The FacePictorial Atlas of Clinical Anatomy

Ralf J. Radlanski Karl H. Wesker

1 The face . . . . . . . . . . . . . . . . . . . . 1

1.1 Introduction . . . . . . . . . . . . . . . . . . . . 2

1.1.1 General remarks . . . . . . . . . . . . . . . . . . 2

1.1.2 Regions of the face . . . . . . . . . . . . . . . . 4

1.1.3 Morphometry and proportions of the face . . . . 6

1.2 The face in anterior view . . . . . . . . . . . . . . 18

1.2.1 Fat compartments of the face

in anterior view . . . . . . . . . . . . . . . . . . . 18

1.2.2 Muscles of the face in anterior view . . . . . . . . 25

1.2.3 Vascular and nerve supply of the face

in anterior view . . . . . . . . . . . . . . . . . . . 38

1.3 The face in lateral view . . . . . . . . . . . . . . . 54

1.3.1 Fat compartments of the face

in lateral view . . . . . . . . . . . . . . . . . . . . 54

1.3.2 Muscles of the face in lateral view . . . . . . . . . 62

1.3.3 Vascular and nerve supply of the face

in lateral view . . . . . . . . . . . . . . . . . . . . 78

1.4 The head in vertical view . . . . . . . . . . . . 106

1.5 The head in dorsal view . . . . . . . . . . . . . 116

1.6 The neck . . . . . . . . . . . . . . . . . . . . . 122

1.6.1 The neck in anterior view . . . . . . . . . . . . 123

1.6.2 The neck in lateral view . . . . . . . . . . . . . 128

1.6.3 The neck in dorsal view . . . . . . . . . . . . . 133

1.7 Facial expression . . . . . . . . . . . . . . . . . 136

1.8 The facial skeleton . . . . . . . . . . . . . . . . 148

1.9 Sectional anatomy . . . . . . . . . . . . . . . . 162

1.10 Schematic representations of pathways

in the face . . . . . . . . . . . . . . . . . . . . 172

2 The orbital region . . . . . . . . . . . . 180

2.1 Surface topography of the orbital region . . . . 182

2.2 Preseptal muscles and fat layers . . . . . . . . . 185

2.3 The orbital septum and the eyeball . . . . . . . 189

2.4 Vascular and nerve supply in the orbital region . . . 196

Contents

2.5 Vascular and nerve supply in the orbital region

in relation to the muscles . . . . . . . . . . . . 205

2.6 Sectional anatomy of the orbital region . . . . . 210

3 The nasal and midfacial region . . 216

3.1 Surface topography of the nasal region . . . . . 218

3.2 The nose in anterior view . . . . . . . . . . . . 222

3.3 The nose in lateral view . . . . . . . . . . . . . 230

3.4 The nose in caudal view . . . . . . . . . . . . . 244

3.5 The nasal cavity . . . . . . . . . . . . . . . . . 245

3.6 The sinuses . . . . . . . . . . . . . . . . . . . 258

4 The mouth . . . . . . . . . . . . . . . . . 262

4.1 Extraoral topography of the oral region . . . . . 264

4.2 Topographical anatomy of the oral region . . . . 265

4.3 Vascular and nerve supply of the oral region . . . 267

4.4 The oral cavity . . . . . . . . . . . . . . . . . . 278

4.5 Anatomy of the lips, teeth, periodontium

and alveolar bone in sections . . . . . . . . . . 283

4.6 The anterior oral vestibule . . . . . . . . . . . . 289

4.7 Anatomy in the area around the

mandibular ramus . . . . . . . . . . . . . . . . 290

4.8 The temporomandibular joint . . . . . . . . . . 303

4.9 Anatomy of the oral region in sections . . . . . 308

4.10 Pathways of odontogenic spread of infections . . 314

5 The ear . . . . . . . . . . . . . . . . . . . . 316

6 The skin and aging of the face . . . . 330

Appendix . . . . . . . . . . . . . . . . . . . . . 345

References . . . . . . . . . . . . . . . . . . . . . . . 347

Index . . . . . . . . . . . . . . . . . . . . . . . . . . 349

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Parietal region

Temporal region

Infratemporal region

Nasal region

Zygomatic region

Oral region

Parotideo-masseteric region

Mental region

Sternocleido-mastoid region

Lateralcervical region

Frontal region

Orbital region

Auricular region

Infraorbitalregion

Buccal region

Omotrachealtriangle

Posteriorcervical region

Nasal region

Zygomatic region

