Internal Ear

• Osseous labyrinth: a complex system of cavities in the substance of the petrous bone.
• Membranous labyrinth: filled with endolymph, bathed in perilymph.

The Nasopharynx

• The nasal part of the pharynx has a respiratory function.
• It lies superior to the soft palate and is a posterior extension of the nasal cavity.
• The nose opens into the nasopharynx via to large posterior apertures called choanae.

• The roof and posterior wall of the nasopharynx form a continuous surface that lies inferior to the body of the sphenoid bone and the basilar part of the occipital bone.
• In the mucous membrane of the roof of the posterior wall of the nasopharynx is a collection of lymphoid tissue, known as the pharyngeal tonsil (commonly known as the adenoids).

• The pharyngeal orifice of the auditory tube is on the lateral wall of the nasopharynx, 1 to 1.5 cm posterior to the inferior concha, and level with the superior border of the palate.
• The orifice is directed inferiorly and has a hood-like tubal elevation over it called the torus of the auditory tube or the torus tubarius (L. torus, swelling).

• Extending inferiorly from the torus is a vertical fold of mucous membrane, known as the salpingopharyngeal fold.

• The collection of lymphoid tissue in the submucosa of the pharynx, posterior to the orifice of the auditory tube, is known as the tubal tonsil.

• Posterior to the torus and the salpingopharyngeal fold, there is a slit-like lateral projection of the pharynx called the pharyngeal recess.
• It extends laterally and posteriorly.

Histology

Histology is the study of tissues.

A tissue is a group of cells with similar structure and function plus the extracellular substances located between the cells.

There are four basic types of tissues:

- Epitheliums

- Connective tissue

- Muscle tissue

- Nervous tissue

Gross Features of the Tongue

• The dorsum of the tongue is divided by a V-shaped sulcus terminalis into anterior oral (presulcal) and posterior pharyngeal (postsulcal) parts.
• The apex of the V is posterior and the two limbs diverge anteriorly.
• The oral part forms about 2/3 of the tongue and the pharyngeal part forms about 1/3.

Oral Part of the Tongue

• This part is freely movable, but it is loosely attached to the floor of the mouth by the lingual frenulum.

• On each side of the frenulum is a deep lingual vein, visible as a blue line.
• It begins at the tip of the tongue and runs posteriorly.
• All the veins on one side of the tongue unite at the posterior border of the hyoglossus muscle to form the lingual vein, which joins the facial vein or the internal jugular vein.

• On the dorsum of the oral part of the tongue is a median groove.
• This groove represents the site of fusion of the distal tongue buds during embryonic development.

The Lingual Papillae and Taste Buds

• The filiform papillae (L. filum, thread) are numerous, rough, and thread-like.
• They are arranged in rows parallel to the sulcus terminalis.

• The fungiform papillae are small and mushroom-shaped.
• They usually appear are pink or red spots.

• The vallate (circumvallate) papillae are surrounded by a deep, circular trench (trough), the walls of which are studded with taste buds.

• The foliate papillae are small lateral folds of lingual mucosa that are poorly formed in humans.

• The vallate, foliate and most of the fungiform papillae contain taste receptors, which are located in the taste buds.

The Pharyngeal Part of the Tongue

• This part lies posterior to the sulcus terminalis and palatoglossal arches.
• Its mucous membrane has no papillae.

• The underlying nodules of lymphoid tissue give this part of the tongue a cobblestone appearance.
• The lymphoid nodules (lingual follicles) are collectively known as the lingual tonsil.

o    English: all speech sounds produced by making exhaled air audible

o    Two ways of producing sound
    at larynx
    further up in vocal tract (tongue, lips)
    
o    How to produce sound at larynx
    changes in breathing: regulate airstream from lungs to atmosphere by changing movements of vocal folds, pharynx, soft-palate, tongue, lips and jaws
    
•    inhalation: take in greater volume more quickly, abduct folds

•    expiration: variable force; use muscles of inhalation to control rate of expiration, adduct

