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.
The skull base is the caudal boundary of the cerebral cranium. Looking at it from the inside it can be subdivided into the anterior, middle and posterior cranial fossae. The skull base comprises parts of the frontal, ethmoid, sphenoid, occipital and temporal bones. The face is referred to as all skull bones fronto-caudally connected to the cerebral cranium. Prominent representatives are the maxilla (upper jaw) and the mandible (lower jaw).
The skull is the part of the skeleton that covers and protects the brain and other sense organs. The human skull is composed of 22 types of bones. These bones are separated into two categories, the bones the form the cranium and facial bones.The section of the brain that holds the brain is known as the cranium.The cranium is made up of eight flat bones that are connected. The cranium bones form the forehead and eye socket and the back of the skull.The facial bones include fourteen bones, the majority of them symmetrical to give the face symmetry. The facial bones include bones such as the maxilla, which is the upper jaw and the nasal bone.he cranium bones form the forehead and eye socket and the back of the skull. The facial bones include fourteen bones, the majority of them symmetrical to give the face symmetry. The facial bones include bones such as the maxilla, which is the upper jaw and the nasal bone.