Infratemporal region

Orbital region

Frontal region

Infraorbital region

Oral region

Buccal region

Parotideomasseteric region

Mental region

Submental triangle

Submandibular triangle

Omotracheal triangle

Parietal region

Temporal region

Occipital region

Auricular region

Mastoid region

Retromandibular fossa

Sternocleidomastoid region

Posterior cervical region

Carotid triangle

Vertebra prominens (C7)

Lateral cervical region

Fig 1-3 Regions of head and neck in anterior view.Fig 1-4 Regions of head and neck in lateral view.

1.1.2 Regions of the face

The face

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Temporal region

Mastoid region

Parotideo-masseteric region

Sternocleido-mastoid region

Lateralcervical region

Auricular region

Parietal region

Occipital region

Posteriorcervical region

Vertebraprominens (C7)

Orbital region

Infraorbital region

Zygomatic region

Auricular region

Parotideomasseteric region

Submandibular triangle

Carotid triangle

Sternocleido-mastoid region

Lateral cervical region

Major supra-clavicular fossa

Oral region

Buccal region

Mental region

Submental triangle

Omotrachealtriangle

Jugular fossa

Minor supra-clavicular fossa

Fig 1-5 Regions of the neck and the face in anterior view.Fig 1-6 Regions of head and neck in dorsal view.

Introduction

5

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Gl Gl

Trg Or’ Or’Sn

Pg’

a b

Fig 1-20 The “Fotostat” assessment according to Schwarz (1936).

Fig 1-20 The German orthodontist A. M. Schwarz (1936) in-troduced a method to evaluate the sagittal relation between the upper and the lower face, which he called the “Fotostat” technique. For this, the profile and lateral views are mounted so that the measuring points tragus (Trg) and infraorbital point (Or’) are on a common horizontal line. Vertical lines are drawn from the glabella (Gl; line b) and from the infraorbital point (Or’; line a). The diagnosis of the sagittal position of the max-illa is made by the position of subnasal point (Sn) in relation to line (b). If the maxilla is anterior of this line, it is a prognathic face; if it is posterior then the face is retrognathic. An average face is observed when Sn is on line (b). The diagnosis of the po-sition of the mandible is made by the position of the soft tissue

pogonion (Pg’). The face is “balanced” when Pg’ is in the mid-dle between the two perpendicular lines (a) and (b). A retrog-nathic face is found when Pg’ is approaching or exceeding the orbital line (a). A prognathic face occurs when Pg’ approaches or exceeds line (b).

In this evaluation method, the jaw profile field lies between the vertical lines (a) and (b). In our model, however, both the critical reference points for the upper jaw (Sn) and for the man-dible (Pg’) are located well anterior to the glabella line (b). It would, therefore, be identified as a prognathic face with slight mandibular protusion based on this evaluation. Our model, however, is without any question esthetically flawless.

Fig 1-21 Common measurement points on the skull and the soft tissue in anterior view.

SOr: supraorbital pointOr: orbital point (orbitale)N: nasionSn: subnasaleMx: maxillare (palpable, deepest point in the molar region

at the transition of the maxilla to the zygomatic bone)M: Mastoid

Md: mandibulare (palpable alveolar process in the molar region)

Go: gonion (jaw angle point)Go’: jaw angle on the soft tissueMe: menton (chin prominence in the middle)Mer: menton on the right (the most inferior lateral point on

the anterior inferior border of the mandible, right)Mel: menton on the left (the most inferior lateral point on

the anterior inferior border of the mandible, left)Me’: soft tissue chin point

The face

14

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Or Or

N

SOr SOr

M M

Mx MxSn

MdMd

Me

GoGo

Mer Mel

Go’ Go’

Me’

Fig 1-21 Common measurement points on the skull and the soft tissue in anterior view.

