The skin over the anterior distal thigh above the patella is innervated by which of the following sensory segmental levels:
1) T12
3) L2
2) L1
5) L4
4) L3
The skin over the thigh is innervated by the L1, L2, and L3 sensory segmental levels. Remember:
• L1 Thigh, proximal third, and anterior
• L2 Thigh, middle, and anterior
• L3 Thigh, distal third, and anterior
Correct Answer: L3
702. (1069) Q2-1376:
The skin of the anterior middle third of the thigh is innervated by which of the following sensory segmental levels:
1) T12
3) L2
2) L1
5) L4
4) L3
The skin over the thigh is innervated by the L1, L2, and L3 sensory segmental levels. Remember:
• L1 Thigh, proximal third, and anterior
• L2 Thigh, middle, and anterior
• L3 Thigh, distal third, and anterior
Correct Answer: L2
703. (1070) Q2-1377:
The skin of the proximal one-third of the anterior thigh just distal to the inguinal ligament is innervated by which of the following sensory segmental levels:
1) T12
3) L2
2) L1
5) L4
4) L3
The skin over the thigh is innervated by the L1, L2, and L3 sensory segmental levels. Remember:
⢠L1 Thigh, proximal third, and anterior ⢠L2 Thigh, middle, and anterior
⢠L3 Thigh, distal third, and anterior
Correct Answer: L1
704. (1243) Q2-1613:
The tibialis anterior muscle is principally innervated by which of the following segmental levels:
1) L1
3) L3
2) L2
5) L5
4) L4
The tibialis anterior muscle is primarily innervated by the L4 nerve root. The tibialis anterior muscle also receives innervation from L5. Patients with a weak or absent tibialis anterior muscle will have a drop foot or a steppage gait. The tibialis anterior muscle causes dorsiflexion and inversion of the foot and ankle
■Correct Answer: L4
705. (1244) Q2-1614:
The patellar tendon reflex is primarily transmitted through which of the following nerve roots:
1) L1
3) L3
2) L2
5) L5
4) L4
Although the patellar tendon reflex is transmitted primarily through the L4 nerve root, the L2 and L3 nerve roots also contribute to the fibers. A weak reflex is present if the L4 nerve root is completely cut even if there are still fibers of L2 and L3. This reflex is seldom completely absent unless the patient has primary muscle or anterior horn lesions
■Correct Answer: L4
706. (1245) Q2-1615:
The skin on the medial aspect of the leg and great toe is innervated by which of the following nerve roots:
1) L1
3) L3
2) L2
5) L5
4) L4
It is important to remember the sensory dermatomes when examining patients. The medial aspect of the leg, foot, and great toe are supplied by the L4 nerve root. The tibial crest separates the L4 and L5 dermatomes on the leg.
Note:
L4 Medial aspect of leg, foot, and great toe
L5 Lateral aspect of the leg and toes two through four
S1 Lateral aspect of the fifth toe
Correct Answer: L4
707. (1246) Q2-1616:
The extensor hallucis longus muscle is innervated by which of the following nerve roots:
1) L1
3) L3
2) L2
5) L5
4) L4
The extensor hallucis muscle is primarily innervated by the L5 segmental level. Remember that the L5 nerve root innervates the following muscles:
Extensor hallucis longus
Extensor digitorum longus and brevis
Gluteus medius
Correct Answer: L5
708. (1247) Q2-1617:
The extensor digitorum longus and brevis muscles are primarily innervated by which of the following nerve roots:
1) L1
3) L3
2) L2
5) L5
4) L4
The extensor digitorum longus and brevis muscles are primarily innervated by the L5 nerve root. Remember that the L5 nerve root innervates the following muscles:
Extensor hallucis longus
Extensor digitorum longus and brevis
Gluteus medius
Correct Answer: L5
709. (1248) Q2-1618:
The gluteus medius muscle is principally innervated by which of the following nerve roots:
1) L1
3) L3
2) L2
5) L5
4) L4
The gluteus medius muscle principally receives innervation from the L5 nerve root through the superior gluteal nerve. Although the principal innervation is from L5, there are contributions from L4 and S1
■Correct Answer: L5
710. (1249) Q2-1619:
Testing for the L5 nerve root can be accomplished through which of the following:
1) Patellar tendon reflex
3) Superficial anal reflex
2) Achilles tendon reflex
5) Beevor's sign
4) Tibialis posterior reflex
There is not a well-defined reflex arCfor the L5 nerve root. The tibialis posterior reflex can sometimes be elicited, and this reflex is mediated through the L5 nerve root.
