Normal Respiration for Online PDF

The Respiratory System Respiratory System Anatomy ◼ Structurally ❑ Upper respiratory system ◼ Nose, pharynx and associated structures ❑ Lower respiratory system ◼ Larynx, trachea, bronchi and lungs ◼ Functionally ❑ Conducting zone – conducts air to lungs → alwa...

The Respiratory System Respiratory System Anatomy ◼ Structurally ❑ Upper respiratory system ◼ Nose, pharynx and associated structures ❑ Lower respiratory system ◼ Larynx, trachea, bronchi and lungs ◼ Functionally ❑ Conducting zone – conducts air to lungs → always open ◼ Nose, pharynx, larynx, trachea, bronchi, bronchioles ❑ Respiratory zone – main site of gas exchange → elastic ◼ Respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli Larynx Epiglottis function: covering the airways during swallowing the food or liquid. Trachea ❑ Extends from larynx to superior border of T5 ◼ Divides into right and left primary bronchi ❑ 16-20 C-shaped hyaline cartilages ◼ Open part faces esophagus Why the conduction part of respiratory system has such strong cough reflex? – with the strongest reflex in the Carina. Bronchi ❑ Trachea bifurcates at Carina – which is the most sensitive area for triggering cough reflex ❑ Trachea bifurcates to right and left 1o bronchi that supply right & left lungs ◼ 1o bronchi (go to entire lungs) divide to become form bronchial tree ◼ 2o lobar bronchi ◼ 3o segmental bronchi – the smallest part that can be surgically removed ◼ Bronchioles – have beta 2 (β2) adreno-receptors → bind adrenaline → which dilates bronchioles (this is sympathetic nervous system SNS effect) ◼ What will happen if we block beta 2 receptors? → no binding of adrenaline → unable to dilate ❑ Structural changes with branching – the large bronchi are rather rigid and cannot collapse. While smaller bronchioles and alveoli are elastic. ❑ We call the division of 1o bronchi “bronchial tree” Pleura ❑ Each lung enclosed by double-layered pleural membrane ◼ Parietal pleura ◼ Visceral pleura ❑ Pleural space or cavity is between the two layers – MUST maintain negative pressure so that lungs won’t collapse. ◼ Pleural fluid reduces friction, produces surface tension (stick together) ◼ Cardiac notch – heart makes left lung 10% smaller than right Parietal Lung pleura Visceral pleura Pleural space Diaphragm Anatomy of Lungs ◼ Lungs receive 1o bronchi ◼ Lobes receive 2o bronchi (right lung has 3 lobes and left lung has 2 lobes) ◼ Segments receive 3o bronchi ◼ Lobules receive bronchiole – wrapped in connective tissue and receive arteriole, venule, and lymphatic vessel Microscopic Anatomy of Lobule of Lungs Alveoli ❑ Alveoli are like cup-shaped outpouching ❑ Have 2 types of alveolar epithelial cells ◼ Type I alveolar cells – responsible for gas exchange ◼ Type II alveolar cells – making surfactant which reduces the surface tension in the lungs keeping the alveoli from collapsing. These cells complete maturation at 7- month gestation. Important to know because in the case of premature babies. ❑ Alveolar macrophages – immune cells, take care of debris cleaning ❑ Alveolar circulation ◼ Incoming pulmonary artery → pulmonary capillaries wrap around the alveolus for gas exchange → outgoing pulmonary veins Breathing or ventilation is made of inhalation/inspiration (active) and exhalation/expiration (passive) Inhalation is active Diaphragm is the most important muscle of inhalation ◼ Flattens, lowering dome when contracted ◼ Responsible for 75% of air entering lungs during normal quiet breathing External intercostals ◼ Their contraction elevates ribs ◼ 25% of air entering lungs during normal quiet breathing ◼ When thorax expands, pressure drops in the pleural space, lung expand ◼ Air is pulled inside the lungs Exhalation is passive ❑ Muscles relax instead of contracting ◼ Based on elastic recoil of chest wall and lungs from elastic fibers and surface tension of alveolar fluid ◼ Diaphragm relaxes and become dome shaped ◼ External intercostals relax and ribs drop down ◼ Pressure in lungs increases, which expelling the air ❑ Exhalation only active during forceful breathing What happens if someone is trapped in a tunnel and CO2 builds up? How O2 and CO2 levels in tissue cells will look like if there in the case of arterial occlusion? Diffusion!  