Unifying concepts of Animal Respiration - The respiratory system consist of several organs that facilitates gas exchange. Gas exchange requires close cooperation between the circulatory system and the respiratory system.

The exchange of O2 and CO2 between cells and the environment makes it possible for animals to put to work the food molecules that the digestive system provides.

Respiratory Surfaces

The part of an animal where O2 from the environment diffuses into living cells and CO2 diffuses out to the surrounding environment is the respiratory surface. The respiratory surface is usually covered with a single layer of living cells that is thin enough to allow rapid diffusion between the body and the environment.

The respiratory surface of an animal must be large enough to take up O2 for every cell in the body. A variety of solutions have evolved from this, varying mainly with the size of the organism and whether it lives in water or land.

There are four types of respiratory organs There are four types of respiratory organs. Each of the four parts includes a cross section of the animal’s body through the respiratory surface.

1. Some small animals, such as earthworms, use their entire moist outer skin as a respiratory organ.

2. Fishes and many other aquatic animals have gills, feathery respiratory surfaces that extend into the surrounding water.

3. Terrestrial insects have a persuasive system of interval tube called tracheae that channel air directly to cells.

4. Most terrestrial vertebrates exchange gasses across the thin lining of lungs, internal organs with a rich blood supply.

The Human Respiratory System

The three phases of gas exchange:

Structure and Function: The lung is located at the chest cavity, bordered along the bottom by the diaphragm.

Process: Air enters the respiratory system through external openings such as the nostrils and the mouth. In the nasal cavity, air is filtered by hairs, warned, and sampled by smell receptors. The air passes to the pharynx where the digestive and respiratory system meets. From the pharynx, air is inhaled into the larynx and then into the trachea. The trachea forks into two bronchi, one leading to each lung. Within the lungs, each bronchus branches repeatedly into finer tubes called bronchioles. The bronchioles dead-end in grape-like clusters of air sacs called alveoli.

- Breathing consist of alternating processes of inhalations and exhalation. When inhaling, ribs move upward and spread out as muscles between them contract and the diaphragm moves downward expanding the chest cavity. This increases the volume of the lungs, dropping the air pressure of the atmosphere. The result is that air rushes in through the mouth and nostrils toward the region of lower pressure, filling the lungs. This is called negative pressure breathing.

Automatic control centers in the brain regulate breathing Automatic control centers in the brain regulate breathing. While at rest, the control centers send out signals that maintain a respiratory rate of 10-14 inhalations per minute. You can make yourself dizzy by hyperventilating, taking excessively rapid, deep breaths.

Blood transports respiratory gases: - Low-oxygen blood travels to the right side of the heart and is pumped to the lungs. -     Oxygen-rich blood moves through the left side of the heart and travels to the body cells -  Body tissues absorb oxygen and release carbon dioxide -     Gas movement depends on the partial pressure of each gas o Gases move from an area of high pressure to an area of low pressure

The role of hemoglobin in gas transport: The human respiratory system takes O2 into the body and expels CO2, but it relies on the circulatory system to shuttle these gases between the lungs and the body’s cells. Red cells are particularly well suited to transporting oxygen because they contain a special oxygen-binding protein known as hemoglobin. Each molecule of hemoglobin is based on iron which binds oxygen loosely and reversibly.

Diseases of the lungs: - permanent enlargement of air sacs (alveoli) with loss of ability to completely exhale (emphysema) - hereditary lung blockages (cystic fibrosis) - long-term (chronic) infections (sarcoidosis) - permanent scarring and thickening of lung tissue (idiopathic pulmonary fibrosis)