Bone Structure & Physiology Quiz

Bone Structure & Physiology

• Red Marrow: Present in infant cavities, in adults found only in epiphyses spaces of spongy bone.
• Haversian Canal: Central canal running parallel to the bone's long axis. Contains blood vessels, nerves, and lymph vessels.
• Osteocytes: Mature bone cells residing in lacunae, chambers arranged in concentric circles called lamellae around the Haversian canal.
• Osteon: Structure composed of a central canal and all its concentric lamellae, also known as a Haversian system.
• Canaliculi: Tiny canals radiating from the Haversian canal, forming a communication and transport network for nutrients.
• Volksmann's canals: Perpendicular to the bone shaft, originating from the periosteum, connecting bone marrow cavity and central cavities.

Bone Ossification

• Endochondral Ossification: Uses hyaline cartilage as a model for bone formation.
• Primary Ossification Center: Area where bone formation begins in endochondral ossification.
• Steps of Endochondral Ossification:
  • Periosteum replaces perichondrium.
  • Osteoblasts secrete bone around the pre-existing cartilage.
  • Cartilage calcifies, hollows, forming a cavity.
  • Periosteal bud containing osteoblasts, osteoclasts, vessels, red marrow, and nerves invades the cavity, forming a medullary cavity on either side of the primary ossification center.
  • During bone growth, medullary cavity lengthens and widens.
  • After adolescence, the epiphyseal plate of ossifying cartilage is replaced by a calcified epiphyseal line.

Cartilage Types and Locations

• Cartilage: Composed mainly of water with varying amounts of elastic, reticular, or collagen fibers. Has an outer covering called perichondrium for growth and repair.
• Cartilage Types:
  • Elastic: Found in the ear.
  • Hyaline: Found in articular cartilage, costal cartilage, laryngeal cartilage, tracheal, bronchial, and nasal cartilage.
  • Fibrocartilage: Found in intervertebral discs.

Bone Disease

• Osteoporosis: Gradual bone mass loss, leading to weakened bones, increased risk of fractures. Caused by hormone deficiencies, calcium/vitamin deficiencies, physical inactivity, and unhealthy habits.

Axial Skeleton

• Axial Skeleton: Composed of the skull, vertebral column, and bony thorax.
  • Consists of 80 bones.

Skull & Cranial Bones

• Skull: Divided into cranium and facial bones.
  • Cranium: Encloses the brain.
  • Facial Bones: Contain features for eyes, facial muscles.
• Sutures: Joints connecting skull bones (except for mandible), offering immobility.
• Cranium: Divided into a superior cranial vault (calvaria) and inferior cranial floor (base).
  • Cranial floor has three concavities: Anterior, Middle, and Posterior fossa, housing the brain.
• Cranial Bones:
  • Frontal: Anterior cranium, including forehead, superior orbit, and floor of anterior fossa.
    • Supraorbital Foramen/Notch: Passages for blood vessels and nerves above each orbit.
  • Parietal (paired): Form the superior sides of the cranium.
    • Sagittal Suture : Articulation point of the parietal bone.
  • Temporal (paired): Form the inferior sides of the cranium.
    • Squamous Suture: Articulation point of the temporal and parietal bones.
    • Zygomatic Process: Bridge-like extension forming the cheekbone.
    • Mandibular Fossa: Rounded depression articulating with the mandible.
    • External Acoustic Meatus: Canal leading to the eardrum and middle ear.
    • Styloid Process: Attachment site for muscles and ligaments of the neck.
    • Mastoid Process: Attachment site for muscles.
    • Mastoiditis: Infection of the mastoid process, potentially spreading to the meninges (brain coverings) causing meningitis.
    • Stylomastoid Foramen: Opening for cranial nerve VII.
    • Jugular Foramen: Opening for jugular vein and cranial nerves IX, X, and XI.
    • Carotid Canal: Opening for internal carotid artery.
    • Internal Acoustic Meatus: Passage for cranial nerves VII, and VIII.
    • Foramen Lacerum: Opening for internal carotid artery and small nerves.
  • Occipital: Posterior portion of the cranium, joining the sphenoid bone anteriorly.
    • Lambdoid Suture: Articulation point of the occipital and parietal bones.
    • Foramen Magnum: Large opening for the spinal cord.
    • Hypoglossal Canal: Passage for the hypoglossal nerve (cranial nerve XII).
    • Occipital Condyles: Articulate with C1, the Atlas.
  • Sphenoid: Bat-shaped bone forming the anterior plateau of the middle cranial fossa, spanning the width of the skull.
    • Greater Wings: Part of the orbital socket.
    • Superior Orbital Fissure: Jagged opening for cranial nerves III, IV, V, and VI to serve the eye.
    • Inferior Orbital Fissure: Passage for infraorbital vessels and cranial nerve V.
    • Sella Turcica (Turk's Saddle): Central portion of the bone.
      • Hypophyseal Fossa (Seat of the Saddle): Holds the pituitary gland.
    • Optic Canals: Openings for the optic nerves.
    • Foramen Rotundum and Ovale: Openings for branches of the fifth cranial nerve.
    • Foramen Spinosum: Opening for the middle meningeal artery.
  • Ethmoid: Anterior to the sphenoid, forms the roof of the nasal cavity, upper nasal septum, and part of the medial orbital wall.
    • Crista Galli: Vertical projection, attachment point for the dura mater of the brain.
    • Cribiform Plates: Bony plates lateral to the crista galli, holding the olfactory foramina for passage of olfactory fibers.
    • Horizontal Plate: Includes the crista galli and cribiform plates.
    • Perpendicular Plate: Forms the superior nasal septum.
    • Lateral Masses: Part of the medial orbital walls.
    • Superior and Middle Nasal Conchae: Turbinates aiding nasal cavity mucosa in warming and humidifying incoming air.