Remember the other reflexes as well: Patellar tendon L4
Achilles tendon S1
Superficial anal reflex S2, S3, S4
Beevorâs sign refers to asymmetry of the segmental innervation of the rectus abdominus muscles. When a patient performs a sit- up, there is unilateral segmental nerve root loss
■Correct Answer: Tibialis posterior reflex
711. (1250) Q2-1620:
The skin on the lateral aspect of the leg and the dorsum of the foot between the second and fourth toes is innervated by which of the following nerve roots:
1) L1
3) L3
2) L2
5) L5
4) L4
The L5 dermatome covers the skin on the lateral leg and dorsum of the foot from the lateral border of the great toe to the medial border of the little toe.
Note:
L4 Medial aspect of leg, foot, and great toe
L5 Lateral aspect of the leg and toes two through four
S1 Lateral aspect of the fifth toe
Correct Answer: L5
712. (1251) Q2-1621:
The peroneus longus and brevis muscles are innervated by which of the following nerve roots:
1) L3
3) L5
2) L4
5) S2
4) S1
The peroneus brevis and longus muscles are principally innervated by the S1 nerve root through the superficial peroneal nerve. Although the innervation is principally S1, the nerve is derived from the L5 and S2 nerve roots, as well.
Remember that the muscles principally innervated by the S1 nerve root are: Peroneus longus and brevis
Gastrocnemius-soleus complex
Gluteus maximus
Correct Answer: S1
713. (1252) Q2-1622:
The medial and lateral gastrocnemius muscles principally receive their innervation through which of the following nerve roots:
1) L3
3) L5
2) L4
5) S2
4) S1
The medial and lateral gastrocnemius muscles are principally supplied by the S1 nerve root through the tibial nerve. Although the innervation is principally S1, the nerve is derived from the L5 and S2 nerve roots, as well.
Remember that the muscles principally innervated by the S1 nerve root are:
Peroneus longus and brevis Gastrocnemius-soleus complex Gluteus maximus
Correct Answer: S1
714. (1253) Q2-1623:
The Achilles tendon reflex (ankle reflex) is transmitted through which of the following nerve roots:
1) L4
3) S1
2) L5
5) S3
4) S2
The Achilles tendon reflex is based upon the triceps muscle group (medial and lateral gastrocnemius muscles and soleus muscle)
and is transmitted through the S1 nerve root.
Note the reflexes and the associated nerve roots: Patellar tendon reflex L4
Posterior tibial reflex L5
Achilles tendon reflex S1
Correct Answer: S1
715. (1254) Q2-1624:
Which of the following groups of nerve roots innervates the intrinsiCmuscles of the foot:
1) L2, L3, and L4
3) L4, L5, and S1
2) L4 and L5
5) S2 and S3
4) L5, S1, and S2
The intrinsiCmuscles of the foot are innervated by the S2 and S3 nerve roots. These muscles are difficult to test. Clawing of the toes occurs with intrinsiCmuscle paralysis.
The following nerve roots innervate important structures: L5, S1, and S2 Hip extension: gluteus maximus
L5, S1, and S2 Foot plantar flexion
L5, S1, and S2 Foot eversion
L4, L5, and S1 Hip abduction: gluteus medius
L4, L5 Foot dorsiflexion L4, L5 Foot inversion L2, L3, and L4 Hip adduction
L2, L3, and L4 Knee extension
L1, L2, and L3 Hip flexion: iliopsoas
Correct Answer: S2 and S3
716. (1255) Q2-1625:
Perianal sensation is derived from which of the following nerve roots:
1) L2, L3, and L4
3) L5, S1, and S2
2) L3, L4, and L5
5) S2, S3, S4, and S5
4) S1, S2, and S3
Perianal sensation is derived from the S2, S3, S4, and S5 nerve roots. The sensory distribution is as follows:
S4-S5 Innermost perianal ring
S3 Middle perianal ring
S2 Outermost perianal ring
Correct Answer: S2, S3, S4, and S5
717. (1256) Q2-1626:
Which of the following sensory segmental levels corresponds with the nipple line:
1) T2
3) T7
2) T4
5) T12
4) T10
It is important to know the sensory levels to localize pathologiCprocesses. In addition to knowing the innervation of selected muscles and the deep tendon reflexes, the clinician should also know the sensory levels.
