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The Skeletal System
The Skeletal System
• 206 bones in adult human (about 300 in babies)
• Functions of the skeleton
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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 Skeleton
Skull
Axial
Skeleton
Clavicle
Sternum
Ribs
Vertebral
column
Scapula
Humerus
Radius
Pelvis
Ulna
Carpals
Metacarpals
Phalanges
Femur
Patella
Fibula
Tibia
Tarsals
Metatarsals
Phalanges
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
Pivot Joint
Clavicle
Humerus
Ball-andsocket
joint
Radius
Hinge Joint
Scapula
Pivot
joint
Ulna
Humerus
Femur
Patella
Fibula
Metacarpals
Tibia
Hinge
joint
Saddle joint
Carpals
Structure of A Knee Joint
Muscle
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
Figure 27.28
The Structure
of
Bone
Cartilage
Spongy bone
(contains red
bone marrow)
Compact bone
Central cavity
Yellow bone marrow
Fibrous
connective 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”