Anatomy: Larynx and Mediastinum

• ΑΝΑΤΟΜΙΑ is the subject
• Addressed to the IΑΤΡΙΚΗ ΣΧΟΛΗ (Medical School)
• Intended for the 2nd year
• For the academic year 2022-2023
• Taught by ΧΑΡΑΛΑΜΠΟΣ ΧΑΡΑΛΑΜΠΙΔΗΣ and ΓΕΩΡΓΙΟΣ ΠΑΦΙΤΑΝΗΣ

Respiratory System

• Focus is on the Larynx & Mediastinum
• The Respiratory system enables breathing
• Facilitating the intake of O2
• Expelling CO2
• Embryologically, the Respiratory system orginates as a part of the digestive system

Upper & Lower Airways

• Upper airway includes the nose and pharynx
• Specifically including the nasal, oral, and laryngeal parts
• Lower airway comprises the larynx, trachea, bronchi, and lungs

Larynx and Terrestrial Life

• Larynx adaptations are due to the demands of terrestrial life
• These adaptation meet increased oxygen demand for movement and respiration
• It protects the lower respiratory tract via coughing
• It is involved in swallowing

Larynx as an Organ

• As an airway, it acts as a sphincter, controlling entry to the lower airway
• It protects the lungs and preventing aspiration, cough, and phlegm
• It supports abdominal pressure
• It participates in swallowing
• Acts as the vocal organ, related to the position and function of the larynx

Key Notes on Larynx Location

• Position and voice quality are influenced by singer's posture
• Position affects swallowing
• In newborns and breastfeeding mammals is differs
• Also location influences tracheotomy

Topography of Larynx

• The larynx is located in the neck
• It is beneath the skin and superficial cervical fascia
• It is positioned inferior to the hyoid bone, between major blood vessels
• It lies anterior to the laryngeal part of the pharynx
• Superior border corresponds to the upper surface of vertebra Α3
• Inferior border corresponds to the lower surface of vertebra Α6
• In females, it is 0.5-1 vertebrae higher
• Its position varies depending of head flexion-extension, speech, swallowing, coughing, and phonation

Dimensions of Larynx

• The larynx is related to stature
• The sagittal diameter increases in men during puberty
• Also increases in castrated men
• Length is 44 or 70 mm (36)
• Transverse diameter is 43 mm (41)
• Sagittal diameter is 36 mm (26)

Anatomy of Larynx

• The construction consists of:
• Cartilages-Ligaments/Joints
• Muscles
• Cavity-Mucosa
• Vasculature and Nerves

Laryngeal Cartilages

• Single cartilages:
• Thyroid
• Cricoid
• Epiglottis
• Paired cartilages:
• Arytenoid
• Corniculate
• Cuneiform
• Composed of hyaline cartilage and elastic cartilage

Cricoid Cartilage

• It's the basic cartilage of the larynx
• It forms the lowest part
• It constitutes the posterior and the narrowest part of the anterior wall of the larynx
• It consists of two parts:
• Arch(anterior) - with thyroid articular surfaces
  • Palpable (5-7mm)
• Lamina (posterior)
  • Measures 20-30 mm in length and width
  • Presents anterior and posterior surfaces
  • Has a median longitudinal crest, superior and Inferior border
  • Also has an arytenoid articular surface

Arytenoid Cartilages

• Located on the upper border of the cricoid cartilage lamina
• They form the posterior part of the larynx
• They are functionally significant and important for vocal cords attachment
• They have irregular, triangular pyramid shapes, approximately 15 mm in size

Features of Arytenoid Cartilages

• Apex articulates w/ corniculate cartilage
• It's base articulates w/ cricoid cartilage
• Vocal process has attachment for the vocalis muscle and vocal ligament
• Muscular process has attachment for two cricoarytenoid muscles
• On the Posterior (Posterior-External) surface there's the arcuate crest/triangular fovea/ oblong fovea
• Has medial/internal and anterior/external surfaces

Thyroid Cartilage

• It's the largest laryngeal cartilage that makes up main anterior and lateral walls
• Two quadrilateral plates: four borders, two surfaces
• Presents laryngeal prominence (Adam's Apple)
• Anterior border: thyroid angle (90° is typical for males; 120° is typical for females)
• Posterior border: upper-lower thyroid horns

Further Anatomy of Thyroid Cartilage

• Superior border presents thyroid notch
• Inferior border presents inferior thyroid tubercle
• Internal surface
• External surface presents the superior tubercle/oblique line

Epiglottis Details

• It's an elastic, yellowish cartilage leaf shape, 2 mm thick
• Enlarged in ruminants for olfactory function during prolonged feeding
• The anatomy includes a petiole, superior free border (base), anterior surface (hyoepiglottic ligament) and posterior surface

Corniculate-Cuneiform Cartilages

• Corniculate cartilages: located at apex of arytenoid, presenting a corniculate tubercle
• Cuneiform cartilages: expansion from epiglottis

Articulations of the Larynx

• CricoThyroid Joint
• Involves superior, inferior, and anterior cricothyroid ligament
• It is moves to change between the arch of cricoid to lower ridge of thyroid
• Influences position of glottis and the tension of the vocal cords

Other Joints of Larynx

• Cricoarytenoid Joint:
• Influences glottis
• Arytaenocorniculate Joint
• Modifies glottis

Ligaments of the Larynx

• They maintain position
• Ligamens connect to adjacent organ

Main Ligaments of Larynx

• Connections to adjacent organs
• Middle hyothyroid ligament between: thyroid notch and upper edge of hyoid bone
• Lateral hyothyroid ligaments connects superior thyroid horns with the greater horn tubercle
• Hyothyroid membrane between the medium-lateral hyothyroid ligament
• It contains adipose tissue
• The hyoepiglottic ligament, the cricotracheal ligament,

