Cribriform plate

Fig. 2.9 Nasal chemoreceptive systems (Terminalis MOS and AOS) in neonate Rabbit. CP = cribriform plate F = forebrain GT = ganglion terminale NT(SNT) = Nervus terminalis ON = olfactory nvs. and F = forebrain (after Huber and Guild, 1913).

Fig. 4.6(a) Migration of LHRH neurocrine cells prenatal transportation along the track of extra-bulbar VN axons (caudal branch). CB, cribriform plate FB, forebrain cell types, TAG-1, transient axonal surface glycoprotein and N-CAM, neural cell adhesion molecule (from Yoshida et al, 1995). 

The dendrites on the receptor cells have swellings, the olfactory knobs. These knobs have smooth vesicles that may be open to the mucus covering the epithelium. From each knob extend 1 to 150 cilia, floating in the mucus. The precise number of cilia varies with the species. The rabbit, for example, has 10-12 cilia on each knob. The surrounding mucus consists of mucopolysaccharides, lipids, and phosphatides. The axons of the olfactory receptor cells extend through the cribriform plate and terminate in the olfactory bulb (Fig. 5.1). 

Figure 5.9 The human olfactory system. (A) Section through the nose. (B) Section through the cribriform plate. (C) The olfactory pathway to the cerebrum (forebrain). This shows the pathway of olfactory sensation. Nasal stimulation begins at the cilia of the olfactory receptor cells located at the ends of the olfactory nerves. The olfactory nerves then carry the impulse to the cerebrum, resulting in the sense of smell.

The olfactory bulb sits at the base of the brain on the cribriform plate. Humans have two olfactory bulbs, the right bulb that receives signals from the right olfactory epithehum and the left bulb that receives signals from the left olfactory epithelium. In the bulb, centers called glomeruli exist, each of which receives signals from only one type of receptor cell, irrespective of where those receptors are located on the epithehum. Olfactory receptor... 

Axons from the olfactory epithelium travel in parallel fascicles (Daston et al. 1990) but form a dense plexus after they pass through the cribriform plate. Individual glomeruli receive fascicles entering from different directions (Le Gros Clark, 1951 1956). A similar plexus of fibers is seen in amphibians (Scalia, 1976 Kauer, 1981 Duncan et al. 

Olfactory neuroblastoma (ONE) is the prototypic round cell tumor of the sinonasal tract. It occurs over a broad age range (average 40 to 45 years) and affects both sexes equally. The tumor most commonly arises high in the nasal cavity and has its primary attachment or origin at the cribriform plate. Rare cases will have origins in other locations within the sinonasal cavity. The tumor is frequently polypoid. Clinically, patients with ONE can present with nonspecific sinonasal symptoms such as obstruction and nasal congestion, and they... 

Small cell neuroendocrine carcinomas similar to those seen in the lung are exceptionally rare in the nasal cavity and paranasal sinuses. They affect both sexes equally and occur over a broad age range (38 to 68 years in one studyThey may arise either in the nasal cavity or in the paranasal sinuses, especially the ethmoid and maxilla. Though some tumors will remain localized to the site of origin, higher grade tumors are likely to invade into adjacent structures such as the orbit, cribriform plate, or cranial cavity. 

The olfactory receptor cells are located in the olfactory epithelium. This is a greenish-yellowish patch of tissue, several square centimetres in area, which is found on the roof of the nasal cavity, as shown in Figure 13.8. The epithelium is about 100-200 pm thick and is bathed in an aqueous liquid known as the olfactory mucus. The mucus is about 35 pm thick and flows backwards across the epithelium at about l-6cm/min. The receptor cells run through the cribriform plate at the base of the skull. At one end (in the epithelium) the cells contain hairs, or cilia, which are 20-200 pm long and which is where the receptor proteins are located. 

The olfactory cells run through the cribriform plate at the base of the skull and feed directly into the olfactory bulb. Neurons from the epithelium converge on areas of the olfactory bulb known as glomeruli. Evidence... 

Horizontal cribriform plate where the falx cerebri attaches (Fig. 103-19). 

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