Week 5 呼吸系统 The Respiratory System: Function and Anatomy

• The respiratory system takes in oxygen and removes carbon dioxide.
• It warms and moistens inhaled air.
• The system filters particles from inhaled air.
• It gives a sense of smell.
• Sound is produced by moving air past the vocal cords.

Lower Respiratory Tract

• The nose opens at the nostrils/nares and leads into the nasal cavities.
• Hairs and mucus in the nose filter the air.
• The nasal cavity has many capillaries that warm and moisten the air.
• Specialized cells act as odor receptors (olfactory sensory receptors).

Lower Respiratory Tract (cont.)

• Tonsils provide a lymphatic defense during breathing at the junction of the oral cavity and pharynx.
• The larynx is a triangular, cartilaginous structure that passes air between the pharynx and trachea.
• Also known as the voice box, it houses the vocal cords.
• Two mucosal folds make up the vocal cords, with an opening in the middle called the glottis.
• The glottis separates the vocal cords.
• Sound is produced by the vibration of cords during exhalation
• Pitch is controlled by the tension on the cords.

Lower Respiratory Tract

• Made up of the trachea, bronchial tree, and lungs.
• The trachea is a tube, often called the windpipe, which connects the larynx with the bronchi.
• It is composed of connective tissue, smooth muscle, and cartilaginous rings, which keep the airways open.
• The trachea is lined with cilia and mucus that help to keep the lungs clean.
• The bronchial tree starts with two main bronchi that lead from the trachea into the lungs.
• The bronchi continue to branch until they are small bronchioles about 1mm in diameter with thinner walls.
• Bronchioles eventually lead to elongated sacs called alveoli.

The Alveoli

• There are 300 million alveoli in the lungs, which greatly increases the surface area.
• Alveoli are enveloped by blood capillaries.
• They are lined with surfactant that acts as a film to keep alveoli open.

The Lungs

• Bronchi, bronchioles, and alveoli beyond the bronchi make up the lungs.
• The right lung has 3 lobes while the left lung has 2 lobes that divide into lobules.
• Each lung is enclosed by membranes called pleura.

Definitions

• Ventilation Definition: Movement of air into and out of the lungs (breathing).
• Inspiration (inhalation) Definition: breathing in.
• Expiration (exhalation) Definition: breathing out.
• Respiration Definition: Gas exchange.
• Cellular respiration Definition: Use of oxygen by cells to make ATP

Breathing/Ventilation

• Inspiration Definition: An active process of inhalation that brings air into the lungs.
• Expiration Definition: Usually a passive process of exhalation that expels air from the lungs.

Inspiration/Inhalation

• The diaphragm and intercostal muscles contract.
• The diaphragm flattens, and the rib cage moves upward and outward.
• Volume of the thoracic cavity and lungs increases.
• Air pressure within the lungs decreases.
• Air flows into the lungs.

Expiration/Exhalation

• The diaphragm and intercostal muscles relax.
• The diaphragm moves upward and becomes dome-shaped.
• The rib cage moves downward and inward.
• The volume of the thoracic cavity and lungs decreases.
• Air pressure within the lungs increases.
• Air flows out of the lungs.

Volumes of Air During Breathing

• Tidal volume Definition: the small amount of air that usually moves in and out with each breath, approximately 500 mL.
• Vital capacity Definition: the maximum volume of air that can be moved in plus the maximum amount that can be moved out during one breath, approximately 4800 mL.

Regulation of Breathing

• Nervous control Definition: The respiratory control center in the brain (medulla oblongata) sends out nerve impulses to contract muscles for inspiration; controls breathing rate and depth.
• Chemical control Definition: Two sets of chemoreceptors sense changes in blood pH: one set is in the brain and the other in the circulatory system.
• Both chemoreceptors sets are sensitive to carbon dioxide levels that change blood pH due to metabolism.
• Breathing rate speeds up when blood pH drops and becomes too acidic.

Upper Respiratory Tract Infections

• Sinusitis Definition: blockage of sinuses.
• Otitis media Definition: An ear infection.
• Tonsillitis Definition: Inflammation of the tonsils.
• Laryngitis Definition: An infection of the larynx that leads to a loss of voice

Lower Respiratory Disorders

• Pneumonia Definition: An infection of the lungs with a thick, fluid build-up.
• Tuberculosis Definition: A bacterial infection that leads to tubercles (capsules).
• Pulmonary fibrosis Definition: Lungs lose elasticity because fibrous connective tissue builds up in the lungs usually because of inhaled particles

Lower Respiratory Disorders (cont.)

• Cystic Fibrosis Definition: An inherited disease that causes thickened mucus to form in the lungs, pancreas, and other organs, blocking the airways in the lungs to cause damage and labored breathing.
• Asthma Definition: A bronchial tree becomes irritated causing breathlessness, wheezing, and coughing
• Asthma Definition: A disease characterized by intermittent episodes in which airway smooth muscle contracts strongly, markedly increasing airway resistance
• The basic defect in asthma is chronic inflammation of the airways, the causes of which vary from person to person and include, among others, allergy, viral infections, and sensitivity to environmental factors.

Chronic Obstructive Pulmonary Disease (COPD)

• Exemplified by chronic bronchitis and emphysema.
• Major causes of death and disability in North America
• Emphysema Definition: Caused by destruction and collapse of the smaller airways and loss of elastic ability to exhale; barrel chest is common.
• Chronic bronchitis Definition: Characterized by excessive mucus production in the bronchi and chronic inflammatory changes in the small airways where the cause of obstruction is an accumulation of mucus in the airways and thickening of the inflamed airways.

Chronic Obstructive Pulmonary Disease (cont.)

• Features of both emphysema and chronic bronchitis.
• Patients almost always have a history of smoking.
• Labored breathing (dyspnea) becomes progressively more severe.
• Coughing and frequent pulmonary infections are common.
• Most victims are hypoxic, retain carbon dioxide, and have respiratory acidosis.
• These diseases cause severe difficulties not only in ventilation but also in oxygenation of the blood.
• Those infected will ultimately develop respiratory failure.

Lung Cancer

• Accounts for one-third of all cancer deaths in the United States.
• Increased incidence is associated with smoking.
• Two major types: Non-Small cell carcinoma and Small cell carcinoma.

Explore the vital functions of the respiratory system, including oxygen intake, carbon dioxide removal, air filtration, and the sense of smell. Delve into the anatomy of the lower respiratory tract, covering the roles of the nose, nasal cavities, tonsils and larynx and vocal cords in respiration and sound production.