Note:
T4 Nipple line
T7 Xiphoid process
T10 Umbilicus T12 Groin Correct Answer: T4
718. (1257) Q2-1627:
Which of the following segmental nerve levels corresponds to sensation at the xiphoid process:
1) T2
3) T7
2) T4
5) T12
4) T10
The skin over the xiphoid process area is innervated by the T7 nerve root.
It is important to know the sensory levels to localize pathologiCprocesses. In addition to knowing the innervation of selected muscles and the deep tendon reflexes, the clinician should also know the sensory levels.
Note:
T4 Nipple line
T7 Xiphoid process
T10 Umbilicus T12 Groin Correct Answer: T7
719. (1258) Q2-1628:
The skin over the umbilicus is innervated by which of the following levels:
1) T2
3) T7
2) T4
5) T12
4) T10
The skin of the umbilicus is innervated by the T10 level.
It is important to know the sensory levels to localize pathologiCprocesses. In addition to knowing the innervation of selected muscles and the deep tendon reflexes, the clinician should also know the sensory levels.
Note:
T4 Nipple line
T7 Xiphoid process
T10 Umbilicus T12 Groin Correct Answer: T10
720. (1259) Q2-1629:
The skin over the groin is innervated by which of the following segmental levels:
1) T2
3) T7
2) T4
5) T12
4) T10
The skin over the groin is innervated by the T12 level.
It is important to know the sensory levels to localize pathologiCprocesses. In addition to knowing the innervation of selected muscles and the deep tendon reflexes, the clinician should also know the sensory levels.
Note:
T4 Nipple line
T7 Xiphoid process
T10 Umbilicus T12 Groin Correct Answer: T12
721. (1260) Q2-1630:
Which of the following levels of the spinal cord principally innervates the main flexor of the hip:
1) T10, T11, T12
3) L2, L3, L4
2) L1, L2, L3
5) L5, S1, S2
4) L4, L5, S1
The iliopsoas muscle is the main flexor of the hip. The iliopsoas muscle receives innervation from the L1, L2, and L3 levels. One should remember the following nerve roots that innervate important structures:
L5, S1, and S2 Hip extension: gluteus maximus
L5, S1, and S2 Foot plantar flexion
L5, S1, and S2 Foot eversion
L4, L5, and S1 Hip abduction: gluteus medius
L4, L5 Foot dorsiflexion L4, L5 Foot inversion L2, L3, and L4 Hip adduction
L2, L3, and L4 Knee extension
L1, L2, and L3 Hip flexion: iliopsoas
Correct Answer: L1, L2, L3
722. (1261) Q2-1631:
Which of the following segmental levels innervates the quadriceps muscle:
1) T10, T11, T12
3) L2, L3, L4
2) L1, L2, L3
5) L5, S1, S2
4) L4, L5, S1
The quadriceps muscle is innervated by the femoral nerve from the L2, L3, and L4 levels. One should remember the following nerve roots that innervate important structures:
L5, S1, and S2 Hip extension: gluteus maximus
L5, S1, and S2 Foot plantar flexion
L5, S1, and S2 Foot eversion
L4, L5, and S1 Hip abduction: gluteus medius
L4, L5 Foot dorsiflexion L4, L5 Foot inversion L2, L3, and L4 Hip adduction
L2, L3, and L4 Knee extension
L1, L2, and L3 Hip flexion: iliopsoas
Correct Answer: L2, L3, L4
723. (1262) Q2-1632:
The skin over the anterior distal thigh above the patella is innervated by which of the following nerves:
1) T12
3) L2
2) L1
5) L4
4) L3
The skin over the thigh is innervated by L1, L2, and L3. Note:
L1 Thigh, proximal third, anterior
L2 Thigh, middle, anterior
L3 Thigh, distal third, anterior
Correct Answer: L3
724. (1263) Q2-1633:
The skin of the anterior middle third of the thigh is innervated by which of the following levels:
1) T12
3) L2
2) L1
5) L4
4) L3
The skin over the anterior middle third of the thigh is innervated by L1, L2, and L3. Note:
L1 Thigh, proximal third, anterior
L2 Thigh, middle, anterior
L3 Thigh, distal third, anterior
Correct Answer: L2
725. (1264) Q2-1634:
The skin of the proximal one-third of the anterior thigh just distal to the inguinal ligament is innervated by which of the following levels:
1) T12
3) L2
2) L1
5) L4
4) L3
The skin of the proximal one-third of the anterior thigh just distal to the inguinal ligament is innervated by L1, L2, and L3. Note:
L1 Thigh, proximal third, anterior
L2 Thigh, middle, anterior
L3 Thigh, distal third, anterior
Correct Answer: L1
726. (1265) Q2-1635:
The mechanism of action of the fluoroquinolone class of antibiotics, such as ciprofloxacin and gatifloxacin, is:
1) Inhibiting of cell wall synthesis
3) Inhibiting RNA synthesis
2) Selectively targeting bacterial topoisomerases (inhibit DNA replication)
5) Poisoning cytochrome Csystem
4) Inhibiting ribosomal translation
The fluoroquinolone class of antibiotics selectively target bacterial topoisomerases. Topoisomerases maintain the correct amount of supercoiling of DNA in both replicating and nonreplicating areas of the chromosomes.
