Chapter 15 & 16

- are located and confined to the head region.
- smell, taste, sight, hearing, and equilibrium
- NOT free endings of sensory neurons but receptor cells
- transfer sensory information via afferent pathways to the brain via cranial nerves.

- aka know as receptors for taste, they are considered "chemoreceptors" because they respond to chemical substances.

- aka taste cells, they are located on tongue in the epithelial cells.
- gustatory hairs project though the taste pore to the surface of the epithelium.
- replaced every 7-10 days by basal cells
- taste information reaches the brain via the facial nerve, glossopharyngeal nerve and vagus nerve.

- aka as smell senses
- classified as a chemoreceptors
- these cells lie in epithelium on the roof of the nasal cavity (nasal concha and nasal septum)
- pseudostratified columnar epithelium that contains millions of bipolar neurons called OLFACTORY RECEPTOR CELLS

- pseudostratified in shape, the are found in the epithelium of the nose.
- surrounded by supporting cells
- basal cells lie at the base.
- cilila in the olfactory are immotile
- has an axon that enters the connective tissue of the lamin propria.

- most external layer, consists of dense connective tissue arranged into two diff. regions: Cornea and Sclera.
- Sclera, white, tough froms the posterior of the fibrous layer.
- protects the eyeball and provides shape.
- Cornea, light enters though, richly supplied with nerve endings where pain is can be located.
- sandwhiched between a corneal epithlium and corneal endothelium.
- Limbus, is the junction between the cornea and the conjunctiva. Here, the epithelial stem ceels are continually renewed.

- vascular layer, is the middle coat of the eyeball has 3 parts: the iris, choroid and the ciliary body.
- Choroid, is hightly vascular, darkly pigmented membrane that forms the posteror five sixths of the vascular layer. has many blood vessesl that nourish the other layers of the eye. brown color of the choroid is produced by melanocytes.
- ciliary body, is a thickedned ring of tissue that encircles the lens. consists chiefly of smooth muscle called the ciliary muscle, which acts to focus the lens.
- ciliary zonule, area where fine fibrils extends from the ciliary processes to attach around the entire circumference.
- iris, is the visble, colored part of the eye. It lies between the cornea and lens, and its base attaches to the ciliary body.

- inner layer have the retina and optic nerve.
- retina contains two layers, thin pigmented and a thicker neural layers.
- pigmented layer, is an outer layer lies agaist the choroid is a single layer of flat to columnar melanocytes. It functions like the choroid to absorb light. Also, it supports the photoreceptor cells by removing damaged portions of those cells, recycling the vitamin A.
- neural layer, is a sheet of nervous tissue that contains the light sensitive photoreceptors cells. only this layer plays a role in vision.
- pig and neural are not fused together.
- neural layers, contains 3 types of neurons Photorecptor cells, bipolar cells, and ganglion cells.
- Photoreceptors; two types: rods and cones. Rods are more sensitive to light and permit vision in dim light. Cone cells operate best in bright light and enable high acuity color vision. (blue, red, and green light are sensitive in cone cells). Photoreceptors are considered neurons.

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- located at the posterior pole of the retina..it contains a pitcalled FOVEA CENTRALIS, which contains only cones and provides maximal visual acuity.
- macula lutea contains mostly cones and the density of the cones declines iwth increasing distance from the macula.
- Opal disk, located medial to the fovea, this is where the axons of ganglion cells converge to exit the eyes as the optic nerve.
- optic disk is called the blind spot because it lacks photoreceptors.

- one of two araes divided in the anterior segment.
- it is between the cornea and iris and the posterior chamber is between the iris and lens.
- aqueous humor: similar to blood plasma, is renewed and is in constant motion unlike vitreous humor. Helps with supplies nutrients and oxygen to the avasular lens and cornea.

- divided by the lens and ciliary zonule, the posteriro segment is filled with clean vitreous humor, a jellylike substance that cintains fine fibrils of collagen and a ground substance that binds tremendous amounts of water, it functions to transmit light, support the posterior surface of the lens and hold the neural retina fimly against the pigmented layer and help maintain intraocular pressure.

- a process in which it allows the eye to focus on closer objects.

- also known as the ear drum, forms a boundary between the middle and and external ear.

