SM: Week 6

Question 1

What is Wolff’s Law?

Answer 1

It states that bony structures orient themselves in form and mass to best resist extrinsic forces (ie form and mass follow function)

Question 2

Why is the patella within the quadriceps tendon?

Answer 2

It improves mechanical advantage of the quads by transferring their force to the appropriate angle in relation to the tibia (think vectors)

Question 3

What is cauda equine syndrome and what symptoms do patients present?

Answer 3

It is an injury that affects all nerve roots below the location of injury and is a medical emergency

• patients present with saddle anesthesia, bowel or bladder incontinence or urinary retention
• damage is likely permanent after 6-8 hours

Question 4

What is trochanteric bursitis and how is it treated?

Answer 4

• Many patients present with “hip pain” which is lateral to hip joint ~ likely trochanteric bursitis
• Surgery is rarely done, instead PT and local injections used for treatment

Question 5

What is the primary concern with a hip fracture and/or dislocation?

Answer 5

Blood supply to the femur is crucial and is usually obstructed or damaged upon injury. If the injury is not reduced in a timely manner, then avascular necrosis can occur.
- Note: the main blood supply to the femur is through the medial femoral circumflex artery

Question 6

Upon observing a patient with a hip dislocation, what position indicates a posterior and an anterior dislocation?

Answer 6

• Posterior - hip internally rotated

- Anterior - hip/knee externally rotated

Question 7

Describe the blood supply to the menisci.

Answer 7

o Blood supply does not directly reach all of the meniscus, particularly the middle. Unreached components receive nutrition via diffusion from synovial fluid.

o Note: richer blood supply in area of tear = more likely to heal after repair (can repair tear instead of removing meniscus)

Question 8

What are the tests used in a suspected ACL injury and how are they performed?

Answer 8

• Lachman’s test: knee flexion at 30 degrees, stabilize femur and pull tibia forward
• Anterior Drawer test (less sensitive compared to Lachman’s): Patient is supine, hips at 45 degrees, knees at 90 degrees, assessor sits on foot and pulls tibia forward; if tibia moves without an end point this is a positive test for an ACL tear

Question 9

Where does the Medial Collateral Ligament usually tear?

Answer 9

Almost always tears at femur, not along joint

Question 10

What does a patient present with in Osgood-Schlatter syndrome?

Answer 10

Tenderness and swelling at site of infrapatellar tendon insertion into tibial tubercle; usually present in tall, active male adolescents

Question 11

What ligaments are involved in an inversion ankle sprain?

Answer 11

• Anterior talofibular
• Calcaneal fibular
• Posterior talofibular

Question 12

What action causes a bilateral calcaneal fracture?

Answer 12

Jumping, running away from police (yep!)

Question 13

What causes Volkman’s ischemic contracture of the hand?

Answer 13

It is caused by a compartment syndrome and causes the hand to contract due to lack of blood supply.

Question 14

What is the WBC that is elevated during viral infections?

Answer 14

Lymphocytes; also elevated in TB and typhoid infections

Question 15

What is the WBC that is elevated during bacterial infections?

Answer 15

Neutrophils - particularly high in acute bacterial infections

• bands = immature neutrophils and is called a “left shift”

Question 16

What does an ESR test examine and what conditions does it indicate in the body?

Answer 16

• Rate at which red blood cells precipitate in 1 hour when anti-coagulated blood is allowed to stand.
• Rough measure of abnormal acute phase proteins and immunoglobulins.
• Nonspecific indicator of tissue damage and inflammation.

Question 17

What does CRP do in the body and where is it produced?

Answer 17

• Involved in promotion of the immune system through activation of the complement cascade
• Produced in the liver and present in circulation at low levels normally

Question 18

Hyaline Cartilage: where is it found in the body, what type of collagen fibers does it possess, and what feature(s) are seen in a histology slide?

Answer 18

• Found in nose, rings of the trachea, anterior extensions of ribs connecting to sternum, formation of fetal skeleton (becomes ossified), articular surfaces of joints
• Type II collagen fibers
• Histo: many isogenous groups with chondrocytes within lacunae, no visible fibers, smooth glossy appearance

Question 19

Elastic Cartilage: where is it found in the body, what type of collagen fibers does it possess, and what feature(s) are seen in a histology slide?

Answer 19

• Found in outer ear (pinna), , supporting wall to external auditory canal, epiglottal cartilage, some components of laryngeal cartilage
• Type II collagen fibers, also elastic fibers (eosinophilic)
• Histo: lacunae and isogenous groups are more numerous compared to hyaline cartilage, can see presence of elastic fibers (can be very dark depending on staining process); more cellular than hyaline

Question 20

Fibrocartilage: where is it found in the body, what type of collagen fibers does it possess, and what feature(s) are seen in a histology slide?

Answer 20

• Found in annulus fibrosis (intervertebral discs), pubic symphysis,
• Type I collagen (able to visualize)
• Histo: chondrocytes are lined up and have multiple collagen fibers running parallel to each other

Question 21

What is appositional growth in cartilage?

Answer 21

Appositional growth = new cells at periphery of existing cartilage

Question 22

What is interstitial growth in cartilage?

