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The Eye and The Endocrine System Eymi Hu-Tun Period 5 (Major Structures…
The Eye and The Endocrine System Eymi Hu-Tun Period 5
Major Structures and Functions of the Eye
Sclera- fibrous "white" part of eye
Choroid- dark pigment layer (under the sclera)
Cornea- transparent covering
Pupil- opening that lets light into eye; colored part of eye
Iris- circular muscle: controls the size of pupil
Lens- focuses light rays onto fovea
Ciliary Body (muscle)- controls shape of lens
Aqueous Humor- water fluid behind cornea (anterior to lens)
Vitreous Humor- jelly like fluid maintains eyeball shape
Retina- layer of sensory receptor cells
Fovea- small depression with high concentration of cones
Optic Disc- region with no receptors, receptors connect to optic nerve
Conjunctive- mucous membrane covering the front surface of the sclera and lining eyelid
Diseases associated with the eye
Cataracts- clouding of the eye; lens hardens & becomes opaque
Glaucoma- drainage of the aqueous humor is blocked; damage to the optic nerve will eventually lead to blindness
Astigmatism- unequal curvatures in different parts of the cornea or lens leads to blurry images
Hyperopia (farsightedness)- parallel light rays from distant objects are focused behind the retina; see distant objects but close objects appear blurry
Myopia (nearsightedness)- distant objects are focused in front of the retina; can see close objects but distant objects appear blurry
Color Blindness- lack of one or more cone type; inherited by x-linked condition; common in males then females
Conjunctivitis- inflammation of the conjunctiva usually from bacteria or viral infection
Functions of the Endocrine System
Hormones diffuse into the bloodstream to act on specific target cells
Regulate a number of metabolic processes
Their actions are precise
Hormones can influence the target cells even if they are present only in minute concentrations
Steroid Hormones signal the cell to make specific proteins
Non-steroid Hormones triggers a cascade of reactions inside the cell
Negative Feedback systems control hormonal releases
Major glands & their functions
Hypothalamus- serves many different functions and is responsible for the direct control of the endocrine system through the Pituitary Gland
Pituitary Gland- blood vessels surround the gland to carry hormones it releases throughout the body
Posterior Pituitary- axons of some of the neurosecretory cells of the hypothalamus extend; create 2 hormones that are stored and released
Anterior Pituitary- releases and inhibits hormones from the hypothalamus; produces 6 important hormones
Pineal Gland- porduces hormone melatonin that helps regulate the human sleep-wake cycle
Thyroid Gland- Produces 3 major hormones
Parathyroid Gland- produces the hormone parathyroid hormone, which is involved in calcium ion homestasis
Adrenal Gland-