NEET MDS Lessons
Anatomy
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
- The palate has a rich blood supply from branches of the maxillary artery.
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
|
Pharyngeal Arch |
Arch Artery |
Cranial Nerve |
Skeletal elements |
Muscles |
|
1 |
Terminal Branch of maxillary artery |
Maxillary and mandibular division of trigemenial (V) |
Derived from arch cartilages (originating from neural crest): From maxillary cartilages: Alispenoid, incus From mandibular: Mackel’s cartilage, malleus
Upper portion of external ear (auricle) is derived from dorsal aspect of 1st pharyngeal arch.
Derived by direct ossification from arch dermal mesenchyme: Maxilla, zygomatic, squamous portion of temporal bone, mandible
|
Muscles of mastication (temporalis, masseter, and pterygoids), mylohyoid, anterior belly of digastric, tensor tympani, tensor veli palatini (originate from cranial somitomere 4) |
|
2 |
Stapedius artery (embryologic) and cortiotympanic artery (adult) |
Facial nerve (VII) |
Stapes, styloid process, stylohyoid ligament, lesser horns and upper rim of hyoid (derived from the second arch cartilage; originate from neural crest).
Lower portion of external ear (auricle) is derived from 2nd pharyngeal arch. |
Muscles of facial expression (orbicularis oculi, orbicularis oris, auricularis, platysma, fronto-ooccipitalis, buccinator), posterior belly of digastric, stylohyoid, stapedius (originate from cranial somitomere 6) |
|
3 |
Common carotid artery, most of internal carotid |
Glossopharyngeal (IX) |
Lower rim and greater horn of hyoid (derived from the third arch cartilage; originate from neural crest cells) |
Sytlopharyngeus (originate from cranial somitomere 7) |
|
4 |
Left: Arch of aorta; Right: Right subclavian artery; Original sprouts of pulmonary arteries |
Superior laryngeal branch of vagus (X) |
Laryngeal cartilages (Derived from the 4th arch cartilage, originate from lateral plate mesoderm) |
Constrictors of pharynx, cricothyroid, levator veli palatine (originate from occipital somites 2-4) |
|
6 |
Ductus arteriosus; roots of definitive pulmonary arteries |
Recurrent laryngeal branch of vagus (X) |
Laryngeal cartilages (derived from the 6th-arch cartilage; originate from lateral plate mesoderm) |
Intrinsic muscles of larynx (originate from occipital somites 1 and 2) |
Muscles Around the Eyelids
- The function of the eyelid (L. palpebrae) is to protect the eye from injury and excessive light. It also keeps the cornea moist.
The Orbicularis Oculi Muscle
- This is the sphincter muscle of the eye.
- Its fibres sweep in concentric circles around the orbital margin and eyelids.
- It narrows the eye and helps the flow of tears from the lacrimal sac.
- This muscle has 3 parts: (1) a thick orbital part for closing the eyes to protect then from light and dust; (2) a thin palpebral part for closing the eyelids lightly to keep the cornea from drying; and (3) a lacrimal part for drawing the eyelids and lacrimal punta medially.
- When all three parts of the orbicularis oculi contract, the eyes are firmly closed and the adjacent skin becomes wrinkled.
- The zygomatic branch of the facial nerve (CN VII) supplies it.
The Levator Palpebrae Superioris Muscle
- This muscle raises the upper eyelid to open the palpebral fissure.
- It is supplied by the oculomotor nerve (CN III).
The Middle Ear
- This part of the ear is in a narrow cavity in the petrous part of the temporal bone.
- It contains air, three auditory ossicles, a nerve and two small muscles.
- The middle ear is separated from the external acoustic meatus by the tympanic membrane.
- This cavity includes the tympanic cavity proper, the space directly internal to the tympanic membrane, and the epitympanic recess, the space superior to it.
- The middle ear is connected anteriorly with the nasopharynx by the auditory tube.
- Posterosuperiorly, the tympanic cavity connects with the mastoid cells through the aditus ad antrum (mastoid antrum).
- The tympanic cavity is lined with mucous membrane that is continuous with the mucous membrane of the auditory tube, mastoid cells, and aditus ad antrum.
Contents of the Tympanic Cavity or Middle Ear
- This cavity contains the auditory ossicles (malleus, incus and stapes); the stapedius and tensor tympani muscles; the chorda tympani nerve (a branch of the facial nerve, CN VII); and the tympanic plexus of nerves.
The Tongue
- The tongue (L. lingua; G. glossa) is a highly mobile muscular organ that can vary greatly in shape.
- It consists of three parts, a root, body, and tip.
- The tongue is concerned with mastication, taste, deglutition (swallowing), articulation (speech), and oral cleansing.
- Its main functions are squeezing food into the pharynx when swallowing, and forming words during speech.
Gross Features of the Tongue
- The dorsum of the tongue is divided by a V-shaped sulcus terminalis into anterior oral (presulcal) and posterior pharyngeal (postsulcal) parts.
- The apex of the V is posterior and the two limbs diverge anteriorly.
- The oral part forms about 2/3 of the tongue and the pharyngeal part forms about 1/3.
Oral Part of the Tongue
- This part is freely movable, but it is loosely attached to the floor of the mouth by the lingual frenulum.
- On each side of the frenulum is a deep lingual vein, visible as a blue line.
- It begins at the tip of the tongue and runs posteriorly.
- All the veins on one side of the tongue unite at the posterior border of the hyoglossus muscle to form the lingual vein, which joins the facial vein or the internal jugular vein.
- On the dorsum of the oral part of the tongue is a median groove.
- This groove represents the site of fusion of the distal tongue buds during embryonic development.
The Lingual Papillae and Taste Buds
- The filiform papillae (L. filum, thread) are numerous, rough, and thread-like.
- They are arranged in rows parallel to the sulcus terminalis.
- The fungiform papillae are small and mushroom-shaped.
- They usually appear are pink or red spots.
- The vallate (circumvallate) papillae are surrounded by a deep, circular trench (trough), the walls of which are studded with taste buds.
- The foliate papillae are small lateral folds of lingual mucosa that are poorly formed in humans.
- The vallate, foliate and most of the fungiform papillae contain taste receptors, which are located in the taste buds.
The Pharyngeal Part of the Tongue
- This part lies posterior to the sulcus terminalis and palatoglossal arches.
- Its mucous membrane has no papillae.
- The underlying nodules of lymphoid tissue give this part of the tongue a cobblestone appearance.
- The lymphoid nodules (lingual follicles) are collectively known as the lingual tonsil.