Connections between Cartilages

• The connections involving cartilages are:
• The arytenoepiglottic ligament
• The vocal ligament
• The cricothyroid ligament

Muscles of the Larynx

• There are both extrinsic and intrinsic muscles

Extrinsic Muscles of the Larynx

• Laryngopharyngeal transports larynx in superior-posterior direction
• Sternothyroid transports larynx inferiorly
• Thyrohyoid transports larynx superiorly
• All anterior cervical muscles are indirectly related

Intrinsic Muscles of the Larynx

• Embryonic origin is both internal and external
• They are located anterior, posterior and lateral
• The muscles act on the Glottis and Larynx opening

Key Intrinsic Muscles of Larynx

• Cricothyroid: originates on the out surface of cricoid ring and inserts into the inferior border of the thyroid cartilage
• Posterior cricoarytenoid: originates on the posterior lamina of the cricoid cartilage and inserts into the muscle process of the arytenoid cartilage
• Lateral cricoarytenoid: originates at the superior border of the cricoid cartilage
• Inserts muscular process of the arytenoid cartilage
• Transverse arytenoid: spans between arytenoid cartilages
• Inserts muscular process of the arytenoid cartilage

Other Intrinsic Muscles

• Oblique arytenoid crosses and inserting into the arytenoid muscle
• Thyroarytenoid originate within the Thyroid cartilage, and insert to the arytenoid

Vocalis Muscle and Ligament

• Vocalis Muscle thickens, and leads to Vocal Fold
• Ventricular Muscle, leading leads to Ventricular Fold

Categorization of Muscles

• Extrinsic or Intrinsic origin
• Anterior, posterior, or lateral position on larynx
• Act at larynx opening or at glottis

Intrinsic muscles grouped by action at larynx opening

• Oblique arytenoid, Aryepiglottic muscles, and transverse arytenoid are constrictors

Intrinsic Muscles Grouped by Impact on Glottis Size

• Abductors: Posterior cricoarytenoid
• Adductors: Lateral cricoarytenoid
• Transverse arytenoid, Oblique arytenoid and Thyroarytenoid
• Modifies position and shape of glottis

Intrinsic Muscles Grouped by Impact on Vocal Fold Length & Tension

• Cricothyroid increases the length and tension
• Posterior Cricoarytenoid is partially involved with increasing the length and tension
• Thyroarytenoid increases/decreases
• Vocalis does the fine tuning

Summarized Action on the Glottis

• Contraction of the:
• Cricothyroid tightens the glottis
• Posterior cricoarytenoid widens the glottis
• Lateral cricoarytenoid also tightens the glottis
• Transverse arytenoid tightens the glottis
• Thyroarytenoid close the vocal cords

Laryngeal Mucosa

• Epithelium is ciliated pseudoColumnar (vocal cords=stratified squamous)
• The Chorion is connective tissue
• There are Glands present to moisten the vocal cords

Cavity of Larynx

• There is the pharyngeal foramen and the tracheal foramen
• Consisting of superior, middle and inferior subregions
• Shaped like an hourglass

Pharyngeal Opening of Larynx

• This is superior and posterior of the larynx
• Anterior: base of the Epiglottis
• Posterior: Arytenoid cartilages and interarytenoid notch
• Lateral: Aryepiglottic fold

Tracheal Opening of Larynx

• Equivalent with inferior border of cricoid cartilage
• Lining of the trachea artery

Upper Larynx Subregion

• The upper part of the larynx
• It contains the Epiglottis and ventricular fold

Middle Larynx Subregion

• It is narrower than the other regions because of Ventricular folds
• Contains ventricular folds/ false vocal cords that does not participate in phonation
• Also contains vocal folds/ true vocal cords- two whitish fold that abuts the glottis and that participate in the function of phonation
• There is also the Laryngeal Ventricle

Inferior Larynx Subregion

• Nothing particularly notable

Why Women Have Higher Voices

• Higher Larynx position
• Shorter Vocal Cord Length

Vascularture & Innervation of Larynx

• Vascular Supply: Superior, Middle, and Inferior laryngeal artery
• Venous Drainage: internal jugular/Unnamed vein
• Lymphatic Drainage: pre-Laryngeal, paratracheal
• Sympathetic/Superior-Inferior Laryngeal Nerve,
• Superior laryngeal nerve supplies the cricothyroid muscle
• Inferior laryngeal nerve supplies the others

Mediastinum

• Space in the thorax between the lungs
• Bounded laterally by mediastinal pleura

Delimiting Mediastinum

• Superior border: upper thoracic aperture, slanting (anteriorly and inferiorly) from the manubrium of sternum to first thoracic vertebra
• Inferior border: diaphragm
• Anterior border: posterior surface of sternum
• Posterior border: bodies of the thoracic vertebrae, adjacent posterior parts of ribs

Peritoneal & Visceral Covering of Mediastinum

• Consist of the Serosa

Topography

• Top: superior
• Divided into Superior Mediastinum
• Anterior, Middle and Posterior Subregions of the Inferior Mediastinum

Superior Mediastinum

• The structures found here are divided into the Thymus (remnants), Trachea, Esophagus and great blood vessels
• This also includes nerves and lymphatic vessels

Anterior Subregion of the Inferior Mediastinum

• The anterior border of sternum, and inner surface of pericardium
• It is occupied by Thymus and lipids

Medial Subregion of the Inferior Mediastinum

• Located to the anteromedial wall of the pericardium
• the structures include the pulmonary vein