RESPIRATORY SYSTEM

RESPIRATORY SYSTEM

This involves the process by which oxygen is taken into the body cells(s) and used to break down food particles in order to release energy. The intake of oxygen into each cell simultaneously accompanied by the removal of carbon dioxide and some molecules of water through the same rate (exchange surface)

RESPIRATION IN ANIMALS
Respiration in Animal is purely aerobic hence; all animals need a quick means of obtaining oxygen for their respiratory activities and this has led to the evolution of respiratory organs. There are four (4) different types of organs of surface which animals use for gaseous exchange and these are

1. Body Surfaces
2. Trachea
3. Gills
4. Lungs

Characteristics or features of a Good Respiratory surface

1. Presence of large surface area
2. A good respiratory surface must be well vascularized i.e supply of blood
3. It must have thin epithelium i.e Surface living
4. It must have a ventilation system
5. A good respiratory surface must always be moist etc

Respiratory Surfaces

1. Body Surface: This is used for gaseous exchange in the lower animal such as the moners, Protist (Amoeba) some nematodes and annelids. They are able to achieve this due to their small sizes which made them have a large surface area per volume ratio. Hence, Oxygen easily diffuses from their environment across the cell membrane into their cytoplasm for use. Gaseous exchange through the body surfaces is also found in some nematodes in which oxygen diffuses in their body through their moist. This type of respiration in them is called Cutaneous respiration.
2. The Trachea: The trachea is a system of branching tubes that is sub-divided into smaller units called tracheoles and this amplifies through the body of the animals. The trachea system opens through the ventilation structure called spiracles. Which line up at either side of thoracic and abdominal cavities in pairs. When the concentration of carbon iv oxide is high in the body tissues of arthropods, the spiracles valves opens widely and allows an inflow of air through it into the trachea, Carbon iv oxide also flows out simultaneously.

Diagram of a Trachea

3. The Gills
This is a highly braced respiratory growth with flat surface used for gaseous exchange in the aquatic environment.
Diagram of a Gill

The Gills
The gills can either be external or internal. External gills are found in tadpoles and slung while the internal gills are found in fish and some crustaceans, the external gills project out of the body of the organism and they are not covered by the operculum plate (Operculum) However, they are linked with the circulatory systems.

This is very important unlike the internal gills which are enclosed in a special chamber in the head region and projected by the operculum plate hence, internal gills are well protected from mechanical injury. Additionally, they don't hinder or prevent the free movement of the animal through the water.

The gills are made up of folding unit which is prevented from collapsing on one another by the density of the water if piration occurs when the fish opens its mouth and lowers the floor of the buccal cavity during which their operculum is tightly closed, water then rushes into the mouth and the dissolved oxygen diffuses across the surface of the gills into the circulatory system.
Expiration also occurs when then fish closes its mouth and the operculum plate is opened the carbon dioxide produced after respiration then flows out of the opercula chambers.

Exchange of gases takes place on the surface of the gills arch serves to hold the gills rackers functions in sieving out particles from the inflowing water to prevent their entry into surfaces of the gill filament thereby causing damage. The sieved out particles, in turn, serve as food for the fish.
4. The lungs - The lungs are the two most highly vascularised internal gaseous exchange surfaces used by terrestrial higher animals. The lungs is surrounded by a membrane called a pleural membrane and they are protected by the rib case. Air from outside is suckled through the mouth (Buccal Cavity) or the nose (nasal cavity) into the pharynx from where the air direct to the larynx.
Functions of some Respiratory organ

1. The Rib cage

a. It protects the lungs
b. It provides a means of breathing
2. Intercoastal muscle
a. It brings about the movement of ribs
3. Pleural Cavity
a. It protects the lungs
b. It provides a means for breathing
4. Diaphragm
a. It Protects the lungs
b. It brings about movement of the rib during breathing
5. Lungs, Bronchia and Trachea
They are reinforced with cartilage to prevent pipes from collapsing when air pressure within them is low.
Composition of Inhaled and Exhaled air
Gas                           Inhaled air                  Exhaled air
Oxygen                      21% 16%
Carbon dioxide           0.03%                        between 4 to 6%
Nitrogen                      78%                           78%
Water Vapour           Variable                         Saturated

NOTE: During normal, inspiration or respiration about 500cm3 of air goes in or out of the lungs. The air is known as tidal air, However, the lung usually has some leftover the air in it and the air is known as residual air.

After a normal Inspiration, more can still be possibly taken into the lung into its fullest capacity. This volume is known as a total living capacity.