Respiratory System PDF

RESPIRATORY SYSTEM FUNCTIONS: Pulmonary ventilation (breathing): movement of air into and out of the lungs. The inspired air is filtered and the respiratory tract secretes a small amount of water and heat. Pulmonary Gas Exchange: diffusion of gases across plasma membranes; two type...

RESPIRATORY SYSTEM FUNCTIONS: Pulmonary ventilation (breathing): movement of air into and out of the lungs. The inspired air is filtered and the respiratory tract secretes a small amount of water and heat. Pulmonary Gas Exchange: diffusion of gases across plasma membranes; two types of Pulmonary gas exchange: External Pulmonary gas exchange: gas exchange between air in lungs and blood. Internal Tissue gas exchange: gas exchange between the blood and tissues Regulation of blood PH (changes the level of carbon dioxide) Production of chemical mediators (enzyme regulate blood pressure) Voice production (movement of air past vocal sound and speech) Olfaction (smell occurs when airborne molecules are drawn into nasal cavity) Protection (against microorganism entry) THE RESPIRATORY AND CARDIOVASCULAR SYSTEMS CONNECT IN PERFUSION oxygen delivery= cardiac output X arterial oxygen content For the respiratory system to carry out its functions involves 4 intricate processes: 1 BREATHING 2 EXTERNAL RESPIRATION -> GAS EXCHANGE AT THE LUNGS AND TISSUE (between lungs and environment) 3 TRANSPORTATION OF OXYGEN AND CARBON DIOXIDE 4 INTERNAL RESPIRATION-> GAS EXCHANGE AT THE TISSUE (between the blood and cell) WE NEED OXYGEN TO PRODUCE ATP, used as the main energy source for metabolic functions. When O2 or blood flow is reduced cells are at risk of cell death. Brain cells are the most vulnerable. Neuronal ATP levels break down very fast, with 90% ATP depleted in less than 5 minutes. Without ATP, the neuron can not maintain the correct ion flux- function is deregulated, the nerve cell swells and finally the cell bursts and dies. IT IS VERY IMPORTANT TO EXCRETE CARBON DIOXIDE FROM OUR BODY Carbon dioxide build-up causes acid build-up in the body which is toxic and creates havoc with our stable international environment for homeostasis The body only functions well with a pH 7.35-7.45  Carbon dioxide buildup would < pH All cells become functionally deregulated (especially nerve and cardiac cells) in acidic environments. It would eventually lead to cell death. BREATHING HAS BOTH VOLUNTARY AND INVOLUNTARY COMPONENTS: - VOLUNTARY BREATHING -> Conscious breathing involves direct control of the brain (blowing candles) - INVOLUNTARY (NORMAL) BREATHING-> The respiratory center is an involuntary nerve center that regulates the activities of respiration through RESPIRATORY REFLEX (sending impulses to the diaphragm and intercostal muscles) causing contractions/inspiration. Various regions called THE RESPIRATORY CENTRE located in the brain stem control this rhythmic pattern of breathing. MEDULLA OBLONGATA THE RHYTHMICITY CENTER-> Directly controls breathing inspiratory (normal) expiratory (forced). Sets basic rhythm Pons-> Modifies and Smoothes out the basic rhythm set by the medulla TOGETHER MEDULLA AND PONS MAINTAIN A NORMAL RESPIRATORY RATE, IN ADULTS 12/20 PER MINUTE. The rhythmicity area in the medulla oblongata sets the basic rhythm. Normal inspiration is initiated in the inspiratory area. NERVE IMPULSES ARE INITIATED VIA THE PHRENIC AND INTERCOSTAL NERVES AND STIMULATE the inspiratory muscles to contract (diaphragm and external intercostals). After 2 secs, inspiratory muscles relax, and expiration takes place passively. After 3 seconds of relaxation, the nerve impulses are initiated again and inspiratory muscles contract- a new ventilation cycle begins again. An Expiratory area (active only during forced breathing) stimulates accessory muscles. CHEMORECEPTORS: FUNCTION Based on oxygen and carbon dioxide levels (pH) chemoreceptors are sensory receptors that send information to the respiratory center BREATHING IS ALSO MODIFIED BY SENSORY INFORMATION-> RESPIRATORY REFLEX  GAS EXCHANGE