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BIOLOGY 252 Human Anatomy & Physiology Chapter 23 The Respiratory System: Lecture Notes
The Respiratory System Cells continually use O 2 & release CO 2 Respiratory system designed for gas exchange Cardiovascular system transports gases in blood Failure of either system – rapid cell death from O 2 starvation
Respiratory System Anatomy Nose Pharynx = throat Larynx = voicebox Trachea = windpipe Bronchi = airways Lungs Locations of infections –upper respiratory tract is above vocal cords –lower respiratory tract is below vocal cords
Nose - Internal Structures Large chamber within the skull Roof is made up of ethmoid and floor is hard palate Internal nares (choanae) are openings to pharynx Nasal septum is composed of bone & cartilage Bony swelling or conchae on lateral walls See lab manual p – 1.17
Functions of the Nasal Structures Olfactory epithelium for sense of smell Pseudostratified ciliated columnar with goblet cells lines nasal cavity –warms air due to high vascularity –mucous moistens air & traps dust (cleanse) –cilia move mucous towards pharynx Paranasal sinuses open into nasal cavity –found in ethmoid, sphenoid, frontal & maxillary –lighten skull & resonate voice
Pharynx Muscular tube (5 inch long) hanging from skull –skeletal muscle & mucous membrane Extends from internal nares to cricoid cartilage Functions –passageway for food and air –resonating chamber for speech production –tonsil (lymphatic tissue) in the walls protects entryway into body Distinct regions -- nasopharynx, oropharynx and laryngopharynx
Cartilages of the Larynx Thyroid cartilage forms Adam’s apple Epiglottis - leaf-shaped piece of elastic cartilage –during swallowing, larynx moves upward –epiglottis bends to cover glottis Cricoid cartilage - ring of cartilage attached to top of trachea Pair of arytenoid cartilages sit upon cricoid –many muscles responsible for their movement –partially buried in vocal folds (true vocal cords) –See lab manual – p
Larynx Cartilage & connective tissue tube Anterior to C4 to C6 Constructed of 3 single & 3 paired cartilages
Trachea Size is 12 cm (5 in) long & 2.5 cm (1in) in diameter Extends from larynx to T5 anterior to the esophagus and then splits into bronchi Layers –mucosa = pseudostratified columnar with cilia & goblet cells –submucosa = loose connective tissue & seromucous glands –hyaline cartilage = 16 to 20 incomplete rings open side facing esophagus contains trachealis m. (smooth) internal ridge on last ring called carina –adventitia binds it to other organs –See lab manual p. 2.5 – 2.7
Trachea and Bronchial Tree Full extent of airways is visible starting at the larynx and trachea
Histology of the Trachea Ciliated pseudostratified columnar epithelium Hyaline cartilage as C-shaped structure closed by trachealis muscle
Airway Epithelium Ciliated pseudostratified columnar epithelium with goblet cells produce a moving mass of mucus.
Tortora & Grabowski 9/e 2000 JWS Tracheostomy and Intubation Tracheotomy, syn. = Tracheostomy Reestablishing airflow past an airway obstruction –crushing injury to larynx or chest –swelling that closes airway –vomit or foreign object Tracheostomy is incision in trachea below cricoid cartilage if larynx is obstructed Intubation is passing a tube from mouth or nose through larynx and into trachea
Bronchi and Bronchioles Primary bronchi supply each lung Secondary bronchi supply each lobe of the lungs (3 right + 2 left) Tertiary bronchi supply each bronchopulmonary segment Repeated branchings called bronchioles form a bronchial tree
Tortora & Grabowski 9/e 2000 JWS Tidal volume = amount air moved during quiet breathing MVR= minute ventilation is amount of air moved in a minute Reserve volumes ---- amount you can breathe either in or out above that amount of tidal volume Residual volume = 1200 mL permanently trapped air in system Vital capacity & total lung capacity are sums of the other volumes Lung Volumes and Capacities
Structures within a Lobule of Lung Branchings of single arteriole, venule & bronchiole are wrapped by elastic CT Respiratory bronchiole –simple squamous Alveolar ducts surrounded by alveolar sacs & alveoli –sac is 2 or more alveoli sharing a common opening
Photomicrograph of lung tissue showing bronchioles, alveoli and alveolar ducts. Histology of Lung Tissue
Cells Types of the Alveoli Type I alveolar cells –simple squamous cells where gas exchange occurs Type II alveolar cells (septal cells) –free surface has microvilli –secrete alveolar fluid containing surfactant Alveolar dust cells –wandering macrophages remove debris
Details of Respiratory Membrane Find the 4 layers that comprise the respiratory membrane
Alveolar-Capillary Membrane Respiratory membrane = 1/2 micron thick Exchange of gas from alveoli to blood 4 Layers of membrane to cross –alveolar epithelial wall of type I cells –alveolar epithelial basement membrane –capillary basement membrane –endothelial cells of capillary Vast surface area = handball court
Double Blood Supply to the Lungs Deoxygenated blood arrives through pulmonary trunk from the right ventricle Bronchial arteries branch off of the aorta to supply oxygenated blood to lung tissue Venous drainage returns all blood to heart
Breathing or Pulmonary Ventilation Air moves into lungs when pressure inside lungs is less than atmospheric pressure –How is this accomplished? Air moves out of the lungs when pressure inside lungs is greater than atmospheric pressure –How is this accomplished? Atmospheric pressure = 1 atm or 760mm Hg
Boyle’s Law As the size of closed container decreases, pressure inside is increased The molecules have less wall area to strike so the pressure on each inch of area increases.
