Respiratory System

Breathing External Respiration Internal Respiration 4 PROCESSES Breathing External Respiration Internal Respiration Cellular Respiration

Trachea epiglottis thyroid cartilage vocal cord tracheal cartilages

The Trachea lumen posterior anterior esophagus hyaline cartilage ring Mucus membrane submucosa adventitia anterior

The Trachea

Vocal Cords True vocal cords are inferior to false vocal cords Sound is produced when expelled air is passing through the larynx over the vocal cords

Epithelial Lining of the Trachea mucus cilia

Lungs

Alveoli

Alveoli

Alveoli alveolar macrophage type I alveolar cell type II alveolar cell (surfactant secreting cell) pulmonary capillaries CO2

Erythrocytes Function- transport respiratory gases Lack mitochondria. Why?

Hemoglobin Structure Hemoglobin- quaternary structure 2  chains and 2  chains Hemoglobin Structure 1 RBC contains 250 million hemoglobin molecules

Uptake of Oxygen by Hemoglobin in the Lungs O2 binds to hemoglobin to form oxyhemoglobin High Concentration of O2 in Blood Plasma High pH of the Blood Plasma oxyhemoglobin O2

O2 pickup CO2 release

Unloading of Oxygen from Hemoglobin in the Tissues When O2 is releaseddeoxyhemoglobin Low Concentration of O2 in Blood Plasma Lower pH of the Blood Plasma

O2 release CO2 pickup

Carbon Dioxide Chemistry in the Blood CO2 + H2O  H2CO3  HCO3- + H+ carbonic acid bicarbonate ion

Transport of Carbon Dioxide from the Tissues to the Lungs 60-70% as bicarbonate dissolved in the plasma (slow reaction) 7-10% dissolved in the plasma as CO2 20-30% bound to hemoglobin as HbCO2 CO2 + hemoglobin  HbCO2

Mechanics of Breathing 2 muscles involved with breathing: external intercostal muscles diaphragm Breathing controlled by: phrenic nerve from medulla pons

Mechanics of Breathing

Lung Ventilation Negative pressure draws air in Inspiration 760 mm Hg

Lung Ventilation Positive pressure forces air out 768 mm Hg Expiration

Lung Volumes Tidal Volume- 500 ml Vital Capacity- 4800 ml Residual Volume- 1000-1200ml Total Lung Capacity- 4400-6400ml IRV- 2800 ml ERV- 1000-1200ml Dead Space- 150 ml What factors affect lung volume?

Regulation of Breathing medulla oblongata pons phrenic CO2 and H+ triggers breathing reflex in medulla, not presence of O2 vegas

Restrictive vs Obstructive Air Flow Restrictive- more diff. to get air in to lungs Loss of lung tissue Decrease in lungs ability to expand Decrease in ability to transfer O2 and CO2 in blood Diseases: Fibrosis, sarcoidosis, muscular disease, chest wall injury, pneumonia, lung cancer, pregnancy, obesity

Restrictive vs Obstructive Air Flow Obstructive- more diff. to get air out of lungs Airway narrows Increase in time it takes to empty lungs Diseases: Emphysema, chronic bronchitis, asthma