Introduction

15

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Mental n. (CN V3Mental n. (CN V3Mental n. (CN V )

Buccinator

Temporal branches (CN VII)

Zygomaticofacial n.

Inferior palpebral branch(CN V2(CN V2(CN V )

Infraorbital n. (CN V2Infraorbital n. (CN V2Infraorbital n. (CN V )

Upper lateral cartilage

Buccal n. (CN V3Buccal n. (CN V3Buccal n. (CN V )

Superficial temporal a. and v.

Anterior nasal branch

Supraorbital n.,lateral branch

Medial branchof supraorbital n.

Supratrochlear n.

Infraorbital v.

Transverse facial a.

Infraorbital a.

Zygomaticofacial a. and v.

Facial a. and v.

Mental a.,mental branch ofinferior alveolar v.

Submental a. and v.

Parotid duct

Buccal a.

Anterior nasal a.

Supraorbital a. and v.

Supratrochlear a. and v.

Parietal branch(superficial temporal v.)

Fig 1-45 Deep arteries and veins (right half of the face), and deep nerves (left half of the face).

The face

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Fig 1-46 Some branches of the supratrochlear and supraor-bital arteries and veins run so close to the bone that they are covered by the corrugator supercilii muscle. Other branches of these vessels pass over the muscle in a cranial direction. The lateral and medial branches of the supraorbital and the supra-trochlear nerves run underneath, through and over the corru-gator supercilii muscle. The motor innervation is supplied by the anterior temporal branches of the facial nerve (CN VII).

The temporalis muscle is supplied by the deep temporal ar-teries and veins and also by the deep temporal nerve (from CN V3). It also receives innervation from temporal branches of the facial nerve.

The superficial temporal artery and vein and the main trunk of the temporal rami (from the facial nerve) run over the zygo-matic arch and, therefore, have been cut in this stage of prep-aration.

Vessels and nerves that emerge from the infraorbital foramen (artery, vein and infraorbital nerve) supply the region around the foramen and reach well into the eyelid (inferior palpebral rami) and also reach the nose muscles and the upper lip.

The facial artery and vein pass around the edge of the mandi-ble, anterior to the masseter muscle. They cross over the buc-cinator muscle medially and stretch obliquely in a multicurved pattern. They lie above the branches of the infraorbital artery and vein. Here, a pulse can be felt.

Buccal branches of the facial nerve supply the buccinator mus-cle.

The blood vessels and nerves coming from the mandibular ca-nal emerge through the mental foramen. The mental artery and the mental ramus of the inferior alveolar vein supply the lower lip and the chin region. The mental nerve reaches the skin and the soft tissues of the lower lip and chin region. Mo-tor innervation of the muscles of this region is maintained by the marginal mandibular branches of the facial nerve (CN VII).

Fig 1-47 The frontal belly of the occipitofrontalis muscle is penetrated by branches of the supratrochlear and supraor-bital arteries and veins. Lateral and medial branches of the su-praorbital and supratrochlear nerves run through and above the muscle. Its motor innervation is supplied by the anterior temporal branches of the facial nerve.

The dorsum of the nose is innervated by the external nasal branches arising from the anterior ethmoidal nerve. The nerve

penetrates the suture between the nasal bone and the lat-eral nasal cartilage and runs on the surface of this cartilage. Branches from the infraorbital nerve (external nasal branches) reach the nasal wings. The motor innervation is maintained by the zygomatic branches of the facial nerve (CN VII).

Fig 1-48 Further venous drainage is supplied by additional branches of the supratrochlear vein in the forehead region.

The orbicularis oculi muscle covers the orbital septum. It is well supplied with thin branches of the medial and lateral palpe-bral artery, which empty into the venous superior palpebral arch (upper eyelid) and inferior palpebral arch (lower eyelid). The lateral palpebral artery arises from the lacrimal artery, and the medial palpebral artery from the ophthalmic artery; both of these originate from the internal carotid artery. The venous blood of the upper and lower eyelids is collected by the su-perior and inferior palpebral veins and then redirected to the angular vein (medially); laterally it is collected by the superior ophthalmic vein (upper eyelid) and the inferior ophthalmic vein (lower eyelid).

