PTA135-Unit6-Bone and Joints

Question 1

Name the 2 components of bone

Answer 1

• cortical (compact, dense)

- cancellous (spongy, trabecular)

Question 2

discuss Cortical bone

Answer 2

 Compact
 Dense, hard on all surfaces
 Outer shell that defines the shape of the bone
 Located in the diaphyseal portion of long bones
 Major structural subunit is Osteon
 Subject to bending, torsion, and compressive forces
 30% porous

Question 3

discuss Cancellous bone

Answer 3

 Trabecular
 Spongy
 Appears as a complex lattice of bone matrix fibers that orient along specific lines of
stresses, strains, and compressive forces
 Found within epiphyses at the ends of long bones (Marieb p. 178)
 Found within the medullary canal of long bones
 50% to 90% porous

Question 4

Name the 3 functions of bone

Answer 4

• mechanical
• mineral storage
• hemapoetic

Question 5

discuss the Mechanical function of bone

Answer 5

 Support – framework to support the body – legs act as pillars, rib cage supports
thoracic wall
 Protection – skull protects brain, vertebrae protect spinal cord, rib cage protects
chest organs
 Movement‐ muscles use bones as levers to move the body and its parts

Question 6

discuss the Mineral Storage function of bone

Answer 6

A reservoir for 
calcium, 
phosphate, 
sodium, 
magnesium, 
growth factors

Question 7

discuss the Hemapoetic function of bone

Answer 7

Formation of RBC, WBC, platelets
 Found in pelvis, sternum, skull, ribs, vertebrae, scapulae and epiphyseal ends of
femur and humerus

Question 8

define Diaphysis

Answer 8

The body or shaft of the long bone

 Forms the long axis

Question 9

define Metaphysis

Answer 9

The portion between the diaphysis and the epiphysis of a developing long bone
 The growth area of the bone

Question 10

define Epiphysis

Answer 10

End of the long bone

 Separated from the diaphysis by the epiphyseal plate

Question 11

define Osteoblast

Answer 11

Formation of bone and type I collagen
 The cell that synthesizes type I collagen
 Has a large volume of endoplasmic reticulum, Golgi apparatus and mitochondria to synthesize
collagen and secrete matrix proteins

Question 12

define Osteocyte

Answer 12

Maintain bone as living tissue
 What the osteoblast becomes when it is done forming bone
 Actually is osteoblast that is embedded within newly formed mineralized bone matrix
 Fewer organelles but greater nucleus to cytoplasmic ratio than osteoblasts

Question 13

define Osteoclast

Answer 13

Absorption and removal of unwanted tissue

 Giant cell multinucleated bone resorption cell

Question 14

define Wolff’s Law

Answer 14

Intermittent physiologic loads applied to bone stimulate adaptive responses.
 Intermittently applied stress, as well as changes in function of bone, causes definite changes.
 Bone grows or remodels in response to the forces on it.
 Bone is laid down where needed and resorbed where not needed.
 “a bone grows or remodels in response to the demands placed on it”

Question 15

describe the general process of bone remodeling

Answer 15

Phenomenon of cellular turnover
 Normal dynamic process of bone synthesis and resorption
 Occurs on periosteal, endosteal, trabecular, and haversian canal portions of bone
 A lifelong activity that responds to mechanical stress
 See Wolff’s Law
 Functions in reshaping or replacement of bone during growth and following injury
 Phase IV of fracture repair ‐ Hard callus is gradually reshaped to the original anatomical bone
shape
Bone resorption by osteoclasts
 Bone deposit by osteoblasts
 Bone mineralization/maintenance by osteocytes

Question 16

describe the clinical manifestation of Achondroplasia

Answer 16

 aka Dwarfism
 short arms and legs (decreased growth in long bones)
 normal sized hands, feet, body
 relatively normal‐sized head
 small jaw and bulged forehead (maybe)
 mental status usually normal
 increased thoracic kyphosis and lumbar lordosis
 bowing of the legs
 hypotonia
 waddling gait pattern
 “trident hand”
 spinal stenosis

Question 17

state the Indications for TKA

Answer 17

 destruction to the knee joint due to severe arthritis or trauma
 inability to move the knee
 eliminate and reduce pain
 improve functional activities in disabled individuals
 osteoarthritis (degenerative joint disease)
 rheumatoid arthritis
 previous trauma

Question 18

state the Precautions for THA - posterolateral, posterior or lateral approach

Answer 18

avoid hip adduction
 avoid hip internal rotation
 avoid hip flexion greater than 90 degrees
 avoid combination of all three for up to 4 months after surgery
o avoid sitting on low surfaces, crossing legs, sleeping on side without pillow,
bending forward at hips

Question 19

state the precautions for THA - anterior approach

Answer 19

 avoid hip extension

 avoid hip external rotation

Question 20

define Autoimmune Disease

Answer 20

 A disorder in which the body’s immune system forms antibodies that attack
healthy tissue and organs
 The immune system can’t tell the difference between healthy body tissue and
antigens

Question 21

characteristics of Autoimmune Disease

Answer 21

Many characteristics that make it difficult to tell one from another:
 Synovitis (joint)
 Pleuritis (pleura)
 Myocarditis (heart muscle)
 Endocarditis (inner layer of the heart)
 Pericarditis (tissue surrounding the heart)
 Nephritis (kidney)
 Peritonitis (inner wall of abdomen)
 Connective tissue alterations
 Muscle and/or joint pain
 Skin rash
 Fatigue
 Malaise