Muscular System (Part 1) - Introduction and Muscles of the head

Summary

This module introduces the muscular system in dogs, focusing on skeletal muscles. It covers the head, trunk, thoracic limb, and pelvic limb muscles, detailing their actions and clinical importance. Key terms like tendons, aponeurosis, origin, insertion, belly, intrinsic, and extrinsic muscles are explained. The lecture discusses masticatory and facial expression muscles, noting the digastricus as the jaw opener and the temporalis as the strongest jaw closer. It also touches on muscles of the tongue and extraocular muscles, emphasizing their roles in facial expression and eye movement.

Takeaways

• 💪 Module 4 focuses on the muscular system, particularly the skeletal muscles of dogs.
• 📚 The module provides an overview of common muscles observed during dissection and their physiological and clinical importance.
• 📖 Topics are organized by body region to simulate the experience of actual muscle dissection.
• 🦴 Skeletal muscles are the bulk of muscles in the body and are categorized by their region: head, trunk, thoracic limb, and pelvic limb.
• 🔍 Important muscle terms include tendons, aponeurosis, origin, insertion, belly, intrinsic, and extrinsic muscles.
• 🦷 Masticatory muscles are powerful and associated with chewing, having attachments to the mandible.
• 😸 Mimetic muscles, also known as muscles of facial expression, move the skin and appendages of the face and ears.
• 👅 The tongue muscles and extraocular muscles are also part of the head muscles discussed.
• 🔑 The digastricus is the only muscle that opens the jaw, while others like the masseter and temporalis are involved in closing the jaw.
• 😏 Muscles of facial expression include the platysma, which draws the angle of the mouth caudally, and the boxinator, which draws the cheek inward.
• 👁️ Extraocular muscles enable eye movement and are divided into rectus, oblique, and retractor muscles.

Q & A

What is the primary function of the muscular system?

The primary function of the muscular system is to contract to produce movement.

What type of muscle is mainly focused on in this module?

This module mainly focuses on the skeletal muscle of the dog.

How is the muscular system organized in this module?

The muscular system is organized per region of the body: head, trunk, and limb regions.

What is the difference between tendons and aponeurosis?

Tendons are fibrous bands of collagen connecting muscles to bone, while aponeurosis are tendons associated with flat muscles.

What is the origin and insertion in the context of muscles?

The origin is the less movable attachment of a muscle, and the insertion is the more movable attachment.

What is the term for the thick fleshy central part of a muscle?

The thick fleshy central part of a muscle is called the belly.

How are intrinsic muscles different from extrinsic muscles?

Intrinsic muscles lie completely within one region of the body, having their origin and insertion within that region, whereas extrinsic muscles run from one region of the body to another.

What are the main groups of muscles in the head?

The main groups of muscles in the head are the masticatory muscles, facial expression muscles (mimetic muscles), tongue muscles, and extraocular muscles.

Which muscle is responsible for opening the jaw?

The digastricus, also known as the biventor, is the only muscle that opens the jaw.

What is the role of the masseter muscle?

The masseter muscle closes the jaw and lies lateral to the mandible.

What are the functions of the temporalis muscle?

The temporalis muscle closes the jaw and is the strongest muscle of the head in carnivores.

What are the main actions of the muscles of facial expression?

The muscles of facial expression move the skin and appendages of the face and head, such as the ears, to show reactions like aggression.

Outlines

00:00

🐾 Introduction to the Muscular System

This paragraph introduces Module 4, which focuses on the muscular system, specifically the skeletal muscles of dogs. It emphasizes the role of muscles in producing movement through contraction. The module is structured to cover muscles of the head, trunk, and limbs, aiming to help students identify different muscles and understand their main actions. Important muscle-related terms are introduced, such as tendons, aponeurosis, origin, insertion, belly, intrinsic, and extrinsic muscles. The paragraph also provides an overview of the muscles of the head, including masticatory muscles for chewing and facial expression muscles, or mimetic muscles, which control facial expressions and movements. Specific muscles like the digastricus, masseter, temporalis, and pterygoids are mentioned, each with their roles in jaw movement and facial expressions.