The procerus and depressor supercilii muscles cover the glabel-lar and supraorbital region. They are penetrated by branches of the lateral and medial rami of the supratrochlear nerve. Their motor innervation is maintained by the temporal rami of the facial nerve (CN VII).

The muscles of the nose are supplied by branches of the angu-lar artery. Further cranially, the terminal branch of the angular artery, the dorsal nasal artery, takes over the arterial supply. The venous drainage is through the external nasal veins, which empty into the angular vein. The infraorbital vein also drains blood from the nose. The sensory innervation is supplied by the ramus of the external nasal nerve (nasalis externus ramus), which is a branch of the ethmoidal frontal nerve. The motor innervation is maintained by zygomatic branches of the facial nerve.

The levator anguli oris muscle now covers the upper and lat-eral corners of the orbicularis oris muscle. The facial artery and vein, as well as the superior labial rami, branches from the in-fraorbital nerve, run at its surface.

The depressor labii inferioris muscle covers the mental fo-ramen

The face in anterior view

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Orbicularis oculi

Levator labii superioris

Zygomaticus minor

Zygomaticus major

Levator anguli oris

Buccinator

Risorius

Levator labii superiorisalaeque nasi muscle

Fig 1-131 Smiling with the mouth closed.

The face

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Orbicularis oculi

Levator labii superiorisalaeque nasi muscle

Levator labii superioris

Zygomaticus minor

Zygomaticus major

Levator anguli oris

Buccinator

Risorius

Fig 1-132 Smiling with the mouth opened.

Facial expression

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Lacrimal caruncle

Superior tarsus

Superior oblique

Medial palpebralligament

Lacrimal sac

Inferior oblique

Inferior tarsus

Inferior rectus

MaxillaInfraorbitalforamen

Zygomatic bone,zygomatic arch

Frontal bone

Levator palpebrae

Lateral palpebral ligament

Zygomaticofacialforamen

Lateral rectus

Ligament oflevator palpebrae

Lacrimal gland,palpebral lobe

Lacrimal gland,orbital lobe

Supraorbital foramen

Trochlea

Frontal notch

Nasal bone

Superior tarsus

Superior oblique

Medial palpebralligament

Lacrimal sac

Inferior oblique

Inferior tarsus

Inferior rectus

MaxillaInfraorbitalforamen

Zygomatic bone,zygomatic arch

Frontal bone

Levator palpebrae

Lateral palpebral ligament

Zygomaticofacialforamen

Lateral rectus

Lacrimal gland,palpebral lobe

Lacrimal gland,orbital lobe

Supraorbital foramen

Trochlea

Frontal notch

Fig 2-17 Postseptal fat removed.Fig 2-18 Lacrimal gland exposed.

The orbital region

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Lacrimal caruncle

Superior tarsus

Superior oblique

Medial palpebralligament

Lacrimal sac

Inferior oblique

Inferior tarsus

Inferior rectus

Maxilla

Lacrimal sac

Nasolacrimalduct

Inferioralveolar canal

Superior lacrimalcanaliculus

Infraorbitalforamen

Zygomatic bone,zygomatic arch

Frontal bone

Levator palpebraesuperioris

Lateral palpebralligament

Zygomaticofacialforamen

Lateral rectus

Ligament oflevator palpebrae

Lacrimal gland,palpebral lobe

Lacrimal lake

Lacrimal gland,orbital lobe

Superior rectus

Supraorbital foramen

Trochlea

Frontal notch

Fig 2-19 Superior tarsal muscle cut and the lacrimal gland removed.Fig 2-20 Lacrimal apparatus.

193

The orbital septum and the eyeball

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Alarcartilage

Lobularconnective tissue

Medial crusof alar cartilage

Quadrangularcartilage

Upper lateralUpper lateralcartilagecartilage

Nasal bone

Nasal foramen

SupraorbitalSupraorbitala. and v.a. and v.

