Skeletal muscle anatomy introduction

Summary

The video script offers an introductory overview of the human body's skeletal muscles, emphasizing their variety and complexity. It discusses muscles of facial expression, mastication, and the role of muscles in posture and movement. The script delves into the muscles of the head, neck, back, and limbs, highlighting their functions in supporting the body, aiding respiration, and facilitating movement. It also touches on the importance of muscle fiber direction and the interplay between muscles and joints in the body's overall functionality.

Takeaways

• 📚 The human body has a vast number of muscles, far more than bones, which makes understanding them a complex task.
• 💪 Skeletal muscles are the focus of the script, as they are under conscious control and move the skeleton, unlike smooth muscles and cardiac muscles.
• 🤔 The muscles of facial expression are crucial for non-verbal communication and are distinct from other muscles due to their control and innervation.
• 🦷 Mastication muscles, like the masseter, are essential for chewing and are different from facial expression muscles in function and innervation.
• 🔬 The muscles of the neck, such as the sternocleidomastoid and trapezius, play a significant role in head movement and posture.
• 🏋️‍♂️ The trapezius muscle is multifunctional, affecting both the upper limb and back movements, and has fibers running in various directions.
• 🦴 Back muscles are layered and include superficial muscles that influence upper limb movement, intermediate muscles like erector spinae that support spine posture, and deep muscles that provide proprioception.
• 💨 The diaphragm, a skeletal muscle, plays a key role in respiration by changing the volume within the thorax to facilitate inhalation and exhalation.
• 🧘‍♀️ Abdominal muscles, including the rectus abdominis and the obliques, are vital for torso movement and maintaining intra-abdominal pressure.
• 🦵 The muscles of the upper limb, such as the deltoid and rotator cuff muscles, are essential for shoulder stability and arm movement.
• 👣 The muscles of the lower limb, particularly the quadriceps and hamstrings, are large and strong to support body weight and facilitate movement at the hip, knee, and ankle joints.

Q & A

What are the main types of muscles in the human body discussed in the script?

The script primarily discusses skeletal muscles, which are under voluntary control and move the skeleton. It also mentions smooth muscles within organs and blood vessels, and cardiac muscle, which are under autonomic control and not covered in detail in the script.

What is the role of the muscles of facial expression?

The muscles of facial expression are used for moving the lips, closing the eyes, and making various expressions. They are skeletal muscles that can be consciously controlled.

How does the script differentiate the muscles of mastication from the muscles of facial expression?

The muscles of mastication, such as the masseter, are involved in moving the jaw for chewing and are distinct from the muscles of facial expression not just in their role but also in their innervation.

What is the significance of the sternocleidomastoid muscle in the script?

The sternocleidomastoid muscle is significant because it is a superficial muscle involved in flexing the neck and bringing the chin towards the sternum when used bilaterally, and in rotation when used unilaterally.

What is the role of the trapezius muscle as described in the script?

The trapezius muscle is a superficial muscle of the back and also a muscle of the upper limb. It is involved in holding the head up, moving the scapula, and has different fiber directions allowing for various actions.

How does the script describe the function of the serratus anterior muscle?

The serratus anterior muscle runs from the ribs to the scapula and is involved in moving the scapula, including rotating and protracting it, as well as helping with breathing by pulling on the ribs.

What is the main function of the intercostal muscles according to the script?

The main function of the intercostal muscles is to form a pressure barrel, allowing the lungs to be moved by the muscles and bones, thus facilitating the change in volume inside the thorax for breathing.

How does the script explain the importance of the diaphragm?

The diaphragm is a skeletal muscle with a dome shape that can be consciously controlled. When contracted, it flattens, increasing the volume in the thorax and allowing the lungs to fill with air, playing a crucial role in respiration.

What is the role of the quadriceps femoris muscle group in the lower limb as described in the script?

The quadriceps femoris muscle group is responsible for extending the knee joint. The rectus femoris part of this group also crosses the hip joint, allowing it to flex the hip and extend the knee.

What are the hamstring muscles and what do they do according to the script?

The hamstring muscles are in the posterior compartment of the thigh and cross both the knee and hip joints. They can extend the hip by bringing the lower limb back when it's out in front, and flex the knee by bringing the heel up to the butt.

How does the script describe the importance of the gluteus maximus muscle?

The gluteus maximus is a large muscle that crosses the hip joint and is a powerful extensor of the hip. It plays a crucial role in standing up from a seated position by extending the hip joint.

