Lakhasly

[?/??Receptor binding produces depolarization of the gustatory cells, stimulating the sensory nerve fibers that send information to the brain for processing.Taste buds detect at least five broad categories of tastants: sodium ions (salty); hydrogen ions from acids (sour); sugars and related compounds (sweet); alkaloids and certain toxins (bitter); and amino acids such as glutamate and aspartate (umami; Jap.?] Dr/Samaher Mohammed ?: The lamina propria of the olfactory epithelium possesses large serous glands, the olfactory glands (of Bowman), which produce a constant flow of fluid surrounding the olfactory cilia and facilitating the access of new odoriferous substance [?/???] Dr/Samaher Mohammed ?: Olfactory Epithelium The olfactory chemoreceptors for the sense of smell are located in the olfactory epithelium, a specialized region of the mucous membrane covering the superior conchae at the roof of the nasal cavity.They are not restricted to papillae and are also widely scattered elsewhere on the dorsal and lateral surfaces of the tongue, where they are also continuously flushed by numerous minor salivary glands.The apical (luminal) pole of each olfactory cell is its dendrite end and has a knoblike swelling with about a dozen basal bodies, from which long cilia project into the overlying aqueous layer.Supporting cells are columnar, with narrow bases and broad, cylindrical apexes containing the nuclei and extending microvilli into the fluid layer.The paranasal sinuses communicate with the nasal cavities through small openings; mucus produced there is moved into the nasal passages by the activity of the ciliated epithelial cells.?] Dr/Samaher Mohammed ?: Paranasal Sinuses The paranasal sinuses are bilateral cavities in the frontal, maxillary, ethmoid, and sphenoid bones of the skull (Figure 17-1).Approximately 250 taste buds are present on the lateral surface of each vallate papilla, with many others present on fungiform and foliate (but not the keratinized filiform) papillae.?] Dr/Samaher Mohammed ?: Taste buds are ovoid structures within the stratified epithelium on the tongue's surface, which sample the general chemical composition of ingested material (Figures 15-4 and 15-5).Salt and sour tastes are produced by ion channels and the other three taste categories are mediated by G-protein-coupled receptors.Olfactory neurons are bipolar neurons present throughout this epithelium.?:?????:???:??[??/???:??

[٩/‏٩ ٧:٢٩ م] Dr/Samaher Mohammed 🌼: Olfactory Epithelium
The olfactory chemoreceptors for the sense of smell are located
in the olfactory epithelium, a specialized region of the
mucous membrane covering the superior conchae at the roof
of the nasal cavity. In adult humans, it is about 10 cm2
in area
and up to 100 μm in thickness. This thick, pseudostratified
columnar epithelium has three major cell types (Figure 17–3):
■ Olfactory neurons are bipolar neurons present
throughout this epithelium. Their nuclei form an irregular row near the middle of this thick epithelium. The
apical (luminal) pole of each olfactory cell is its dendrite
end and has a knoblike swelling with about a dozen basal
bodies, from which long cilia project into the overlying
aqueous layer. These cilia have nonmotile axonemes and
collectively provide a large surface for transmembrane
chemoreceptors. The receptors respond to odoriferous
substances by generating an action potential along the
axons extending from the basal ends of these neurons.
The axons leave the epithelium and unite in the lamina
propria as very small nerves that then pass to the brain
through foramina in the cribriform plate of the ethmoid bone (Figure 17–3). There they form the olfactory
nerve (cranial nerve I) and eventually synapse with neurons in the olfactory bulb of the brain.
■ Supporting cells are columnar, with narrow bases
and broad, cylindrical apexes containing the nuclei and
extending microvilli into the fluid layer. Well-developed
junctional complexes bind the supporting cells to the
olfactory cells. The supportive role of these cells is not
well understood, but they express abundant ion channels
that help maintain a microenvironment conducive to
olfactory function and survival.
■ Basal cells are small, spherical or cone-shaped cells near
the basal lamina. These are the stem cells for the other two
types, replacing the olfactory neurons every 2-3 months
and support cells less frequently
[٩/‏٩ ٧:٣٠ م] Dr/Samaher Mohammed 🌼: The lamina propria of the olfactory epithelium possesses
large serous glands, the olfactory glands (of Bowman), which
produce a constant flow of fluid surrounding the olfactory cilia
and facilitating the access of new odoriferous substance
[٩/‏٩ ٧:٣٥ م] Dr/Samaher Mohammed 🌼: Paranasal Sinuses
The paranasal sinuses are bilateral cavities in the frontal, maxillary, ethmoid, and sphenoid bones of the skull (Figure 17–1).
They are lined with a thinner respiratory epithelium having
fewer goblet cells. The lamina propria contains only a few small
glands and is continuous with the underlying periosteum. The
paranasal sinuses communicate with the nasal cavities through
small openings; mucus produced there is moved into the nasal
passages by the activity of the ciliated epithelial cells.
[١٠/‏٩ ٥:٠٥ م] Dr/Samaher Mohammed 🌼: Taste buds are ovoid structures within the stratified
epithelium on the tongue’s surface, which sample the general
chemical composition of ingested material (Figures 15–4 and
15–5). Approximately 250 taste buds are present on the lateral surface of each vallate papilla, with many others present
on fungiform and foliate (but not the keratinized filiform)
papillae. They are not restricted to papillae and are also widely
scattered elsewhere on the dorsal and lateral surfaces of the
tongue, where they are also continuously flushed by numerous
minor salivary glands.
A taste bud has 50-100 cells, about half of which are elongated gustatory (taste) cells, which turn over with a 7- to
10-day life span. Other cells present are slender supportive
cells, immature cells, and slowly dividing basal stem cells that
give rise to the other cell types. The base of each bud rests on
the basal lamina and is entered by afferent sensory axons that
form synapses with the gustatory cells. At the apical ends of the
gustatory cells, microvilli project toward a 2-μm-wide opening in the structure called the taste pore. Molecules (tastants)
dissolved in saliva contact the microvilli through the pore and
interact with cell surface taste receptors (Figure 15–4).
Taste buds detect at least five broad categories of tastants:
sodium ions (salty); hydrogen ions from acids (sour); sugars
and related compounds (sweet); alkaloids and certain toxins (bitter); and amino acids such as glutamate and aspartate
(umami; Jap. umami, savory). Salt and sour tastes are produced by ion channels and the other three taste categories are
mediated by G-protein–coupled receptors. Receptor binding
produces depolarization of the gustatory cells, stimulating the
sensory nerve fibers that send information to the brain for
processing. Conscious perception of tastes in food requires
olfactory and other sensations in addition to taste bud activity