Question

Which of the following is a fusiform muscle? (a) Cardiac muscle (b) Smooth muscle (c) Both (a) and (b) (d) Skeletal muscle

Short answer

(d) Skeletal muscle

Step-by-step solution

Define Fusiform Muscle

A fusiform muscle is a type of muscle that has a central belly and ends that taper off, forming a shape similar to a spindle. They are usually quite strong and can control a higher amount of movement.

Analyze the Options

Next, each option is analyzed based on the definition: (a) Cardiac muscle: These are found in the walls of the heart, and have a unique structure designed specifically for continuous contraction and relaxation. They do not have a fusiform structure. (b) Smooth muscle: These muscles are located in various systems of the body like the digestive and respiratory systems. They are not under voluntary control and have tapered ends, but the uniform, elongated shape is missing. They cannot be categorized as fusiform muscles. (d) Skeletal muscle: These muscles are directly involved in movement of the body and can be controlled voluntarily. They have a fusiform structure – a central belly that tapers off at both ends.

Choose Correct Option

From the analysis in Step 2, it is clear that the skeletal muscle fits the definition of a fusiform muscle. So, the correct choice is (d) Skeletal muscle.

Key concepts

Fusiform Muscle

Fusiform muscles are fascinating components of the muscular system. They are named for their spindle-like shape, where the muscle belly is broad and tapers at the ends, resembling a fusiform shape. This configuration allows them to generate force efficiently with a greater range of motion.

These muscles are conducive to producing quick and powerful movements. They are capable of contracting rapidly, making them well-suited for actions that require speed and agility. Typically, fusiform muscles are located where these characteristics can be most beneficial, such as in the biceps brachii, which allows us to flex and extend the forearm with agility and precision.

• Structure: Central belly, tapers at both ends.
• Function: Allows for a wide range of motion.
• Examples: Biceps brachii, hamstrings.

Cardiac Muscle

Cardiac muscles are one of the primary muscle types in our bodies, specifically designed to endure the tireless activity of pumping blood. Found exclusively in the walls of the heart, these muscles are tailored to withstand continuous contraction and relaxation cycles without fatiguing.

The unique structure of cardiac muscles includes interconnected fibers that facilitate the synchronized beating of the heart. These muscles are involuntary, meaning you can't control their action consciously. Their durability and rhythmic ability are thanks to their distinct cellular structure and the presence of intercalated discs, which help in rapid transmission of signals across heart fibers.

• Location: Walls of the heart.
• Function: Continuous and rhythmic contraction.
• Involuntary control.

Smooth Muscle

Smooth muscles are incredibly efficient muscles that play a significant role in various essential involuntary bodily functions. These muscles are found in various systems, including the digestive, respiratory, and circulatory systems.

Unlike skeletal muscles, smooth muscles do not have a striated appearance and are spindle-shaped. They can contract and relax slowly but with sustained force, which is crucial for managing processes like digestion, blood flow, and respiration. Since they are not under direct voluntary control, you can think of them as the constant, silent workers in your body.

• Location: Digestive tract, blood vessels.
• Function: Involuntary control of internal processes.
• Structure lacks striations, yet is powerful.

Skeletal Muscle

Skeletal muscles are the voluntary muscles that facilitate movement and posture. They are controlled consciously, allowing for deliberate actions like walking, running, and lifting. These muscles are connected to bones by tendons, playing a crucial role in the musculoskeletal system.

Skeletal muscles have a different structure compared to cardiac and smooth muscles. They are striated, meaning they have a banded appearance under a microscope, and are composed of long fibers. Interestingly, some skeletal muscles, such as the biceps, have a fusiform shape, which allows for detailed and extensive movements.

• Location: Attached to bones throughout the body.
• Function: Voluntary movement control.
• Structure: Striated and robust.