External branchesExternal branchesof the anteriorof the anterior

ethmoidal a. and vethmoidal a. and v

SesamoidSesamoidcartilagecartilage

SuperiorSuperiorlabial v.labial v.

SuperiorSuperiorlabial aa.labial aa.

InfraorbitalInfraorbitala. and v.a. and v.

Fig 3-39 Vascular supply in the deeper nasal region in lateral view.

The nasal and midfacial region

240

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Compressor nariumminor muscle

Dilator naris,anterior muscle

Alar nasalis muscleAlar nasalis muscle

DepressorDepressorsepti nasisepti nasi

Alarcartilage

NasalisNasalis

Procerus

Levator labiiLevator labiisuperioris alaequesuperioris alaequenasi musclenasi muscle

Supraorbital n.,lateral branch

Medial branchof supraorbital n.

Supratrochlear n.

Infratrochlear n.

Externalnasal branch

Superiorlabial branches

Infraorbital n.(CN V2(CN V2(CN V )

Fig 3-40 Nerve supply in relation to the arrangement of muscles in the nasal region, in lateral view.

241

The nose in lateral view

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Nasal cavity

Vomer

Buccal fat pad(of Bichat)

Facial a.

Buccinator

Zygomaticusminor

Zygomaticusmajor

Inferiornasal concha

Medialnasal concha

Maxillarysinus

Maxilla

Greaterpalatine a.

Tooth 3,first upperpermanentmolar

Tooth 30,first mandibularmolar

Tongue

Fig 3-64 Frontal section through the maxillary sinus at the level of the first molar.

The nasal and midfacial region

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Maxillary n.(CN V2(CN V2(CN V )

Levator labiisuperioris

Buccinator

Temporalis

Medialpterygoid

Lateral pterygoid,inferior head

Lateral pterygoid,superior head

Maxillarysinus

Orbicularisoris

Orbicularisoculi

Fig 3-65 Sagittal section through the maxillary sinus at the mid-eye level.

261

The sinuses

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Infraorbital n.(CN V2(CN V2(CN V )

Zygomatico-facial n.Maxilla

Zygomatico-facial a. and v.

Parotidduct

Infraorbitala. and v.

Superficialtemporal a. and v.

Transversefacial a.

Buccal a.

Facial v.

Facial a.

Mental a. andinferior mental v.,

mental branch

Submentala. and v.

Body(of mandible)

Inferioralveolar n.(CN V3(CN V3(CN V )

Buccal n.(CN V3(CN V3(CN V )

Buccinator

Ramus ofmandible

Mental n.(CN V3(CN V3(CN V )

Fig 4-9 Muscles, blood vessel supply (right half of the face) and innervation (left half of the face) of the oral region, deepest layer.

The mouth

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Infraorbital n.(CN V2(CN V2(CN V )

Zygomatico-facial n.Maxilla

Zygomatico-facial a. and v.

Externalcarotid a.

Masseter

Infraorbitala. and v.

Superficialtemporal a. and v.

Transversefacial a.

Masseteric a.Masseteric a.

Superior labiala. and v.

Facial a. and v.

Mental a. andinferior mental v.,

mental branch

Submentala. and v.

Inferior labiala. and v.

Mentalis

Inferior alveo-lar n. (CN V3lar n. (CN V3lar n. (CN V )

Buccal n.(CN V3(CN V3(CN V )

Facial n. (CN VII)VII)

Buccinator

Marginalmandibularbranch (CN VII)

Orbicularisoris

Mental n.(CN V3(CN V3(CN V )

Fig 4-10 Muscles, blood vessel supply (right half of the face) and innervation (left half of the face) of the oral region, orbicularis oris muscle exposed, masseter muscle cut.

