Flat muscle

A flat muscle is a type of skeletal muscle characterized by its broad, thin, sheet-like shape and parallel or slightly oblique muscle fibers. These muscles often attach to bones, fascia, or other muscles via aponeuroses—flat, fibrous tendons that distribute force over a wide area.

Anatomically, flat muscles are designed to generate tension across large surfaces rather than produce localized, powerful contractions. They are commonly found in the walls of the trunk, thorax, and neck, where they provide support, stability, and protection for underlying structures.

Function

Functionally, flat muscles play vital roles in:

• Enclosing and protecting body cavities (e.g., abdominal wall)

• Compressing contents of cavities during activities such as respiration, defecation, and childbirth

• Producing trunk movements such as flexion, extension, and rotation

Examples

• External and internal oblique, transversus abdominis (abdomen)

• Pectoralis major (chest)

• Trapezius and latissimus dorsi (shoulder region)

• Intercostal muscles (thoracic wall)