Biology 260 M. Iyengar Embryological Development of the Respiratory System • At the 4th week the lung bud develops ventrally from the endodermal tube – The tube branches to form the respiratory tree – Mesoderm around the respiratory tree becomes blood vessels, muscles and cartilage • Alveoli start developing in weeks 16-28 • Respiratory system begins functioning after birth. The Respiratory System Functions
• Main Function: – Respiration - the ENTIRE process of gas exchange in the body. • Pulmonary ventilation + gas transport + gas exchange
• Supply the body cells with O2 – Why does the body need oxygen?
• Dispose of CO2 that cells create
• Additional Functions: – Filters, warms, and moistens air – Regulate blood pH – Produces sound and smell receptors Respiratory System
ANATOMICAL Divisions: FUNCTIONAL Divisions: UPPER 1. Conducting Zone • Nose • Connected cavities and – Nasal cavity & Paranasal sinuses tubes that filter, warm, moisten and conduct air • Pharynx into the lungs. – Nasopharynx, Oropharynx, Laryngopharynx • Larynx LOWER • Trachea • Bronchial Tree 2. Respiratory Zone – Primary, secondary, tertiary, bronchioles • Tissues that facilitate • Lungs gas exchange between – Alveoli air and blood. Diaphragm The Respiratory System Anatomy
Conducting Zone
Nasal cavity Oral cavity Nostril Pharynx UPPER Left main Larynx (primary) bronchus LOWER Trachea Carina of trachea Right main (primary) bronchus
Right lung
Diaphragm Respiratory Zone The Upper Respiratory Tract Nose Anatomy: • External nares = nostrils • Nasal, frontal, & maxillary bones + hyaline cartilage (alar and septal) • Nasal septum = internal division – Perpendicular plate of the ethmoid bone & vomer – Divides nose into the left and right Nasal Cavity Anatomy • Space inside the internal nose, connects to the pharynx – Lined with pseudostratified ET + goblet cells + olfactory ET – Roof is the cribriform plate of the ethmoid bone, floor is the maxillae & palatine bones – Conchae – extensions that increase surface area • Superior • middle • Inferior Nose & Nasal Cavity Functions
1. Filtering, warming and moistening incoming air – Respiratory mucosa → produces mucus to moisten the air and trap bacteria and send them to the stomach (via throat)…Yum! – Rich network of small veins → warms the air – Contain nasal hair → collect and remove dust
2. Detecting smell → olfactory receptors
3. Modify vibrations of sound for speech Paranasal Sinuses
• Hollow cavities within the skull bones associated with the nasal cavity. • Frontal • Maxillary • Sphenoid • Ethmoid
• Help lighten the skull, help voice resonance and secrete mucus Pharynx • Funnel-shaped passageway for food and air. – Skeletal muscles lined with mucus membrane • Chamber for resonating speech and contains tonsils Pharynx Nasopharynx • Posterior to the nasal cavity and above soft palate – Only an air passageway – Closed off during swallowing – Pseudostratfied ciliated columnar ET
• Pharyngeal tonsil – Located on posterior wall – Destroys entering pathogens Pharynx = Throat Oropharynx • Arch-like entranceway of the oral cavity – Passageway for both food and air – Extends from soft palate to the epiglottis – Stratified squamous ET • Palatine tonsils – in the lateral walls • Lingual tonsils – covers the posterior surface of the tongue
Laryngopharynx • Area that opens into larynx and esophagus – Passageway for both food and air – Stratified squamous ET Larynx
• The cartilaginous structure that surrounds and protects the glottis – Glottis – narrow opening in the larynx where air from the pharynx moves to the trachea
• Three functions: 1. Provides an open airway 2. Routes air and food into the proper channels 3. Voice production Larynx
Anatomy Functions 1. Thyroid cartilages – Large anterior 1. Thyroid & Cricoid cartilages shield attached to the hyoid bond (hyaline) - protect the glottis • Laryngeal prominence – where and entrance to the trachea 2 thyroid cartilage plates fuse 2. Epiglottis (elastic) – leaf- 2. Cricoid cartilages – inferior, ring- shaped lid, that closes over shaped attached to the trachea the glottis when food enters 3. Epiglottis – leaf-shaped lid, posterior aspect of the tongue to the pharynx the thyroid cartilage 3. Arytenoid & Corniculate 4. Arytenoid, cuneiform & cartilage (hyaline) – open & corniculate cartilage– lateral & close the glottis and assist posterior walls of the larynx with sound production Anatomy of the Larynx Label the Larynx Vocal Cords
