RESPIRATION: THE EXCHANGE OF GASES Chapter 22 RESPIRATION: THE EXCHANGE OF GASES

Human Respiratory System Functions: Works closely with circulatory system, exchanging gases between air and blood: Takes up oxygen from air and supplies it to blood (for cellular respiration). Removal and disposal of carbon dioxide from blood (waste product from cellular respiration). Homeostatic Role: Regulates blood pH. Regulates blood oxygen and carbon dioxide levels.

Blood Transports Gases Between Lungs and Tissues

Human Respiratory System Components: Nasal cavity, throat (pharynx), larynx (voice box), trachea, bronchi, alveoli, and lungs. Pathway of Inhaled Air: Nasal cavity Pharynx (Throat) Larynx (Voice Box) Trachea (Windpipe) Bronchi Bronchioles Alveoli (Site of gas exchange) Exhaled air follows reverse pathway.

Human Respiratory System

Human Respiratory System 1. Nasal cavity: Air enters nostrils, is filtered by hairs, warmed, humidified, and sampled for odors as it flows through a maze of spaces. 2. Pharynx (Throat): Intersection where pathway for air and food cross. Most of the time, the pathway for air is open, except when we swallow. 3. Larynx (Voice Box): Reinforced with cartilage. Contains vocal cords, which allow us to make sounds by voluntarily tensing muscles. High pitched sounds: Vocal cords are tense, vibrate fast. Low pitched sounds: Vocal cords are relaxed, vibrate slowly. More prominent in males (Adam’s apple).

Larynx or Voicebox Contains the Vocal Cords

Human Respiratory System 4. Trachea (Windpipe): Rings of cartilage maintain shape of trachea, to prevent it from closing. Forks into two bronchi. 5. Bronchi (Sing. Bronchus): Each bronchus leads into a lung and branches into smaller and smaller bronchioles, resembling an inverted tree. 6. Bronchioles: Fine tubes that allow passage of air. Muscle layer constricts bronchioles. Epithelium of bronchioles is covered with cilia and mucus. Mucus traps dust and other particles. Ciliary Escalator: Cilia beat upwards and remove trapped particles from lower respiratory airways. Rate about 1 to 3 cm per hour.

Human Respiratory System Alveoli (Sing. Alveolus): Grapelike clusters of tiny air sacs with very thin elastic walls through which gas exchange occurs. Oxygen in air enters blood in capillaries. Carbon dioxide in blood enters air in alveoli. There are several million alveoli in the human lungs, with a total surface roughly equivalent to a tennis court. The walls of the alveoli are very delicate. Alveolar macrophages are phagocytic cells that swallow inhaled particles (dust, bacteria, etc.) and digest them.

Structure of Lung Alveoli

Lung Alveoli Are The Site of Gas Exchange

Exchange of Gases Occurs in Alveoli

Breathing Ventilates the Lungs Breathing: Alternation of inhalation and exhalation. Supplies our lungs with oxygen rich air, and expels excess carbon dioxide. Inhalation: Diaphragm contracts, moving downward and causing rib cage, chest cavity, and lungs to expand. Air rushes in, due to decrease in internal lung pressure as lungs expand. Exhalation: Diaphragm relaxes, moving upwards and causing rib cage, chest cavity, and lungs to contract. Air rushes out, due to the increase in internal lung pressure as lungs contract. Breathing is controlled by centers in the nervous system to keep up with body’s demands.

Human Breathing: Inhalation and Exhalation

Human Breathing is Automatically Controlled

Hemoglobin helps transport CO2 and buffer blood Hemoglobin is found in red blood cells Functions: Transports oxygen Transport carbon dioxide Helps buffer blood As carbon dioxide is picked up from tissues it is converted into carbonic acid: CO2 + H2O <-----> H2CO3 <----> H+ + HCO3 - Carbon Carbonic acid Carbonate ion dioxide Hemoglobin picks up most H + ions, so they don’t acidify the blood.

Blood Transports Gases to Between Lungs and Tissues

Hemoglobin Loading and Unloading of Oxygen

Hemoglobin Transports Gases and Helps Buffer Blood

Diseases of the Respiratory System Respiratory rate: 10 to 14 inhalations/minute. In one day, an average human: Breathes 20,000 times Inhales 35 pounds of air Most of us breathe in air that is heavily contaminated with solid particles, ozone, sulfur oxide, carbon monoxide, nitrogen oxides, and many other damaging chemicals. Breathing contaminated air can cause a number of diseases including asthma, bronchitis, emphysema, and lung cancer.

Diseases of the Respiratory System Cigarette smoke is one of the worse air pollutants. Over 1 million people start smoking every year. Kills about 350,000 people every year in U.S. Contains 4000 different chemicals. Each cigarette smoked subtracts about 5 minutes from life expectancy. Cigarette smoke paralyzes cilia in airways, preventing them from removing debris and from protecting delicate alveoli. Frequent coughing is the only way airways can clean themselves. Cigarette smoke also causes fetal damage, which can result in miscarriage, premature birth, low birth weight, and poor development.

Diseases of the Respiratory System Asthma: Condition in which breathing is impaired by constriction of bronchi and bronchioles, cough, and thick mucus secretions. The severity and incidence of asthma has risen dramatically in recent years, especially in children. May be fatal if not treated. Causes: Attacks may be precipitated by inhalation of allergens (e.g.: pollen, cats, and cockroach proteins), pollutants, infection, or emotional stress. Treatment: Alleviates symptoms (e.g.: immuno-suppressors, bronchodilators), but is not a cure.

Diseases of the Respiratory System Bronchitis: Inflammation of the mucous membranes of the bronchi. May present with cough, fever, chest or back pain, and fatigue. Causes: Associated with smoking, pollution, and bacterial or viral infections. Pneumonia: Acute inflammation of the lungs. Symptoms include high fever, chills, headache, cough, and chest pain. Causes: Bacterial, fungal, or viral infections. Treatment: Antibiotics or other antimicrobials.

Diseases of the Respiratory System Emphysema: Permanent and irreversible destruction of alveolar walls, resulting in loss of lung elasticity and gas exchange surface. Symptoms include shortness of breath, difficulty exhaling, cough, weakness, anxiety, confusion, heart failure, lung edema (swelling), and respiratory failure. Causes: Smoking, pollution, old age, and infections. Treatment: Oxygen to help breathing. No cure.

Diseases of the Respiratory System Lung Cancer: Cancerous growth that invades and destroys lung tissue. Very high fatality rate. Symptoms include bloody sputum, persistent cough, difficulty breathing, chest pain, and repeated attacks of bronchitis or pneumonia. Causes: Smoking (50% of all cases) and pollution (radon, asbestos). Smokers are 10 times more likely to develop lung cancer than nonsmokers. Treatment: Surgery is most effective, but only 50% of all lung cancers are operable by time of detection. Other treatments include radiation and chemotherapy.

Human Fetus Exchanges Gases with Mother’s Blood through the Placenta