Innervation Deep Dive
Nerve provides motor innervation to the only intrinsic laryngeal muscle that is a tensor of the vocal cords.
External branch of the Superior Laryngeal Nerve (SLN) (innervates the Cricothyroid muscle).
This large, fan-shaped extrinsic tongue muscle is the bulk of the tongue mass and is responsible for tongue protrusion.
Genioglossus
In an adult, this is the standard distance measured from the incisors to the carina.
26 cm.
Applying digital pressure to this specific point, also known as Larson's point, may relieve a laryngospasm.
Laryngospasm notch (posterior to the earlobe, just anterior to the mastoid process).
This double-layered membrane reflection, located inferior to the hilum, allows for the inferior movement of the lung root during inspiration and the expansion of the pulmonary vein.
Pulmonary Ligament.
While the Vagus nerve (CN X) provides motor innervation to most pharyngeal muscles, this specific muscle is the exception and is innervated by the Glossopharyngeal nerve (CN IX).
Stylopharyngeus
These are the sole abductors of the vocal folds, making them critical for maintaining a patent airway.
Posterior cricoarytenoid muscles
Unlike adults, where the rima glottidis is the narrowest point, this is the narrowest fixed part of the pediatric upper airway.
Cricoid cartilage (subglottic area)
This clinical phenomenon occurs because deoxygenated bronchial venous blood enters the oxygenated pulmonary veins, ultimately decreasing the pO2 of arterial blood.
Venous admixture (or normal anatomic right-to-left shunt)
This specific landmark, found only on the left lung, is a thin, tongue-like extension of the superior lobe that slides in and out of the costomediastinal recess during respiration.
Lingula.
This cranial nerve transmits special sensory information (taste) from the posterior 1/3 of the tongue and serves as the afferent limb of the gag reflex.
Glossopharyngeal nerve (CN IX)
This muscle, located at the level of the C6 vertebra, is tonically contracted to serve as the upper esophageal sphincter.
Cricopharyngeus muscle (part of the Inferior pharyngeal constrictor).
This anatomical landmark, which correlates with the T4-T5 vertebrae posteriorly, marks the bifurcation of the trachea and the start/end of the aortic arch.
Sternal angle (Angle of Louis / Manubriosternal joint)
A "sniff test" under fluoroscopy that shows a hemi-diaphragm rising upward during inspiration indicates this pathology.
Paradoxical movement (signifying ipsilateral phrenic nerve/diaphragm paralysis).
In the tracheobronchial tree, this is the specific generation where gas exchange begins, marking the transition from the conducting zone to the respiratory zone.
Respiratory Bronchioles
Although sympathetic fibers (T1-T4) provide only a weak motor effect on airway diameter, their primary pulmonary roles include these two inhibitory actions.
Vasoconstriction of pulmonary vessels and inhibition of gland secretion.
During active expiration, these specific intercostal muscle layers are responsible for depressing the ribs.
Internal intercostals and the Deep intercostal muscle layer (transversus thoracis, innermost intercostals, and subcostals).
These "communications" allow for collateral ventilation between adjacent alveoli and may facilitate the spread of infection.
Pores of Kohn.
These cells, which replace goblet cells starting at the terminal bronchioles, secrete surfactant apoproteins and can act as progenitors for ciliated cells.
Club cells (formerly Clara cells).
These three specific muscles make up the "Deep Intercostal Muscle Layer," which acts to depress the ribs during active expiration.
Transversus thoracis (anterior), Innermost intercostals (lateral), and Subcostals (posterior).
Sensory innervation to the diaphragm is primarily provided by the phrenic nerves (C3-C5), but these nerves provide sensation to its peripheral edges.
Lower intercostal nerves
Relaxation of this specific soft palate muscle, often seen during sedation, allows the palate to occlude the airway.
Tensor Veli Palatini
This specific region of the anteroinferior nasal septum is a frequent site for chronic epistaxis because it is where branches of the sphenopalatine, ethmoidal, greater palatine, and facial arteries anastomose.
Kiesselbach’s area (or plexus)
This recessed area on either side of the larynx is a common site for foreign bodies to become impacted and is a landmark for blocking the internal laryngeal nerve.
Piriform fossa.
Name the vertebral level where the trachea begins, the vertebral level where the carina is typically located, and the average distance (in cm) from the incisors to that bifurcation in an adult.
Begins at C6; Carina at T4-T5 (Sternal Angle); Distance is 26 cm.