Muscles are complex tissues in the human body that play a crucial role in movement, stability, and various bodily functions. Here's a basic overview of muscle structure:

1. Muscle Fibers: Muscles are made up of individual muscle fibers, also known as muscle cells. These long, cylindrical cells contain multiple nuclei and are packed with contractile proteins called myofilaments.

2. Myofibrils: Within each muscle fiber, there are numerous myofibrils, which are the structural units responsible for muscle contraction. Myofibrils are composed of repeating units called sarcomeres.

3. Sarcomeres: Sarcomeres are the smallest functional units of muscle tissue. They contain two types of filaments: thick filaments made of myosin and thin filaments made of actin. Contraction occurs as these filaments slide past each other.

4. Fascicles: Muscle fibers are grouped into bundles called fascicles. These fascicles are surrounded by connective tissue called perimysium.

5. Muscle Belly: The entire muscle, consisting of multiple fascicles, forms the visible bulk of the muscle known as the muscle belly.

6. Tendons: At each end of a muscle, the muscle fibers merge into a tough, fibrous connective tissue called tendons. Tendons attach muscles to bones, allowing for movement.

7. Blood Vessels and Nerves: Muscles are richly supplied with blood vessels to deliver oxygen and nutrients. They are also innervated by nerves, which transmit signals from the brain to control muscle contraction.

Overall, the intricate arrangement of muscle fibers and their contractile components enables the body to perform a wide range of movements and functions.