O2 in the lungs O2 O2 Alveolus O2 O2 air O2 O2 O2 O 2 O2 O O2 O2 O2 O O2 2 2 O2 O2 O2 O 2 O2 O2 O2 O O2 2 O2 O2 O2 O2 O2 O2 O 2 O2 O2 O2 O2 O2 O2 Blood O2 O 2 O2 Incoming blood Outgoing blood from the body to the body  O2 in the tissues Incoming blood Outgoing blood from the lungs to the lungs O2 O O O2 O2 Blood O2 2O2 2 O2 O2 O2 O2 O2 O2 O2 O2 O 2 O2 O2 O2 O2 O2 O2 O2 O 2 O2 O2 O2 O2 O2 O2 O2 O O2 O2 O2 2 O2 O2 O2 O2 O2 O2 Tissues O2 O2 O2  CO2 in the lungs Alveolus CO2 CO2 CO2 CO CO2 2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO CO2 CO 2 CO2 2 CO2 CO2 CO2 Blood CO2 Incoming blood Outgoing blood from the body to the body  CO2 in the tissues Incoming blood Outgoing blood from the lungs to the lungs CO2 Blood CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO 2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO CO2 CO2 2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 Tissues CO2 External respiration (lungs) and internal respiration (tissues) External/lung respiration ◼ Oxygen ❑ Oxygen diffuses from alveolar air (PO2 105 mmHg) into blood of pulmonary capillaries (PO2 40 mmHg) ❑ Diffusion continues until PO2 of pulmonary capillary blood matches PO2 of alveolar air ◼ Carbon dioxide ❑ Carbon dioxide diffuses from deoxygenated blood in pulmonary capillaries (PCO2 45 mmHg) into alveolar air (PCO2 40 mmHg) ❑ Continues until of PCO2 blood reaches 40 mmHg Internal/tissue respiration ◼ Oxygen ❑ Oxygen diffuses from systemic capillary blood into tissue cells – cells constantly use oxygen to make ATP ◼ Carbon dioxide ❑ Carbon dioxide diffuses from tissue cells into systemic capillaries – cells constantly make carbon dioxide ◼ At rest, only about 25% of the available oxygen is used Relationship between hemoglobin (Hb) and O2 partial pressure ❑ Hb is a 4 subunit protein that can carry O2 in each subunit. Hb is packed in red blood cells (RBCs). ❑ Higher the PO2, More O2 combines with Hb ❑ Fully saturated – completely converted to oxyhemoglobin ❑ Percent saturation expresses average saturation of hemoglobin with oxygen ❑ Oxygen-hemoglobin dissociation curve ◼ In pulmonary capillaries, O2 loads onto Hb ◼ In tissues, O2 is not held and unloaded ❑ 75% may still remain in deoxygenated blood (reserve) O2 - Hb dissociation curve How much O2 bound to Hb How much O2 around the Hb Hemoglobin and Oxygen Other factors affecting affinity of Hemoglobin for oxygen. Each makes sense if you keep in mind that metabolically active tissues need O2, and produce acids, CO2, and heat as wastes CO2 + H2O H2CO3 H+ - HCO3- In tissues In tissues 1- O2 is released from Hb to tissues 2- CO2 binds Hb 3- CO2 + H2O are converted by Carbonic anhydrase (CA) to carbonic acid (H2CO3) → this is called CO2 trap CO2 + H2O H2CO3 H+ - HCO3- In lungs In lungs 1- O2 binds Hb 2- CO2 is released from Hb – CO2 exhaled with air 3- H2CO3 is converted by Carbonic anhydrase (CA) to CO2 + H2O – CO2 exhaled with air Central chemoreceptors (CC) Respond to CO2 via H+ So, CC measure hydrogen, because hydrogen comes from carbonic acid, and carbonic acid comes from carbon dioxide. It is quite convoluted way of measuring carbon dioxide. CO2 + H2O H2CO3 H+ - HCO3- Central chemoreceptors (CC) Brain stem, in healthy individuals, regulate minute to minute respiration respond to H+ (any) H+ comes from H2CH3 (in the case of respiration) It can also come from any acid in our body If CO2 is high → H2CO3 gets elevated → H+ gets elevated → stimulates CC → increase respiratory rate RR which lowers CO2 which lowers H2CO3 which lowers H+ But if CO2 constantly elevated, CC get habituated stop working and peripheral chemoreceptors PC take over Peripheral chemoreceptors (PC) Respond to O2 !!!!!!!!!!! levels Peripheral chemoreceptors (PC) Located in aortic arch and carotid sinus → because internal carotid artery blood supplies the brain and aortic arch carries blood to the whole body. PC respond to O2 levels If O2 is low in blood → it stimulates PC → increase RR to bring more O2 If O2 is elevated in blood → it inhibit PC → decrease RR to bring less O2 up to stopping the respiration altogether.  Respiratory Acidosis (pH < 7.35) ◼ Respiratory: ❑ pCO2 increases → forms carbonic acid ❑ CO2 + H2O  H2CO3 (H+ - HCO3-) ❑ pCO2 > 50 mm Hg ❑ Low BP, vasodilation, flushed skin ❑ Why CO2 is elevated? ❑ Ventilation disorders ❑ Increased CO2 production (in fever, sepsis, burns, exercise) ❑ Air is high in CO2 ◼ The body will compensate ◼ Acidic urine because kidney get rid of H+ ◼ Other buffers in the body