Human Anatomy and Physiology: The Skeleton

Human Anatomy and Physiology - Chapter 07: The Skeleton

Introduction

  • Importance of Understanding Skeleton Anatomy:
    • Anticipates potential medical issues, such as complications in labor and delivery due to pelvic dimensions.

The Skeleton Overview

  • Components of the Skeletal System:
    • Consists of bones, cartilages, joints, and ligaments:
    • Predominantly bone.
    • Cartilage found in isolated areas.
    • Ligaments connect bones and reinforce joints.
  • Body Mass Contribution:
    • The skeleton accounts for approximately 20% of total body mass.
  • Major Divisions of the Skeleton:
    • Axial Skeleton
    • Appendicular Skeleton

Part 1: The Axial Skeleton

  • Definition:
    • Composed of 80 bones grouped into three major regions:
    • Skull
    • Vertebral Column
    • Thoracic Cage
  • Functions of the Axial Skeleton:
    • Provides the longitudinal axis of the body.
    • Supports the head, neck, and trunk.
    • Protects the brain, spinal cord, and thoracic organs.

The Human Skeleton

  • Labelled Bones Overview (Figures 7.1a and 7.1b):
    • Cranial Bones:
    • Form part of the skull, encasing the brain.
    • Facial Bones:
    • Framework of the face including nasal and zygomatic structures.
    • Other notable bones include the clavicle, scapula, sternum, ribs, vertebrae, humerus, radius, ulna, carpals, phalanges, femur, patella, tibia, fibula, tarsals, and metatarsals.

Section 7.1: The Skull

  • Complex Structure:
    • Most complex bony structure in the body.
  • Divisions of the Skull:
    • Cranial Bones and Facial Bones:
    • Cranial Bones: Enclose and protect the brain within the cranial cavity; attach to head and neck muscles.
    • Facial Bones:
      • Framework of the face.
      • Houses cavities for special sense organs (sight, taste, smell).
      • Provides openings for air and food passage and secures teeth.
      • Anchor muscles for facial expressions.
    • Skull Bone Composition:
    • Most bones are flat and connected by sutures (joints with serrated edges).
    • The mandible is the only movable bone.
Overview of Skull Geography
  • Cranium:
    • Divided into:
    • Cranial Vault (Calvaria): Superior, lateral, and posterior portions of the skull, includes the forehead.
    • Cranial Base: Inferior aspect — consists of three fossae (anterior, middle, posterior) where the brain sits.
  • Other Cavities of the Cranium:
    • Middle and internal ear cavities, nasal cavity, orbits for the eyeballs.
  • Openings in Skull:
    • 85 Named Openings:
    • Include foramina, canals, fissures for passageways of the spinal cord, major blood vessels, and cranial nerves.
Major Structures of the Skull (Figures 7.2a, 7.2b, 7.2c)
  • Cranial Bones (Total of 8):
    1. Frontal Bone:
    • Forms the anterior of the cranium.
    • Contains the frontal sinuses.
    1. Parietal Bones (2):
    • Form most of the superior and lateral aspects of the cranial vault.
    1. Occipital Bone:
    • Forms the posterior wall of the skull and contains the foramen magnum.
    1. Temporal Bones (2):
    • Comprise inferolateral aspects and part of the cranial base, house inner/middle ear cavities.
    1. Sphenoid Bone:
    • Bat-shaped; articulates with all other cranial bones.
    • Contains the sella turcica which houses the pituitary gland.
    1. Ethmoid Bone:
    • Deepest skull bone; includes cribriform plates forming the roof of the nasal cavity.
  • Associated Features of the Cranial Bones:
    • Sutures: Include coronal, sagittal, lambdoid, and squamous suture.
Facial Bones Overview
  • Composition: Facial skeleton made up of 14 bones, 12 of which are paired (except mandible and vomer).
  • Key Facial Bones Include:
    1. Mandible: Largest and strongest facial bone.
    2. Maxillary Bones (2)*
    3. Zygomatic Bones (2)
    4. Nasal Bones (2)
    5. Lacrimal Bones (2)
    6. Palatine Bones (2)
    7. Vomer
    8. Inferior Nasal Conchae (2)
Mandible Specifics
  • Structure: U-shaped, composed of body and rami.
  • Features Include:
    • Coronoid Process: Insertion point for temporalis muscle.
    • Condylar Process: Articulates with the temporal bone at the temporomandibular joint (TMJ).
    • Foramina: Includes mental foramen for nerves and vessels.
Maxillae Details
  • Function: Fused bones forming the upper jaw and central facial skeleton.
  • Key Anatomical Regions:
    • Include alveolar processes for the upper teeth, palatine processes for the hard palate, and frontal processes.
Zygomatic, Nasal, Lacrimal, Palatine, Vomer and Inferior Nasal Conchae
  • Zygomatic Bones: Form cheekbones and inferolateral margins of orbits.
  • Nasal Bones: Form bridge of the nose.
  • Lacrimal Bones: Form medial walls of orbits.
    • Contains lacrimal fossa for tear drainage.
  • Palatine Bones: L-shaped; form posterior part of the hard palate.
  • Vomer: Forms part of the nasal septum.
  • Inferior Nasal Conchae: Paired bones forming part of lateral walls of nasal cavity, largest of the three pairs of conchae.
Orbital and Nasal Cavity Structures
  • Orbits: Enclose eyes and lacrimal glands, attachment sites for eye muscles.
    • Formed by seven bones: frontal, sphenoid, zygomatic, maxilla, palatine, lacrimal, and ethmoid.
  • Nasal Cavity Structure: Comprised of ethmoid, vomer, and septal cartilage, and features turbinates for airflow regulation.
Paranasal Sinuses
  • Description: Air-filled spaces within cranial bones lined with mucosa.
  • Functions: Warm and humidify air, lighten skull, and enhance voice resonance.
Clinical Considerations of the Skull
  • Mastoid Air Cells: Located in mastoid process; infections can lead to mastoiditis.
  • Congenital Conditions: Such as cleft palate, cause complications, especially in infants.

Part 2: The Appendicular Skeleton

  • Division Overview:
    • Composed of bones forming human limbs and their girdles.
    • Pectoral Girdle: Attaches upper limbs to the trunk.
    • Pelvic Girdle: Attaches lower limbs to the trunk, supporting pelvic organs.
Pectoral Girdle Details
  • Structure: Comprises clavicles and scapulae, allowing for a vast range of motion.
  • Clavicle Characteristics:
    • S-shaped bone, articulates with sternum medially and scapula laterally.
Scapula Structure
  • Anatomy: Flat, triangular bone located on the dorsal surface of the rib cage.
  • Key Features: Include glenoid cavity, acromion, and coracoid process.
Upper Limb Structure
  • Framework: Composed of 30 bones in total (upper arm, forearm, wrist, and hand).
  • Humerus Features: Largest bone in the arm; articulates with scapula and forearm bones.
  • Forearm Composition: Made up of radius and ulna; their structures facilitate forearm mobility.
Leg Structure
  • Bones: Tibia and fibula are the primary constituents of the leg.
  • Tibia Characteristics: Weight-bearing bone; includes key structures like medial malleolus and tuberosity.
  • Fibula: Non-weight bearing, provides muscle attachments.
Foot Structure
  • Framework: Consists of tarsals, metatarsals, and phalanges.
  • Arches of the Foot: Crucial for weight distribution and balance.

Developmental Aspects of the Skeleton

  • Infant vs Adult Skulls: Infant skull has fontanelles that allow for easy birth and growth.
  • Importance of Curve Development: Primary and secondary curvatures guide proper skeletal development as we age.