Respiratory System PDF

CHAPTER 10 The Respiratory System* *Optional HW with this chapter  Functions of the respiratory system: Exchanging carbon dioxide and oxygen Producing noises (language) Respiratory system  The path of oxygen: Oxygen inhaled: through mouth or nose, into pharynx, down trachea, into b...

CHAPTER 10 The Respiratory System* *Optional HW with this chapter  Functions of the respiratory system: Exchanging carbon dioxide and oxygen Producing noises (language) Respiratory system  The path of oxygen: Oxygen inhaled: through mouth or nose, into pharynx, down trachea, into bronchi, into bronchioles, into alveoli in lungs  diffuses into blood plasma in capillaries surrounding alveoli  binds with hemoglobin  transported in blood vessels  diffuses into blood plasma in capillaries of body  diffuses into cells  diffuses to mitochondria in cells, for aerobic cellular respiration. (carbon dioxide moves in the opposite direction) Note that gas exchange between the respiratory system and the circulatory system occurs at the alveoli only The upper respiratory tract Figure 10.2 Copyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc. Slide 10.3A  Nasal passages Passageway for respiration Has receptors for smell (is thus important for “taste” too) Foreign material (dirt and bacteria) caught in mucus, cilia moves it back to pharynx (cough out or swallowed) Moistens (mucus) and warms (many blood vessels) air before it enters lungs Resonating chambers for voice (influences voice quality) The lower respiratory tract Copyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc.  Larynx Epiglottis covers trachea and vocal cords cover glottis (opening to trachea) in swallowing reflex, so food does not enter trachea (don’t eat and talk) When not talking = glottis is open. Talking, singing, etc. = glottis is mostly closed. Air passing through the narrow glottis causes the vocal cords to vibrate. Shorter cords / stretched tighter: higher pitched voice Longer cords / looser: lower pitched voice Men have enlarged larynx deeper voices after puberty (due to longer vocal chords). Laryngitis: larynx is inflamed, vocal chords cannot cover opening properly, do not vibrate The larynx Breathing Talking  Trachea Transports air to and from lungs. Ringed with cartilage, so it’s always open Smooth muscle allows adjustment for heavy breathing (wider) / coughing (narrower = more air pressure).  Smoking and infections The trachea is lined with mucus-secreting cells, and cells with cilia. Smoking paralyzes these cilia, and long-term smoking kills them. This leads to “smoker’s cough”. Smoking also kills white blood cells in the respiratory tract, and loss of the cilia and white blood cell death both make smokers more vulnerable to respiratory tract infections.  Bronchi/bronchioles Left and right bronchi are cartilage lined. Cilia and mucus present. Smooth muscle is present. Bronchi branch into small airways known as bronchioles. Smooth muscle present. Cilia and mucus still present. Cartilage not present.  Asthma Some people have asthma attacks: a trigger such as pollen, dust, other allergens, as well as pollution, stress, heavy exercise and respiratory infections can cause an attack. During an attack, smooth muscles in the bronchioles constrict, and mucus is produced in high amounts, both of which dramatically restrict breathing. An attack can be fatal. People who suffer from asthma attacks must carry inhalers with them, that widen the bronchioles allowing them to breath.  Gas exchange occurs at alveoli Each bronchiole ends in several alveoli. Both lungs have about 300 million alveoli combined, with about 75 square meters of surface area for exchange. Alveoli have a single cell layer, with pulmonary capillaries lining it (air must cross 2 cell layers). Gas exchange between capillaries and alveoli  Emphysema Emphysema occurs when alveoli deteriorate, it progresses over many years. As a result of the destroyed alveoli, not as much gas is exchanged in the lungs, and even walking and basic physical activities can be difficult. The reduced gas exchange causes the heart to have to work harder as well, to circulate the reduced amount of oxygen entering the blood. Ultimately, emphysema can be fatal. Cigarette smoking is the leading cause of emphysema, but frequent respiratory infections and genetics can cause it as well. Breathing in and out (inhalation and exhalation) Breathing in: External intercostal muscles and diaphragm contract. This expands the lungs, increasing their volume and decreasing the pressure within them. Air moves from higher pressure (outside the body) into the lungs. Breathing out: The muscles relax, and the ribcage and diaphragm recoil. This lowers the volume of the lungs and increases the pressure, and air is “squeezed” out of the lungs. Active exhalation: abdominal muscles contract, and push diaphragm upwards more, also internal intercostal muscles contract, pulling ribs inwards.  Lungs Enclose bronchi, bronchioles, blood vessels and alveoli. 2 pleural membranes: lining the thoracic cavity and as the outside of the lung. The membranes have a lubricating fluid between them for inhalation / exhalation. Note: inhaling is not due to lungs contracting (they are not muscles)  Gas transport: oxygen and carbon dioxide Oxygen: Bound to hemoglobin: 98% Dissolved in blood plasma (water): 2% (oxygen is not that soluble in water / blood plasma). Carbon dioxide: Bound to hemoglobin (23%) Dissolved in blood plasma (7%), or in the form of plasma bicarbonate (70%). Carbon dioxide diffusing into alveoli from capillaries causes more carbon dioxide to form, which continues to diffuse into alveoli CO2 + H2O H2CO3 HCO3- + H+ 7% 70% Nervous system regulation of breathing Respiratory center in medulla oblongata: Establishes basic breathing pattern: Inhalation: Stimulation of diaphragm and intercostal muscles every 4-5 sec. Exhalation: Stretch receptors (attached to lungs) signal brain to stop muscle contraction. Stimulation stops, muscles relax, diaphragm returns to domed shape, ribs return to previous shape due to recoil. Nervous system regulation of breathing Chemical receptors in medulla oblongata: monitors hydrogen ions (carbon dioxide) in spinal fluid. More H+ (carbon dioxide)  faster and deeper breathing. Carotid and aortic bodies: sensitive to oxygen levels (and carbon dioxide, H+). Decreased oxygen leads to more and deeper breathing Hydrogen ion sensors are more sensitive, breathing rate usually responds to increased carbon dioxide, not decreased oxygen Brain can consciously control breathing rate too (diaphragm and intercostal muscles are both skeletal muscles) CO2 + H2O H2CO3 HCO3- + H+ Regulation of Breathing  Disorders of Respiratory System Infections: Pneumonia (bacterial or viral) Inflammation causes alveoli to secrete excess fluids that accumulate in alveoli impairing gas exchange. Can be deadly. Possibly a complication of the flu. Responsible for the majority of COVID deaths. Can be caused by severe air pollution as well. Tuberculosis (bacterial) Infection that damages lungs and produces lung scars. Very common: about 25% of the world has it (but only 5-15% are sick with it) It is the leading fatal infectious disease. Often leads to severe coughing (including coughing up blood) and difficulty breathing. Fatal without treatment.  Disorders of Respiratory System Cystic fibrosis (genetic disorder) very sticky mucus produced in air passages within lungs. This mucus impedes gas exchange and provides a favorable environment for bacterial infections. Infections often become fatal. Patients must have lungs drained periodically. More common among caucasians.  Disorders of Respiratory System Lung cancer (uncontrolled division of lung cells  tumors  impaired function) > 90% of lung cancer cases are due to cigarette smoke (it’s very preventable if you DON’T SMOKE) Slide 10.9