Respiration
Respiration is a vital process for the normal function at every level of organization from a cell to an organism. Oxygen, supplied by local circulation at the tissue level, functions at the mitochondrial internal membrane as an essential mediator for the energy release.
Respiratory system
Respiratory system is the system consisting of specific organs and structures used for the process of respiration in an organism.
Functions of respiration
1. Ventilation: pumping of water in gills and pumping of air in lungs.
2. Internal Respiration: exchange of gases with the environment.
3. Internal Respiration: Essential gases are then exchange with the tissue in the respective capillary beds.
Respiratory Organs
Gills
vertebrate gills are designed for water breathing. Gills are thin tissue filaments that re highly branched and folded. When water passes over the gills, the dissolved oxygen in water rapidly diffuses across the gills into the bloodstream.
Gills are involved in many functions including the exchange of gases and other molecule between the body and surrounding water . These include oxygen, water, acid, urea, ammonia and carbon dioxide.
Skin
Earthworm and amphibians use their skin as a respiratory organ. A dense network of capillaries lie just below the skin and facilitate gas exchange between the external environment and the circulatory system. The respiratory surface must be kept moist in order for the gases to dissolve and diffuse across cell membrane.
Lungs
Lungs are designed for air breathing. They have elastic bag like nature. Their volume expands when air is inhaled and decreases when air is exhaled.
Human Respiratory System
The human respiratory system consist of the:
1. Upper Respiratory Tract : Nasal passages
2. The airway conduction system : Larynx, trachea, bronchi, bronchioles and terminal bronchioles.
3. The lower respiratory tract : Lungs
The function of pulmonary system is to extract oxygen from the environment and provide it for aerobic respiration at the cellular level.
Oxygen is ultimately used to produce ATP, and the carbon dioxide is breathed out with other metabolic byproducts.
Nose
The respiratory system of humans begins with the nose, where air is conditioned by warming and moistening. Bone partition separate the nasal cavity into chambers where air swirls about in currents. Hairs and hair like cilia trap dust particles and purify the air.
Pharynx
The nasal chambers open into the cavity at the rear of the mouth called the pharynx. From the pharynx, two tubes called Eustachian tubes open into the middle ear to equalize air pressure there. The pharynx also contain tonsils and adenoids, which are pocket of lymphatic tissue used to trap and filter microorganism.
Trachea
After passing through the pharynx, air passes into the windpipe called trachea. The trachea has a framework of smooth muscle with about 16 to 20 open rings of cartilage shaped like a C. These rings give rigidity to the trachea and ensure that it remains open. The opening of the trachea is a slit like structure called the glottis. A thin flapped of tissue called the epiglottis folds over the opening during swallowing and prevent food from entering the trachea. At the upper end of the trachea, several folds of the cartilage from the larynx, or voice box. In the larynx, flap like pairs of tissue called vocal cords vibrate when a person exhales and produces sound.
At its lower end, the trachea branches into two large bronchi. These tubes also have smooth muscles and cartilage rings . The bronchi branch into smaller bronchioles forming a bronchial tree. The bronchioles terminate in the alveoli.
Lungs
Humans lungs are composed of 300 million alveoli. Red blood cells pass through the capillaries in single file, and oxygen from each alveolus enters the red blood cells and bind to the hemoglobin. In addition, carbon dioxide in the plasma and red blood cells leave the capillaries and enters the alveoli when a breath is taken.
The alveoli is the functional unit of respiratory system.
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