Upper Respiratory System

Respiratory System

• The respiratory system consists of two parts: the upper respiratory system and the lower respiratory system.

Upper Respiratory System

• The upper respiratory system consists of two parts: the nose and nasal cavity, and the pharynx.
• Functions of the upper respiratory system:
  • Passageway for respiration
  • Receptors for smell
  • Filters incoming air to filter larger foreign material
  • Moistens and warms incoming air
  • Resonating chambers for voice

Nose

• The nose provides entrance for air and is divided into two portions: external nares (choanae) and internal nares.
• The external nose is supported by bone and cartilage, covered with skin, and lined with mucus membrane.
• The internal nose is a large cavity in the skull, merging with the external nose anteriorly and communicating with the throat posteriorly.

Nasal Cavity

• The nasal cavity is the entrance of the respiratory system.
• The nasal cavity is divided medially by the nasal septum and contains cilia and sticky mucus membrane to filter particles.
• The nasal cavity is divided into three parts: nasal vestibule, superior part surrounded by bone, and vertical partition (nasal septum).

Trachea

• The trachea is a long tube connecting the mouth and nasal cavity to the rest of the respiratory system.
• The trachea branches off into two bronchi, one for each lung.

Bronchi

• The bronchi divide into smaller tubes called bronchioles.
• Each bronchus enters each lung.

Bronchioles

• The bronchioles are smaller tubes that the air passes through.
• There are millions of bronchioles in the lungs.

Alveoli

• Alveoli are located at the end of each bronchiole.
• Alveoli are air sacs that facilitate gas exchange.
• Features of alveoli:
  • Thin walls to reduce the distance for diffusion
  • Walls are only one cell thick
  • Large surface area for gas exchange
  • Moist surface to facilitate gas exchange
  • Surrounded by capillaries for a rich blood supply

Respiratory Cycle

• The respiratory cycle consists of four processes:
  • Breathing (ventilation): air in and out of the lungs
  • External respiration: gas exchange between air and blood
  • Internal respiration: gas exchange between blood and tissues
  • Cellular respiration: oxygen use to produce ATP, carbon dioxide as waste

Respiratory Center

• The respiratory center is located in the medulla oblongata.
• The respiratory center establishes the basic breathing pattern.
• Chemical receptors monitor carbon dioxide, hydrogen ions, and oxygen levels.

Inspiration and Expiration

• Inspiration: diaphragm contracts, intercostal muscles contract, chest wall expands, and air is pulled into the lungs.
• Expiration: diaphragm and intercostal muscles relax, chest wall descends, and air is expelled from the lungs.

Pharynx

• The pharynx is a funnel-shaped tube that connects the nasal cavity to the larynx.
• The pharynx is lined with mucus membrane and has three regions: nasopharynx, oropharynx, and laryngopharynx.

Larynx

• The larynx is the voice box that conducts air into the lower respiratory tract and produces voice.
• The larynx has three unpaired cartilages: thyroid, cricoid, and epiglottis, and three paired cartilages: arytenoid, cuneiform, and corniculate.

Lungs

• The lungs are located in the thoracic cavity and occupy most of the space.
• The left lung is divided into two lobes by an oblique fissure and is smaller than the right lung.
• The right lung is divided into three lobes by an oblique and horizontal fissure.
• Blood supply in the lungs:
  • Pulmonary circulation supplies deoxygenated blood pumped from the right ventricle and is carried by pulmonary arteries.
  • When blood passes through capillaries of alveoli, it becomes oxygenated.

Chronic Airway Inflammation

• Chronic airway inflammation is a chronic inflammatory disease of the airways.
• Characteristics:
  • Recurrent episodes of wheezing, breathlessness, chest tightness, and coughing, particularly at night or in the early morning.
  • Widespread but variable airflow obstruction that is often reversible either spontaneously or with treatment.
• Pathophysiology:
  • Increased smooth muscle cell proliferation and hypertrophy leading to thickening of the airway wall.
  • Increased mucus production.
  • Airway edema.
  • Presence of inflammatory mediators may increase airway reactivity and induce bronchospasm.

Bronchoconstriction and Bronchodilation

• Bronchoconstriction:
  • Cholinergic (vagal) innervation.
  • Adenosine A1 receptors.
  • α-Adrenergic pathways.
  • Irritant receptors.
• Bronchodilation:
  • β-Adrenergic (β2) receptors.
  • Adenosine A2 receptors.

Symptoms of Chronic Airway Inflammation

• Wheezing due to airstream turbulence and vibration of mucus.
• Rapid breathing and shortness of breath (dyspnea).
• Coughing.
• Chest tightness.
• Hyperinflation of the thorax.

Extrinsic Factors

• Sensitization to allergens is a key feature.

• Decreased childhood infections inhibit normal development of the immune system, leading to increases in allergic responses.

• Increased indoor play and exposure to indoor allergens may contribute to chronic airway inflammation.### Asthma Overview

• Asthma usually begins in childhood, but can also occur in adults, although it is less common.

• It is often associated with atopy, a predisposition to developing allergies.

Types of Asthma

• Intrinsic Asthma: More common in adults, not associated with atopy, and may be triggered by infection, exercise, inhaling cold air, or emotional factors.
• Intrinsic Asthma: Patients may have nasal polyps, aspirin sensitivity, and sinusitis.

Asthma Triggers

• Allergens: pollen, house dust mites, pet dander, cockroach antigens, and cigarette smoke.
• Other Triggers: perfume and other chemicals, viral infections, cold air, exercise, and aspirin.

Diagnosis of Asthma

• Spirometry: Helps determine airflow obstruction and reversibility, valuable in children over 4 years old, but some children may not be able to conduct the maneuver until after 7 years old.
• Spirometry Measurements: FEV1, FVC, and FEV1/FVC are taken before and after the patient inhales a short-acting bronchodilator.

Symptoms of Asthma

• Nocturnal Symptoms: Symptoms occur or worsen at night, awakening the patient.
• Key Indicators: Symptoms occur or worsen in the presence of exercise, viral infection, animals, house-dust mites, mold, pollen, smoke, changes in weather, and strong emotional expression.

Goals of Asthma Management

• Prevent chronic symptoms: Maintain normal/near normal pulmonary function, normal activity level, and prevent recurrent exacerbations.
• Minimize hospital admissions: Meet patients' expectations of and satisfaction with care.

Asthma Medications

• Quick Relievers: Short-acting beta 2 agonist inhalers.
• Long-term Controllers: Inhaled corticosteroids, long-acting beta 2 agonist inhalers, oral beta 2 agonists, Theophylline, cromolyn/nedcromil, and leukotriene modifiers.