Section 7.1: The Skull

Overview of the Skull

The skull is composed of 8 cranial bones and 14 facial bones, forming the framework that supports and protects the brain and associated sensory organs.

• Cranial bones protect the brain.

• Facial bones form the structure of the face, house sensory organs, and provide attachment points for muscles.

Major Sutures of the Skull

• Sutures are immovable joints found between the bones of the skull.

• Major sutures include the coronal, sagittal, lambdoid, and squamous sutures.

Key Skull Features

• Foramen magnum: The large opening at the base of the skull through which the spinal cord passes.

• Auditory ossicles: Small bones in the middle ear cavity that transmit sound vibrations.

• Ethmoid bone: Contains the cribriform plate, which allows passage of olfactory nerves for the sense of smell.

• Hyoid bone: A U-shaped bone in the neck that supports the tongue and is not directly attached to other bones.

Temporomandibular Joint (TMJ)

• TMJ stands for Temporomandibular Joint, the joint connecting the jawbone to the skull.

• Common issues include TMJ syndrome, which can cause pain and dysfunction in the jaw joint and muscles.

• Sinuses are air-filled cavities in certain skull bones that reduce weight and contribute to voice resonance.

Section 7.2: The Orbit and Nasal Complex

Orbit and Nasal Complex

The orbit contains the eyes and associated structures, while the nasal complex encloses the nasal cavities.

• Both cranial and facial bones contribute to the orbital and nasal complexes.

• Paranasal sinuses are air-filled spaces that lighten the skull and enhance voice resonance.

Section 7.4: Fontanelles

Fontanelles in Newborns

Fontanelles are soft, non-ossified fibrous areas between cranial bones in infants, allowing for rapid brain growth and easier passage through the birth canal.

• Major fontanelles include the anterior and posterior fontanelles.

• Fontanelles gradually ossify as the child grows.

Section 7.5: The Vertebral Column

Structure and Function

The vertebral column supports the body, protects the spinal cord, and provides attachment points for ribs and muscles. It also features normal curves that enhance flexibility and shock absorption.

• Composed of 33 vertebrae in five regions: cervical, thoracic, lumbar, sacral, and coccygeal.

• Primary curves (thoracic and sacral) develop before birth; secondary curves (cervical and lumbar) develop after birth.

Key Features of Vertebrae

• Body: The main weight-bearing part of the vertebra.

• Vertebral foramen: The opening through which the spinal cord passes.

• Intervertebral discs: Pads of fibrocartilage between vertebrae that absorb shock and allow movement.

• Spinous process: The bony projection felt through the skin along the back.

Special Cervical Vertebrae

• Atlas (C1): Supports the skull and allows nodding motion.

• Axis (C2): Has the dens (odontoid process) for rotation of the head.

Abnormal Curvatures

• Kyphosis: Exaggerated thoracic curvature (hunchback).

• Lordosis: Exaggerated lumbar curvature (swayback).

• Scoliosis: Lateral curvature of the spine.

Section 7.7: The Thoracic Cage

Structure and Function

The thoracic cage protects vital organs in the chest and provides attachment points for muscles involved in respiration and upper limb movement.

• Consists of the sternum, ribs, and thoracic vertebrae.

• There are 12 pairs of ribs:

  • True ribs (1-7): Attach directly to the sternum via costal cartilages.

  • False ribs (8-12): Attach indirectly or not at all to the sternum.

  • Floating ribs (11-12): Do not attach to the sternum.

• Sternum has three parts: manubrium, body, and xiphoid process.

Clinical Note

• Improper administration of CPR can result in fracture of the xiphoid process of the sternum.

Key Terms and Definitions

• Suture: Immovable joint between skull bones.

• Foramen: Opening in a bone for passage of nerves and blood vessels.

• Sinus: Air-filled cavity within a bone.

• Fontanelle: Soft spot on a newborn's skull.

• Intervertebral disc: Fibrocartilaginous pad between vertebrae.

• Costal cartilage: Cartilage connecting ribs to the sternum.

Table: Comparison of Vertebral Regions

Key Equations and Concepts

• There are no specific equations for bone structure, but understanding the arrangement and function of bones is essential for Anatomy & Physiology.