14.1 and 16.1

14.1 and 16.1

Blood Pressure

The Heart

Blood exerts a force, called blood pressure, against the walls of blood vessels. Blood pressure is caused by the force with which the ventricles contract. In general, as blood moves away from the heart, blood pressure decreases. This change happens because the farther away from the ventricle the blood moves, the lower its force is. Blood flowing near the heart arteries exerts the highest pressure. Blood pressure in arteries farther from the heart is much lower. Blood pressure can be measured with an instrument called a sphygmomanometer. A cuff is wrapped around the upper arm. Air is pumped into the cuff until the blood flow through the artery is stopped. As the pressure is released, the examiner listens to the pulse. Blood pressure is expressed in millimeters of mercury.

Each time the heart beats, it pushes blood through the blood vessels of the cardiovascular system. Your heart is about the size of your fist. In a year, your heart pumps enough blood to fill 30 competition-size swimming pools. The right side of the heart is completely separated from the left side by a wall of tissue called the septum. Each side has two compartments, or chambers called ventricles—an upper chamber and a lower chamber.

The Cardiovascular System

The cardiovascular system takes required substances, like blood, to organs, and takes waste products away from cells. Also, blood contains white blood cells that help fight diseases.

Capillaries

Arteries

Veins

After blood moves through capillaries, it goes into larger blood vessels called veins. They carry blood back to the heart. The walls of veins, like those of arteries, have three layers, with muscle in the middle layer. However, the walls of veins are generally much thinner than those of arteries.

Eventually, blood flows from small arteries into the tiny capillaries. In the capillaries, materials are exchanged between the blood and the body’s cells. Capillary walls are only one cell thick so materials can pass easily through them. Materials such as oxygen and glucose pass from the blood, through the capillary walls, to the cells. Cellular waste products travel in the opposite direction—from cells, through the capillary walls, and into the blood.

Blood travels through arteries after it leaves the heart. The walls of arteries are very thick. There are 3 cell layers. The inner layer is made up of epithelial cells and is smooth. This smooth surface lets blood flow freely. The middle layer consists mostly of muscle tissue. The outer wall is made of flexible connective tissue. Because of this layered structure, arteries have both strength and flexibility. Arteries are able to withstand the enormous pressure of blood as it is pumped by the heart and to expand and relax between heart beats.

Two Loops

The first loop:

blood travels from the heart to the lungs and then back to the heart

The second loop:

blood is pumped from the heart throughout the body and then returns again to the heart

Cells and Tissues

16.1 The Body's Transport System

You already know a lot about cells, so let's move on to tissues.

A tissue is a group of similar cells that perform the same function. The human body contains four basic types of tissue:

• muscle tissue
• nervous tissue
• connective tissue
• epithelial tissue.

The body's transport system includes the following:

• the Cardiovascular System
• the Heart
• Two Loops
• Arteries
• Capillaries
• Veins
• Blood Pressure

14.1 Body Organization

1. What are the 4 levels of organization in the body?

2. What is homeostasis?

3. Name at least 3 of the parts in the body's transport system mentioned in this presentation.

4. What instrument is used to measure blood pressure?

5. What is the main difference in the functions of the first and second loops?

The levels of organization in the human body from smallest to largest are:

• cells
• tissues
• organs
• organ systems

Homeostasis

This is the process in which an organism’s internal environment is kept stable despite changes in the outer environment.

example: It's really cold outside, but your body temperature doesn't drop with the temperature outside.

Organs and Organ Systems

An organ is a structure that is composed of different types of tissues. Like a tissue, an organ performs a specific job. The job of an organ is usually more complex than that of a tissue. Some examples are:

• stomach
• heart
• brain
• lungs