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.
The cranium has several bones, 1 frontal, 2 parietal, 2 temporal, and 1 occiptal â¦ ; for a total of 6. They are soft and contain a lot of cartilage in early childhood, but later in adulthood, they are interconnected by joints called sutures. The main job of the skull is to house and protect the brain.owever, because the brain is floating in this fluid the skull can also act as a damaging wall as the brain slaps back and forth during head banging, car crashes, severe shaking and any other sort of sudden go and stop motion that effects the head.