Sagittal

Definition

In bilaterian anatomy, pertaining to or situated in a longitudinal plane that divides the body into right and left portions. The sagittal plane is perpendicular to both the transverse (horizontal) and coronal (frontal) planes. A mid-sagittal (or median sagittal) section passes through the midline, producing symmetrical halves; a para-sagittal section lies parallel but lateral to the midline, creating unequal portions. In arthropods, sagittal planes are used to describe internal anatomy in dissections, histological sections, and micro-CT reconstructions, though the dorsoventrally flattened body plan of many insects and arachnids often makes sagittal and coronal orientations less intuitive than in vertebrates.

Etymology

From Latin sagitta, arrow, via the term sagittal suture of the skull; coined by Gerard of Cremona in medieval anatomical translations.

Example

A mid-sagittal section of a honey bee worker reveals the dorsal vessel, esophagus, and nerve cord running in parallel along the body axis; in a para-sagittal section through the leg, the tracheal air sacs and femoral musculature appear asymmetrically.

Synonyms

• Median
• midsagittal (when through midline)

Related Terms

• coronal
• transverse
• Dorsal
• Ventral
• Median
• para-sagittal
• frontal plane
• longitudinal section

Usage Notes

In arthropod morphology, 'sagittal' is sometimes used loosely for any longitudinal vertical section, but precision matters: true sagittal requires right-left division, whereas 'longitudinal' alone does not specify orientation relative to the dorsoventral or lateral axes. In flattened arachnids such as harvestmen, sagittal sections are rarely practical; dorsal or ventral views with transverse sections are preferred. The term contrasts with 'frontal' (coronal), which divides dorsal from ventral, and 'transverse' (horizontal), which divides anterior from posterior.