Anatomy Quick Tips: Arms

Hey everyone, Sinix here.

It's time for another episode of
Anatomy Quick Tips,

the series that is here to give you
some useful observations

and help you feel more comfortable with

drawing people from imagination.

Today, we'll be talking about arms

and also dont be alarmed but

this all-arm video puts us near the end of this series,

only two more videos remain

regardless for now let's just focus on these upper appendages

This probably wont be the funniest video in this series or anything

but it will be definitely be the most humourous

so roll up your sleeves and lets get to work

starting out with structure

weve alreday covered both shoulders and hands

in other videos

so we just need to make sure we can bridge these things together

im sketching a quick front side and back few of the shoulders to start

seeing a shoulder and torso without the arm

always reminds me of a little lamb or something

but anyway were going to focus on

the skeletal breakdown of the arm first

of course we have a single major bone

in the upper arm

and two in the lower arm

connected at the elbow

but as i draw that, the first thing i actually want to point out

is that things arent in a perfect straight line

you can even take a moment

and try to see this yourself

just hold one arm out straight

and close your opposite eye

now do your best to look directly straight down

the barrel of that massive gun you call

your upper arm

if you line up your sight from shoulder to elbow

you'll notice the lower arm doesn't really

line up as much as you might've thought.

To get really good at drawing any organic forms,

it's important to try and identify these types of subtle offsets

as much as possible.

Anyway, let's get back to these bones.

The humerus is of course the bone

of the upper arm

meanwhile the lower arm has the ulna

which I would consider the primary lower arm bone

it's the one you would be hitting someone with

if you elbowed them

and then the radius which orginates

from the exterior side of the elbow

aka the side thats further away from your body

and always connects to the thumb-side of your hand

so we can do a bit of a rotational twisting

around the lower arm

hence the name radius

the last skeletal thing i want to mention

is the funny bone

this is just an extention of the humerus

which protrudes from the inner side of the elbow

closest to the thigh

it's called the funny bone

because of an exposed nerve ending next to it

that will send a shock up your arm

if you hit this part of the elbow against something

so if you ever see a chance to whack

your friends' funny bone with your pencil or stylus

its, you know, free comedy

alright i added some hands to these drawings

and i know this isnt the hands video

but since wrists and organic offsets are so important

lets do a quick recap at that connection anyway

now keep in mind by the time

the radius and ulna get to the wrist

theyll always be side by side

and therefore the lower arm connects in

a much flatter and wider way into the palm

and back of hand

and thinner from the side view of the hand

basic stuff but the fun part is

any time youre adding a hand to an arm

make sure to give it a bit of an offset

and step over toward the thumb/ radius side of things

similarly from the side view the hand should always

take a noticeable offsetting step toward the palm side

by the way when i say the word offset

it usually just means not lined up evenly with surrounding things

anyway always make sure the thumb side of the hand

feels more chunkier and substantial

than the pinky side of the palm

with all of these ideas in mind

you should be able to develop a quick shorthand

for getting from the arm into the hand

in fact you should be able to

quickly deduce everything about the bones

and orientation of the wrist without ever seeing

the thumbs or fingers or any interior information

so maybe see how quickly you can determine

where the radius and the ulna are

in any of these rough sketches im making

hopefully that seems easy enough

lets get back to structure and talk about the muscle side of things

were going to make it really easy

for our drawing purposes

and only focus on three muscle groups

the biceps are on the front of your upper arm

and allow you to curl up your arm

they insert under your shoulder muscles chest muscles on one end

and connect to the radius and tissue around the ulna on the other end

the triceps are on the back of your arm

and allow you to pull your arm straight

they also come out from under your shoulder muscles and similar back muscles

and connect to the back of the ulna

and yes the deltoids of course the shoulder muscles

but the third muscle that were going to be fixated on in this video

is going to be the brachioradialis

you must learn to love the brachioradialis

it will be a pivotal part of this video in more ways than one

these insertions points are important so keep them in mind

it connects from the lower back of the humerus

under the triceps and it wraps around a bit

over parts of the lower biceps and

connects to the radius on the other side

i will be exaggerating this muscle heavily throughout this video

so be aware of that strategic inflation

were going all in on the bre-bre (brachioradialis)

