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Anatomy - NEETMDS- courses
NEET MDS Lessons
Anatomy

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

The Salivary Glands

  • There are three large, paired salivary glands: the parotid, submandibular, and sublingual glands.
  • In addition to the main salivary glands, there are numerous small accessory salivary glands scattered over the palate, lips, cheeks, tonsils, and tongue.

  • U-shaped bone
  • Body
  • Greater horn
  • Lesser horn
  • Suspended by ligaments from the styloid process
 

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.

The Muscles of Facial Expression

  • These lie in the subcutaneous tissue and are attached to the skin of the face.
  • They enable us to move our skin and change our facial expression. They produce their effects by pulling on the skin but do not move the facial skeleton.
  • These muscles surround the facial orifices and act as sphincters and dilators.
  • All facial muscles receive their innervation from the branches of the facial nerve (CN VII)-temporal, zygomatic, buccal, marginal mandibular, cervical.

Superior Constrictor Muscle

  • Origin: Hamulus, pterygo-mandibular raphe, and mylohyoid line of the mandible.
  • Insertion: Median raphe of the pharynx.
  • Nerve Supply: Vagus nerve via the pharyngeal plexus.
  • Arterial Supply: Ascending pharyngeal artery, ascending palatine artery, tonsillar branch of the facial artery, and dorsal branch of the lingual artery.
  • Action: Constricts the wall of the pharynx during swallowing.

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

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