Thyroid gland, Pharynx & esophagus, & Larynx & Trachea Flashcards
cervical visceral layers
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Endocrine layer: thyroid and parathyroid
- Thyroid gland: secretes thyroid hormone (regulation of metabolism) and calcitonin ( Ca concentration in blood)
- Parathyroid gland: parathormone (PTH: Ca concentration in blood)
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Respiratory layer: larynx and trachea
- Conducts air to respiratory tract
- Directs food into alimentary tract
- Producing voice
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Alimentary layer: pharynx and esophagus
- Conducts air to respiratory tract
- Directs food into alimentary tract
- Involved in food propulsion (esophagus)
thyroid gland
Thyroid gland
Location: anterior portion of neck, deep to sternothyroid and sternohyoid muscles, at the level of C5 – T1 vertebrae
Parts
- Lobes (R & L): anterolateral to larynx and trachea
- Isthmus: unites lobes over trachea (anterior to 2-4 tracheal rings)
- Pyramidal lobe: projects superiorly towards thyroid cartilage (not always present)
- Thyroid capsule: fibrous tissue surrounding the gland
Arteries
- Superior thyroid a.: branch of ECA, supply superior portion of the gland
- Inferior thyroid a.: branch of subclavian a., supply inferior portion of gland
Veins
- Superior and middle thyroid vv.: tributary of IJV
- Inferior thyroid v.: tributary of brachiocephalic v.
parathyroid gland
Parathyroid glands
- Location: external to thyroid capsule, on the posterior surface of each lobe of the thyroid gland
- Superior parathyroid glands: lie ~ 1cm superior to point of entry of inferior thyroid a. into thyroid gland
- Inferior thyroid gland: lie ~ 1cm inferior to point of entry of inferior thyroid a. into the thyroid gland
larynx (respiratory layer)
Organ of voice production, and guard air passages during swallowing
Location: in anterior portion of neck, at the level of C3 – C6 vertebral bodies
Boundaries: superoposterior with laryngopharynx and inferiorly is continuous with trachea
thyroid cartilage of the larynx
Thyroid (1): largest laryngeal cartilage
- Laminae: plates that fuse anteriorly and form the laryngeal prominence (Adam’s apple)
- Superior and inferior horns
- Thyrohyoid membrane: attach thyroid cartilage superiorly to the hyoid bone
cricoid cartilage of the larynx
Cricoid (1): complete ring, narrower anteriorly than posteriorly. Lower border (at the level of C6) marks the inferior limit of the larynx
- Cricothyroid ligament: attaches cricoid and thyroid cartilages. The lateral cricothyroid ligament forms the conus elasticus and vocals folds
- Clinical relevance: cricothyrotomy is conducted by performing an incision through the skin and this membrane to create a patent airway
epiglottic cartilage of the larynx
Epiglottic (1): elastic cartilage, attached inferiorly to the junction of the laminae of the thyroid cartilage and with a free superior end
- Epiglottis: epiglottic cartilage covered with mucous membrane, located posterior to root of tongue and hyoid bone and anterior to laryngeal inlet (entry to the larynx from the laryngopharynx)
- Thyroepiglottic ligament: attaches epiglottic cartilage to laminae of thyroid cartilage
arytenoid cartilage of the larynx
Arytenoid (2): pyramidal cartilages that articulate with the superior border of the cricoid cartilage
- Apex: superior portion that bears the corniculate cartilage
- Vocal process: anterior portion that serves as the posterior attachment for the vocal ligament
- Vocal ligaments: extend from the junction of the laminae of thyroid cartilage anteriorly to the vocal process of the arytenoid cartilages posteriorly. Makes up the submucosal skeleton of the vocal folds and is the superior free margin of the conus elasticus
- Quadrangular membrane: sheet of connective tissue extending between the epiglottic and arytenoid cartilages
- Vestibular ligament: inferior free margin of the quadrangular membrane. Makes up the submucosal skeleton of the vestibular fold
- Ary-epiglottic ligament: superior free margin of the quadrangular membrane. Makes up the submucosal skeleton of the ary-epiglottic fold
corniculate cartilage of the larynx
Corniculate (2): connect to the apex of the arytenoid cartilages
cuneiform cartilage
Cuneiform (2): no directly attached to other cartilages
*laryngeal cavity
Laryngeal inlet
communicates posteriorly with the laryngopharynx
Vestibule
between laryngeal inlet and vestibular folds
Vestibular folds
on the lateral wall of larynx, at the lower end of vestibule. Inferior free margin of quadrangular membrane
Infraglottic cavity
between vocal folds and inferior border of cricoid cartilage. It’s continuous with trachea
Glottis
comprised by the vocals folds and rima glottidis
Rima glottidis
aperture between vocals folds
Rima vestibuli
space between vestibular folds
Conus elasticus
lateral portion of the cricothryoid ligament. Its free superior margin forms the vocal ligament
intrinsic mm of larynx (respiratory layer)
- Provide protection and adjustment of larynx and vocal cord during phonation and respiration
- Involved in sound production and opening and closing the airway during respiration
- Move laryngeal components, altering the length and tension of the vocal folds and shape of the rima glottidis
- All innervated by the recurrent laryngeal nerve (CN X), except cricothyroid m. innervated by the external laryngeal nerve (CN X)
extrinsic mm of larynx (respiratory layer)
work on the larynx as a whole. Move the larynx as an entire organ, while the intrinsic muscles make adjustments
- Infrahyoid muscles: depressors of hyoid and larynx
- Suprahyoid muscles: elevators of the hyoid and larynx
arteries of larynx
Superior and inferior laryngeal arteries: branches of the superior and inferior thyroid aa. Same aa. supplying the thyroid supply the larynx
veins of larynx
Superior and inferior laryngeal veins: drain into superior thyroid v
innervaion of larynx
CN X
. Persistent hoarse voice is an indication that someone may have vagus nerve problems
- Superior laryngeal:
- External: motor to cricothyroid (intrinsic muscle of larynx)
- Internal: sensory and parasympathetic to inside of larynx
- Recurrent laryngeal: motor to all other intrinsic muscles of larynx. Goes inferiorly and curves below the subclavian on right and below the aortic arch on left going between the trachea and esophagus.