• Vocal folds (true vocal cords) – ligaments of elastic fibers create the mucosal folds – Air rushes up from the lungs and vibrates the vocal folds • Vestibular folds (false vocal cords) – mucosal folds superior to the vocal folds. – Help to close the glottis during swallowing Trachea
• Descends from the larynx into the mediastinum • Anterior to the esophagus • Carina = Inferior tracheal cartilage
Histology: • Mucosa – ciliated pseudostratified with goblet cells • Submucosa – CT & seromucous glands • Hyaline cartilage - C-rings (16-20) that help keep the tube open – Smooth muscle supports the tracheal cartilages, closes the circle of C-ring – Helps adjust air flow to lungs • Adventitia – outer CT layer Trachea = Windpipe Bronchi in the Conducting Zone • Bronchial tree – extensively branching respiratory passageways 1. Primary (main) bronchi– largest, & 1st branches off the trachea – Right is wider and shorter than the left. – Why? 2. Secondary (lobar) bronchi – One per lung lobe • Three on the right • Two on the left 3. Tertiary (segmental) bronchi – Branch off secondary bronchi 4. Bronchioles – little bronchi, less than 1 mm in diameter 5. Terminal bronchioles – less than 0.5 mm in diameter Bronchi in the Conducting Zone Anatomical Changes to Bronchi Structure
• Cartilage – Rings become irregular plates – Walls of the tube contain elastic fibers
• Epithelium – Pseudostratified columnar → columnar → cuboidal – Mucus cells and cilia are reduced in bronchioles
• Smooth muscle – Increases as the passageways become smaller The Respiratory Zone • Consists of air-exchanging structures • Begins with terminal bronchioles becoming respiratory bronchioles – Terminal bronchiole → Respiratory bronchiole → alveolar ducts → alveolar sac → alveoli Alveoli • Epithelial cell surrounded by fine elastic fibers and pulmonary capillaries • Interconnect by alveolar pores
• Respiratory membrane – Cell types: • Type I alveolar cells = Simple squamous – Alveolar pores connect one alveoli to another • Type II alveolar cells = Simple cuboidal – Septal cells - Secrete surfactant that help reduce friction • Alveolar macrophages – remove infectious pathogens Anatomy of Alveoli and Respiratory Membrane Location of Lungs • Occupy the thoracic cavity – Apex – pointed end near the clavicle – Base – rounded end the rests on the diaphragm – Right Lung – Larger, three lobes – Left Lung – Smaller, two lobes & cardiac notch
Clavicle Lung Rib 3 Rib 4 8 5 Nipple 9 6 Lung 10 7 12 8 11 Parietal Midaxillary Parietal pleura line 9 Infrasternal pleura angle at the 10 xiphisternal Midclavicular line joint Costal margin (a) Posterior view (b) Anterior view Figure 22.13 The Pleurae
• A double-layered serosa sac surrounding each lung – Parietal pleura – lines thoracic cavity walls – Visceral pleura – lines lung walls – Pleural cavity – space between the two layers filled with fluid • Allows for friction free movement Anatomy of the Lungs • Hilum – groove where bronchus, blood vessels and nerves access the lungs • Right lung (horizontal and oblique fissure) – Superior lobe – Middle lobe – Inferior lobe • Left lung (oblique fissure) – Superior lobe – Inferior lobe – Cardiac notch Blood Supply and Innervation of the Lungs • Pulmonary arteries – deliver oxygen-poor blood to the lungs – Branch into pulmonary capillary networks around alveoli • Pulmonary veins – carry oxygenated blood to the heart • Bronchial arteries – supply oxygenated blood and nutrients to the lung tissue Pulmonary Ventilation
Inhalation/ Inspiration Exhalation / Expiration 1. Contraction of muscles 1. Inspiratory muscles relax – Diaphragm contracts → flattens – Diaphragm relaxes → dome shaped – External intercostal muscle – External intercostal relaxes → contract → lift the rib cage thoracic cavity volume decreases 2. Thoracic cavity volume 2. Decrease of thoracic cavity increase → Lung volume volume → lung volume increases decreases 3. Lung pressure decreases 3. Lung pressure increases compared to atmospheric compared to atmospheric pressure → partial vacuum pressure 4. Air moves into the lungs 4. Air moves out of lungs (high→ (high → low pressure) until low pressure) until pressure equalized
The Big Picture of Respiration Deep, Forced Pulmonary Ventilation