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