Question at position 5 Place these structures of the skeletal muscle in order from largest to smallest: 1. fascicle 2. myofibril 3. muscle fiber (cell) 4.sarcomere B) 2, 4, 3, 1C) 1, 4, 3, 2A) 1, 3, 2, 4D) 3, 1, 2, 4,单项选择题
A
B)  2, 4, 3, 1
B
C)  1, 4, 3, 2
C
A)  1, 3, 2, 4
D
D)  3, 1, 2, 4,

Question

Question at position 5 Place these structures of the skeletal muscle in order from largest to smallest: 1. fascicle 2. myofibril 3. muscle fiber (cell) 4.sarcomere B) 2, 4, 3, 1C) 1, 4, 3, 2A) 1, 3, 2, 4D) 3, 1, 2, 4,单项选择题

A

B) 2, 4, 3, 1

B

C) 1, 4, 3, 2

C

A) 1, 3, 2, 4

D

D) 3, 1, 2, 4,

BlackTom AI · Accepted Answer

Skeletal muscle structural hierarchy: fascicles are bundles of muscle fibers (cells), each fiber contains many myofibrils, and each myofibril is composed of repeating sarcomeres.

1) Relevant knowledge points and concepts
- Organ-level to molecular-level organization in skeletal muscle: (largest) fascicle → muscle fiber (cell) → myofibril → sarcomere (smallest functional unit).
- A fascicle is a bundle of many muscle fibers, a muscle fiber is a single multinucleated cell, myofibrils are cylindrical contractile elements within the fiber, and sarcomeres are repeating contractile units along each myofibril.

2) Step-by-step reasoning process
- Compare each named structure by what it contains:
  - A fascicle (1) contains multiple muscle fibers (3).
  - A muscle fiber (3) contains many myofibrils (2).
  - A myofibril (2) is made up of sequential sarcomeres (4).
- Therefore ordering from largest to smallest follows the containment chain: fascicle → muscle fiber → myofibril → sarcomere.

3) Intermediate steps (explicit nesting)
- Start: Fascicle (bundle of fibers)
- Next: Muscle fiber (individual cell inside fascicle)
- Next: Myofibril (component of the fiber)
- Last: Sarcomere (repeating unit within a myofibril)

4) Why the correct answer is correct
- Choice A lists 1, 3, 2, 4, which exactly matches fascicle → muscle fiber → myofibril → sarcomere. This reflects anatomical arrangement and decreasing size from a bundled structure to the smallest contractile unit.

5) Why the other options are incorrect
- B (2, 4, 3, 1) orders myofibril before sarcomere and places the whole fascicle last; it reverses the correct size hierarchy.
- C (1, 4, 3, 2) places sarcomere larger than muscle fiber, which is incorrect because sarcomeres are subunits of myofibrils inside fibers.
- D (3, 1, 2, 4) places a muscle fiber larger than a fascicle; a fascicle is a bundle of fibers and therefore larger.

6) Conclusion
- The correct ordering from largest to smallest is 1, 3, 2, 4, which matches the provided answer A) 1, 3, 2, 4.

Question at position 5 Place these structures of the skeletal muscle in order from largest to smallest: 1. fascicle 2. myofibril 3. muscle fiber (cell) 4.sarcomere B) 2, 4, 3, 1C) 1, 4, 3, 2A) 1, 3, 2, 4D) 3, 1, 2, 4,单项选择题

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