Fluoroquinolones
Second generation
Ciprofloxacin, ofloxacin, and lomefloxacin
Third generation
Sparfloxacin and levofloxacin
Fourth generation
Trovofloxacin, gatifloxacin, and moxifloxacin
Correct Answer: Selectively targeting bacterial topoisomerases (inhibit DNA replication)
727. (1266) Q2-1636:
The fluoroquinolone class of antibiotics, including ofloxacin and ciprofloxacin, is especially useful (considered drug of choice) for osteomyelitis caused by which of the following organisms:
1) Pseudomonas
3) Staphylococcus epidermidis
2) Staphylococcus aureus
5) Streptococcus
4) Enterobacteriaceae
Ofloxacin and ciprofloxacin have been studied in the treatment of post-traumatiCosteomyelitis. When compared with parenteral antibiotics, the cure rate was 80% for the fluoroquinolones and 85% for the parenteral antibiotics. The cure rate for the fluoroquinolones was even higher against Enterobacteriaceae. They are considered the drug of choice for osteomyelitis according to the referenced article
■Correct Answer: Enterobacteriaceae
728. (1267) Q2-1637:
In which of the following groups of patients should fluoroquinolones such as ciprofloxacin not be used because of significant adverse effects:
1) Young women
3) DiabetiCpatients
2) Children
5) Patients with sickle cell anemia
4) Elderly patients
Fluoroquinolones may cause side effects to the musculoskeletal system that include arthralgias, chondrotoxicity, and tendinopathy. Cartilage damage was found in animal studies at therapeutiCdoses. The cartilage cells of the physeal plate were damaged.
Cartilage blistering, erosions, matrix degeneration, and chondrocyte loss were also present. The fluoroquinolones are not to be used in children, pregnant women, and nursing mothers unless under special circumstances (such as drug resistance in children with cystiCfibrosis).
The fluoroquinolones are safe in the other groups of patients. One should remember the following: Light-headedness and dizziness may occur in young women.
Nausea, vomiting, and diarrhea are the most common complications.
Nonsteroidal anti-inflammatory drugs taken in combination will worsen side effects. Photosensitivity may occur.
Achilles tendonitis and rupture may occur.
Correct Answer: Children
729. (1268) Q2-1638:
Which of the following musculoskeletal complications may occur in patients taking fluoroquinolones, such as ciprofloxacin:
1) Osteomalacia
3) Joint laxity
2) Osteoporosis
5) Parethesias
4) Tendon ruptures
Fluoroquinolones may cause side effects to the musculoskeletal system that include arthralgias, chondrotoxicity, and tendinopathy. Achilles tendonitis and rupture is the most common tendinopathy associated with fluoroquinolone use (usually ciprofloxacin). Fifty
percent of cases are bilateral. The interval to rupture is between 2 and 60 days.
