Anatomy of the Face

Essential Anatomy of the Face

When considering the anatomy of the face for rejuvenation with injectables, it is helpful to think of it in its entirety as a three-dimensional structure that consists of five unique layers running superficial to deep. This is important to understand, so that we know which structures we are aiming to treat are placed.

The first layer, the outer most layer of the face is the skin, that comprises of both the epidermis and dermis. Beneath this you will find the subcutaneous layer that comprises of fatty tissue. The subcutaneous layer sits on top of the fascial layer that varies depending on the area of the face. For example, in the forehead the fascial layer contains the frontalis muscle, the temporal region contains the temporal parietal fascia and below the zygoma in the mid and lower, the fascia becomes the SMAS (superficial muscular aponeurotic system) which is fibro fatty and lymphatic fascial tissue that contains the muscles for facial expressions.

Underneath the SMAS layer is a layer that has traditionally been considered to be a loose areola tissue layer. We now understand that this deeper layer comprises of multiple discrete fat compartments and can be sometimes referred to as the deep fat layer. Beneath this is the periosteum of the facial skeleton.

Ligaments

There are a number of ligaments that run through these tissue plane, from deep to superficial. The true retaining ligament run from the periosteum through the SMAS layer to insert into the dermis. These include the orbital retaining ligament, the zygomatic cutaneous ligament and the mandibular ligament. A number of smaller ligaments are also present which can be described as condensations of fascia which run from the SMAS layer superior to the skin. The role of these multiple myocutaneous ligaments is to allow the transmission of movements of the muscles of facial expressions to the skin.

Arterial Blood Supply

The face contains two main arterial blood supplies. One arising from the external carotid artery system and one arising from the internal carotid artery system.

The external carotid artery gives rise to the facial artery which crosses the mandible, entering the face at the junction between the posterior one third and the anterior two thirds of the body of the mandible. This also corresponds to the anterior border of the masseter muscle and this can be palpated at this point as well as being identified by a facial artery notch that runs inferiorly along the edge of the mandible. This artery runs underneath the SMAS layer and traverses superiorly and medially towards the corner of the lip before giving rise to an inferior labial and superior labial artery, and then continuing in the deep nasal labial fat as the nasolabial artery. This continues along the side of the nose, as the angular artery, and gives rise to an alar branch to supply the skin over the ala of the nose and a lateral nasal branch to supply the skin of the lateral nose.

A further branch of the carotid artery is its terminal branch, the superficial temporal artery which divides into two main branches and supplies the skin of the temporal and forehead area.

The second main supply to the face arises from the internal carotid artery which gives rise via its various branches to the supraorbital and supratrochlear artery.

Muscles of the Face and Neck

Muscle Structure

Muscles are classified into three different types, which are skeletal, smooth and cardiac.

For the purpose of this course, we are mainly going to concentrate on Skeletal muscle, as smooth muscle is mainly found within hollow organs and cardiac muscle is found within the heart.

Skeletal muscles, also known as striated due to its appearance, or voluntary due to its action, are attached to bones and deal with movement. These muscles are made up of fine, thread like fibres of muscles, containing light and dark bands. Skeletal muscles can be made to contract and relax by voluntary will. They have striations due to the actin and myosin fibres and create movement when contracted. There are over 650 different types of muscles in the human body, making up nearly half of the body weight.

Muscles have the following properties:

Excitability – the muscle responds to stimuli
Contractibility – the muscle shortens due to a nerve impulse

Extensibility – the muscle can stretch and increase its length by half

Elasticity – the muscle will return to its normal length

Muscles consist mainly of muscle fibres which are held together by fibrous connective tissue, with numerous blood vessels and nerves penetrating through them. The muscle fibres are made up of muscle cells, which vary in length and are rod shaped. The fibres are called myofibrils and they get shorter (contract) in response to a nerve impulse. The protein strands then slide against each other when the muscle contracts.

Each muscle fibre has an individual wrapping of a fine connective tissue called endomysium, which are then wrapped into bundles called fascicule and are covered by the perimysium. This is what forms the muscle belly, and has its own covering called the fascia epimysium. The fascia acts as a “Clingfilm” around muscles, giving them support and also acts as a pathway for nerves, blood and lymph vessels.

Muscle Shapes

The bundles of fibres within muscles will determine the shape of the muscle. The commonest muscle fibre arrangements are:

Parallel fibres – these muscles have fibres that run parallel to each other in length and can sometimes be called strap muscles. These muscles have great endurance but may not be that strong due to their length. An example would be the Sternocleidomastoid (SCM).

