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The Respiratory System Respiratory System Respiratory System Organs of the Respiratory System • Upper respiratory system – Nose, nasal cavity, pharynx, glottis and larynx • Lower respiratory system – Trachea, bronchus, bronchioles, and lungs – Diaphragm-skeletal muscle; functions in ventilation All airways that carry air to lungs: • Nose, pharynx, larynx, trachea bronchi, bronchioles, and terminal bronchioles Sites within lungs where gas exchange occurs • Respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli Nose • Structure – External nares nasal cavity internal nares – Nasal septum divides nose into two sides – Nasal conchae covered by mucous membrane • Functions – Warm, humidify, filter/trap dust and microbes • Mucus and cilia of epithelial cells lining nose – Detect olfactory stimuli – Modify vocal sounds Large stiff Hairs Nose Sinuses Nasal Cavity Olfactory Receptors Pharynx Pharynx • Known as the “throat” • Structure – Funnel-shaped tube from internal nares to larynx • Three regions (with tonsils in the upper two) – Upper: nasopharynx; posterior to nose • Adenoids and openings of auditory (Eustachian) tubes – Middle: oropharynx; posterior to mouth • Palatine and lingual tonsils are here – Lower: laryngopharynx • Connects with both esophagus and larynx: food and air larynx • “Voice box” • Made largely of cartilage – Thyroid cartilage: V-shaped • “Adam's apple”: projects more anteriorly in males • Vocal cords “mucoso folds – Epiglottis: leaf-shaped piece; covers airway • During swallowing, larynx moves up so epiglottis covers opening into trachea-glottis – Cricoid cartilage: inferior most portion – Arytenoids (paired, small) superior to cricoid Larynx Vocal Cords: mucosal folds Lower Respiratory System: Larynx Trachea • “Windpipe” • Location – Anterior to esophagus and thoracic vertebrae – Extends from end of larynx to primary bronchi • Structure – Lined with pseudostratified ciliated columnar mucous membrane: traps and moves dust upward – C-shaped rings of cartilage support trachea, keep lumen open during exhalation • Tracheostomy: opening in trachea for tube Trachea • The methods outlined above, coughing, backblows, and abdominal thrusts (Heimlich maneuver) have a very high rate of success. In the event, however, that these methods fail to dislodge the obstructing material from the air pipe (trachea), a tracheotomy must be considered. Larynx tracheotomy Cricoid Cartilage Lungs • Two lungs: left and right – Right lung has 3 lobes – Left lung has 2 lobes • Lungs surrounded by pleural membrane – Parietal pleura attached to diaphragm and lining thoracic wall – Visceral pleura attached to lungs – Pleural cavity with little fluid between pleurae Lung Lobes Bronchi • Structure of bronchial tree – Bronchi contain cartilage rings – Primary bronchi enter the right and left lungs – In lungs, branching secondary bronchi • One for each lobe of lung: 3 in right, 2 in left – Tertiary bronchi terminal bronchioles • These smaller airways – Have less cartilage, more smooth muscle. – In asthma, these airways can close. Bronchioles • Respiratory bronchioles – Lined with nonciliated epithelium Alveolar ducts Alveolar sacs Surrounded by alveoli Terminal Alveolar Alveoli • Cup-shaped • Alveoli: composed of three types of cells – Lined with thin alveolar cells (simple squamous); sites of gas exchange – Surfactant-secreting cells. Surfactant: • Lowers surface tension (keeps alveoli from collapsing) • Humidifies (keeps alveoli from drying out) – Alveolar macrophages: “cleaners” • alveoli + capillary – Gases diffuse across these thin epithelial layers: air blood Alveolar Sac Surfactants Air • Mixture of gases (N2, O2,, CO2, H2O, and others) • Each gas has own partial pressure, such as PO2 or PN2 • Sum of all partial pressures = atmospheric pressure • Each gas diffuses down its partial pressure Diffusion • Diffusion across alveolar-capillary membrane – O2 diffuses from air (PO2 ~105 mm Hg) to pulmonary artery (“blue”) blood (PO2 ~40 mm Hg). (Partial pressure gradient = 65 mm Hg) • Continues until equilibrium (PO2 ~100-105 mm Hg) – Meanwhile “blue” blood (PCO2 ~45) diffuses to alveolar air (PCO2 ~40) (Partial pressure gradient = 5 mm Hg) • Occurs throughout body • O2 diffuses from blood to cells: down partial pressure gradient • PO2 lower in cells than in blood because O2 used in cellular metabolism • Meanwhile CO2 diffuses in opposite direction: cells blood Internal and External Respiration Transport of Carbon Dioxide • CO2 diffuses from tissues into blood • CO2 carried in blood: – Some dissolved in plasma (7%) – Bound to proteins including hemoglobin (23%) – Mostly as part of bicarbonate ions (70%) • CO2 + H2O H+ + HCO3- • Process reverses in lungs as CO2 diffuses from blood into alveolar air exhaled Transport of Oxygen and Carbon Dioxide External Respiration • • • • • • • Bicarbonate ions Carbonic ahydrase Acidosis Alkalosis Carbaminohemoglobin Oxyhemoglobin deoxyhemoglobin Control of Respiration • Nervous Control of Breathing is located in the medulla oblongata of brain • Chemical control are sensory receptors in the body that are sensitive to chemical composition of body fluids • Two sets of chemoreceptors sensitive to pH can cause breathing to speed up. Location: medulla oblongata and in the carotid arteries and aortic bodies . These chemoreceptors are stimulated by the Carbon dioxide concentration. Regulation of Respiratory Center • Chemoreceptor input to increase ventilation – Central receptors in medulla: sensitive to H+ or PCO2 – Peripheral receptors in arch of aorta + common carotids: respond to PO2 as well as H+ or PCO2 in blood • Blood and brain pH can be maintained by these negative feedback mechanisms Mechanism of Breathing • Inspiration: rib cage moves up and out • External intercostal muscles pull the ribs outward • Diaphragm contracts and move down • When pressure in lungs decreases, air comes rushing in. Expiration • Rib cage moves down and in • Internal intercostal muscles pull the ribs inward during forced expiration • Diaphragm relaxes and move up • When pressure in lungs increases, air is pushed out