What are the 3 layers of the eyeball?
the fibrous tunic, vascular tunic, and the retina
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| Term | Definition |
|---|---|
| What are the 3 layers of the eyeball? | the fibrous tunic, vascular tunic, and the retina |
| the fibrous tunic consists of what? | the sclera (the white of the eye) and the cornea (where the light passes to enter the eyeball) |
| the vascular tunic consists of what? | the ciliary body (the muscle that attaches to the lens, causing it to change shape), the iris (the colored portion of the eye, conrols the opening of the eyeball), the lens, and the pupil |
| what is the vascular tunic made up of? | choroid connective; supplies blood flow to the eyeball |
| the retina consists of what? | the macula lutea (the yellow spot), the fovea centralis (the point of sharpest focus in the eye), the optic disc (where the optic nerve/"the blind spot" and the retina's main artery and vein enter the back of the eye ) |
| What are the two chambers of the eyeball? what are they filled with? | the anterior chamber and the posterior chamber. they are filled with fluid to maintain the eyeball's shape but allow light to pass through them |
| Where is the anterior chamber? what does it hold? | It's the space between the cornea and the lens. it's filled with a watery substance called the aqueous humor |
| Where is the posterior chamber? what does it hold? | it's the larger space behind the lens that fills the eyeball back to the retina. it's filled with a thicker, gel-like substance called the vitreous humor |
| What are the accessory features of the eye? | the eyebrows, eyelashes, eyelids, and the conjunctiva |
| the eyebrows do what to protect the eye? | they help to protect the eye from liquids or debris entering the eye and provide a cover from direct sunlight exposure to some degree. |
| the eyelashes do what to protect the eye? | They protect the eye by catching foreign particles and dust to prevent them from entering the eye and shield the eye from intense light. |
| the eyelids do what to protect the eye? | they shield the eye but also lubricate the eye and remove any foreign material through the blinking motion. |
| what is the conjunctiva dn what does it do to protect the eye? | is a thin membrane that lines the inside of the eyelid and covers the sclera. It distributes fluid to help lubricate the eye, protect it from microbes, and play a role in the immune response to germs that make their way into the area around the eye. |
| conjunctivitis is what? | an inflammatoin or irritation of the sensitive lining |
| what does the lacrimal system do? | it helps produce and drain lacrimal fluid, or tears, around the eyes. |
| what do tears do? | they lubricate the conjunctiva and the cornea and flush away dust and debris that might enter the eye. they are primarily water and salts but also contain antimicrobial enzymes to help safeguard the eye from germs. |
| what is the general process of crying? | The lacrimal glands are located on the superior lateral margin of the eye orbit. These produce tears that travel through the lacrimal ducts to the medial corner of the eyes, where they enter the lacrimal canaliculi, tunnels that collect the tears and lead to the lacrimal sac. The seventh cranial nerve, or facial nerve, controls the release of tears through the lacrimal duct into the corner of the eye and the nasal cavity when needed. |
| Which facial nerve controls the release of tears through the lacrimal duct into the corner of the eye and the nasal cavity when needed? | the seventh cranial nerve |
| what are the six eye muscles that surround the eye to help with movement? | the superior rectus m., inferior rectus m., medial rectus m., lateral rectus m., superior oblique m., and the inferior oblique m. |
| what does the superior rectus m. do? | rolls or lifts the eye upward. It is located above the eye and is controlled by the oculomotor nerve (cranial nerve III). |
| what does the inferior rectus m. do? | moves the eye downward. It is located inferiorly on the eyeball and is also controlled by the oculomotor nerve (cranial nerve III). |
| what does the medial rectus m. do? | moves the eye closer to the nose. It is located medially on the eyeball and is controlled by the oculomotor nerve (cranial nerve III). |
| what does the lateral rectus m. do? | moves the eye laterally or away from the nose. This allows you to look out of the corner of the eye toward the periphery. It is located laterally on the eyeball and is controlled by the abducens nerve (cranial nerve VI). |
| what does the superior oblique m. do? | rotates the eye downward, medially, and laterally. it's located under the superior rectus m. and is controlled by the trochlear nerve (cranial nerve IV). |
| what does the inferior oblique m. do? | lifts the eye and rotates it medially and laterally. its located under the lateral rectus m. and is controlled by the oculomotor nerve (cranial nerve III). |
| what is the general physiology of sight? | light strikes the cornea, its shape bens the light to focus -> light passes through the pupil -> dilation occurs when the pupil enlarges to allow more light to enter the eye or pupillary constriction occurs when the pupil contracts to limit the light that enters the eye -> the light passes through the lens and is refracted/bent so the light focuses on the focal point of the rentina (the fovea centralis), in the macula lutea -> adjustments are made to the lens by the ciliary body (adjusting the light to the correct refraction) -> when light hits the retina, photorecpetors are stimulated and transmit the signal to the brain through the optic nerve -> the impulses are converted into images and are decoded and processed in the occipital lobe (because the cornea and lens bend the light, the image the brain receives is upside down and must be turned right-side up as the brain interprets it) |
| The process known as accommodation does what? | it contracts or flattens the lens for proper focusing of the eye. For close objects, the ciliary muscles contract, making the lens more circular. When objects are farther away, the ciliary muscles relax, flattening out the lens. |