Patients at increased risk include:
Patients older than 60 years of age
Patients with diabetes
Patients with impaired renal function
Patients who partake in strenuous sports activities
Correct Answer: Tendon ruptures
730. (1269) Q2-1639:
Which of the following proteins binds to osteoclast precursor cells and positively effects their final differentiation into osteoclasts:
1) Receptor activator of nuclear factor-kappa B (RANK)
3) Bone morphogenetiCprotein 7
2) Osteoprotegerin
5) Parathyroid hormone related protein (PTHrP)
4) Core binding factor alpha 1 (Cbfa1)
Four proteins that regulate osteoclast activation have been discovered:
1. Receptor activator of nuclear factor-kappa B (RANK) binds to a receptor on osteoclast precursor cells and positively effects their final differentiation into osteoclasts.
2. Osteoprotegerin is a soluble decoy receptor that resembles RANK and inhibits osteoclasts.
Core binding factor alpha 1 (Cbfa1) is a transcription factor (coded by the Cbfa1 gene) that is necessary and sufficient for differentiation of cells into osteoblasts and facilitates chondrocyte differentiation during enchondral bone formation
■Correct Answer: Receptor activator of nuclear factor-kappa B (RANK)
731. (1270) Q2-1640:
Which of the following proteins negatively effects precursor cells to form osteoclasts:
1) Receptor activator of nuclear factor-kappa B (RANK)
3) Bone morphogenetiCprotein 7
2) Osteoprotegerin
5) Parathyroid hormone related protein (PTHrP)
4) Core binding factor alpha 1 (Cbfa1)
Four proteins that regulate osteoclast activation have been discovered:
1. Receptor activator of nuclear factor-kappa B (RANK) binds to a receptor on osteoclast precursor cells and positively effects their final differentiation into osteoclast activation.
2. Osteoprotegerin is a soluble decoy receptor that resembles RANK and inhibits osteoclasts.
Core binding factor alpha 1 (Cbfa1) is a transcription factor (coded by the Cbfa1 gene) that is necessary and sufficient for differentiation of cells into osteoblasts and facilitates chondrocyte differentiation during enchondral bone formation
■Correct Answer: Osteoprotegerin
732. (1271) Q2-1641:
Which of the following proteins or genes is necessary for bone formation and induces osteocalcin (expressed exclusively by osteoblasts):
1) Sox-9 gene
3) Receptor activator of nuclear factor-kappa B (RANK)
Core binding factor alpha 1 (Cbfa1) and its gene (Cbfa1) have been described as anaboliCregulators of bone. Cbfa1 is a transcription factor and is responsible for the differentiation of precursor cells into osteoblasts. It also enhances differentiation of chondrocytes during enchondral bone formation. When there is deficiency of Cbfa1 there can be abnormal bone development, as in clediocranial dysplasia
The human genome is comprised of approximately what number of genes:
1) 1,000
3) 10,000
2) 5,000
5) 100,000
4) 30,000
The human genome is composed of approximately 30,000 unique genes. Each gene is composed of a promotor or regulator region and a transcriptional or coding region. Regulatory proteins or transcription factors bind to the promoter region of the gene
to signal the beginning of transcription of the DNA into RNA or repress the expression of the gene. The coding region contains both introns and exons. Exon sequences of the gene directly code for the proteins, and the introns are spacers. The intron sequences are enzymatically removed from the newly transcribed messenger RNA by a splicing mechanism
■Correct Answer: 30,000
734. (1273) Q2-1643:
Which of the following portions of a gene directly codes for the messenger RNA for eventual translation into proteins on the ribosome:
1) Promoter region
3) Exon
2) Intron
5) Activator or repressor binding site
4) Coding region
The human genome is composed of approximately 30,000 unique genes. Each gene is composed of a promotor or regulator region and a transcriptional or coding region. Regulatory proteins or transcription factors bind to the promoter region of the gene
to signal the beginning of transcription of the DNA into RNA or repress the expression of the gene. The coding region contains both introns and exons. Exon sequences of the gene directly code for the proteins, and the introns are spacers. The intron sequences are enzymatically removed from the newly transcribed messenger RNA by a splicing mechanism
■Correct Answer: Exon
735. (1910) Q2-2320:
Which of the following occurs in Pagetâs disease:
1) Inadequate mineralization of newly formed bone
3) Normal osteoclastiCactivity with decreased osteoblastiCactivity
2) Low bone mass and microarchitectural deterioration of bone
5) Increased osteoclastiCactivity and increased bone formation
4) Increased osteoclastiCactivity and normal osteoblastiCactivity
Pagetâs disease is a remodeling disease in which there is marked bone resorption by the osteoclast. The osteoblasts repair the bone in a mosaiCpattern with thickened trabeculae and cement or remodeling lines. There is both increased osteoclastiCactivity and increased bone formation by the osteoblast.