Outlines

00:00

📚 Introduction to Skeletal Muscles

The script begins with an introduction to the complexity of the human body's muscles, which are more numerous and varied than bones. The narrator emphasizes the focus on skeletal muscles, which are under voluntary control and move the skeleton, as opposed to smooth muscles and cardiac muscles that are under autonomic control. The facial muscles, including those of mastication and expression, are highlighted for their distinct roles and innervation. The importance of posture and the muscles' role in supporting the head against gravity are discussed, with a note on the potential for muscle fatigue due to poor posture.

05:03

💪 Muscles of the Neck and Back

This paragraph delves into the muscles of the neck and back, starting with the splenius muscles that wrap around others and the scalene muscles that assist in breathing. The sternocleidomastoid and trapezius muscles are highlighted for their roles in neck flexion, rotation, and upper limb movement. The script explains the multi-layered nature of back muscles, including the superficial muscles involved in upper limb movement, the intermediate erector spinae that support the spine, and the deep muscles that provide proprioceptive feedback and potentially cause pain if misaligned.

10:03

🏃‍♂️ Muscles of the Torso and Limbs

The narrator describes the muscular structure of the torso, emphasizing the intercostal and abdominal muscles that form a protective barrier around internal organs and assist in breathing and torso movement. The pelvic floor muscles are mentioned as part of this muscular system. The limbs are introduced, with a focus on the scapula and its associated muscles like serratus anterior and latissimus dorsi, which are crucial for scapular movement and upper limb function. Pectoralis major and minor are also discussed for their roles in adduction and stabilization of the upper limb.

15:04

🤲 Upper Limb Muscles and Their Functions

This section provides a detailed overview of the upper limb muscles, starting with the deltoid muscle that suspends the limb and aids in shoulder movement. The rotator cuff muscles are introduced for their role in stabilizing the shoulder joint. The script continues with the muscles of the arm that facilitate elbow flexion and extension, wrist and finger movement, and the intricate actions of the hand that allow for fine dexterity and various forms of grip.

20:05

🚶‍♂️ Lower Limb Muscles and Their Actions

The paragraph focuses on the lower limb muscles, which are larger due to their role in supporting body weight during movement. The hip joint muscles, including the quadriceps femoris for knee extension and the hamstrings for hip extension and knee flexion, are detailed. The adductors and abductors of the hip are mentioned, along with the gluteal muscles that assist in standing up from a seated position. The muscles of the leg that cross the ankle joint and their roles in dorsiflexion, plantar flexion, inversion, and eversion are also discussed.

25:05

🌟 Overview of Skeletal Muscles and Their Importance

The final paragraph wraps up the introduction to the skeletal muscles, highlighting their variety, complexity, and the multitude of joints they cross. The importance of innovation and blood supply for muscle function is briefly mentioned. The script concludes with a light-hearted reference to the start of the academic year and an invitation to viewers to join for more detailed explorations of individual muscle groups in future videos.

Keywords

💡Skeletal Muscles

Skeletal muscles are the muscles attached to bones by tendons and are responsible for voluntary body movements. They are critical to the video's theme as the script discusses various skeletal muscles and their functions. For instance, the script mentions 'the muscles of facial expression' and 'the muscles of mastication' as examples of skeletal muscles that we can consciously control to make expressions and chew food, respectively.

💡Autonomic Control

Autonomic control refers to the involuntary regulation of certain bodily functions, such as the action of smooth muscles within organs and blood vessels or the cardiac muscle of the heart. In the script, autonomic control is contrasted with the voluntary control of skeletal muscles to highlight the different types of muscles in the body and how they operate independently of our conscious thoughts, unlike skeletal muscles.

💡Mastoid Process

The mastoid process is a bony projection behind the ear that serves as an attachment point for several muscles, including the sternocleidomastoid. The script uses the mastoid process as a reference to describe the location and function of the sternocleidomastoid muscle, which is involved in neck flexion and rotation.

💡Trapezius Muscle

The trapezius muscle is a large, superficial muscle of the back and upper limb that supports the shoulder blade and plays a role in head elevation and limb movement. The script describes the trapezius as having fibers running in different directions, allowing for various actions such as shrugging the shoulders and moving the scapula.