This is the primary function of the respiratory system and is critical for ensuring a constant supply of oxygen to tissues, as well as safely and efficiently removing carbon dioxide. There are 3 basic steps to the process of gas exchange in the body: - PULMONARY VENTILATION (breathing)-> Air flow between atmosphere and alveoli due to alternating pressure differences created by contraction and relaxation of respiratory muscle Inhalation and exhalation. - EXTERNAL RESPIRATION (Pulmonary Exchange)-> diffusion of gases based on gradient - INTERNAL RESPIRATION (Tissue Exchange)-> diffusion of gases based on gradient PULMONARY CIRCULATION Rate of blood flow through the pulmonary circulation is = flow rate through the systemic circulation. Pulmonary vascular resistance is low Blood flow to the lungs is maintained by Autoregulation: –Matches ventilation /perfusion ratio GAS EXCHANGE -> Occurs between air and blood in the lungs (External Respiration) Occurs between blood and tissues (Internal Respiration) Depends on: partial pressures of the gases diffusion of molecules between gas liquid -solubility Atmospheric pressure is essentially the weight of air and produced by air molecules bumping into each other. Gas pressure can be measured inside or outside the lungs. NORMAL ATMOSPHERIC PRESSURE: (Sea level: 760 mm Hg) Each gas (partial pressure) contributes to the total pressure in proportion to its concentration (Dalton’s law). WHAT ELSE ENHANCES GAS EXCHANGE:  1. A large surface area (about 35 times the surface area of the body), The dense network of blood supply to the alveoli increases surface area and enhances gas exchange Histology of Alveoli 2. Alveoli and capillary walls are very thin (< 1 μm) –the distance for gases to travel is very small 3 Ventilation-perfusion rate Air flow and blood flow matched: ventilation-perfusion matching (V/P ratio). Normal pulmonary blood flow =5L/min; normal alveolar air flow = 4L/min. Normal V/P ratio = 0.8 Increased V/Q Ratio Emphysema (a type of COPD) Heart disease. Pulmonary hypertension Factors Affecting Diffusion Through the Respiratory Membrane Diffusion of gases through the respiratory membrane depends on three major factors. Partial pressure gradients Membrane thickness. The thicker the respiratory membrane, the lower the diffusion rate. Diseases like tuberculosis or pneumonia can increase membrane thickness as inflammatory fluid accumulates. Surface area: Decreased surface area decreases diffusion rate. Diseases like emphysema and lung cancer reduce available surface area. Gas exchange across respiratory membranes is reduced in ageing. THORACIC CAGE Composed of:the thoracic vertebrae posteriorly ribs laterally sternum and costal cartilages anteriorly FUNCTIONS: PROTECTIVE (organs like heart lungs, blood vessels) SUPPORT (upper limbs) ATTACHMENT (for neck, back, chest and shoulder) LIFT (the thorax during breathing) STERNUM (BREAST BONE) Made up of three parts -> manubrium, body, xiphoid process THORACIC VERTEBRAE-> 12 vertebrae, all articulate with the ribs RIBS 12 pairs of ribs, all attached to the vertebral column posteriorly First SEVEN -> true ribs are VERTEBROSTERNAL (attach directly to the sternum) The next 5 ribs -> false ribs are VERTEBROCHONDRAL (attached to the costal cartilage) Last 2 ribs-> FLOATING RIBS (don’t have any anterior attachment) TYPICAL RIB (2-10) -> Each rib has a head, neck, tubercle and shaft, costal groove/ head articulates with the vertebrae at the same level and tubercle articles with the transverse process of the thoracic vertebrae ATYPICAL RIB (1, 11, 12)-> The first rib only articulates with one vertebrae, and its fixed so no movement occurs at this joint-> The last two also articulate only with their vertebrae INTERCOSTAL SPACE/MUSCLES OF RESPIRATION-> is the area between two ribs, there are 3 layers of muscle within this space, EXTERNAL INTERCOSTAL (INSPIRATION - ELEVATES RIBS), INTERNAL & INNERMOST INTERCOSTAL ( EXPIRATION - DEPRESSES RIBS).  