The Respiratory System

Respiration

• Includes ventilation, external respiration, and internal respiration.
• Ventilation involves moving air into and out of the lungs and is also known as breathing.
• External respiration is the gas exchange between air in the lungs and blood.
• Internal respiration is the gas exchange between blood and tissues.
• Function: primarily to obtain oxygen.
• Blood pH is regulated by the bicarbonate system, which is influenced by CO2 levels.
• Chemical mediators such as angiotensin-converting enzyme (ACE) are produced in the lungs to help control blood pressure.
• Voice production occurs through the movement of air past the vocal folds.
• The cavities of the mouth, tongue, and nose contribute to resonance.
• Olfaction refers to the sense of smell.
• Acts as protection preventing the entry of microorganisms.
• Upper respiratory system includes the nose, nasal cavity, pharynx (throat), and larynx (voice box).
• Lower respiratory system consists of the trachea (windpipe), bronchi, and lungs.
• The conducting zone moves air without gas exchange.
• The respiratory zone is where gas exchange occurs, specifically in the alveoli.

Nose & Nasal Cavity

• The nose consists of bones and cartilage.
• External nares are openings in the cartilage that allow air to enter the nasal cavity.
• The nasal vestibule is just inside the nasal cavity and is lined with stratified squamous epithelium and hairs to trap large particles.
• The hard palate, made of the maxillary and palatine bones, separates the nasal and oral cavities.
• Nasal conchae are ridges along the lateral sides increase turbulence and surface area for mucus membranes.
• The superior, middle, and inferior are types of nasal conchae.
• Meatuses are canals between the conchae and act as passageways from the vestibule to the back of the cavity.
• Olfactory epithelium is located in the superior region.
• Paranasal sinuses are air-filled cavities within the bones that are lined with mucus membranes and help lighten the skull and resonate speech.
• Frontal sinus is located in the frontal bone.
• Sphenoidal sinus is located in the sphenoid bone.
• Choanae (internal nares) are openings at the end of the nasal cavity that open into the pharynx.
• The lacrimal duct drains mucus into the inferior meatus and adds moisture to the air.
• Mucus membranes have a highly vascular lining, produce mucus, heat, and moisture.
• The structure of mucous membranes is pseudostratified ciliated columnar epithelium with goblet cells.
• Cilia move mucus towards the pharynx.

Pharynx (Throat)

• The pharynx is a 13 cm muscular tube made of skeletal muscle and mucus membranes.
• The pharynx extends from the choanae to the esophagus.
• Functions as a passageway for food and air, a resonating chamber for speech, and contains tonsils.
• Nasopharynx is the most superior region and runs from the choanae to the soft palate.
• The uvula closes off the nasopharynx and oropharynx during swallowing.
• The auditory tube opens into the nasopharynx and assists with equalizing pressure around the eardrum.
• The pharyngeal tonsil (adenoid) is located in the superior region and carry air.
• Oropharynx runs from the soft palate to the epiglottis and carry both food and air.
• The tonsils in the oropharynx are typically removed.
• The epiglottis closes off the airway when swallowing.
• Fauces are the opening from the oral cavity into the pharynx.
• Palatine tonsils are more superior.
• Inguinal tonsils are more inferior.
• The lining of the oropharynx is stratified squamous epithelium.
• Laryngopharynx runs from the epiglottis to the esophagus.
• The lining of the laryngopharynx is stratified squamous epithelium.
• Laryngopharynx carries food to the esophagus and air to the trachea.

Larynx (Voice Box)

• The larynx consists of 9 pieces of cartilage that allow passage of air from the pharynx to the trachea.
• The cartilage pieces are typically hyaline and are held together by ligaments and muscles, also lined with stratified squamous epithelium.
• Located anterior to the esophagus.
• The epiglottis is an unpaired flap of leaf-shaped elastic cartilage that covers the glottis during swallowing.
• Ligaments attach the epiglottis to the thyroid cartilage, allowing movement.
• The thyroid cartilage is unpaired and more prominent in males (Adam's apple) due to sex hormones.
• The thyrohyoid membrane attaches the thyroid cartilage to the hyoid bone.
• The cricoid cartilage is unpaired and is a ring at the base of the larynx which helps create opening to allow air to enter conducting tube.
• There is a pair of arytenoid cartilages which articulate posteriorly and superiorly with the cricoid. They attach to the vestibular and vocal folds.
• Corniculate cartilages are a pair of small pieces attached to the tips of the arytenoid cartilages.
• Cuneiform cartilages are embedded in the mucus membrane, anterior to the corniculate, and support lateral aspects of the epiglottis and vocal cords.

Laryngeal Folds

• Paired ligaments covered with mucus membranes.
• Vestibular folds: are false vocal cords, lie more superior and cover an area but are not involved in voice production.
• Vocal folds: are true vocal cords, lie more inferior.
• Vocal folds attach to thyroid cartilage on the anterior side and to arytenoid cartilage on the posterior side.
• Open position: muscles contract to abduct the vocal folds by laterally rotating the arytenoid cartilage, used for breathing.
• Closed position: muscles contract to adduct the vocal folds by medially rotating the arytenoid, used for sound production.
• Sound production occurs when air is forced through vocal cords, creating bands of compression.
• Pitch: for higher pitch, the arytenoid is moved posteriorly to increase tension.
• Glottis: space between the vocal cords.

Trachea (Windpipe)

• The trachea consists of 16-20 C-shaped hyaline cartilage rings.
• These rings support dense regular connective tissue and smooth muscle, extending from the larynx to T5 (12 cm).
• Fibromuscular membrane: includes smooth muscle (trachealis) and elastic membrane on the open (posterior) portion of the trachea which allows the esophagus to dilate for swallowing or the trachea to dilate for breathing.
• The carina is bifurcated cartilage located at the base of the trachea which allows branching of bronchi.
• The membrane of the carina is very sensitive, causing a cough reflex.
• The lining is pseudostratified ciliated columnar epithelium with goblet cells.
• The cilia direct mucus and debris to the pharynx.