Introduction
Refer to the following sections for background information:
• the requirements of efficient gaseous exchange organs in lesson 1
• cellular respiration in Grade 11
• animal tissues in Grade 10
Task
Underline the most important points on the notes given and paste diagrams on the notebooks
Answer asked questions
(The teacher will be using handouts to develop the lesson
,explain notes in class and give out diagrams
Asks learners questions to check their level of understanding)
Below are definitions of some of the terms that you will study under this section. Use your textbook for glossary and underline all the new terms/words that you encounter while studying through this section. Use the glossary in your textbook to define these new terms/words
(Note: At least 2 marks are awarded if you can define a term correctly in a test or examination)
Diaphragm – The muscular plate which separates the thoracic cavity from the abdominal cavity in humans
Alveoli – The part of the lungs where the exchange of gases takes place
Bronchi – The two main branches of the trachea
Intercostal muscles – The muscles found between the ribs and involved in the mechanism of breathing
Epiglottis – The structure that prevents food from entering the trachea during swallowing
The ventilation/breathing system of humans consist of the:
• Nasal cavities
• Trachea
• Two bronchi
• Many bronchioles
• Two lungs
• Respiratory muscles
Diagram of a human respiratory system
Nasal cavities:
• The two external nostrils lead to two nasal cavities that are separated by a septum
• Small hairs in the nasal cavities filter large particles from the inhaled air
• Each nasal cavity is divided into three passages by three curved turbinate bones.
• The nasal cavities are lined with a mucous membrane that consists of ciliated columnar epithelial cells
• The epithelial cells are richly supplied with blood capillaries that warms the incoming air
• Goblet cells in the epithelium secrete mucus that moistens the incoming air, traps dust and germs, and is
antiseptic.
• Cilia on the epithelial cells perform sweeping movements in a direction away from the lungs to expel dust –
carrying mucus to the outside.
Pharynx:
• The nasal cavities open into the pharynx.
• The pharynx leads to two openings i.e. the opening known as the glottis which leads to the trachea and the
opening that leads to the oesophagus
Trachea:
• The trachea is a long, tubular structure located at the front of the oesophagus
• The larynx (voice box) with the vocal chords is located at the top of the trachea
• The epiglottis is at the top of the larynx and consists of cartilage
• The epiglottis closes the glottis during the swallowing process and prevents food from entering the trachea
• The walls of the trachea are supported and kept open by C-shaped cartilage rings.
• The trachea is lined with ciliated columnar epithelium with goblet cells that secrete mucus.
• The mucus moistens the incoming air and trap dust particles
• Mucus with trapped foreign particles are moved to the pharynx through the sweeping actions of the cilia
Bronchi, bronchioles and alveoli:
• The trachea branches into two bronchi that enters the right and left lung
• The bronchi are also lined with a mucous membrane and are held open by O-shaped cartilage rings
• The bronchi divide into smaller branches inside the lungs and form the bronchioles
• The bronchioles do not have cartilage rings and their walls consist of smooth muscle that can contract and relax
to alter air flow.
• Each bronchiole ends in an infundibulum which consists of groups of alveoli.
• The millions of alveoli increase the gaseous exchange surface
• The walls of the alveoli are thin and consists of a single layer of squamous epithelium. These thin walls allow for
efficient gaseous exchange
• A thin layer of tissue fluid lines the inside surface of the alveoli and keep the surface of the alveoli moist, preventing the cells from drying out.
• The alveoli are surrounded by a network of capillaries.
• Capillaries transport oxygen to the tissues and carbon dioxide to the lungs
• The walls of the capillaries are thin and consist of a single layer of the squamous epithelium to allow for efficient gaseous exchange.
DIAGRAM OF ALVEOLI, BRONCHIOLE AND CAPILLARIES
Lungs:
• The two lungs are located in the chest and are and protected by 12 pairs of ribs.
• The lungs are spongy and elastic and can expand and contract during breathing
• The right lung has three lobes and the left lung has two lobes
• Each lung is surrounded by a double membrane, the pleura
• The fluid between the pleura prevents friction when the lung expands or shrinks
Respiratory muscles:
Diaphragm:
• The diaphragm is a dome-shaped muscle plate which separates the chest and the abdomen
Intercostal muscles:
• The intercostal muscles are located between consecutive ribs and consists of the external and internal intercostal
muscles.
Process
PLEASE NOTE
Know the meaning of instructional verbs in test and examination questions e.g.
Instructional verb Meaning
Name Give the name of something
Differentiate Use differences to qualify between two or more categories
Tabulate Draw a table and indicate the answers as direct pairs.
Describe State in sentences the main points of a process
Explain Give your answer in a cause-effect or statement and reason sequence
Compare Give similarities and differences between concepts.
HOMEWORK
Answer all the questions below according to the diagram below
Which of the following are represented by A, D and G?
A Larynx, trachea, diaphragm
B Larynx, trachea, diaphragm
C Larynx, lung, alveolus
D Bronchiole, lung, alveolus
1.1.7 Which ONE of the following is a function of structure H?
A During inhalation it contracts and during exhalation it relaxes.
B During inhalation it relaxes and during exhalation it contracts.
C During inhalation it is arched and during exhalation it relaxes.
D During inhalation it contracts and during exhalation it is flattened.
Evaluation
Below are definitions of some of the terms that you will study under this section. Use your textbook and underline all the new terms/words that you encounter while studying through this section. Use the glossary in your textbook to define these new terms/words
(Note: At least 2 marks are awarded if you can define a term correctly in a test or examination)
PLEASE NOTE
Know the meaning of instructional verbs in test and examination questions e.g.
Instructional verb Meaning
Name Give the name of something
Differentiate Use differences to qualify between two or more categories
Tabulate Draw a table and indicate the answers as direct pairs.
Describe State in sentences the main points of a process
Explain Give your answer in a cause-effect or statement and reason sequence
Compare Give similarities and differences between concepts
Conclusion
The teacher emphasizes key points and ask learners some questions or allow the learners to ask their questions
Gives the homework.
Learners answer questions or ask questions
TAKE THEIR HOMEWORK
Credits
(Note: At least 2 marks are awarded if you can define a term correctly in a test or examination)
Teacher Page
I have listed the all the links as to direct the learners straight to the applicable subtopic explained on the notes