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Respiratory System. Anatomy and Function. Anatomy. Conducting Zone Nose to bronchioles Function: filter, warm, moisten incoming air Respiratory Zone Respiratory bronchioles to alveoli Gas exchange. Anatomy continued. Nose and paranasal sinuses Open to the exterior provides airway
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Respiratory System Anatomy and Function
Anatomy Conducting Zone • Nose to bronchioles • Function: filter, warm, moisten incoming air Respiratory Zone • Respiratory bronchioles to alveoli • Gas exchange
Anatomy continued • Nose and paranasal sinuses • Open to the exterior provides airway • Small hairs filter air • Olfactory receptors • Sinuses drain into the nasal cavity which is divided by the nasal septum • Pharynx • Houses the tonsils • Extends from base of skull to C6 vertebrae • Larynx • Contains vocal cords • Routes food and air into proper channels • Trachea • C-shaped cartilage rings and ciliated mucosa • Connect the larynx with the bronchi that lead to lung
Anatomy continued • Bronchial tree • Divide into right and left • Continue to subdivide into smaller passageways that end at the alveoli (air sacs) • Lungs and pleurae • Right lung has 3 lobes • Left lung has 2 lobes • Both have their own cavity called the pleural cavity • Pulmonary arteries carry blood to the lungs from the heart and pulmonary veins carry oxygenated blood back to the heart for circulation • Bronchial arteries provide blood to lung tissue
Breathing • Intrapulmonary pressure is pressure in the alveloi • Intrapleural pressure is pressure within the pleural cavity • Gasses travel from high to low pressure • Inspiration occurs when the diaphragm and external intercostal muscles contract increasing thorax volume, this decreases pressure and air rushes in • Expiration is passive and as the muscles relax the lungs recoil raising intrapulmonary pressure and forcing air out of the lungs
Pulmonary ventilation • Factors that hinder air passage • Airway resistance- airway diameter • Inhaled irritants activate a reflex that causes constriction of the bronchioles (asthma attack) • Histamines and other inflammatory chemicals cause constrictions, while epinephrine dilate the bronchioles • Accumulation of mucus, infectious material, or solid tumors in the passageways When resistance rises breathing becomes more strenuous
Surfactant • Fluid that coats the alveolar walls • Secreted by the type II alveoli cells • Made of lipids and proteins • Reduces the cohesive nature of water and forces the alveoli to stay open IRDS- infant respiratory distress syndrome Infants who are born premature have inadequate pulmonary surfactant prevents the infants from inflating the alveoli
Gas exchange • The composition of the atmosphere is different from the composition of gasses in your lungs • Your lungs have more water and CO2 than the atmosphere • Partial pressure of each component directs the exchange of that particular gas between the gaseous state (air) and the dissolved gas state (blood) • Hyperbaric oxygen chamber- provides a high O2 high pressure environment that forces more than normal amounts of O2 to be absorbed ex. If someone has CO poisoning.
Gas exchange Each inspiration supplies about 500ml of air which then mix with some remaining gases. If N2 makes up the majority of the air we intake why doesn’t it interfere with the exchange of O2 and CO2 ? • Answer: because N2 is much less soluble • The solubility of gasses are different CO2 is more soluble than O2 and N2 is nearly insoluble.
Gas exchange • The partial pressures of O2 and CO2 are easily changed by increasing breathing depth and rate. • In the pulmonary circuit, dark red blood unloads CO2 and picks up O2 which turns the blood bright red. • Hemoglobin molecules in the rbc pick up the O2 because they have a high affinity for O2 when O2 is abundant.
Summary of gas exchange • 3 factors that influence Partial pressure gradients and gas solubilities • Pressure in alveoli is 104 mm compared to the pulmonary artery 40 mm • Pressure equalizes within .25 seconds which is about 1/3 of the time a RBC spends in the pulmonary capilary Matching of alveolar ventilation and pulmonary blood perfusion • If either the air intake or the amount of blood is reduced then gas exchange is reduced • Pulmonary health and respiratory health are closely connected Structural characteristics of the respiratory membrane Healthy lung- 0.5 to 1 μm, surface area is approx 40x larger than the surface of the skin that covers the body
Hemoglobin • Made of 4 polypeptide chains attached to an iron atom. • Each chain and iron atom can bind to one O2 molecule • Hemoglobin is said to be saturated when it is bound to 4 O2 molecules. • Temperature, blood pH, and pressure potentials influence the binding of O2 to hemoglobin • At the tissue capillary there is an increase in CO2, acidic pH, and increase CO2 pressure all reduce hemoglobin’s affinity for Oxygen.
Control of Respiration Sensory impulses reach the brain stem and respiratory center, located in the pons and medulla • Excitatory influences • Chemoreceptors in the aortic arch and carotid arteries detect decreased levels of O2, increased levels of CO2, and increased H+ • Receptors in muscles and joints • Inhibitory influences • Stretch receptors in lungs and irritant receptors in the trachea Hypothalamus and Cerebral Cortex control voluntary breathing and responses to emotional stimuli and pain. Hyperventilationis an increase in the rate and depth of breathing that exceeds the body’s need to remove CO2.
