Classification

Epitheliums can be classified on appearance or on function

Classification based on appearance

- Simple - one layer of cells

- Pseudostratified - looks like more than one layer but is not

- Stratified - more than one layer of cells

Simple epitheliums

Simple squamous epithelium

 Cells are flat with bulging or flat nuclei.  Lines the insides of lung alveoli and certain ducts in the kidney

 Forms serous membranes called mesothelium that line cavities like: pericardial ,  peritoneal,  plural

 Lines blood vessels - known as endothelium

Simple cuboidal epithelium

It appears square in cross section,  Found in: - Ducts of salivary glands,  Follicles of the thyroid gland,  Pigment layer in the eye,  Collecting ducts of the kidney, In the middle ear is ciliated type.

Simple columnar

• Lines the gastrointestinal tract from the stomach to the anal canal,  Some columnar cells have a  secretory function – stomach, peg cells in the oviduct,  Some columnar cells have microvilli on their free border (striated border) – gall bladder, duodenum
• Microvilli increase the surface area for absorption
• Some columnar cells have cilia – oviduct, smaller bronchi
• Cilia transport particles

Pseudostratified

Appears as stratified epithelium but all cells are in contact with the basement membrane.  Has a thick basement membrane. Different cell types make up this epithelium,  Cells that can be found in this type of epithelium are:

• Columnar cells with cilia or microvilli.
• Basal cells that do not reach the surface.
• Goblet cells that secrete mucous.
• Found in the trachea, epididymus, ductus deferens and female urethra

Stratified epithelium

Classified according to the shape of the surface cells

Stratified squamous epithelium

Has a basal layer that varies from cuboidal to columnar cells that divide to form new cells. Two types are found:

Keratinized:  Mostly forms a dry covering, The middle layers consists of cells that are forming- and filling up with keratin. The superficial cells form a tough non living layer of keratin,  Keratin is a type of protein,  The skin is of this type has  thick skin - found on the hand palms and soles of the feet,  thin skin - found on the rest of the body

Non-keratinized:  Top layer of cells are living cells with nuclei  Forms a wet covering,  The middle layers are polyhedral,  The surface layer consists of flat squamous cells

• Is found in:  mouth,  oesophagus,  vagina

Stratified cuboidal epithelium

Found: - in the ducts of sweat glands

Stratified columnar epithelium

Found at the back of the eyelid (conjunctiva)

Transitional epithelium

- Sometimes the surface cells are squamous, sometimes cuboidal and sometimes columnar

- The superficial cells are called umbrella cells because they can open and close like umbrellas, when the epithelium stretch and shrink

- Umbrella cells can have 2 nuclei

- Found in the bladder and ureter

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

Nerves of the Face

Innervation of the Muscles of Facial Expression

The Facial Nerve (CN VII)

• The seventh cranial nerve supplies the superficial muscle of the neck (platysma), the muscles of facial expression, the auricular muscles and the scalp muscles.
• CN VII is the sole motor supply to the muscles of facial expression.

• The facial nerve emerges from the skull though the stylomastoid foramen.
• Almost immediately, it enters the parotid gland. It runs superficially in this gland before giving rise to its five terminal branches: temporal, zygomatic, buccal, marginal mandibular, and cervical.
• These nerve emerge from the superior, anterior and inferior margins of the gland and spread out like the abducted digits of the hand to supply the muscles of facial expression.

• The temporal branches of CN VII cross the zygomatic arch to supply all the superficial facial muscles superior to it, including the orbital and forehead muscles.

• The zygomatic branch of CN VII passes transversely over the zygomatic bone to supply the muscles in the zygomatic, orbital and infraorbital regions.

• The buccal branches of CN VII pass horizontally, external to the masseter muscle, to supply the buccinator and the muscles of the upper lip.

• The marginal mandibular branch of CN VII supplies the muscles of the lower lip and chin.

• The cervical branch of CN VII supplies the platysma and the superficial muscles of the neck.

Muscles Moving the Auditory Ossicles

The Tensor Tympani Muscle

• This muscle is about 2 cm long.

• Origin: superior surface of the cartilaginous part of the auditory tube, the greater wing of the sphenoid bone, and the petrous part of the temporal bone.
• Insertion: handle of the malleus.
• Innervation: mandibular nerve (CN V³) through the nerve to medial pterygoid.

