Musculoskeletal System & Cranial Anatomy Notes

Musculoskeletal System Overview

  • The musculoskeletal system includes bones, muscles, joints, and connective tissues essential for movement, stability, and support.

Skull Anatomy

  • Cranial Bones:
    • Parietal
    • Frontal
    • Temporal
    • Ethmoid
    • Occipital
    • Sphenoid
    • Wormian bones (not visible in all views)
  • Facial Bones:
    • Mandible
    • Nasal
    • Lacrimal
    • Maxilla
    • Zygomatic

Anatomical Terms

  • Foramen (pl: foramina): Holes for nerves and vessels.
  • Process: Protrusions for muscle attachment.
  • Fossa: Indentation in bone.
  • Condyle: Rounded protuberance for articulation.

Cranial Vault

  • Comprised of bones protecting the brain; visible in lateral and posterior views.

Cranial Sutures

  • Types of Sutures:
    • Sagittal Suture: Between parietal bones.
    • Coronal Suture: Between frontal and parietal bones.
    • Lambdoid Suture: Between occipital and parietal bones.
    • Squamous Suture: Between temporal and parietal bones.
  • Function: These fibrous joints stabilize skull.

Craniosynostosis

  • Definition: Premature fusion of cranial sutures leading to craniofacial deformities.
  • Types:
    1. Sagittal Synostosis: Fusion of the sagittal suture.
    2. Coronal Synostosis: Fusion of the coronal suture.

Cranial Base Structures

  • Important Features:
    • Foramen magnum: Opening for the spinal cord.
    • Occipital condyles: Articulate with the atlas.
    • Mastoid process: Attachment site for muscles.
    • Styloid process: Muscle attachment site.

Facial Bones & Sinuses

  • Nasal Cavity: Contains nasal bones, maxilla, and vomer.
  • Paranasal Sinuses: Hollow cavities within bones (Frontal, Ethmoidal, Sphenoidal, Maxillary).
    • Function: Lined with epithelium; common infection site.

Muscles of Mastication

  • Muscles Involved:
    • Temporalis: Elevates & retracts the mandible.
    • Masseter: Elevates & protracts the mandible.
    • Medial Pterygoid: Elevates & protracts the mandible.
    • Lateral Pterygoid: Depresses & protracts the mandible.
  • Innervation: Primarily by Trigeminal nerve (CN V3).

TMJ (Temporomandibular Joint)

  • Characteristics:
    • Synovial joint with superior & inferior cavities.
    • Functions in mastication and movement of the jaw.

Tongue Anatomy

  • Extrinsic Muscles: Includes:
    • Genioglossus: Protrudes the tongue.
    • Hyoglossus: Depresses tongue.
    • Styloglossus: Retracts tongue.
    • Palatoglossus: Elevates tongue.
  • Innervation: Hypoglossal nerve (CN XII) except Palatoglossus (Vagus n. CN X).

Oral Cavity & Pharynx

  • Divided into Nasopharynx, Oropharynx, and Laryngopharynx.
  • Muscles: Guide swallowing; consist of pharyngeal constrictors.

Facial Expression Muscles

  • Innervated by Facial Nerve (CN VII).
  • Key Muscles:
    • Platysma: Tenses neck skin; depresses mouth corners.
    • Orbicularis Oculi: Closes eyes.
    • Zygomaticus Major: Elevates mouth corners.

Dentition

  • Types:
    • Permanent Teeth: 32 teeth including incisors, canines, premolars, molars.
    • Deciduous Teeth: 20 primary teeth.
  • Structure: Enamel, dentine, pulp, root, cementum.

Salivary Glands

  • Major Glands:
    • Parotid Gland: 25-30%, CN IX.
    • Sublingual Gland: 3-5%, CN VII.
    • Submandibular Gland: 60-70%, CN VII.
  • Functions: Produce saliva; serous or mucus secretions.