Muscular System I (MANT011): Muscle Cell Types

• Ms NC. Mabunda presents Muscular System I (MANT011)

Types of Muscle Cells

• There are three types of muscle cells: cardiac, skeletal, and smooth

Cardiac Muscle Cells

• Found in the heart walls
• Controlled by the autonomic nervous system
• Have one central nucleus
• Striated and branched
• Movement is involuntary

Smooth Muscle Cells

• Located in the walls of hollow organs like blood vessels, the stomach, and the bladder uterus
• Controlled by the autonomic nervous system
• Have a single central nucleus
• Non-striated and spindle-shaped
• Involuntary movements

Skeletal Muscle Cells

• Attached to bone for skeletal system movement
• Controlled by the central nervous system
• Multinucleated
• Striated, long, and cylindrical in shape
• Muscles are under voluntary movement

Skeletal Muscle Shapes

• Skeletal muscles have different shapes adapted to their functions

Circular Muscles

• Circular in shape and usually surround openings like the mouth (Obicularis Oris) and eyes (Obicularis Oculi)

Convergent Muscles

• The origin is wider than the point of insertion like Pectoralis Major

Parallel Muscles

• Parallel muscles, strap muscles, have fibers running parallel to each other
• They are typically long muscles facilitating large movements
• Examples include the Sartorius and Sternocleidomastoid

Fusiform Muscles

• Spindle-shaped with the muscle belly wider than the origin and insertion
• Examples are Biceps Brachii and Psoas major

Pennate Muscles

• Have a high density of muscle fibers per unit, making them strong but easily fatigued
• They are divided into: Unipennate, Bipennate, and Multipennate

Unipennate

• Fibers arranged diagonally inserting onto a tendon like Extensor Digitorum

Bipennate

• Two rows of muscle fibers facing opposite diagonal directions with a central tendon, resembling a feather like Rectus Femoris

Multipennate

• Multiple rows of diagonal fibers with a central tendon branching into two or more tendons like the Deltoid muscle

Muscle Attachments

• Muscles attach to bone via tendons
• Each muscle typically has two attachments: an origin and an insertion

Origin

• Also known as the proximal attachment
• The attachment site remains stationary during contraction
• Found proximal in relation to the insertion

Insertion

• The attachment site that moves during muscle contraction
• Position is distal to the origin

Muscles of Facial Expression

• Responsible for facial movements and expressions
• They originate from the skull bones or fascia, inserting onto the skin
• Resulting in the muscles pulling on the skin and exerting effects
• Derived from the 2nd pharyngeal arch, they are innervated by branches of the Facial nerve (CNVII)
• Divided into three groups: Orbital, Nasal, and Oral

Occipitofrontalis - Orbital Group

• Has two bellies connected by the epicranial aponeurosis
• The frontal belly is the primary component involved in facial expression

Front Belly of Occipitofrontalis

• Actions include elevating eyebrows
• Wrinkling the skin of the forehead
• Protracts the scalp, which indicating surprise or curiosity

Front Belly Facial Expression

• Innervated by temporal branches of CNVII

Occipital Belly of Occipitofrontalis

• Its main action is retracting the scalp
• Increases the effectiveness of the frontal belly
• Innervated by the posterior auricular branches of CNVII

Obicularis Oculi - Orbital Group

• There are three parts: Palpebral part, Orbital part, and Lacrimal part

Palpebral part of Obicularis Oculi

• Gently closes the eyelids to keep the cornea from drying, such as when blinking or sleeping

Orbital part of Obicularis Oculi

• Tightly closes the eyelids protecting the eyeballs from glare and dust
• Used when winking or squinting

Lacrimal part of Obicularis Oculi

• Passes posterior to the lacrimal sac
• Draws the eyelids medially, aiding drainage of tears

Obicularis Oculi Innervation

• Innervated by the temporal and zygomatic branches of CNVII

Corrugator Supercilii - Orbital Group

• Actions of Corrugator Supercilii, draws the eyebrow medially and inferiorly
• Creates vertical wrinkles above the nose, demonstrating concern or worry
• Innervated by the temporal branches of CNVII

Procerus - Nasal Group

• Procerus main action is pulling the eyebrows downward
• Producing wrinkles over the nose
• Innervated by buccal branches of CNVII

Nasalis - Nasal Group

• Two parts work together to compress nasal cartilages, which flaring the nostrils
• Transverse part
• Alar part

Nasalis Action

• Compresses the nose
• Depresses medial end of the eyebrow
• Wrinkles skin over the dorsum of the nose
• Conveys disdain or dislike
• Innervated by buccal branches of CNVII