Trachea (respiratory layer)
- Fibrocartilagenous tube supported by incomplete cartilagenous rings (tracheal cartilages)
- Location: extends from the larynx (at the level C6) inferiorly into the thorax (at the level T4 or sternal angle), where it divides into R & L bronchi
- Anterior and median in the neck
- Anterior to the esophagus, and intimately related anatomically to it. They are hard to separate from each other
- Medial to common carotid aa.
- Anterior to lobes of the thyroid gland, and posterior to isthmus of thyroid gland
- Function: transports air to and from lungs
pharynx (alimentary layer)
- Superior expanded part of alimentary system
- Location: extend from cranial base to inferior border of the cricoid cartilage (at the level of C6), where is continuous with the esophagus
- Division
- Nasopharynx: posterior to nose and superior to soft palate
- Oropharynx: posterior to mouth, and below soft palate
- Laryngopharynx: posterior to the larynx
nasopharynx
Posterior extension of nasal cavities, involved in respiration
Pharyngeal tonsils: lymphoid tissue masses on the superior and posterior aspect of the nasopharynx.
- Clinical relevance: commonly called adenoids and many times removed (adenoidectomy) when swollen and blocking airflow in the nasal passage
Opening of pharyngotympanic tube: on lateral wall of nasopharynx
Torus of the pharyngotympanic tube (torus tubarius): rim of tissue around opening pharyngotympanic tube, formed by the cartilage of the auditory tube as it pokes the lateral wall of the nasopharynx
Salpingopharyngeal fold: fold of tissue that extends down from torus of the pharyngotympanic tube. It is mucus membrane covering the salpingopharyngeus m.
Pharyngeal recess: lateral and posterior projection of the pharynx, posterior to the salpingopharyngeal fold
Oropharynx
- Boundaries: S: soft palate; I: root of tongue; L: palatoglossal & palatopharyngeal arches
- Location: extends inferiorly from the soft palate to the superior border of the epiglottis, and is involved in digestion
- Palatine tonsils: mass of lymphoid tissue on each side of oropharynx, between the palatine arches (palatoglossal & palatopharyngeal)
- Clinical relevance: tonsillectomy involves the removal of the tonsils, when inflamed, and many times is conducted in combination with an adenoidectomy. The ICA lies posterolateral to the tonsillar bed, and a mistake during tonsillectomy could be disastrous
laryngopharynx
- Location: posterior to the larynx, extends from the superior border of the epiglottis to the inferior border of the cricoid cartilage, where it becomes continuous inferiorly with the esophagus
- Laryngeal inlet: communicates the laryngopharynx posteriorly with the larynx anteriorly
- Piriform fossa (recess): small depression of the laryngopharynx on either side of pharyngeal inlet.
pharyngeal mm
External circular layer
- Pharyngeal constrictors: Superior, Middle, Inferior
- Contraction: involuntary and sequential from superior to inferior end of the pharynx
Internal longitudinal layer
- Palatopharyngeous
- Salpingopharyngeous
- Stylopharyngeous
Pharyngobasilar fascia: strong internal fascial lining of the pharyngeal constrictor muscles
Buccopharyngeal fascia: thin external fascial lining of the pharyngeal constrictor muscles
pharyngeal plexus of nerves: on lateral wall of pharynx
Pharyngeal branches of CN X, CN IX
Sympathetic fibers from superior cervical ganglion
esophagus (alimentary layer)
- Muscular tube connecting the pharynx to the stomach, posterior to the trachea in cervical region
- Extends from the laryngopharynx superiorly (at the level of C6 and inferior border of cricoid cartilage) to the stomach in the abdomen
- Muscular distribution
- Superior 1/3rd: striated
- Middle 1/3rd: striated and smooth
- Inferior 1/3rd: smooth
- Cervical esophagus: part of the voluntary upper 1/3rd
- Superior esophageal sphincter: cricopharyngeal part of the inferior pharyngeal constrictor muscle
