Related Experiment Video
Updated: Sep 27, 2025

Development of a Rabbit Chronic-Like Rotator Cuff Injury Model for Study of Fibrosis and Muscular Fatty Degeneration
Published on: March 31, 2023
A Different Pattern of Arrangement of the Risorius Muscle Fibers: A Case Report
Beatriz C Ferreira-Pileggi1, Alexandre R Freire2, Paulo R Botacin3
1Biosciences, Piracicaba Dental School, University of Campinas (UNICAMP), Piracicaba, BRA.
Abstract:
The risorius is a very thin muscle and is one of the superficial muscles of facial expression, which is reported as being inconstant, as it is absent in most people, and is a unique muscle; once it has no bony origin. The study aimed to report a different pattern of arrangement of the risorius muscle fibers. During a routine Anatomy class, a different pattern of arrangement of the risorius muscles fibers was found from the observation of an adult (around 40 years old) male cadaver hemiface (right side). After dissections, it was possible to note that the arrangement of the risorius muscle fibers on the surface of the masseteric fascia was formed in different arrangements formed in two bands. In conclusion, the risorius muscle fibers are not always easily distinguishable, and detailed knowledge of their different morphological arrangement is essential when planning and performing facial procedures.
More Related Videos
Related Concept Videos
Fascicle Arrangement in Skeletal Muscles
The four primary types of muscle based on fascicle arrangement are:
Classification of Skeletal Muscle Fibers
Slow-Twitch Muscle Fibers
Slow oxidative, muscle fibers appear red due to large numbers of capillaries and high levels of...
Gross Anatomy of Skeletal Muscles
Muscles of the Forearm that Move the Hand and Fingers
Anterior Compartment
The anterior compartment muscles originate from the humerus. They primarily function as flexors and are also known as flexor muscles. They typically insert on the carpals, metacarpals, and phalanges. The superficial layer includes the flexor carpi...
Muscles of the Shoulder
Anterior Thoracic Muscles
The anterior thoracic muscles include the serratus anterior, subclavius, and...
Assessment of Airway, Skin Color, and Use of Accessory Muscles
Introduction
The initial evaluation of a patient's respiratory system...

