Thanks to the respiratory system our bodies get necessary oxygen and release unwanted carbon dioxide. This would be impossible without the cardiovascular system though.
The respiratory system consists of nose and nasal cavity, pharynx, larynx, trachea, bronchi and their smaller branches, and lungs.
The nose is the entering point for oxygen and the exit point for carbon dioxide. The nasal cavity is the internal part of the nose where smell (olfactory) receptors and respiratory mucosa, that humidifies and warms air, are located. Furthermore, a sticky mucus is produced from the mucus glands and acts as a barrier for bacteria.
The pharynx is a muscular passageway through which both food and air travel. It is about 5 inches long. The pharynx is connected to the middle ears through the pharyngotympanic tubes which explains why an ear infection may result in a sore throat.
The larynx is responsible for voice but also to navigate food and air into the right passageways. Food enters the oesophagus and travels to the stomach while air enters the trachea and travels to the lungs. The larynx is made of cartilage and muscles. In men the thyroid cartilage is referred to as ‘Adam’s apple’. One of the reasons you can’t take a breath in while swallowing is due to the epiglottis (spoon shaped cartilage) closing the passageway to the trachea. This is essential to prevent aspiration and choking. In patients with Dementia swallowing becomes a problem as the epiglottis weakens and does not always function effectively. This condition is known as dysphagia and may lead to frequent chest infections.
The trachea is about 4 inches long and leads air to the lungs. It is made of hyaline cartilage and divides into main bronchus.
The main bronchi are left and right bronchus. The right one is wider, shorter and straighter compared to the left one which is why foreign objects usually end up in the right bronchus. The bronchi are connected to the lungs through smaller subdivisions (bronchioles and the smallest alveoli) resembling roots of a tree. The alveoli are tiny air sacs where gas (O2, CO2) exchange occurs. Tiny blood vessels then carry oxygen to the rest of the body.
The lungs are soft and spongy. They are located in the thoracic cavity and are surrounded by a protective rib cage. The right lung has 3 lobes: upper, middle and lower lobe, while the left lung has only 2 lobes: upper and lower lobe due to the heart’s positioning. Each lung is covered by a two-layered membrane called pulmonary pleura. Between the two layers is the pleural cavity where there is vacuum and serous fluid which reduces friction. A condition called pneumothorax occurs when air or gas enters the pleural cavity. Pleural effusion occurs when liquid enters the pleural cavity, while hemothorax, particularly, is when blood enters the pleural cavity. Pleural effusion may lead to lung failure so a chest drain is inserted to get rid of excess fluid or blood.
The diaphragm is a smooth muscle at the base of the lungs which assists breathing. It is not part of the respiratory system but plays vital function in it.