Depressor Septi Nasi - Nasal Group

• Depressor Septi Nasi assists the alar part of the nasalis
• Pulls the nose inferiorly, helping to open it
• Innervated by buccal branches of CNVII

Oral Group - Facial Expression

• Responsible for the movements and shape of the mouth and lips
• They are required in singing, whistling, communication, and facial mimics
• Performing their functions by elevating, retracting, and everting the upper lip
• Depressing, retracting, and everting the lower lip
• Controlling the orbicularis oris which is the sphincter around the mouth like the buccinator in the cheek

Orbicularis Oris - Oral Group

• Closes the oral fissure
• Compresses and protrudes the lips during kissing
• Resists distension when blowing
• Innervated by buccal branches of CNVII

Levator Labii Superioris Alaeque Nasi - Oral Group

• Dilates the nostril
• Elevates the upper lip and wing of the nose
• Innervated by buccal branches of CNVII

Levator Labii Superioris - Oral Group

• Dilates the mouth
• Elevates and everts the upper lip
• It Deepens the nasolabial sulcus, showing sadness
• Innervated by buccal branches of CNVII

Levator Anguli Oris - Oral Group

• Main Actions: Widens oral fissure and allows smiling by elevating the angle of the mouth and dilating the mouth
• Innervated by Buccal branches of CNVII

Zygomaticus Major - Oral Group

• Dilates the mouth
• Draws the angle of the mouth
• Smiling bilaterally, represents happiness
• Sneering unilaterally represents disdain
• Innervated by buccal branches of CNVII

Zygomaticus Minor - Oral Group

• Dilates the mouth
• Elevates and everts the upper lip
• Deepens the nasolabial sulcus, showing sadness
• Innervated by buccal branches of CNVII

Buccinator - Oral Group

• Compresses the cheeks against the teeth
• Resists distension when blowing or sucking
• Works with the tongue to keep food between the occlusal surfaces and out of the oral vestibule
• It is an assistant muscle of mastication that is involved with chewing
• Innervated by buccal branches of CNVII
• Pierced by the parotid duct to identify in a cadaver

Risorius - Oral Group

• Dilates the mouth by drawing back angle of mouth
• Innervated by the buccal branches of CNVII
• Action - cause one to show sadness

Depressor Anguli Oris - Oral Group

• Dilates the mouth, drawing back angle of mouth
• Causes someone to frown which indicates sadness
• Innervated by marginal mandibular branches of CNVII

Depressor Labii Inferioris - Oral Group

• Dilates the mouth
• Elevating and everting the upper lip
• Deepens nasolabial sulcus
• The actions all shows sadness
• Innervated by marginal mandibular of CNVII

Mentalis - Oral Group

• Elevates and protrudes the lower lip
• Elevates skin of the chin
• Showing doubt
• Innervated by marginal mandibular branches of CNVII

Platysma - Oral Group

• Depresses the mandible which is the lower jaw
• Tenses the skin of the lower face and neck
• Conveys tension and stress
• Innervated by cervical branches of CNVII

Muscles of Mastication

• A group of four muscles that all attach to the mandible
• They produce movements of the lower jaw at the temporomandibular joint (TMJ) to enable chewing and grinding
• Protrusion protraction, moves the mandible forwards
• Retraction pulls the mandible backwards
• The elevation elevates the mandible and closes the mouth
• Depression depresses the mandible and opens the mouth
• Lateral movements produces side-to-side movements of the mandible

Mastication Innervation and Origin

• All muscles of mastication develop from the first embryonic pharyngeal arch
• All innervated by a nerve of that arch, called the mandibular branch of the trigeminal nerve (CN V3)

Temporalis Muscle

• Fan-shaped to lie in the temporal fossa of the temporal bone
• Innervated by the mandibular nerve of CNV3 which includes the deep temporal nerves
• Its main actions elevates and retracts the mandible
• Mandible's Muscles

Masseter Muscle

• A quadrilateral muscle covering the lateral aspect of the ramus of the mandible
• Innervated by the mandibular nerve of trigeminal nerve CNV3 plus masseteric branches
• Elevates and protrudes the mandible

Medial Pterygoid Muscle

• Medial pterygoid muscle is a quadrangular muscle in the infratemporal fossa
• Has two heads
• Receives innervation from Mandibular nerve of Trigeminal nerve CNV3 the Nerve to medial pterygoid muscle
• Acts to Elevates and protrudes the mandible
• Produces smaller lateral chewing and grinding movements

Lateral Pterygoid Muscle

• A triangular muscle in the infratemporal fossa
• Has two heads
• Innervated by Mandibular nerve of the trigeminal nerve (CNV3) and the Lateral pterygoid nerve
• Protrudes and depresses the mandible
• Produces larger lateral chewing and grinding movements