Respiratory System Functions

• Divided into Upper Respiratory System (face and neck) and Lower Respiratory System (lower neck and thoracic cavity)
• Transports oxygen into the body and carbon dioxide out of the body
• Exchanges occur in the lungs between RBC in capillaries and lung alveoli, and in the body between RBC in capillaries and body cells
• Helps maintain proper acid-base balance of blood by exhaling CO2, reducing carbonic acid in the blood
• Produces vocal sounds through phonation

Upper Respiratory System

• External Nose
  • Consists of root, bridge, dorsum nasi, apex, ala, and external nares (openings)
• Internal Nose
  • Consists of vestibule, nasal turbinate (superior, middle, inferior), nasal meatuses (superior, middle, inferior), and paranasal sinuses
  • Nasolacrimal duct connects to the nasal cavity
• Mouth and Pharynx
  • Oral cavity and pharynx (nasopharynx, oropharynx, laryngopharynx) separated by soft palate
  • Tonsils (lingual, palatine) function to detect pathogens from food and air

Larynx and Trachea

• Larynx
  • Consists of 9 cartilages (3 paired, 3 unpaired)
  • Epiglottis, thyroid cartilage, and cricoid cartilage are the 3 unpaired cartilages
  • Paired cartilages include arytenoid, corniculate, and cuneiform cartilages
  • Vocal folds (vocal cords) produce sound, innervated by recurrent laryngeal nerve
  • Vestibular fold/ligament (false vocal cords) keeps food and drinks out of the airways
• Trachea
  • Located from C6 to T5, dividing into two bronchial trees at T5
  • Carina is a cartilaginous bridge that divides into the two bronchial trees

Trachea Histology

• Mucosa
  • Respiratory epithelium (pseudostratified columnar ciliated epithelium with goblet cells)
  • Goblet cells not stained, but important for mucous production
• Lamina propria
  • Loose connective tissue that attaches respiratory epithelium to submucosa
• Submucosa
  • Contains seromucous glands (serous glands and mucus glands with goblet cells)
• Hyaline cartilage
  • 16-20 C-shaped rings that suspend the airway open
  • Not full rings to avoid interfering with esophagus function

Bronchial Tree

• Primary/Main Bronchi (2)
• Secondary/Lobar Bronchi (3 on the right, 2 on the left)
• Tertiary/Segmental Bronchi (10 on the right, 10 on the left)
• Bronchioles (cartilage rings disappear)
• Terminal Bronchioles
• Respiratory Bronchioles (one per lobule)
• Alveolar Ducts
• Alveoli (Alveoli) – Gas exchange

Alveoli

• Type I cells (Type I Pneumocyte)
  • Simple squamous epithelium for efficient gas diffusion
  • Many capillaries wrap around the alveolus for gas exchange
• Type II cells (Type II Pneumocyte)
  • Secrete surfactant to decrease surface tension, preventing alveolar collapse
  • Allow for easy breathing in and out

Lungs

• Pleura – serous membrane that covers inside of the pleura cavities
• Parietal pleura and Visceral pleura
• Apex projects above Rib 1
• Base sits on diaphragm
• Lungs expand and contract with diaphragm movement
• Surfaces: posterior, costal, anterior, and medial
• Lobes: Right Side (superior, middle, inferior), Left Side (superior, inferior)
• Fissures: Horizontal fissure (between superior and middle lobes), Oblique fissure (between middle and inferior lobes)
• Cardiac Notch – a cut on the left lung for the heart

Nasal Cavity Structure

• The vestibule is the anterior space where air enters after passing through the nares
• Nasal turbinate bones, also known as nasal conchae, have three structures: • Superior nasal conchae: part of the ethmoid bone • Middle nasal conchae: part of the ethmoid bone • Inferior nasal conchae: part of the facial bone

Nasal Meatuses

• Nasal meatuses are tubular pathways created by nasal turbinate bones
• Three types of nasal meatuses: • Superior nasal meatus: below superior conchae • Middle nasal meatus: below middle nasal conchae • Inferior nasal meatus: below inferior nasal conchae

