Your Skeletal SystemYour Skeletal System7th Grade Science7th Grade Science

44thth Quarter Quarter

BonesBones• Your bones are part of Your bones are part of

your skeleton.your skeleton.• Your bones give your Your bones give your

body support. Without body support. Without your bones you could your bones you could not sit or stand, walk not sit or stand, walk or run, skate, or swim.or run, skate, or swim.

• Your bones protect the Your bones protect the important organs in important organs in your body.your body.

BonesBones• Your bones protect Your bones protect

the important the important organs in your body.organs in your body.

• The skull protects The skull protects the brain. It is like a the brain. It is like a hard hat.hard hat.

• Your ribs protect the Your ribs protect the heart, lungs, and heart, lungs, and stomach. stomach.

Interesting FactsInteresting Facts• You were born with 300 bones. By You were born with 300 bones. By

the time you graduate from high the time you graduate from high school you will have 206 bones.school you will have 206 bones.

• How many more bones did you have How many more bones did you have when you were born than you will when you were born than you will have when you graduate?have when you graduate?

Speedy Bone FactsSpeedy Bone Facts• The femur is the thigh bone. It is the The femur is the thigh bone. It is the

largest bone in the body. largest bone in the body. • The shortest bone is in your middle The shortest bone is in your middle

ear. It is called the stirrup, or stapes.ear. It is called the stirrup, or stapes.• More than half the bones in your More than half the bones in your

body are in your hands and feet.body are in your hands and feet.• Humans have the same number of Humans have the same number of

neck bones as giraffes and mice.neck bones as giraffes and mice.

• The femur is the thigh bone. It is the The femur is the thigh bone. It is the largest bone in the body. largest bone in the body.

• The shortest bone is in your middle The shortest bone is in your middle ear. It is called the stirrup, or stapes.ear. It is called the stirrup, or stapes.

• More than half the bones in your More than half the bones in your body are in your hands and feet.body are in your hands and feet.

• Humans have the same number of Humans have the same number of neck bones as giraffes and mice.neck bones as giraffes and mice.

BonesBones• Bones are made of cells.Bones are made of cells.• Bones are living parts of your body Bones are living parts of your body

that grow and change just as you do.that grow and change just as you do.• You began your life with 300 bones. You began your life with 300 bones.

As you grow your bones fuse As you grow your bones fuse together. How many bones will you together. How many bones will you have when you graduate?have when you graduate?

A Closer Look at BonesA Closer Look at Bones• The outside of the bone is hard. It is The outside of the bone is hard. It is

made up of living bone cells that made up of living bone cells that form rings around tiny canals form rings around tiny canals through which blood vessels pass. through which blood vessels pass.

• The inside is a honeycomb of bone The inside is a honeycomb of bone cells with spaces between them. This cells with spaces between them. This is called spongy bone.is called spongy bone.

• Minerals are stored inside the bone.Minerals are stored inside the bone.

A Closer Look at BonesA Closer Look at Bones• The hollow centers of many bones are The hollow centers of many bones are

filled with jellylike red and yellow filled with jellylike red and yellow marrow.marrow.

• Yellow marrow stores fat and releases Yellow marrow stores fat and releases it when it is needed elsewhere in the it when it is needed elsewhere in the body.body.

• Red marrow is a tissue that makes red Red marrow is a tissue that makes red and white blood cells and platelets.and white blood cells and platelets.

A Closer Look at BonesA Closer Look at Bones• Red bone marrow makes up to five Red bone marrow makes up to five

thousand million red bloods cells and thousand million red bloods cells and thousands upon thousands of white thousands upon thousands of white blood cells and platelets each day.blood cells and platelets each day.

A Closer Look at BonesA Closer Look at Bones• Red blood cells are Red blood cells are

the cells that carry the cells that carry oxygen throughout oxygen throughout the body.the body.

A Closer Look at BonesA Closer Look at Bones• White blood cells White blood cells

are the cells that are the cells that fight disease and fight disease and infection.infection.

A Closer Look InsideA Closer Look Inside• The platelets help the blood to clot The platelets help the blood to clot

after injury.after injury.

Bone ConnectionBone Connection• Bones are connected together by Bones are connected together by

ligaments at the joints.ligaments at the joints.• Cartilage is another kind of Cartilage is another kind of

connective tissue found in joints and connective tissue found in joints and at the ends of bones.at the ends of bones.

• Bones are moved by muscles that Bones are moved by muscles that are attached to themare attached to them

What is a skeleton?What is a skeleton?• The skeleton is a The skeleton is a

column of column of interlinked bones, interlinked bones, with two legs with two legs attached at the attached at the bottom and two bottom and two arms and a skull arms and a skull attached at the attached at the top.top.

The SkullThe Skull• The skull is a bony case that supports The skull is a bony case that supports

and protects the brain and some of and protects the brain and some of the body’s sense organs, such as the the body’s sense organs, such as the eyes and ears.eyes and ears.

• There are twenty-nine different bones There are twenty-nine different bones in the skull.in the skull.

• The part of the skull that surrounds The part of the skull that surrounds the brain is called the cranium.the brain is called the cranium.

The SKullThe SKull• Fourteen facial bones form the Fourteen facial bones form the

framework for the eyes, nose, framework for the eyes, nose, cheekbones, and upper and lower jaw.cheekbones, and upper and lower jaw.

• Upper jaw is called the maxilla.Upper jaw is called the maxilla.• Lower jaw is called the mandible. Lower jaw is called the mandible. • The lower jaw can move from side to The lower jaw can move from side to

side and up and down.side and up and down.

BackboneBackbone• Your backbone, or spine is a flexible Your backbone, or spine is a flexible

column of bones that runs sown the column of bones that runs sown the middle of your body.middle of your body.

• It is made up of thirty-three small It is made up of thirty-three small bones called vertebraebones called vertebrae

Rib Cage and SternumRib Cage and Sternum• Your rib cage forms Your rib cage forms

a protective shell a protective shell for some of your for some of your most important most important organs, including organs, including your heart, lungs, your heart, lungs, stomach, and liver.stomach, and liver.

Clavical and Shoulder BoneClavical and Shoulder Bone

HandsHands• The hand has The hand has

twenty-seven bones twenty-seven bones in three groups: the in three groups: the phalanges in the phalanges in the fingers and thumbs, fingers and thumbs, the carpals in the the carpals in the wrist, and the wrist, and the metacarpal in the metacarpal in the palm.palm.

Hands Hands • There are fourteen finger bones – three There are fourteen finger bones – three

in each finger and two in each thumb.in each finger and two in each thumb.• The joints in the fingers are called The joints in the fingers are called

knuckles. knuckles. • The wrist is made up of eight small The wrist is made up of eight small

bones arranged in two rows and held bones arranged in two rows and held tightly with ligaments. tightly with ligaments.

• Five long bones make up the palm.Five long bones make up the palm.

Names of BonesNames of Bones• Femur – thigh boneFemur – thigh bone• Pelvis - hip bonePelvis - hip bone• Cranium – skullCranium – skull• Ulna-Radius– lower arm bonesUlna-Radius– lower arm bones• Humerus – upper arm boneHumerus – upper arm bone