Respiratory System Anatomy

• The respiratory system is composed of several organs that oxygenate the body through respiration (breathing) involving inhaling air and delivering it to the lungs, where gas exchange takes place.

Divisions of the Respiratory Tract

• Anatomically, it is split into upper and lower sections at the vocal cords
• The upper respiratory tract includes the nasal cavity, paranasal sinuses, pharynx, and the part of the larynx above the vocal cords
• The lower respiratory tract includes the larynx below the vocal cords, the trachea, bronchi, bronchioles, and the lungs
• Functionally, the tract is divided into the conducting part which forms the nasal cavities, pharynx, larynx, trachea, bronchi and bronchioles
• Also the respiratory part (lung respiratory bronchioles, alveolar ducts, and alveoli)

Nose

• The interior of the nose has a nasal cavity divided by a nasal septum
• Olfactory receptors are in the mucosa on the superior surface and upper parts of medial and lateral walls while the remainder of the cavity is lined with respiratory mucosa.

Paranasal Sinuses

• These are air-filled spaces associated with bones like the maxillary, frontal, sphenoidal, and ethmoidal sinuses
• They communicate with the nasal cavity through several openings

Pharynx

• Is a fibromuscular tube that extends from the base of the skull to the sixth cervical vertebrae posteriorly and the lower border of the cricoid cartilage anteriorly
• The parts include nasal, oral, and laryngeal
• The nasopharynx, the backward extension of the nasal cavities, connects the nasal cavity with the tympanic cavity, and serves a respiratory function

Larynx

• The larynx, anterior to the esophagus, connects to the trachea below and opens at the lowest part of the pharynx
• It has a mucous membrane internally and is covered in voluntary muscles externally
• There are 9 cartilages:
• Single cartilages:
  • Thyroid cartilage: Features the laryngeal prominence (Adam's apple) anteriorly.
  • Cricoid cartilage: Is a complete ring
  • Epiglottic cartilage: a leaf that attached to angle of the thyroid cartilage
• Paired cartilages:
  • Arytenoid cartilages: Paired, small, and pyramidal
  • Bases articulate with the upper border of the lamina of the cricoid cartilage
  • Corniculate cartilages: One on each side and are small nodules
  • Articulates with apices of arytenoid cartilage
  • Cuneiform cartilages: Two small, rod-shaped pieces lying in front of the corniculate cartilage

Tracheobronchial Tree

• It conducts air from the upper airways to the lungs and consists of the trachea, bronchi, and bronchioles
• The trachea sits in the superior mediastinum, representing the trunk
• The trachea spans extends from the lower border of the cricoid cartilage and bifurcates at the level of the sternal angle (T5) into the left and right main bronchi
• The right and left main bronchi goes inferolaterally to the hilum of the right and left lungs, respectively
• The right main bronchus has a more vertical path, is wider and shorter than the left, increasing susceptibility to foreign body impaction

Respiratory Tree Divisions

• Primary Bronchi
• Secondary Bronchi
• Tertiary Bronchi
• Bronchioli
• Terminal Bronchioli

Anatomy of the Lungs

• Lungs primarily fill the thoracic cavity, with a generally conical shape
• Lies next to one another in the mediastinum
• The medial aspect of each lung, where structures enter and exit, defines the hilum
• The structures connecting lungs to the mediastinum include the bronchus (Rt and Lt), bronchial vessels, pulmonary artery, two pulmonary veins, pulmonary nerve plexuses, and bronchopulmonary lymph nodes and lymphatics
• Lungs are spongy organs within the thoracic cavity
• The right lung has three lobes (superior, middle, inferior) divided by oblique and horizontal fissures and is larger than the left
• The left lung has two lobes (superior, inferior), divided by one oblique fissure

Anatomy of the pleura

• The pleura is a serous membrane folding on itself to create a double-layered membranous pleural sac
• The outer layer is called the parietal pleura
• The inner layer is called the visceral pleura, covering the lungs, blood vessels, nerves, and bronchi

The Diaphragm

• The diaphragm, a double-domed musculotendinous sheet at the lowest part of the rib cage, performing two main functions
• Separates the thoracic and abdominal cavities and undergoes contraction and relaxation, altering the volume of the thoracic cavity and the lungs
• Important openings in the diaphragm:
• Vena caval opening: at the level of the eighth thoracic vertebra
• Esophageal opening: at the level of the tenth thoracic vertebra
• Aortic opening: at the level of the last thoracic vertebra