human body systems: structure & movement

7/22/2019 Human Body Systems: Structure & Movement

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Human Body Systems:

Structure and Movement


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TheSkeletal

System


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The bones in your body are alive. They are made

of living tissues and cells. Bone cells take in

nutrients and use energy just like other body cells.


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Do you have any idea how many bones

you have?

Did you realize that the number of

bones you have changes from when

youre a baby to when youre grown up?


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Babies start out with over

300 bones. Since babies

have a lot of growing todo, some of the bones

theyll have as adults start

out in multiple pieces.

Over time, these bonesgrow together to form one

larger bone. By the time

youre an adult, youll

have exactly 206bones.Over half of those bones

can be found in your

hands and feet!


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Imagine what it would be like if you didnt have

any bonesYou wouldnt be able to stand up,

walk, or sit in a chair. You would look just like a

blob of skin. However if we didnt have bones, it

would affect more than just our appearance.

Bones have several important functions.


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Functions of Skeletal System

The skeleton gives shape and support to your body.

Bones protect your internal organs. For example, your skullprotects your brain.

Major muscles are attached to bone and help them move. Our bones are also responsible for making our blood. In the

middle of our bones is a spongy substance called marrow. Itis here that the body makes millions of new blood cells

every day to send out to the rest of your body. Large quantities of calcium and phosphorous are stored in

the skeleton for later use. (They are also what makes boneshard.)


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Bone Structure

The outer surface of a boneis a tough, tight-fittingmembrane called theperiosteum. It containsnerves and blood vessels andnourishes the bone.

Directly under theperiosteum is a layer of bonetissue called compact bone.It gives bones strength. Thisis the part you see when you

look at a skeleton. Spongy bone is located

toward the ends of longbones. It has many smallopen spaces that make bones

lightweight.


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Bone Structure

The innermost part of manybones contains bone marrow.Bone marrow is sort of like athick jelly, and its job is tomake blood cells.

The ends of bones are

covered with a smooth,slippery, thick layer of tissuecalled cartilage. It acts as ashock absorber and makesmovement easier by reducing

friction that would be causedby bones rubbing together atjoints. Bones are held in placeat joints by tough bands oftissue called ligaments.


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Bone Formation

Some of a baby's bones are made entirely of soft,flexible cartilage. Other bones in a baby are partlymade of cartilage. During childhood, as you aregrowing, the cartilage is slowly replaced by bone.

Bone-forming cells called osteoblastsdeposit calciumand phosphorus in bones, making the bone tissue hard.

Healthy bone tissue is always being formed andreformed. Osteoclastsare cells that help to sculpt and

shape bone by breaking down bone tissue. Whenosteoclasts break bone down, they also release thestored calcium and phosphorus into the bloodstreamwhere it can be used.


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Skeleton Humor


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The Muscular System

Did you know you have more than 600 muscles inyour body? Some are voluntary muscles that youcan control. You use voluntary muscles to help

you lift a heavy backpack, climb a mountain,smileOther muscles are involuntaryand cantbe controlled consciously. Your heart pumpsblood throughout your body and is an example of

an involuntary muscle. A muscleis an organ that can relax, contract, and

provide the force to move your body parts.


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Classification of Muscle Tissue

Three different types of muscles: smooth,

cardiac, and skeletal.

Smooth muscles are involuntary and are found in

your internal organs.

Cardiac muscle is found only in the heart.

Skeletal muscles are the muscles that show how

strong you are. They move bones. Tendonsattachskeletal muscles to bones.


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Musculoskeletal System

Quick Review
http://kidshealth.org/kid/interactive/muscles_it.htmlhttp://kidshealth.org/kid/interactive/muscles_it.htmlhttp://kidshealth.org/kid/interactive/muscles_it.htmlhttp://kidshealth.org/kid/interactive/muscles_it.htmlhttp://kidshealth.org/kid/interactive/muscles_it.html


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Dying to Be Strong

by Elizabeth Foy Larsen
http://www.scholastic.com/scopemagazine/PDFs/SCOPE-100113-Nonfiction.pdfhttp://www.scholastic.com/scopemagazine/PDFs/SCOPE-100113-Nonfiction.pdfhttp://www.scholastic.com/scopemagazine/PDFs/SCOPE-100113-Nonfiction.pdfhttp://www.scholastic.com/scopemagazine/PDFs/SCOPE-100113-Nonfiction.pdf


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The Skin

Your skin is the largest organ of your body.

Skin is made up of three layers of tissue: theepidermis, the dermis, and a fatty layer.


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Skin Structures

The epidermisis the thinnestouter layer. Cells in theepidermis producemelanina pigment thatprotects your skin and gives

it color. The dermisis the thick layer

below the epidermis. Itcontains blood vessels,nerves, muscles, oil, and

sweat glands. Below the dermis is a fatty

layer. It insulates the bodyand is where fat is oftenstored when a person gainsweight.


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Skin Functions

The skin carries out several major functions:

protection, sensory response, formation of

vitamin D, regulation of body temperature, and

ridding the body of wastes.

human body systems: structure & movement

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