Chapter 9 Respiratory System

Points to Ponder What are the parts and function of the upper and lower respiratory system? What is the mechanism for expiration and inspiration? How is breathing controlled by the nervous system and through chemicals? Where and how is exchange of gases accomplished? What are some common respiratory infections and disorders? What do you know about tobacco and health? What is your opinion about bans and legislation on smoking?

Organs of the Respiratory System

The Respiratory System Ensures oxygen enters and carbon dioxide leaves body. Inspiration: Inhalation Expiration: Exhaling

What is the pathway that air follows? nose pharynx larynx trachea bronchus bronchioles alveoli

Upper Respiratory Tract Nose Pharynx Larynx

The Nose Opens at the nostrils/nares; leads to the nasal cavities. Nasal cavities divided by a bone/cartilage septum. Hairs and mucus filters air entering the cavities. The nasal cavity has capillaries to warm and moisten the air. Specialized ciliated cells in the narrow upper recesses of the nasal cavity act as odor receptors. Tear glands (lacrimal glands) drain into the nasal cavities.

The Pharynx Funnel-shaped cavity connecting nasal and oral cavities to the larynx. Commonly called the “throat”. 3 portions based on location: Nasopharynx: Where nasal cavities open above the soft palate. Oropharynx: Where oral cavity opens. Laryngopharynx: Open into the larynx. Tonsils provide a lymphatic defense during breathing at the junction of the oral cavity and pharynx.

The Larynx Triangular, cartilaginous structure that passes air between the pharynx and trachea. Ie. Voice box (houses vocal cords) At apex of triangle sits Adam’s apple. 2 mucosal folds make up the vocal cords. Glottis: Opening between the slit of the vocal cords. High or low pitch of voice is controlled by the tension of the vocal chords. Moves against the epiglottis when swallowing.

Lower Respiratory Tract Trachea Bronchial tree Lungs

The Trachea, ie. Windpipe Tube connecting the larynx with the primary bronchi. Anterior to the esophagus. Made of connective tissue, smooth muscle and cartilaginous rings. Lined with cilia (pseudostratified ciliated columnar epithelium) and goblet cells to produce mucus. Helps keep the lungs clean.

The Bronchial Tree Begins with the division of trachea into left and right primary bronchi. Lead to left and right lungs. Bronchi continue to branch, eventually transitioning into small bronchioles about 1mm in diameter with thinner walls. Bronchioles eventually lead to alveoli (elongated air sacs for gas exchange),

The Lungs Paired, cone-shaped organs in the thoracic cavity. Consist of the bronchi, bronchioles and alveoli. Right lung has 3 lobes; left lung has 2 lobes. Lobes divide into lobules with bronchioles and alveoli. Each lung is enclosed by pleura membranes. Produce serous fluid for lubrication.

The Alveoli ~ 300 million in the lungs; greatly increase surface area. Alveoli are enveloped by blood capillaries. Alveoli and capillaries consists of one layer of epithelium; allows for gas exchange. Lined with surfactant; act as a film to keep alveoli open.

Phases of Breathing/Ventilation 1. Inspiration: an active process of inhalation that brings air into the lungs 2. Expiration: usually a passive process of exhalation that expels air from the lungs

Inspiration The diaphragm and intercostal muscles contract The diaphragm flattens and the rib cage moves upward and outward Volume of the thoracic cavity and lungs increase The air pressure within the lungs decrease Air flows in to the lungs

Expiration The diaphragm and intercostal muscles relax The diaphragm moves upward and becomes dome-shape The rib cage moves downward and inward Volume of the thoracic cavity and lungs decrease The air pressure within the lungs increases Air flows out of the lungs

Different Volumes of Air During Breathing Tidal volume: the small amount of air that usually moves in and out with each breath Vital capacity: the maximum volume of air that can be moved in plus the maximum amount that can be moved out during one breath Inspiratory and expiratory reserve volume: the increased volume of air moving in or out of the body Residual volume: the air remaining in the lungs after exhalation

Visualizing the Vital capacity

Nervous System Control of Breathing Respiratory control center in the brain (medulla oblongata) sends out nerve impulses to contract muscle for inspiration. Sudden infant death syndrome (SIDS) is thought to occur when this center stops sending out nerve signals

Chemical Control of Breathing 2 sets of chemoreceptors sense the drop in pH: one set is in the brain and the other in the circulatory system Both are sensitive to carbon dioxide levels that change blood pH due to metabolism

Exchange of Gases in the Body Oxygen and carbon dioxide are exchanged The exchange of gases is dependent on diffusion Partial pressure is the amount of pressure each gas exerts (PCO2 or PO2) Oxygen and carbon dioxide will diffuse from the area of higher to the area of lower partial pressure

External Respiration Exchange of gases between the lung alveoli and the blood capillaries PCO2is higher in the lung capillaries than the air thus CO2 diffuses out of the plasma into the lungs The partial pressure pattern for O2 is just the opposite so O2 diffuses the red blood cells in the lungs Carbon dioxide transport: carbonic H+ + HCO3- H2CO3 anhydrase H2O + CO2 Oxygen transport: Hb + O2 HbO2

Internal Respiration The exchange of gases between the blood in the capillaries outside of the lungs and the tissue fluid PO2 is higher in the capillaries than the tissue fluid thus O2 diffuses out of the blood into the tissues Oxyhemoglobin gives up oxygen: HbO2 Hb + O2 Most CO2 is carried as a bicarbonate ion: carbonic CO2 + H2O anhydrase H2CO3 H3 + HCO3-

Movement of Oxygen and Carbon Dioxide in the Body

Upper Respiratory Tract Infections Sinusitis: Blockage of sinuses Otitis media: Infection of the middle ear Tonsillitis: Inflammation of the tonsils Laryngitis: Infection of the larynx that leads to loss of voice

Lower Respiratory Tract Disorders Pneumonia: Infection of the lungs with thick, fluid build up Tuberculosis: Bacterial infection that leads to tubercles (capsules) Pulmonary fibrosis: Lungs lose elasticity because fibrous connective tissue builds up in the lungs usually because of inhaled particles Emphysema: Chronic, incurable disorder in which alveoli are damaged and thus the surface area for gas exchange is reduced Asthma: Bronchial tree becomes irritated causing breathlessness, wheezing and coughing Lung cancer: Uncontrolled cell division in the lungs that is often caused by smoking and can lead to death

Health focus: Things you should know about tobacco and health. All forms of tobacco can cause damage Smoking increases a person’s chance of lung, mouth, larynx, esophagus, bladder, kidney, pancreas, stomach and cervix The 5-year survival rate for people with lung cancer is only 13% Smoking also increases the chance of chronic bronchitis emphysema, heart disease, stillbirths and harm to an unborn child Passive smoke can increase a nonsmokers chance of pneumonia, bronchitis and lung cancer

Bioethical focus: What do you think? Is it ethical to ban smoking? Does restricting the freedom to smoke segregate people based on habit? Are nonsmokers infringing upon smokers or are smokers infringing upon nonsmokers? Is it both? Will this legislation help smokers quit? Should smoking be banned in bars and casinos? Do smoking bans hurt the economy?