Papillae systems

Taste-active chemicals react with receptors on the surface of sensory cells in the papillae causing electrical depolarization, ie, drop in the voltage across the sensory cell membrane. The collection of biochemical events that are involved in this process is called transduction (15,16). Not all the chemical steps involved in transduction are known however, it is clear that different transduction mechanisms are involved in different taste quaUties different transduction mechanisms exist for the same chemical in different species (15). Thus the specificity of chemosensory processes, ie, taste and smell, to different chemicals is caused by differences in the sensory cell membrane, the transduction mechanisms, and the central nervous system (14). 

The renal system consists of the kidneys and their vasculature and innervation, the kidneys each draining through a ureter into a single median urinary bladder, and the latter draining to the exterior via a single duct, the urethra. The kidney has three major anatomical areas the cortex, the medulla, and the papilla. 

Figure 3. Location of some oral chemosensory receptor systems. Taste buds (schematic upper right) are found on specialized papillae on the tongue and scattered on the palate and posterior oral structures. Free nerve endings are found...

Studies on human taste sensations confirm and extend our understanding of the types of chemical signals measured by these oral chemoreceptor systems. There are, for instance, several distinct sensations elicited by chemical stimulation of fungiform papillae innervated by the geniculate ganglion, indicating that a neural functional complexity similar to that described above for... 

The papilla is the smallest anatomical portion of the kidney. Papillary tissue consists primarily of terminal portions of the collecting duct system and the vasa recta. Papillary blood flow is low relative to cortex and medulla less than 1% of total renal blood flow reaches the papilla. However, tubular fluid is maximally concentrated and the volume of luminal fluid is maximally reduced within the papilla. Potential toxicants trapped in tubular lumens may attain extremely high concentrations within the papilla during the process of urinary concentration. High intraluminal concentrations of potential toxicants may result in diffusion of these chemicals into papillary tubular epithelial and/or interstitial cells, leading to cellular injury. 

The palpebral conjunctiva is composed of nonkera-tinized stratified epithelium that decreases in thickness as it proceeds from the eyelid margin. Many mucin-secreting goblet cells are located near the fornix. The epithelium overlies the substantia propria, which consists of delicate connective tissue and blood vessels. Most of the immune system cellular components reside in the substantia propria.The stroma contains lymphocytes, lymphoid follicles, neutrophils, plasma cells, and mast cells, all of which proliferate extensively in conjunctival inflammatory disease. This proliferation leads to the formation of papillae and follicles. 

Systemic disorders may also manifest with conjunctival inflammation. Acute or chronic conjunctivitis may present with any of five signs of conjunctival inflammation chemosis, hyperemia, discharge or exudate, follicles, and papillae (Table 25-1). Specific patterns of inflammation may be helpful in diagnosis of the underlying cause. 

These diseases involve the renal tubules and their surrounding interstitial tissue. The presentation may be acute and reversible with interstitial inflammatory cell infiltrates, rapid loss of renal function, and systemic symptoms or chronic and irreversible with interstitial fibrosis, slow loss of renal function, and no systemic symptoms. Papillary necrosis, a variant of chronic interstitial nephritis, originates deep in the renal medulla and papillae. 

The excretory part of the nasolacrimal drainage system consists of the lacrimal puncta the superior, inferior, and conunon canaliculi the lacrimal sac and the nasolacrimal duct. In humans, the two puncta are the openings of the lacrimal canaliculi and are situated on an elevated area known as the lacrimal papilla. It is thought that tears are largely absorbed by the mucous membrane that lines the ducts and the lacrimal sac only a small amount reaches the nasal passage. 

The papilla is closely connected to the body by means of the blood circulation, the lymph system, and the extracellular fluid during the anagen growth phase. Not only the components of the hair but also the trace elements that are present are fed into the hair at the concentrations they have at that time and incorporated into the body of the hair. 

In the region of the root each hair follicle is surrounded by a system of capillary blood vessels that maintains a constant information exchange between the root and the rest of the body. The narrowing of a capillary can be a threat to the life of the hair-follicle when the arterial supply to the vascular loop of the papilla breaks down the hair follicle begins to die off, but remains anchored in the scalp for some months. After certain intoxications the dead hair root exhibits substance-specific alterations (Figs. 5 and 6). 

Randall VA et al (1991) Androgens and the hair follicle. Cultured human dermal papilla cells as a model system. Ann N Y Acad Sci 642 355-375... 

---