How Respiratory System Works

Respiration and Respiratory Organs

Breathing is simply defined as the exchange of oxygen and carbon dioxide in the body.
Or, it is an oxidative process in which oxygen is absorbed into the tissue (from the lungs) to oxidize food and release energy and carbon dioxide.
The released energy is used to perform various life activities.
Metabolic waste such as CO2 is removed from the body through the lungs.
The oxidized compounds in respiration are called respiratory substrates.

Respiration is categorized into two types on the basis of site of gaseous exchange:

i) External breathing: exchange of gas between the lungs and the blood. It is the process of absorbing oxygen and removing carbon dioxide from the body through the lungs.
ii) Internal respiration: exchange of gas between blood and cells. It is the process of using oxygen to produce energy and carbon dioxide by oxidizing the food material inside the cell.

Respiratory organs

  1. Nose and nasal cavity
  2. Pharynx
  3. Larynx
  4. Trachea
  5. Bronchi
  6. Alveoli

1. Nose and nasal cavity

The nose is a part of the respiratory tract that is located above the mouth. It is produced from hyaline cartilage.
It is divided into the right and left nasal cavity by the nasal septum. Its anterior portion is cartilaginous and the posterior portion is bony.
The nasal cavities open outwards through the external nostrils or nostrils. The nasal cavities are subsequently opened into the nasopharynx through the internal nostrils.
The opening of the nasal sinuses and nasolacrimal ducts is located in the nasal cavities.
Internally, the nasal cavity is lined with mucous and cylindrical cylindrical epithelium. Contains nasal hair.
Function
I. Prevents the entry of dust particles into the lungs by trapping the powder in the mucus or nasal hair.
Mucus-secreting glands, i.e. goblet cells are located in the nasal chamber which produce mucus. Smoke or dust particles bound with mucus.
ii) The ciliated epithelium prevents infection by sweeping microorganisms.
iii) Heats the cold air and moistens the dry air.
iv. Detects odor. The upper third of the nasal mucosa is the olfactory area that contains the olfactory cells. These cells are involved in the perception of smell.
Internal noses: these are the openings of the nasal chambers at the root of the nasopharynx and are closed by the uvula during swallowing.

2. Pharynx

It is both the digestive and respiratory organs.
It is a 12-14 cm tube that extends the base of the skull to the level of the fifth cervical vertebra.
It is located behind the mouth, nose and larynx.
It is connected to the nasal cavity through the internal opening of the nostrils and to the mouth.

3. Larynx

Also called sound box or voice box.
It is located in the anterior neck, that is, in front of the esophagus.
It is a small, thin-walled tubular part, present in the neck at the apex of the trachea.
Connect the lower part of the pharynx and the trachea.
The pharynx opens into the larynx through the glottis which is protected by a leaf like an unpaired cartilage called an epiglottis. It prevents food from entering the trachea.
It consists of several irregularly shaped cartilages, which are: 1 thyroid cartilage, 1 cricoid cartilage and 2 arytenoid cartilage. They prevent the collapse of the larynx.
There are two vocal cords (true vocal cords) located in the cavity of the larynx between the thyroid and the arytenoid cartilage. Even a few vestibular folds have a protective function.
The size of the larynx is similar in boys and girls before puberty. After puberty, the larynx in males widens and is called the apple of Adam in males. Adam’s apple is the ventral swelling of the thyroid cartilage of the larynx.
function
I. Plays an important role in sound production.
ii) It joins the pharynx with the trachea, then allows the passage of air.
iii) Humidification, filtering and heating of the air occur in the larynx.
iv. Speech occurs when the sound produced by the vocal cords is manipulated by the tongue, cheeks and lips.
v. During swallowing, the larynx rises, blocking the opening from the pharynx. In addition, the epiglottis also closes on the larynx. This ensures that food passes into the esophagus and not into the trachea.

4. Trachea (Wind pipe)

It is a hollow tube approximately 11-12 cm long and 2.5 cm in diameter.
It extends from the base of the larynx to the thoracic cavity.
It runs on the neck in front of the esophagus.
It is supported by a 16-20 C-shaped cartilaginous tracheal ring. These rings prevent the trachea from collapsing due to continuous relaxation and expansion.
Internally, the wall of the trachea is lined with pseudostratified ciliated epithelium with goblet cells secreting mucus. The secretion of the mucous cells keeps the tube wall moist and traps the dust particles.
function
I. The mucus lubricates the passage and the eyelashes help filter the dust.
ii) The constant blink of the eyelashes brings mucus and debris to the pharynx, where it is ingested or expelled.
iii) Help in cough reflex.
iv. It is compatible with the head and neck.

5. Bronchi

When the trachea reaches the thoracic cavity, it is divided into two branches called bronchi, right and left bronchi.
Each bronchus has a structure similar to the trachea. The right bronchus is wider and shorter than the left bronchus. It is about 2.5 cm long and the left bronchus is about 5 cm long.
Each bronchus when it enters the corresponding lungs is divided into smaller secondary bronchi and then into tertiary bronchi. These bronchi are progressively divided into smaller and smaller tubes called bronchioles and therefore into terminal bronchioles. The bronchioles continue to expand and open into the respiratory bronchioles which in turn branch out into the alveolar duct leading to the alveoli (microscopic air sac).
function
I. The bronchi connect the trachea to the lungs, allowing air from the external respiratory openings to enter the lungs.

6. Alveoli

The bronchioles continue to expand and open into the respiratory bronchioles which in turn branch out into the alveolar duct leading to the microscopic air sac called alveoli. The gas exchange takes place in the alveoli. The alveoli are rich in blood capillaries. The wall of the alveoli is lined with type I pneumocytes that promote gas exchange and type II pneumocytes produce surfactant. The surfactant reduces surface tension so that the lungs don’t collapse.
function
I. The alveoli assist in blood purification.
ii) Allows the exchange of oxygen and carbon dioxide in the lungs.

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