Smooth Muscle

Light microscopic Structure:

cells - long - spindle shaped,  nucleus lies in the widest widest part of the fiber,  when the fiber contract the nucleus become folded, 30 - 200 µm long,between fibres lie endomycium

Electron microscopic structure:

 Mitochondria, ribosomes, golgi, rough EPR, myofilaments are present but no sarcomeres and no Z lines,thin filaments - actin and tropomyosin (7nm), thick filaments - myosin (17nmØ)

- intermediate filaments (10 nm)

- actin and myosin overlap more than in skeletal muscle and can therefore contract more

 A rudimentary sacroplasmic reticulum is present in the form of invaginations on the surface called caveolae , So there are no T-tubules,  Cells communicate through gap junctions.

Dense bodies

Filaments are attached to dense bodies which take the place of the Z line in skeletal muscle

There are two types of dense bodies - cytoplasmic and membrane

contains a percentage actinin (like the Z line)

dense bodies transmit contractile force to adjacent fibres

Arrangement:

Fibres can be single or in groups, normally arranged in sheaths,  In the GIT are 2 or 3 layers

Nerve supply:

2 types:

Where it is arranged in layers a few fibres are innervated together

impulse spread through the gap junctions between fibres (slow contraction)

In the iris and the vas deferens each fiber is individually supplied (quick contraction)

The Nose

• The nose is the superior part of the respiratory tract and contains the peripheral organ of smell.
• It is divided into right and left nasal cavities by the nasal septum.
• The nasal cavity is divided into the olfactory area and the respiratory area.

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

• This is the posterior curtain-like part, and has no bony support. It does, however, contain a membranous aponeurosis.
• The soft palate, or velum palatinum (L. velum, veil), is a movable, fibromuscular fold that is attached to the posterior edge of the hard palate.
• It extends posteroinferiorly to a curved free margin from which hangs a conical process, the uvula (L. uva, grape).

• The soft palate separates the nasopharynx superiorly and the oropharynx inferiorly.

• During swallowing the soft palate moves posteriorly against the wall of the pharynx, preventing the regurgitation of food into the nasal cavity.

• Laterally, the soft palate is continuous with the wall of the pharynx and is joined to the tongue and pharynx by the palatoglossal and palatopharyngeal folds.

• The soft palate is strengthened by the palatine aponeurosis, formed by the expanded tendon of the tensor veli palatini muscle.
• This aponeurosis attaches to the posterior margin of the hard palate.

Intramembranous ossification

• Flat bones develop in this way (bones of the skull)
• This type of bone development takes place in mesenchymal tissue
• Mesenchymal cells condense to form a primary ossification centre (blastema)
• Some of the condensed mesenchymal cells change to osteoprogenitor cells
• Osteoprogenitor cells change into osteoblasts which start to deposit bone
• As the osteoblasts deposit bone some of them become trapped in lacunae in the bone and then change into osteocytes
• Osteoblasts lie on the surface of the newly formed bone
• As more and more bone is deposited more and more osteocytes are formed from mesenchymal cells
• The bone that is formed is called a spicule
• This process takes place in many places simultaneously
• The spicules fuse to form trabeculae
• Blood vessels grow into the spaces between the trabeculae
• Mesenchymal cells in the spaces give rise to hemopoetic tissue
• This type of bone development forms the first phase in endochondral development
• It is also responsible for the growth of short bones and the thickening of long bones

The Orbital Margin

• The frontal, maxillary and zygomatic bones contribute equally to the formation of the orbital margin.

• The supraorbital margin is composed entirely of the frontal bone.
• At the junction of its medial and middle thirds is the supraorbital foramen (sometimes a notch), which transmits the supraorbital nerves and vessels.

• The lateral orbital margin is formed almost entirely of the frontal process of the zygomatic bone.

• The infraorbital margin is formed by the zygomatic bone laterally and the maxilla medially.

• The medial orbital margin is formed superiorly by the frontal bone and inferiorly by the lacrimal crest of the frontal process of the maxilla.
• This margin is distinct in its inferior half only.