A scientist is studying the anatomy and function of bone growth. He is able to create a cell line of osteocytes with a mutation that prevents the osteocytes from exchanging nutrients and waste products within neighboring lamellae. This mutation most likely affected which of the following cell structures?
ADynein
BGap junctions
CEndoplasmic reticulum
DPlasma membrane
EKinesin
An investigator is developing a drug for muscle spasms. The drug inactivates muscular contraction by blocking the site where calcium ions bind to regulate actin-myosin interaction. Which of the following is the most likely site of action of this drug?
ATroponin C
BMyosin-binding site
CAcetylcholine receptor
DRyanodine receptor
EMyosin head
A 72-year-old woman is brought to the emergency department because of severe pain in her left hip after a fall this morning. She has smoked one pack of cigarettes daily for 45 years. Her only medication is a vitamin D supplement. Physical examination shows that her left leg is externally rotated and appears shorter than her right leg. An x-ray of the pelvis shows a fracture of the neck of the left femur. Which of the following changes in bone architecture is the most likely underlying cause of this patient's symptoms?
ASubperiosteal bone resorption and cystic degeneration
BDeposition of lamellar bone interspersed with woven bone
CFormation of multiple sclerotic lesions in bony cortex
DLoss of cortical bone mass and thinning of trabeculae
EOvergrowth of cortical bone and reduced marrow space
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