Class :


Term :

First Term

Week :

Week 5

Instructional Teaching Materials :

  • Photos of plants and animals
  • Sample alimentary canal of animal



  • Scheme of Work
  • On-line Information
  • Textbooks
  • Workbooks

Earlier Tutorials 

The pupils have earlier information on

Types of Circulation and Circulatory Systems

that was beforehand taught as a topic before this specific lesson


Behavioural Objectives :  On the conclusion  of this lesson, the learners will likely be succesful to

  • Say





Types of Respiratory Systems


Types of Respiratory Systems

Note That respiration is one of the characteristics of living things we discussed in our basic classes, In this process, oxygen is taken in while carbon iv oxide is given out. The two basic types of respiration are; aerobic and anaerobic respiration.

Respiratory system refers to all the parts or organs and cells responsible for respiration process that take place in the organism.

Respiration is simply a biochemical process in which energy is liberated from food substances (mainly simple sugars) in the mitochondria of living cells with the aid of enzymes in the absence or presence of oxygen.

The production of water, carbon iv oxide, alcohol or other organic substances is just incidental to the basic process. Respiration is achieved through the mouth, nose, trachea, lungs and diaphragm. The system functions to obtain oxygen for use by the body and to eliminate the carbon iv oxide. It works in conjunction with the circulatory system.

In animals, the structures associated with respiration include the following organs:

  1. Body surface (amoeba, paramecium,earthworm,).
  2. Lung books (spider,)
  3. Gills (tadpole, molluscs, fish).
  4. Trachea (man, insects,)
  5. Lungs (reptiles, man, birds, goat and other mammals etc)

In plants, the stomata and Lenticels are the main respiratory structures for gas exchange by diffusion. Gas exchange in animals depends on their respiratory medium (whether it is air or water) and the nature of their respiratory surfaces. For aquatic animals, the respiratory medium is water, as for terrestrial animals, the medium is air. Amphibians and some fishes use both air and water as their media of exchange.

The exchange of gases with the respiratory medium by animals is called breathing. The respiratory surface provides a boundary between the body and respiratory medium. The cells in this surface are epithelial in nature (have thin wall) and have large surface area. This enhances diffusion.

Body Surface Respiration

This is the simplest type of respiration found mainly in unicellular organisms and some multi-cellular organisms such as Annelids (earthworms), platyhelminthes (flatworms), sponges, toads and frogs. Respiration occurs by diffusion. In unicellular organisms, exchange of gases takes place at the respiratory surfaces. Gases are dissolved in water before they are diffused across the cell membrane. Organisms that respire through their body surface possess moist skin. As for breathing, it is a visible, mechanical, muscular action, which enables an animal to quicken the rate of gas exchange between itself and its environment.


The gill is found in large aquatic organisms such as tadpole, aquatic snails and fishes. Gills are highly branched and vascularised, i.e., they are richly supplied with blood capillaries. Gills may be external or enclosed. External gills may be sea slugs and amphibian larvae, whereas in enclosed gills are found in water snails and crustaceans.

How Fish Breathe

A fish breathes by absorbing oxygen from the water it drinks. Water flows into the mouth, through the gills, and out of the body through gill slits. As water flows through the gills, the oxygen it contains passes into blood circulating through gill structures called filaments and lamellae. At the same time, carbon dioxide in the fish’s bloodstream passes into the water and is carried out of the body.

Tracheal System

Tracheal System is common in insects and many other arthropods. It ends up in tiny holes in the cuticle called spiracles. The spiracles open and close by muscular action. The tracheae branch repeatedly into fine branches called tracheoles, which are equivalent to the air sacs in the lungs. The tracheoles contain fluid in which oxygen dissolves before actually getting to the individual cells of the body.

Anatomy of a Grasshopper

This illustration of a grasshopper depicts the tiny circular openings called spiracles through which most insects obtain oxygen. From the spiracles, tubes called tracheae reach deep within the body to supply oxygen to every cell.


In developed organisms (animals), lungs is the main respiratory organ e.g., in terrestrial vertebrates like mammals. Lungs are closely linked with the circulatory system. Lungs are found in amphibians, birds, and mammals. The mammalian respiratory system consists of the nostrils, pharynx, larynx, lungs and diaphragm.

Characteristics of Respiratory Surface

The following characteristics have been identified in exchange of gases in respiratory surfaces:

  1. Epithelia in nature
  2. Have very thin walls which shorten the diffusion distance and increase diffusion rate.
  3. Mostly moist because gases diffuse in solution through them.
  4. Possess delicate cells.
  5. Have a large surface area to volume ratio, which ensures exchange of large quantities of gases.

