Chapter 15: Respiratory System BIOLOGY 12 Chapter 15: Respiratory System

Overview/Objectives 15.1 The Respiratory System Two steps required for ventilation Three steps that involve the circulatory system How respiratory surfaces modify air Path of air/ and functions of each organ 15.2 Mechanism of Breathing Measurements of air in and out of our lungs How breathing is achieved (pressure in lungs) 15.3 Gas Exchange in the body Gas exchange: external vs internal respiration Function of respiratory pigments in red blood cells 15.4 Respiration and Health Common respiratory infections and disorders

15.1 The Respiratory System Function: Gas exchange to support cellular respiration. Two steps of ventilation (breathing): Inspiration (inhalation) – fresh oxygen rich air brought to lungs Expiration (exhalation)- stale, carbon dioxide rich air brought away from lungs

Types of Respiration Notice that the respiratory system works with the cardiovascular system (types 2-4) 1. Breathing: mechanical movement of air in and out of lungs. No diffusion of gases across any membranes

2. External Respiration: exchange of gases between the lungs and the blood stream * O2 in and * CO2 out.

3. Internal Respiration: exchange of gases between the tissue capillaries and the cells of the body *O2 from blood to cells and *CO2 returned to the blood from cells.

4. Cellular Respiration: biochemical reactions (metabolism) in the cells in which glucose is oxidized and converted into ATP energy with CO2 as a by product .

Cellular Respiration Reaction

Anatomy

Path of Air & Functions a) Upper Respiratory Tract 1) Nasal cavity Structure: Nostrils= opening to cavity Two nasal cavities= Lined with mucous membrane Function: Main function is to filter, warm and moisten air as it enters the respiratory tract

2) Pharynx Epiglottis Glottis Structure: connects nasal and oral cavity to larynx Function: Connection to surrounding regions Epiglottis flap of skin covering the glottis prevents food from going down the windpipe Glottis opening to the trachea allows air to pass between the pharynx and larynx

3) Larynx Structure: Cartilaginous; houses the vocal cords (voice box) Function: Sound protection

b) Lower Respiratory Tract 4) Trachea Structure: Flexible tube, connects Larynx with bronchi Function: Passage of air to bronchi

5) Bronchi Structure: Paired tubes below the trachea that enter the lungs Function: Passage of air to the lungs

6) Bronchioles Structure: Branched tubes that lead from bronchi to alveoli Function: Passage of air to each alveolus

7) Lungs Structure: Soft, cone-shaped organs that occupy thoracic cavity Enclosed by double layer membrane = pleura Function: Contains alveoli and blood vessels

8) Alveoli Structure: Thin-walled microscopic air sacs in lungs Function: Gas exchange between air and blood

The structure of alveoli allow it to perform its function: Large SA/V ratio  efficient exchange of gasses Thin & Elastic walls  increase diffusion rate (gasses are close to blood) Moist surface  gasses diffuse efficiently through a liquid environment (to a limit) Surfactant (lipoprotein layer)  lowers surface tension so alveoli do not collapse Highly Vascularized  each alveolus is surrounded by extensive blood supply

Blood Supply to and from Alveoli pulmonary arteries carry deoxygenated blood back to lungs from the right ventricle pulmonary venules carry oxygen rich blood back to the heart from the lungs

15.2 Mechanisms of Breathing

Respiratory Volumes Spirometer- used by physicians to measure breathing Tidal volume- the amount of air normally moved in/out (~500mL) Vital capacity- the maximum amount of air that can be moved in + out Inspiratory reserve volume- volume of air that can be forcibly inhaled after normal inhalation Expiratory reserve volume- volume of air that can be forcibly exhaled after normal exhalation Residual volume- amount of air remaining in lungs after a forceful exhalation

Important Facts to Know about Ventilation Normally, there is a continuous column of air from the pharynx to the alveoli Lungs lie in the thoracic cavity; rib cage = top/sides of thoracic cavity diaphragm= flood of thoracic cavity Pleura= surrounds the lungs Functions: allows lungs to move freely in thoracic cavity reduces friction between lungs and ribs seals thoracic cavity; creating a vaccum

