We learn that the equator is a line around the wide waist of the world. Pleasure cruisers often make a great toâdo about crossing this line on the ocean. Any passenger who owns up to the fact that this is his first crossing may be put through ceremonies such as walking the plank and other merry goingsâon.
Ectoderm â Outer or External Layer â differentiates into the nervous system, epidermis, and the outer part of the integument system â forms the central nervous system, the lens of the eye, cranial and sensory, the ganglia and nerves, pigment cells, head connective tissues, the epidermis, hair, and mammary glands.
Overview. The central nervous system consists of the brain and the spinal cord. The peripheral nervous system consists of the extensions of neural structures beyond the central nervous system and includes somatic and autonomic divisions.ross Anatomy: Meninges. The meninges consist of 3 tissue layers that cover the brain and spinal cord: the pia, arachnoid, and the dura mater (see the image below). The pia along with the arachnoid are referred to as the leptomeninges, whereas the dura is referred to as the pachymeninx.