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Introduction The primary function of the respiratory system is to supply the blood with oxygen in order for the blood to deliver oxygen to all of the body. The respiratory system does this through breathing. When we breathe we inhale oxygen and exhale carbon dioxide.

Mouth/Nose Respiration is achieved through the mouth, nose, trachea, lungs and diaphragm. Oxygen enters the respiratory system through the mouth and the nose. So we will start by explaining the Mouth and the Nose. In scientific terms the Mouth is also known as the, Oral Cavity and the Nose as the Nasal Cavity. When you inhale, air enters through the Nose or Mouth. As air is breathed through the nose, it is warmed, moistened and filtered by the hairs that line the nostrils. The hairs that line the wall can be seen as “the air-cleaning system”. Air also enters trough the Mouth (Oral Cavity), especially in people who have a mouth-breathing habit or whose nasal passages may be temporarily obstructed as by a cold or during heavy exercise. The human mouth ( or oral cavity ) is the first portion of the alimentary canal that receives food and begins digestion by mechanically breaking up the solid food particles into smaller pieces and missing the with saliva. So the mouth is actually mage more for eating and the nose is made more for breathing.

The Mechanics of Breathing Antagonistic muscles contract and help lift ribs upward. Antagonistic muscles relax creating less space in the lungs and increasing the pressure causing air to be forced off.

Practical Exercise – Lung Capacity Bag

Nasal Cavity The nasal cavity is the interior area of the nose; lined with a sticky mucous membrane and contains short, thick surface cilia hairs. The nasal cavity helps to filter air that is passed through to the respiratory system. Due to the large surface area provided by the conchae, the air passing through the nasal cavity is warmed or cooled within 1 degree of body temperature.

The Nasal Cavity

The throat, doctors prefer to use the more precise term "pharynx". Pharynx describes the part of the throat that begins from behind the nose to the beginning of the voice box and the oesophagus. The pharynx is a common channel that conducts both air and food. Because of these two functions, the pharynx must open to allow air and food to pass through, and at the same time, it must be able to squeeze and propel the food down into the oesophagus. The pharynx must be able to perform these functions simultaneously at mealtimes. It can do this because, unlike the nose or the windpipe, which are rigid, the pharynx is a soft muscular tube and can squeeze food down during swallowing

Because the pharynx also acts as an airway, an mechanical obstruction of the pharynx can also cause airway obstruction. There is one type of obstruction that is peculiar to the pharynx. Unlike the nose and the windpipe, which are rigid structures, the pharynx is a soft collapsible tube. Obstruction can occur even without a physically enlarged structure : In an unconscious patient the tongue can fall back to cause obstruction An unconscious patient may vomit and the vomitus may go into the lungs because the vocal cords of the unconscious patient do not react to protect the lungs During sleep, there is a very common disorder called Obstructive Sleep Apnea (OSA) in which the pharynx collapses repeatedly during sleep.

The Larynx The main functions of the larynx include Production of sound, where pitch and volume are manipulated Allowing exchange of air from nasal cavity to bronchioles Assisting in swallowing

Dissection of the Larynx

The trachea or windpipe, is the bony tube that connects the nose and mouth to the lungs. It is an important part of the vertebrate respiratory system. When an individual breathes in, air flows into he lungs for respiration through the windpipe/trachea. This is why any damage to the windpipe is potentially life threatening.

The large air tubes leading from the trachea to the lungs that convey air to and from the lungs. The bronchi have cartilage as part of their supporting wall structure. The trachea divides to form the right and left main bronchi which, in turn, divide to form the lobar, segmental, and finally the sub segmental bronchi.

The bronchioles are the first airway branches that no longer contain cartilage. They are branches of the bronchi, and are smaller than one millimetre in diameter. There are no glands or cartilage in any of the bronchioles, and the epithelial cells become more cuboidal in shape.cuboidal The bronchioles terminate by entering the circular sacs called alveoli. Control of airflow resistance and air distribution in the lungs is controlled by the bronchioles.

The Alveoli The lungs contain about 300million alveoli, representing a total surface area of approximately square metres. Each alveolus is wrapped in a fine mesh of capillaries and the alveoli structure consists of epithelial cells and extra cellular matrix's surrounded by capillaries.

Capillary Network

Diseases Empty Nose SyndromeLarynx Cancer

Asthma is a long-lasting disease of the lungs and bronchi that affects 5 people in every 100. Asthma is characterised by attacks of breathlessness, tight chest, wheezing and coughing which are caused by the airways becoming narrowed and inflamed. Some people may have these symptoms all of the time and others may be normal between attacks. Asthma can arise at any age, but why some people have the disease and others don't is not known. People with asthma have airways that are more sensitive than normal.

Bronchitis is the inflammation of the bronchi this means the air flow is restricted to and from the lungs and a heavy mucus is formed in the bronchi. The cause of bronchitis is due to viruses getting into the airways and cause infection and produces swelling and mucus. In most cases the viruses which cause colds cause bronchitis but only acute bronchitis. The most well known way of getting bronchitis is smoking due to when you smoke you inhale dangerous chemicals which pass through your lungs and can cause infection in your bronchi but it is more serious than acute bronchitis because it can cause chronic bronchitis.