05:00

🗣️ Muscles of Facial Expression and the Head

This paragraph delves into the muscles responsible for facial expressions and other specific actions in the head region. It describes the platysma and buccinator muscles of the cheek, which are involved in mouth movement, and several muscles acting on the lips, such as the levator nasolabialis, orbicularis oris, and zygomaticus. The paragraph also covers the mentalis and maxillo nasolabialis muscles, which contribute to lip movement and nostril dilation. The frontalis muscle of the forehead and the extraocular muscles that control eye movement are also discussed. Additionally, the muscles of the tongue, both intrinsic and extrinsic, are briefly introduced, with a focus on their roles in tongue movement and shape alteration.

10:03

👅 Extrinsic Tongue Muscles and Module Conclusion

The final paragraph of the script discusses the extrinsic muscles of the tongue in more detail, including the styloglossus, genioglossus, and hyoglossus muscles, which are responsible for the tongue's movement and position. The styloglossus draws the tongue caudally, the genioglossus moves it rostrally and depresses it, while the hyoglossus attracts and depresses the tongue. The paragraph concludes with advice for students on how to better remember the muscles discussed, suggesting repetitive writing of the muscle names and organizing them based on their actions or locations. It also directs students to proceed to the next part of the module, which will cover the muscles of the neck, back, and abdomen.

Keywords

💡Muscular System

The muscular system is a body system comprised of muscles that contract to produce movement. In the context of the video, the muscular system is the primary focus, with an emphasis on the skeletal muscles of dogs. The script discusses how these muscles are essential for movement and how they can be categorized based on their location and function within the body.

💡Skeletal Muscle

Skeletal muscle is a type of muscle that is attached by tendons to bones and is responsible for voluntary movements. The script specifically focuses on the study of skeletal muscles in dogs, which are the bulk of muscles in the body and play a crucial role in producing movement and maintaining posture.

💡Tendons

Tendons are fibrous connective tissues that attach muscles to bones. As mentioned in the script, they are made of collagen and are essential for transmitting the force generated by muscle contractions to the bones to produce movement.

💡Aponeurosis

An aponeurosis is a flat, tendon-like tissue that connects flat muscles to bones. The script refers to it in the context of muscles that are associated with flat muscles, indicating its role in muscle attachment and function.

💡Origin and Insertion

In the script, 'origin' refers to the less movable attachment of a muscle, typically where the muscle is anchored, while 'insertion' is the more movable attachment, often where the muscle exerts force. These terms are critical for understanding how muscles produce movement by contracting and pulling on bones.

💡Belly

The belly of a muscle, as described in the script, is the thick, fleshy central part of the muscle. It is the primary contractile portion of the muscle, responsible for generating force during muscle contractions.

💡Intrinsic Muscle

Intrinsic muscles, as mentioned in the script, are muscles that lie completely within one region of the body, having both their origin and insertion within that region. This is in contrast to extrinsic muscles, which span across different body regions.

💡Masticatory Muscles

Masticatory muscles are those involved in the process of chewing. The script highlights these muscles as being powerful and having attachments to the mandible, with their contractions producing jaw movements associated with chewing.

💡Mimetic Muscles

Mimetic muscles, also known as muscles of facial expression, are responsible for moving the skin and appendages of the face and head. The script describes these muscles as being innervated by the facial nerve and includes examples such as the platysma and buccinator.

💡Extraocular Muscles

Extraocular muscles are the muscles that control the movement of the eye. The script explains that these muscles are striated and attached to the outside of the eyeball, enabling the eye to move in various directions.

💡Tongue Muscles

Tongue muscles, as discussed in the script, can be intrinsic or extrinsic. Intrinsic tongue muscles allow the tongue to change shape, while extrinsic muscles, such as the styloglossus, hyoglossus, and genioglossus, arise from outside the tongue and are responsible for moving the tongue as a whole.

Highlights

Module 4 focuses on the muscular system, particularly the skeletal muscles of dogs.

The module is divided into four lecture presentations based on body regions: head, trunk, and limb regions.

The muscular system is essential for movement, and this module provides an overview of common muscles observed during dissection.

Tendons and aponeurosis are key terms introduced, defining their roles in muscle attachment.

The origin and insertion of muscles are explained, detailing their functions in movement.

Intrinsic and extrinsic muscles are differentiated based on their location and function within the body.

The masticatory muscles are powerful and essential for the domestication of food.

The digastricus muscle is unique for being the only muscle that opens the jaw.

