RESPIRTORY SYSTEM

RESPIRTORY SYSTEM CLASS: I M.Sc., UNIT: 3 PREPARED BY: A. BENNO SUSAI DEPARTMENT OF BIOCHEMISTRY, SJC, TRICHY

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. DEPARTMENT OF BIOCHEMISTRY, SJC, TRICHY

Blood Transports Gases Between Lungs and Tissues DEPARTMENT OF BIOCHEMISTRY, SJC, TRICHY

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. DEPARTMENT OF BIOCHEMISTRY, SJC, TRICHY

DEPARTMENT OF BIOCHEMISTRY, SJC, TRICHY

Human Respiratory System Nasal cavity: Air enters nostrils, is filtered by hairs, warmed, humidified, and sampled for odors as it flows through a maze of spaces. Pharynx (Throat): Intersection where pathway for air and food cross. Most of the time, the pathway for air is open, except when we swallow. 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). DEPARTMENT OF BIOCHEMISTRY, SJC, TRICHY

Human Respiratory System Trachea (Windpipe): Rings of cartilage maintain shape of trachea, to prevent it from closing. Forks into two bronchi. Bronchi (Sing. Bronchus): Each bronchus leads into a lung and branches into smaller and smaller bronchioles, resembling an inverted tree. 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. DEPARTMENT OF BIOCHEMISTRY, SJC, TRICHY

Pulmonary Function Tests • Assessed by spirometry. • Subject breathes into a closed system in which air is trapped within a bell floating in H20. • The bell moves up when the subject exhales and down when the subject inhales. DEPARTMENT OF BIOCHEMISTRY, SJC, TRICHY

Spirogram • Tidal volume: • Amount of air expired with each breath. • Vital capacity: • The maximum amount of air that can be forcefully exhaled after maximum inhalation. DEPARTMENT OF BIOCHEMISTRY, SJC, TRICHY

Terms Used to Describe Lung Volumes and Capacities Term Definition Lung Volumes The four nonoverlapping components of the total lung capacity Tidal volume The volume of gas inspired or expired in an unforced respiratory cycle Inspiratory reserve volume The maximum volume of gas that can be inspired during forced breathing in addition to tidal volume Expiratory reserve volume The maximum volume of gas that can be expired during forced breathing in addition to tidal volume Residual volume The volume of gas remaining in the lungs after a maximum expiration Lung CapacitiesMeasurements that are the sum of two or more lung volumes Total lung capacity The total amount of gas in the lungs after a maximum inspiration Vital capacity The maximum amount of gas that can be expired after a maximum inspiration Inspiratory capacity The maximum amount of gas that can be inspired after a normal tidal expiration Functional residual capacity The amount of gas remaining in the lungs after a normal tidal expiration DEPARTMENT OF BIOCHEMISTRY, SJC, TRICHY

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. DEPARTMENT OF BIOCHEMISTRY, SJC, TRICHY

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. DEPARTMENT OF BIOCHEMISTRY, SJC, TRICHY

Hemoglobin Loading and Unloading of Oxygen DEPARTMENT OF BIOCHEMISTRY, SJC, TRICHY

Respiratory Acid-Base Balance • Ventilation normally adjusted to keep pace with metabolic rate. • H2CO3 produced converted to CO2, and excreted by the lungs. • H20 + C02 H2C03 H+ + HC03- DEPARTMENT OF BIOCHEMISTRY, SJC, TRICHY

Respiratory Acidosis • Hypoventilation. • Accumulation of CO2 in the tissues. • pH decreases. • Plasma HCO3- increases. • Pc02 increases. DEPARTMENT OF BIOCHEMISTRY, SJC, TRICHY

Respiratory Alkalosis • Hyperventilation. • Excessive loss of CO2. • pH increases. • Plasma HCO3- decreases. • Pc02 decreases. DEPARTMENT OF BIOCHEMISTRY, SJC, TRICHY

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. DEPARTMENT OF BIOCHEMISTRY, SJC, TRICHY

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. DEPARTMENT OF BIOCHEMISTRY, SJC, TRICHY

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. DEPARTMENT OF BIOCHEMISTRY, SJC, TRICHY

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. DEPARTMENT OF BIOCHEMISTRY, SJC, TRICHY

REFERENCES • Arthur C. Guyton, 2005, Text Book of Medical Physiology, WB Saunders’s, USA. • C. C Chatterjee, 1985, Human Physiology Vol I & Vol II. 11thEdn, Kalyani Mukerjee Publications, Kolkata, India. • Kathleen, J.W. Wilson and Anne Waugh. 1998. Ross and Wilson Anatomy and Physiology in health and illness. (8th Edition). Churchchill Livingstone, New York. DEPARTMENT OF BIOCHEMISTRY, SJC, TRICHY

RESPIRTORY SYSTEM