Inadequate mineralization of newly formed bone is called osteomalacia. In children, there is decreased mineralization at the growth plate.
Osteoporosis refers to low bone mass and microarchitectural deterioration of bone. There are two types of osteoporosis:
High turnover osteoporosis is increased osteoclastiCactivity and normal osteoblastiCactivity. In high turnover, the osteoclasts resorb large amounts of bone and the osteoblasts are unable to replace the bone. One finds markers for high levels of bone resorption and bone formation in the serum and the urine.
Low turnover osteoporosis is normal osteoclastiCactivity with decreased osteoblastiCactivity. In low turnover, the osteoclastiCactivity is at the normal rate; however, there is insufficient osteoblastiCactivity to fill in the osteoclastiCresorption cavities. The markers for osteoclastiCresorption are normal and the markers for bone formation are decreased.
Correct Answer: Increased osteoclastiCactivity and increased bone formation
736. (1911) Q2-2321:
Which of the following laboratory studies evaluates amounts of bone resorption:
1) Serum alkaline phosphatase
3) Gamma-glutamyl transpeptidase
2) Aspartate aminotransferase and alanine aminotransferase
5) Urine N-telopeptide, pyridinoline, and deoxypyridinoline
4) Osteocalcin
Bone resorption is assessed by measuring the products of bone remodeling. N-telopeptide, pyridinoline, and deoxypyridinoline are collagen cross-link products that are released during bone turnover. These collagen cross-links can be measured in the urine. A new marker can be measured in the serum and is called carboxy terminal collagen cross-links (CrossLaps).
Bone formation is assessed with serum alkaline phosphastase and osteocalcin.
Liver function tests include aspartate aminotransferase, alanine aminotransferase, and gamma-glutamyl transpeptidase.Correct
Answer: Urine N-telopeptide, pyridinoline, and deoxypyridinoline
737. (1912) Q2-2322:
Pagetâs disease is common in all of the following bones except:
1) Humerus
3) Femur
2) Spine
5) Pelvis
4) Hands and feet
Key features of Pagetâs disease:
Remodeling disease caused by excessive osteoclastiCactivity
Rarely diagnosed in patients younger than 40 years of age; most patients diagnosed after age 50
Most common sites include pelvis, femur, spine, skull, and tibia
Less common sites include clavicles, scapulae, ribs, and facial bones
Rarely found in the hands and feet
PagetiCbone
is more susceptible to fracture is less compact
is more vascular
tends to bow in weight bearing areas
GeographiCclustering (up to 4% in patients older than 55 years of age) England
Northern Europe North America Australia, New Zealand
Rare in Asia, China, Indonesia, Malaysia, and sub-Saharan Africa
Possibly a slow viral disease
RNA paramyxovirus (e.g., respiratory syncytial virus and measles) Correct Answer: Hands and feet
738. (1913) Q2-2323:
Pagetâs disease is common in all of the listed locations except:
1) England
3) Northern Europe
2) United States
5) Sub-Saharan Africa
4) Australia
Key features of Pagetâs disease
Remodeling disease caused by excessive osteoclastiCactivity
Rarely diagnosed in patients younger than 40 years of age; most patients diagnosed after age 50
Most common sites include pelvis, femur, spine, skull, and tibia
Less common sites include clavicles, scapulae, ribs, and facial bones
Rarely found in the hands and feet
PagetiCbone
is more susceptible to fracture is less compact
is more vascular
tends to bow in weight bearing areas
GeographiCclustering (up to 4% in patients older than 55 years of age) England
Northern Europe North America Australia, New Zealand
Rare in Asia, China, Indonesia, Malaysia, and sub-Saharan Africa
Possibly a slow viral disease
