A system (including the thymus and bone marrow and lymphoid tissues) that protects the body from foreign substances and pathogenic organisms by producing the immune response.A system that provides a defense mechanism to organism, providing defensive measures against antigens which would prove harmful to the organism.
Ultrasound is a type of imaging. It uses high-frequency sound waves to look at organs and structures inside the body. Health care professionals use it to view the heart, blood vessels, kidneys, liver, and other organs. During pregnancy, doctors use ultrasound to view the fetus. Unlike x-rays, ultrasound does not expose you to radiation. During an ultrasound test, you lie on a table. A special technician or doctor moves a device called a transducer over part of your body. The transducer sends out sound waves, which bounce off the tissues inside your body.
Definition of ultrasound for English Language Learners. : 1  a type of sound that is too high for humans to hear. 2  medical : a method of producing images of the inside of the body by using a machine that produces sound waves which are too high to be heard. : 3  an image that is made using ultrasound.