Vascular and nerve supply of the oral region

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ArticularArticulardiscdisc

LowerLowerjoint cavityjoint cavity

LateralLateralpterygoidpterygoid

Medial nasalMedial nasalconchaconcha

Inferior nasalInferior nasalconchaconcha

Sphenoid,greater wing

Temporalbone

Upperjoint cavityVomer

Occipital bone,basilar part

Lateral pterygoid,Lateral pterygoid,inferior headinferior head

Lateral pterygoid,Lateral pterygoid,superior headsuperior head

MasseterMasseter

MedialMedialpterygoidpterygoid

Teeth

Mylohyoid

Genio-glossusglossus

Genio-hyoidhyoid

TemporalisTemporalis

Digastric,anterior belly

Fig 4-37 The vertical section through the temporoman-dibular joint shows the articular disc, which creates an up-per and a lower joint space. The masseter and the medial pterygoid muscles create a sling around the mandibular ra-mus and, together with the temporalis muscle, form the group of adductor muscles. The lateral pterygoid muscle has two bellies. The superior belly originates from the in-fratemporal crest of the sphenoid bone and inserts in the articular disc of the temporomandibular joint. Some fibers also attach to the condylar process. Its inferior belly origi-nates from the lateral aspect of the lateral lamina of the

pterygoid process and inserts in the condylar process of the mandible.

Fig 4-38 The mandibular nerve (CN V3) passes through the skull base in the oval foramen and reaches the infratemporal fossa. After the meningeal branch has left to re-enter the cra-nial cavity, the mandibular nerve divides further to provide a motor and sensory supply for the mandibular region. The auriculotemporal nerve curves laterally around the middle meningeal artery and posteriorly, at the height of the man-dibular neck, runs in a lateral direction. After some branches

Fig 4-37 Dorsal view with a vertical section through the temporomandibular joint region.

The mouth

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Auriculo-Auriculo-temporal n.temporal n.

ParotidParotidbranchesbranches

Masseteric n.Masseteric n.

MedialMedialpterygoid n.pterygoid n.

Buccal n.Buccal n.

Lingual n.Lingual n.

Mylohyoid n.Mylohyoid n.

Digastric,anterior belly

InferiorInferioralveolar n.alveolar n.

Mandibular n.(CN V3(CN V3(CN V )

Lateral pterygoid,superior head

Deeptemporal n.

Occipital bone,basilar part

Lateralpterygoid

LateralLateralpterygoid,pterygoid,

inferior headinferior head

MasseterMasseter

MedialMedialpterygoidpterygoid

Teeth

Mylohyoid

Genio-glossusglossus

Genio-hyoidhyoid

TemporalisTemporalis

Fig 4-38 Dorsal view with a vertical section through the temporomandibular joint region.

to the temporomandibular joint have exited, the auriculo-temporal nerve extends close to the ear and, together with the temporal artery and vein, to the skin of the temporal re-gion, where it provides sensory innervation. It also gives off branches into the parotid gland. Branches of the buccal nerve penetrate the buccinator muscle but do not provide motor innervation (which is facilitated by the facial nerve, CN VII); instead, these branches transmit sensory information from the cheek mucosa. The lingual nerve is found at the medial aspect of the mandibular ramus and enters the tongue at the level of the roots of the third molar, providing sensory inner-

vation for its oral portion. From a short stem of the mandibu-lar nerve, the masseteric nerve arises before passing through the mandibular notch to reach the masseter muscle, provid-ing motor innervation for this masticatory muscle. The me-dial pterygoid nerve, also a branch of the mandibular nerve, provides motor innervation for the medial pterygoid mus-cle. Before the inferior alveolar nerve enters the mandibular canal to continue on to provide sensory innervation for the dental and the periodontal structures, a motor branch exits to the mylohyoid muscle and the anterior belly of the digas-tric muscle.