PLEURA Visceral pleura adheres to the surface of the lung and parietal pleura lines the thoracic cavity and the thoracic surface of the diaphragm. Pleural cavity contains pleural fluid which lubricates and prevents friction, it creates a surface tension which draws the surface of the lung to the thoracic wall. BREATHING: Ventilation-movement of air into/out of the lungs Inspiration-movement of air into the lungs Expiration-movement of air out of the lungs DIAPHRAGM Muscle located between abdomen and thorax Made up of central tendon and muscular part Inspiration contracts, muscle fibers shorten, central tendon is pulled downwards, enlarging the thoracic cavity BOYLE’S LAW-> states that decreasing volume creates an increase in pressure and that increasing volume creates a decrease in pressure PARTIAL PRESSURES The pressure exerted by an individual gas is its partial pressure (Dalton’s law) Dalton’s law of PP –Total pressure of a mixture of gases is equal to the sum of the partial pressures of the component gases CHANGES IN DIAMETER To expel air or bring it in, the pressure needs to be changed within the thorax Change the pressure by changing the diameter: -vertical diameter (diaphragm) -anteroposterior diameter (ribs) -transverse diameter (ribs) Inspiration  Diaphragm and external intercostal muscles contract Thoracic volume increases Intrapleural pressure drops Lungs expand into low-pressure thorax Intrapulmonary pressure decreases Air moves in Expiration Diaphragm and external intercostal relax (passive), lungs recoil (elasticity) Thoracic volume decreases Intrapleural pressure increases Lungs compressed into high-pressure thorax Intrapulmonary pressure increases Air moves out CHANGES IN PRESSURE AND VOLUME (BOYLE’S LAW) CAUSE AIR TO MOVE IN AND OUT OF THE LUNGS PULMONARY FUNCTION TESTS-> set of tests that can help to diagnose certain lung conditions. SPIROMETRY-> examines how well you breathe in and out (quick, non-invasive, and painless) PEAK FLOW-> measurement of how quickly you can blow air out of your lungs LUNG VOLUMES->Test that measures amount of air in the lungs -tidal volume, inspiratory reserve volume, expiratory reserve volume, and the residual volume. LUNG VOLUMES->Test that measures amount of air in the lungs -tidal volume, inspiratory reserve volume, expiratory reserve volume, and the residual volume. OXYGEN TRANSPORT IN THE BLOOD Oxygen Delivery = Cardiac Output X Arterial Oxygen Content Blood plasma can’t transport enough O2 to meet physiological needs.It requires a transport system. 1.5% Free in plasma 98.5% temporarily bound to hemoglobin as oxyhaemoglobin  RED BLOOD CELLS-> Transport O2 in the blood to the peripheral tissues where it is diffused into tissues/cells. 250 million haemoglobin per RBC. Chemical Binding Of Haemoglobin & oxygen-> Each hemoglobin has 4 polypeptide chains and 4 hemes.Each heme has 1 atom iron that can combine with 1 molecule 02. Each molecule of Hb carries 4 molecules of oxygen. O2 + Hb = OXYHAEMOGLOBIN, known as loading reaction O2 - Hb= DEOXYHAEMOGLOBIN know as unloading reaction Some Factors Which Affect Hb And Oxygen Bonding: Carbon monoxide found in smoke and fumes has 210 times stronger of a bond than oxygen (can die from smoke inhalation). Anaemia: the oxygen-carrying capacity of the blood is below normal due to an abnormally low Hb. Increasing temperature ‘hyperthermia’ heat exhaustion will weaken and denature the bond between oxygen and hemoglobin, decreasing the oxyhemoglobin concentration. Hb and RBC production is controlled by the hormone erythropoietin produced in the kidney in response to P02 blood levels. (Normal level production and death of Red blood cells is maintained by basal level of erythropoietin) CARBON DIOXIDE TRANSPORT IN THE BLOOD Carbon Dioxide is acid-producing our bodies are extremely intolerant of acidic the environment 70% Carbon dioxide is transported as bicarbonate ions 23%: primarily haemoglobin 7% in solution with plasma CARBAMINOHAEMOGLOBIN AT SYSTEMIC CAPILLARIES 23% Carbon Dioxide combines with Hb to form carbaminohaemoglobin (HbC02 ). As carbon dioxide binds to the Hb it causes the release of 02 from the Hb. 7% IN SOLUTION WITH PLASMA Carbon dioxide (C02 ) combines with water (H20) to form carbonic acid (H2C03). This occurs in both plasma (slow rate) and contributes some acidity to blood. HOW THE RESPIRATORY SYSTEM HELP PH HOMEOSTASIS THE PH SCALE-> It is the degree of concentration of hydrogen ions in a substance or solution. It is measured on a logarithmic scale from 0 to 1 pH balance is maintained by controlling H+ ion concentration in body fluids Normal blood pH (7.35-7.45- slightly alkaline is critical for normal cellular functions) Carbon Dioxide is acid-producing our bodies are extremely intolerant of acidic the environment The protein molecule’s 3-D shape is very sensitive to pH changes (denaturation). Nerve cells are sensitive to changes in blood pH. Extreme changes disrupt oxygen delivery to cells. Excess dietary protein metabolism results in excess acids. Excess carbon dioxide retention in the blood results in excess acids (remember carbonic acid) Several mechanisms help maintain blood pH (7.35–7.45) 1. Buffer systems 2. Exhalation of carbon dioxide by the respiratory system 3. Excretion of H+ in urine The respiratory system (lung) helps to regulate blood pH by altering blood carbon dioxide level. ACID-BASE IMBALANCES: ACIDOSIS AND ALKALOSIS Acidosis -> Systemic arterial blood pH below 7.35 (Accumulation of CO2 in the tissues >>>Plasma carbonic acid (HCO3- ) increases>>>pH decrease) Chemoreceptor- respiratory center – effector system respiratory compensation within minutes if the source of pH change is respiratory or metabolic. Acidosis – the respiratory response is an increased rate and depth of breathing that expels more CO2 (hyperventilation) Alkalosis-> Systemic arterial blood pH above 7.45 (Too little CO2 in the tissues >>>Plasma carbonic acid HCO3- diminishes >>>pH increase) Alkalosis – the respiratory rate is decreased and the depth of breathing accumulates CO2 in the blood BUFFERS -> act to temporarily prevent rapid, drastic shifts in pH by converting strong acid or base into a weak acid or base; don’t remove from the body - PROTEIN BUFFER -> Utilizes blood amino acid proteins such as hemoglobin and albumin Amino acids have a carboxyl group and the amino group Carboxyl group releases H+ when pH rises (H+ concentration falls) Amino group binds H+ when pH falls (H+ concentration increases) - CARBONIC ACID-BICARBONATE BUFFER-> Carbonic acid releases H+ when pH rises - Bicarbonate ion binds H+ when pH falls - Functions only if exhalation of CO2 is balanced The PCo2, carbonic acid, hydrogen and bicarbonate concentrations in blood are maintained relatively constant by normal ventilation and therefore contribute to maintaining normal blood pH. RESPIRATORY ASSESSMENT Blood oxygen levels -> Pulse oximetry is sometimes referred to as the fifth vital sign; it is a quick and non-invasive monitoring technique that measures the oxygen saturation in the blood by shining light at specific wavelengths through tissue, most commonly the fingernail bed RESPIRATORY RATE/ RHYTHM VARIATIONS-> A Rise above basal normal levels of respiratory rate at rest can be the first indicator of an acutely deterioration person. Basis of early warning score system. Children have normal higher respiratory rates compared to adults CHILDREN AND RESPIRATORY FUNCTION The diameter of an infant's trachea is about 4mm (comparable to a drinking straw) compared to an adult's diameter of 20mm so there is greater airway resistance (15 times greater than an adult's). Babies are more at risk of oedema and swelling in response to a virus, bacteria, or irritant. At this point, the lung tissue contains only 25 million alveoli, which are not fully developed. This increases to 300 million by 8 years QUALITY OF BREATHING -> Should be symmetrical chest breathing and autonomic- using diaphragm and external intercostal muscles The lung matures by age 20–25 years, and thereafter aging is associated with a progressive decline