| the process known as convergence does what? | when the eyes simultaneously rotate medially to help focus while the pupils constrict to allow for better focus on a subject closer to the eye |
| what is refraction? | the bending of light |
| what are the four refractory structures in the eye? | the cornea, the lens, the aqueous humor, and the vitreous humor |
| what direction does refraction flip the image casted on the retina? | vertically |
| what are the two types of photoreceptors? | rods and cones |
| where are rods located and what do they do? | they are located in the eye's periphery, they contain the pigment rhodospin. they are responsible for low-light and night vision but do not react to or transmit wavelengths of color (estimates suggest that there are approximately 90 million rod cells in the retina of each eye). |
| where are cones and what do they do? | they are concentrated in the macula, and they perceive color. they are less sensitive than rods and tend to be activated in brighter light. |
| what are the three varieties of cones that respond to the wavelength based on the opsin pigment they contain? | 1. L cones (long wavelength) detect red light 2. M cones (medium wavelength) detect green light 3. S cones (short wavelength) detect blue light |
| what is emmetropia? | "normal vision" |
| what does it mean to have "20/20 vision?" | this means you can see what the average person sees from tewenty feet away (someone with 20/40 vision can see at twenty feet what the average person sees from forty feet away) |
| Myopia is... | "near-sightednes", its when someone has trouble viewing objects far away. This occurs because the light inside the eye focuses in front of the retina rather than on it. |
| Hyperopia is... | "far-sightedness", it's when someone has trouble viewing objects close to them. This is caused by the light in the eye not focusing on the retina but focusing behind it, causing it to be blurry. |
| Presbyopia is... | "the hardening of the lens", the lens loses flexibility and can no longer change its shape and focus on close objects, resulting in blurry vision. |
| Monochromacy or achromatopsia is... | a complete lack of color |
| Cataracts is... | the deterioration of the lens in the eye. Someone with cataracts will notice that their vision becomes cloudy or blurry because proteins in the usually clear lens break down and clump together. This prevents light from passing through the lens, obscuring the vision. |
| Glaucoma is... | buildup of pressure in the eye's fluid, increasing the intraocular pressure, due to a problem with the normal drainage system of the eye. this can damage the optic nerve, resulting in the loss of vision |
| Astigmatism is... | an irregularity in the curvature of the cornea or lens in the eye. This may cause blurry vision close up and/or far away. |
| what is macular degeneration? | this happens when the macula of the retina begins to break down. Because of the location of the macula, the person will experience loss of sight starting in the center of the field of vision. |
| what is audition? | the process of hearing |
| what are the three sections the ear is divided into? | the outer, the middle, and the inner |
| what does the outer ear do? | it collects sound waves and moves them into the middle ear. |
| what does the outer ear consist of? | the auricle/pinna, external auditory canal, tympanic membrane, and the ceruminous glands |
| what is the auricle/pinna? | it's the visible structure on the outside of the head, commonly called "the ear." It is made of elastic cartilage covered with epithelial tissue. The helix of the ear is made of cartilage and forms the top or curve of the pinna. The lobe is the fleshy portion below the opening. The tragus is the tough, cartilaginous structure that protects the opening to the auditory canal. |
| what is the external auditory canal? | its a tunnel that sound waves travel into when going into the skull. it contains hair and ceruminous glands that produce cerumen/ ear wax that traps foreign object from going into the inner ear |
| what is the tympanic membrane/ "the eardrum"? | its a thin, transparent sheet of tissue that separates the outer ear from the middle ear. it vibrates when sound waves strike it to transmit these waves into the next section of the ear canal. |
| what does the middle ear do? | it begins on the inside of the tympanic membrane-- It is an air-fluid chamber that houses the auditory ossicles, eustachian tubes, and the oval window. |
| what is the eustachian tube? | its a canal in the skull that connects the middle ear to the nose and pharynx. with its numerous functions, it drains fluid from the middle ear into the nose and throat, equalizing pressure inside these chambers, and moving oxygen between the ear and the nose and throat. most recognized for its "pop" |
| what are the auditory ossicles? | they are the smallest bones of the body. they are responsible for transmitting sound vibrations through the middle ear. they consist of the malleus, the incus, and the stapes. |
| what is the malleus? | its shaped like a hammer and attaches to the tympanic membrane |
| what is the incus? | its shaped like an anvil and receives vibrations form the malleus and transmits them to the stapes |
| what is the stapes? | its shaped like a stirrup and it connects to the incus and the oval window leading to the inner ear |
| what is the oval window? | it spearates the middle ear from the inner ear. it's a membrane-covered opening that divides the two chambers and transmits the vibrations as they pass from the ossicles. |
| what does the inner ear do? | it begins at the oval window-- its a bony labyrinth (series of canals) that travel through the temporal bone. it's where the sound is processed for final transmission to the brain and it also plays a role in balance and coordination. |
| what does the inner ear consist of? | the cochlea, the vestibule, and the sumicircular canals (they are all filled with endolympth fluid; helps with hearing and equilibrium) |