• The tensor tympani muscle pulls the handle of the malleus medially, tensing the tympanic membrane, and reducing the amplitude of its oscillations.
• This tends to prevent damage to the internal ear when one is exposed to load sounds.

The Stapedius Muscle

• This tiny muscle is in the pyramidal eminence or the pyramid.

• Origin: pyramidal eminence on the posterior wall of the tympanic cavity. Its tendon enters the tympanic cavity by traversing a pinpoint foramen in the apex of the pyramid.
• Insertion: neck of the stapes.
• Innervation: nerve to the stapedius muscle, which arises from the facial nerve (CN VII).

• The stapedius muscle pulls the stapes posteriorly and tilts its base in the fenestra vestibuli or oval window, thereby tightening the anular ligament and reducing the oscillatory range.
• It also prevents excessive movement of the stapes.

• Skull 
  Cranium
  o    Superior portion formed by the frontal. parietal, and occipital bones
  o    Lateral portions formed by the temporal and sphenoid bones
  o    Cranial base formed by the temporal. sphenoid, and ethmoid bones
  o    Fontanels-soft spots in which ossification is incomplete at birth

  Frontal bone
  o    Forms the forehead
  o    Contains the frontal sinuses
  o    Forms the roof of the orbits
  o    Union with the parietal bones forms the coronal suture

  Parietal bones
  o    Union with the occipital bone forms the lambdoid suture
  o    Union with the temporal bone forms the squamous suture
  o    Union with the sphenoid bone forms the coronal suture

  Temporal bones
  o    Contains the external auditory meatus and middle and inner ear structures
  o    Squamous portion-above the meatus: zygomatic process-articulates with the zygoma
  o    to form the zygomatic arch 

  •    Petrous portion
  o    Contains organs of hearing and equilibrium 
  o    Prominent elevation on the floor of the cranium

  •    Mastoid portion
  o    Protuberance behind the ear

  o    Mastoid process
  •    Glenoid fossa-articulates with the condyle on the mandible
  •    Styloid process-anterior to the mastoid process; several neck muscles attach here
  •    Stylomastoid foramen-located between the styloid and mastoid processes; facial nerve emerges through this opening
  •    Jugular foramen-located between the petrous portion and the occipital bone: cranial nerves IX. X, and XI exit
   

- The forehead is formed by the smooth, broad, convex plate of bone called the frontal squama.
- In foetal skulls, the halves of the frontal squama are divided by a metopic suture.
- In most people, the halves of the frontal bone begin to fuse during infancy and the suture between is usually not visible after 6 years of age.
- The frontal bone forms the thin roof of the orbits (eye sockets).
- Just superior to and parallel with each supraorbital margin is a bony ridge, the superciliary arch, which overlies the frontal sinus. This arch is more pronounced in males.
- Between these arches there is a gently, rounded, medial elevation called the gabella; this term derives from the Latin word glabellus meaning smooth and hairless. In most people, the skin over the gabella is hairless.
-The slight prominences of the forehead on each side, superior to the superciliary arches, are called frontal eminences (tubers).
- The supraorbital foramen (occasionally a notch), which transmits the supraorbital vessels and nerve is located in the medial part of the supraorbital margin.
- The frontal bone articulates with the two parietal bones at the coronal suture.
-It also articulates with the nasal bones at the frontonasal suture. At the point where this suture crosses the internasal suture in the medial plane, there is an anthropological landmark called the nasion . The depression is located at the root of the nose, where it joins the cranium.
- The frontal bone also articulates with the zygomatic, lacrimal, ethmoid, and sphenoid bones.
In about 8% of adult skulls, a remnant of the inferior part of the metopic (interfrontal) suture is visible. It may be mistaken in radiographs for a fracture line by inexperienced observers.
- The superciliary arches are relatively sharp ridges of bone and a blow to them may lacerate the skin and cause bleeding.
- Bruising of the skin over a superciliary arch causes tissue fluid and blood to accumulate in the surrounding connective tissue, which gravitates into the upper eyelid and around the eye. This results in swelling and a "black eye".
- Compression of the supraorbital nerve as it emerges from its foramen causes considerable pain, a fact that may be used by anaesthesiologists and anaesthetists to determine the depth of anaesthesia and by physicians attempting to arouse a moribund patient.