Lecture 16 – Survey of Bones (Continued)

What happens after a fracture?

  1. Sever bleeding; a clot forms at the site of the fracture.
  2. Periosteum – surrounding the bone is made of connective tissue cells for fibroblasts that form osteoblasts.  Osteoblasts are bone-forming cells that form fragments of bone within the clot.  The fragment plus the clot equals a CALUS.  The formation of a calus is an essential step in repairing a bone.
  3. Osteoblast formation of periosteum forms bone between the two fragmented ends.  This is called a collar.

Types of Joints

The science of joints is called arthrology.

  1. Fibrous Joints – A small amount of connective tissue between bones.  Example:  Sutures and bones of the calvarium (skull).
  2. Cartilagenous – Fibrocartilage between bones.  Example:  vertebrae –( intervertebral discs); pubic symphysis (between two pubic bones).
  3. Synovial Joints – syn – with; ovial – egg whites in natural state, not the yolk.  Example:  Humerus, which articulates with glenoid fossa; femur with acetabulum, which means vinegar cup.
  4. Hinge joints – Example: elbows.  These joints increase and decrease the angle of the arm.  Make a muscle like Popeye, the sailor man.  Then relax and straighten arm out to the side.  Hing joints are also found in the knee.
  5. Ball and socket joints-  A synovial joint, such as the shoulder or hip joint, in which a spherical knob or knoblike part of one bone fits into a cavity or socket of another.  Some degree of rotary motion is possible in every direction. Also called enarthrosis.

 Characteristics of a Synovial Joint

  1. Articular cartilage
  2. Synovial membrane produces synovial fluid
  3. Heavy connective tissue and joint capsule for stability and protection.  (I have difficulty watching baseball players slide into home plate!  That is stressful to the joints of the knee.  A little bit of learning is truly a dangerous thing, as Pope Alexander said.)
  4. Bursa cushion the joints by reducing friction caused by the surrounding muscles.  Not all synovial joints bursa; Bursa are found in knees and shoulders.
  5. Head and depression joints.  Examples:  Humerus and glenoid cavity; femur and acetabulum.
  6. Pivot joint – Example: radius with head pivot around the ulna.  This is why the anatomical position is important.  Palms must be forward in order for the ulna to be medial to the body.  If you have your palms facing backwards, the radius and ulna will pivot and change positions!
  7. Saddle joint – 1st metacarpal has a convex surface.

Joint Movement

  1. Flexion – biceps – decreasing in angle.
  2. Extension – increasing in angle
  3. Adduction – toward the midline (Adducter)
  4. Abducter – away from the midline.  For example, the deltoid muscle takes the arm away from the body.
  5. Circumduction – circular motion.

Bodies are meant to be in motion.  A sedentary lifestyle causes obesity and other illnesses, especially diabetes mellitus.  Get some form of exercise every day.  Enjoy your day.




Filed under The Skeletal System

2 responses to “Lecture 16 – Survey of Bones (Continued)

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    • Thank you. It is nice to know that my work and the jokes are not in vain. I make every effort to simplify complex medical topics. Have a successful academic year. Please stay with us as we have a lot of material to cover this year.


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