Biology - Respiration
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- Higher vertebrates have developed respiratory systems whereby gas exchange occurs at a single place, known as
- The respiratory surface, the lungs
- How does air enter the respiratory tract?
- Through the external nares or nostrils
- After moving through the external nares and being filtered by mucous and nasal hairs, it passes through the pharynx and into a second chamber called what?
- The larynx
- Does ingested food also pass through the pharynx?
- Yes it does, en route to the esophagus
- What is the piece of tissue called that covers the glottis and what is the glottis?
- The glottis is the opening to the larynx, and the epiglottis covers it
- After passing through the larynx, where does air pass?
- Through the trachea
- What is the trachea primarily composed of?
- Cartilage
- How many branches does the trachea branch off to?
- They divide into two bronchi
- Where do they each go?
- One goes into the right lung and the other enters the left
- What ciliates both the trachea and bronchi?
- Epithelial cells
- What is their function?
- They filter and trap particles inhaled along with the air
- After the bronchi branch repeatedly into smaller bronchi, they reach the terminal branches which are called?
- Bronchioles
- What is each bronchiole surrounded by?
- Clusters of small air sacs called alveoli
- Where does gas exchange between the lungs and the circulatory system occur?
- Across the very thin walls of the alveoli
- What is each alveolus coated with?
- A layer of liquid containing surfactant
- And what is each alveolus surrounded by?
- An extensive network of capillaries
- What does surfactant do?
- It lowers the surface tension of the alveoli and facilitates gas exchange across the membranes
- How many alveoli provide 100 m2 of moist respiratory surface for gas exchange?
- There hundred million alveoli
- What is ventilation of the lungs?
- When air is inhaled and exhaled
- What is the purpose of ventilation?
- To take in oxygen from the environment and eliminate carbon dioxide from the body
- Pressure changes are dependent on the ventilating mechanism known as what?
- The thoracic cavity
- What is the thoracic cavity?
- The body cavity that contains the heart and lungs
- What is the thoracic cavity separated by from the abdominal cavity?
- A muscle known as the diaphragm
- Where is the diaphragm bounded to on its sides?
- By the chest wall
- What membranes are the lungs surrounded by?
- The visceral pleura and the parietal pleura
- What is the space between the two pleura known as?
- The intrapleural space
- What does it contain?
- A thin layer of fluid
- What is the pressure differential between the intrapleural space and the lungs responsible for?
- It prevents the lungs from collapsing
- During inhalation, when the diaphragm contract and flattens, what muscles contract?
- The external intercostals muscles
- What do they do?
- They push the rib cage and chest wall up and out
- What does this cause?
- It causes the rib cage to move down
- What does this volume increase cause?
- A reduction in the intrapleural pressure
- What is this referred to as?
- Negative-pressure breathing
- Is exhalation an active or passive process?
- A passive process
- When the diaphragm and external intercostals muscles relax causing the chest wall to push inward, is there an increase or decrease in thoracic cavity volume?
- A decrease
- What does this do?
- It causes the lungs to deflate, forcing air out of the alveoli
- During forced exhalation what muscles contract?
- The internal intercostals muscles
- What does surfactant reduce?
- The high surface tension of the fluid lining the alveoli, preventing collapse during exhalation
- Where are the neurons located that regulate ventilation?
- In the medulla oblongata
- How do they regulate ventilation?
- They rhythmically discharge stimulating the intercostals muscles and or the diaphragm to contract
- How can these neural signals be modified?
- By chemoreceptors in the aorta
- Why do the signals change?
- The signals change in order to respond to changes in the pH and the partial pressure of CO2 in the blood
- When the partial pressure of CO2 rises, does the medulla oblongata stimulate a decrease or increase in the rate of ventilation?
- An increase
- Can ventilation be controlled at all by the cerebrum?
- To some extent
- What is the purpose of hyperventilation?
- It lowers the partial pressure of CO2 in the blood below normal
- In response to this, what do chemoreceptors do?
- They sense it and send signals to the respiratory center which temporarily inhibits breathing
- What does a spirometer do?
- It measures the amount of air normally present in the respiratory system and the rate at which ventilation occurs
- What is the vital capacity?
- It is the maximum amount of air that can be forcibly inhaled and exhaled from the lungs
- What is the amount of air normally inhaled and exhaled with each breath called?
- Tidal volume
- What is the residual volume?
- The air that always remains in the lungs, preventing the alveoli from collapsing
- What is the volume of air that can be forcibly exhaled following a normal exhalation?
- The expiratory reserve volume
- What is total lung capacity?
- It is equal to the vital capacity plus the residual volume
- What is the dense network of minute blood vessels called that surrounds the alveoli?
- The pulmonary capillaries
- How does gas exchange occur across these capillary walls and the alveoli?
- By diffusion
- When blood enters the pulmonary capillaries, is it in an oxygenated or deoxygenated state?
- It is in a deoxygenated state
- What does this imply?
- It implies that it has a lower partial pressure of O2 than does the inhaled air in the alveoli
- Once O2 diffuses down its gradient into the capillaries where it binds to hemoglobin, what does it do next?
- It returns to the heart via the pulmonary veins
- Is the partial pressure of CO2 in the capillaries greater to that of the inhaled alveolar air or smaller?
- It is greater
- What does imply?
- It implies that CO2 will diffuse from greater concentration to smaller concentration from the capillaries into the alveoli, where it is released into the external environment during exhalation
- What happens at high altitudes?
- The partial pressure of O2 in the atmosphere declines, making it more difficult to get sufficient oxygen to diffuse into the capillaries
- What does the body do to compensate?
- It increases the rate of ventilation and also increases the production of red blood cells to carry more oxygen
- What happens to the affinity of hemoglobin for oxygen?
- It decreases to facilitate unloading of oxygen in tissues
- Does active transport facilitate gas exchange in the lungs at any point?
- No
- The intrapleural space in the lungs is bounded by what?
- The visceral pleura and the parietal pleura
- The lungs can collapse from what?
- It can collapse from insufficient surfactant production and a rupture of the parietal pleura