Structure and Support

Structure and Support

Middle School

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Learning Objectives

• Describe how cells form tissues and organs for specific body functions.

• Explain how the body is a system of interacting subsystems made of cells.

• Describe how muscular and skeletal systems work together for movement and support.

• Explain how plant structures like roots and stems provide support to the plant.

Key Vocabulary

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Cell

The cell is the most basic and smallest unit of all living things.

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Tissue

A tissue is a large group of similar cells that work together.

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Organ

An organ is a group of different tissues that work together to perform function.

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Organ System

An organ system is a group of organs that work together to perform major functions.

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Cell Wall

The cell wall is a rigid outer layer that provides structural support to plant cells.

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Muscle

Muscle is a type of tissue in the body that has the ability to contract.

Key Vocabulary

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Joint

A joint is the specific location in the body where two or more bones meet.

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Ligament

A ligament is a tough, flexible tissue that connects one bone to another bone, holding them together.

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Hydrostatic Skeleton

A hydrostatic skeleton is a structure found in soft-bodied animals consisting of a fluid-filled cavity.

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Exoskeleton

An exoskeleton is a hard, external covering on the outside of the body for support and protection.

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Skeletal Muscle

Skeletal muscle is a type of voluntary muscle that is attached to bones and helps move them.

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Cardiac Muscle

Cardiac muscle is a special type of involuntary muscle found only in the walls of the heart.

Key Vocabulary

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Smooth Muscle

Smooth muscle is a type of involuntary muscle found in the walls of internal organs.

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Roots

Roots are the part of a plant that anchors it and absorbs water and nutrients.

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Stems

Stems provide support to the plant and act as a transport system for water and nutrients.

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From Cells to Systems: The Body's Organization

• All living things are made of cells, the smallest unit of life.

• Groups of specialized cells that work together are called tissues, like nervous tissue.

• Different tissues combine to form organs, which have a specific job to do.

• Organs work together in organ systems to keep the body running.

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Multiple Choice

What is the smallest, most basic unit that makes up all living things?

• A cell

• A tissue

• An organ

• An organ system

Multiple Choice

What is the relationship between cells, tissues, and organs in the body?

• Cells group together to form tissues, and tissues combine to form organs.

• Organs combine to form tissues, and tissues group together to form cells.

• Tissues are made of organs, which are made of specialized cells.

• Cells, tissues, and organs are all separate and do not work together.

Multiple Choice

If an organ within an organ system is damaged, what is the most likely effect on the body's organization?

• The organ system that relies on that organ may not function correctly.

• Only the tissues that make up the organ will be affected.

• The cells in the organ will immediately stop working.

• The body will instantly create a new organ to take its place.

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Cellular Support: Cell Walls and Membranes

Plant Cells

• They have a cell membrane that controls what enters and leaves the cell.

• An additional rigid cell wall provides strength and structural support to the cell.

• This strong wall helps the plant to stand upright and keep its shape.

Animal Cells

• They have a flexible cell membrane that forms the cell's outer boundary.

• They do not have a rigid cell wall like plant cells do.

• Animals rely on other structures, such as a skeletal system, for support.

Multiple Choice

What is the main function of the cell wall in a plant cell?

• To provide strength and structural support to the cell.

• To control what enters and leaves the cell.

• To form the cell's flexible outer boundary.

• To help the animal's skeletal system grow.

Multiple Choice

Which statement best compares the outer layers of plant and animal cells?

• Plant cells have both a cell wall and a cell membrane, while animal cells only have a cell membrane.

• Animal cells use their cell membrane for support, while plant cells do not.

• Plant cells have a flexible boundary, while animal cells have a rigid one.

• Animal cells have a cell wall, while plant cells have a cell membrane.

Multiple Choice

Based on the information provided, what would most likely happen to a tall plant if its cells lost their rigid cell walls?

• The plant would lose its shape and be unable to stand upright.

• The plant would develop a skeletal system for support.

• The cell membrane would become rigid to provide support.

