The Skull Anatomy PDF

THE SKULL CHARACTERISTICS  Is slightly flattened from side to side  It is smooth viewed from above; very uneven viewed from below  Oval in shape, wider behind than its front  Composed of irregular and flat bones  Base is much thicker and stronger  Presents a number of openings...

THE SKULL CHARACTERISTICS  Is slightly flattened from side to side  It is smooth viewed from above; very uneven viewed from below  Oval in shape, wider behind than its front  Composed of irregular and flat bones  Base is much thicker and stronger  Presents a number of openings called the foramina for the passage of the spinal cord, the cranial nerves and blood vessels CHARACTERISTICS Made up of 2 layers of compact bones:  outer layer is thick and tough called the outer table  Inner layer is thinner and more brittle called the inner table enclosing a layer of spongy bone called diploe DEFINITION OF TERMS  SKULL-refers to the entire skeleton of the head and the face, including the mandible  CRANIUM- refers to the skull minus the mandible  CALVARIUM-refers to the skull after the bones of the face have been removed  The skull is composed of a series of flattened and irregular bones, united at immobile joints called SUTURE., with the exception of the mandible THE DIFFERENT VIEWS OF THE SKULL Norma Verticalis Norma Verticalis FALSE SUTURE Norma Occipitalis Norma Frontalis Norma Frontalis Norma Lateralis Norma Lateralis Norma Basalis Interna Norma Basalis Externa The bones of the head enclose the following cavities:  CRANIAL CAVITY-contains the brain  ORBITAL CAVITIES-contain the eyeballs, lacrimal gland, ciliary ganglion, muscles moving the eyeballs, and the blood and nerve supply  NASAL CAVITIES-are separated from each other by the bony nasal septum  Divisions of the bones of the skull A. Cerebral or cranial bones or brain case which is made up of 8 bones 1. unpaired bones- 4 bones a. occipital bone (flat) b. frontal bone (flat) c, sphenoid bone (irregular) d. ethmoid bone (irregular) 2. paired bones -4 bones a. the parietal bones (flat) b. the temporal bones (irregular) The Occipital Bone The occipital bone forms the posterior and inferior portions of the cranium. Along its superior margins, the occipital bone articulates with parietal bones forming the lambdoidal Yellow - parietal bone suture. Red- lambdoidal suture Green- Occipiltal bone The Frontal Bone The frontal bone of the cranium forms the forehead and superior surface of each eye socket or orbit. Green- frontal bone The Sphenoid Bone The sphenoid bone forms the floor of the cranium. It also acts as a bridge uniting the cranial and facial bones, and it braces the sides of the skull. The Ethmoid Bone  The Ethmoid bone consists of two honeycombed masses of bone.  It forms part of the cranial floor, contributes to the medial surface of the orbit of each eye, and forms the roof and the sides of the nasal cavity. The Parietal Bones 2 in number It forms the roof/ superior wall of the skull. The bone is posterior to the frontal bone and anterior to occipital bone. The 2 bones articulates to form the sagittal suture. Green - parietal bone The Temporal Bones Lying below the parietal bones and contributing to the sides and base of the cranium. It comes it contact with the parietal bone it forms the squamosal suture. Green- frontal bone Yellow- parietal bone Light green- occipital Blue- temporal bone  Divisions of the bones of the skull B. Facial or visceral cranium -14 bones 1. paired bones- 12 bones a. nasal bones (flat) b. lacrimal bones (flat) c. Maxilla (irregular) d. zygomatic/malar/cheek bones (irregular) e. palatine bones (flat) f. inferior nasal conchae/turbinates (irregular) 2. unpaired bones -2 bones a. the vomer (flat) b. the mandible (irregular) The Nasal Bones Forming the bridge of the nose. It is located midway between the orbits, the nasal bones and it articulate with the frontal bone and the maxillary bones. Red- Nasal bone The Lacrimal Bones The lacrimal bones are found within the medial wall of the orbit. They articulate with the frontal, Ethmoid and maxillary bones. Aqua blue- Lachrymal bone The Maxillary Bones  The maxillary bones or Maxillae, articulate with all other facial bones except the mandible.  