Anatomy and Physiology of the Nose

The nose is located above the mouth. It consists of:

The external meatus which is triangularly shaped located in the middle of the face.

The external nostrils.

The Septum is primarily made up of bone and cartilage which gives support and shape to the external nose.

The nasal passages and sinuses.

Physiology of the mouth

The mouth is anteriorly bounded by lips, posteriorly by fauces, laterally by cheeks, inferiorly by the muscular floor and superiorly by the palate.

The lips also called labia form the entrance to the mouth, and they are covered by skin. They include the orbicularis muscle which controls what comes in and out.

The cheeks represent the sidewalls of the oral cavity which are externally covered by the skin and internally by the mucous membrane.

Between the mucous membranes and the skin, there are buccinators muscles and connective tissue.

Inside the oral cavity, there are the teeth and the gum which consists the pocket-like oral vestibule.

Physiology of the Pharynx

The Pharynx which is a major musculo membranous tube functions in the respiratory and digestive systems. It consists of three parts:

The Nasopharynx which is located at the back of the nose and over the open soft palate.

The oropharynx which is situated at the center between the nasopharynx and the laryngopharynx.

The laryngopharynx is situated in the posterior part region and represents the place of divergence of the digestive and respiratory systems.

Physiology of the Larynx

The larynx is made up of the interior cavity, ligaments and elastic membranes, cartilaginous-osseous framework, muscles, vessels, joints, and nerves.

It is situated between the trachea and the tongue.

It protects the airway in the process of swallowing, phonation and respiration.

During inhaling and exhaling, the larynx through the epiglottis allows free passage of air while during swallowing the epiglottis is pushed posteriorly by food to block the entrance of substances in the larynx.

Functions of the voice box

Enhances gas exchange by allowing air to pass through to the respiratory systems.

Sound creation.

It protects the lungs from foreign substances.

It enhances coughing, swallowing and respiration.

Epiglottis

The epiglottis is made up of an elastic cartilage tissue which is coated with a mucous membrane and located at the larynx entrance.

It hangs downwards in the windpipe to protect swallowed food from getting into the lungs.

Normally, it points upwards to allow free air passage into the larynx and trachea.

During the eating process, it blocks the trachea to prevent entrance of the food substances into the windpipe and opens up when the swallowing process is over to allow normal breathing.

Physiology of Trachea

The trachea also the windpipe is a 12 cm long tube which connects the larynx with the lungs through principal bronchi.

Its main functions comprise free air flow to the lungs, air warming and humidification and mucociliary clearance.

It interacts with a visceral mesoderm developing from the foregut endodermal lining.

In adults, there are various stem cells types which exist in the glandular ducts and mucosal epithelium.

Physiology of lungs

The lung comprises left and right sides with three lobes:

The upper, middle and the lower lobe while the heart lies in the middle of the chest towards the left.

The bronchi distribute and separate air from the windpipe to the right and left sides.

The bronchi eventually create extra generations resembling a branch of a tree while they get smaller.

Physiology of the Bronchus

The bronchial vessels begin from the intercostals arteries or the aorta and enter the lungs through the hilum.

They branch at the conventional bronchus supplying extrapulmonary airways to the trachea and support structures.

This bronchial vasculature fraction drains rightwards to the heart through systemic veins.

The bronchus supply intrapulmonary airways up to the terminal bronchi forming extensive anastomoses.

Physiology of Bronchioles

The bronchioles are the tiniest airways inside the lungs which are not enclosed by cartilage.

They have approximately 1mm diameter located inside the lungs consisting of smooth muscles and connective tissues which maintain the tubes unlocked.

They further develop into many smaller tubules that continue to subdivide until they get to the alveoli.

Most bronchioles sections are lined between epithelial tissues or ciliated columnar which contain goblet cells.

Physiology of the Alveoli

Alveoli are void cavities which execute gas exchange in the blood within the longs.

The inhaled oxygen diffuses through the capillaries and alveoli walls into the blood cells that carry the air to the entire body tissues.

Carbon dioxide from the rest of the tissues of the body returns to the alveoli through the blood.

The carbon dioxide also diffuses in the respiratory membranes and capillary to get axed through respiration.

LIST OF REFERENCES

Brand-Saberi, B.E. and Schäfer, T., 2014. Trachea: anatomy and physiology. Thoracic surgery clinics, 24(1), pp.1-5.

Donaldson, A. and Raithatha, R., 2016. the Nose, Paranasal Sinuses, and Olfaction. Rhinology Handbook, p.1.

Herrmann, J., Tawhai, M.H. and Kaczka, D.W., 2016. Regional gas transport in the heterogeneous lung during oscillatory ventilation. Journal of Applied Physiology, 121(6), pp.1306-1318.

Ince, L.M., Pariollaud, M. and Gibbs, J.E., 2018. Lung Physiology and Defense. Current Opinion in Physiology.

Lieberman, G., 2015. Imaging the Trachea: Snapshots of Physiology.

Lumb, A.B., 2016. Nunn's applied respiratory physiology eBook. Elsevier Health Sciences.

Patwa, A. and Shah, A., 2015. Anatomy and physiology of respiratory system relevant to anaesthesia. Indian journal of anaesthesia, 59(9), p.533.

Sasaki, C.T., Lerner, M.Z. and Reza Nouraei, S.A., 2015. Physiology and phylogeny of the larynx and trachea. Laryngeal and Tracheobronchial Stenosis, p.27.

Sherwood, L., 2015. Human physiology: from cells to systems. Cengage learning.

Shier, D.N., Butler, J. and Lewis, R., 2017. Hole's essentials of human anatomy & physiology. McGraw-Hill Education.