• The plant would not be able to control what enters its cells.

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The Muscular and Skeletal Systems

Skeletal System

• The skeletal system is an organ system made up of organs like bones.

• These organs are composed of specialized tissues and cells that provide crucial support.

• This system provides your body with its fundamental shape and basic structure.

Muscular System

• The muscular system is an organ system composed of strong, contractile tissues.

• These tissues can pull on bones, which allows you to move around.

• Muscle cells have many mitochondria because they require a lot of energy.

Multiple Choice

What is the primary role of the skeletal system?

• To provide the body with its fundamental shape and structure.

• To pull on bones, which allows the body to move around.

• To provide a large amount of energy for cells to use.

• To be composed of strong, contractile tissues.

Multiple Choice

What is the relationship between the muscular and skeletal systems that allows for movement?

• Muscles are made of tissues that pull on bones to create movement.

• Bones are made of tissues that pull on muscles to create movement.

• The skeletal system provides the energy the muscular system needs.

• The muscular system gives the body its fundamental shape.

Multiple Choice

Based on the information provided, what is the best explanation for why muscle cells have many mitochondria?

• Moving the body's bones requires a large amount of energy.

• The mitochondria provide the bones with their structure.

• The muscle cells need to store calcium from the bones.

• Energy is needed to make the muscle tissues less flexible.

Joints and Skeletal Functions

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What Are Joints?

• ​Joints are where two or more bones meet, which provides bodily flexibility.

• ​​Ligaments are responsible for connecting bones to other bones and keeping them stable.

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Types of Movable Joints

• ​Ball-and-socket joints, like in the hips, allow for wide rotational movement.

• ​​Hinge joints, such as in the knees, allow back-and-forth bending motions.

• ​Pivot joints are found in the neck and allow for turning movements.

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More Skeletal Functions

• ​Bones provide protection for vital organs like the brain and the heart.

• ​​The skeletal system is also responsible for producing the body's red blood cells.

• ​It stores important materials the body needs, including minerals like calcium.

Multiple Choice

What is the primary function of joints in the skeletal system?

• To produce the body's red blood cells

• To provide flexibility where two or more bones meet

• To store important minerals like calcium

• To provide protection for the body's vital organs

Multiple Choice

What is the key difference between the joints in the knees and the joints in the neck?

• The way hinge joints and pivot joints move

• The number of bones connected by each joint

• The type of organs each joint helps protect

• The material stored inside the bones of the joint

Multiple Choice

Which statement provides the best conclusion about the variety of functions performed by the skeletal system?

• The hip's ball-and-socket joint allows for rotation, while the skeleton also produces red blood cells and protects organs.

• The knee's hinge joint allows for bending, while ligaments connect the bones to keep them stable.

• The neck's pivot joint allows for turning, while bones store important minerals like calcium.

• The skeleton provides flexibility for movement, while also storing minerals and producing red blood cells.

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Support in Animals Without Bones

Hydrostatic Skeleton

• Some animals use a fluid-filled cavity surrounded by muscle for support.

• This type of skeleton is found in soft-bodied animals like earthworms.

• It allows the animal to change its shape, which helps it move.

Exoskeleton

• An exoskeleton is a hard, external covering that supports an animal's body.

• Insects, spiders, and shellfish like crabs have this type of skeleton.

• This rigid shell provides both strong support and protection from predators.

Multiple Choice

What is the main function of both hydrostatic skeletons and exoskeletons?

• To provide support for the animal's body

• To help the animal digest its food

• To remove waste from the animal's cells

• To help the animal find a mate

Multiple Choice

How does the structure of a hydrostatic skeleton differ from that of an exoskeleton?

• A hydrostatic skeleton is a hard, internal structure, while an exoskeleton is a soft, flexible shell.

• A hydrostatic skeleton is a fluid-filled cavity, while an exoskeleton is a hard, external covering.

• A hydrostatic skeleton is used for protection, while an exoskeleton is used for changing shape.