It forms the mid-face; houses the maxillary sinus and the upper teeth Yellow-maxilla The Zygomatic Bones  On each side of the skull (facial).  It is also known as the cheek or malar bone  Zygomatic bone articulates with the frontal bone and the maxilla to complete the lateral wall of the orbit. Black- Zygomatic bone The Palatine Bones  The paired palatine bones form the posterior surface of the bony hard palate, or the roof of the mouth.  Superiorly it communicates the orbit, forming its floor. The Inferior Nasal Conchae  The paired inferior nasal conchae project from the lateral wall of the nasal cavity. Green- Inferior nasal concha vomer  A flat bone that forms the lower part of the bony nasal septum  The Mandible It is the bone of the lower jaw. It has a body and two upward processes called ramus The superior part of the ramus has a condlye and a coronoid process, the first forms part the TMJ and the latter form part of the attachment of the muscles of mastication. FONTANELS  membrane-filled spaces found between the bones.  Important for the development of the brain case  Closure indicates bone ossification is completed  Non-closure indicates incomplete bone formation  Membranous tissue between the cranial bones at the sutures and fontanels allows certain degrees of overlapping during birth process, thus reducing the diameter of the baby’s skull, a process called ‘MOLDING” Fontanels :found in the newborn baby’s skull  Anterior or bregmatic fontanel-largest, situated between the frontal and parietal bones, it closes completely by the second year of life (18-24 months)  Posterior or occipital fontanel-triangular gap between the occipital and parietal bones. It closes completely two months after birth.  Sagittal fontanel – found along the sagittal suture in the region of the parietal foramina or obellion. It maybe closed already at birth Fontanels :found in the newborn baby’s skull  Antero-lateral or sphenoidal fontanel -is found at the antero-inferior angles of the parietal bones. it closes three months after birth.  Postero-lateral or mastoidal fontanel- is found at the postero-inferior angles of the parietal bones. It is completely closed by the first year of life. Frontal, Anterior, or Bregmatic  Posterior or Occipital Skull at Birth, Superior View  Sagittal Fontanel Skull at Birth, Superior View Anterolateral or Sphenoidal Posterolateral or Mastoidal anomalies  MICROCEPHALY- is a small skull caused by the early closure of the fontanels  MACROCEPHALY- Is a big skull caused by the delayed closure of the fontanels  HYDROCEPHALUS-is a condition characterized by increased intracranial pressure due to excessive amount of cerebrospinal fluid inside the brain causing the fontanels to remain open. It is usually fatal if uncorrected or with mental and physical retardation if the child survives. SUTURES -are named according to the bones they unite except: 1. Coronal or fronto-parietal sutures 2. Sagittal or interparietal or parieto-parietal sutures 3. lambdoid Classification of sutures 1. True or sutura Vera where the articulating surfaces are smooth a. sutura dentata has tooth-like appearance of the suture EX: sagittal suture b. sutura serrata has a saw-tooth like configuration; it is finer than sutura dentata EX: zygomatico-maxillary suture c. sutura limbosa where the articulating bones overlap with one another EX; coronal suture Classification of sutures 1. False or sutura Notha where the articulating surfaces are rough a. sutura squamosa has scale-like appearance of the articulating surfaces EX: temporo-parietal suture or squamosal suture b. sutura harmonia has simple apposition of articulating parts or surfaces; they may also be overlapping without definite shape. EX: internasal suture Terms  WORMIAN OR SUTURAL BONES-are islands of bones found within the sutures  PNEUMATIC BONES-contain air spaces due to loss of inner spongy layer. These cavities which are filled with air are called PARANASAL SINUSES