Axial skeleton

Skull: Cranial Bones

1. Frontal Bone

   • Location: Anterior cranium (forehead).

   • Function: Protects the frontal lobe of the brain; forms superior orbit and part of cranial floor.

2. Parietal Bones

   • Location: Superior and lateral sides of the cranium.

   • Function: Forms the roof and sides of the cranial cavity, protecting the brain.

3. Temporal Bones

   • Location: Lateral sides of the cranium near ears.

   • Function: Houses structures for hearing (external auditory meatus) and muscle attachment (mastoid/styloid processes).

4. Occipital Bone

   • Location: Posterior and base of the cranium.

   • Function: Protects occipital lobe and allows spinal cord passage through the foramen magnum.

5. Sphenoid Bone

   • Location: Base of the skull, central to the cranial floor (bat-shaped).

   • Function: Protects the pituitary gland in the sella turcica; forms part of orbits and cranial floor.

6. Ethmoid Bone

   • Location: Between the nasal cavity and orbits.

   • Function: Forms part of nasal septum, medial orbit walls, and roof of nasal cavity; allows olfactory nerve passage via cribriform plate.

Facial Bones

1. Maxillae

   • Location: Upper jaw, below orbits.

   • Function: Supports upper teeth and forms part of the hard palate.

2. Mandible

   • Location: Lower jaw.

   • Function: Enables chewing by articulating with the temporal bones; supports lower teeth.

3. Zygomatic Bones

   • Location: Cheekbones, lateral to maxillae.

   • Function: Forms the cheeks and part of the lateral orbital wall.

4. Nasal Bones

   • Location: Bridge of the nose.

   • Function: Supports the cartilage that shapes the nose.

5. Lacrimal Bones

   • Location: Medial walls of orbits.

   • Function: Contains the lacrimal fossa for tear drainage.

6. Palatine Bones

   • Location: Posterior part of the hard palate.

   • Function: Forms part of the hard palate and nasal cavity floor.

7. Inferior Nasal Conchae

   • Location: Lateral walls of the nasal cavity.

   • Function: Increases surface area to warm and humidify air.

8. Vomer

   • Location: Inferior part of the nasal septum.

   • Function: Divides nasal cavity into left and right sides.

Vertebral Column

1. Cervical Vertebrae (7)

   • Location: Neck region.

   • Function: Supports the skull and allows head movement.

2. Thoracic Vertebrae (12)

   • Location: Upper and mid-back.

   • Function: Articulates with ribs and supports the thoracic cage.

3. Lumbar Vertebrae (5)

   • Location: Lower back.

   • Function: Bears weight of the upper body.

4. Sacrum (5 fused vertebrae)

   • Location: Base of the spine, between the hip bones.

   • Function: Connects spine to pelvis; supports weight transfer to lower limbs.

5. Coccyx (3–5 fused vertebrae)

   • Location: Tailbone, at the very base of the spine.

   • Function: Provides attachment for ligaments and muscles of the pelvic floor.

6. Intervertebral Discs

   • Location: Between vertebrae.

   • Function: Cushions and absorbs shocks; allows flexibility.

Thoracic Cage

1. Sternum

   • Location: Center of the chest, anteriorly.

   • Function: Protects the heart, lungs, and major blood vessels.

   a. Manubrium

   • Location: Upper part of the sternum.

   • Function: Articulates with clavicles and first ribs.
     b. Body

   • Location: Central portion of the sternum.

   • Function: Articulates with ribs 2–7.
     c. Xiphoid Process

   • Location: Inferior portion of the sternum.

   • Function: Attachment point for abdominal muscles.

2. Ribs
   a. True Ribs (1–7)

   • Location: Directly attached to the sternum via costal cartilage.

   • Function: Protect thoracic organs.
     b. False Ribs (8–10)

   • Location: Indirectly attached to the sternum via costal cartilage.

   • Function: Protect lower thoracic organs.
     c. Floating Ribs (11–12)

   • Location: Not attached to the sternum.

   • Function: Protect kidneys.

Hyoid Bone

1. Location: In the neck, above the larynx.

   • Function: Provides attachment for tongue and neck muscles; does not articulate with any other bone.

Fetal Skull

1. Fontanelles (Soft Spots)

   • Location: Between cranial bones in a fetal or infant skull.

   • Function: Allows skull compression during birth and brain growth after birth.
     a. Anterior Fontanelle

     • Location: Top of the skull.

     • Function: Largest fontanelle, closes last.
       b. Posterior Fontanelle

     • Location: Back of the skull.

     • Function: Closes early in development.
       c. Sphenoidal Fontanelle

     • Location: Near temples.

     • Function: Enables lateral skull flexibility.
       d. Mastoid Fontanelle

     • Location: Behind the ears.

     • Function: Allows posterior cranial flexibility.