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Bone and Skull Overview

Oct 13, 2025

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Overview

This lecture covered factors influencing bone development, detailed features of the skull, and introduced the vertebral column as part of the axial skeleton.

Upcoming Assignments & Reminders

  • Integumentary system lecture assignment due Thursday
  • Tissues lab assignment due Friday
  • Lab practical on tissues is Friday

Bone Growth and Development

  • Bone forms through intramembranous ossification (collagen membrane to bone, e.g., skull) and endochondral ossification (cartilage to bone, most bones).
  • Growth plates (epiphyseal plates) allow bones to lengthen until maturity.
  • Nutrition (especially calcium), vitamin D (from sunlight), hormones, and physical exercise affect bone development.
  • Lack of vitamin D or calcium can cause rickets, resulting in soft, deformed bones.
  • Few natural dietary sources of vitamin D; dairy and some juices are supplemented.
  • Safe sun exposure is needed for vitamin D synthesis, balanced with skin protection.

Hormonal Influence on Bone Growth

  • Growth hormone from the anterior pituitary stimulates bone elongation during adolescence.
  • Excess growth hormone: pituitary gigantism (abnormally long bones).
  • Deficient growth hormone: pituitary dwarfism/achondroplasia (shortened long bones).
  • Axial skeleton retains relatively normal size in dwarfism.

Skeletal System Organization

  • Skeleton divided into axial (skull, vertebral column, thoracic cage) and appendicular (limbs, girdles) groups.
  • Adult humans have ~206 bones; infants start with ~270, many fuse over time.
  • Bone handout lists required bones and features for study.

Skull Features & Bones

  • Sutures are joints between skull bones: coronal (frontal-parietal), sagittal (between parietals), squamous (parietal-temporal), lambdoid (occipital-parietal/temporal).
  • Jugular foramen: hole for the jugular vein in the skull base.
  • Frontal bone: supraorbital foramen (hole above eye), frontal sinus (air space).
  • Parietal bones: no distinct features.
  • Occipital bone: foramen magnum (large hole for spinal cord), occipital condyles (rocking surfaces for nodding).
  • Temporal bone: external auditory meatus (ear canal), mastoid process (lump behind ear), styloid process (pointed projection), zygomatic process (part of cheek arch).
  • Sphenoid bone: sella turcica (pituitary seat), sphenoid sinus.
  • Ethmoid bone: olfactory foramina (smell holes), perpendicular plate (part of nasal septum), ethmoid sinus.
  • Maxilla: maxillary sinus, hard palate, infraorbital foramen (hole below eye).
  • Palatine bone: forms posterior hard palate.
  • Zygomatic bone: temporal process (forms cheek arch).
  • Lacrimal bone: near tear duct.
  • Nasal bones: bridge of nose.
  • Vomer: forms lower part of nasal septum.
  • Inferior nasal concha: lower nasal cavity hook.
  • Mandible: mandibular condyle (TMJ joint), coronoid process (jaw muscle attachment), mandibular foramen (nerve entry), mental foramen (nerve exit at chin).

Skull Development and Associated Bones

  • Fontanelles are soft spots of connective tissue on infant skulls for birth and early growth.
  • Skull bones fuse at sutures by age two.
  • Middle ear bones (malleus, incus, stapes) transmit sound.
  • Hyoid bone (U-shaped, above Adam’s apple) supports throat muscles.

Vertebral Column Overview

  • Typically 33 vertebrae: 7 cervical (neck), 12 thoracic (chest), 5 lumbar (low back), sacrum (5 fused), coccyx (3–5 fused).
  • Vertebrae are separated by intervertebral discs.
  • Normal spinal curves: cervical/lumbar (lordotic/forward), thoracic/sacral (kyphotic/backward).
  • Use bone handout for labeled features to study.

Key Terms & Definitions

  • Intramembranous ossification — bone formation from a collagen membrane (e.g., skull).
  • Endochondral ossification — bone formation from a cartilage model.
  • Growth plates (epiphyseal plates) — areas where bone elongates during development.
  • Rickets — bone-softening disease from vitamin D/calcium deficiency.
  • Suture — joint between skull bones.
  • Foramen — a hole in the bone for nerves or vessels.
  • Process — a projection or outgrowth of bone.
  • Sinus — air-filled cavity within a bone.
  • Fontanelle — soft spot on an infant skull.

Action Items / Next Steps

  • Complete the integumentary system lecture assignment by Thursday.
  • Finish the tissues lab assignment and study for Friday’s lab practical.
  • Use the bone handout to guide feature memorization and focus on listed structures.

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