Morphogenesis and growth of the soft tissue and cartilage of the vomeronasal organ in pigs

Abstract

The morphology of the soft tissue and supporting cartilage of the vomeronasal organ of the fetal pig was studied from early stages to term. Specimens obtained from an abattoir were aged by crown-to-rump distance. Series of transverse sections show that some time before birth all structures--cartilage, connective tissue, blood vessels, nerves, glands and epithelia--are well developed and very similar in appearance to those of the adult. Furthermore, in transmission electron microscopy photomicrographs obtained at this stage the vomeronasal glands exhibit secretory activity.

Fig. 1

Transverse sections through the VNO of the prenatal pig. Centre, camara lucida drawing of a section through the whole VNO of a 12-cm specimen. Clockwise from top left: HE-stained sections showing the development of the vomeronasal epithelia; SE, sensory epithelium; VNCg, vomeronasal cartilage; VNDc, vomeronasal duct; d, dorsal; l, lateral. Scale bar = 100 µm.

Fig. 2

HE-stained transverse sections through the VNO of 3.1-cm and 22-cm pig fetuses, showing communication between the VNDc and the nasal (NC) and oral (OC) cavities via the incisive duct (asterisk). PI, papilla incisiva; VNDc, vomeronasal duct; d, dorsal; l, lateral. Scale bar = 100 µm.

Fig. 3

Transverse sections through the VNO of prenatal pig at two different levels and magnifications (A and B), showing the typical appearance and arrangement of connective tissue (arrows). VNCg, vomeronasal cartilage. Stain: Weigert's resorcin-fuchsin. Scale bar = 100 µm.

Fig. 4

Transverse sections through the VNO of several prenatal pig specimens stained with haematoxylin-eosin (A–C) or toluidine blue (D–G). The general topography of the soft tissue is illustrated in the main picture (C), which shows a section taken caudally. The other pictures show the myelinization status of the nasocaudal nerves (D, E, and arrowhead in C) and the vomeronasal nerves (F,G, and arrows in A–C). Scale bars = 20 µm (A), 50 µm (C1,D,F), 100 µm (B,C2,E,G) and 500 µm (C).

Fig. 5

Transverse sections through the VNO of several prenatal pig specimens stained with Weigert's resorcin-fuchsin (A,B) or haematoxylin-eosin (the others), showing arteries (A,B, arrows) with a clear tunica intima, subepithelial capillaries (C, arrows), veins (V) and venous sinuses (asterisks). LE, lateral epithelium; SE, sensory epithelium. Scale bar = 20 µm (C,D), 50 µm (A,B) and 100 µm(E–G).

Fig. 6

Transverse sections through the VNO of several prenatal pig specimens stained with haematoxylin-eosin (A–C), PAS (D,F,H) or PAS and Alcian blue (E,G,I), showing vomeronasal glands opening into the lumen of the VNDc (A–C) and reactivity of vomeronasal glands (D–I, arrows). Scale bar = 20 µm (A) and 100 µm (others).

Fig. 7

TEM micrographs of the apical cytoplasm of VNGl cells showing the release of the contents of secretory granules by fusion of granule and cell membrane (arrows). L, lumen. Scale bar = 1 µm.

Fig. 8

Selected members of series of HE-stained transverse sections through the VNO of several prenatal pig specimens, showing the vomeronasal cartilage (in black) at various levels (I–VI) as described in the text.

Fig. 9

Cellular components of the vomeronasal cartilage at various stages of prenatal development, showing the fibrous layer of the perichondrium (A,B, double arrow), mitotic figures (C,D, arrows), cell nests (E, arrows) and round and oval chondrocytes (F, arrows). Scale bar = 50 µm.