trachea would not be a good idea. Why? (Think back to the lesson on respiration.) There is a small flap of skin, called the epiglottis , which closes over the trachea as you swallow.

The food is then directed to the esophagus. What do you think causes the food to move down into the stomach? Perhaps its by the force of gravity. But astronauts live in the gravity free environment on the space shuttle and they can still eat, so it must be something else. Your digestive system uses the muscles along the digestive pathway to push the food along in waves. This pushing action is called peristalsis .

Both chemical and mechanical digestion occur in the stomach . While muscles squeeze and churn the food, enzymes and acid are added. This combination of actions causes the food to turn to the consistency of a milkshake. But if you have ever gotten sick to your stomach, you know that it neither looks nor tastes like a milkshake! The strong acid breaks down proteins like meats and milk products.

But the stomach is made of proteins! How does it keep from being eaten away? Hmmmm, what did you learn about the stomach in the movie that prevented this problem?

After 2 to 3 hours this ground-up food now enters the small intestine . Immediately, it is mixed with enzymes from the pancreas and gallbladder and any fats that you ate are further broken down.

The inside of the small intestine is covered with very small finger-like projections called villi . These villi increase the surface area for absorbing food. By the time the food particles reach the villi in the small intestine they are small enough to be able to be absorbed through the thin walls of the villi and into the blood stream. This process is called absorption should sound familiar, as it is very similar to gas exchange in the lungs.

Any food particles that aren't absorbed in the small intestine are passed along to the large intestine . Here, any remaining water, minerals and vitamins are absorbed and the remaining material compacted and stored in the rectum as feces until you go to the bathroom.

Exercise 3.3: The Digestive System