Bones: Joints and Injuries

Learning Objectives

By the end of this class you should understand:

• The bones of the three regions of the axial skeleton• The bones that form the three largest joints of the

appendicular skeleton• The structure of a major synovial joint• The differences between the different types of joint injuries

Axial Skeletal Regions• Skull– Composed of cranium and

facial bones

• Vertebral column– Supports weight– Houses/protects spinal cord

• Ribcage– Protects chest organs– Attaches to arms

Skull

• The skull made of many different bones

• Almost all bones (except jawbone) are fused together

• These fusions occur at a young age (newborn skulls are unfused so brain can grow)

Vertebral column

• The vertebral column is made of many vertebrae (singular vertebra)

• Vertebrae have two major parts:– Weight-bearing region with

cartilage pads between them– A ring of bone that

surrounds the spinal cord

Vertebra Structure

Ribcage

• The ribcage is created by 12 pairs of ribs that each attach to a vertebra

• Protect thoracic organs (heart, lungs, stomach, liver)

• The ribs attach directly or via cartilage to the sternum (breastbone)

Appendicular Skeleton

• The arms are attached to the axial skeleton via the pectoral girdle– Sternum is the attachment

point

• The legs are attached to the axial skeleton via the pelvic girdle– The pelvis, or os coxa, is the

attachment of the vertebrae to the hip bones

Joints

• A joint is a meeting point of two or more bones of the human body

• There are many classifications of joints– Suture: fused joint (e.g. skull)– Hinge joint: moves in 1 direction (e.g.

elbow)– Ball-and-socket joint: moves in 3

dimensions (e.g. shoulder)

• Any joint that moves is called a synovial joint

Pectoral Girdle

• The arm is attached to the axial skeleton at the sternum– The sternum attaches to the

clavicle (collar bone)– The clavicle attaches to the

scapula (shoulder bone)– The scapula attaches to the

humerus (upper arm bone) in a ball-and-socket joint

Pectoral Girdle

• The shoulder is one of the largest joints in the body

• Sacrifices strength to gain flexibility

• Can move in many directions due to additional motion of clavicle-scapula joint

Pelvic Girdle

• The pelvis (os coxae) is a fusion of the bottom of the vertebral column with three pairs of hip bones

• Together they form a socket that the ball of the femur (thigh bone) fits into

• This is a major joint but requires more strength and so has less flexibility

Leg Bones• The femur is the largest and

strongest bone in the body• The femur attaches to the tibia

(shin bone) at the knee– The patella (kneecap) is another

bone that forms part of this attachment

– The lower leg also has the fibula, which does not support any weight, only attachment for muscles

Synovial Joints

• The human body has many movable (synovial) joints

• The three most complex and vital ones for movement are the shoulder, hip, and knee

• As these joints are more complex, they have more protection

Wear and Tear

• A synovial joint does not have bone-to-bone contact like a fused joint– Would wear down the bones

• Has layers of cartilage and a synovial fluid for lubrication– Loss of protection leads to

friction, bone-on-bone grinding, etc

Joint Protection• Ligaments and tendons are

not permitted to rub against bones– Protected by fluid-filled sacs

called bursae (singular bursa)

• Inflammation of the bursa is called bursitis

• Tear or overstretch of the ligament is called a sprain

Anatomy of Major Joints

Joint Inflammation• A joint may become inflamed

with age– Referred to as arthritis

• Rheumatoid arthritis is an immune reaction to the joint

• Osteoarthritis is a wearing down of the cartilage on a joint and the subsequent thickening of the bone due to friction

Next week: muscles!