in lung function. Structural changes: There can be a reduction in total lung compliance leading to increased work of breathing. The lung tissue loses some supporting structure causing dilation of air spaces- this is often referred to as ‘senile emphysema’. Respiratory muscle strength decreases with age and can impair effective cough, which is important for airway clearance. The alveolar dead space increases with age, affecting arterial oxygen without impairing the carbon dioxide elimination. ALL CELLULAR OPERATIONS RELY ON WATER the body of an adult human being contains 70% water. Most of the water in the human body is contained inside our cells. Approx half of total weight of body is water. 2 major compartments: - Intracellular fluid compartment - Extracellular fluid compartment - Each compartment is composed of water, electrolytes, and other solutes with specific distribution in each compartment BODY WATER: Exact % of body water depends on: Age, gender and diet More water in infants then with age Less water in females as they have more adipose tissue than men. Less water in obese people (much less water in adipose tissue than in Muscle Fluid Compartments Intracellular fluid compartment. All fluids inside cells of body. About 40% of total body weight. EXCHANGE BETWEEN COMPARTMENTS The two major forces that determine fluid movement into and out of the blood are hydrostatic pressure and osmotic pressure. Total osmotic pressure in each compartment is approximately equal. Allows for continuous exchange of water and electrolytes. Osmosis has the greatest influence on maintaining fluid homeostasis between extracellular fluid compartments Fluid Balance: Water intake = Waterloss FLUID INPUT Changes in total water volume alter several factors including solute concentration of body fluids, blood pressure, and interstitial fluid pressure. Primary sources of fluid input are: Food and beverages (90%) Cellular respiration (10%) Provides 1.5 to 3.0 L of water per day FLUID OUTPUT Routes of water loss: Kidneys – 61% of fluid loss as urine Evaporation – 35% through the skin and respiratory passageways. Feces – 4% loss from the digestive tract REGULATION OF FLUID BALANCE Thirst is the sensation that induces an urge to drink liquids. Mechanisms that control thirst are: Osmoreceptors Baroreceptors Dryness of the mouth Distention of the stomach Hormonal Mechanisms Regulating Body Fluid Composition Blood volume changes are directly proportional to blood pressure changes. Three hormonal mechanisms regulated this relationship: Renin-angiotensin-aldosterone hormone mechanism Atrial natriuretic hormone (ANH) mechanism Antidiuretic hormone (ADH) mechanism RENIN-ANGIOTENSIN SYSTEM DROP IN BLOOD PRESSURE-> RENIN RELEASE FROM KIDNEY-> LIVER ANGIOTENSINOGEN-> RENIN ACTS ON ANGIOTENSINOGEN TO FORM ANGIOTENSIN 1-> LUNG RELEASE ACE-> ACE ACTS ON ANGIOTENSIN 1 TO FORM ANGIOTENSIN 11 -> ALSO ACT DIRECTLY ON BLOOD VESSELS STIMULATING VASOCONSTRICTION (This increased blood volume and therefore blood pressure) -> ANGIOTENSIN 11 ACTS ON THE ADRENAL GLAND TO STIMULATE THE RELEASE OF ALDOSTERONE-> ALDOSTERONE ACTS ON THE KIDNEYS TO STIMULATE THE REABSORPTION OF SALT AND WATER ELECTROLYTE BALANCE Electrolytes are formed when molecules dissociate into ions in water. Inorganic salts, inorganic acids and bases, some proteins. Nonelectrolytes do not dissociate into ions in water; for example, lipids, urea, glucose. Electrolytes, especially sodium, are the component of the body’s fluids that contribute the greatest influence to their osmolality and can be either cations or anions.  The concentration of solutes is determined by osmolality (Osm) which is the number of solute particles in a particular volume of solution. Adding water dilutes the concentration. Losing water would concentrate the solution. Regulation of Sodium 2Imbalances: Hyponatremia: low plasma sodium levels; can lead to confusion, seizures, and coma. Hypernatremia: high plasma sodium levels; can lead to pulmonary edema, and muscle convulsions.