Specialized organelle found in Giardia species (trophozoite stage) and characterized by a spiral array of microtubules and microtubule-associated structures including dorsal microribbons and crossbridges. The edge of the ventral disc narrows into a lateral crest. The ventral disk mediates mechanical attachment of the trophozoite to the host's intestinal wall, and contains the contractile proteins actinin, alpha-actinin, myosin, and tropomyosin working towards contraction of the disk involved in adherence. [ https://www.worldcat.org/search?q=bn%3A9780124260207 http://www.ncbi.nlm.nih.gov/pubmed/4777416 http://www.ncbi.nlm.nih.gov/pubmed/11432808 http://www.ncbi.nlm.nih.gov/pubmed/5961344 ]