Normal lung Smoker’s lung Lung cancer

Mammalian Dive Reflex Heart rate slows Blood flow to extremities constricted Blood and water allowed to pass through organs and circulatory walls to chest cavity. The first two items begin to happen as soon as the face hits cold water. The slowing heart rate is almost instantaneous, the constricted blood flow happens more gradually. Both responses are more extreme with more extreme temperatures. The slowed heart rate is generally a useful feature as it actively serves to conserve oxygen depletion and increase the available time underwater without dramatically harming performance. Yeah! You’re holding your breath, so obviously there are limits to the effectiveness! The decreased blood flow provides more of a long-term (minutes-hours) survival benefit, but is detrimental to performance. If you were diving for food, you’d quickly find that your limbs turn into numb rocks in cold water. The third response is a bit more scary. Essentially, the body intentionally allows fluid to fill the lungs and chest cavity to prevent organs from being crushed from extreme pressure. For surface dwelling mammals, this serves a survival function. It only kicks in as depths become extreme. Mammalian Dive Reflex First observed in sea mammals, this reflex (MDR) is effectively what allows freedivers to do what they do. It wasn't until the 1950's that this reflex was shown to be possessed by people and not just whales, seals and our cretacious cousins, the dolphins. Prior to this discovery and even in the era of Jaques Mayol, scientists thought it was impossible for a freediver to dive much over 40m without being killed. The MDR consists of a number of immediate physiological changes: bradycardia (the slowing of the heart), splenic contraction and blood shift. a) Bradycardia (slowing of the heart) Because the heart, as the biggest muscle in the body, uses oxygen every time it beats, the slower it beats, the less oxygen it uses, allowing the diver to stay underwater for extended periods. b) Splenic contraction Water pressure squeezes the spleen, reducing its size by up to 20%. This effectively squeezes blood rich in red blood-cells into the circulatory system, increasing hemoglobin concentration by up to 10%. c) Blood shift Blood shift, or "blood shunt", is a movement of blood from the peripheral areas such as the limbs, to the core areas of heart, lungs and brain. It is caused through peripheral vasoconstriction of skin vessels, as well as big intra-thoracic vessels. For these organs, oxygen is an obvious priority. So by this redistribution of blood, and therefore oxygen, from the nonessential areas to those areas involved in maintaining consciousness, the freediver is able to stay conscious longer. Another advantage offered by blood shift is that, because there is less blood flowing to the legs, when they are used during fining they are forced to work primarily anaerobically and therefore use less oxygen than they otherwise would. Blood shift also allows divers do dive well beyond residual volume (30-40m) without suffering "lung squeeze" as the lungs pool with blood, thereby mitigating the increasing vacuum effect caused by ribs inability to flex inwards and the diaphragm to move up as the pressure differential between the air in the lungs and the surrounding water increase. Blood does not actually enter the lungs air space. Rather it is the capillaries that intrude into the lungs' airspace and expand as they become engorged with blood. This is termed "pulmonary erection". Only if negative pressure becomes extreme will plasma and then even blood (pulmonary edema) enter the airspace and be coughed up. Martin Stepanek, during static apnea alone, is said to have such a strong blood shift that his legs and arms go visibly white and his torso red. This shows that although blood shift is usually triggered by pressure, it is also triggered by the "breath-hold reflex", the two reflexes being inextricably linked. The degree of dive reflex: It varies from person to person. Fortunately it is trainable to a large degree. The more often you dive, the more accustomed the body gets to engage the various mechanisms involved. It's almost as if the brain, knowing what is about to happen next, can quicker and more effectively trigger the necessary physiological chances. A simple static then becomes enough to trigger the entire MDR. Facial immersion: Apart from increased ambient hydrostatic pressure and breath-holding, the other very important trigger of the MDR is facial immersion in water. Dr Erica Schagatay found that the main trigger was cold water, colder the better. She also managed to show that the areas which needed to be exposed to the cold water were on the face, specifically nerves around the eyes and upper lip. This is the reason behind doing a warm-up static face down and without a mask before a big dive, and if there is a thermocline available, a static bellow the thermocline without a mask. It's also the reason why many freedivers prefer wearing goggles over masks during statics.

Hyperventilation Short term, rapid, deep breathing beyond the need for the activity Lowers the level of CO2 in blood Short term, rapid, deep breathing beyond the need for the activity Lowers the level of CO2 in blood (hypocapnia or hypocarbia)

Shallow Water Blackout

INQUIRY Identify the lipoprotein molecule that reduces surface tension within the alveoli so they do not collapse during exhalation. Even after the most forceful exhalation, a certain volume of air remains in the lungs. What is the volume of air called? Describe the physical structure of alveoli. What structures warm and moisten incoming air? What body cavity are the lungs located? What tissue lines the lungs? What stimulates the breathing response? Calculate total lung capacity given: RV= 1000, TV = 500, ERV = 1100, IRV = 2500, VC= 4100