Planarians: Circulatory System Analysis

Planarians are triploblastic acoelomates, meaning they have three tissue layers, ectoderm, mesoderm, and endoderm (Newmark and Alvarado, 2001). Their epidermal layer that surrounds the planarian is ciliated on the ventral surface (Newmark and Alvarado, 2001). Underneath the epidermal layer and the basal lamina, followed by a complex wall musculature that surrounds the body. The complex wall muscle is composed of the circular diagonal and muscle fibers (Newmark and Alvarado, 2001). The nervous system contains two ventral nerve cores. The nerve cores are aggregated in the anterior part of the planarian to form the cerebral ganglia that are connected to two ventral longitudinal nerve cords, which are interconnected with the lateral commissures, and a submuscular nervous plexus (Newmark and Alvarado, 2001, Wenemoser, 2011). The function of the cerebral ganglia is to process information that was received from the sensory structures (Newmark and Alvarado, 2001). Examples are; photoreceptors, rheoreceptors, and chemoreceptors (Newmark and Alvarado, 2001). Planarians, do not have a circulatory system or respiratory structures, their gas exchange relies completely upon diffusion to provide them with the required amount of oxygen (Newmark and Alvarado, 2001, Wenemoser, 2011). …show more content…
Inside the planarian the space between the organs is filled with a solid mass of tissue called parenchyma (Wenemoser, 2011). These, tissue mainly consists of types of differentiated cells, such as different types of gland cells, and many undifferentiated cells, such as neoblasts (Wenemoser, 2011). Planarians have two forms of reproduction; asexual reproduction by fission, and sexual reproduction involving a male partner (Newmark and Alvarado,