💡Serratus Posterior

The serratus posterior muscles are a group of muscles deep within the back that assist in respiratory movements by lifting the ribs. The script mentions these muscles in the context of breathing, indicating their role in inhalation by helping to expand the rib cage.

💡Erector Spinae

The erector spinae muscle group is a set of long muscles running along the spine, responsible for maintaining posture and aiding in spinal extension. In the script, the erector spinae is described as helping to lift the body from a bent position and stabilizing the spine.

💡Intercostal Muscles

Intercostal muscles are located between the ribs and are involved in the mechanics of breathing by moving the rib cage. The script explains that these muscles help form a pressure barrier that assists in inhalation and exhalation, highlighting their importance in respiratory function.

💡Diaphragm

The diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity and plays a crucial role in breathing. The script describes the diaphragm as a skeletal muscle that can be consciously controlled to flatten and facilitate inhalation, or relax to allow exhalation.

💡Pelvic Floor Muscles

Pelvic floor muscles are a group of muscles at the base of the pelvis that support the pelvic organs and assist in various functions, including urination and defecation. The script mentions these muscles as part of the body's muscular structure that can be consciously contracted, contributing to the overall stability and function of the pelvic region.

💡Quadriceps Femoris

The quadriceps femoris muscle group is a collection of four muscles at the front of the thigh responsible for extending the knee joint. The script specifically notes that the patella, a sesamoid bone in the quadriceps tendon, assists in this movement, emphasizing the muscle group's importance in activities like walking and jumping.

💡Hamstrings

The hamstrings are a group of muscles at the back of the thigh that bend the knee and extend the hip. The script describes the hamstrings as having dual functionality, crossing both the knee and hip joints, and being involved in actions such as sitting down and standing up.

Highlights

Introduction to the complex and numerous muscles of the human body, emphasizing the selectivity required due to their vast number.

Differentiation between skeletal muscles, which are under voluntary control, and smooth muscles and cardiac muscles, which are under autonomic control.

Explanation of the muscles of facial expression and their role in moving the lips, closing the eyes, and making expressions.

Discussion on the muscles of mastication, particularly the masseter, and their distinct innervation from facial expression muscles.

Importance of the neck muscles in supporting the head and maintaining posture, especially in the context of modern lifestyle and technology use.

Identification of the sternocleidomastoid and trapezius muscles as key players in neck and upper limb movements.

Description of the back muscles, emphasizing their layered structure and the role of the erector spinae in maintaining an upright posture.

Highlighting the role of the diaphragm as a skeletal muscle involved in respiration and its unique dome shape.

Overview of the abdominal muscles, including the external oblique, internal oblique, transversus abdominis, and rectus abdominis, and their functions in torso movement and support.

Introduction to the muscles of the pelvis and the importance of the pelvic floor muscles in supporting the body's core.

Discussion of the serratus anterior and latissimus dorsi muscles and their roles in scapula movement and upper limb support.

Explanation of the pectoralis major and minor muscles and their involvement in the movement of the upper limb and chest.

Description of the deltoid muscle's role in the suspension of the upper limb and its multi-penate structure.

Overview of the muscles involved in the movement of the forearm, wrist, and hand, emphasizing the importance of grip and dexterity.

Introduction to the muscles of the lower limb, focusing on their size and function in supporting body weight during movement.

Detailing the quadriceps femoris muscle group's role in knee extension and the rectus femoris's dual role at the hip and knee joints.

Explanation of the hamstring muscles' function in hip extension and knee flexion, and their importance in posture and movement.

Highlighting the gluteus maximus muscle's role as a powerful hip extensor, essential for rising from a seated position.

Description of the muscles involved in ankle movement, including the gastrocnemius and soleus for plantar flexion, and their importance in balance and stability.

Concluding remarks on the complexity and importance of the skeletal muscles, their interconnections, and their role in everyday activities.

