Scalp Anatomy

HEAD AND NECK

OBJECTIVES

• Introduction
• Describe the layers of scalp

Identify the bones, joints, cavities and views of the skull Describe the structure (processes, spines, body, rami ) and functions of cervical vertebrae Describe functions and innervation of muscles of the scalp, facial expression, mastication and neck Describe parts band functions of the brain Describe cranial nerves

• Outline major blood supply and lymphatic drainage of the head and neck

Describe surface anatomy of the head and neck

INTRODUCTION

The head and neck region of the body contains many important structures compressed into a relatively small area The head is formed mainly by the skull with the brain and its covering meninges enclosed in the cranial cavity.

The special senses, the eye and the ear, lie within the skull bones or in the cavities bounded by them.

The brain gives rise to 12 pairs of cranial nerves, which leave the brain and pass through foramina and fissures in the skull. All the cranial nerves are distributed to structures in the head and neck, except the 10th, which also supplies structures in the chest and abdomen

SCALP

The scalp consists of skin (normally hair bearing) and subcutaneous tissue that cover the neurocranium from the superior nuchal lines on the occipital bone to the supra-orbital margins of the frontal bone Laterally, the scalp extends over the temporal fascia to the zygomatic arches.

LAYERS OF SCALP

Skin: thin, except in the occipital region, containing many sweat and sebaceous glands and hair follicles. It has an abundant arterial supply and good venous and lymphatic drainage.

Connective tissue: forms the thick, dense, richly vascularized subcutaneous layer that is well supplied with cutaneous nerves.

Aponeurosis (epicranial aponeurosis): the broad, strong, tendinous sheet that covers the calvaria and serves as the attachment for muscle bellies converging from the forehead and occiput and from temporal bone on each side

Scalp Anatomy

Loose areolar tissue: a sponge-like layer including potential spaces that may distend with fluid as a result of injury or infection. This layer allows free movement of the scalp proper (the first three layers—skin, connective tissue, and epicranial aponeurosis) over the underlying calvaria.

Pericranium: a dense layer of connective tissue that forms the external periosteum of the neurocranium.

MENINGES

The central nervous system consists of the brain and spinal cord.

The brain and spinal cord are completely covered by three membranes, the meninges lying between the skull and the brain, and between vertebrae and the spinal cord. These are Dura mater

• Arachnoid mater

Pia mater

DURA MATER

The cerebral dura mater consists of two layers of dense fibrous tissue.

The outer layer takes the place of the periosteum on the inner surface of the skull bones, and the inner layer provides a protective covering for the brain.

The dura mater forms several structures that separate the cranial cavity into compartments and protect the brain from displacement. These are The falx cerebri separates the hemispheres of the cerebrum The falx cerebelli separates the lobes of the cerebellum The tentorium cerebelli separates the cerebrum from the cerebellum

Venous blood from the brain drains into venous sinuses between the layers of dura mater

The superior sagittal sinus that runs across the top of the brain is formed by falx cerebri and the tentorium cerebelli forms the straight and transverse sinuses.

The epidural space is a potential space that may exist between the dura mater and the skull. If there is hemorrhage in the brain, blood may collect here.

The subdural space is a space existing between the dura mater and the middle layer of the meninges, the arachnoid mater

ARACHNOID MATER

The arachnoid or arachnoid mater is the middle layer of the meninges.

In some areas, it projects into the sinuses formed by the dura mater. These projections are the arachnoid granulation or arachnoid villi. . They transfer cerebrospinal fluid from the ventricles back into the bloodstream.

The subarachnoid space lies between the arachnoid and pia mater. It is filled with cerebrospinal fluid.

All blood vessels entering the brain, as well as cranial nerves pass through this space.

PIA MATER

This is a fine connective tissue containing many minute blood vessels. It adheres to the brain, completely covering the convolutions and dipping into each fissure.

It continues downward covering the spinal cord.

Beyond the end of the cord it continues as the filum terminale, pierces the arachnoid tube and goes on, with the dura mater, to fuse with the Periosteum of the coccyx.