Respiratory System

Respiration Ventilation: Movement of air into and out of lungs External respiration: Gas exchange between air in lungs and blood Transport of oxygen and carbon dioxide in the blood Internal respiration: Gas exchange between the blood and tissues Cellular Respiration: The use of O2 to produce ATP via Glycolysis, TCA cycle, & ETS

Respiratory System Functions Gas exchange: Oxygen enters blood and carbon dioxide leaves Regulation of blood pH: Altered by changing blood carbon dioxide levels Carbonic acid Buffer system Sound production: Movement of air past vocal folds makes sound and speech Olfaction: Smell occurs when airborne molecules drawn into nasal cavity Thermoregulation: Heating and cooling of body Protection: Against microorganisms by preventing entry and removing them

Respiratory System Divisions Upper tract Nose, pharynx and associated structures, Larynx. Lower tract trachea, bronchi, lungs

Nasal Cavity and Pharynx

Nasal Cavity and Pharynx

Nose and Pharynx Nose Pharynx External nose Nasal cavity Functions Passageway for air Cleans the air Humidifies, warms air Smell Along with paranasal sinuses are resonating chambers for speech Pharynx Common opening for digestive and respiratory systems Skull-C6 Three regions Nasopharynx Oropharynx Laryngopharynx

Larynx Functions Maintain an open passageway for air movement Epiglottis and vestibular folds prevent swallowed material from moving into larynx Vocal folds are primary source of sound production

Vocal Folds

Trachea Windpipe Divides to form Insert Fig 23.5 all but b Rt , Lt Primary bronchi Carina: Cough reflex Insert Fig 23.5 all but b

Tracheobronchial Tree Non-Acinus -Conducting zone Trachea to terminal bronchioles which is ciliated for removal of debris, mucus lined Passageway for air movement controlled by smooth muscle at end of terminal bronchioles Cartilage holds tube system open and smooth muscle controls tube diameter Acinus Portion - Respiratory zone Respiratory bronchioles to alveoli Site for gas exchange Area the size of a football field

Tracheobronchial Tree

Bronchioles and Alveoli

Alveolus and Respiratory Membrane

Lungs Two lungs: Principal organs of respiration Divisions Right lung: Three lobes, shorter, broader, and has a greater volume. Left lung: Two lobes, is longer and narrower than the right lung Divisions Lobes, bronchopulmonary segments, lobules

Lungs The only point of attachment for each lung is at the hilum, or root, on the medial side. This is where the bronchi, blood vessels, lymphatics, and nerves enter the lungs. Each lung is enclosed by a double-layered serous membrane, called the pleura. The visceral pleura is firmly attached to the surface of the lung. At the hilum, the visceral pleura is continuous with the parietal pleura that lines the wall of the thorax. The small space between the visceral and parietal pleurae is the pleural cavity. It contains a thin film of serous fluid that is produced by the pleura. The fluid acts as a lubricant to reduce friction as the two layers slide against each other, and it helps to hold the two layers together as the lungs inflate and deflate.

Thoracic Walls Muscles of Respiration

Thoracic Volume

Pleura Pleural fluid produced by pleural membranes Acts as lubricant Helps hold parietal and visceral pleural membranes together

Pressure – Volume Relationships As vol. , pressure  As vol. , pressure  This is given by Boyle’s Law which says: P1V1 = P2V2 Why does this occur? Remember, pressure equals force/area P = Force/Area So, in this equation as A gets larger P must get smaller.

Ventilation Movement of air into and out of lungs via negative pressure pump mechanism Air moves from area of higher pressure outside the lung to area of lower pressure created in the thorax and lungs by diaphram Pressure is inversely related to volume in that as pressure goes down lung volume goes up

Inspiration Begins with the contraction of the diaphragm and the external intercostals This causes thoracic volume to  Which causes lung volume to  Which causes lung pressure to  Now Palv is <Patm so air will flow down its pressure gradient and enter the lungs. Inspiration ends when Palv=Patm

Inspiration Active process involving the diaphragm and intercostal muscles

3 Muscle Groups of Inhalation Diaphragm: contraction draws air into lungs 75% of normal air movement External intracostal muscles: assist inhalation 25% of normal air movement Accessory muscles assist in elevating ribs: sternocleidomastoid serratus anterior pectoralis minor scalene muscles

Quiet expiration is a passive process that is due to the elasticity of the lungs. Forced expiration is an active process due to contraction of oblique and transverse abdominus muscles, internal intercostals, and the latissimus dorsi. Expiration

Expiration Usually passive Can become active Using internal intercoastal and abdominal muscles

Alveolar Pressure Changes

Changing Alveolar Volume Lung recoil Causes alveoli to collapse resulting from Elastic recoil and surface tension : Pneumothorax Surfactant: Reduces tendency of lungs to collapse Pleural pressure Negative pressure can cause alveoli to expand Pneumothorax is an opening between pleural cavity and air that causes a loss of pleural pressure

Compliance Measure of the ease with which lungs and thorax expand The greater the compliance, the easier it is for a change in pressure to cause expansion A lower-than-normal compliance means the lungs and thorax are harder to expand Conditions that decrease compliance Pulmonary fibrosis Pulmonary edema Respiratory distress syndrome.

Alveolar Membrane Surfactant and water layer Alveolar wall- Simple squamous epithelium 3) Basement membrane of alveolar wall 4) Interstitial space 5) Capillary wall- Simple squamous epithelium 6) Basement membrane of cap wall.

Alveolar Capillary Membrane

The factors that effect rate of gas exchange Partial pressure gradients of O2 and CO2 Surface area of alveolar membrane Thickness of capillary-alveolar membrane Ventilation- perfusion mismatch

Pulmonary Volumes Tidal volume Inspiratory reserve volume Volume of air inspired or expired during a normal inspiration or expiration Inspiratory reserve volume Amount of air inspired forcefully after inspiration of normal tidal volume Expiratory reserve volume Amount of air forcefully expired after expiration of normal tidal volume Residual volume Volume of air remaining in respiratory passages and lungs after the most forceful expiration

Pulmonary Capacities Inspiratory capacity Functional residual capacity Tidal volume plus inspiratory reserve volume Functional residual capacity Expiratory reserve volume plus the residual volume Vital capacity Sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume Total lung capacity Sum of inspiratory and expiratory reserve volumes plus the tidal volume and residual volume

Pulmonary Capacities Inspiratory capacity is the total amt of air that can be inspired after a tidal expiration: IC = TV + IRV Functional residual capacity is the amt of air in the lungs after a tidal expiration: FRC = ERV + RV Vital capacity is the total amt of exchangeable air: VC = TV+IRV+ERV Total lung capacity is the sum of all lung volumes and is normally around 6L in males: TLC = VC + RV

Spirometer and Lung Volumes/Capacities

Lung Capacities Lung Volumes: TV IRV ERV RV Lung Capacities: VC FRC TLC IC

Minute and Alveolar Ventilation Minute ventilation: Total amount of air moved into and out of respiratory system per minute Respiratory rate or frequency: Number of breaths taken per minute Anatomic dead space: Part of respiratory system where gas exchange does not take place Alveolar ventilation: How much air per minute enters the parts of the respiratory system in which gas exchange takes place

Physical Principles of Gas Exchange Partial pressure The pressure exerted by each type of gas in a mixture Dalton’s law Water vapor pressure Diffusion of gases through liquids Concentration of a gas in a liquid is determined by its partial pressure and its solubility coefficient Henry’s law

Physical Principles of Gas Exchange Diffusion of gases through the respiratory membrane Depends on membrane’s thickness, the diffusion coefficient of gas, surface areas of membrane, partial pressure of gases in alveoli and blood Relationship between ventilation and pulmonary capillary flow Increased ventilation or increased pulmonary capillary blood flow increases gas exchange Physiologic shunt is deoxygenated blood returning from lungs

Oxygen and Carbon Dioxide Diffusion Gradients Moves from alveoli into blood. Blood is almost completely saturated with oxygen when it leaves the capillary P02 in blood decreases because of mixing with deoxygenated blood Oxygen moves from tissue capillaries into the tissues Carbon dioxide Moves from tissues into tissue capillaries Moves from pulmonary capillaries into the alveoli.

Gas Exchange

Changes in Partial Pressures

Hemoglobin and 02 Transport 280 million hemoglobin/ RBC. Each hemoglobin has 4 polypeptide chains and 4 hemes. Each heme has 1 atom iron that can combine with 1 molecule 02.

Hemoglobin Hemoglobin production controlled by erythropoietin. Production stimulated by P02 delivery to kidneys. Loading/unloading depends: P02 of environment. Affinity between hemoglobin and 02.