RNA paramyxovirus (e.g., respiratory syncytial virus and measles) Correct Answer: Sub-Saharan Africa
739. (1914) Q2-2324:
Which of the following occurs in active Pagetâs disease:
Marked bone resorption by the osteoclast and marked bone formation by the osteoblast occurs in active Pagetâs disease. The activities of the osteoclast and osteoblast are linked together
OsteocytiCosteolysis refers to which of the following processes:
1) Loss of bone through decreased bone formation
3) Removal of bone by osteoclasts
2) Mobilization of poorly crystallized calcium salts without effect on bone matrix
5) Osteocyte-mediated resorption of bone matrix
4) Loss of bone by osteoclasts in multiple myeloma
Osteocytes do not directly resorb bone. Osteocytes have receptors for parathyroid hormone, and they mobilize poorly crystallized calcium salts that surround them without resorbing the bone matrix. The osteocytes connect with each other through long, thin cytoplasmiCprocesses
■Correct Answer: Mobilization of poorly crystallized calcium salts without effect on bone matrix
741. (1916) Q2-2326:
Which of the following cells sends mechanical signals and transmits messages to other cells to increase bone remodeling in areas of maximum stress and strain:
1) Mast cells in bone marrow
3) Plasma cells
2) Osteoblasts
5) Osteocytes
4) Osteoclasts
Osteocytes respond to mechanical signals and transmit messages to other cells to increase bone remodeling
■Correct Answer: Osteocytes
742. (1917) Q2-2327:
Receptor activator of nuclear factor âkB (RANK) is located on which of the following cells:
1) Osteoblasts
3) Osteocytes
2) Plasma cells
5) Osteoclast precursors
4) Active osteoclasts
The activation of osteoclasts is a complex process. Surface receptors on the osteoclast precursor cells are called RANK. Receptor activator of nuclear factor âkB ligand (RANKL) is expressed on the surface of osteoblasts/stromal cells. The RANKL proteins leave the osteoblast and attach to the RANK receptor on the osteoclast precursor. Macrophage colony stimulating factor then facilitates the production of active osteoclasts from the osteoclast precursor.
Osteoprotegerin (OPG) is an inhibitor that is produced on the cell surface of hematopoietiCprecursor cells and mature osteoclasts. OPG binds to RANK receptor to inhibit the activation of osteoclasts
RANKL
Stimulates osteoclast differentiation and osteoclast activity
Inhibits osteoclast apoptosis
Induces hypercalcemia when injected
Loss of expression induces: Osteopetrosis
Tooth eruption defects
T and B cell differentiation defects
OPG
Soluble decoy receptor for RANKL Blocks osteoclast formation Reduces hypercalcemia
Overexpression induces osteopetrosis Loss of expression induces osteoporosis Prevents calcification of large arteries
Correct Answer: Osteoclast precursors
743. (1918) Q2-2328:
Osteoprotegerin (OPG) has which of the following functions or effects:
1) Inhibits osteoclast apoptosis
3) Activates osteoclast precursors
2) Inhibits osteoclast formation
5) Binds to receptor activator of nuclear factor âkB ligand (RANKL)
4) Induces hypercalcemia
The activation of osteoclasts is a complex process. Surface receptors on the osteoclast precursor cells are called RANK. Receptor activator of nuclear factor âkB ligand (RANKL) is expressed on the surface of osteoblasts/stromal cells. The RANKL proteins leave the osteoblast and attach to the RANK receptor on the osteoclast precursor. Macrophage colony stimulating factor then facilitates the production of active osteoclasts from the osteoclast precursor.
Osteoprotegerin (OPG) is an inhibitor that is produced on the cell surface of hematopoietiCprecursor cells and mature osteoclasts. OPG binds to RANK receptor to inhibit the activation of osteoclasts.
