Semester 1 Review Anatomical directional terms Cells and tissues Skin and the integumentary system Nervous system

Special Senses Eye and Ear

Eye and Vision

Quick Facts about the Eye 70% of all sensory receptors are in the eye Approx. 1 inch in diameter Uses light to gather information about environment

External Eye Eyelid Eyelashes Medial canthus Lateral canthus

Accessory Structures of the Eye Tarsal glands (within eyelids) Conjuctiva Lacrimal apparatus – Lacrimal glands  Lacrimal canals and lacrimal sac  Nasolacrimal duct  nasal cavity – Lacrimal secretions are made up of a dilute salt solution and lysozyme (antibiotic)

Internal Eye Anatomy

Eye Overview Made of tunics and humors Tunics: layers surrounding the eye and it’s parts Humors: fluid areas within the tunics to give eye pressure and keep it’s shape

Tunics Sclera: outermost tunic – Thick, white covering – Anterior portion modified into cornea No blood vessels

Tunics Vascular tunic: middle tunic – Supplies blood to eye – 2 parts: Choroid (posterior) Ciliary body (anterior) attaches lens using ciliary zonule (suspensory ligaments) Iris Pupil

Tunics Sensory tunic: innermost tunic Retina: contains photoreceptors – Rods: black, white and shades of gray in dim light, peripheral vision – Cones: color receptors (what colors?) Signals sent from retina to optic nerve to brain

Retina Macula lutea: yellowish area near back of the eye – Fovea Centralis: depression in the center of Macula lutea High concentration of cones Produces sharpest vision Optic disc: nerve fibers and blood vessels enter and leave the eye – Contains a blind spot

Humors Humors: fluid filled areas in eye Aqueous humor – Anterior to lens – Constantly replaced to bring nutrients to areas without blood supply Secreted by choroid Scleral vernous sinus (canal of Schlemm) – at junction of sclera and cornea Vitreous humor – Posterior to lens – Constant pressure to give eye shape (intraocular pressure)

Lens Biconvex structure Behind cornea, iris, pupil Bends to focus on objects

Muscles of the Eye (right eye)

Muscles of the Eye (front)

How does the eye work? Light is refracted by each layer it moves through – Humors, lens, cornea Image is shown on retina (upside-down) and sent to brain Brain flips the image and uses other cues to make sense of image

How does the eye work? Nerve impulses from the retina leave the eye through the optic nerve. Optic nerves from each eye meet at the optic chiasm.

How does the eye work? At the optic chiasm, the impulses from the medial portion of each retina cross over to the opposite side Leaving the optic chiasm are the optic tracts, which fuse in the thalamus Leaving the thalamus are the optic radiations, which then join to the occipital lobe (visual cortex) of the brain where interpretation occurs

How does the eye work? Result is that each side of the brain receives input from both eyes. Binocular vision – each eye sends an image to the brain, resulting in 3-dimensional vision.

Problems within the Eye Cateracts Conjunctivitis Nearsightedness – distant objects are blurry Farsightedness – close objects are blurry Astigmatism Glaucoma

Sheep Eye Dissection

Additional Sheep Eye Questions 1.How did the fat and muscle tissue differ in the sheep eye? 2.What is the function of the choroid coat? 3.How is the tapetum lucidum used in the sheep eye?

The Ear, Hearing, and Balance

Overview of the Ear 3 parts: outer, middle, inner Mechanoreceptor: respond to physical forces (sound vibrations, movement of the head)

Middle Ear Tympanic membrane Ossicles: smallest bones in the human body – hammer/malleus – anvil/incus – stirrup/stapes

Middle Ear Oval window Round window Pharyngotympanic tube (auditory/Eustachian tube)– connects ear and throat and will open and close to keep pressure within ear the same as external pressure

Outer Ear Pinna or auricle – external ear – Surrounds auditory canal into ear canal External acoustic meatus (external auditory canal) – skin lined canal between outside of the head and the eardrum – Glands in skin (ceruminous glands) secrete cerumen to protect ear

Inner Ear Made up of bony chambers called the osseous (bony) labyrinth 3 divisions: – Cochlea – Vestibule – Semicircular canals

Inner Ear Filled with fluid called perilymph Within labyrinth are membranes (membranous labyrinth) – Filled with endolymph

Inner Ear Semicircular canals and vestibule are responsible for balance and detecting motion. Cochlea is responsible for hearing.

Hearing Organ of Corti – Within the cochlea – Basilar membrane Anchors hair cells – Tectoral membrane Above hair cells Different sounds will vibrate membranes at different frequency

Organ of Corti

How sound travels to the brain Send sound signals along cochlear nerve to the temporal lobe (auditory cortex) Two ears help us determine where sounds are coming from Over-stimulation of cochlear nerve allows us to “tune out” certain sounds

Hearing Video m_E m_E

Equilibrium and Balance Vestibular Apparatus: equilibrium detectors in the vestibule and semicircular canals Send signals to brain through vestibular nerve to cerebellum

Static equilibrium Vestibule of the inner ear Respond to gravity, balance – Utricle (hairs are upright) – Saccule (hairs are horizontal) Maculae: patch of hairs and supporting cells on the utricle and saccule Otolithic membrane (gel-like material) contains otoliths (calcium carbonate stones) to detect movement of head

Static Equilibrium

Dynamic equilibrium Semicircular Canals – Anterior canal – Posterior canal – Lateral canal Movement in all directions

Semicircular Canals Membranous canals within the bony canal ends in an ampulla – Communicate with the utricle

Semicircular Canals (within the ampulla) Crista ampullaris: contains hairs to detect movement Cupula (gel cap) on the hairs of the christa ampullaris – Movement bends hairs, cupula, endolymph

Dynamic Equilibrium Cupula on surface of the crista ampullaris bends hairs in response to motion.