There are many peripheral structures around the eye, such as eyebrows, eyelids, and eyelashes. The eye itself has three tunics. The outer is fibrous and contains collagen and elastin, such as the sclera or whites of the eyes, as well as the cornea. The middle (vascular) tunic contains the choroid, iris, pupil, lens, ciliary bodies, suspensory ligaments, and vitreous humor. The inner (neural) tunic contains the retina, photoreceptors, macula (optic nerve), and optic disc. Ocular lenses can be concave or convex and require glasses or surgery to focus light properly. The photoreceptors include rods and cones (cones help differentiate colors). Visual information proceeds from the eyes to the occipital lobe in the brain via the optic nerve. Vision disorders and conditions include night blindness, astigmatism, cataracts, and glaucoma.
The eye has numerous accessory structures that help it work and be protected: eyebrows, eyelids, eyelashes, skeletal eye muscles, conjunctiva, lacrimal glands, and orbital fat
The outer (fibrous) tunic of the eye includes the sclera and cornea (with the aqueous humor just posterior to the cornea)
The middle (vascular) tunic of the eye includes the choroid, iris, pupil, lens, ciliary bodies and suspensory ligaments
The inner (neural) tunic of the eye includes the retina (with photoreceptors), the vitreous humor, and the optic nerve
The blind spot is the part of the retina on top of the optic nerve exit that has no photoreceptors
Accommodation (the act of focusing) occurs because of actions of the lens, it gets more concave for focusing far away and more convex for focusing up close
Problems with accommodation include various degrees of myopia and hyperopia
Photoreceptors (rods and cones) contain bipolar cells, an inner segment, outer segment, and pigmented epithelium
Stereoscopic vision allows our visual fields to overlap, giving us depth perception
The optic chiasma, optic tracts, and occipital lobes are all involved in the optic pathways from the eyes to the brain
Vision conditions/problems include cataracts, glaucoma, astigmatism, and retinitis pigmentosa
Did you know…
Q: I’ve heard that some people can “see” sounds. How does that happen?
A: It’s called synesthesia, a disorder in which parts of the brain that interpret stimuli from the 5 senses are intimately connected within neuronal networks rather than segregated to different areas. Studies suggest that it is natural in infants for these parts of the brain to be wired together (perhaps hearing their mother’s voice may bring visions of glowing sunshine!) but as we age, the parts of the brain get separated as certain neurons in the brain die off. People with synesthesia may go to a dance club and see colors associated with various noises…maybe a black square appears every time they hear a deep bass drum beat. The precise sensations in these individuals vary from person to person. One person may hear the word “Friday” and see purple and another might see orange with the same word.
Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.
This book is the ninth edition of the top-selling Human Anatomy & Physiology text and the authors have produced the most accessible, comprehensive, up-to-date and visually stunning anatomy & physiology textbook on the market.. It presents information in smaller and more digestible bites, making it easier to read and navigate.
This book has a superb balance between structure and function and continue to emphasize the correlations between normal physiology and pathophysiology, normal anatomy and pathology, and homeostasis and homeostatic imbalances. The acclaimed illustration program continues to be refined and is unsurpassed in the market. The thirteenth edition is fully integrated with a host of innovative electronic media, including WileyPlus 5.0 (access purchased separately.) No other text and package offers a teaching and learning environment as rich and complete.
This book includes updated examples, references, and dozens of illustrations. Readers of the new edition will come to understand the meanings of terms in anatomy and physiology, get to know the body's anatomical structures, and gain insight into how the structures and systems function in sickness and health. It also features updated information on how systems function in illness and in health.