Transcripts

hi

um I am going to introduce to you the

muscles of the body

this is a daunting task there are lots

of muscles in the body I've done some

introductory videos about the skeleton

hey there's only 206 bones and most of

those duplicated that's easy but there

are a lot of muscles

so I have to be selective in what I talk

about otherwise we'll be here for

literally dozens of hours

um so I'm going to we'll start at the

top head neck consider the trunk the

back and then look at the limbs think

about the joints think about how the

muscles are grouped the actions that

they do

um and try to be very introductory and

not get carried carried away

[Music]

we'll start up here with the head

um

there are muscles of the scalp

but these are the muscles of facial

expression that you use for moving your

lips and closing your eyes and making

Expressions here these are all skeletal

muscles that you can control and that's

an important thing while I'm introducing

the muscles of the body I'm introducing

the skeletal muscles the the the muscles

that we can think about moving and move

muscles that move the skeleton there are

other muscles there are smooth muscle

within organs and blood vessels and what

have you which I'm not going to talk

about which we don't think about that we

can't control they're under autonomic

control and the muscle of the heart the

cardiac muscle that's also under

autonomic control so we're thinking

about skeletal muscle

um the other muscles of the face are the

muscles of mastication this is masseter

here

these move the jaw

in different directions so that we can

chew uh they're distinct from the

muscles of facial expression not just

because of their role but also their

innervation

we actually have some

fairly good muscles that can move the

ear

but you need to practice quite a lot to

be able to move your ear but you can do

it now as we move around posteriorly

because we are upright bipedal animals

this has all evolved quite differently

to other animals and a lot of the

muscles here are important in keeping

our

well keeping our head up so we can gaze

forward

um with modern living satter computers

if you have a bad posture the head's a

very very heavy thing so these muscles

are quite strong in holding the head up

so if we have bad posture if we're

looking down a lot or in an awkward

position these muscles can get fatigued

overused and very tired so there are a

number of muscles under here and the

other thing about muscles is that we

need to consider what joints they cross

when we think about what actions they

might perform and some of these so these

um these muscles of the neck up here

we'll consider when we look at the

muscles of the back in a moment there

are also some splenius muscles splenius

means bandage they wrap around the other

muscles but there are also muscles of

the neck like these scalene muscles here

that run between the vertebrae and the

ribs

so they can lift up the ribs when you

take a deep breath

you'll feel these muscles Contracting

your neck as they're helping lift the

rib cage up and helping you inhale there

are two muscles of the neck that I would

like to point out though this one here

is sternocleidomastoid

this is the mastoid process here

posterior to the ear this is the

clavicle that's the clydo bit and the

sternum is here so sternocleidomastoid

it's a superficial muscle it's very

prominent it stands out it's involved in

if you've used if you use both sides

together

you Flex the neck you bring the chin

towards the sternum if you use them

individually then they're involved in

rotation the other big muscle is this

one here trapezius

now trapezius so here we can see

trapezius here it's been removed but if

you had the two trapezius muscles it

would make a trapezium shape now

trapezius is a very interesting muscle

it's a superficial muscle of the back

but it's also a muscle of the Upper Limb

um so this is the back it's superficial

it's covering the other muscles of the

back it runs up to the neck so it's

important in holding the head up it runs

out to this bone here this is the

scapula and to the clavicle so it's

involved in moving the scapula now the

scapula's job is to support the Upper

Limb so if we have a muscle that moves

the scapula then

it's moving supporting stabilizing the

Upper Limb it has a roll in the Upper

Limb and then it also runs down here to

the back and we have different fibers

running in different directions and

we'll see this in a number of muscles

some muscles are very straightforward

and they're just long things and they

contract in one axis and that's it the