• A hydrostatic skeleton is found in insects, while an exoskeleton is found in earthworms.

Multiple Choice

A soft-bodied animal lives in an ocean environment with many predators. Which type of skeleton would provide the best advantage for survival and why?

• A hydrostatic skeleton, because it allows the animal to change shape to hide.

• An exoskeleton, because its rigid shell offers protection.

• A hydrostatic skeleton, because it is more lightweight for escaping.

• An exoskeleton, because it is fluid-filled and can absorb impacts.

Three Types of Muscle

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Skeletal Muscle

• ​These muscles are attached to your bones to help you move.

• ​​You have conscious control over these muscles, making them voluntary.

• ​Examples include the muscles in your arms and legs for running.

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Cardiac Muscle

• ​This special muscle is found only in the walls of the heart.

• ​​It works automatically without you having to think about it (involuntary).

• ​Its main job is to continuously pump blood throughout your body.

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Smooth Muscle

• ​Smooth muscle is found in the walls of your internal organs.

• ​​You cannot consciously control this muscle type; it is also involuntary.

• ​It helps with processes like digestion in your stomach and intestines.

Multiple Choice

Which type of muscle is under your conscious control, allowing you to perform actions like running?

• Skeletal muscle

• Cardiac muscle

• Smooth muscle

• Involuntary muscle

Multiple Choice

How do the primary functions of cardiac muscle and smooth muscle differ?

• Cardiac muscle pumps blood throughout the body, while smooth muscle helps with processes like digestion.

• Cardiac muscle is voluntary, while smooth muscle is involuntary.

• Cardiac muscle is found in the stomach, while smooth muscle is found in the heart.

• Cardiac muscle helps move bones, while smooth muscle helps the heart beat.

Multiple Choice

Imagine you are running to catch a bus. Which statement best describes the muscle activity involved?

• Your skeletal muscles contract to move your legs, and your cardiac muscle pumps more blood.

• Your smooth muscles contract to move your legs, and your skeletal muscle digests your food.

• Your cardiac muscle is used for both walking and digesting the meal.

• Your smooth muscle pumps more blood, and your skeletal muscle moves your legs.

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Plant Structure and Support

• Plant support comes from its specialized cells, tissues, and different organs.

• ​Roots anchor the plant and absorb water using tissues with strong cell walls.

• Stems support the plant and transport substances with their strong, rigid tissues.

• The stem's strength comes from the millions of strong cell walls inside.

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Multiple Choice

What is the primary source of a plant's structural support?

• The amount of sunlight it receives.

• The type of soil it grows in.

• Its specialized cells, tissues, and organs.

• The color of its leaves and flowers.

Multiple Choice

How do the functions of roots and stems differ in supporting a plant?

• Roots absorb water, while stems absorb sunlight.

• Both roots and stems are responsible for anchoring the plant.

• Roots anchor the plant in the ground, while stems provide upright support above ground.

• Stems absorb nutrients from the soil, while roots transport them.

Multiple Choice

If the individual cell walls within a plant's stem became weak, what would be the most likely consequence?

• The roots would stop absorbing water from the soil.

• The plant would be unable to produce its own food.

• The stem's tissues would lose their rigidity, causing the plant to fall over.

• The leaves would be unable to release excess water.

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Common Misconceptions

Misconception	Correction
Organs work independently.	Organs are part of organ systems and work together to perform functions.
Muscles push on bones to create movement.	Muscles can only pull on bones when they contract and work in pairs.
Bones are only for support.	Bones also protect organs, produce red blood cells, and store calcium.
All animals have bones.	Many animals have a hydrostatic skeleton or a hard exoskeleton for support.

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Summary

• Living things are organized from cells to tissues, organs, and organ systems.

• The body is a system of interacting subsystems that perform necessary functions.

• Plant cells have a cell wall for support, while some animals have exoskeletons.

• The muscular and skeletal systems work together for movement and support.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

• 1

• 2

• 3

• 4