The masseter muscle is responsible for closing the jaw and is located lateral to the mandible.

The temporalis muscle is the strongest in the head and plays a crucial role in jaw movement.

The medial and lateral pterygoids are involved in both jaw closing and side-to-side movement.

Facial expression muscles, or mimetic muscles, are responsible for moving the skin and appendages of the face.

The platysma and buccinator muscles are key in facial expression, particularly around the mouth.

The levator nasolabialis and other muscles around the lips are essential for facial expressions and nostril dilation.

The orbicularis oris is a muscle that plays a role in closing the lips.

The frontalis muscle is the primary muscle of the forehead, affecting eyebrow movement.

Extraocular muscles are responsible for the movement of the eye in various directions.

The muscles of the tongue are categorized into intrinsic and extrinsic, affecting tongue movement and shape.

The styloglossus, hyoglossus, and genioglossus muscles are key extrinsic muscles of the tongue.

A tip for remembering muscle names is provided: repetition and organization based on action or location.

Transcripts

welcome to module 4. after finishing the

bones in the joints

we may now study the muscular system

muscles are organs that contract to

produce movement

this module is focused mainly on the

skeletal muscle of dog

although detailed myology is available

for study

this lecture will just give you an

overview of the common muscles observed

during dissection

with some information and their

physiological and basic clinical

importance

take note that the topics were arranged

per region of the body

as it is the best presentation in most

textbooks

as well as it stimulates the feeling of

actual muscle dissection

this module is divided into four lecture

presentations

and was based on the muscles of the head

the trunk

and the limb region at the end of this

module

you should be able to identify the

different muscles of the body

and identify the main action of each

muscle

the bulk of the muscles in the body is

skeletal muscle

here is the general overview of the

group of muscles that you will be

studying in this module

we will be discussing the muscles of the

head

the muscles of the trunk the muscles of

the thoracic limb

and finally the muscles of the pelvic

limb

but before we start let us discuss some

important terms that are necessary in

studying muscles

tendons are fibrous bones of collagen

connecting muscles to bone

aponeurosis are tendons associated with

flat muscles

the origin is the less movable

attachment

while the insertion is the more movable

attachment

belly is the thick fleshy central part

of a muscle

intrinsic muscle lie completely within

one region of the body

where they have their origin and

insertion in contrast to the extrinsic

muscle

which run from one region of the body to

another

aside from this there is a list of

muscle name derivation on the handout

provided

please read them so that you can have

additional idea

on how the muscles were named

let us begin with the muscles of the

head for easier familiarization

most anatomy references group the

musculature of the head

based on their role or main action

first we have the masticatory muscles

these muscles are powerful for

domestication of food

normally they have attachments to the

mandible and contractions produce

jaw movement associated with chewing

next are the muscles of facial

expression or the mimetic muscles

this group of muscles move the skin and

appendages of the face and the head

the ears for example for the animal to

show any reaction like

aggression other muscles of the head

includes

the tongue muscles and the extraocular

muscles of the eye

we will discuss each group in the next

slides

the first muscle of mastication to be

discussed is the digastricus or the

biventor

take note that this is the only muscle

that opens the jaw

this is being aided by the gravity the

rest of the masticatory muscles

open the jaw this muscle originates at

the jugular process of the occipital

bone

and inserts at the angle and ventral

surface of the mandible

next is the masseter it closes the jaw

and it lies lateral to the mandible it

is located

the deep masseteric fossa of the

mandible of the dog

this muscle originates at the

psychomatic arc and

inserts at the masseteric fossa on the

lateral surface of the mandible

the temporalis muscle closes the jaw as

well it is the strongest muscle of the

head in carnivores

it covers much of the dorsal and lateral

surface of the skull

to complete the muscles of mastication a

deeper muscle called medial and lateral

pterygoids

lie medial to the mandible here is a

lateral view of the head

with the ramus of the mandible removed

to show the pterygoid use muscle

they ate the temporalis and masseter in

closing the jaw

but they are also responsible for the

side to side movement

typical of herbivore mastication

the muscles of facial expression or the

pneumatic muscles

are generally thin cutaneous muscles

innervated by the facial nerve

they can be further subdivided into

