Scalp Fascia Surface Anatomy 3v104n

Scalp, Fascia of the neck and Surface Anatomy For 31st Batch 2009 Dr MB Samarawickrama (MBBS MS)

Surface Anatomy Helps • Land marking of internal structure • Identification of anatomical sites • Clinical judgment • Guide for investigations and management

Surface Anatomy Nasion – the depression between the two supra-orbital margins • Glabella – the ridge above the nasion • Superficial temporal artery – crossing the posterior extremity of the zygomatic arch

The Surface Anatomy • Anterior edge of the mastoid – behind the auricle • Mandible – the whole superficial surface of it is palpable except the coronoid process – Condyloid process – can be felt by a finger placed immediately in front, or within, the external auditory meatus while the mouth is opened and closed.

The Surface Anatomy • Symphysismenti ? • Mandibular foramen – Slight dimple in living 4cm behind the symphysismenti

• Zygomatic bone – The broad anterior part of the arch

The Surface Anatomy • Masseter – clench the teeth and feel over the ramus of the mandible • Temporalis – clench the teeth and feel above the zygomatic arch • Parotid duct – can be rolled over the tensed masseter

The Surface Anatomy of the • Opening of the parotid duct – seen within the mouth at the level of the 2nd upper molar tooth • A line drawn vertically between the 1st & 2nd premolar teeth es through, – the mental foramen (es mental branch of the inferior alveolar nerve) – the infra-orbital foramen (es infra-orbital nerve) – the supra-orbital notch (es supra-orbital nerve)

The Surface Anatomy • Middle meningeal artery – Represented by a line drawn upwards and somewhat forewards from a point along the zygomatic arch, two fingers’ breadth behind the jugalar point ( Jugalar point – the junction between the zygoma and the zygomatic arch) – The posterior branch – es backwards a thumb’s breadth above , and parallel to the zygomatic arch

The Surface Anatomy of the Neck • In the midline from above downwards – Symphysis menti – Hyoid bone – C3 level – Thyroid cartilage – C4 level – Cricoid cartilage – C6 level – Isthmus of the thyroid gland- can be rolled over the 3rd and 4th tracheal rings – Suprasternal notch

The Surface Anatomy •

At the lower border of the cricoid cartilage (C6) 1. The junction of the larynx with the trachea 2. The junction of the pharynx with the oesophagus 3. The inferior thyroid artery and the middle thyroid vein enter the thyroid gland 4. The vertebral artery enters the transverse foramen in the C6 vertebra

The Surface Anatomy 5. Superior belly of the omohyoid crosses the carotid sheath 6. Middle cervical sympathetic ganglion 7. Carotid artery can be compressed against the transverse process of C6

The Surface Anatomy of the Neck (cont’d) • Define the posterior triangle and the anterior triangle by pressing the jaw laterally against resistsnce

The Surface Anatomy • Platysma – (shown by violently clenching the jaw) – es from the mandible down over the clavicles – Lies in the superficial fascia of the skin

The Surface Anatomy • External jugular vein – (visible on straining) – Lies immediately deep to the platysma – Crosses the sternomastoid into the posterior triangle – Perforates the deep cervicle fascia just above the clavicle – Enters the subclavian vein

The Surface Anatomy • Common carotid artery – Carotid artery pulse can be felt by pressing backwards against the anterior tubercle of the transverse process of C6

• Line of carotid sheath – A line ing a point midway between the tip of the mastoid process and the angle of the jaw to the sterno-clavicular t

The Surface Anatomy – Bifurcation of common carotid artery into external and internal carotid arteries at the level of the upper border of the thyroid cartilage

Palpable pulses • Carotid – against the anterior tubercle of the C6 • Facial- anterior border of the maseter over the mandible • Superficial temporal- over the zygomatic arch immediately in front of the auricle

Fascia of the neck The cervical fascia • Compartmentalize the structures in the neck • Afford the slipperiness that allows structures in the neck to move and over one another without difficulty

Fascia of the neck (cont’d) Layers – Superficial cervical fascia (Subcutaneous tissue) – Deep cervical fascia

Superficial cervical fascia • Is a thin layer of connective tissue • Lies between the dermis of the skin and the investing layer of the deep cervical fascia

Superficial cervical fascia (cont’d) • Contains – Cutaneous nerves – Blood and lymphatic vessels – Fat – Platysma (anterolaterally)

Deep cervical fascia •

Consists of 1. 2. 3. 4.

