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Biology - Gas Exchange

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    Study Guide Biology – Gas Exchange 1. Human Respiratory System The human respiratory system is responsible for bringing oxygen into the body and removing carbon dioxide. Oxygen is essential for releasing energy in our cells, while carbon dioxide is a waste gas that must be removed. This system is made up of several organs that work together smoothly. The main parts include the nose, pharynx, trachea, and lungs . Let’s follow the path of air and see what each part does. 1.1 Nose: Where Air Enters and Gets Prepared Breathing begins at the nose . • As air enters, it is warmed and moistened , making it safer for the lungs. • Inside the nose, bony partitions divide the nasal cavity into chambers. • Air swirls through these chambers, which helps trap dust. • Nose hairs and tiny hairlike structures called cilia catch dust and other particles, cleaning the air before it moves deeper into the body. This process helps protect the lungs from damage. 1.2 Pharynx: The Shared Airway From the nose, air moves into the pharynx , also known as the throat. • The pharynx is located at the back of the mouth. • Two Eustachian tubes open from the pharynx to the middle ear. Their job is to equalize air pressure on both sides of the eardrum. • The pharynx also contains tonsils and adenoids , which are made of lymphatic tissue. • These structures help trap and filter microorganisms , supporting the immune system.

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    Study Guide 1.3 Trachea: The Windpipe After the pharynx, air enters the trachea , or windpipe. • The trachea is supported by 16 – 20 C - shaped rings of cartilage . • These cartilage rings keep the airway open at all times , even when you bend or move your neck. • The open part of the “C” faces the esophagus, allowing room for swallowing. 1.3.1 Protecting the Airway • The opening of the trachea is called the glottis . • A flap of tissue called the epiglottis covers the glottis during swallowing. • This prevents food from entering the trachea and causing choking. 1.3.2 Voice Production • At the top of the trachea is the larynx , or voice box. • Inside the larynx are vocal cords . • When you exhale, air passes over the vocal cords, causing them to vibrate and produce sound. 1.4 Bronchi, Bronchioles, and Alveoli: The Airway Tree At its lower end, the trachea splits into two large tubes called bronchi (one leading to each lung). • The bronchi also contain cartilage and smooth muscle. • Each bronchus branches into smaller tubes called bronchioles . • Together, these branches form a bronchial tree . • The bronchioles end in tiny air sacs called alveoli .

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    Study Guide 1.5 Lungs: Gas Exchange Happens Here The lungs contain about 300 million alveoli . • Each alveolus is surrounded by tiny blood vessels called capillaries . • Red blood cells move through these capillaries in single file . • Oxygen from the air in the alveoli diffuses into the blood and binds to hemoglobin in red blood cells. • At the same time, carbon dioxide leaves the blood and enters the alveoli. Most carbon dioxide reaches the alveoli as bicarbonate ions , while about 25% is loosely bound to hemoglobin . 1.6 Breathing In and Out 1.6.1 Inhalation (Breathing In) • The rib muscles and diaphragm contract . • This increases the volume of the chest cavity . • As volume increases, air pressure inside the chest decreases . • Air rushes into the lungs, and the alveoli expand and fill with air. This process happens passively , meaning the lungs themselves do not pull air in. 1.6.2 Exhalation (Breathing Out) • The rib muscles and diaphragm relax . • The chest cavity becomes smaller. • Air pressure inside increases. • The alveoli shrink, and air is pushed out of the lungs.

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    Study Guide 1.7 Control of Breathing Breathing is controlled by nerve impulses sent to the rib muscles and diaphragm. • These impulses are influenced by the level of carbon dioxide in the blood . • When carbon dioxide levels rise, the brain sends more nerve signals . • This causes breathing to become faster and deeper , helping remove excess carbon dioxide. 2. Quiz Human Respiratory System 1. Question Fill in the blank: Which of the following is the correct pathway through which air travels in the human respiratory system? Answer Choices • nose, lungs, pharynx, trachea • nose, pharynx, trachea, lungs • pharynx, nose, trachea, lungs Correct Answer nose, pharynx, trachea, lungs Why This Is Correct Air enters the body through the nose , then passes through the pharynx , continues down the trachea , and finally reaches the lungs , where gas exchange occurs. The other options list the structures in an incorrect anatomical order. Therefore, the correct pathway is nose → pharynx → trachea → lungs .

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    Study Guide 2. Question Fill in the blank: Which of the following is responsible for preventing food from entering the trachea? Answer Choices • epiglottis • glottis • larynx Correct Answer epiglottis Why This Is Correct The epiglottis is a flap of cartilage that folds down over the opening of the trachea during swallowing. This action prevents food and liquid from entering the airway and directs them into the esophagus. For comparison: • The glottis is the opening between the vocal cords. • The larynx (voice box) is involved in sound production and airway protection but does not directly block food. Therefore, the epiglottis is responsible for preventing food from entering the trachea. 3. Question Fill in the blank: Which of the following correctly describes the method of inhalation? Answer Choices • rib muscles and diaphragm contract, volume in chest cavity decreases, air pressure increases • rib muscles and diaphragm contract, volume of chest cavity increases, air pressure decreases • rib muscles and diaphragm relax, volume of chest cavity increases, air pressure decreases

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