Answer 22

Interstitial growth involves the expansion of cartilage from within an existing block of cartilage (bone cannot do this since it is mineralized)

Question 23

Define perichondrium.

Answer 23

Perichondrium: layer of dense irregular connective tissue that surrounds the cartilage of developing bone

Question 24

Define chondroblast.

Answer 24

Chondroblasts: active cells, eventually get embedded and become chondrocytes

Question 25

Define chondrocyte.

Answer 25

Chondrocyte: quiescent or relatively inactive cartilage cells

Question 26

Define lacuna.

Answer 26

Lacuna: spherical space, initially holds a chondrocyte, which divides and forms the new isogenous group

Question 27

Define isogenous group.

Answer 27

Isogenous group: cluster of chondrocytes (rarely more than 4) formed through division of one progenitor cell

Question 28

Define aggrecan.

Answer 28

Aggrecan: Proteoglycan with many chondroitin sulfates, keratin sulfates, and heparin sulfates covalently bound to a protein backbone

Question 29

Define chondronectin.

Answer 29

Chondronectin: Adhesive glycoprotein, has multiple binding sites: type II collagen, chondroitin-4 and -6 sulfates, integrins of chondroblasts and chondrocytes

Question 30

Define territorial and extraterritorial matrix.

Answer 30

Territorial and extraterritorial matrix: found in hyaline cartilage. Area surrounding the lacunae has more proteoglycan aggregates, is more basophilic, thus the territorial matrix ring is dark as compared to the greater surrounding area, the extraterritorial matrix

Question 31

How does cartilage receive nutrients?

Answer 31

Cartilage is avascular so it relies on receiving nutrients via diffusion, thus repair of damaged cartilage is poor.

Question 32

What is the function of an osteoblast and what is the process?

Answer 32

• Osteoblast: responsible for bone formation
  o Form “epithelioid” appearance on bone surfaces, cuboidal to columnar when active
  o Two step process: synthesis of organic matrix (osteoid), then deposition of inorganic components (phosphate binds with calcium) within osteoid = mineralization
  o Have surface receptors for parathyroid hormone; When bound, releases osteoclast stimulating factor.

Question 33

What is the function of an osteocyte?

Answer 33

• Osteocyte: formed by osteoblasts, become trapped by bone formation around them
  o Communicate via gap junctions for cell-cell coordination and nutrient transfer
  o Necessary for maintenance of matrix and regulation of calcium
  o As osteocytes die, matrix is resorbed.

Question 34

What is the function of canaliculi?

Answer 34

• Canaliculi: Tiny canals that processes between osteoblasts get stuck in during mineralization

Question 35

What is the function of an osteoclast?

Answer 35

• Osteoclast: derived from monocytes, abundant lysosomes, capable of eroding bone to allow for remodeling
  o Amitotic, multinucleated with numerous cell processes
  o Ruffled border: microvilli where osteoclast lies against bony surface
  • Membranes pump H+ into sub-osteoclastic compartment
  • Lower pH causes mineral liberation which leads to minerals entering osteoclast and dump out other side to capillaries

Question 36

What is a Howship’s Lacunae

Answer 36

• Howship’s lacunae: regions of resorbed matrix containing an osteoclast, appears as a depression in bone surface

Question 37

Define osteoid.

Answer 37

• Osteoid: organic matrix synthesized by osteoblasts prior to mineralization

Question 38

What are some of the components of bone matrix, both organic and inorganic?

Answer 38

o Inorganic: 50% of bone dry weight, primarily calcium phosphate/hydroxyapatite crystals
o Organic: composed of type I collagen and ground substance (includes chondroitin sulfate, keratin sulfate, hyaluronate, glycoproteins - 3 types of adhesive proteins with multiple binding sites for collagen, osteoblasts, osteocytes, and hydroxyapatite)

Question 39

Define lamellae.

Answer 39

• Lamellae: bone tissue that forms the layers of a Haversian system

Question 40

Define diaphysis.

Answer 40

• Diaphysis: Bone shaft between two epiphyseal plates; mostly compact bone

Question 41

Define metaphysis.

Answer 41

• Metaphysis: Spongy (cancellous) bone at extreme ends of diaphysis

Question 42

Define epiphysis.

Answer 42

• Epiphysis: Distal ends of long bones, articular cap of hyaline cartilage

Question 43

Define epiphyseal plate.

Answer 43

• Epiphyseal plate: junction between diaphysis and epiphysis; responsible for bone growth

Region where periosteum becomes continuous with perichondrium.

Question 44

Define periosteum.

Answer 44

• Periosteum: tough connective tissue, serves as an insertion point for tendons; has two layers:
  o Fibrous outer layer: contains fibroblasts, collagen, and elastin. Protects bone.
  o Osteogenic inner layer: contains mesenchymal precursors to osteoblasts. May contain osteoclasts if remodeling
• Features: blood vessels and nerves present, Sharpey’s fibers (collagenous) anchor periosteum to bone

Question 45

Define endosteum.

Answer 45

• Endosteum: between bone marrow and bone matrix; layer of osteoblasts, osteoclasts, and a few osteogenic cells

Question 46

Define medullary cavity.

Answer 46

• Medullary cavity: cancellous and contains a marrow cavity

o yellow marrow is filled with fat and is inactive; red marrow is active