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Pedipalps contain sensitive chemical detectors and function as taste and smell organs, supplementing those on the legs. [2] In sexually-mature male spiders, the final segment of the pedipalp, the tarsus, develops a complicated structure (sometimes called the palpal bulb or palpal organ) that is used to transfer sperm to the female seminal ...
Palpal bulbs are believed to have evolved from the claws of the male pedipalp. Prior to the male's final moult, the bulb develops from cells at the base of where the claw would be. The transformation of claws to bulbs occurred before the evolution of all living spiders. [ 2 ]
The cephalothorax, also called prosoma, is composed of two primary surfaces: a dorsal carapace and a ventral sternum.Most external appendages on the spider are attached to the cephalothorax, including the eyes, chelicerae and other mouthparts, pedipalps and legs.
Somite 2 has a pair of pedipalps that in most sub-groups perform sensory functions, while the remaining four cephalothorax segments (somite 4 to 6) have pairs of legs. [10] In basal forms the ocular somite has a pair of compound eyes on the sides and four pigment-cup ocelli ("little eyes") in the middle. [ 12 ]
Tactile corpuscles are encapsulated myelinated nerve endings, [3] surrounded by Schwann cells. [3] The encapsulation consists of flattened supportive cells arranged as horizontal lamellae surrounded by a connective tissue capsule. The corpuscle is 30–140 μm in length and 40–60 μm in diameter.
The Merkel cell expresses the PIEZO2 mechanosensitive ion channels; mechanical activation of the channel causes depolarisation of the Merkel cell and consequent release of [1] serotonin into a synapse with the associated nerve ending, to also depolarise the later. [3] The nerve ending meanwhile expresses an unknown mechanosensitive channel. [1]
Merkel cell. Merkel cells are found in the skin and some parts of the mucosa of all vertebrates. In mammalian skin, they are clear cells found in the stratum basale [2] [3] (at the bottom of sweat duct ridges) of the epidermis approximately 10 μm in diameter. They are oval-shaped mechanoreceptors essential for light touch sensation and found ...
Illustration of Bowman's capsule, and glomerular capillaries wrapped by podocytes. A podocyte has a complex structure. Its cell body has extending major or primary processes that form secondary processes as podocyte foot processes or pedicels. [6]