SLE204 Lecture Notes - Lecture 9: Aortic Arches, Flatworm, Planaria

• School: Deakin University
• Department: Science, Engineering and Built Environment
• Course: SLE204
• Professor: Anneke Veenstra

Document Summary

Phylum platyhelminthes flatworms: acoelomate no coelom, 3 germ layers triploblastic. Middle = mesoderm muscles & organs formed here. Inner = endoderm lining of digestive tract: mesoderm allows development of organs e. g. excretory, reproductive. Outer = epiderm (ectoderm) organs: may have mouth (on ventral surface); no anus inefficient digestive system. Endoparasitic (internal parasite -> usually small so can move around in blood vessels or lymph of the host) Free-living in aquatic or moist terrestrial environments. Digestive system: endodermal layer gives rise to digestive system. Undigested food exits via mouth -> not very efficient molecules through their tegument. Mesodermal layer: muscles: circular, longitudinal and diagonal, parenchyma: fill spaces between muscle fibres, reproductive structures: contained in proglottids. Excretion & osmoregulation: protonephridia (cid:523)(cid:498)flame cells(cid:499)(cid:524) simplest of excretory/osmoregularity systems kidney structure, remove excess water, action: Beating flagella of flame cells creates negative pressure. Reproduction: asexual: by fission: split in half and regenerate missing half, sexual: