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RESPIRATORY SYSTEM As you recall from the chapter on metabolism - cells need oxygen to carry out the process of ATP production - they also produce carbon dioxide as a waste product. The main function of the respiratory system and circulatory system is to ensure that enough oxygen reaches the tissues and that carbon dioxide is removed . The exchange of gases between the atmosphere, the lungs, and the tissues is called respiration In order to get oxygen to the tissues three processes are involved: 1. Pulmonary ventilation (breathing) is the exchange of gases between the atmosphere and the lungs 2. External respiration is the exchange of gases between the lungs and the blood. 3. Internal respiration is the exchange of gases between the blood and the tissues. Components - Upper respiratory system - nose, pharynx (throat) and associated structures - Lower respiratory system - larynx, trachea, bronchi, lungs - functionally there are two divisions: 1. Conducting portion - cavities and tubes 2. Respiratory portion - where gas exchange occurs - bronchioles alveolar ducts, and alveoli 40 Nose - two portions - an external and an internal portion - the external portion consists of: - the bone and cartilage framework with its mucous membranes that make up the structure that protrudes from your face - the two openings called the external nares or nostrils - the internal portion of the nose (the nasal cavity) consists of: - the large cavity bounded anteriorly by the external nose and posteriorly by the opening into the nasal pharynx called the internal nares - contains the nasal conchae and the openings to the paranasal sinuses: - consists of four different sinuses (named after the bones they are in); - Maxillary, Frontal, Ethmoidal, Sphenoidal (see figure above) - Physiology - the function of the nose is to: - warm the air - clean the air - moisten the air - the concha (turbinate bones) cause a vortex and also increase surface area - they are covered with mucous, hair cells, and are very moist and highly vascularized - the superior nasal concha contains the olfactory region for smell and pheromone reception - between the concha are regions known as meatus 41 Pharynx - serves as an airway for the respiratory system and partially (oropharynx and laryngopharynx) as a passageway for the digestive system - 3 portions (1) Nasopharynx - above the soft palate - openings to the eustachian tubes - covered with pseudostratified columnar epithelium - posterior wall contains the pharyngeal tonsils (2) Oropharynx - posterior to the mouth - the opening between the oral cavity and the oropharynx is called the fauces (3) Laryngopharynx - stratified squamous epithelium - is continuous with the esophagus 42 Larynx - the voice box - connects the laryngopharynx with the trachea - passageway for air going to and from the lungs - consists of 9 pieces of cartilage held together with muscles and membranes - the glottis is the opening through the larynx through which air passes. It is covered by the epiglottis during swallowing - voice production - 2 pairs of folds (1) Ventricular folds - uppermost - false focal folds - not involve in sound production - closes to prevent passage of foreign substances into trachea (2) Vocal folds - lowermost folds - true vocal folds sound production requires: - vocal folds, pharynx, mouth, tongue, nasal cavity, sinuses 43 Trachea - 4.5 inches long - divides into left and right primary bronchi - histology - 4 layers 1. mucosa - pseudostratified columnar epithelium with lots of mucous cells - traps dust and cila beats to transport mucous and dust into laryngopharynx 2. Submucosa - contains the mucous glands 3. Cartilagenous layer 16 to 20 incomplete (c shaped) rings closed by trachealis muscle and elastin 4. Adventitia - serosal layer - carina - ridge at junction of trachea/bronchi - very sensitive - location of cough reflex center Bronchi - primary bronchi go to left and right lungs - the right primary bronchi is more vertical , shorter, wider and more likely to receive foreign objects -each primary bronchi splits up into secondary bronchi - each goes to the lobe of the lung: 44 Lungs - gross anatomy of the lungs - base - sits on the diaphragm - apex - rises above the clavicles - hilus - where the bronchi and blood vessels enter - cardiac notch - the scooped out area of the left lung where the heart fits - lobes and fissures - oblique fissure on left and right lungs - horizontal fissure on right side only - 3 lobes on the right - superior, middle, and inferior - 2 lobes on the left - superior and inferior 45 Alveolus (alveoli) - air pockets - lined with capillaries - where gas exchange