OPG
Soluble decoy receptor for RANKL Blocks osteoclast formation Reduces hypercalcemia
Overexpression induces osteopetrosis Loss of expression induces osteoporosis Prevents calcification of large arteries
Correct Answer: Inhibits osteoclast formation
744. (1919) Q2-2329:
Which of the following proteins or hormones assists in the transport of calcium in the kidney against chemical and electrical gradients:
1) Calcitonin
3) Osteoprotegerin
2) Calbindin
5) Vitamin D3
4) Parathyroid hormone
Calbindin, a vitamin D dependent and calcium binding protein, assists in the transport of calcium against chemical and electrical gradients. Most regulation calcium resorption in the kidney occurs in the distal convoluted segment
■Correct Answer: Calbindin
745. (1920) Q2-2330:
Which of the following is the rate-limiting step in the production of biologically active Vitamin D:
1) 25 hydroxylation in the liver
3) Conversion of 7 dehydrocholesterol to vitamin D3 in the skin
2) Absorption of calcium in the duodenum
5) Absorption of calcium in the jejunum
4) 1 hydroxylation in the kidney
The addition of a second hydroxyl group at the 1 position to 25 hydroxy vitamin D3 is the rate-limiting step in the formation of the active from of vitamin D3. Impaired renal function is common in older individuals
■Correct Answer: 1 hydroxylation in the kidney
746. (1921) Q2-2331:
Which of the following proteins or vitamins controls the amount of receptor activator of nuclear factor âkB ligand (RANKL)
produced by osteoblasts:
1) Parathyroid hormone
3) Thyroid hormone
2) 25 hydroxyvitamin D3
5) Calcitonin
4) 1,25 dihydroxyvitamin D3
The active from of vitamin D (1,25 dihydroxyvitamin D3) regulates the control of RANKL production by the osteoblast.
The activation of osteoclasts is a complex process. Surface receptors on the osteoclast precursor cells are called RANK. Receptor activator of nuclear factor âkB ligand (RANKL) is expressed on the surface of osteoblasts/stromal cells. The RANKL proteins leave the osteoblast and attach to the RANK receptor on the osteoclast precursor. Macrophage colony stimulating factor then facilitates the production of active osteoclasts from the osteoclast precursor
■Correct Answer: 1,25 dihydroxyvitamin D3
747. (1922) Q2-2332:
Which of the following proteins or vitamins influences growth plate chondrocyte maturation as a potent mitogen in the proliferative zone:
1) 1,25 dihydroxyvitamin D3
3) Insulin
2) 24,25 dihydroxyvitamin D3
5) Calcitonin
4) 1 hydroxyvitamin D3
Traditionally, 24,25 dihydroxyvitamin D3 was considered an inactive form of vitamin D. Recent studies suggest that 24,25 dihydroxyvitamin D3 influences growth plate chondrocyte maturation as a potent mitogen in the proliferative zone and may also contribute to bone formation and fracture repair
■Correct Answer: 24,25 dihydroxyvitamin D3
748. (1923) Q2-2333:
Which of the following cells has receptors for parathyroid hormone:
1) Osteocytes
3) Plasma cells
2) Osteoclasts
5) Osteoclast precursor cells
4) Osteoblasts
Osteoblasts have receptors for parathyroid hormone. Once stimulated, the cells release interleukin-6 (IL-6). IL-6 signals osteoclasts to resorb bone. The osteoblasts secrete neutral proteases that degrade the osteoid surface. Osteoclasts then attach to the bone surface and secrete acid proteases that degrade the bone matrix. Parathyroid hormone related protein increases osteoblast expression of receptor activator of nuclear factor âkB ligand (RANKL). RANKL binds to osteoclast precursor cells for the formation of active osteoclasts
■Correct Answer: Osteoblasts
749. (1924) Q2-2334:
Parathyroid hormone stimulates which of the following cells to secrete neutral protease that degrades the osteoid bone surface:
1) Osteoblasts
3) Osteoclasts
2) Mast cells
5) Osteoclast precursor cells
4) Osteocytes
Osteoblasts have receptors for parathyroid hormone. Osteoblasts have neutral proteases that begin the degradation of the osteoid matrix. Once stimulated, the cells release interleukin-6 (IL-6). IL-6 signals osteoclasts to resorb bone. The osteoblasts secrete neutral proteases that degrade the osteoid surface. Osteoclasts then attach to the bone surface and secrete acid proteases that degrade the bone matrix. Parathyroid hormone related protein increases osteoblast expression of receptor activator of nuclear factor âkB ligand (RANKL). RANKL binds to osteoclast precursor cells for the formation of active osteoclasts
■Correct Answer: Osteoblasts
750. (1925) Q2-2335:
Parathyroid hormone inhibits the production of:
1) Osteoprotegerin
3) Interleukin-6
2) 1,25 dihydroxyvitamin D3 production
5) Receptor activator of nuclear factor âkB ligand (RANKL)
4) Kidney 1 alpha-hydroxylase
Parathyroid hormone inhibits the production of osteoprotegerin. Osteoprotegerin is a decoy inhibitor of the receptor activator of nuclear factor âkB. Osteoprotegerin inhibits osteoclast activation