Mechanisms of Respiratory System

In plants and animals, respiration is through basic gas exchange facilitated by organs such as stomata, gills, lungs, and skin.

However, in lower animals diffusion occurs through the membranes. In higher animals the internal organs are kept away from the environment. In vertebrate animals, exchange of gases takes place by inhalation and exhalation. This is referred to the breathing in and breathing out.


A scanning electron micrograph reveals the tiny sacs known as alveoli within a section of human lung tissue. Human beings have a thin layer of about 700 million alveoli within their lungs. This layer is crucial in the process called respiration, exchanging oxygen and carbon dioxide with the surrounding blood capillaries.

  1. fine diffusion and osmosis.



  1. Respiration in Higher Animals
  2. Respiration in Lower Animals
  3. Gaseous Exchange in Plants

Respiration in Higher Animals

This type of respiration takes place through the lungs. All mammals have a pair of lungs. lungs adaptations that allow animals to invade the terrestrial environment. Some fishes, and amphibians, reptiles, birds, and mammals, all have their lungs located internally. Mammals breathing system comprises the air passages (nostrils, pharynx, larynx, and trachea), lungs and diaphragm. Oxygen enters the nasal passage through the nostrils into the nasal cavity where it is moistened and kept warm. The nasal cavity has lining cells, which secretes mucus that traps most of the dust and microorganisms present in the air before it diffuses into the lungs.

Nasal cavity leads into the pharynx, the to the trachea (wind pipe), which divides into two bronchi before it enters into the lungs; the cartilages supports the wall of the trachea and bronchus to prevent them from collapsing when the air pressure in them is reduced. Within each lung, the bronchus divides repeatedly and becomes progressively narrower forming numerous tiny tubules called bronchioles, which end in pockets of the air sacs called alveoli. Alveoli are surrounded by a dense network of capillaries, which enhances gas exchange.

Breathing in Humans

As the diaphragm contracts and moves downward, the pectoralis minor and intercostal muscles pull the rib cage outward. The chest cavity expands, and air rushes into the lungs through the trachea to fill the resulting vacuum. When the diaphragm relaxes to its normal, upwardly curving position, the lungs contract, and air is forced out.

The alveoli give the lungs a very large surface area for gas exchange. The lungs are located in the thorax or thoracic cavity, which comprises the breast bone or sternum in front, and the back bone (vertebrae) at the back. At the sides are twelve (12) pairs of ribs and intercostals muscles, which are attached to the spine and the sternum, thereby, forming a bony cage. The diaphragm is a sheet of muscle at the floor of the thorax.

The Human Lungs

In humans the lungs occupy a large portion of the chest cavity from the collarbone down to the diaphragm. The right lung is divided into three sections, or lobes. The left lung, with a cleft to accommodate the heart, has only two lobes. The two branches of the trachea, called bronchi, subdivide within the lobes into smaller and smaller air vessels known as bronchioles. Bronchioles terminate in alveoli, tiny air sacs surrounded by capillaries. When the alveoli inflate with inhaled air, oxygen diffuses into the blood in the capillaries to be pumped by the heart to the tissues of the body. At the same time carbon dioxide diffuses out of the blood into the lungs, where it is exhaled.

Mechanism of Breathing in Mammals


  1. The inter costals muscles contract, while the ribs move upward and outwards.
  2. The diaphragm contracts and flattens out.
  3. The thoracic cavity volume increases, while its air pressure decreases.
  4. Air is then forced from outside into the lungs through the air passage.





The topic is obtainable step-by-step


Step 1:

The subject instructor revises the sooner issues


Step 2.

He introduces the topic new topic


Step 3:

The class coach permits the pupils to current their very personal examples and he corrects them when the desires come up



Conclusion :


The class coach wraps up or conclude the lesson by giving out temporary observe to summarize the topic that he or she has merely taught.

The class coach moreover goes spherical to ensure that the notes are correctly copied or correctly written by the pupils.

He or she does the required corrections when and the place  the desires come up.




  1. The intercostals muscles relax, while the ribs cage is lowered.
  2. The diaphragm relaxes and returns to its original dome-shaped position.
  3. The thoracic cavity volume decreases, while the lungs shrink.
  4. The lung air pressure increases, and a lot of air is expelled from the lungs through the air passage.





The topic wraps up the subject by giving the learners a complete notice and she or he makes certain that the learners copy the notes accurately . She or he marks the notes and he does the mandatory corrections