CARTILAGE

There are 3 types:

Hyaline cartilage
Elastic cartilage
Fibrocartilage

Matrix is made up by: Hyaluronic acid

Proteoglycans

- In cartilage the protein core of the proteoglycan molecule binds through a linking protein to hyaluronic acid to form a proteoglycan aggregate which binds to the fibres

- In the matrix there are spaces, lacunae in which one to three of the cells of cartilage, chondrocytes, are found

- The matrix around the lacuna is the territorial matrix

- Type II collagen fibrils are embedded in the matrix

- The type of fiber depends on the type of cartilage

- Cartilage is surrounded by perichondrium which is a dense CT

- Apositional growth takes place in the perichondrium

- The fibroblasts of the perichondrium change to elliptic chondroblasts which later change to round chondrocytes

- Interstitial growth takes place around the lacunae

- Nutrients diffuse through the matrix to get to the chondrocytes   this limits the thickness of cartilage

Hyaline cartilage

Found: Rib cartilage,  articulating surfaces,  nose,  larynx, trachea, embryonic skeleton, Articulating cartilage has no perichondrium

 Bluish-white and translucent

Contains type II collagen that is not visible

Elastic cartilage

Found:  external auditory canal,  epiglottis

Similar to hyaline except that it contains many elastic fibres ,Yellow in colour,  Can be continuous with hyaline

Fibrocartilage

Found: Intervertebral disk, symphysis pubis

Always associated with dense CT,  Many collagen fibres in the matrix, No perichondrium

- Chondrocytes tend to lie in rows, Can withstand strong forces

The Cheeks

• The cheeks (L. buccae) form the lateral wall of the vestibule of the oral cavity.
• They have essentially the same structure as the lips with which they are continuous.

• The principal muscular component of the cheeks is the buccinator muscle.
• Superficial to the fascia covering this muscle is the buccal fatpad that gives cheeks their rounded contour, especially in infants.

• The lips and cheeks act as a functional unit (e.g. during sucking, blowing, eating, etc.).
• They act as an oral sphincter in pushing food from the vestibule to the oral cavity proper.
• The tongue and buccinator muscle keep the food between the molar teeth during chewing.

Sensory Nerves of the Cheeks

• These are branches of the maxillary and mandibular nerves.
• They supply the skin of the cheeks and the mucous membrane lining the cheeks.

Muscles Around the Nose

The Nasalis Muscle

• This muscle consists of a transverse (compressor naris) and alar (dilator naris) parts.
• It is supplied by the buccal branch of the facial nerve.

Skeletal Muscle:  1-40 cm long fibres, 10- 60 µm thick, according to myoglobin content there are:

Red fibres: lots of myoglobin, many mitochondriam slow twitching - tire slowly

White fibres:  less myoglobin,  less mitochondria, fast twitching - tire quickly

Intermediate fibres:

mixture of 2 above

Most muscles have all three - in varying ratios

Structure of skeletal muscle:

Light Microscopy:  Many nuclei - 35/mm,  Nuclei are oval - situated peripheral,  Dark and light bands

Electron Microscopy: Two types of myofilaments

Actin

- 5,6 nm

 3 components:

 -actin monomers,  

 -tropomyosin - 7 actin molecules long

- troponin

 actin monomers form 2 threats that spiral

- tropomyosin - lie in the groove of the spiral

- troponin - attach every 40 nm

- one end attach to the Z line

- other end goes to the middle of the sarcomere

- Z line consists of á actinin

Myosin:

- 15 nm

- 1,6 µm long

- The molecule has a head and a tail

- tails are parallel

- heads project in a spiral

- in the middle is a thickening

- thin threats bind the myosin at thickening (M line)

Contraction:

A - band stays the same, I - band, H - bands become narrower

Myosin heads ratchet on the actin molecule

Sarcolemma: 9 nm thick,  invaginate to form T-tubule,

 myofibrils - attach to the sarcolemma

Sarcoplasmic Reticulum:

specialized smooth EPR,  Consists of T-tubules, terminal sisternae and sarcotubules

It is speculated that there are gap junctions between the T-tubule and terminal sisterna

An impulse is carried into the fiber by the T-tubule from where it goes to the rest of the sarcoplasmic reticulum

Connective tissue coverings of the muscle

Endomycium around fibres, perimycium around bundles and epimycium around the whole muscle

Blood vessels and nerves in CT

CT goes over into tendon or aponeurosis which attaches to the periosteum

Nerves:

The axon of a motor neuron branches and ends in motor end plates on the fiber

Specialized striated fibres called spindles (stretch receptors) form sensory receptors in muscles telling the brain how far the muscle has stretched

• U-shaped bone
• Body
• Greater horn
• Lesser horn

• Suspended by ligaments from the styloid process

3 basic functions
o    protection of respiratory tract during swallowing food/air pathways cross.
    epiglottis provides protection
o    control intra-thoracic pressure (in coughing) -    close off airway to build pressure then rapidly open to release stuff
o    production of sound (in speaking, singing, laughing)

Important structures

o    hyoid bone
o    thyroid cartilage
o    arytenoids cartilage: vocal and muscle process
    sits on slope on posterior side of cricoid - spin and slide
o    cricoid cartilage: signet ring
o    thyroepiglottic ligament

Membranes and ligaments

o    membrane: general; ligament: thickening of membrane
o    folds: free edges of membranes or ligaments
o    names: tell you where located

Important membranes:
    quandrangular/vestibular membrane—from epiglottis to arytenoids
•    inferior edge: false vocal fold
    thyrohyoid membrane
    conus elasticus = cricothyroid = cricovocal
•    superior/medial edge = vocal fold
•    vocal ligaments: true folds, top of cricothyroid membrane