This simple diagram illustrates my present understanding of the relationship of the planes of the body as offered by the teachings of Rudolf Steiner. In this two-dimensional medium, the true nature of the concept, the gestalt, is, apologetically, underrepresented. So I leave it to your imagination to visualize it in a way that makes sense for you!
Here, the area designated as the "physical body" represents the human being. You can imagine the physical body plane in the diagram as the top of the head, the scalp. Extrapolate the diagram to a three-dimensional figure of the human form, rotate the figure around in space, and see it from all sides. The physical body is the mineral, the matter, the form, structure, flesh and blood, cellular, carbon-based, anatomical and physiological human being.
The etheric body takes the shape of the physical body, and extends just beyond it, closely approximating the body's contours. The etheric body generates the phenomena of life, hence it is referred to as the vital force or life force. In other cultures, it may be akin to the chi. In Star Wars, it is probably similar to the "Force" that the Jedis often speak of. The etheric body is three dimensional in shape, having a volume of its own, occupying the same space as the physical body, yet emanating just beyond the human skin. The etheric body, in the diagram, I would describe as a membrane of a sort, having a thickness. Within this etheric body are two distinct layers, a "coarse" etheric and a "fine" etheric. The coarse side penetrates into the physical body, while the fine side emanates to coalesce with another plane of the body: the sentient body.
The sentient body is unique to the human being in comparison to other organisms on earth. The sentient body, or astral body, is what gives the human his or her consciousness of self and of the environment. The sentient body recognizes the existence of the physical and etheric bodies. To me, the sentient body, because of its gift of consciousness, is what gives us interconnectedness to others and the external environment. (I think in some ways, the chi, and OK, forgive my movie reference again, the Force, also share similarities to the sentient body because I think through the sentient body, we are capable of manipulating our environment, or at least impacting on it to some degree.) In the diagram, the sentient body is tethered to the etheric body via the finer projections of the etheric milieu. The sentient body is affected by the etheric and physical bodies as they determine and restrict the sentient body.
Another layer depicted in the diagram is the sentient soul. According to spiritual science, we undergo transformation as part of our nature, and through the I body (not depicted in the diagram), the sentient body transforms into the sentient soul. Because our lives are dynamic and the processes are dynamic, the sentient body continually gives off more material to the sentient soul as this transformation occurs over our lifetime.
Now remember, I am synthesizing my learning process and as I get further along in my studies, and I have a feeling more concepts will follow, my understanding of the work may change, maybe it will be confirmed or totally rejected. My astral body is thinking that Steiner has more up his sleeves and we are only at the edge of the forest in the journey through anthroposophy.