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Here is a thorough overview of the human skull, drawn from Gray's Anatomy for Students and supplemented with high-quality anatomical diagrams.

The Human Skull

Overview

The skull has 22 bones (excluding the 6 ossicles of the ear). It is divided into:

The cranium - all skull bones except the mandible
The mandible - the only movable bone of the skull

The cranium is further subdivided into:

Calvaria (skullcap) - the upper domed part covering the brain
Cranial base - the floor of the cranial cavity
Facial skeleton (viscerocranium) - the lower anterior portion

Gray's Anatomy for Students, p. 992

The 8 Cranial Bones (Neurocranium)

These bones enclose and protect the brain:

Bone	Count	Location
Frontal bone	1	Forehead and superior orbital rim
Parietal bones	2 (paired)	Top and sides of the skull
Temporal bones	2 (paired)	Sides and base; contain the ear canal
Occipital bone	1	Back and base; contains the foramen magnum
Sphenoid bone	1	Central base; butterfly-shaped
Ethmoid bone	1	Between the eyes; separates nasal cavity from brain

The 14 Facial Bones (Viscerocranium)

Bone	Count
Nasal bones	2
Lacrimal bones	2
Zygomatic (cheekbones)	2
Maxillae (upper jaw)	2
Palatine bones	2
Inferior nasal conchae	2
Vomer	1
Mandible (lower jaw)	1

Anterior (Front) View of the Skull

Anterior View of the Human Skull - Gray's Anatomy for Students

Key features visible from the front:

Glabella - the smooth flat area between the eyebrows
Nasion - the junction of the nasal and frontal bones
Superciliary arches - bony ridges above the orbits (more pronounced in males)
Supra-orbital foramen - transmits the supra-orbital nerve and vessels
Piriform aperture - the bony entrance to the nasal cavity
Infra-orbital foramen - transmits infra-orbital nerve and vessels
Mental foramen - on the mandible; transmits mental nerve and vessels
Mental protuberance - the chin prominence

Lateral (Side) View of the Skull

Lateral View of the Human Skull - Gray's Anatomy for Students

Key features:

Pterion - the thin, H-shaped junction of frontal, parietal, sphenoid, and temporal bones. Clinically important because the middle meningeal artery runs beneath it - a blow here can cause an extradural (epidural) haematoma
Coronal suture - frontal meets parietal bones
Squamous suture - temporal meets parietal
Lambdoid suture - parietal meets occipital
Mastoid process - rounded projection behind the ear; attachment for sternocleidomastoid
Styloid process - slender projection below the ear
Zygomatic arch - the cheekbone arch formed by zygomatic and temporal bones

Sutures and Fontanelles

Sutures are immovable fibrous joints between skull bones. The major ones are:

Suture	Bones Joined
Coronal	Frontal + parietal
Sagittal	Two parietal bones (midline)
Lambdoid	Parietal + occipital
Squamous	Parietal + temporal

Key junctions:

Bregma - where sagittal and coronal sutures meet (site of anterior fontanelle in infants)
Lambda - where sagittal and lambdoid sutures meet (site of posterior fontanelle)
Asterion - where lambdoid, parietomastoid, and occipitomastoid sutures meet

In fetuses and newborns, fontanelles (unossified membranous gaps) allow the skull to deform during birth and permit postnatal brain growth. The anterior fontanelle closes by around 18 months; the posterior by about 3 months.

Special Joints of the Skull

There are only three pairs of synovial joints in the head:

Temporomandibular joints (TMJ) - between the mandible and temporal bone; the most important movable joints of the skull
Malleus-incus joint (in the middle ear)
Incus-stapes joint (in the middle ear)

All other skull bones are united by sutures.

The Cranial Base (Internal View)

The interior of the base of the skull is divided into three fossae:

Fossa	Key Contents
Anterior cranial fossa	Frontal lobes of the brain; ethmoid bone (cribriform plate - where olfactory nerves pass)
Middle cranial fossa	Temporal lobes; pituitary fossa (sella turcica) on the sphenoid; numerous foramina for cranial nerves
Posterior cranial fossa	Brainstem and cerebellum; foramen magnum (where the brainstem exits to become the spinal cord)

Mandible

The mandible consists of:

Body - the horizontal part bearing the teeth (alveolar part above, base below)
Ramus - the vertical part ascending posteriorly
Angle - where body and ramus meet
Condylar process - articulates with the temporal bone to form the TMJ
Coronoid process - attachment for temporalis muscle
Mental protuberance - the midline chin bump

The Calvaria's Unique Structure

The flat bones of the skullcap have a specialized three-layer sandwich structure:

External table - outer compact (dense) bone
Diploe - middle layer of spongy cancellous bone containing red bone marrow and diploic veins
Internal table - inner compact bone (thinner and more fragile)

This structure provides strength while minimizing weight, and the diploe acts as a shock absorber.

Clinical Highlights

Pterion fractures - can tear the middle meningeal artery, causing an extradural haematoma with a "lucid interval"
Skull base fractures - may result in cerebrospinal fluid leaking from the nose (rhinorrhoea) or ear (otorrhoea)
Craniosynostosis - premature fusion of cranial sutures, restricting brain growth; requires surgical correction
Bulging anterior fontanelle in an infant suggests raised intracranial pressure
Sunken fontanelle suggests dehydration
Wormian (sutural) bones - small extra islands of bone occasionally seen along the lambdoid suture, a normal variant

Sources: Gray's Anatomy for Students; TeachMeAnatomy skull overview

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