sun muscles have fibers running in

different directions so different parts

of a muscle can contract independently

of the other parts and cause different

actions

uh so that's trapezius these are the

deeper muscles of the back here

hmm the back

we have many vertebral bones

forming the vertebral column the back

each one of those vertebrae can move

relative to the next vertebrae and we

join up all those little movements and

we can make quite big movements and

there are multiple layers of back

muscles so they're very superficial

muscles of the back

are actually involved as I say in the

Upper Limb look here if you take

trapezius off you can see the rhomboids

the rhomboids link the scapula to the

vertebrae so they can you can squeeze

your shoulder blades together you can

retract your scapulae with your rhomboid

muscles we have muscles here running

from the vertebrae to the ribs so

they're involved in moving the ribs

helping you push air out there's a this

is serratus posterior inferior there's

another deep set deep to these guys up

here which is serratus posterior

Superior

um which lift the ribs up so these

muscles are either

lifting the ribs and helping you bring

air in or

pulling the ribs down and helping you

push air out

so we have muscles that remove the ribs

relative to the vertebrae and then we

have this band of muscle here this this

intermediate layer and this is the

erector spiny muscle group you can

probably palpate this on your own back

erector spiny so this erects the spine

so if you're bent over these bands of

muscle help lift you back up again and

whilst that is a group of muscles it has

individual muscles or muscle bands

running from different parts of the back

to other parts of the back of the the

ribs and other parts of the back so it

gets broken up into muscles of many many

many different names

and then and this extends up into the

neck and then when you take off that

intermediate group of muscles you find

the Deep muscles and there are muscles

in between the vertebrae there are deep

muscles and deeper muscles and very very

deep muscles and lots of little muscles

there are lots of muscles in the back

and the deeper muscles are very small

they run between vertebrae and they

probably have a more proprioceptive role

sensing where each vertebra is relative

to the other vertebra and giving you

um giving your brain information about

that and maybe giving you pain if the

vertebra is being pulled inappropriately

and causing you to stop moving your back

and lie on a firm surface but it's these

larger muscles here these larger

superficial muscles that are probably

moving the back and also oh yeah

these muscles

the trunk

is made out of muscles and Bone but

muscles

so

um if you want to make a nice strong

container to keep all your organs in

muscles are pretty good building block

in the thorax we see the ribs and we see

layers of muscle in between the

intercostal muscles and the main

function here sure those intercostal

muscles can pull on the ribs and move

them but the main purpose of those

intercostal muscles is to form a

pressure Barrel a wall so that the lungs

inside can be moved by the muscles and

the bones you can change the volume

inside the thorax and if you increase

the volume inside the thorax you

decrease the pressure

air is drawn in through the Airways and

if you

decrease the volume inside the thorax

you push the air out and what we can't

see here if I took this off you'd find

the diaphragm so the diaphragm is also a

skeletal muscle and it's a dome inside

here do I want to take

there it is here's the diaphragm this

Dome up here

and this is a skeletal muscle you can

choose to control it and if you contract

it it flattens it pulls down all this

squishy stuff gets pushed out but the

volume here increases and the lungs

filled with air so the diaphragm is also

a skeletal muscle

and as we continue

inferior to the ribs and down to the

pelvis that's all covered with muscle

so the body wall is made up of mostly

three layers of muscle we have three

layers of intercostal muscle

three layers of abdominal muscle out

here you see how these fibers are

running in this direction we have the

external oblique muscles and then deep

to that we have the internal oblique

muscles their fibers are running in the

opposite direction and then deep to that

you have a third layer of muscle

transversus abdominis whose muscle

fibers run in that direction run

transversely and then in the midline we

also have the six pack we have rectus

abdominis running from the pelvis up to

the sternum and the the inferior ribs

here

[Music]