muscles of the cheek

lips forehead and the eyelid

there are two muscles of the cheek

responsible for the dog's facial

expression

first is the platysma this is a

relatively well-developed sheet of

cutaneous muscle that draws

the angle of the mouth codally it

originates at the dorsal rafi

of the neck and inserts at the

commissure of the lips

the second one is the boxinator if we

remove the superficial structures

we can see the boxinators it is a thin

wide sheet of muscle that forms the

non-cutaneous substance of the chick

its contraction draws the chick inward

against the teeth

there are five known muscles that acts

on the lips

first is the levator nasolabialis from

the name itself

it elevates the nasolabial area it is

one of the most superficial muscle layer

covering the lateral surface of the

nasal bone and the maxilla

just deep to the skin contraction causes

the dilatation of the nostrils

and it raises the upper lip

next around the opening of the mouth is

the orbicularis oris

it lies deep in the platysma and levator

nasolabialis

its fibers run longitudinally and

contraction closes the lips

by drawing them together into the shape

of an

o zygomaticus or the smiling muscle

draws the angle of the mouth cuddly and

external ear cranially and

ventrally

mentalis is essentially a subdivision of

the ventral part of the boxinator

contractions defense the apical region

of the lower lip

finally the maxillo nasolabialis

is a specialization of the dorsal part

of the orbicularis oris

it is divided into two portions both of

which

lie deep to the levator nasolabials

the levator laby superioris is the more

dorsal portion

it traces the upper lip and dilates the

nostrils

while the caninus is the more ventral

portion

it is similar origin with the levator

laby superioris

but it inserts only into the upper lip

its contraction raises the upper lip

there is one major muscle of the

forehead and that is the

frontalis it is a thin sheet of muscle

overlying the temporalis muscle its

contraction

draws the scutular cartilage forward and

raises the eyebrow

there are five muscles known to act on

the eyelids

first is the orbicularis oculi it

surrounds the palpebral fissure

and contraction closes the said fissure

the retractor anguli oculi lateralis

passes directly cuddly from the lateral

palpibral

angle to blend with the temporal fascia

it draws the lateral palpibral angle

caudally thereby assisting in the

closing of the eye

on the other hand the counterpart

levator anguli oculi medialis

passes directly from the medial

palpebral angle

to attach to the frontal bone it raises

the upper lid

and erects the hair of the eyebrow

a dorsal view of the head musculature to

show the retractor anguli oculi

lateralis

and the levator anguli oculimidalis

as previously mentioned other muscles of

the head

include the extraocular muscles and the

muscles of the thumb

let us begin with the extraocular

muscles

these are the striated muscles that lie

within the orbit

associated with the globe of the eye

they are called

extraocular because they are attached to

the outside of the eyeball

this muscles enables the globe of the

eye to move

in the many directions of which it is

capable

there are eight extraocular muscles

which is divided into four rectus muscle

two oblique muscles and one retractor

muscle

the dorsal rectus elevates the globe

while the opposite

ventral rectus depresses the globe

the lateral rectus turns the globe

temporally or laterally

while the medial rectus turns the globe

nasally or

medially the dorsal oblique

in torts the globe or it rotates the 12

o'clock position

nasally while the ventral oblique

extorts the globe

or it rotates the 12 o'clock position

temporally

the remaining retractor bulbae retracts

the globe the muscles of the tongue can

be grouped

into intrinsic and extrinsic muscles

the intrinsic muscles of the tongue are

arranged in fascicles that run

longitudinally

transversely and vertically allowing the

tongue to change

shaped in multiple planes

the extrinsic muscles of the tongue are

those that arise from the outside of the

tongue

it includes the styloglosus hyaglosus

and the genioglossus the styloglossus

extends from the stylohyoid to the

tongue

it has three muscle heads that inserts

at the tongue at different level

it draws the tongue caudally

the genioglossus is a thin triangular

muscle

at the intermandibular space ventral to

the tongue

contraction draws the entire tongue

rostrally

it depresses the tongue and finally

the hyoglosus is located at the root of

the tongue

it attracts and depresses the tongue

that ends our presentation on this part

of the module

as a start it may be difficult for you

to remember

all the muscles discussed as a tip

it will be easy if you will write the

name repeatedly to be more familiar with

the term and the spelling

or as presented it will be easy to

remember if you organize

them based on their main action or

location at least

after that you are good to go you may

now proceed to part 2 of this module

which will be dealing with the muscles

of the neck

back and abdomen