The suture that separates the parietal bone from the tabular portion of the occipital bone is called:
A. Sagittal suture
B. Frontal suture
C. Coronal suture
D. Lambdoidal suture
Correct Answer: D. Lambdoidal suture
Explanation
The suture that separates the parietal bone from the squamous (tabular) part of the occipital bone is called the lambdoid (lambdoidal) suture.
Explanation:
- The parietal bones form the sides and roof of the skull.
- The occipital bone forms the posterior part of the skull; its squamous (tabular) part lies behind the parietal bones.
- The lambdoid suture is a fibrous joint that runs between:
- Parietal bones (anteriorly)
- Occipital bone – squamous/tabular part (posteriorly)
Key point to remember:
- Lambdoid suture = Parietal + Occipital
- It is named “lambdoid” because its shape resembles the Greek letter λ (lambda).
✅ Correct answer: Lambdoid (lambdoidal) suture
Other Options Details
These are cranial sutures of the fetal skull, important in labour and delivery because they allow moulding of the head.
Description of each 👇
A. Sagittal suture
- Location: Runs in the midline of the skull
- Between: Two parietal bones
- Direction: Anteroposterior
- Extent: From anterior fontanelle (bregma) to posterior fontanelle (lambda)
- Obstetric importance:
- Most important landmark in vaginal examination
- Helps to identify position of the fetal head
B. Frontal suture (Metopic suture)
- Location: In the midline of the frontal bone
- Between: Two halves of the frontal bone
- Extent: From anterior fontanelle to root of nose
- Normally: Fuses in early childhood
- Obstetric importance:
- Palpable in fetus and newborn
- Helps in identifying face or brow presentation
C. Coronal suture
- Location: Runs transversely
- Between: Frontal bone and parietal bones
- Direction: From one side of skull to the other
- Obstetric importance:
- Less commonly felt during labour
- Helps in orientation of the fetal skull
D. Lambdoidal suture
- Location: Posterior part of skull
- Between: Parietal bones and occipital bone
- Direction: Transverse and oblique
- Obstetric importance:
- Meets sagittal suture at posterior fontanelle (lambda)
- Used to confirm occipital position
Summary Table
Suture Bones Joined Importance Sagittal Parietal–Parietal Most important in labour Frontal Frontal–Frontal Identifies brow/face Coronal Frontal–Parietal Skull orientation Lambdoidal Parietal–Occipital Occipital position
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Writer: Vandita Singh, Lucknow (GS India Nursing Group