i think thats enough structure so

lets get into some drawing practice

a big theme in the land of arms will be

controlling our organic curves

so i guess i will do a quick recap on s-curves and c-curves

dont let the names throw you off too much

most of the s-curves and c-curves you'll be drawing

are going to be extremely subtle

just a whisper of curvature going on most of the time

and its good to practice that level of control

but an even more important thing to practise

is your ability to weight your cuves

weighting your curves means changing of

the harshness of the curvature through the line

so if the curve stays consistent from start to finish

that would be a weightless curve

you can have the curve be increasingly strong at the start

or the end of the line

to give it weight in a specific direction

this is very very important to practise

because we spend our entire childhoods writing

letters and shapes which curve and in a very balanced way

but the more you can break away from that

the more organic your drawings will be

so warm up with these often

alright lets get into those simplifications and reductions

or rather maybe mention another little side thing

sorry theres a lot of ways to think about arms

such as the chain

a common trick for approaching arms

is to imagine a giant linking chain

the idea being that since the upper arm is

wider from the side view than from the front view

and meanwhile the forearm is the opposite

it will generally create a nice little back and forth between wide and narrow

which is definitely good for aesthetic purposes

so you can use that as a little mental note when applicable

meanwhile to go back to what weve just talked about

with curve weight the most important mental note i fixate on

is usually just where to weight the curve for each part of the arm

on the bicep side of the upper arm

the curve weight is further toward the elbow

whereas on the back or tricep side of things

the curve weight is closer to the shoulder

the brachioradialis is definitely weighted toward the upper forearm

but its more rounded and gradual than the opposite

side of the forearm

all of these things relate to

the actual muscle bodies of each muscle group

the tricep being the most important one

to always remember because

the muscle bodies are located in the top half of the upper arm

okay so lets sum up the straight arm simplications

a bit more directly

back view of the arm pop forward minimal twisting

the upper arm might as well be a simple cylinder

with minimal tapering

but the lower arm is going to feel

closer to an upside down bowling pin

the important part is that

the exterior side of the brachioradialis

is going to not only curve outward more than the interior side

but also come up a bit higher than it

it should definitely feel like

it starts its s-curve above the elbow

if we raise the arm up out to the side

yes youll get a bit of the chain concept

but since youll probably not be drawing massive bodybuilders

it can become pretty minor

you do want to make sure that

youre thinking of weight and gravity though

obviously this gets a lot more extreme with age

but on any body type

you should still be using these ideas

to give you at least a little bit of subtle curve weight

another useful reference point to think about

comes from the shoulder muscle

the deltoid comes down to a bit

of a point on the exterior of the arm

while not exact this can still be used

as a good way to indicate a break

between the front bicep side of the arm

and the rare tricep side

especially when youre dealing with more complex poses

and off angle views

if i draw a quick arm over here on the left

from a slightly awkward angle

adding a deltoid and letting it point a line

towards the elbow can at least

help us visualise the tricep and bicep sides of the arm

this drawing looks weirdly off to you at first

thats good

the brachioradialis was not coming from the correct spot

lets first recall that the brachioradialis should come from

under the triceps and over the biceps

and using that line from the deltoid

we can visualise this insertion

much more clearly

moving along

some of these straight arms and elbows

might be looking a bit wonky

so lets briefly mention them

the most important part of simple "find the elbow"

will definitely come from seeing

the triceps and humerus all come together in a mass

that leads straight down through the elbow

and into the ulna

the funny bone and radius both become a bit

indented on a straight arm

so youll mostly see these

pockets of depth off to

both sides of the triceps and ulna

the forearm muscles pulling the forms back out

and really solidifying those crevices