Circular muscles – these muscles are usually circular in shape and an example would be the muscles surrounding the mouth and eye.

Convergent – this is where the muscle fibres converge to an attachment to a bone. The fibres are arranged to allow maximum force and can sometimes cross joints which have a large range of movement such as the Pectoralis Major.

Pennate – these are made up of short fibres, so the pull is short but also strong, though the muscle tires easily.

Fusiform – these are sometimes included within the parallel muscle group and are made up of spindle shaped fibres. A good example is the Biceps Brachii as the belly is wider than the origin and the insertion.

Muscle Movement

Muscles are only every able to contract or pull. This means they have to work in groups and even when carrying out an action, do not work alone. A joint, therefore has to have two or more muscles working together.
As a muscle contracts, the second muscle relaxes, and as this second muscle contracts, the first muscle relaxes. This is called Antagonistic action as they are pulling in the opposite direction to each other but without working against each other. One end of the muscle needs to be fixed, which is known as the origin and as that muscle contracts, the other end of the muscle moves towards the origin. The name given to the end of the muscle that moves towards the origin is called the insertion.

NamePositionAction
FrontalisUpper part of the craniumElevates eyebrows; draws the scalp forwards
CorrugatorInner corner of eyebrowsDraws eyebrows together (frowning)
ProcerusTop of nose between eyebrowsDepresses the eyebrows (forms wrinkles over the nose)
Orbicularis OculiSurrounds the eyeCloses the eye (blinking)
NasalisOver the front of noseCompresses nose (causing wrinkles)
TemporalisRuns downs the side of face towards jawAids chewing; closes mouth
MasseterRuns down and back to the angle of the jawLifts the jaw; gives strength for biting (clenches the teeth)
BuccinatorForms most of the cheek and gives it shapePuffs out cheeks when blowing; keeps food in mouth when chewing
RisoriusLower cheekPulls back angles of the mouth (smiling)
ZygomaticusRuns down the cheek towards the corner of the mouthPulls corner of the month upwards and sideways
Quadratus labii superiorusRuns upward from the upper lipLifts the upper lip; helps open the mouth
Orbicularis OrisSurrounds the lip and forms the mouthCloses the mouth; pushes lips forwards
MentalisForms the chinLifts the chin; moves the lower lip outwards
TriangularisCorner of the lower lip, extends over the chinPulls the corner of the chin down
PlatysmaFront of throatPulls down the lower jaw; angles the mouth
Sterno – mastoidEither side of the neckPulls head down to shoulders; rotates head to side; pulls chin onto chest

Skin Anatomy

  • The skin is the largest organ of the body.
  • Cells have an average life span of 19 – 34 days.
  • The average person is covered by 2 ½ square yards of skin that weighs around 9 pounds.
  • The average human grows about 1000 completely new outer skins during a lifetime.
  • Red blood cells wear out at a rate of 3 million every second, requiring the body to make over 200 billion new ones every day.
  • The body’s entire supply of red blood cells is completely renewed every four months.
  • Blood platelets last only 7-10 days in the body. They are one of the shortest-lived elements in the human body.

The Skin

Skin has two major tissue layers, The Epidermis, a thin layer of nonvascular tissue and the dermis, a dense layer of vascular connective tissue the subcutaneous layer (below the dermis) is a thick layer composed of fatty connective tissue that varies in thickness in each person.

A unique characteristic of the epidermis is its ability to regenerate tissue continuously. This process of shedding and renewing and renewing of epidermal tissue is called desquamation, taken from the Latin ‘desquamatous’ that means to scale off.

The outer layer of healthy skin is moist and approximately 10% water.

Intercellular cement is the lipid substance between the cells of the epidermis that keep the skin from dehydrating and helps to shield the skin from aggravating substances.

The layers of the epidermis have no blood vessels.

In order of their distance from the surface:

Stratum Corneum: Horny Layer: The outer layer of skin. This layer is the thickest of the epidermal layers and is exposed to the outer elements. The cells in this layer are dry and flat. This layer may have between 18-23 layers of flat dry cells that are cemented together by lipids, peptides, sebum and ceramides.

Stratum Lucidum: Is only present on the palms and soles of the feet. Thickness may vary from 0.5 to 0.8MM on the palms and soles of the feet and can be less than 0.1mm on the eyelids.

Stratum Granulosum: In this layer the lipids separate from the keratin (a non-living substance), ands cells lose a considerable amount of fat and moisture. These cells are approximately 80% keratin and less than 20% water.