297

Anatomy in the area around the mandibular ramus

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1a

1b1b 1c1c

3b3b

3c3c

4b4b4b 3a3a

3dd

2b2b2a

4a4a4a4a

4c4c4d5b5b 5a

5c5c6b

6a

7

9

8

2.3 mm0.6 mm

1.7 mm

0.5 mm

2.12.1mm

1.5 mm

1.9.9 mm

2.5 mm

1.6 mm

Fig 6-1 Esthetic units of the face. For practical reasons, the skin of the face is divided into esthetic units. For structural reasons, each region must be treated or reconstructed after trauma or tumor resection within itself, without disturbing any of the adjacent regions.The forehead unit consists of a central (1a) and two lateral (1b) subunits, and the eyebrow region is considered as a third (1c) subunit. The nose is subdivided into the region of the dor-sum nasi (2a) and an alar unit (2b). The eyelids need to be di-vided into four subunits: lower lid (3a), upper lid (3b), lateral canthal (3c) and medial canthal (3d). The cheek is also divided into four subunits: medial cheek (4a), zygomatic (4b), lateral (4c) and buccal (4d). The upper lip requires a division into a philtrum subunit (5a), lateral subunits (5b) on either side and a mucosal subunit (5c). The lower lip has only two areas, the cen-tral subunit (6a) and the mucosal subunit (6b). There is also a chin unit (7), an auricular unit (8) and a neck unit (9).

Fig 6-2 The thickness of the facial skin (epidermis and dermis) ranges between 0.5  mm in the lower lid region and 2.5  mm in the chin region. The measurements of skin thick-ness (Gonzales-Ulloa, 1957) correlate with the esthetic regions of the face.

Figs 6-3 to 6-5 Histology of the facial skin. Most of the face is covered by hairy skin. The skin (cutis, corium) consists of the upper epidermis layer and the lower dermis. Underneath the dermis is a cushion of fatty tissue, the subcutis.

The epidermis consists of a five-layered epithelium that con-stantly renews itself (Fig 6-4). The stem cells for this renewal line the basement membrane as the stratum basale (stratum germinativum). These cells divide and start to migrate to the skin surface; they differentiate into keratocytes, forming the stratum spinosum (prickle cell layer). The keratocytes continue to migrate, now producing keratohyaline granules, which are necessary for the keratinization of the skin. These granules can be seen and this further layer is known as the stratum granulo-sum. Often, there is a narrow stratum lucidum above this layer, indicating the beginning of the dissolution of cell organelles. The top layer, the stratum corneum, is the final layer and by this point all cell organelles and the nuclei have disintegrated and the living keratocytes have transformed into dead kera-tin cells. In addition to keratocytes, other cell types are found in the epidermis. Melanocytes are located between the basal cells. They produce melanin, which is distributed to the kerato-cytes through widely branching cellular processes. From these

Fig 6-1 Esthetic units of the face. Fig 6-2 Values for varying thickness of facial skin.

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Subcutaneousvv. and aa.

Profound plexus(vessels)

Superficial plexus(vessels)

Arrector pili

Hair follicle

Sweat gland

Merkel cell

Sebaceousgland

Meissnercorpuscles

SubcutisDermisEpidermis

Fig 6-3 Cross-section of facial skin to show histology.

melanocytes, malignant melanomas may arise. Merkel cells are also located in the stratum basale and act as mechanorecep-tors for tactile and pressure perception. Langerhans cells are found in the stratum spinosum. They are descendants of he-matopoietic stem cells from the bone marrow and participate in cutaneous immune responses. Between the epithelium and the dermis there is a basement membrane where the epider-mis and the dermis are interlocked in a serrated pattern.

The dermis (corium) has two layers. The papillary dermis (stra-tum papillare) is the invaginated margin separated from the epidermis by the basement membrane. In this area, there are

collagen fibers (type I and III) intertwined with elastic fibers. The underlying reticular dermis (stratum reticulare) is charac-terized by highly tensile, thick, parallel bundles of collagen fibers (type I) plus some elastic fibers. All these structural com-ponents are embedded in abundant gelatinous matrix, which consists mainly of water-binding hyaluronic acid and prote-oglycans. In addition, there are fibroblasts and extravasated leukocytes, including T-lymphocytes (T-regulatory and T-helper cells), mast cells and macrophages. Hair roots with their arrec-tor pili muscles (Fig 6-5), and the secretory parts of the seba-ceous and sweat glands are located in the reticular dermis but also extend into the underlying subcutis.

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