- found in the medial boundary, there is a wall of bone that separates it from the inner ear. two small holes penetraet this medial wall..superior oval window and inferior round window.

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- 3 smallest bones in the body,and found in the tympanic cavity.
- malleus (hammer)
- incus (anvil)
- stapes (stirrup of a saddle)
- handle of the malleus attaches to the eardrum and the base of the stapes vibrates against the oval window.

- originates on the cartilage part of the pharyngotympanic tube and inserts on the malleus. Along with the STAPEDIUS, these muscles contract reflexively to limit loud vibrations of the ossicles and thus prevent damage .

- runs from the posterior wall of the middle ear to the stapes.

- is a cavity in the petrous bone consisting of a system of twisting channels that has 3 parts. From posterolateral to anteromedial, they are semicircular canals, the vestibule, and the cochlea.

- is a continuous series of membrane walled sacs and ducts that fit loosely within the bony labyrinth and more of less follow
its contours
- main parts are semicircular ducts, (inside each semicircular canal) utricle and saccule (bothin in the vestibule) and third the cochlear duct.

- spiny chamber of bony labyrinth.
- attachment to the vestibule at the base, it coils into a pill or bone called the MODIOLUS with what threads called OSSEOUS SPIRLA LAMINA. running though the bony core of the modiolus is the COCHLEAR NERVE.

- is the central cavity of the bony labyrinth. lies just medial to the middle ear and the oval window is in the lateral bony wall.

- are three half-circular, interconnected tubes located inside each ear. The three canals are the horizontal semicircular canal (also known as the lateral semicircular canal), superior semicircular canal (also known as the anterior semicircular canal), and the posterior semicircular canal.
- Each canal is filled with a fluid called endolymph and contains a motion sensor with little hairs (cilia) whose ends are embedded in a gelatinous structure called the cupula. As the skull twists in any direction, the endolymph is thrown into different sections of the canals. The cilia detect when the endolymph rushes past, and a signal is then sent to the brain.

- suspended in its perilymph are tow egg shaped parts
- the utricule is continuous iwth the semicircular ducts and the saccule with the cochlear ducts
- both store a spot of sensory epithelium called a MACULA, which have receptor cells that monitor the positioin o th heard when the held is still, this is called static equilibrium.
- they also monitor straigtline changes in speed and direction of head movements.

- an oval-shaped highly pigmented yellow spot near the center of the retina of the human eye

- Near its center is the fovea, a small pit that contains the largest concentration of cone cells in the eye and is responsible for central vision, and also contains the parafovea and perifovea.

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- one of the two branches of the Vestibulocochlear nerve (the cochlear nerve being the other). It goes to the semicircular canals via the vestibular ganglion. It receives positional information.

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- is the sensory organ of rotation located in the semicircular canal of the inner ear. The function of the crista ampullaris is to sense angular acceleration and deceleration.

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- a nerve in the head that carries signals from the cochlea of the inner ear to the brain. It is part of the vestibulocochlear nerve, the 8th cranial nerve which is found in higher vertebrates; the other portion of the 8th cranial nerve is the vestibular nerve which carries spatial orientation information from the semicircular canals.

- is a perilymph filled cavity inside the cochlea of the inner ear that conducts sound vibrations to the scala media

- is one of the perilymph-filled cavities in the cochlear labyrinth. It is separated from the scala media by the basilar membrane, and it extends from the round window to the helicotrema, where it continues as scala vestibuli.

- The purpose of the perilymph-filled scala tympani and scala vestibuli is to transduce the movement of air that causes the tympanic membrane and the ossicles to vibrate, to movement of liquid and the basilar membrane

- is a membrane inside the cochlea of the inner ear. It separates scala media from scala vestibuli. Together with the basilar membrane it creates a compartment in the cochlea filled with endolymph, which is important for the function of the organ of Corti. It primarily functions as a diffusion barrier, allowing nutrients to travel from the perilymph to the endolymph of the membranous labyrinth.

- within the cochlea of the inner ear is a stiff structural element that separates two liquid-filled tubes that run along the coil of the cochlea, the scala media and the scala tympani

- is the organ in the inner ear of mammals that contains auditory sensory cells, or "hair cells."

- The tectorial membrane covers the hair cells in Organ of Corti, with the longer hairs of the outer hair cells embedded in it