Lesson Notes By Weeks and Term v5 - Grade 11

Lesson Video

This page supports the lesson note with a companion video and a short classroom-ready summary.

For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.

Performance objectives

• Describe the structure and function of the respiratory system.
• Explain gas exchange in the lungs and tissues.
• Describe the structure and function of the excretory system.
• Explain how urine is formed in the nephron.
• Relate common diseases of these systems to their causes and prevention.

Lesson summary

This week, we delve into the vital processes of human respiration and excretion. Understanding these systems is crucial for appreciating how our bodies function, maintain homeostasis, and stay healthy. Think about the air pollution in many South African cities or the impact of water scarcity on kidney health. Respiration provides the energy our bodies need to perform all activities, from running a marathon to thinking in class. Excretion removes harmful waste products that could poison us if they accumulated. These processes are directly affected by environmental factors, lifestyle choices, and access to resources, all of which are pertinent issues in South Africa.

Lesson notes

2.1 Human Respiration What is Respiration? Respiration is the process by which living organisms obtain energy from food. In humans, this involves both breathing (ventilation) and cellular respiration. Breathing is simply the movement of air into and out of the lungs, while cellular respiration is the chemical process that occurs within cells to release energy from glucose. We're focusing on the mechanics and structures involved in breathing this week.

The Respiratory System: Nasal Cavity: Air enters through the nose or mouth. The nasal cavity filters, warms, and moistens the air. Tiny hairs called cilia and mucus trap dust and other particles. Imagine the dust kicked up on a construction site; this is what your nasal cavity protects you from.

Pharynx (Throat): A passageway for both air and food.

Larynx (Voice Box): Contains the vocal cords, which vibrate to produce sound.

Trachea (Windpipe): A tube reinforced with rings of cartilage to prevent it from collapsing. The cartilage rings are C-shaped, with the open part at the back, allowing the esophagus (food pipe) to expand when swallowing.

Bronchi: The trachea divides into two bronchi, one entering each lung.

Bronchioles: Inside the lungs, the bronchi branch repeatedly into smaller and smaller tubes called bronchioles.

Alveoli: Tiny air sacs at the end of the bronchioles. This is where gas exchange occurs. The alveoli are surrounded by a network of capillaries (tiny blood vessels). The lungs contain millions of alveoli, providing a large surface area for efficient gas exchange. Think of it like a sponge – lots of surface area packed into a small space.

Lungs: The main organs of respiration. They are located in the chest cavity and protected by the rib cage.

Pleura: Two membranes that surround the lungs. The space between the membranes contains a lubricating fluid that reduces friction during breathing.

Diaphragm: A large, dome-shaped muscle at the bottom of the chest cavity. It plays a crucial role in breathing.

Intercostal Muscles: Muscles located between the ribs that also assist in breathing.

Mechanism of Breathing (Ventilation): Inhalation (Inspiration): The diaphragm contracts and flattens, and the intercostal muscles contract, lifting the ribs up and out. This increases the volume of the chest cavity, decreasing the pressure inside the lungs. Air rushes into the lungs from the atmosphere, following the pressure gradient (air moves from high pressure to low pressure).

Exhalation (Expiration): The diaphragm relaxes and returns to its dome shape, and the intercostal muscles relax, lowering the ribs. This decreases the volume of the chest cavity, increasing the pressure inside the lungs. Air is forced out of the lungs into the atmosphere.

Gas Exchange: Oxygen (O2) diffuses from the alveoli into the blood capillaries, where it binds to hemoglobin in red blood cells. Carbon dioxide (CO2) diffuses from the blood capillaries into the alveoli. This exchange occurs because of differences in the concentration of oxygen and carbon dioxide between the air in the alveoli and the blood in the capillaries.