ETHMOID SINUS: The ethmoid sinuses begin to form in the third to fifth fetal months, when numerous separate evaginations
arise from the nasal cavity.
It is commonly present in the bladder neck and trigone region, where prostatic evaginations
during embryonic development have been reported.
The testis, epididymis, and most of the ductus deferens are enveloped by the vaginal tunic, an evagination
of abdominal peritoneum that extends through the inguinal canal into the scrotum.
The sinovaginal bulbs are two solid evaginations
originating from the urogenital sinus at the distal aspect of the mullerian tubercle, as shown at right (A).
of the dorsal aorta form paired glomeruli, which are partially surrounded by out-pocketing of the nephrostomial ducts (Bowman's capsules).
3) The anterior and middle ethmoid cells begin as evaginations
from the nasal cavity into the middle meatus at about the third month of fetal development.
The normal pancreas is derived from several evaginations
of the wall of primitive duodenum.