Muscle 1: Axial Muscles of the Head, Neck, and Back

Created Feb. 7, 2024 by Dongho Kim

Muscle 1: Axial Muscles of the Head, Neck, and Back

Topics Covered

Introduction

Muscles of the head

Muscles of facial expression

Eye movement

Tongue

Muscles of the lower jaw

Muscles of the neck and back

Head movement

Anterior neck

Posterior neck and back

Introduction

Muscles of are discrete and made up of fascicules, or bundles of muscle fibers (cells). Muscles have a point of origin and a point of insertion, which are usually found on bone, but can also be found on skin (such as the muscle of facial expression) or on other muscle (such as pharyngeal muscles).

· Origin – the attachment point of the muscle that does not move during contraction, also called the proximal attachment

· Insertion – the attachment that moves during contraction, also called the distal attachment

· Action – the effects(s) the muscle has on a part of the body

Muscles often cross a joint; this is the joint that they act on. When a muscle contracts, it shortens, bringing the insertion closer to the origin. Muscle fiber orientation can tell the direction of muscle contraction; when muscle contracts it shortens along the long axis of the fiber. Discrete muscles can be made up of muscle fibers that are oriented in many different directions- such as the temporalis muscle or the trapezius muscle.