In open circulatory system, the blood (i.e. hemolymph) bathes the organs and tissues directly. Examples of animals with open circulatory system are arthropods and most mollusks. In closed circulatory system, the blood circulates within blood vessels throughout the body. Therefore, there is a distinction between blood and lymph. Examples of animals with closed circulatory system are annelids, few mollusks, and vertebrates.
Its main task is the protection of the most important organ in the human body: the brain. The brain is almost entirely enclosed by the cerebral cranium with the exception of the foramen magnum and other foramina at the skull base which serve as entry and exit point for blood vessels and cranial nerves. The braincase consists of the skullcap (calvarium) and the skull base.
Axial Skeleton: Axial skeleton forms the axis of human body. It consists of Skull, vertebral column and thoracic cage. 1  Skull: Skull is that part of human skeleton that forms the bony framework of the head.2  It consists of 22 different bones that are divided into two groups: bones of cranium and bones of face.one is a tough and rigid form of connective tissue. It is the weight bearing organ of human body and it is responsible for almost all strength of human skeleton. For more details visit: Basic anatomy article; â Bone â.