occurs Alveolar Sacs - common space into which alveoli empty Septal Cells - found in walls of alveoli - secrete surfactant to lower surface tension so walls of the alveoli do not stick together if lung loses all its air. Dust Cells (Alveolar Macrophages) - phagocytes that remove debris 46 Pulmonary Ventilation - exchange of gases between the atmosphere and the lungs - involves the movement of air (gases) due to pressure changes Boyle's Law - the pressure of a gas in a closed container is inversely proportional to the volume of the container Inspiration - the diaphragm is contracted and moves down (called deep or diaphragmatic breathing) or the External Intercostal muscle pull the ribs upward and outward (called eupnea or shallow breathing) - either action above causes the volume inside the thorax to increase, thereby lowering the intrapulmonary pressure (Boyle's law) - the air moves from regions of high pressure (the atmosphere) to regions of lower pressure (inside the lungs (intrapulmonary)) 47 Expiration - diaphragm relaxes or gravity pulls ribs down (or internal intercostal muscles pull the ribs down - in forced expiration) - either action above causes the volume inside the thorax to decrease, thereby raising the intrapulmonary pressure (Boyle's law) - the air moves from regions of high pressure (inside the lungs) to regions of lower pressure (the atmosphere) Note: the intrapleural space is always subatmospheric so that the lungs adhere to the parietal pleura 48 Atelectasis (at-e-LEK-ta-sis) - collapse of the lungs - surfactant (a phospholipid) prevents the walls of the alveoli from remaining in contact due to surface tension - respiratory distress syndrome - infants - deficiency in surfactant - can lead to CIDS Compliance - the ease with which the lungs and thoracic walls can be expanded - related to: - elasticity - surface tension - compliance decreases if: - lung tissue is destroyed - lung is filled with fluid Pulmonary Volumes Tidal Volume - quiet breathing, amount breathed in and out - about 500 ml Anatomic Dead Space - amount of air in the respiratory tract that does not reach the lungs - about 150ml Minute Volume - the amount of air taken in - in one minute Inspiratory Reserve - the amount of air that the lung can take in after a normal inhalation Expiratory Reserve - the amount of air the lung can breathe out after a normal exhalation Residual Volume - the amount of air left in the lungs after expiratory reserve 49 Exchange of Respiratory Gases Charle's Law - the volume of gas is directly proportional to its temperature - means that the gas in the lungs expands due to warming Dalton's Law - Each gas in a mixture of gases exerts its own pressure as if all other gases were not present Atmospheric Pressure = PO2 + PCO2 + PN2 + PH2O - can be determined for each gas as follows: - atmospheric PO2 = 21% X 760 mmHg = 160 mmHg -atmospheric PCO2 = .04% X 760 mmHg = .3 mmHg Henry's Law - the quantity of gas that will dissolve in a liquid is proportional to the partial pressure of the gas and its solubility coefficient, when the temperature remains constant - the solubility coefficients of: - CO2 = 0.57 - O2 = 0.024 - N2 = 0.01 - this means that CO2 can dissolve in blood but O2 and N2 cannot (unless the partial pressure of that gas increases) 50 Physiology of External Respiration External Respiration - the exchange of gases between the alveoli of the lungs and the blood in the respiratory capillaries - results in: deoxygenated blood becoming oxygenated blood NOTE: the gases diffuse down the concentration gradient ALVEOLI BLOOD PO2 105 mmHg ----------------------------------------> PO2 40 mmHg PCO2 40 mmHg <--------------------------------------- PCO2 45 mmHg 51 Physiology of Internal Respiration Internal Respiration - the exchange of gases between blood and the tissues BLOOD TISSUES PO2 105 mmHg -----------------------------------------> PO2 40 mmHg PCO2 40 mmHg <---------------------------------------- PCO2 45 mmHg Transportation of Respiratory Gases Oxygen - does not dissolve in plasma - combines with the heme portion of hemoglobin to form oxyhemoglobin Carbon Dioxide - each l00 ml of deoxygenated blood contains 4 ml of carbon dioxide - 7% of this is dissolved in the plasma - 23% combines with Hb to form carbaminohemoglobin - 70% is transported in plasma as bicarbonate ions Carbonic Anhydrase CO2 + H2O <----------------------> H2CO3 <----------> H+ + HCO3 Carbonic Bicarbonate acid ion - the bicarbonate ions leave the RBC and enter the blood plasma - in exchange Cl- ions diffuse from the plasma into the RBC and combine with K+ to form KCl - in the lungs the opposite reactions occur to release the CO2 into the alveoli 52 53