Culcita novaeguineae, like all echinoderms, has a water vascular system (WVS) which is essentially a network of fluid filled canals (Hickman et al. 2008). These canals are lined with cilia which creates internal counter currents. This system is utilised in respiration and internal transport. The WVS operates hydraulically and is an effective locomotor system. This system connects to the external tube feet. Star fish often use this pathway to excrete waste, migrating unwanted material to a single tube foot which is then pinched off and expelled (Hickman et al. 2008).
The cushion star's mouth on the oral side leads through a short oesophagus to a large stomach located in the central disc (Hickman et al. 2008). Like other Asteroids, this species has a ciliated cardiac stomach. During feeding this stomach can be everted for external digestion of prey (Hickman et al. 2008, Other feeding experiments). Digestion is mostly extracellular (Hickman et al. 2008). The anus of cushion stars is relatively inconspicuous, although can be seen under magnification.
The hemal system of asteroids is relatively underdeveloped and its function is not well known (Hickman et. al. 2008). It has little to do with the circulation of body fluids and appears to have some role in absorbing nutrients after feeding (Hickman et al. 2008).
The nervous system of this species consists of an oral (ectoneural) system, a deep (hyponeural) system, and an aboral system. The oral system contains a nerve ring around the mouth and a main radial nerve extending into each arm. The deep system lies aboral to the oral system, and the aboral system contains a ring around the anus, with further radial nerve extensions (Hickman et al. 2008).
Gonads of cushion stars lie in the interradial space in each arm (Hickman et al. 2008).