What is the role of the sarcoplasmic reticulum in muscle contraction?

Correct Answer: C

Rationale: The sarcoplasmic reticulum, a specialized endoplasmic reticulum in muscle cells, stores calcium ions and releases them into the cytoplasm upon a nerve signal. This calcium triggers contraction by binding to troponin. It doesn’t produce ATP or contract myofibrils, making 'Storing and releasing calcium ions' correct.

Correct Answer: A

Rationale: Bones are living tissues, not inert structures. They contain cells like osteocytes, osteoblasts, and osteoclasts that maintain bone structure, repair damage, and regulate mineral content. Blood vessels and nerves within bones also support their living functions, such as growth and remodeling, making 'True' the correct answer.

Correct Answer: B

Rationale: The human body has three muscle types: smooth (involuntary, in organs), cardiac (involuntary, in the heart), and skeletal (voluntary, attached to bones). 'Rough muscle' is not a recognized category in anatomy; it may confuse with muscle texture but isn’t a type, making 'rough muscle' the correct answer for what is NOT a muscle type.

Correct Answer: D

Rationale: A long bone includes the diaphysis (shaft), epiphysis (ends), and medullary cavity (marrow space). The perichondrium is a cartilage membrane, not part of mature long bones (which have a periosteum instead), making 'perichondrium' the correct answer for what is NOT included.

Correct Answer: B

Rationale: Hematopoiesis is the process of blood cell formation, occurring in red bone marrow. Endochondral and intramembranous ossification form bones, and remodeling reshapes them, making 'hematopoiesis' the correct answer.