| the three structures are encased in a system of sacs and tubules called what? | the membranous labyrinth |
| between the membranous labyrinth and the bony labyrinth is a layer of fluid called what? | perilymph; it plays a role in hearing, equilibrium, and the health of the cells in the inner ear. It also serves to cushion these soft structures within the bony chamber where they are found. |
| what is the general physiology of hearing? | (in the external ear) sound waves are collected by the auricle/pinna -> channeled to the external auditory canal -> vibrations move to the tympanic membrane, where it amplifies the vibrations -> (in the middle ear) the vibrations are communicated to the auditory ossicles -> (the inner ear) inside the bony labyrinth, the cochlea is responsible for hearing (the Organ of Corti is inside the cochlea that contains hair cells that stand up, surrounded by endolymph fluid) -> sound waves pass through the oval window -> transfered to fluid-filled tubes inside the cochlea that moves and matches the frequency of the sound waves -> the fluid bends the hairs in the Organ of Corti -> ion channels open, creating impulses sent to the brain through the vestibulocochlear nerve, cranial nerve VIII |
| the inner ear is also the location for what? | balance and equilibrium in the body |
| what is static equilibrium? | sensations about position when the body is at rest |
| what is dynamic equilibrium? | orientation when the body is moving horizontally or vertically |
| what does the vetibule of the inner ear contain? | two fluid-filled sacs called the saccule and utricle (which contain a membrane called the macula; this has hairs that are brushed by calcium carbonate crystals called otoliths that move with gravity and move the hairs. This send signals to the brain that make us aware of the change in the position of the head) |
| what are the semicircular canals? | three joined canals; they sense a particular direction of movement in the head based on their orientation. Structures called the ampulla and cupula move across one another, moving fluid in the canals that stimulates hairs as in the other inner ear structures. These send stimuli to the brain that detect motion. |
| what is conductive hearing loss? | it occurs in the outer or middle ear if the vibrations from the outside can no longer be passed through the ear |
| what is sensorineural hearing loss? | it occurs in the inner ear when the ability to transmit neural messages is lost in the cochlea |
| what is presbycusis? | The most common issue is gradual or sudden hearing loss; it's the breakdown of hair cells in the inner ear, which reduces the transmission of impulses to the brain. |
| what is olfaction? | the sense of smell |
| humans have about how many olfactory receptor subtypes? | 350 |
| "our sense of smell has a speed similar to that of __" | color perception |
| what are odorants? | air containing odor molecules |
| what is the nasal cavity called? | the nasopharynx |
| what is the olfactory epithelium? | its at the back of the cavity where odorants dissolve in the mucous |
| what is the physiology of smell? | odorants enter the nostrils -> travels to the nasopharynx as it passes the conchae -> odorants dissolve in the mucous of the olfactory epithelium (the mucosa contains specialized receptor neurons that allow for the vast array of scents to be detected) -> the dendrites of the neurons bind ot moleucles that, when inhaled, send impulses to the olfactory tract (cell axons) -> impulses are sent to the brain's olfactory bulb -> the smell is communicated directly to the brains olfatory region along the olfactory nerve (cranial nerve I). |
| what locations are associated with long-term memory and emotions? | the temporal lobe, the limbic system, and the hypothalamus |
| what is sensory adaptation? | a common phenomenon that states that by adapting to the smells in the environment, the olfactory system acclimates to those stimuli that are always around. This allows it to be attuned to new smells indicating danger or potential threat. This also protects the brain from sensory overload. Because of this, you may notice that your house smells different when you come home after a vacation, having been gone for a while. |
| what is anosmia? | a condidtion where you have no sense of smell |
| how is anosmia caused? | by injury to the olfactory nerve, if the brain's frontal lobe is harmed, or because of the effects of chemicals or drugs (many people suffered from temporary anosmia secondary to COVID-19 during the pandemic, losing their senses of smell and taste) |
| what is the band of tissue that anchors the tounge in the mouth called? | the lingual frenulum |
| what is the structure of the surface of the tongue? | it's lined by stratified squamous epithelium. Across the surface are the papillae containing specialized taste buds or gustatory receptor cells that detect taste sensations |
| what are the four types of papillae on the tongue based on their shape? | fungiform (mushroom shaped, contains most of the tastebuds), foliate (form ridges and grooves towards the posterior part and sides, contains hundred of taste buds in each foliate), circumvallate (10-14 on the tongue, "inverted oval"/ circular, arranged in a row towards the posterior region of the tongue, contains app. 250 taste buds each), and filiform ("v-shaped", don't contain taste buds, the most numerous, function in the sense of touch that allows use to feel the form and texture of foods) |
| what are the primary tastes detected by humans? | sweet, sour, bitter, salty, and unami (savory) |
| what is the link between taste and smell? | While chewing, food releases chemicals that are received by the microvilli on each taste bud and by the olfactory receptors in the nose. Both receptors work together to give the food's true flavor. |
| where does unami flavor often come from in processed foods? | monosodium glutamate (MSG) |
| what crnaila nerves are involved in the sense of taste? | the facial nerve, glossopharyngeal nerve, and the vagus nerve |