md0006 - BASIC HUMAN ANATOMY.pdf - Raems.com

52. The outermost layer of the eyeball is colored white and is made up of very dense
FCT; it is known as the sclera, scleral coat, or fibrous tunic. Its anterior portion is
called the cornea. The major focusing device for the eyeball is the cornea.
(para 11-27b(1))
53. The middle layer of the wall of the eyeball is known as the choroid, choroid coat, or
vascular tunic. This layer is richly supplied with blood vessels and pigmented with
a black material. (para 11-27b(2))
54. The inner layer of the wall of the eyeball is known as the retina, retinal coat, or
internal tunic. The actual photoreceptor elements are located at the back and the
sides. These elements are the rods and the cones. (para 11-27b(3))
55. The elements which register colors are the cones. However, cones require more
intense light than do rods. Rods register only black and white. (para 11-27c(1)(a))
56. The fovea centralis is a small depression at the posterior end of the eyeball
opposite the pupil. The macula lutea is a small yellow area of the retina where
vision is sharpest. It includes the fovea centralis. (para 11-27c(1)(b))
57. The blind spot is the point of exit of the optic nerve, at the posterior end of the
eyeball where there are no rods and cones. (para 11-27c(1)(c))
58. The thickening of the choroid layer around the edge of the lens is called the ciliary
body. It includes radial muscle fibers making up the ciliary muscle.
(para 11-27c(2))
59. The lens is biconvex. The anterior surface is flatter than the posterior surface.
The lens is transparent and elastic. Its thickness varies with contraction or
relaxation of the ciliary muscle. Accommodation is the process in which close
objects are seen more clearly; it involves contraction of the ciliary muscle,
reduction in pupil size, and convergence of the lines of sight. (para 11-27c(4))
60. The space between the cornea and the iris is called the anterior chamber. The
space between the iris and the lens is called the posterior chamber. Together,
these make up the space between the cornea and the lens called the anterior
cavity and filled with the aqueous humor. This drains into the encircling canal of
Schlemm, located in the angle between the cornea and the iris. Behind the lens is
a jellylike material called the vitreous body. It fills the posterior cavity of the
eyeball. (para 11-27c(6), (7))
61. The orbit is the cavity in the upper facial skull which contains the eyeball and its
adnexa. The orbit is shaped roughly like a cone. (para 11-28a)
MD0006 11-58