•

Investing layer Pretracheal layer Prevertebral layer Carotid sheath

the viscera, muscles, vessels, deep lymph nodes

Investing layer of deep cervical fascia • The most superficial layer of deep cervical fascia • Surrounds the entire neck deep to the skin and subcutaneous tissue • Splits into superficial and deep layers to – Encloses the – sternocleidomastoid and trapezius muscles – the submandibular and parotid glands – Suprasternal and supra clavicular spaces – Form the fibrous capsule of the parotid gland

Suprasternal space

Investing layer of deep cervical fascia • Attachments – Superiorly • • • • •

External occipital protubarance Superior nuchal line Mastoid process Zygomatic arches Inferior border of the mandible

– Inferiorly • Manubrium • Clavicles • Acromions and spines of the scapulae

Investing layer of deep cervical fascia • Posteriorly • Ligamentum nuchae • Spine of the C7

• Anteriorly • Symphysismenti • Hyoid bone

Pretracheal layer of deep cervical fascia • Thin • Limited to the anterior part of the neck • Extends inferiorly from the hyoid bone into the thorax • Blends with the fibrous pericardium

Pretracheal layer of deep cervical fascia Encloses the • infrahyoid muscles – Omohyoid – Sternothyroid – Sternohyoid – Thyrohyoid

• Thyroid gland

Pretracheal layer of deep cervical fascia

• Is continuous posteriorly and superiorly with buccopharyngeal fascia • Blends laterally with the carotid sheaths

Pretracheal layer of deep cervical fascia Attachments • Superiorly – Hyoid bone – Oblique line of thyroid cartilage – Cricoid cartilage

• Inferiorly – blends with the arch of the aorta

• On either side – Blends with the carotid sheath

Carotid sheath • Is a dense tubular fibrous investment • Extends from the base of the cranium to the root of the neck • Blends anteriorly- with the investing and pretracheal layers of fascia • Blends posteriorly with the prevertebral layer of deep cervical fascia

Carotid sheath • It contains • common and internal carotid arteries • Internal jugular veins • Vagus nerve

Prevertebral layer of deep cervical fascia • Forms a tubular sheath for the vertebral column and muscles associated with it • Extends from the base of the cranium to T3 or T4 vertebra • At T3 it fuses with the anterior longitudinal ligament

Prevertebral layer of deep cervical fascia • Cervical and brachial plexus lie behind the prevertibral fascia • It extends laterally as the axillary sheath

Scalp • Consists of • Skin • Subcutaneous tissue

• Covers the cranium – From the superior nuchal line of the occipital bone – To the supraorbital margins of the frontal bone

Scalp (cont’d) • • 1. 2. 3. 4. 5.

Laterally it extends over the temporal fascia to the zygomatic arches Consists of five layers Skin Connective tissue Aponeurosis SCALP Loose connective tissue Pericranium

Skin • Thin except in the occipital region • Contains many sweat glands, sebaceous glands and hair follicles • Has an abundant arterial supply and good venous and lymphatic drainage

Connective tissue • Forms the thick, dense, richly vascularized, subcutaneous layer • Is well supplied with cutaneous nerves • The space is divided by fibrous septa

Aponeurosis • Is the tendon of the occipito frontalis muscle • Is found between the frontal and occipital bellies of the occipitofrontalis muscle and the superior auricular muscle • It has no boney attachment

Loose connective tissue layer • Like a sponge • Has many potential spaces • Allows free movement of the scalp proper over the underlying calvaria • Is relatively avascular

Pericranium • Is the periosteum of the skull bone • Is firmly attached • but can be stripped fairly easily from the calvaria of living persons except in the cranial sutures

Innervation of the scalp • Anterior to the auricles – By branches of all three divisions of the trigeminal nerve

• Posterior to the auricles – Spinal cutaneous nerves (C2 and C3)

Arteries of the scalp • Run in the layer two (connective tissue) • Are held by the dense connective tissue • Thus tend to remain open when cut • Have abundant anastomoses

Arteries of the scalp (cont’d) Derived from the • External carotid arteries through the – Occipital arteries – Posterior auricular arteries – Superficial temporal arteries

• Internal carotid arteries by way of the – Supratrochlear arteries – Supraorbital arteries

Arteries of the scalp • Supply very little boold to the bones of the calvaria (supplied by the middle meningeal artery) • Thus loss of the scalp does not produce death of the bones forming the calvaria

Venous drainage • Of the superficial parts of the scalp by – Supraorbital vein

Supratrochlear vein

Angular vein

Facial vein

Venous drainage (cont’d) – Superficial temporal veins – Posterior auricular veins – Occipital veins

Venous drainage (cont’d) • Of the deep parts of the scalp – Via emissary veins that communicates with the dural sinuses – Through deep temporal veins (are tributaries of the pterygoid venous plexus) in the temporal region

Lymphatic drainage • Into the superficial ring (pericervical collar) of lymph nodes – Submental – Submandibular – Parotid – Mastoid (retroauricular) – Occipital

Lymphatic drainage (cont’d) • From the superficial ring nodes to the deep cervical lymph nodes along the internal jugular vein • There are no lymph nodes in the scalp