Dimensions of the Chest Cavity Breathing in requires muscular activity & chest size changes Contraction of the diaphragm flattens the dome and increases the vertical dimension of the chest
Diaphragm moves 1 cm & ribs lifted by external intercostal muscles and we inhale 500 ml of air If Diaphragm moves 10 cm & ribs are lifted accordingly Intrathoracic pressure falls and we inhale 2-3 liter of air. Quiet Inspiration
Passive process with no muscle action Elastic recoil & surface tension in alveoli pulls inward Alveolar pressure increases & air is pushed out Quiet Expiration
Labored Breathing Forced expiration –abdominal mm force diaphragm up –internal intercostals depress ribs Forced inspiration –sternocleidomastoid, scalenes & pectoralis minor lift chest upwards as you gasp for air
Intrapleural pressures or Intrathoracic pressures (see text p. 859) & Alevolar or Intrapulmponary pressures Always subatmospheric (756 mm Hg) As diaphragm contracts intrathoracic pressure decreases even more (754 mm Hg)
Alveolar Surface Tension Thin layer of fluid in alveoli causes inwardly directed force = surface tension –water molecules strongly attracted to each other Causes alveoli to remain as small as possible Detergent-like substance called surfactant produced by Type II alveolar cells –lowers alveolar surface tension –insufficient in premature babies so that alveoli collapse at end of each exhalation
Tortora & Grabowski 9/e 2000 JWS Pneumothorax Pleural cavities are sealed cavities not open to the outside Injuries to the chest wall that let air enter the intrapleural space –causes a pneumothorax –collapsed lung on same side as injury –surface tension and recoil of elastic fibers causes the lung to collapse
Tortora & Grabowski 9/e 2000 JWS Compliance of the Lungs Ease with which lungs & chest wall expand depends upon elasticity of lungs & surface tension Some diseases reduce compliance –tuberculosis forms scar tissue –pulmonary edema - fluid in lungs & reduced surfactant –paralysis
Airway Resistance Resistance to airflow depends upon airway size –increase size of chest airways increase in diameter –contract smooth muscles in airways decreases in diameter
Breathing Patterns Eupnea = normal quiet breathing (yu-p-ne a) Apnea = temporary cessation of breathing (ap ne a) Dyspnea =difficult or labored breathing (disp-ne a) Tachypnea = rapid breathing (tak-ip-ne a) Diaphragmatic breathing = descent of diaphragm causes stomach to bulge during inspiration Costal breathing = just rib activity involved
Modified Respiratory Movements Coughing –deep inspiration, closure of glottis & strong expiration blasts air out to clear respiratory passages Hiccuping –spasmodic contraction of diaphragm & quick closure of glottis produce sharp inspiratory sound Valsalva maneuver - forced exhalation against a closed glottis as may occur when lifting a heavy weight Chart of others on page 868
Tortora & Grabowski 9/e 2000 JWS The Gas Laws Boyle’s Law – the pressure of a gas varies inversely with its volume (if temperature remains constant). Gay-Lussac’s Law – the pressure of a gas increases directly in proportion to its (absolute) temperature.
Tortora & Grabowski 9/e 2000 JWS The Gas Laws Dalton’s Law – in a mixture of gasses, each gas exerts a partial pressure, proportional to its concentration. Henry’s Law – the quantity of a gas that will dissolve in a liquid is directly proportional to its partial pressure, if temperature remains constant.
Tortora & Grabowski 9/e 2000 JWS What is the Composition of Air? Air = 20.93% O 2, 79.04% N 2 and 0.03% CO 2 Alveolar air = 14% O 2, 79% N 2 and 5.2% CO 2 Expired air = 16% O 2, 79% N 2 and 4.5% CO 2 –Anatomic dead space = 150 ml of 500 ml of tidal volume
Dalton’s Law In a mixture of gasses, each gas exerts a partial pressure, proportional to its concentration. Each gas in a mixture of gases exerts its own pressure as if all other gases were not present partial pressures denoted as p Total pressure is sum of all partial pressures atmospheric pressure (760 mm Hg) = pO 2 + pCO 2 + pN 2 + pH 2 O Thus in atmospheric air with a total pressure of 760 mm Hg, O 2 which makes up 20.93% - has a partial pressure of 20.93/100 x 760 = mm Hg.
