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Front
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Back
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- The exchange of O2 from environment for CO2 from body's cells
- Inhalation/inspiration: The process of taking air into the lungs
- Exhalation/expiration: The process of breathing air out of the lungs
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Photosynthesis: 6 CO 2 + 6 H 2O --> C 6H 12O 6 + 6 O 2
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- Cellular respiration: Production of ATP by oxidation of carbohydrates, amino acids, or fatty acids; oxygen is consumed, & carbon dioxide is produced
- Energy stays in the cell & is used to build, repair, & reproduce cells
- CO2 is released into the bloodstream as waste & carried to lungs to be released
- Water - Most is released as waste but some stays in cell
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- CO2 is produced when carbon is combined w/ oxygen while making ATP (energy) in the mitochondria
- CO2 is transported from your mitochondria out of your cell, to your red blood cells, & back to your lungs to be exhaled
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Why Do We Need to Get Rid of CO2?
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- Normal blood pH is tightly regulated between 7.35 & 7.45
- CO2 dissolves in the blood plasma, making the plasma more acidic
- Excess CO2 must be removed from the body to stop it from reaching toxic levels
- Hypercapnia: Higher than normal CO2 in environment or blood can cause acidosis
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Overview
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- Unicellular & small multicellular organisms rely on diffusion for gas exchange
- Larger organisms combine diffusion & bulk flow for gas exchange
- Bulk flow - Movement of molecules from area of high pressure to area of low pressure
- Used in circulation - Transport of gases in the circulatory system
- Used in ventilation - Moving air or water over lungs or gills
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- Large, lobed, paired organs in the chest (thoracic cavity)
- Thin sheets of epithelium (pleura) separate inside of chest cavity from outer surface of the lungs
- The bottom of the thoracic cavity is formed by the diaphragm
- Bronchi are reinforced to prevent their collapse & are lined w/ ciliated epithelium & mucus-producing cells
- Bronchi branch into smaller & smaller tubes known as bronchioles
- Bronchioles terminate in grape-like sac clusters known as alveoli
- Alveoli are surrounded by a network of thin-walled capillaries. Only about 0.2 μm separate the alveoli from the capillaries due to the extremely thin walls of both structures
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Pleural Sac
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- Each lung is surrounded by a pleural sac
- 2 layers of cells w/ small space between them (pleural cavity)
- Pleural cavity contains a small volume of pleural fluid
- Intrapleural pressure is subatmospheric, which keeps lung expanded
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- Separates the chest from the abdomen; plays a lead role in breathing
- When we breathe in, the diaphragm moves downward toward the abdomen & the rib muscles pull the ribs upward & outward, enlarging the chest cavity & pulling air in through the nose or mouth
- When we breathe out, the diaphragm moves upward, forcing the chest cavity to get smaller & pushing the gases in the lungs up & out of the nose & mouth
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Mammals: 2 Main Parts to Respiratory System
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- Upper respiratory tract: Mouth, nasal cavity, pharynx, trachea
- Nasal passage
- Oral cavity
- Pharynx --> Cavity behind nose & mouth, connecting them to esophagus
- Larynx
- Trachea --> Large tube from larynx to bronchial tubes; moves air to & from the lungs (windpipe)
- Lower respiratory tract
- Bronchi, lungs, heart, ribs
- Bronchi & gas exchange surfaces (alveoli)
- Alveoli are the site of gas exchange
- Thin wall of type I alveolar cells
- Type II surfactant cells secrete fluid
- Outer surface of alveoli are covered in capillaries
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- Bronchi are reinforced to prevent their collapse & are lined w/ ciliated epithelium & mucus-producing cells
- Bronchi branch into smaller & smaller tubes known as bronchioles
- Bronchioles terminate in grape-like sac clusters known as alveoli
- Alveoli are surrounded by a network of thin-walled capillaries. Only about 0.2 μm separate the alveoli from the capillaries due to the extremely thin walls of both structures
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- Exchange of O2 & CO2 takes place at capillary level around alveoli
- Because O2 levels in alveoli are high, O2 diffuses across the alveolar & capillary walls into the blood where O2 concentration is low
- The same thing occurs with CO2 but in the opposite direction
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Metalloproteins (Respiratory Pigments)
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- Proteins containing metal ions that reversibly bind to & increase O2-carrying capacity by 50-fold
- 3 major types:
- Hemocyanins: Present in arthropods & molluscs; contains copper
- Hemerythrins: Present in some annelids & contains iron directly bound to protein
- Hemoglobins (most common):
- Present in vertebrates, nematodes, some annelids, crustaceans, & insects
- The protein globin is bound to a heme molecule that contains iron
- Usually located within blood cells
- Appears red when oxygenated
- Myoglobin is a type of hemoglobin found in muscles
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- Each of us has hundreds of millions of alveoli in our lungs. The alveoli are where the exchange of O2 & CO2 takes place
- With each inhalation, air fills a large portion of the millions of alveoli
- Through diffusion, O2 moves from the alveoli to the blood through the capillaries
- Once in the bloodstream, O2 is bound by hemoglobin found in red blood cells
- This O2-rich blood then flows back to the heart, which pumps it through the arteries to tissues throughout the body
- In the tiny capillaries of the body tissues, O2 is freed from the hemoglobin & moves into the cells
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- CO2 is produced as waste by a cell & moves out of these cells into the capillaries, where most of it is dissolved in the plasma of the blood
- Most CO2 is taken up by red blood cells where it is
- Bound by hemoglobin
- In an environment where there is a lot of CO2 in comparison to O2, the CO2 tends to displace any O2 attached to hemoglobin, and vice versa
- Converted into bicarbonate (HCO3-)
- Most of CO2 in blood is found in this form
- Blood rich in CO2 then returns to the heart via the veins
- From the heart, this blood is pumped to the lungs, where CO2 passes into the alveoli to be exhaled
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