Human Body Systems

Grade 5 · Science · Study Guide

Learn how the major organ systems of the human body work and how they depend on each other.

Your body is like a city — it has many systems running at once, each doing a specific job, but all working together so you can live and thrive. The major body systems include the skeletal, muscular, digestive, circulatory, respiratory, and nervous systems.

The skeletal system (206 bones in adults) provides structure and protects organs. The muscular system works with it to move your body. The digestive system breaks food into nutrients your cells can use. The circulatory system — powered by the heart — delivers oxygen and nutrients through blood vessels to every cell. The respiratory system brings oxygen in and pushes carbon dioxide out through the lungs.

The nervous system is the body's command center. Your brain sends signals along nerves to control everything from breathing to reading. These systems don't work in isolation. For example, when you exercise, your muscular system needs more oxygen, so the respiratory system breathes faster and the circulatory system pumps faster to keep up. Understanding how systems interact is the key to understanding how the whole body works.

Key terms

Organ System
A group of organs that work together to perform a major body function.
Circulatory System
The system made up of the heart, blood, and blood vessels that carries nutrients and oxygen throughout the body.
Respiratory System
The system including the lungs that brings oxygen into the body and removes carbon dioxide.
Nervous System
The brain, spinal cord, and nerves that send and receive signals to control body functions.
Digestive System
The system that breaks food down into nutrients the body can absorb and use.

Flashcards

Skeletal System
The 206 bones that give the body structure and protect organs.
Muscular System
The muscles that work with bones to allow movement.
Circulatory System
Heart, blood, and blood vessels that transport oxygen and nutrients.
Respiratory System
Lungs and airways that exchange oxygen and carbon dioxide.
Digestive System
Organs that break food into nutrients the body can use.
Nervous System
Brain, spinal cord, and nerves that control and coordinate the body.
Heart
The muscular organ that pumps blood throughout the body.
Lungs
The organs in the chest that take in oxygen and release carbon dioxide.

Questions

  1. Which organ is the main pump of the circulatory system?

    1. Lungs
    2. Brain
    3. Heart
    4. Liver
    Show answer

    Answer: Heart

    The heart is the pump of the circulatory system. It beats to push blood through arteries and veins throughout the body.

  2. The respiratory system is responsible for breaking down food into nutrients.

    Show answer

    Answer: False

    The respiratory system handles breathing — bringing in oxygen and removing carbon dioxide. The digestive system breaks down food.

  3. Which body system controls all other body systems by sending electrical signals?

    1. Muscular system
    2. Skeletal system
    3. Digestive system
    4. Nervous system
    Show answer

    Answer: Nervous system

    The nervous system (brain, spinal cord, nerves) sends electrical signals that control all other body systems.

  4. The skeletal system protects organs and gives the body its ___.

    Show answer

    Answer: structure

    Bones give the body its shape (structure) and protect vital organs like the brain and heart.

  5. What gas do the lungs remove from the blood and breathe out?

    1. Oxygen
    2. Nitrogen
    3. Carbon dioxide
    4. Hydrogen
    Show answer

    Answer: Carbon dioxide

    The lungs remove carbon dioxide — a waste gas — from the blood and expel it when you exhale. They bring in oxygen when you inhale.

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