Inspiration The medula oblongata detects CO2, O2, (H+) levels and sends signals to the diaphragm and rib muscles by the phrenic nerve Diaphragm goes down (contracts) and ribs come up and out This enlarges thoracic chest cavity creating negative pressure compared to atmospheric pressure  air rushes in Stretch receptors in alveoli are stimulated  message sent by vagus nerve to brain for expiration

Inspiration

Expiration The diaphragm relaxes and the rib cage moves down & in Lungs recoil Positive pressure in lungs Air forced out Talking occurs as air moves over vocal cords in larynx

Expiration

Mechanics of Breathing Medulla senses decrease in pH and increase in CO2 and sends a message to the diaphragm and intercostal muscles via the phrenic nerve causing inhalation When the lungs are stretched receptors send a message via the vagus nerve back to brain and exhalation occurs

Control of Breathing Rate Our breathing rate must be able to respond to various energy demands of the body. The medulla in our brain contains our breathing center - it sets the basic rate.

Control of Breathing By Carbon Dioxide CO2 levels rise in blood Medulla oblongata detects this Nerve impulses sent to diaphragm and rib muscles Breathing rate increases to get rid of CO2

Control of Breathing Continued B) By Oxygen Low oxygen levels measured by chemoreceptors in aorta and carotid arteries Message sent to medulla oblongata Nerve impulses sent to the diaphragm and rib muscles to increase breathing rate to obtain oxygen

Of the two mechanisms, the control of breathing by carbon dioxide is the most important

15.3 Gas Exchange

1. External Respiration External respiration = exchange of gasses between air (alveoli) and blood (pulmonary capillaries) Partial pressure= pressure exerted by a gas (PCO2 and PO2)

EXTERNAL RESPIRATION

External Respiration CO2 Blood in pulmonary capillaries has higher PCO2 than atmospheric air CO2 diffuses out of plasma and into lungs Most CO2 is carried as bicarbonate ions (HCO3-) Enzyme carbonic anhydrase in red blood cells speeds breakdown of carbonic acid (H2CO3) carbonic anhydrase H+ + HCO3-  H2CO3  H2O + CO2 Hydrogen Bicarbonate carbonic water carbon Ion ion acid dioxide

External Respiration  O2 Reverse pattern of that for CO2 Blood in pulmonary capillaries is low in O2 and alveolar air has higher PO2  O2 diffuses into plasma and into red blood cells in the lungs Hemoglobin takes up oxygen and becomes oxyhemoglobin (HbO2) Hb + O2  HbO2 Deoxyhemoglobin oxygen oxyhemoglobin

2. Internal Respiration Internal Respiration= the exchange of gasses between the blood in the systemic capillaries and the tissue fluid

Internal Respiration  O2 O2 diffuses out of the blood and into the tissues because PO2 of tissue is lower than that of blood PO2 of tissue is lower because cells are continuously using O2 in cellular respiration HbO2  Hb + O2 oxyhemoglobin Deoxyhemoglobin oxygen

Internal Respiration  CO2 Carbon dioxide diffuses into the blood from the tissues because PCO2 of tissue fluid is higher than that of blood PCO2 of tissue fluid is higher because cells continuously produce CO2 CO2 enters red blood cells three ways: dissolved in plasma (small amount) transported as bicarbonate ion (most) attached to hemoglobin (some) carbaminohemoglobin carbonic anhydrase H2O + CO2  H2CO3  H+ + HCO3- water carbon carbonic Hydrogen Bicarbonate dioxide acid ion ion

15.4 Respiration and Health The respiratory tract is constantly exposed to environmental air, which means air quality affects our health

Upper Respiratory Tract Infections Sinusitis- infection of the cranial sinuses Otitis Media- bacterial infection of middle ear (caused by nasal infection Tonsillitis- tonsils in the pharynx become inflamed and enlarged Laryngitis- infection of the larynx (hoarseness of voice)

Lower Respiratory Tract Infections Acute bronchitis- infection of primary and secondary bronchi Pneumonia- viral or bacterial infection of the lungs (bronchi and alveoli fill with thick fluid) Pulmonary tuberculosis- tuburcle bacillus (bacteria) invade lung tissue Pulmonary fibrosis (restrictive pulmonary disorder)- connective tissue build up in lungs Chronic bronchitis- airways inflamed and filled with mucous Emphysema- chronic, incurable disorder, alveoli damaged, less SA for gas exchange Asthma- disease of bronchi and bronchioles

Lung Cancer