um

and when I said that

the big muscles move the back well

these are big strong muscles and these

the directions the muscle fibers run in

means that you can move your torso right

if you're moving your torso you're

moving your vertebrae so the abdominal

muscle wall is important at holding your

viscera in at resisting the

intra-abdominal and intrathoracic

pressure changes and also in movement of

the Torso

um down in the pelvis there is a pelvic

floor so

um the levator A9 muscle group and then

also support all of this inferiorly with

the pelvic floor muscles also skeletal

muscles you can

you can contract your pelvic floor right

you can choose to do that so it's glutal

muscle

um

now that's most of the Torso muscles but

now we can see the the limbs are hanging

from this

we mentioned the scapula back here

let me go this way around I take the arm

off

you can see

this muscle here

this is a it has a serrated appearance

this muscle because it has lots of slips

of muscle attaching to the ribs and this

is serratus anterior

goes along with this serratus posterior

muscle now serratus anterior is a big

beefy muscle running from the ribs

to the scapula so it's also involved in

moving the scapula rotating the scapula

protracting the scapula around the body

wall

but also it can pull on the ribs it's a

big muscle that can pull on the ribs and

help you breathe if you hold on to

something if you fix these bones in

place with your Upper Limb

big muscle here latissimus dorsi

so this big it's a back muscle runs

around laterally it's coming from fascia

and bones and vertebrae here and it runs

around to the humerus and this is the um

the climber's muscle this is the

swinging around in trees muscle this is

the muscle that lets you do a pull-up

it's so big because you can lift your

body weight with the pair of these

working together if you're really strong

you can do a one arm pull-up then you

just need one of them but not many

people can do that latissimus dorsi so

you can see how we've got muscles of the

back which are very much muscles of the

Upper Limb

serratus anterior latissimus dorsi if I

put the arm back on

okay

um here's pectoralis major

so this is a major bustle of the chest

but it's actually a muscle of the Upper

Limb it's running from sternum

clavicle out to the humerus this is a

muscle that's gonna

um well

see we get into the weeds already

the pectoralis major can

adduct the humerus and rotate the

humerus that's another thing we need to

think about with bones when we have like

a ball and socket joint like we have at

the glenohumeral Joint the humerus can

rotate

right

um and the way the muscles attached to

the bone will determine whether they can

take part in that rotation and how they

might take apart pectoralis major take

that off and you see pectoralis minor

running from the ribs up to the tip of

the shoulder

um so if trapezius you can use to shrug

your shoulders pectoralis minor you can

use to pull the tip of your shoulders

back down again

talking of trapezius

see we keep coming back to some of these

major muscles but

um here's trapezius you see how these

fibers are running from the axial

skeleton from that vertebral column out

to

the scapula and the clavicle and then we

have this muscle this is the deltoid

muscle look it's got lots of groups of

fibers running in slightly different

directions it's a multi-penate muscle

and then the humerus the lower limb

is attached to the deltoid muscle and

what we've got is we've got the

suspensory arrangement then the limbs

are quite heavy the Upper Limb is is a

heavy thing

so the weight of the limb is suspended

largely through the deltoid muscle there

are other muscles involved up to this

bony points and then the weight is

transferred through trapezius up to the

axial skeleton can you see that that

suspension Arrangement so the deltoid

muscle will move you know it'll

um abduct uh Flex extend the humerus of

the glenohumeral joint but his other big

job is actually holding that joint in

there together when you're carrying

something heavy it's holding that Upper

Limb

into the scapula

deep to all of that if you take deltoid

off well actually there's deltoid there

but you have um the rotator cuff muscles

so a smaller deeper muscles running from

the scapula to the humerus helping us

rotate the humerus but also helping hold

that joint together hoping helping

stabilize The Joint when we do things

like this when we stick our arm out when

we do these movements that we take for

granted

um there's deltoid and then of course we

move out to

uh the Upper Limb itself so if that's

the shoulder joint here's the elbow

joint and there's the wrist

on this side the anterior side of the

arm the brachium we have elbow flexors

like biceps

and then deep to that we have brachialis

and coracobrachialis and if they cross

the elbow joint then they can Flex the

elbow and they're also crossing the

shoulder joints they're also taking part

in movements of the humerus relative to

the shoulder joint

and then on the other side we have the

triceps muscle

so because the elbow is a hinge joint

the muscles on this side Flex the hinge

joint and the triceps brachii muscle on

this side extends the hinge joint and as

we move past the elbow everything gets a

lot more complicated

um we have muscles that are running to

the fingers that give us the power of

grip so most many of the muscles in the

anterior compartment of the forearm

forearm give us the power of grip

um but with the forearm we can also

pronate and supinate pronate and

supinates we have a number of muscles

involved with that including biceps

actually

and then we have muscles that are

running to the wrist so not only do we

Flex our fingers but we also Flex the

wrist

so we have flexors of the wrist the the

carpi muscles

and then when you get into the hand

these muscles are also important they're

smaller but these are the muscles that

give us the dexterity that we take for

granted

uh these little muscles in here the the

thumb has its own set of muscles the

thumb is very special very useful for us

with various forms of grip but those

other little movements of the hand of

the fingers that we use we're using the

muscles in the forearm but we're also

using the small muscles in the hand to

give us that fine dexterity and if we

have muscles on this side doing those

jobs then we have muscles on the

opposite side so these muscles will

extend the wrist extend the fingers

