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Mammals excrete urine through the urinary system. Excretion is elimination of metabolic waste, which is an essential process in all organisms. In vertebrates, this is primarily carried out by the lungs, kidneys, and skin. [1] This is in contrast with secretion, where the substance may have specific tasks after leaving the cell.
The Type IV secretion system (T4SS) is the general mechanism by which bacterial cells secrete or take up macromolecules. Their precise mechanism remains unknown. T4SS is encoded on Gram-negative conjugative elements in bacteria. T4SS are cell envelope-spanning complexes, or, in other words, 11–13 core proteins that form a channel through ...
Sweat glands in the skin secrete a fluid waste called sweat or perspiration; however, its primary functions are temperature control and pheromone release. Therefore, its role as a part of the excretory system is minimal. Sweating also maintains the level of salt in the body. Mammals excrete sweat through sweat glands in the skin throughout the ...
Sweat glands are a type of exocrine gland, which are glands that produce and secrete substances onto an epithelial surface by way of a duct. There are two main types of sweat glands that differ in their structure, function, secretory product, mechanism of excretion, anatomic distribution, and distribution across species:
Sebaceous glands secrete the skin lubricant sebum. Sebum is secreted onto the hair shaft and it prevents the hair from splitting. It consists mostly of lipids. After the sebum spreads along and up the hair shaft, it is distributed over the skin surface where it lubricates and waterproofs the outer layer of the skin, the stratum corneum. [1] [2]
In Madagascar, some gecko species in the genera Phelsuma and Lygodactylus are known to approach flatid plant-hoppers on tree-trunks from below and induce them to excrete honeydew by head nodding behaviour. The plant-hopper then raises its abdomen and excretes a drop of honeydew almost right onto the snout of the gecko.
Merocrine – the cells of the gland excrete their substances by exocytosis into a duct; for example, pancreatic acinar cells, eccrine sweat glands [dubious – discuss], salivary glands, goblet cells, intestinal glands, tear glands, etc. Apocrine – the apical portion of the cytoplasm in the cell membrane, which contains the excretion, buds off.
Sympathetic postganglionic neurons typically secrete norepinephrine and are named sympathetic adrenergic neurons; however, the sympathetic postganglionic neurons that innervate sweat glands secrete acetylcholine and hence are termed sympathetic cholinergic neurons. Sweat glands, piloerector muscles, and some blood vessels are innervated by ...