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Special Senses (Anatomy & Physiology)
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complete lecture in special senses for Anatomy and Physiology
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Our Lady of Fatima University III. Inner EarCollege of Pharmacy Composed of 2 parts:
Anatomy and Physiology I. Bony labyrinth:
wall is bony – temporal bone.
Fluid inside is perilymph made up of:
a) Cochlea – made up of scala vestibuli and
SPECIAL SENSES tympani.
Concerned with hearing.
HEARING
b) Vestibule – concerned with static equilibrium.
3 parts of the ear (contains succule and utricle for linear motion )
c) 3 semicircular canals – concerned with dynamic
Outer ear – contains auricle, external acoustic meatus,
equilibrium. (for circular motion)
tympanic membrane.
Middle ear – contains malleus, incus, limbs of stapes, II. Membranous Labyrinth
oval window & round window. Found inside the bony labyrinth.
Wall is fibrous.
Inner ear – contains receptors, cochlear nerve,
Fluid inside is endolymph.
semicircular ducts, vestibule, vestibulocochlear nerve
a) Scala media –found inside bony cochlea and
(VIII)
contains organ of corti which is the receptor for
hearing)
b) Utricle & Saccule – inside bony vestibule.
I. External ear c) 3 semicircular ducts – inside the semicircular
- Pinna or auricle canal
- External acoustic meatus Perilymph - fluids inside the bony labyrinth.
1. Pinna or auricle – shell shaped structure Endolymph – fluid inside the membranous
surrounding the auditory canal opening labyrinth.
- one that receives the
sound Receptors for Hearing – “Organ of Corti”
2. External auditory canal – short narrow
COCHLEA
chamber (about 1 inch long by ½ inch wide)
- Curved into temporal bone of -main organ of hearing for the inner ear
the skull.
Cochlea- bony labyrinth
- Skin of walls lined with
ceruminous glands which secrete a Cochlear duct- membranous labyrinth
waxy yellow substance called
MODIOLUS - a spiral bony canal turning 2 ¾ around a
earwax or cerum.
central bony axis called. (houses the nerve)
3. Tympanic membrane or eardrum
- A thin membrane separating outer SPIRAL LAMINA – spiral bony projection from modiolus,
from middle ear. turns 2 ¾.
II. Middle Ear Divided into 2:
- a small, air-filled cavity within the temporal bone a) Scala Vestibuli and Tympani – contain
perilymph. They communicate in
- medial boundary – a bony wall with 2 openings: HELICOTREMA.
Oval window – opening that communicates with the HELICOTREMA – scala media contains
inner ear, where the foot of the stapies are attached. endolymph.
(upper portion)
Tectorial Membrane
Round window – the lower portion
- Composed of five filaments embedded in
Anterior boundary – eustachian tube gelatinous matrix rich in mucopolysaccharides.
- Secreted at the upper surface of INTERDENTAL
Ossicles in the middle ear:
CELLS.
Malleus (hammer) – attached to tympanic membrane.
Auditory Center – Brodmann’s area 41, 42 which is
, 2 types of deafness: Macula
- found in the saccule and the utricle.
1. Conduction deafness - For linear motion.
- Temporary or permanent. a. Vestibule (bony labyrinth)
- Disease of external and middle ear. - stimulated by linear acceleration.
e.g. impacted cerumen (impediment example) - Contains gelatinous substance called
otolithic membrane containing
ostoclerosis – (fusion of ossicles) rapture of
otoconia, which are calcium carbonate
eardrum otitis media. crystals.
2. Sensorineural – degeneration or damage to 1. Utricle – largest membranous component of
receptor cells, to cochlear nerve, or to neurons the vestibular.
of auditory cortex due to old age (presbycusis), 2. Saccule – spherical and smaller
extended listening to excessively loud sounds, - Communicates with the cochlear duct
intake of ototoxic drug. through the short narrow ductus
- theres a transmission of pulses reuniens and with utricle through the
but if it gets to nuclear nerve it is defective ultriculo – saccular tract.
3. Endolymphatic duct – tubular evagination of
Test: the utriculosaccular duct.
- It terminates as a blind expansion called
- Weber’s test
endolymphatic sac.
- Base of vibrating tuning fork is applied to the
B. Semicircular canal (Bony labyrinth)
forehead in the midline.
1. Crista ampullaris – for angular acceleration.
a. Normal – if the sound comes from the
- Found in the dilations of semicircular
midline
ducts (membranous) called ampulla.
b. Conduction – if it sound louder in the
- Contains gelatinous substance called
affected ear.
cupula.
c. Sensorineural – if it sound louder in the
2. Vestibonuclear nerve - cranial nerve
normal ear.
1. Rinne’s test OLFACTION
- Base of tuning fork Is placed over the mastoid
process of the skull. Receptors:
- When it can be no longer heard, it is removed - olfactory epithelium located in the upper 1/3 of
and then is held in front of the ear. each nasal mucosa.
a. Normal – air conduction is greater - found in olfactory mucosa found in upper
than bone conduction, concha of the nose.
b. Conduction deafness – bone - Stimulated by chemicals they transmit impulses
conduction is greater than air along olfactory nerve to olfactory center in the
conduction. temporal lobe (uncus – Brodmann’s area 24)
c. Sensorineural deafness – both are - Closely tied with the limbic system (emotional –
diminished but air conduction visceral part of the brain).
remains better than the bone
conduction. Upper- line by olfactory epithelium which is receptor for
smell.
Vestibular Sense (sense of body balance)
Middle & lower – are line by respiratory epithelium for
- Maintains body balance. conduction of air.
- Coordinates eye, head, and body movements.
- Permits the eyes to remain fixed on a point in Olfactory epithelium made up of bipolar cells.
space as the head moves. Olfactory bulb contains mitral cells.
Vestibular Organs –found in the inner ear and made up Olfactory nerve - olfactory bulb - ofactory striae -
of vestibule and semicircular canals are components of brodmann’s area 34
the bony labyrinth associated.
Vestibule – contains utricle and saccule.
Semicircular canal – contains semicircular duct.
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