The respiratory system which includes the air passages, pulmonary vessels, lungs and breathing muscles are the part of your body that allows you to breathe. It's primary function is to supply oxygen through the blood to the entire body. This is accomplished by inhaling air, processing it and exhaling carbon dioxide filled air which is part of the elimination process to remove waste gases. Respiratory function is one of the few functions of the body which is both involuntary (done without thinking and controlled by the parasympathetic nervous system) and voluntary (done with thinking and controlled by the sympathetic nervous system)
In addition to air distribution and gas exchange, the respiratory system filters, warms, and humidifies the air you breathe. Organs in the respiratory system also play a role in speech and the sense of smell. The respiratory system also helps the body maintain homeostasis, or balance among the many elements of the body’s internal environment.
The respiratory system is divided into two main components:
Upper Respiratory Tract
Air enters the body through the nose and mouth. When air goes in through the nose, it goes through the upper airways and comes in contact with parts of the respiratory structure helping clean the air and goes through several processes.
- Olfactory cells contain around twelve million nerve receptors which allow smells to be transported to the brain.
- Goblet cells which release mucus to trap dust particles and irritants and allow waste particles to be eliminated with the help of tiny hairs called cilia.
- Air then passes through the four different sinus cavities: Frontal sinus, above each eye and near the midline; Ethmoidal sinus, located on either side of the upper portion of the nasal cavity; Sphenoidal sinus located above the posterior portion of the nasal cavity and the Maxillary sinus located next to the nasal cavity (on each side) extending to the roots of the upper teeth.
- The Nasopharynx contains the auditory tube which connects to the middle ear
Breathing can occur through the mouth. Many times when the nasal passages are clogged air must then be brought in through the mouth and then down into the lungs.
- Oropharynx is the passage way for food and air
- Laryngopharynx is the passage way for food only.
- The larynx is the passage way for air only and is made of cartlage and elastic tissue
- Vocal cords vibrate to create speech
- False vocal cords are the area around vocal cords which often swell and impair vocal functions
- Epiglottis is the flap that closes when swallowing to prevent food from entering lungs
- Laryngeal cartilage forms much of the structure of the passage and opening of vocal cords.
Lower Respiratory Tract includes the lungs– a pair of organs found in all vertebrates.
The structure of the lungs includes the bronchial tree – air tubes branching off from the bronchi into smaller and smaller air tubes, each one ending in a pulmonary alveolus
- Trachea connects larynx to the bronchial branches
- Bronchi create the network of passages that begin the gas exchange for the blood.
- Alveolar ducts and sacs are extending tubules connected to the ends of the bronchi
- Alveoli do the final exchange from oxygen to carbon dioxide on the cellular level
- Capillary network covers the surface of alveoli allowing exchange of oxygen and carbon dioxide.
- Pulmonary artery brings old, used, blood to alveolar to release carbon dioxide into lung.
- Pulmonary vein takes new, oxygenated blood to the heart to be pumped throughout the body
- Pleural sac surrounds each lung with fluid to prevent friction during inhalation
- Diaphragm is the muscle responsible for breathing.
There are several necessary substances for good respiration. Without any one of these working the body will have difficulty functioning correctly.
- Phrenic nerve initiates contraction of diaphragm
- Surfactant cells secrete surfactant which keeps surface tension sufficient so alveolar sacs don't collapse.
- Oxyhemoglobin binds oxygen with hemoglobin
The act of breathing has two stages – inhalation and exhalation
- Inhalation – the intake of air into the lungs through expansion of chest volume. The muscles contract
- Exhalation – the expulsion of air from the lungs through contraction of chest volume. The muscles relax.
- Inhalation and exhalation involves muscles which are constantly contracting and relaxing approximately 16 ties per minute.
- Rib muscles - the muscles between the ribs in the chest
- Diaphragm muscle located at the bottom of the lungs.
Major Functions of Respiratory System
1. Pulmonary Ventilation - Breathing. Air is inhaled through the nose and mouth and moves into the lungs. Air containing carbon dioxide is exhaled through the same pathways.
2. External Respiration Exchanges Gases between the Lungs and the Bloodstream. Inside the lungs, oxygen is changed for carbon dioxide waste through the alveoli. Inhaled oxygen goes from the alveoli into the pulmonary capillaries surrounding them. Oxygen then binds to the hemoglobin molecules in red bloods cells and then pumped throughout the bloodstream. Returning blood diffuses through the capillaries back into the alveoli and is expelled through exhalation.
3. The bloodstream delivers oxygen to the cells and removes waste carbon dioxide through internal respiration. The red blood cells carry oxygen absorbed from the lung around the body where it diffuses through the capillaries and then releases the oxygen into the tissues. The carbon dioxide diffuses from the tissues into red blood cells and plasma to be returned to the lung and eliminated.
4. Smelling is a chemical sensation beginning with the olfactory fibers lining the nasal cavities inside the nose. Chemicals in the air bind to and activate the nervous system receptors on the cilia sending a signal to the brain. Neurons take the signal from the nasal cavities through openings in the ethmoid bone, and then to the olfactory bulbs. The signal then travels from the olfactory bulbs, along cranial nerve, to the olfactory area of the cerebral cortex
5. Sound is created when muscles in the larynx move the arytenoid cartilages, pushing them together. When the cords are pushed together, air passing between them makes them vibrate creaing sound. Greater tension in the vocal cords create more rapid vibrations and higher pitched sounds. Lesser tension causes slower vibration and a lower pitched sound.