and so on so that's the Upper Limb oh

yeah

with the lower limb we have the hip

joint we have the knee joint and then

the ankle and the foot

um and these muscles are very big

they're big because they're supporting

most of the body weight when we're

walking when we're getting up from a

chair when we're going upstairs when

we're running jumping whatever

so these muscles are much larger and

when we walk with every step that we

take

we stand on one leg

so a number of these muscles have to

support us while we're stood on one foot

with every step that we take and keep

the pelvis level to give us that

efficient gait that we use

so these muscles are big so the hip

joint is a ball and socket joint now in

this anterior compartment of the thigh

the the big muscle bulk is the

quadriceps femoris muscle group and most

of that muscle only crosses the knee

joint this is the patella and the

patella is a sesame bone in the tendon

of that muscle and the tendon inserts

into the tibia here so this muscle

extends the knee joint which is a hinge

joint you go from a flexed knee to a

straight knee uh with the the rectus

with the quadriceps femoris muscle group

now one part of that this midline part

here the rectus femoris muscle also

crosses the hip which means that it can

act at the hip and at the knee so you

can Flex the hip that is raise your knee

towards your chest using rectus femoris

and quadriceps then extends the knee

from a bent position

we also see Sartorius here

and then there are some other bits and

Bobs now the medial compartment these

muscles in here these are the adductor

muscles there are a number of adductor

muscles the big one being Magnus the

lung one being longest the short one

being brevis

and those adduct the lower limb at the

hip joint and that is so if you are

adduct you bring the lower limb back to

the body if you abduct you take the

lower limb away from the body so the

abductors sorry the hip adductors bring

the legs back together gracilis is in

there as well

and if we turn around and we see the

hamstrings here this is the posterior

compartment we have a pair of muscles

here

semitendinosis and semimembranosus and

biceps femoris laterally these muscles

also cross the knee and the hip joint so

they can extend the hip joint

that is take the lower limb out behind

you or if your hip is flexed that is

your knee is out in front of you then

these muscles these hamstring muscles

can bring

the

lower limb back to an extended position

and they can also Flex the knee joint so

if these muscles shorten you'll bring

your heel up to your butt you'll Flex

the knee joint bend the knee joint so

those are the hamstrings and then we

have the gluteal region so this muscle

here is gluteus maximus big muscle and

it's running across the hip joint and

it's also a powerful extensor of the hip

so if you're sat in a chair and then you

stand up again

when you're sat in the chair your hip is

flexed and then when you stand up you'll

use gluteus maximus and the hamstrings

to extend

your hip joint and get up from that

chair

and then from the knee joint to the

ankle joint

we again have muscle compartments we

have this posterior compartment this

lateral compartment

and these anterior compartment and we're

moving the ankle joint so to lift the

toes towards your shin would be

dorsiflexion this is the dorsal foot the

dorsal surface to stand on your tiptoes

would be plantar flexion

and we can see that it's these muscles

back here these muscles of the posterior

compartment we can see gastrocnemius

deep to that we have Soleus so those are

plantar flexors that cross the ankle

joint and attach to the heel the

calcaneus bone here is sticking out to

give the mechanical advantage to the

ankle joint which is a little bit more

anterior

so these are big muscles that we can use

to stand on tiptoes to lift our entire

body weight to stabilize the foot when

we're walking to stabilize the foot on

uneven ground and uneven surfaces and

deep to those muscles we have muscles

that run around

the arches of the foot and run into the

sole of the foot which will

like the muscles of the forearm Flex the

toes Flex the big toe and help us with

our stability on the ground and also

stabilize the ankle joint

inversion is to bring your your soul so

it's facing inwards eversion is to bring

the soul of your foot so it's facing

outwards and those muscles that pass

immediately will help with inversion

that's the posterior compartment the

anterior compartment kind of does the

opposite so these muscles are running

across the ankle so they will help with

dorsiflexion bringing your toes to your

shins and also extending your toes with

your toes are flexed then the muscles in

the anterior compartment like extensor

digitorum longness

will help extend the toes and then also

um

muscles there are crossing the ankle

joint and help will help with inversion

and then that lateral compartment we

have the fibularis muscles because the

fibular bone is out here and those

fibularis muscles are running around the

ankle laterally and will help with

eversion all of those muscles are

working together

to help stabilize us

as we're stood over that foot

on a maybe less than perfect surface but

even if it is a flat surface you know

it's like you stand on on on one foot

one legged

right

a little bit wobbly it's

it's all of these muscles working

together to balance us and stabilize us

and then when we get into the foot

just like in the hand there are a lot of

small muscles which help with fine

movements of the toes which are maybe

less important to us than the fine

movements of the hand which are so

important for day-to-day living and then

in the sole of the foot there are layers

layers of muscles supporting all of this

oh okay

that was a lot of muscles

how's that that's an introduction to the

skeletal muscles of the human body there

are a lot they do a lot of things they

cross a lot of joints there's a lot of

detail in there the innovation's

important the blood supply is important

if you want to know more I have many

more videos in more detail about

individual Parts but I hope I hope

that was a useful warm-up speaking of

warm-ups

I don't know if you can hear but it

sounds like the uh

the freshest party is starting to warm

up students are coming back it's that

that time of the year where we

introduced students to new knowledge

right see you next week

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