Body Systems Preparation 2

We learned human eyes are spherical organs. Six small muscles attach the eye to the socket. According to Chiras(2013) “The wall of the human eye consists of three layers. The outermost is a durable, fibrous layer, which consists of the white off the eye(sclera). In front, this layer is clear and forms the cornea. The cornea lets light into the interior of the eye. The middle layer consists of cells containing a large amount of a dark pigment, known as melanin. In front, the pigmented layer forms the iris, the colored portion of the eye visible through the cornea. Looking in a mirror; you can see a dark opening in the iris called the pupil. The pupil allows light passing through the cornea to enter the eye. The blackness you see through the pupil is the pigmented region, just mentioned, and the pigmented section of the retina, discussed shortly. The iris contains smooth muscle cells. These cells contract and relax to adjust the amount of light entering the eye. When it is dark, for example, the muscles relax, which allows the pupils to dilate so more light enters. In bright light, just the opposite occurs. The innermost layer of the eye is the retina. The retina consist of an outer, pigmented layer and an inner layer consisting of photoreceptors. The photoreceptors of the retina are highly modified nerve cells that detect light. Two types of photoreceptors are present in the retina; rods and cones. The rods, so named because of their rod-like shape, are sensitive to low light. They function at night or in dim light and produce grayish, somewhat indistinct black-and-white images. The cones, also named because of their shape, operate only in brighter light. They are responsible for sharp vision as well as color vision (p. 81).
We found the urinary system to be quite interesting. The kidneys have a filtration unit