Skeletal System

Skeletal System

Bones:•22 skull•27 hand•26 foot

Skeletal System (cont.)

# of bones:•Adults 206•Babies 300

Function of Bones1. Support

for body and organs2. Protection

for the brain, spinal cord, and

vital organs3. Movement

levers for muscles4. Mineral storage – Ca, P5. Blood cell formation

occurs in the marrow of bones

Division of Bones:1. Axial skeleton –

skull, vertebral column, sternum, rib cage

2. Appendicular skeleton –upper & lower limbs, shoulder, hip

Axial Skeleton

Appendicular

Skeleton

Classification of Bones:

• Long bones:Arm and leg bones

• Short bones:Wrist bones

• Flat bones:The bones of the skull

• Irregular bones: Facial bones or vertebrae

Structure of Bones:

• Bones are solid networks of living cells and protein fibers that are surrounded by deposits of calcium salts.

Compact & Spongy Bone

• Dense & strong• Provides strength & protection

• Outermost part of the bone

Compact Bone:

• Less dense & contains bone marrow

• Found in short, flat, and long bones

• Surrounded by compact bone

Spongy Bone:

Structure of Long Bone

Figure 6.3a,b

Structure of Long Bone• Periosteum- tough layer of connective tissue

• Compact bone- found beneath periosteum

• Haversian canals- network of tubes that run through compact bone & contain blood vessels and nerves.

Structure of Long Bone:• Spongy bone- ends of long bones & middle of short, flat bones. Adds strength w/o mass!

Within bones are cavities that contain a soft tissue called bone marrow.

Structure of Long Bone:• Two types of bone marrow: Yellow bone marrow- made up of fat cells

Red bone marrow- produces red blood cells, white blood cells, & platelets

Structure of Long Bone

Bone Cells:• Osteocytes- mature bone cells that are embedded in the matrix

• Osteoclasts- break down bone

• Osteoblasts- produce bone

Stop growing- late teens! Our Bones are continuously remodel throughout our lives.

OsteoporosisOsteoclast activity is faster than osteoblast activity!

Osteoporosis

Development of Bones:

• Skeleton of embryo almost entirely cartilage:Cartilage is a type of connective tissue that is made up of a network of protein fibers (both tough collagen & flexible elastin).

Development of Bone Cont’d: • Cartilage does not contain

blood vessels!• Cartilage is replaced by bone during the process called ossification:Osteoblasts secrete mineral deposits that replace cartilage with bone.

Osteoblasts surrounded by bone tissue – now osteocytes

Growth:• Long bones contain growth plates called epiphyseal lines at either ends

Growth: •Growth of cartilage at these plates causes the bones to lengthen.

•Gradually cartilage replaced by bone- a.k.a. ossification

•Late adolescence/ early adulthood growth plates replaced by bone- stop growing!

•Cartilage in adults found:

- nose, external ears, attach ribs to sternum

Epiphyseal Fracture

Bone Connections• Joints- place where one bone attaches to anotherClassified by movement:ImmovableSlightly movableFreely movable

• Ligaments hold bone to bone

Immovable Joints: •Allow no movement•Bones are interlocked and held together by connective tissue or fusedExample: skull bones

fixed

Slightly Movable Joints:

• Permit a small amount of restricted movement

• Bones are separated from each other

• Example:Joints between lower leg Joints between adjacent vertebrae

inter-vertebral

joints

Freely Movable Joints:

• Permit movement in one or more directions

• Grouped according to shapes of the surfaces of the adjacent bones. Ball- and- Socket JointHinge JointPivot JointSaddle Joint

Ball-and-Socket Joint:

• Permits movement in many directions

• Allows for widest range of motion

• Example:Humerus bone and scapula

ball & socket

Hinge Joint:

•Permits back and forth motion

•Example:Femur and tibia/fibula

Like open and closing a door!

hinge joint

Pivot Joint:

•Allow one bone to rotate around

another. •Example:

Humerus and radius/ulna

pivot joint

Saddle Joints:

• Permits one bone to slide in two directions.

• Example:Metacarpals with your carpals

saddle joint

Structure of Joints: • Cartilage covers the surfaces where two bones come together (protects bones)

• Joint capsule helps hold bones together & consists of two layers:LigamentsSynovial fluid

Structure of Joints Cont’d: • Ligaments- hold bones together in a joint

• Synovial fluid- produced by cells enables surfaces of the joint to slide over each other smoothly.

Skeletal Conditions•Bursitis•Scoliosis•Osteoporosis

•Arthritis•Sprain•Fracture

Bursitis

• Inflammation of the bursa (sac)

•Curvature of the spine

Scoliosis

Osteoporosis

• Inefficient bone replacement

• 5-10% of bone mass lost every 10 years past age of 40

Rate of bone eating cells exceeds bone building cells!

Arthritis• Joint inflammation

•Lose strength & functionEx. Rheumatoid arthritis

Rheumatoid arthritis

Sprain•Over stretching of ligaments or tendons

•Torn ligaments require surgery

Fracture

•Broken bone

•Multiple types

• Simple fracture:Bone breaks but does not come through the skin

Types of Fractures:

• Compound fracture:Bone protrudes through the skin

Types of Fractures:

• Stress fracture:A thin crack in the bone

Types of Fractures: