Respiration PDF Study Notes

8/27/24, 6:13 PM Platform | Study Fetch The Respiratory System: Structure and Function The Human Lungs and Air Pathway (00:00:38 - 00:01:47) The respiratory system regulates the exchange of oxygen and carbon dioxide between...

8/27/24, 6:13 PM Platform | Study Fetch The Respiratory System: Structure and Function The Human Lungs and Air Pathway (00:00:38 - 00:01:47) The respiratory system regulates the exchange of oxygen and carbon dioxide between tissues and the outside environment. The upper respiratory tract includes the nasal cavity, pharynx, and larynx. The lower respiratory tract includes the trachea, bronchi, bronchioles, and alveoli. The air pathway is as follows: Nasal cavity -> Pharynx -> Larynx -> Trachea -> Bronchi -> Bronchioles -> Alveoli The alveoli are the site of gas exchange with the blood. The Pleura (00:01:47 - 00:02:37) The pleura are the layers that surround the lungs. The pleura provide a smooth, lubricated surface for the lungs to move over during expansion and contraction. The two layers of the pleura are: Visceral pleura (inner layer) Parietal pleura (outer layer) The Diaphragm (00:02:37 - 00:03:30) The diaphragm is the main respiratory muscle responsible for inspiration and expiration. The diaphragm contracts during inspiration, creating negative pressure in the chest cavity and pulling air in. The diaphragm relaxes during expiration, allowing air to leave the lungs. The phrenic nerve innervates the diaphragm, originating from C3-C5 in the spine. Inspiration vs. Expiration (00:03:42 - 00:04:17) Inspiration: The diaphragm contracts and pulls downward, creating negative pressure in the chest cavity and pulling air in. Expiration: The diaphragm relaxes, allowing the air to leave the lungs. Accessory muscles, such as the intercostal muscles, can also be used to force more air out. Accessory Respiratory Muscles (00:04:17 - 00:04:31) In addition to the diaphragm, there are accessory respiratory muscles, such as the intercostal muscles, that can be used to assist with breathing, especially during more strenuous activities. https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cd4f069b6d6b89c5eb6/document?go=note 1/7 8/27/24, 6:13 PM Platform | Study Fetch Respiratory Muscles and Breathing Mechanics (00:04:48 - 00:05:08) The intercostal muscles are located between the ribs There are internal and external intercostal muscles These accessory muscles can be used by people with conditions like asthma to help with breathing (00:05:08 - 00:05:24) Mnemonic to remember the roles of the intercostal muscles: External intercostals do not belong to the "other" (expire) Internal intercostals do not "inspire", they expire (00:05:24 - 00:05:35) Understanding the roles of the intercostal muscles is important and high-yield for exams Lung Volumes and Capacities (00:05:35 - 00:06:04) Quiet Breathing: Tidal volume - the amount of air flowing in and out during normal breathing Allows for passive gas exchange Deeper Breathing: Inspiratory reserve volume - the maximum amount of air that can be inhaled beyond the tidal volume Inspiratory Capacity: The sum of tidal volume and inspiratory reserve volume (00:06:04 - 00:06:21) Expiratory Reserve Volume: The maximum amount of air that can be exhaled beyond the tidal volume Vital Capacity: The sum of tidal volume, inspiratory reserve volume, and expiratory reserve volume Represents the full capacity of the lungs (00:06:21 - 00:06:36) Residual Volume: The amount of air that cannot be exhaled, even with maximum effort Total Lung Capacity: The sum of vital capacity and residual volume (00:06:36 - 00:07:03) Measuring Lung Volumes: Vital capacity can be easily measured with spirometry Residual volume is more difficult to measure, often estimated https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cd4f069b6d6b89c5eb6/document?go=note 2/7 8/27/24, 6:13 PM Platform | Study Fetch (00:07:03 - 00:07:32) Functional Residual Capacity: The sum of expiratory reserve volume and residual volume Represents the amount of air left in the lungs at the end of a quiet breath (00:07:32 - 00:08:20) Measuring Vital Capacity: Involves having the patient take a deep breath and then exhale as much as possible Provides information about lung function (00:08:20 - 00:08:37) Measuring lung volumes and capacities can provide valuable insights into a person's respiratory health Gas Exchange and Hemoglobin Gas Exchange (00:08:37 - 00:09:06) Gas exchange is the result of partial pressure differences between oxygen and carbon dioxide Carbon dioxide is at a relatively high concentration in the blood and low concentration in inhaled air Oxygen is at a high pressure in inhaled air and low pressure in the blood This pressure difference drives the exchange of gases across the capillary membrane Air Movement and Surfactant (00:09:06 - 00:09:46) Type II pneumocytes secrete surfactant, which prevents the alveoli from collapsing As alveoli get smaller, the tendency to collapse increases Surfactant reduces surface tension and keeps the alveoli open Premature babies may have issues with surfactant production, requiring clinical intervention Gas Exchange Anatomy (00:09:46 - 00:10:45) Type I pneumocytes are where gas exchange takes place, covering the largest surface area of the alveoli Air flows in and out of the alveoli, with gas exchange occurring across the pneumocytes and endothelial cells Red blood cells carry hemoglobin, which binds oxygen Hemoglobin and Oxygen Binding (00:10:45 - 00:11:31) https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cd4f069b6d6b89c5eb6/document?go=note 3/7 8/27/24, 6:13 PM Platform | Study Fetch Hemoglobin is made up of porphyrin rings with iron atoms in the center, allowing it to bind oxygen The structure of hemoglobin, with four chains and heme groups, facilitates oxygen transport Oxygen Dissociation Curve (00:11:31 - 00:12:27) The oxygen dissociation curve shows how oxygen binds to hemoglobin Factors that shift the curve include: Increased acidity (lower pH) from lactic acid production during exercise Increased carbon dioxide levels Decreased temperature Lactic Acid and Oxygen Delivery (00:12:27 - 00:12:58) During exercise, muscles use glycolysis to generate ATP, producing lactic acid The acidic environment created by lactic acid shifts the oxygen dissociation curve, allowing more oxygen to be unloaded to the tissues The Oxygen Dissociation Curve and Factors that Shift It (00:12:58 - 00:13:09) CO2 from metabolism will cause the acidification of the local environment CO2 turns into a proton and bicarbonate, increasing the local acidity (00:13:09 - 00:13:21) In the lungs, the oxygen partial pressure is typically around 100-110 mmHg At a pH of 7.4, hemoglobin saturation is high (around 98%) (00:13:33 - 00:13:48) As oxygen partial pressure drops in the tissues, hemoglobin oxygen saturation falls For example, at 20% oxygen partial pressure, hemoglobin saturation may drop to around 40% (00:13:48 - 00:14:31) In the case of acidosis (e.g., from diabetes, lactic acidosis, or hypercapnia), the oxygen dissociation curve shifts to the right This means that at a given oxygen partial pressure, hemoglobin will unload more oxygen to the tissues For example, at a pH of 7.0, hemoglobin saturation may drop to around 10% at 20% oxygen partial pressure (00:14:31 - 00:14:50) The right shift of the oxygen dissociation curve in acidosis allows for greater oxygen unloading to metabolically active tissues (00:15:03 - 00:15:20) https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cd4f069b6d6b89c5eb6/document?go=note 4/7 8/27/24, 6:13 PM Platform | Study Fetch In a highly acidic environment, the oxygen dissociation curve shifts to the right, allowing for more oxygen unloading Conversely, in alkalosis, the curve shifts to the left, making it harder to unload oxygen to tissues (00:15:20 - 00:15:32) Alkalosis can be caused by hypercapnia (loss of buffer bicarbonate) or contraction alkalosis (00:15:32 - 00:15:51) Changes in H+ ion concentration can shift the oxygen dissociation curve by directly interacting with hemoglobin (00:15:51 - 00:16:06) Left shift of the curve means hemoglobin is tightly bound to oxygen, making it harder to release Right shift means hemoglobin is loosely bound, making it easier to release oxygen to tissues Factors that Shift the Oxygen Dissociation Curve: Shift Right (Increase Oxygen Unloading) Shift Left (Decrease Oxygen Unloading) Carbon dioxide Decreasing carbon dioxide Acidity (H+ ions) Decreasing acidity (H+ ions) Diphosphoglycerate (2,3-BPG) Decreasing 2,3-BPG Exercise Decreasing exercise Temperature Decreasing temperature (00:16:46 - 00:16:59) 2,3-Bisphosphoglycerate (2,3-BPG) is a substance produced by red blood cells in hypoxic environments that shifts the curve to the right (00:17:09 - 00:17:33) When ascending to high altitudes, the body produces more red blood cells and 2,3-BPG, shifting the oxygen dissociation curve to the right to facilitate oxygen unloading in the tissues. Chronic Hypoxia and Oxygen Delivery (00:17:33 - 00:17:46) This allows for a more chronic way to unload more oxygen to tissues When you're not inhaling as much oxygen, your tissues become chronically hypoxic throughout your body This is a way for your red blood cells to dump more oxygen without being in an acidotic environment (00:17:46 - 00:18:00) You're just kind of chronically hypoxic This is one of the top situations that can modify the oxygen binding curve of 2,3-bisphosphoglycerate (2,3- BPG) https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cd4f069b6d6b89c5eb6/document?go=note 5/7 8/27/24, 6:13 PM Platform | Study Fetch Bicarbonate Buffering System (00:18:00 - 00:18:15) The bicarbonate buffering system is very important to understand It's a high-yield topic (00:18:15 - 00:18:41) When you breathe in, you take in oxygen When you breathe out, you exhale CO2 Most of the CO2 in your body combines with water to form carbonic acid in the blood (00:18:41 - 00:18:52) The carbonic acid then dissociates into H+ and bicarbonate ions The bicarbonate ions serve as a supply to soak up excess hydrogen ions in the blood (00:19:03 - 00:19:26) If you become acidotic, for example, due to lactic acidosis from an infection, the bicarbonate will start to soak up those extra H+ ions (00:19:26 - 00:19:46) When the H+ combines with the bicarbonate, it can then be exhaled as CO2, which is a rapid way for the body to get rid of excess acid (00:19:46 - 00:20:01) There are other ways the kidneys can reuptake bicarbonate and excrete acid in the urine, but we won't go into those details Countercurrent Exchange in Fish Gills (00:20:14 - 00:20:28) Countercurrent exchange allows more oxygen to enter the blood It's a system where two fluids flow past each other in opposite directions, greatly increasing diffusion across the membrane (00:20:28 - 00:20:40) Countercurrent exchange happens in several places in the human body In fish, it occurs in their gills to absorb oxygen from the water (00:20:40 - 00:20:56) Fish rely on this countercurrent exchange for respiration Instead of lungs and alveoli, they have gills with blood vessels and structures called lamellae (00:21:15 - 00:21:27) The water flows over the lamellae, creating a countercurrent exchange This allows for rapid diffusion of oxygen into the fish and CO2 out of the fish (00:21:27 - 00:21:37) The countercurrent exchange in fish gills is a very similar system to the alveoli in human lungs But it has a more flow-based system due to the water environment (00:21:37 - 00:21:48) You can think of the fish gills as being similar to alveoli, but with a more flow-based system https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cd4f069b6d6b89c5eb6/document?go=note 6/7 8/27/24, 6:13 PM Platform | Study Fetch https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cd4f069b6d6b89c5eb6/document?go=note 7/7