The Skeletal System

The Skeletal System

• 206 bones in adult human (about 300 in babies)• Functions of the skeleton

– Support– Protection for internal organs (heart, brain, lungs, etc)– Provides movement– Stores minerals (calcium)– Site of attachment for muscles– Site of blood cell formation (from bone marrow)

Two Parts of a Skeleton

• Axial and appendicular skeleton– Axial skeleton – supports central part of body

and consists of skull, vertebral column (backbone), and rib cage

– Appendicular skeleton – limbs – consists of arms, legs, shoulders, and pelvis (hip)

The SkeletonSkull

Sternum

Ribs

Vertebral column

Metatarsals

Metacarpals

Phalanges

Clavicle

Scapula

Humerus

RadiusPelvisUlnaCarpals

Femur

Patella

Fibula

TibiaTarsals

Phalanges

Axial Skeleton

Appendicular Skeleton

The Male Skeleton vs. Female Skeleton

Types of Bone Joints

• Place where one bone attaches to another is a joint

• Some joints allow extensive movement (shoulder), while others are fixed (skull)

• Three types of bone joints– Immovable – fixed joints allowing no movement and

the bones may be interlocked (skull)– Slightly movable – small amount of restricted

movement (backbone)– Freely movable – allow movement in one or more

directions and there are four types of freely movable joints

Types of Freely Movable Joints

• Ball and socket – circular movement (leg and arm)• Hinge – back and forth movement (elbow and

knee)• Pivot – one bone rotates around another (lower

arm)• Saddle – one bone slides in two directions

(thumb/hand)

Freely Movable Joints

Ball-and-Socket Joint

Hinge Joint

Pivot JointClavicle

Ball-and-socket joint

ScapulaHumerus

Femur

Patella

Hinge jointTibia

Fibula

Humerus

Radius

Pivot joint

Ulna

Metacarpals

CarpalsSaddle joint

Structure of A Knee JointMuscle

Tendon

Femur

Patella

Bursa

Ligament

Synovial fluid

Cartilage

Fat

Fibula

Tibia

Structure of Bone Joints

• Connective tissue called a ligament holds bones together at a joint

• Arthritis is an inflammation of a joint

Structure of Bones

• Bones are living tissue made of living cells and protein surrounded by calcium

• Bone is surrounded by tough layer of connective tissue called periosteum

• Blood vessels in bone carry oxygen and nutrients to bone

Types of Bone and Marrow

• Two types of bone – compact and spongy– Compact bone – dense bone– Spongy bone – less dense, but very strong

and adds strength, but not mass

• Bone marrow is within cavities of bone and there are two types– Yellow bone marrow – made up of fat cells– Red bone marrow – produces red blood cells,

some white blood cells, and platelets

The Structure of Bone

Figure 27.28

CartilageSpongy bone(contains redbone marrow)

Compact bone

Central cavity

Yellow bone marrow

Fibrousconnective tissue

Blood vessels

Cartilage

Development of Bone

• When born, most of skeleton is cartilage

• Cartilage is replaced by bone during bone formation, called ossification

• When cartilage has been completely replaced, the person “stops growing”