    How to vibrate vocal cords
    
•    NOT rhythmic contraction of laryngeal muscles: would be impossible b/c frequenceies of virbration
•    Changes in air pressure cause vibrations

    o    Adduct folds increase in subglottal pressure force folds apart folds sucked back together (Bernouilli effect)
•    The vibration of vocal cords disturbs airareas of low pressure (rarefaction) alternating with areas of high pressure (compression)
•    Changes in pressure sound at ears
•    Sine waves

    o    Changes in amplitudes: loudness

    o    Changes in frequency: pitch

    o    Normal sounds have fundamental frequency, overtones or harmonics

    o    Mass of folds: critical in voice
    Low pitch of lion’s roar: due to massive fibrous pad that forms part of vocal cords
    Men: more massive vocal cords
    Larger foldsslow vibrationdeeper voice

    o    Producing vowels and constants
    Most vowels are “voiced”: vocal folds produce sounds
    Consonants: can be “voiced” (Z) or “non-voiced” (S)
•    Use higher regions of vocal tract to control by stopping, restricting airflow from vocal folds; use lips, teethaperiodic sound

o    Vocal folds and resonators emphasize and deemphasize certain frequencies
    Never hear sounds produced at vocal foldsevery sound changed by passage thru vocal tract: sinuses/resonating chambers
    Howling monkeys: large hyoid bonepowerful resonator

    o    Age-related changes in voice
    
    Infant larynx is smaller, different proportions
•    Arytenoids are proportionately larger
•    Smaller vocal apparatushigher pitch
•    Larynx sits higher easier to breathe thru nose
    Abrupt change in larynx at pubertycan’t control voice
    Older adult: normal degenerative changes in lamina propria, ossification of thyroid cartilagechanges in fundamental frequency
    Lose your voice vocal fold are irritated
•    Can’t adduct foldsair escapes

o    Singing v. speaking
    Singing: greater thoracic pressure and uneven breathing with changes in resonators

    o    Whispering
    Intercartilaginous portions of vocal folds: open to allow air to escapelesser subglottal pressureslittle vibration of foldslittle tonal quality, low volume

    o    Falsetto
    Allowing only part of vocal folds to vibrate
    Increase range by training which part of vocal folds to vibrate

    o    Colds
    Mucus secretions add mass to folds—decrease in pitch, can’t adduct folds as well

    o    Surgeryscars, fibrotic changes can interfere with voice

Cardiac Muscle

Fibres anastomose through cross bridges

Fibres are short, connected end to end at intercalated discs, also striated,  contract automatically

Light microscopic Structure:

Short fibres connected at intercalated disks,  85 - 100 µm long,  15 µm

same bands as in skeletal muscle,  1 or 2 nuclei - oval and central,  in perinuclear area is a sarcoplasmic reticulum, intercalated discs lie at the Z line

Electron microscopic structure:

 Between myofibrils lie the mitochondria,  2,5 µm long mitochondria,  dense cristae

and are as long as the sarcomere, fibres have more glycogen than skeletal muscle fibres

myofilaments, actin and myosin are the same as in skeletal muscle,  the sarcoplasmic reticulum differs in that there is no terminal sisterna. The sarcotubules end in little feet that

sit on the T-tubule

Intercalated Disc:

on Z lines,  fibres interdigitate,

 3 types of junctions in the disc

Transverse Part:

zonula adherens

desmosomes

Lateral Part:

Gap junctions (nexus) - for impulse transfer

Mechanism of Contraction:

slide - ratchet like in skeletal muscle, certain fibres are modified for conduction,  Impulses spread from cell to cell through gap junctions,  Purkinje cells are found in the AV bundle

they have less myofibrils,  lots of glycogen and intercalated discs

Connective tissue coverings:

Only endomycium in cardiac muscle,  Blood vessels, lymph vessels and nerves lie in the endomycium