Sense Organs

Conjunctiva

- stratified squamous epithelium
- inferior eyelid and the superficial layer of the eyeball
- not over the cornea
- contains goblet cells that lubricate and moisten the eye

Subconjunctival Hemorrhage

- blood vessel rupture

Conjunctivitis

- inflammation of the conjunctiva
- bacterial or viral infection
- caused by rubbing eyes with dirty hands

Eyelids (Palpebrale)

- moveable anterior protective covering

Eyelashes and Eyebrows

- protection of the eye

Sty

- typically caused by an infection of the sebaceous glands associated with eyelash follicles

Lacrimal Apparatus

- cleans and protects the eye surface
- fluid produced in the lacrimal gland, collects in the lacrimal sac and drains into the nasal cavity
- dispersed across the eye surface

Two Main Functions of the Eyeball

- protect/support photoreceptor cells
- gather, focus and process light

Fibrus Tunic

- most external layer of the eye consisting of two regions

Sclera

- apart of the fibrous tunic
- dense collagen connective tissue
- "whites of the eye"

Cornea

- apart of the fibrous tunic
- anterior transparent region of the sclera

Corneal Transplants

- if the cornea becomes clouded, it can be produced by another
- no blood supply, therefore no problem with rejection

Vascular Tunic (Uvea)

- made up of three regions
- middle layer of the eye

Choroid

- apart of the vascular tunic
- highly vascularized layer

Ciliary Body

- apart of the vascular tunic
- blood supply
- suspensory ligaments
- ciliary muscle

Iris

- apart of the vascular tunic
- coloured portion of the eye
- eye colour is correlated with the amount of melanin in this region

Retina

- the inner layer of the eye
- responsible for the conversion of light into nerve signals
- often used for diagnostic purposes
- pigmented layer and neural layer

Macula

- apart of the retina
- directly posterior to the centre of the lens

Optic Disc

- apart of the retina
- where nerve fibers of the retina converge into the optic nerve
- blindspot

Detached Retina

- when the retina is pulled from its normal position
- usually treated with laser surgery or cryotherapy

Lens

- made up of proteins arranged like layers of an onion
- fully transparent with no blood vessels
- ciliary muscle controls the shape

Ciliary Body

- suspensory ligaments that extend from the lens to this region
- responsible for the production of the aqueous humor
- over time the condition of the musculature/lens deteriorates and people lose the ability to focus on close objects

Pupil

- defined by the inner margin of the iris
- 2 muscles that control the diameter of the pupil activated by light intensity

Sphincter Pupillae Muscles

- controlled by the parasympathetic system
- constriction of the pupil

Dilator Pupillae Muscles

- controlled by the sympathetic system
- dilation of the pupil

Vitreous Humor

- inferior area of the eye
- transparent jelly that fills the space behind the lens
- "floaters" are found in this region

Aqueous Humor

- watery solution secreted into the space between the iris and the lens

Extrinsic Eye Muscles

- six muscles that move the eye
- originate from a common tendinous ring in the posterior orbit and attach onto the outer surface of the eye

Outer Ear

- consists of the pinna, auricle, auditory canal and tympanic membrane

Pinna

- apart of the outer ear
- made up of elastic cartilage

Auditory Canal

- leads from the auricle to the tympanic membrane
- apart of the outer ear

Tympanic Membrane

- apart of the outer ear
- partition between the outer ear and middle ear

Ruptured Eardrum

- typically caused by infection or trauma
- heals on its own

Middle Ear

- air filled space in the temporal bone
- consists of the three smallest bones in the body the malleus, incus and stapes

The Eustachian Tube

- selective valve that allows air to enter behind the sealed eardrum
- if air pressure is not equal on both sides of the eardrum, it will not vibrate efficiently

Inner Ear

- also called the labyrinth
- consists of the semicircular canals and the cochlea

Semicircular Canals

- apart of the inner ear
- important for balance

Cochlea

- apart of the inner ear
- vibrations passed from the tympanic membrane, along the ear ossicles to the oval window
- nerve impulses generated that travel along the vestibulocochlear nerve, transporting sound through electrical impulses to the brain

Utriculus and Sacculus

- apart of the semicircular canals
- position of the body with respect to gravity

Canals

- apart of the semicircular canals
- involved in the motion of the body
- filled with endolymph
- triggers neural signals as it moves

Olfaction

- receptors found on the olfactory epithelium lining on top of the nasal cavity
- bathed by the swirling air that enters the nose
- has three cell types: olfactory receptor cells, support cells and basal stem cells

Olfactory Tissue

- individual receptor cells are replaced once a month
- each cranial nerve (I) consists of about 20 groups of nerve fibers

Taste

- chemicals for taste and smell must be dissolved
- receptors for taste are found in taste buds
- found on tongue and elsewhere in pharynx

Gustatory Hair

- molecules first attach
- taste

Receptor Cells

- transmit signals

Sensory Neurons

- merge together to form the facial (VII) or glossopharyngeal (XI) nerves

Individual Taste Buds Can Detect

- sweet
- sour
- bitter
- salty
- umani

Filiform Papillae

- no taste buds
- body of the tongue

Fungiform Papilla

- taste buds on the dorsal surface of the tongue

Vallate Papilla

- taste buds
- upper area of the tongue

Foliate Papilla

- taste buds
- side of the tongue