1. In a 300-words, compare the upper and lower respiratory tract in terms of structure and function. AND comment/ elaborate on the following sentence, “Both internal and external respiration depends on diffusion,” by using the terms: alveoli, oxygen, C02, capillaries …

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Comparison of the Upper and Lower Respiratory Tract

The respiratory tract is divided into the upper and lower respiratory systems, each with distinct structures and functions.

The upper respiratory tract includes the nose, nasal cavity, sinuses, pharynx, and larynx. Structurally, it is lined with mucous membranes and cilia that help filter, warm, and humidify the incoming air. The nasal cavity plays a crucial role in trapping dust and pathogens through mucus and cilia. The pharynx serves as a passageway for both air and food, while the larynx (voice box) contains the vocal cords, enabling speech production.

The lower respiratory tract consists of the trachea, bronchi, bronchioles, and lungs. The trachea (windpipe) is a rigid tube reinforced by cartilage rings to prevent collapse, ensuring continuous airflow. It branches into the bronchi, which further divide into bronchioles, ultimately leading to the alveoli—tiny air sacs where gas exchange occurs. Unlike the upper tract, the lower tract is primarily responsible for delivering oxygen to the bloodstream and expelling carbon dioxide.

Elaboration on Respiration and Diffusion

Respiration relies on diffusion, the passive movement of gases from high to low concentration. External respiration occurs in the alveoli, where oxygen (O₂) diffuses from the alveolar air into the surrounding capillaries, while carbon dioxide (CO₂) moves from the capillaries into the alveoli to be exhaled. Internal respiration happens at the tissue level, where O₂ diffuses from capillaries into body cells, and CO₂ moves from cells into the blood for removal.

Since diffusion does not require energy, the process is highly dependent on the concentration gradient between the alveoli and blood. Any impairment in alveolar function (e.g., fluid buildup in pneumonia) can hinder this process, leading to poor oxygenation.