Hemoglobin and Oxygen Transport Oxygen is transported by hemoglobin (98.5%) and is dissolved in plasma (1.5%) Oxygen-hemoglobin dissociation curve shows that hemoglobin is almost completely saturated when P02 is 80 mm Hg or above. At lower partial pressures, the hemoglobin releases oxygen. A shift of the curve to the left because of an increase in pH, a decrease in carbon dioxide, or a decrease in temperature results in an increase in the ability of hemoglobin to hold oxygen

Hemoglobin and Oxygen Transport A shift of the curve to the right because of a decrease in pH, an increase in carbon dioxide, or an increase in temperature results in a decrease in the ability of hemoglobin to hold oxygen The substance 2.3-bisphosphoglycerate increases the ability of hemoglobin to release oxygen Fetal hemoglobin has a higher affinity for oxygen than does maternal

Shifting the Curve

C02 Transport C02 transported in the blood: HC03- (70%). Dissolved C02 (10%). Carbaminohemoglobin (20%).

Transport of Carbon Dioxide Carbon dioxide is transported as bicarbonate ions (70%) in combination with blood proteins (23%) and in solution with plasma (7%) Hemoglobin that has released oxygen binds more readily to carbon dioxide than hemoglobin that has oxygen bound to it (Haldane effect) In tissue capillaries, carbon dioxide combines with water inside RBCs to form carbonic acid which dissociates to form bicarbonate ions and hydrogen ions

Transport of Carbon Dioxide In lung capillaries, bicarbonate ions and hydrogen ions move into RBCs and chloride ions move out. Bicarbonate ions combine with hydrogen ions to form carbonic acid. The carbonic acid is converted to carbon dioxide and water. The carbon dioxide diffuses out of the RBCs. Increased plasma carbon dioxide lowers blood pH. The respiratory system regulates blood pH by regulating plasma carbon dioxide levels

Carbon Dioxide Transport and Chloride Movement

Respiratory Areas in Brainstem Medullary respiratory center Dorsal groups stimulate the diaphragm Ventral groups stimulate the intercostal and abdominal muscles Pontine (pneumotaxic) respiratory group Involved with switching between inspiration and expiration

Respiratory Structures in Brainstem

Rhythmic Ventilation Starting inspiration Increasing inspiration Medullary respiratory center neurons are continuously active Center receives stimulation from receptors and simulation from parts of brain concerned with voluntary respiratory movements and emotion Combined input from all sources causes action potentials to stimulate respiratory muscles Increasing inspiration More and more neurons are activated Stopping inspiration Neurons stimulating also responsible for stopping inspiration and receive input from pontine group and stretch receptors in lungs. Inhibitory neurons activated and relaxation of respiratory muscles results in expiration.

Modification of Ventilation Chemical control Carbon dioxide is major regulator Increase or decrease in pH can stimulate chemo- sensitive area, causing a greater rate and depth of respiration Oxygen levels in blood affect respiration when a 50% or greater decrease from normal levels exists Cerebral and limbic system Respiration can be voluntarily controlled and modified by emotions

Modifying Respiration

Regulation of Blood pH and Gases

Herring-Breuer Reflex Limits the degree of inspiration and prevents overinflation of the lungs Infants Reflex plays a role in regulating basic rhythm of breathing and preventing overinflation of lungs Adults Reflex important only when tidal volume large as in exercise

Ventilation in Exercise Ventilation increases abruptly At onset of exercise Movement of limbs has strong influence Learned component Ventilation increases gradually After immediate increase, gradual increase occurs (4-6 minutes) Anaerobic threshold is highest level of exercise without causing significant change in blood pH If exceeded, lactic acid produced by skeletal muscles

Effects of Aging Vital capacity and maximum minute ventilation decrease Residual volume and dead space increase Ability to remove mucus from respiratory passageways decreases Gas exchange across respiratory membrane is reduced.

Ventilation Patterns Eupnea - Normal, quiet breathing Dyspnea - Difficult breathing Apnea - absence of breathing Tachypnea - Rapid breathing rate Bradypnea - Slow breathing Hyperpnea - Deep breathing Hypopnea - Shallow breathing Hyperventilation - Rapid, deep breathing Cheyne-Stokes breathing - periods of apnea interspersed with hyperpnea