Paranasal Sinuses

• Four types of paranasal sinuses: • Maxillary sinuses: in maxillary bones • Ethmoid air cells: in ethmoid bones • Sphenoid sinuses: in sphenoid bone

Nasolacrimal Duct

• Transports tears from the medial aspect of the orbit to the nasal cavity
• Located below the inferior nasal conchae
• Drains into the inferior nasal meatus

Respiratory System Functions

• The respiratory system is divided into the upper respiratory system (face and neck) and the lower respiratory system (lower neck and thoracic cavity)
• The main functions of the respiratory system are:
  • Transport of oxygen into the body
  • Transport of carbon dioxide out of the body
  • Exchange of oxygen and carbon dioxide occurs at the lungs and the body
  • Help maintain proper acid-base balance of blood
  • Produce vocal sounds through phonation

Upper Respiratory System

• The external nose consists of:
  • Root bridge
  • Dorsum nasi
  • Apex
  • Ala
  • External nares (openings)
• The internal nose consists of:
  • Vestibule
  • Nasal turbinate (aka nasal conchea)
  • Nasal meatuses
  • Paranasal sinuses
  • Nasolacrimal duct
• The nasal turbinate creates tubular pathways called nasal meatuses
  • Superior nasal meatus
  • Middle nasal meatus
  • Inferior nasal meatus

Pharynx

• Divided into three parts:
  • Nasopharynx
  • Oropharynx
  • Laryngopharynx
• Nasopharynx:
  • Receives from middle ear via Eustachian tubes
  • Contains pharyngeal tonsils or adenoids
  • Function as part of immune system, detecting pathogens
• Oropharynx:
  • Separated from nasopharynx by soft palate
  • Contains lingual tonsils and palatine tonsils
  • Tonsils function to detect pathogens from food and air

Larynx

• Location: C4-C6
• Consists of 9 cartilages (3 paired and 3 unpaired)
  • Unpaired cartilages:
    • Epiglottis
    • Thyroid cartilage
    • Cricoid cartilage
  • Paired cartilages:
    • Arytenoid cartilages
    • Corniculate cartilages
    • Cuneiform cartilage
• Vocal fold (vocal cord) produces sound
  • Innervation: recurrent laryngeal nerve (branch of Vagus nerve)
• Vestibular fold (false vocal cords) keeps food and drinks out of the airways

Trachea

• Location: C6-T5
• Divides into two bronchial trees at T5
• Carina: a cartilaginous bridge that divides into two bronchial trees
• Trachea histology:
  • Mucosa:
    • Respiratory epithelium (pseudostratified columnar ciliated epithelium with goblet cells)
    • Lamina propria (loose connective tissue)
  • Submucosa:
    • Contains seromucous glands
    • Hyaline cartilage (16-20 C-shaped hyaline cartilage to suspend airway open)

Bronchial Tree

• 1. Primary/main bronchi (2)
• 2. Secondary/lobar bronchi (3 on the right, 2 on the left)
• 3. Tertiary (third division)/segmental bronchi (10 on the right, 10 on the left)
• 4. Bronchioles
• 5. Terminal bronchioles
• 6. Respiratory bronchioles
• 7. Alveolar ducts
• Alveolus (alveoli) - gas exchange

Alveoli

• Type I cells (Type I Pneumocyte):
  • Simple squamous epithelium
  • Many capillaries wrap around the alveolus
  • Gas exchange occurs here
• Type II cells (Type II Pneumocyte):
  • Secrete surfactant
  • Decrease surface tension, allowing for easier breathing
  • Prevent the collapse of alveoli on exhalation

Lungs

• Pleura: serous membrane that covers the inside of the pleural cavities
  • Parietal pleura
  • Visceral pleura
• Apex: projects above Rib 1
• Base: sits on diaphragm
• Diaphragm contracts and pulls the lungs down, expanding it and allowing for air to enter
• Decreases pressure in lungs, allowing gas to enter