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

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

Classified on functional Basis

Secretion ,Protection and waterproofing, Absorbtion, Transport, Sensory

Secretion

Glandular epithelium’s 3 types:

- Exocrine - with ducts

- endocrine - without ducts

- mixed exo-endocrine

Exocrine glands: One cell

- goblet cells

- In lining epitheliums of respiratory tract and GIT

- Secretes musin (protein) Musin + water = mucus, Mucus is a lubricant

More than one cell

 Simple:  Has a single duct,

• Acinar - mucus glands of the penile urethra
• Tubular - cripts of Lieberkuhn
• Coiled tubular - sweat gland
• Spiral tubular - Gland of Moll
• Branched tubular - mucous glands of the pyloric region
• Branched acinar - sebaceous gland in the skin

Compound

• Consists of a branched duct with numerous secretory end organs
• Compound tubular - Brünners glands
• Compound alveolar - mammary, prostate, pancreas, parotid
• Compound tubuloalveolar - submandibular-, sublingual salivary glands

Endocrine glands

Secrete directly into the blood

One cell :  mast cells,  in soft CT,  near capillaries,

secrete - heparin - histamine

More than one cell

Cells can be arranged in the following ways:

• Cords - adrenal glands, parathyroid, anterior pituitary
• anastomosing cords with dilated blood capillaries in-between
• Isles - pancreas
• Follicles - thyroid
• cells line a follicle filled with non-cellular material

The Parotid Glands

• The parotid glands are the largest of the three pairs of salivary glands.
• Each gland is wedged between the mandible and the sternocleidomastoid muscle and partly covers them.

• The parotid gland is wrapped with a fibrous capsule (parotid fascia) that is continuous with the deep investing fascia of the neck.

• Viewed superficially, the parotid gland is somewhat triangular in shape.
• Its apex is posterior to the angle of the mandible and its base is along the zygomatic arch.
• The parotid gland overlaps the posterior part of the masseter muscle.

• The parotid duct (Stensen's duct) is about 5 cm long and 5 mm in diameter.
• It passes horizontally from the anterior edge of the gland.
• At the anterior border of the masseter muscle, the parotid duct turns medially and pierces the buccinator muscle.
• It enters the oral cavity opposite the second maxillary molar.

Blood Vessels of the Parotid Gland

• This gland is supplied by branches of the external carotid artery.
• The veins from the parotid gland drains into the retromandibular vein, which enters the internal jugular vein.

Lymphatic Drainage of the Parotid Gland

• The lymph vessels of this gland end in the superficial and deep cervical lymph nodes.

Nerves of the Parotid Gland

• These nerves are derived from the auriculotemporal nerve and from the sympathetic and parasympathetic systems.

• The parasympathetic fibres are derived from the glossopharyngeal nerve (CN IX) through the otic ganglion.
• Stimulation of these fibres produces a thin watery (serous) saliva to flow from the parotid duct.

• The sympathetic fibres are derived from the cervical ganglia through the external carotid plexus.
• Stimulation of these fibres produces a thick mucous saliva.

Sternum

o    Forms the medial part of the anterior chest wall
o    Manubrium (upper part)-clavicle and first rib articulate with the manubrium .
o    Body (middle blade)-second and tenth ribs articulate with the body via the costal cartilages
o    Xiphoid (blunt cartilaginous tip)

Ribs (12 pairs)

o    Each rib articulates with both the body and the transverse process of its corresponding
o    thoracic vertebra
o    The second to ninth ribs articulate with the body of the vertebra above'
o    Ribs curve outward, forward, and then downward
o    Anteriorly, each of the first seven ribs joins a costal cartilage that attaches to the sternum
o    Next three ribs (eighth to tenth) join the cartilage of the rib above
o    Eleventh and twelfth ribs do not attach to the sternum; are called "floating ribs"

Muscles of the Soft Palate

The Levator Veli Palatini (Levator Palati)

• Superior attachment: cartilage of the auditory tube and petrous part of temporal bone.
• Inferior attachment: palatine aponeurosis.
• Innervation: pharyngeal branch of vagus via pharyngeal plexus.
• This cylindrical muscle runs inferoanteriorly, spreading out in the soft palate, where it attaches to the superior surface of the palatine aponeurosis.
• It elevates the soft palate, drawing it superiorly and posteriorly.
• It also opens the auditory tube to equalise air pressure in the middle ear and pharynx.

The Tensor Veli Palatini (Tensor Palati)

• Superior attachment: scaphoid fossa of medial pterygoid plate, spine of sphenoid bone, and cartilage of auditory tube.
• Inferior attachment: palatine aponeurosis.
• Innervation: medial pterygoid nerve (a branch of the mandibular nerve).
• This thin, triangular muscle passes inferiorly, and hooks around the hamulus of the medial pterygoid plate.
• It then inserts into the palatine aponeurosis.
• This muscle tenses the soft palate by using the hamulus as a pulley.
• It also pulls the membranous portion of the auditory tube open to equalise air pressure of the middle ear and pharynx.

The Palatoglossus Muscle

• Superior attachment: palatine aponeurosis.
• Inferior attachment: side of tongue.
• Innervation: cranial part of accessory nerve (CN XI) through the pharyngeal branch of vagus (CN X) via the pharyngeal plexus.
• This muscle, covered by mucous membrane, forms the palatoglossal arch.
• The palatoglossus elevates the posterior part of the tongue and draws the soft palate inferiorly onto the tongue.

The Palatopharyngeus Muscle

• Superior attachment: hard palate and palatine aponeurosis.
• Inferior attachment: lateral wall of pharynx.
• Innervation: cranial part of accessory nerve (CN XI) through the pharyngeal branch of vagus (CN X) via the pharyngeal plexus.
• This thin, flat muscle is covered with mucous membrane to form the palatopharyngeal arch.
• It passes posteroinferiorly in this arch.
• This muscle tenses the soft palate and pulls the walls of the pharynx superiorly, anteriorly and medially during swallowing.

The Musculus Uvulae

• Superior attachment: posterior nasal spine and palatine aponeurosis.
• Inferior attachment: mucosa of uvula.
• Innervation: cranial part of accessory through the pharyngeal branch of vagus, via the pharyngeal plexus.
• It passes posteriorly on each side of the median plane and inserts into the mucosa of the uvula.
• When the muscle contracts, it shortens the uvula and pulls it superiorly.