Anatomy of the Pharynx and Larynx Quiz

Human Anatomy and Physiology: The Respiratory System

• Respiration is the exchange of gases between the atmosphere, blood, and cells.
• Four processes are involved: ventilation (breathing), external (pulmonary) respiration, transport of respiratory gases, and internal (tissue) respiration.
• The cardiovascular system helps transport gases as part of the respiratory system.

Learning Outcomes

• Describe the structure and function of each component of the respiratory system.
• List competing pressures involved in respiration, and describe how these gradients are created.
• Describe the mechanics of breathing and its relation to pressure changes.
• Explain how respiration can be assessed (Lung Volumes and Capacities) and the impact of disease upon respiratory function.
• Detail the transport of O₂ and CO₂ in the blood.
• Explain the neuronal mechanisms for controlling breathing, and the factors modulating these processes.

Components of the Respiratory System

• Structurally, the system is divided into upper and lower respiratory systems.
• Functionally, the system is divided into conducting and respiratory zones.

Structures of the Respiratory System

• Upper respiratory system comprises the nose, pharynx, larynx, and associated structures.
• Lower respiratory system includes the trachea, bronchi, and lungs.

The Respiratory System – Functional Zones

• Conducting zone: includes structures for air passage, no gas exchange (nose, nasal cavity, pharynx, larynx, trachea, bronchi, terminal bronchioles).
• Respiratory zone: site of gas exchange (respiratory bronchioles, alveolar ducts, alveoli). Thin-walled structures facilitate gas diffusion.

Anatomy of the Nose and Nasal Cavity

• The nose is the primary air passageway.
• Nostrils contain hair to filter large particles.
• Nasal cavity is the hollow space behind the nose, with two nasal cavities separated by the nasal septum.
• Paranasal sinuses are air-filled cavities, located within the skull, that lighten the skull and enhance voice resonance (maxillary, ethmoidal, frontal, sphenoidal sinuses).

Pharynx

• The pharynx is the throat, a common passageway for food and air, and houses the tonsils.
• Divided into three regions: nasopharynx (posterior to nasal cavity), oropharynx (posterior to oral cavity), and laryngopharynx (posterior to larynx).
• The nasopharynx is a passageway only for air.

Nasopharynx

• Continuous with the nasal cavity, it contains the pharyngeal tonsils and openings of the auditory tubes.
• It closes during swallowing to prevent food from entering the nasal cavity.

Oropharynx and Laryngopharynx

• Oropharynx: stratified squamous epithelium, extends from soft palate to epiglottis. Serves as a common pathway for food and air.
• Laryngopharynx: stratified squamous epithelium, extends from oropharynx, continues as esophagus.

Larynx

• The larynx (voice box) connects the pharynx and trachea.
• Made of muscles and cartilages (thyroid cartilage, cricoid cartilage, arytenoid cartilages, epiglottis, and cuneiform cartilages).
• Contains vocal folds for sound production. The vocal ligaments attach the arytenoid cartilage to the thyroid cartilage. Mucosal folds (true vocal cords) vibrate to produce sound; false vocal cords don't play a role in sound production. Glottis is the medial opening between true vocal cords.
• Functions: sound production, protecting lower respiratory tract (epiglottis during swallowing), passageway for air.

Trachea

• Trachea (windpipe): flexible tube connecting larynx to primary bronchi.
• Composed of three layers: mucosa (goblet cells and ciliated epithelium), submucosa (connective tissue and seromucous glands), adventitia (C-shaped cartilage rings).

Conducting Zone: Bronchi and Subdivisions (bronchial tree)

• Trachea branches into the right and left primary bronchi within the superior border of the fifth thoracic vertebra.
• Bronchi subdivide into smaller and smaller branches within lungs.
• Cartilage support decreases, smooth muscle increases as tubes get smaller.
• Epithelial cell types change as the tubes branch.
• Terminal bronchioles are the end of the conducting zone.
• Cuboidal epithelium, smooth muscle, lack cartilage.

Conducting and Respiratory Zones

• The conduction zone facilitates airflow to the respiratory zone.
• The respiratory zone is where gas exchange occurs.

Respiratory Zone: Bronchi and Subdivisions

• Respiratory bronchioles lead to alveolar ducts, then alveolar sacs and alveoli, approximately 300 million alveoli per lung make up gas exchange surface area.

