The boundaries between skull bones are immovable joints called:
(a) Foramina
(b) Fontanelles
(c) Lacunae
(d) Sutures

Verified step by step guidance

1. Step 1: Understand the types of structures mentioned in the options. Foramina are openings or holes in bones that allow nerves and blood vessels to pass through.
2. Step 2: Recognize that fontanelles are soft spots on a baby's skull where the bones have not yet fused, allowing for growth of the brain and skull.
3. Step 3: Know that lacunae are small spaces within bone tissue that house osteocytes (bone cells), not joints between bones.
4. Step 4: Identify that sutures are immovable joints found between the bones of the skull, where the bones are tightly bound by fibrous connective tissue.
5. Step 5: Conclude that the correct term for immovable joints between skull bones is sutures.

Key Concepts

Immovable Joints (Synarthroses)

Immovable joints, or synarthroses, are connections between bones that allow little to no movement. They provide stability and protection, especially in the skull where bones must be firmly joined to protect the brain.

Sutures

Sutures are the fibrous joints that connect the bones of the skull. These joints are immovable in adults, tightly binding the skull bones together, and are characterized by interlocking edges that provide strength and stability.

Fontanelles

Fontanelles are soft, flexible gaps between the skull bones in infants. These allow for brain growth and skull expansion during early development, eventually closing as sutures form and harden into immovable joints.