The sinoatrial SA node in the wall of the right atrium is the cardiac pacemaker it generates about action potentials per minute Gap junctions between adjacent cells allow action potentials ...

Chambered nautilus, one of six living nautilus species. The shell consists of many gas-filled chambers. The numerous tentacles do not have suckers.

After a female crab has mated she fertilizes eggs with stored sperm and then holds them under her abdomen for months until they hatch Within an hour of hatching an ...

Taste buds are clusters of receptor cells and supporting cells inside special epithelial papillae One type a circular papilla is shown in the section here The tongue has about taste ...