Alveolar Cells

• Type I cells form the alveolar walls (simple squamous epithelium) and facilitate gas exchange through diffusion.
• Type II cells secrete surfactant, a mixture of lipids, and proteins to reduce surface tension and prevent alveoli from collapsing.

Respiratory Membrane

• The air-blood barrier consists of alveolar cells, alveolar basement membrane, capillary basement membrane, and capillary endothelium.

Lungs

• Occupy the thoracic cavity except the mediastinum.
• Encased and protected by the pleural membrane.
• The root (hilum) is the site of vascular and bronchial attachments.
• Costal surface contacts the ribs.

Lobes and Fissures of the Lungs

• Each lung (left and right) is divided into lobes separated by fissures.

Blood Supply to the Lungs

• Bronchial arteries supply oxygenated blood to all lung tissue except alveoli.
• Alveoli receive deoxygenated blood from the pulmonary arteries.
• Pulmonary veins return oxygenated blood from the lungs to the heart.

Pulmonary Ventilation (Breathing)

• Air flows between the atmosphere and alveoli due to pressure differences created by the contraction and relaxation of respiratory muscles.
• Boyle's Law: The volume of a gas is inversely proportional to its pressure.

Pressure Changes in Pulmonary Ventilation

• Negative respiratory pressure is less than atmospheric pressure; inhalation requires negative pressure to draw air into lungs.
• Positive respiratory pressure is greater than atmospheric pressure.
• Intrapulmonary pressure (Palv): pressure within the alveoli
• Intra-pleural pressure (Pip): pressure within the pleural cavity

Pneumothorax

• Presence of air or gas in the pleural cavity.
• Leads to lung collapse (atelectasis).

Inhalation/Inspiration

• Air movement into the lungs.
• Diaphragm contracts, rib cage expands, lung volume increases, and pressure decreases.

Exhalation/Expiration

• Air movement out of the lungs.
• Diaphragm relaxes, rib cage moves down and inward, lung volume decreases, and pressure increases.

Lung Volumes and Capacities

• Measurements of lung air volumes and capacities, including tidal volume (TV), inspiratory reserve volume (IRV), expiratory reserve volume (ERV), and residual volume (RV); various capacities using combinations of lung volumes
• VC (Vital Capacity), TLC (Total Lung Capacity), IC (Inspiratory Capacity), and FRC (Functional Residual Capacity)

COPD (Emphysema and Chronic Bronchitis)

• Irreversible decrease in the ability to force air out of the lungs.
• Common factors: tobacco smoke and air pollution.
• Emphysema: permanent enlargement of alveoli.
• Chronic Bronchitis: airways inflamed with excessive mucus production.
• Symptoms: dyspnea, coughing, frequent infections, hypoventilation.

Asthma

• Reversible obstructive airway disease.
• Characterized by inflammation, bronchospasm (narrowing of airways), and mucus production.
• Allergic factors are often a critical feature.
• Treatment: bronchodilators and inhaled steroids.

External and Internal Respiration

• External respiration: O₂ diffuses from alveoli into pulmonary capillaries; CO₂ diffuses in the opposite direction.
• Internal respiration: O₂ diffuses from systemic capillaries into tissues; CO₂ diffuses in the opposite direction.

Transport of Oxygen and Carbon Dioxide

• Oxygen: dissolved in plasma and carried by hemoglobin approximately 98.5%.
• Carbon dioxide: dissolved in plasma (10%), bound to hemoglobin (20%), and transported as bicarbonate ions (approximate 70%).

Factors Affecting the Affinity of Hb for O₂

• PO₂, pH, temperature, BPG, and Hb type impact how readily hemoglobin binds and releases oxygen.

Summary of Chemical Reactions During Gas Exchange

• Chemical reactions involving O₂ and CO₂ during gas exchange in both pulmonary and systemic capillaries.

Control of Breathing - Respiratory Centers

• Medullary Respiratory Center: dorsal respiratory group (DRG) mainly responsible for inspiration, ventral respiratory group (VRG) for inspiration and expiration. The pre-Botzinger complex initiates rhythmic breathing.
• Pontine Respiratory Group (PRG): modifying medullary neurons for smoothing out transitions between inspiration and expiration.

Regulation of the Respiratory Center

• Cortical influences allow conscious control of breathing needed to avoid noxious gases or water.
• Chemoreceptors monitor O₂ and CO₂ levels.
• Proprioceptors influence breathing rate changes during movement.
• Inflation reflex limits lung expansion.
• Other factors like limbic system stimulation, pain, blood pressure, and temperature can also influence breathing.