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Eye and Endocrine, Diana Iniguez (structure and function of the eye…
Eye and Endocrine, Diana Iniguez
structure and function of the eye
Ciliary Body. The circumferential tissue (a ring of tissue between the end of the choroids and the beginning of the iris) inside the eye composed of the ciliary muscle (involved in lens accommodation and control of intraocular pressure and thus the shape of the lens) and 70 ciliary processes that produce aqueous fluid.
Vitreous Humour (Chamber) is the transparent, colorless gelatinous mass that fills rear two-thirds of the eyeball, between the lens and the retina. It has to be clear so light can pass through it and it has to be there or eye would collapse.
The lens is the natural lens of the eye (chrystaline lens). Transparent, biconvex intraocular tissue that helps bring rays of light to focus on the retina (It bends light, but not as much as the cornea). Suspended by fine ligaments (zonules) attached between ciliary processes. It has to be clear, has to have a power of about +16, and has to be pliable so it can control refraction
Pupil. It is a variable-sized black circular opening in the center of the iris that regulates the amount of light that enters the eye. The pupil needs to be round in order to constrict
The retina is the light sensitive nerve tissue in the eye that converts images from the eye’s optical system into electrical impulses that are sent along the optic nerve to the brain, to interpret as vision. Forms a thin membranous lining of the rear two-thirds of the globe; consists of layers that include two types of cells: rods and cones. There is no retina over the optic nerve which causes a blind spot (This is the sightless area within the visual field of a normal eye.
Iris
The iris is the pigmented tissue lying behind the cornea that gives color to the eye and controls the amount of light entering the eye by varying the size of the papillary opening. It functions like a camera. The color of the iris affects how much light gets in. The iris controls light constantly, adapts to lighting changes, and is responsible for near point reading
Choroid
The vascular (major blood vessel), central layer of the eye lying between the retina and sclera. Its function is to provide nourishment to the outer layers of the retina through blood vessels. It is part of the uveal tract.
The Cornea is the second structure that light strikes. It is the clear, transparent front part of the eye that covers the iris, pupil and anterior chamber and provides most of an eye’s optical power (if too flat = hyperopia/farsightedness; if too steep = myopia/nearsightedness). It needs to be smooth, round, clear, and tough. It is like a protective window. The function of the cornea is to let light rays enter the eye and converge the light rays
Sclera
The sclera is the opaque, fibrous, tough, protective outer layer of the eye (“white of the eye”) that is directly continuous with the cornea in front and with the sheath covering the optic nerve behind. The sclera provides protection and form.
The Optic Nerve is the largest sensory nerve of the eye. It carries impulses for sight from the retina to the brain. Composed of retinal nerve fivers that exit the eyeball through the optic disc, traverse the orbit, pass through the optic foramen into the cranial cavity, where they meet fibers from the other optic nerve at the optic chiasm.
Diseases associated with the eye
Cataract is a clouding of the eye’s lens and is the leading cause of blindness worldwide, and the leading cause of vision loss in the United States. Cataracts can occur at any age because of a variety of causes, and can be present at birth.
Macular degeneration, often called age-related macular degeneration (AMD), is an eye disorder associated with aging and results in damaging sharp and central vision. Central vision is needed for seeing objects clearly and for common daily tasks such as reading and driving.
Diabetic retinopathy (DR) is a common complication of diabetes. It is the leading cause of blindness in American adults. It is characterized by progressive damage to the blood vessels of the retina, the light-sensitive tissue at the back of the eye that is necessary for good vision
Refractive errors are the most frequent eye problems in the United States. Refractive errors include myopia (near-sightedness), hyperopia (farsightedness), astigmatism (distorted vision at all distances), and presbyopia that occurs between age 40–50 years
Major functions of the endocrine system
Hormones are secreted by the glands of the endocrine system, traveling through the bloodstream to various organs and tissues in the body. The hormones then tell these organs and tissues what to do or how to function.
The endocrine system is responsible for regulating a range of bodily functions through the release of hormones.
metabolism
growth and development
sexual function and reproduction
heart rate
blood pressure
appetite
sleeping and waking cycles
body temperature
Major glands/organs and their functions
The thyroid gland is located in the lower front part of the neck. It produces thyroid hormones that regulate the body's metabolism. It also plays a role in bone growth and development of the brain and nervous system in children. The pituitary gland controls the release of thyroid hormones
The parathyroid glands are two pairs of small glands embedded in the surface of the thyroid gland, one pair on each side. They release parathyroid hormone, which plays a role in regulating calcium levels in the blood and bone metabolism.
The pituitary gland is located at the base of the brain beneath the hypothalamus and is no larger than a pea. It is often considered the most important part of the endocrine system because it produces hormones that control many functions of other endocrine glands. When the pituitary gland does not produce one or more of its hormones or not enough of them, it is called hypopituitarism.
The pineal body, or pineal gland, is located in the middle of the brain. It secretes a hormone called melatonin, which may help regulate the wake-sleep cycle of the body.
The hypothalamus is located in the lower central part of the brain. This part of the brain is important in regulation of satiety, metabolism, and body temperature. In addition, it secretes hormones that stimulate or suppress the release of hormones in the pituitary gland. Many of these hormones are releasing hormones, which are secreted into an artery (the hypophyseal portal system) that carries them directly to the pituitary gland. In the pituitary gland, these releasing hormones signal secretion of stimulating hormones.
names of the hormones produced and their target organs
along with functions of the hormones
The posterior lobe produces the following hormones, which are not regulated by the hypothalamus:
Antidiuretic hormone (vasopressin): Controls water loss by the kidneys
Oxytocin: Contracts the uterus during childbirth and stimulates milk production
Thyroid Thyroxine (T4) and Triiodothyronine:Increase metabolic rate, regulates growth and development
The anterior lobe produces the following hormones, which are regulated by the hypothalamus:
Growth hormone: Stimulates growth of bone and tissue (Growth hormone deficiency results in growth failure. Growth hormone deficiency in adults results in problems in maintaining proper amounts of body fat and muscle and bone mass. It is also involved in emotional well-being.)
Thyroid-stimulating hormone (TSH): Stimulates the thyroid gland to produce thyroid hormones (A lack of thyroid hormones either because of a defect in the pituitary or the thyroid itself is called hypothyroidism.)
Parathyroids Parathyroid (PTH) Peptide Bones, kidneys and intestine Raises blood calcium level
Diseases associated with the endocrine system
type 1 diabetes (T1D) is an autoimmune condition in which the pancreas can no longer produce insulin to control your blood sugar naturally. So you need to take insulin in order to manage your blood sugar to remain healthy and avoid serious complications.
Diabetes mellitus refers to a group of diseases that affect how your body uses blood sugar (glucose). Glucose is vital to your health because it's an important source of energy for the cells that make up your muscles and tissues. It's also your brain's main source of fuel
Addison’s disease is a rare disorder that affects men and women of all ages. Addison’s disease is also referred to as primary adrenal insufficiency. Adrenal insufficiency develops when your adrenal glands do not produce enough of the hormone cortisol. This can be due to a problem within the adrenals (called Addison’s disease or primary adrenal insufficiency) or due to a problem with the signal the brain sends to the adrenals instructing them to make cortisol (called secondary adrenal insufficiency).
Adrenocortical carcinoma is a rare tumor afflicting only one or two persons per one million population. It usually occurs in adults, and the median age at diagnosis is 44 years. Although potentially curable at early stages, only 30% of these malignancies are confined to the adrenal gland at the time of diagnosis.