Identify the correct statement regarding the three types of sutures.
Multiple Choice
a. An example of a plane suture is the squamous suture between the temporal and parietal bones.
b. Lap sutures occur where two bones have overlapping beveled edges.
c. Serrate sutures are seen between the palatine processes of the maxillae in the roof of the mouth.
d. Examples of lop sutures include the coronal, sagittal, and lambdold sutures that border the parietal bones.
The Correct Answer and Explanation is:
The correct answer is:
b. Lap sutures occur where two bones have overlapping beveled edges.
Explanation:
Sutures are fibrous joints that connect the bones of the skull. They are immovable joints (synarthroses) and are classified based on the way the edges of the bones interlock or overlap. There are three main types of sutures:
- Plane Sutures (also called butt sutures)
- Lap Sutures (also called squamous sutures)
- Serrate Sutures
Let’s review each option with explanations:
a. An example of a plane suture is the squamous suture between the temporal and parietal bones.
- This statement is incorrect because the squamous suture is not a plane suture; it is a lap suture.
- Plane sutures are characterized by two bones with straight, butt-edged bones meeting without overlapping or interlocking, creating a simple, straight joint.
- The squamous suture, between the temporal and parietal bones, has overlapping beveled edges — typical of a lap suture, not plane.
b. Lap sutures occur where two bones have overlapping beveled edges.
- This is correct.
- Lap sutures feature bones that overlap each other at beveled edges, creating a smooth, interlocking joint.
- A classic example is the squamous suture between the temporal and parietal bones.
- The overlapping nature allows some stability but also some flexibility during growth.
c. Serrate sutures are seen between the palatine processes of the maxillae in the roof of the mouth.
- This statement is incorrect.
- Serrate sutures have interlocking, saw-toothed edges, similar to the coronal, sagittal, and lambdoid sutures.
- The palatine processes of the maxillae join at the midline of the roof of the mouth, but their suture is more of a plane or butt suture, not serrate.
- Serrate sutures are common in areas where the bones interlock like the sagittal suture between the parietal bones.
d. Examples of lop sutures include the coronal, sagittal, and lambdold sutures that border the parietal bones.
- This statement is incorrect.
- The coronal, sagittal, and lambdoid sutures are serrate sutures, not lap sutures.
- Serrate sutures have interlocking edges that resemble a serrated knife.
- Lap sutures are found where bones overlap, such as the squamous suture.
Summary:
- Plane sutures: Flat, straight edges meeting — no overlap (rare in the skull).
- Lap sutures: Bones overlap with beveled edges (e.g., squamous suture).
- Serrate sutures: Interlocking saw-tooth edges (e.g., coronal, sagittal, lambdoid sutures).
Therefore, option b correctly describes lap sutures and is the right answer.