the cranium

8/7/2019 The Cranium

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The Cranium: A General Overview

The Cranium, also called the "Skull," describes the skeleton of the head, face and

mandible.

It is a portion of the axial skeleton, or that portion associated with the central nervoussystem. Those portions of the skeleton not associated with the central nervous system,

are associated with the appendicular skeleton or the extremities (i.e., the arms and

legs).

The axial skeleton consists of the cranium, all the osseous elements of the vertebral

column, the ribs, and the sternum.

In an adult, various of the bones of the cranium are paired left and a right, while

others, which cross the mid-sagittal plane, are unpaired. Furthermore, the bones of the

skull are classified as those which are called Cranial Bones, or contribute to thatportion surrounding the brain, or Facial Bones (i.e., those which do not assist in

forming the braincase).

Glossary of Terms

Osteology terms:

• Cranium

The cranium of the skull comprises all of the bones of the skullexcept for the mandible.

• Skull The skull refers to all of the bones that comprise the head.

• Calvaria The calvaria refers to the cranium without the facial bonesattached.

• Calotte The calotte consists of the calvaria from which the base hasbeen removed.

• Splanchocranium The splanchocranium refers to the facial bones of the skull.

• Neurocranium The neurocranium refers only to the braincase of the skull.

• Endocranial Refers to the interior of the braincase.



• Axial Refers to the head and trunk (vertebrae, ribs and sternum) of the body.

• Suture The saw-like edge of a cranial bone that serves as jointbetween bones of the skull.

• Aperture An opening or space between bones or within a bone.

• Cavity An open area or sinus within a bone or formed by two or morebones.

• Condyle A rounded enlargement or process possessing an artculatingsurface.

•

Fissure A narrow slit or gap.• Foramen

A hole in a bone usually for the transmission of blood vesselsand/or nerves.

• Fossa A pit, depression, or concavity, on a bone, or formed fromseveral bones.

• Process A general term describing any marked projection or

prominence.• Spinous

Descriptive of a sharp, slender process.• Tubercle

A small process or bump, an eminence.• Tuberosity

A large rounded process or eminence.

Anatomical terms:

• Mid-sagittal plane The imaginary plane that transects the the body along the mid-point into mirrored left and right sides.

• Anterior A relative term meaning nearer the front of the body, in abiped it also means ventral.



• Posterior A relative term meaning nearer the back of the body, in abiped it also means dorsal.

• Inferior The relative term meaning below or of the lower portion of thebody.

• Superior The relative term meaning nearer the top or of the upperportion of the body.

• Proximal A relative term indicating a point nearer the trunk or axialskeleton, a point nearer the mid-sagittal plane.

• Distal A relative term indicating a point that lies farther from the

trunk or away from the mid-sagittal plane.• Medial

The relative term indicating a point lying nearer the mid-sagittal plane.

• Lateral The relative term indicating a point lying farther from the mid-sagittal plane or the midline of the body.

• Lingual Areas nearer the tongue or oral cavity.

• Labial

Areas nearer the lips or cheeks.

SKULL



• The bony casing of the head of humans.

• consists primarily of the

1. cranium (the protective casing of the brain) and

2. the bones of the face, which include the

• maxilla (upper jaw bone),

• mandible (lower jaw bone),

• zygomatic bones (cheekbones), and the

• nasal bones.



• Closely associated with, but not strictly part of, the skull are the

- hyoid (a small bone at the back of the tongue) and the

- auditory ossicles (three tiny

bones in each middle ear

NAMELY: _________,

_____________ AND

____________).

A normal adult human skull

has 8 bones in the cranium

and 14 in the face.

o

This makes a total of 29 if the 6auditory ossicles and one hyoid

are also included. None of these

bones are moveable except for

the joint between the lower jaw

and the rest of the skull.

o The foramen magnum is a large

opening at the base of the skull

through which the spinal cord

passes from the brain.

A human skull is almost full sizedat birth. However the 8 bonesthat make up the cranium arenot yet fused together. Thismeans that the skull can flexand deform during birth,making it easier for to deliver a baby through the narrow birthcanal. The individual plates of bone fuse together after about 24months to form the adult skull.

Human skull, front view



The parietal bones are two of the largest bones of the skull. Together they forma large portion of the sides and roof of the cranium. Each bone has the shape of an irregular quadrilateral, and has two surfaces, four borders, and four angles.The Latin parietalis means "of a wall."

Each parietal bone articulates with the other parietal bone in the midline (top of the head), with the frontal bone in front of it, with the occipital bone behind it,and with the sphenoid and temporal bones lower down on the side of the skull.

The parietal bones are separated from each other by the sagittal suture, fromthe frontal bone by the coronal suture, and from the occipital bone by thelambdoid suture.

The Parietals are paired left and right. Externally, each possess a Superior, and

Inferior Temporal Line, to which the temporal muscle is attached. The lines run

from the Frontal Crest of the anterior frontal bone to the Supra-Mastoid Crest on



the posterior portion of the temporal bone. The parietals articulate with each other by

way of the Mid-Sagittal Suture, and with the frontal bone anteriorly by way of the

Coronal Suture. These two sutures generally form a right angle with one another.

Posteriorly, the parietals articulate with the Occipital Bone by way of the Lambdoid

Suture. The intersection of the Lambdoid and Sagittal Sutures approximate a 120

degree angle on each of the parietals and the occipital bone. Among the sutures the

Lambdoid is by far more serrated than either the Sagittal or the Coronal. Inferiorly the

Parietal articulates with the temporal bone by way of the Squamosal and Parieto-

Mastoid Sutures. On the external surface near the center of the bone is the Parietal

Eminence. Slightly posterior to the eminence there may be a Parietal Foramen.

Internally, the bones possess a number of Meningeal Groves as well as perhaps some

number of Arachnoid Foveae. The groves generally branch from the inferior/anterior

edge of the bone to superior/posterior, while the foveae are freqquenly found along

the sagittal suture. At the area of intersection of the lambdoid and parieto-mastoid

sutures there is a brief portion of the Sigmoid (i.e., Transverse) Sulcus.

TO BE CONTINUED …………………….

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