Stratum Spinosum: This layer is several layers thick and flattens out as it rises upward. It is called the spiny or prickle cell layer due to the spiky appearance of the cells.

Stratum Germinativum: The basel layer is the only living layer of the epidermis where mitosis takes place. Mitosis is the process by which body cells divide to form two identical cells. This layer of skin does not have any blood vessels in it. Melanin is also in this layer.

Layers of the Dermis

Papillary Layer: This Layer of skin is directly below the epidermis. – THIS IS AS FAR AS THE HYALURON PEN TREATMENT WILL GO

Reticular Layer: This Layer contains the following:

  • Lymph Vessels.
  • Oil Glands.
  • Blood Vessels.
  • Hair Follicles.
  • Sweat Glands.
  • Fat Cells.
  • Arrector pili muscles.
  • Collagen

One Square inch of skin contains:

  • 9,500,000 Cells
  • 65 Hairs
  • 19-20 Yards of Blood Vessels
  • 13 Sensory apparatuses for cold
  • 19,500 Sensory cells at the ends of nerve fibres
  • 1,300 nerve endings to record pain
  • 650 Sweat glands
  • 95-100 Sebaceous glands
  • 78 sensory apparatuses for heat
  • 78 yards of nerves
  • 160-165 pressure apparatuses for the perception of tactile stimuli.

Skin Facts

  • The skin guards the body from injury and bacterial invasion.
  • The perceived colour of a person’s skin depends on the intensity of the state of contraction or dilation of the superficial vessels and on the extent of oxygenation of the blood.
  • Our skin has a limited capacity for absorption.
  • Freckles are an uneven distribution of melanin in the epidermis.
  • Skin is about 1mm thick on your eyelids, 3mm thick on the palms of your hands and the soles of your feet and about 2mm thick everywhere on the body.
  • The nerve endings are small and separate so that sensation is distributed not uniformly but in small areas. Individuals who are insensitive to pain have defective development of certain nerve structures.
  • When cells are injured, histamine (a chemical that dissolves protein) is released and these irritate the sensory nerve endings to cause varied degrees of discomfort.
  • When ice is applied to the skin the capillaries constrict, less blood and histamine flows and pain is alleviated.
  • When the skin is stroked firmly, the contractile cells of the vessels are mechanically stimulated, and capillary constriction produces immediate blanching. When these cells relax, the vessels dilate, and redness appears that flares to a small distance from the actual site of the stimulus. The flare depends on the integrity of nerve tissue and does not occur when the skin nerves have degenerated. If the stroke is injurious, histamine is released from damaged cells, water moves from the capillaries into the tissues and a swelling ensues. This is called a wheal and flare reaction or a hive.
  • Keratin in the basal layer is a protein that aids in protecting the skin against invasion.

The Function of the Skin

The skin has many functions, these include:

Secretion – The skin secretes sebum from the underlying sebaceous glands. This natural oil helps to keep the skin supple.

Heat Regulation – The body temperature is regulated through the skin. Sweating helps to cool the skin, while shivering helps to warm the body up.

Absorption – Substances can be absorbed through the skin which can be transported into the blood stream.

Protection – The skin acts as a protective barrier against germs and bacteria. The skin also contains Melanocytes which produce Melanin, and this helps protect the skin against UV radiation.

Excretion – The skin contains sweat glands which help to excrete excess waste and toxins out of the body.

Sensation – The skin contains thousands of nerve endings which act as sensors for pain. Heat or cold.

Vitamins – The skin helps make Vitamin D which Is created by a chemical reaction to Sunlight

Hyaluronic Acid (HA) fillers are compounded from a glycosaminoglycan polymer that occurs naturally within the body. Hyaluronic Acid fillers are manufactured by cross linking molecules into a 3-dimensional network. This cross-linking method is what determines the type and extent of the fillers viscosity and stability. Cross-linking of the molecule prevents oxidative stress and enzymatic degradation.

With so many fillers to choose from it is better to conceptualise and organise the choice of filler agents available into categories according to their physical properties and the duration of their effect. There are essentially three main categories of dermal fillers on the market.

These include temporary biodegradable agents that last less than 1 year, semi permanent biodegradable fillers that last 1-2 years and permanent fillers which are nonbiodegradable agents and last more than 2 years.

HOWEVER Hyaluron Pen Treatments are NON PERMANENT due to the layer of skin it hits (Papillary dermis) and last from 4-6 months, A semi perm product is a caHA which would hit the Reticular part of the dermis. 12-24 months.