Facial Bones

• Facial Bones: 7 paired bones (14) and 2 single bones (Vomer and Mandible).
  • Mandible:
    • Mandibular Body: Forms the chin.
    • Mandibular Condyle: Articulates with the mandibular fossa.
    • Conoid Process: Site for muscle attachment.
    • Mental Foramen: Passage for mental blood vessels.
    • Alveolar Margin: Site for inferior teeth sockets.
    • Mandibular Symphysis: Site where mandible fuses.
    • Mandibular Foramen: Passage for CN V (5).
  • Maxillae (Facial Keystone):
    • Alveolar Margin: Site for superior teeth sockets.
    • Palatine Processes: Anterior portion of the hard palate.
    • Infraorbital Foramen: Passage for infraorbital blood vessels.
    • Incisive Fossa: Passage for the nasopalatine artery and blood vessel.
  • Lacrimal Bone:
    • Lacrimal Fossa: Passage for tears, part of the eye orbit.
  • Palatine Bone:
    • Forms posterior portion of the hard palate.
  • Zygomatic Bone:
    • Forms cheeks and part of the eye orbit.
  • Nasal Bone:
    • Forms bridge of the nose and part of the eye orbit.
  • Vomer:
    • Forms inferior nasal septum.
  • Hyoid:
    • Attachment site for neck and tongue muscles.

Vertebral Column

• Vertebral Column: Composed of 24 vertebrae, sacrum, and coccyx.
  • Vertebrae:
    • Cervical Vertebrae: 7 bones in the neck.
    • Thoracic Vertebrae: 12 bones in the upper back.
    • Lumbar Vertebrae: 5 bones in the lower back.
  • Intervertebral Discs: Fibrocartilage separating vertebrae, serving as cushions and shock absorbers.
    • Nucleus Pulposus: Inner gelatinous mass of the disc.
    • Annulus Fibrosus: Outer ring of collagen fibers surrounding the nucleus pulposus.
  • Ruptured Disc: Occurs when nucleus pulposus herniates through annulus fibrosus, compressing spinal nerves.
• S-Shape of Spine: Prevents shock, allows flexibility.
  • Primary Curvature: (Thoracic and Sacral), present at birth.
  • Secondary Curvature: (Cervical and Lumbar), develops later.
• Spinal Curvature Abnormalities:
  • Scoliosis: Excessive lateral curvature of the spine.
  • Kyphosis: Excessive dorsal curvature of the spine.
  • Lordosis: Excessive anterior curvature of the spine.

Vertebra Structure

• Body (Centrum): Rounded central portion facing anteriorly.
• Vertebral Arch: Composed of pedicles, laminae, and a spinous process.
  • Pedicles: Connect body to laminae.
  • Laminae: Connect spinous and transverse processes.
  • Spinous Process: Posterior projection of the arch.
• Vertebral Foramen: Opening between the arch and the body, allowing passage of the spinal cord.
• Transverse Process: Lateral projection of the arch.
• Superior and Inferior Articular Processes: Paired projections lateral to the vertebral foramen, articulating between vertebrae. Superior processes face towards the spinous process, and inferior processes face away.
• Intervertebral Foramina: Spaces within the pedicles, allowing spinal nerves to exit between vertebrae.

Cervical Vertebrae

• C1 (Atlas): Lacks a body, has large depressions in the lateral processes that receive occipital condyles.
• C2 (Axis): Acts as a pivot for atlas rotation.
• Mastoid Process: Muscle attachment.
• External Acoustic Canal: Passage for sound to the middle ear.
• Internal Acoustic Canal: Passage for CN VII and VIII.
• Foramen Lacerum: Passage of internal carotid artery.

Occipital Bone

• Lambdoid Suture: Articulation point of the occipital and parietal bones.
• Foramen Magnum: Passage for the spinal cord.
• Hypoglossal Canal: Passage for CN XII.
• Occipital Condyles: Articulation point with C1, the Atlas.

Sphenoid Bone

• Greater Wings: Part of the eye socket.
• Superior Orbital Fissure: Passage for CN III, IV, V, and VI.
• Inferior Orbital Fissure: Passage for infraorbital vessels and CN V.
• Hypophyseal Fossa: Holds the pituitary gland.
• Optic Canal: Passage for CN II.
• Foramen Rotundum and Ovale: Passage for CN V.
• Foramen Spinosum: Passage for middle meningeal artery.

Ethmoid Bone

• Lateral Masses: Part of the eye orbit.
• Crista Galli: Attachment for dura mater to the skull.
• Cribriform Plates: Hold olfactory foramina for passage of CN I (olfactory nerve).
• Horizontal Plate: Includes the crista galli and cribiform plates.
• Perpendicular Plate: Forms the superior nasal septum.
• Superior and Inferior Nasal Conchae: Turbinates.