Henry’s Law The quantity of a gas that will dissolve in a liquid is directly proportional to its partial pressure, if temperature remains constant. OR The quantity of a gas that will dissolve in a liquid depends upon the amount of gas present and its solubility coefficient
Tortora & Grabowski 9/e 2000 JWS Partial Pressures of Respiratory Gases at Sea Level Total H 2 O O CO N Partial pressure (mmHg) % inDryAlveolarArterialVenousDiffusion Gasdry airairairbloodbloodgradient
Tortora & Grabowski 9/e 2000 JWS The Processes of Respiration Pulmonary ventilation – or breathing, is the mechanical flow of air into (inhalation) and or out of (exhalation) the lungs External respiration – is the exchange of gases between the alveoli of the lungs and the blood in the pulmonary capillaries. In this process, pulmonary capillary blood gains O 2 and loses CO 2 Internal respiration – is the exchange of gases between blood in systemic capillaries and tissue cells. The blood loses O 2 and gains CO 2. Within cells, the metabolic reactions that consume O 2 and give off CO 2 during the production of ATP termed cellular respiration ___________________________________________________ Gas transport – is the transport of O 2 from the lungs to the systemic tissues and the transport of CO 2 from the systemic tissues to the lungs.
External Respiration Gases diffuse from areas of high partial pressure to areas of low partial pressure Exchange of gas between alveolar air & blood Deoxygenated blood becomes 100% saturated with O 2 Compare gas movements in pulmonary capillaries to tissue capillaries
Rate of Diffusion of Gases Depends upon partial pressure of gases in air –pO 2 at sea level is mm Hg –10,000 feet (~3000 m) is 110 mm Hg / 50,000 feet is 18 mm Hg Large surface area of our alveoli Diffusion distance is very small (0.5 µm) Solubility & molecular weight of gases –O 2 smaller molecule diffuses somewhat faster –CO 2 dissolves 24x more easily in water so net outward diffusion of CO 2 is much faster
Internal Respiration Exchange of gases between blood & tissues Conversion of oxygenated blood into deoxygenated Observe diffusion of O 2 inward –at rest 25% of available O 2 enters cells –during exercise more O 2 is absorbed Observe diffusion of CO 2 outward
Oxygen Transport in the Blood Oxyhemoglobin contains 98.5% chemically combined oxygen and hemoglobin – inside red blood cells Does not dissolve easily in water –only 1.5% transported dissolved in blood (plasma)
Tortora & Grabowski 9/e 2000 JWS Carbon Monoxide Poisoning CO from car exhaust & tobacco smoke Binds to the Hb heme group more successfully than O 2 CO poisoning Treat by administering pure O 2
Tortora & Grabowski 9/e 2000 JWS Carbon Dioxide Transport Is carried by the blood in 3 ways –dissolved in plasma –combined with the globin part of Hb molecule forming carbaminohemoglobin –as part of bicarbonate ion CO 2 + H 2 O combine to form carbonic acid (H 2 CO 3 ) that dissociates into hydrogen ions (H+) and bicarbonate ions (HCO 3 - )
Blood is almost fully saturated at pO 2 of 60mm –people OK at high altitudes & with some diseases Between 40 & 20 mm Hg, large amounts of O 2 are released as in areas of need like contracting muscle Oxyhemoglobin Dissociation Curve (Hemoglobin saturation and oxygen partial pressure)
Acidity & Oxygen Affinity for Hb As acidity increases, O 2 affinity for Hb decreases Bohr effect H+ binds to hemoglobin & alters it O 2 left behind in needy tissues
pCO2 & Oxygen Release As pCO 2 rises with exercise, O 2 is released more easily CO 2 converts to carbonic acid & becomes H+ and bicarbonate ions & lowers pH.
Temperature & Oxygen Release Metabolic activity & heat As temperature increases, more O 2 is released
Role of the Respiratory Center Respiration controlled by neurons in pons & medulla 3 groups of neurons –medullary rhythmicity –pneumotaxic –apneustic centers
Tortora & Grabowski 9/e 2000 JWS CONDITIONS AT VARIOUS ALTITUDES
Tortora & Grabowski 9/e 2000 JWS Partial Pressures of Respiratory Gases at Sea Level Total H 2 O O 2 CO 2 N Partial pressure (mmHg) % inDryAlveolarArterialVenousDiffusion Gasdry airairairbloodbloodgradient