🥇 MÚSCULOS de la EXPRESIÓN FACIAL y del CRÁNEO

Muscles of Facial Expression

Overview of Facial Muscles

• The video discusses the muscles of facial expression, categorized into four main groups: muscles of the skull, orbit, nose, and mouth. The neck muscles are mentioned but not covered in detail.

Characteristics of Facial Muscles

• All facial expression muscles share three key characteristics:

• Innervated by the same nerve (to be identified later).

• Originating from bone but inserting into skin or subcutaneous tissue.

• Variable development leading to different contraction forces.

Grouping of Facial Muscles

• The four primary muscle groups discussed include:

• Cutaneous Muscles of the Skull: Two muscles.

• Muscles Surrounding the Orbit: Three muscles.

• Muscles of the Nose: Four muscles.

• Muscles of the Mouth: Eleven muscles, allowing for a wide range of movements.

• A fifth group (neck muscles) is briefly mentioned with a focus on one specific muscle, the platysma.

Cutaneous Muscles of the Skull

• The cutaneous muscles are innervated by the seventh cranial nerve (facial nerve).

• Introduction to galea aponeurotica (epicranial aponeurosis), which connects two major skull muscles: occipital and frontal.

Occipital Muscle Function

• The occipital muscle originates from the occipital bone and mastoid process, inserting into galea aponeurotica.

• Its contraction pulls back on this aponeurosis, tightening it and affecting forehead skin tension.

Frontal Muscle Function

• The frontal muscle originates from galea aponeurotica and inserts into surrounding orbital and nasal structures.

• It elevates eyebrows and creates forehead wrinkles through its contractions.

Orbicularis Oculi Muscle

• This muscle has three portions:

• Circular portion around the orbital orifice.

• Palpebral portion located in eyelids.

• Lacrimal portion not visible in images shown.

Additional Eye-related Muscles

Anatomy of the Orbicularis Oculi and Related Muscles

Orbicularis Oculi Muscle Structure

• The orbicularis oculi muscle has a circular portion that originates at the medial palpebral ligament and adjacent bones of the nose and upper jaw, surrounding the orbital hole to insert into the external palpebral ligament.

• The palpebral portion features transverse fibers located in front of both upper and lower eyelids, originating medially at the internal palpebral ligament and inserting laterally into the external palpebral ligament.

• The lacrimal portion wraps around the lacrimal sac, originating from the posterior lacrimal crest, although it is not visible in this image.

Functionality of Orbicularis Oculi

• This muscle's primary function is to close the eye, acting as a palpebral sphincter that protects the eyeball from external agents while regulating light entry through the pupil into the retina.

Superciliary Muscle Overview

• The superciliary muscle originates from the frontal bone's superciliary arch and inserts at mid-level between eyebrow skin and galea aponeurotica; its contraction pulls forehead skin downwards.

• It acts as an antagonist to both frontal muscles (which open eyes by pulling forehead skin upward) and other muscles like orbicularis oculi.

Eyebrow Depressor Muscles

• The eyebrow depressor originates from nasal portions of frontal bone, inserting at middle third of eyebrows; it functions similarly to superciliary but also antagonizes frontal muscle actions.

Muscles of Nasal Region

• There are four key muscles in this region with both old anatomical names and new ones:

• Piriformis (also known as procerus)

• Transverse nasal muscle (simply called nasal muscle)

• Myrtiform (depressor of nasal septum)

• Dilator muscle for wing of nose

Pyramidal/Procerus Muscle Functions

• The pyramidal or procerus muscle originates from nasal bones' cartilages, intermingling with forehead skin; its function is to lower eyebrow region skin, acting antagonistically against frontal muscles.

Transverse Nose Muscle Insights

• This muscle surrounds grooves between nasal wings and facial skin; when contracted, it narrows nostrils—opposite action compared to dilator muscles which widen them.

Myrtiform Muscle Characteristics

• Also known as depressor of nasal septum, it originates in upper maxillary myrtiform fossa; upon contraction, it narrows nostrils while lowering nasal wings—acting synergistically with transverse nose muscle.

Dilator Muscle for Wing of Nose

Muscles of the Mouth and Nose

Overview of Facial Muscles

• The nasal wing muscle surrounds the nasal opening, contracting to dilate it, acting antagonistically to both the transverse muscle of the nose and the myrtiform muscle.

• There are 11 muscles in the mouth region on each side, making it the area with the most facial muscles. The discussion begins with the orbicularis oris.

Orbicularis Oris Muscle

• The orbicularis oris is a single unit that has two portions: one for the upper lip and another for the lower lip. It originates at both nasal corners and inserts into skin surrounding both lips. Its functions include acting as an oral sphincter and protruding lips forward.

• This powerful muscle intermingles with fibers from other mouth muscles, enhancing its functionality in lip movement.

Buccinator Muscle

• The buccinator is located deep to other facial muscles and is primarily a masticatory muscle rather than a facial expression muscle; it aids in chewing. Its origins include alveolar portions of both jaws and pterygomaxillary raphe.

• It increases intraoral pressure, essential for blowing air (as used by musicians) and helps expand the transverse diameter of the mouth when contracted. Additionally, it is perforated by structures like the stent duct for saliva secretion from parotid glands.

Levator Muscles

Common Levator Muscle

• This muscle elevates both the wing of the nose and upper lip, originating from upper jaw fibers and inserting at these respective locations to facilitate nasal opening during contraction.

Levator Proprio Superior Labii Muscle

• Originating from fibers intertwined with orbicularis oculi at upper jaw level, this muscle also serves to elevate the upper lip upon contraction.

Levator Anguli Oris Muscle

• Known as "the joker's muscle," it originates in canine fossa of upper jaw and inserts at buccal angle; its contraction raises mouth corners transversely, contributing to expressions like smiling or grinning.

Zygomatic Muscles

Zygomatic Minor

• Originating from zygomatic bone (malar bone), this minor zygomatic muscle retracts upwards laterally when contracted, affecting corner movements of both mouth and upper lip insertion points.

Zygomatic Major

• Similar to zygomatic minor but thicker; also originates from zygomatic bone and inserts at corner of mouth/upper lip while functioning similarly by retracting lip commissure upwards/outwards during contraction.

Risorius Muscle

• Further details about this specific risorius muscle were not provided within this segment but will likely follow in subsequent discussions regarding facial musculature.

Muscles of Facial Expression

The Risory Muscle

• The risory muscle is responsible for forming a smile, originating in the skin above the parotid gland and inserting at the angle of the mouth.

• It intertwines with the orbicularis oris, contributing to lip movement during smiling.

Depressor of the Angle of the Mouth

• This triangular muscle originates from the mandible and inserts into the angle of the mouth, functioning to lower the lip corner.

• Its action contrasts with muscles that raise or retract lips, often associated with expressions of sadness.

Quadratus Labii (Lower Lip Depressor)

• Also known as quadratus barbae, this muscle originates deep to the depressor of the angle and inserts at the lower lip.

• Its primary function is to lower the lip commissure, similar to other depressor muscles.

Mental Muscle

• Known as both beard tassel muscle and chin tassel, it originates at jaw level and inserts into chin skin.