When looking into the anatomy of the respiratory system, one needs to take a look at all the components involved in breathing. Through respiration, lungs experience ventilation (breathing), an exchange of gases happens between air and blood and between blood and cells, which cause oxygen perfusion throughout the whole body on a cellular level.
Respiratory System Functions:
- provides the body with an oxygen supply
- eliminates carbon dioxide
- allows gas exchange
- provides a path to and from the alveoli
- provides a sense of smell through the olfactory system
- acts as a humidifier by warming incoming air
- maintains a balanced pH in the body
- allows expulsion of abdominal content (such as during childbirth)
The respiratory system can be divided into the following sub-categories:
Upper Respiratory Tract:
- Nose: includes nostrils (nares), guard hairs (vibrissae, which help prevent insects and large particles from entering the nose), posterior nasal apertures (choanae), nasal cavity, nasal septum (composed of bone and cartilage), nasal fossae, nasal conchae, hard palate, soft palate, paranasal sinuses (which help decrease weight of skull due to its air content), goblet cells, respiratory epithelium of ciliated pseudostratified columnar type, and olfactory epithelium; functions include warming, humidifying and cleansing the inhaled air, providing a sense of smell, and helping in voice amplification.
- Pharynx: a muscular structure about 5 inches long that acts as a common passageway for food and air consisting of the nasopharynx (lined with pseudostratified columnar epithelium), oropharynx and laryngopharynx (both lined with stratified squamous epithelium, making it a hard surface to be able to tolerate abrasion caused by the swallowing of food); includes an auditory tube, pharyngeal tonsil, palatine tonsils and lingual tonsils (tonsils help combat infection).
- Larynx: plays an important role in speech through the vocal cords; comprises of 9 rigid hyaline cartilages with a flap of elastic cartilage known as the epiglottis that helps lead air and food into their appropriate pathways.
Lower Respiratory Tract:
- Trachea: contains c-shaped hyaline cartilage rings that help support it (open parts of ‘c’ face the oesophagus to allow expansion whilst swallowing; lined with ciliated pseudostratified columnar epithelium with a lot of goblet cells that cause mucus production; mucus traps any debris, pushing it upwards through the mucociliary escalator towards the pharynx to be swallowed.
- Bronchi: formed by the division of the trachea, just beneath the carina; supported by hyaline cartilage with a smooth muscle layered wall. These are further divided into secondary bronchi, one for every lobe within the lungs.
- Bronchioles: the smallest of all bronchi, which end up with alveolar sacs; do not contain cartilage but are supported by smooth muscle, making them able to dilate or contract to cause bronchodilation or bronchoconstriction.
- Alveoli: comprised of a single thin layer of squamous alveolar cells that facilitate gas exchange; contain alveolar macrophages (white blood cells) that engulf any bacteria or other debris; great alveolar cells produce a lipid molecule ‘surfactant‘ which coats the alveolar surfaces, preventing the alveoli walls from sticking together, thus allowing them to inflate easily during inhalation; air that enters the alveoli becomes available for gas exchange.
- Lungs: found within the thoracic cavity; the stroma, which is made of elastic connective tissue, allows the lungs to recoil passively during exhalation; contain the visceral pleura (which ‘hugs’ the lungs), the parietal pleura (the outer layer), both encasing the pleural cavity which contains fluid that helps reduce friction between the lungs and the ribcage while they expand and contract); the two lungs are separated by the mediastinum which is the space found between the two lungs containing the heart, oesophagus and the major blood vessels. The right lung has 2 fissures, forming the superior lobe, middle lobe and inferior lobe. The left lung has 1 fissure, forming the superior lobe and the inferior lobe. The left lung also has the ‘cardiac notch‘, which is the area that houses the heart.
THE CONDUCTING ZONE forms a continuous passageway for air to move in and out of the lungs:
Nose > Pharynx > Larynx > Trachea > Bronchi > Bronchioles > Terminal Bronchioles
THE RESPIRATORY ZONE forms a passageway in which air is exchanged:
Respiratory bronchioles > Alveolar ducts > Alveolar sac
The respiratory membrane consists of squamous alveolar cell, squamous endothelial cell that lines the capillary, and a shared thin basement membrane, all of which help facilitate gas exchange.
Below you can find a collection of videos that can help provide a more visual approach to the anatomy of the respiratory system.
Anatomy of the respiratory System – Animation
https://www.youtube.com/watch?v=kacMYexDgHg
Overview of the Respiratory System – Animation
Lung Anatomy
The Respiratory System
Respiratory System Physiology
Special thanks to the creators of the featured videos on this post, specifically Youtube Channels Alila Medical Media, Registered Nurse RN, KhanAcademyMedicine and Professor Dave Explains.
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