Muscular System (Part 1) - Introduction and Muscles of the head
Summary
TLDRThis 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
🐾 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.
🗣️ 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.
👅 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.
Mindmap
Keywords
💡Muscular System
💡Skeletal Muscle
💡Tendons
💡Aponeurosis
💡Origin and Insertion
💡Belly
💡Intrinsic Muscle
💡Masticatory Muscles
💡Mimetic Muscles
💡Extraocular Muscles
💡Tongue Muscles
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
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