By convention, the ear is subdivided into three parts: the external, middle and inner ear. It is largely, but not entirely, contained within the temporal bone. The ears not only receive, modulate, conduct, amplify and discriminately analyse the complex pressure waves that are sound, but also contain the end organs of balance. Temporal Bone Each temporal bone consists of four components: the squamous, petromastoid and tympanic…

The larynx is an air passage, a sphincter and an organ of phonation, and extends from the tongue to the trachea. It projects ventrally between the great vessels of the neck and is covered anteriorly by skin, fasciae and the infrahyoid strap muscles that lower the hyoid bone and the larynx. Above, it opens into the laryngopharynx and forms its anterior wall; below, it continues into…

The pharynx is a 12–14 cm long musculomembranous tube shaped like an inverted cone. It extends from the cranial base to the lower border of the cricoid cartilage (the level of the sixth or seventh cervical vertebrae), where it becomes continuous with the oesophagus. The width of the pharynx varies constantly because it is dependent on muscle tone, especially of the constrictors. At rest, the pharyngo-oesophageal…

Box 39.1 and Table 39.1 set out the different anatomical and clinical terms that are applied to some of the structures described in this chapter. Box 39.1 A note on terminology ‘The advent of endoscopic sinus surgery led to a resurgence of interest in the detailed anatomy of the internal nose and paranasal sinuses. However, the official Terminologia Anatomica used by basic anatomists omits many of…

Infratemporal Fossa The infratemporal fossa lies deep to the ramus of the mandible. It communicates with the temporal fossa superiorly deep to the zygomatic arch; the orbit anteriorly through the inferior orbital fissure; the pterygopalatine fossa medially through the pterygomaxillary fissure; the middle fossa through the foramina ovale and spinosum. It contains lateral and medial pterygoid, the mandibular division of the trigeminal nerve, the chorda tympani…

The mouth extends from the lips and cheeks externally to the anterior pillars of the fauces internally, where it continues into the oropharynx. The mouth can be subdivided into the vestibule external to the teeth and the oral cavity proper internal to the teeth ( Fig. 37.1 ). The palate forms the roof of the mouth and separates the oral and nasal cavities. The floor of…

Skin The scalp and buccolabial tissues are described here. The structure of the eyelids is discussed in Chapter 44 . Scalp The scalp extends from the top of the forehead anteriorly to the superior nuchal line posteriorly. Laterally, it projects down to the zygomatic arch and external acoustic meatus. It consists of five layers: skin, subcutaneous tissue, occipitofrontalis (epicranius) and its aponeurosis, subaponeurotic loose areolar tissue…

The neck extends from the base of the cranium and the inferior border of the mandible to the thoracic inlet. Skin The skin in the neck is normally under tension. Lines of greatest tension have been termed ‘relaxed skin tension lines’; surgical incisions made along these lines are said to heal better with minimal postoperative scarring. Cutaneous vascular supply and lymphatic drainage The blood vessels supplying…

The skull is the bony skeleton of the head. It houses the brain, the organs of special sense, and the upper parts of the respiratory and digestive systems and provides attachments for many of the muscles of the head and neck. Movement is restricted and is found only in relation to the mandible at the temporomandibular joint and at the atlanto-occipital joint for movement of the…

Skin and Fascia Face and scalp The superficial fascia of the scalp is firm, dense, fibroadipose, and closely adherent to the skin and to the underlying muscle, epicranius and the epicranial aponeurosis. Posteriorly, the fascia is continuous with the superficial fascia of the back of the neck, and laterally it is prolonged into the temporal region, where it is looser in texture. Three fascial layers (a…

The cerebral hemispheres are the largest part of the human brain: they consist of the telencephalon (cerebral cortex and underlying white matter), basal ganglia and diencephalon. Both hemispheres are interconnected by the corpus callosum and the anterior commissure. The cerebral cortex contains the motor and premotor regions, the highest level at which motor activities are controlled, and the primary sensory regions, which provide the first cortical…

The term basal ganglia is used to denote a number of subcortical nuclear masses that lie in the inferior part of the cerebral hemisphere, in close relationship with the internal capsule ( Fig. 31.1 ). The traditional definition of the basal ganglia included the corpus striatum, claustrum and amygdaloid complex. The term has now been restricted to the corpus striatum and, according to some authorities, other…

The diencephalon is part of the prosencephalon (forebrain), which develops from the most rostral primary cerebral vesicle that differentiates into the caudal diencephalon and the rostral telencephalon. The cerebral hemispheres, containing the lateral ventricles, develop from the telencephalon. The sites of evagination of the telencephalon become the interventricular foramina, through which the two lateral ventricles and the midline third ventricle communicate. The diencephalon corresponds largely to…

The cerebellum is the largest part of the hindbrain, recognized as a distinct division of the brain from the time of Herophilus (335–280 BC) and Galen (AD 131–200). It is situated in the posterior cranial fossa, beneath the tentorium cerebelli, the medial extension of the falx cerebri and the overlying occipital lobe and lies behind the pons and medulla, from which it is separated by the…

The brainstem is situated in the posterior cranial fossa, where it faces the clivus and dorsum sellae ventrally and the cisterna magna, fourth ventricle and cerebellum dorsally ( Fig. 28.1 ). It is approximately 6–7.5 cm in length and 3–4 cm in width at its widest portion. Its caudal border corresponds to the transverse plane immediately above the exit of the first cervical nerve roots. Its…

The spinal cord provides innervation for the trunk and limbs via spinal nerves and their peripheral ramifications. It receives primary afferent fibres from peripheral receptors located in widespread somatic and visceral structures, and sends motor axons to skeletal muscle. It also contains the cell bodies of all the preganglionic neurones responsible for the sympathetic innervation of cardiac and smooth muscle and secretory glands, and for the…

The brain is a highly vascular organ, its profuse blood supply characterized by a densely branching arterial network ( ). It has a high metabolic rate that reflects the energy requirements of constant neural activity. It receives about 15% of the cardiac output and utilizes 25% of the total oxygen consumption of the body. The brain is supplied by two internal carotid arteries and two vertebral…

The meninges consist of three concentric membranes that envelop the brain and spinal cord, supporting and protecting the delicate tissues they surround. The individual layers, from outside to inside, are the dura mater (pachymeninx), arachnoid mater and pia mater. The dura is an opaque, tough, fibrous coat that incompletely divides the cranial cavity into compartments and accommodates the dural venous sinuses. The arachnoid is much thinner…

The human nervous system is the most complex product of evolution. The activity of its billions of neurones constitutes the physical basis of sensory experience, motor behaviour, consciousness and self-awareness. Research to elucidate the mechanisms that underlie these functions is one of the most active areas of contemporary biology and medicine and is essential for the future treatment and prevention of neurological and psychiatric disorders. The…