Chapter 5The Skeletal System

Pgs 152-175

Vertebral Column

Intervertebral discs – flexible fibrocartilage pads, act as cushion and shock absorption

In young people, these are spongy and have a high water content (~90%)

In older people these dent to dry and weaken along with the ligaments of the vertebral column◦Predisposes elders to herniated (“slipped”) discs◦The protruding disc can press on the spinal cord or

nerves causing numbness and/or excruciating pain

Vertebral Column II

Abnormal curvatures of the spine may result in musculoskeletal back, hip and shoulder pain in adults – the number one cause for common doctors visits in the US

There are many types of curvatures which may result from congenital (present at birth) abnormalities, disease, poor posture, or unequal muscle pull on the spine◦Scoliosis – lateral curvature◦Kyphosis – upper back hunching, chin thrust

forward◦Lordosis – lower back curvature (sway back)

Review: Did you get it?1. What are the five major regions of the vertebral

column?2. How can you distinguish a lumbar vertebra from a

cervical vertebra?3. What is a true rib? A false rib?4. Besides the ribs and sternum, there is a third group

of bones forming the thoracic cage. What is it?5. What bone class do the ribs and skull bones fall into? 6. What is the single point of attachment of the

shoulder girdle to the axial skeleton?7. What bone forms the skeleton of the arm?8. Where are the carpals found, and what type of bone

are they?9. Which bones of the upper limb have a styloid

process?

Review: Did you get it?

1. What three bones form the hip bone? What two bones form each pectoral girdle?

2. In what three ways does the bony pelvis of a woman differ from that of a man?

3. What two bones form the skeleton of the leg?4. Bo’s longitudinal and medial arches have

suffered a collapse. What is the name of Bo’s condition?

5. Which lower limb bone has an intertrochanteric line and crest and an intercondylar fossa?

Joints

Every bone forms a joint (articulation) with at least one other bone◦ Exception = hyoid bone

Functions of joints:1. Hold bones together securely2. Give the rigid skeleton mobility

Joints are classified by structure and functionStructure classes:

◦ Fibrous - immovable◦ Cartilaginous◦ Synovial – freely movable

Function Classes: (Based on type of tissue that separate the bony regions at the joint◦ Synarthroses – immovable joints (axial)◦ Amphiarthroses - slightly moveable (axial)◦ Diarthroses – freely moveable

Joint Continued

Fibrous Joints Cartilaginous Joints

Example: sutures of the skull◦ Bones held in place by

tight CT fibersIn syndesmoses joints,

the fibesr are longer allowing more “give”◦ Ex: distal ends of the

itbia and fibula

Bone ends connected by fibrocartilage◦ Ex: pubic symphysis◦ Intervertebral joints

Joints Continued

Synovial Joints Bone ends are separated by a cavity containing synovial fluid 4 features:

◦ Articular cartilage◦ Articular capsule◦ Joint cavity◦ Reinforcing ligaments

Bursa and tendon sheaths not technically part of joint, but closely associated◦ Bags of lubricant which act like viscous ball bearings to reduce

friction between structures during movement◦ Bursae are flat discs, common where structures rub together◦ Tendon sheaths are elongated bursa that wrap around tedons like

hotdogs Dislocations occur when bones are moved out of their joint

cavity◦ Reductions are used to set the bones back in place

Joints based on Shape

Plane (gliding) joints – short slipping/gliding motions between bones. Motion is nonaxial

Hinge joint – uniaxial movement. Cylinder end of one bone fits into the trough of the other bone

Pivot Joint – Rounded end of one bone fits into a ring of another bone (or ligaments). Uniaxial

Condylar joint – egg shaped arciular surface of one bone fits into an oval cavity on the other. Allows eliptical movement, biaxial.

Saddle joints – each bone has a convex and concave area, works similar to a condylar joint

Ball and socket joint – multiaxial where spherical head of one bone fits into a cup-shaped socket of other bones.

Joints by shape

Homeostatic imbalance of the joints

BursitisSprainsArthritis – broad term for any joint inflammationOsteoarthritis (OA) – chronic degenerative

◦ Wear n’ tear arthritis. Bone spurs develop and “crepitus” may be heard upon movement

Rheumatoid arthritis (RA) – flare-ups and remissions. ◦ Chronic and autoimmune. The inflamed synovial membrane thickens

into “pannus” which erodes articular cartilages. The resulting scar tissue eventually ossifies and the bone ends fuse (ankylosis).

◦ Anti-inflammatory drugs and immunosuppressant drugs often prescribed. Sometimes joint replacements or bone removal are necessary

Gouty arthritis (gout) – needle-shaped deposits of uric acid form in the soft tissues of the joint◦ More common in men and likely genetic. Often affects a single joint

and can be destructive if untreated.