The trachea bifurcates into the left main and right main bronchus at the level of the sternal angle in the thorax. When an object is accidently inhaled, it will most likely lodge in the right main bronchus or the inferior lobar bronchus, which is a further division of the right main. The right bronchus is shorter, wider, and more vertical than the left, leading to a more direct path for any objects inhaled and a higher probability that they will enter the right branch than the left.

The trachea, or windpipe, is a rigid tube that carries air from the larynx into the bronchi. The rigidity comes from C-shaped rings of cartilage.

The pharynx, or throat, is a muscular funnel that receives air from the nose, and food and drink from the mouth. The larynx, or voice box, is also formed from cartilage. The uppermost cartilage is the epiglottis, which separates the respiratory tract from the digestive tract. The thyroid cartilage, or "Adam's apple," forms the anterior and lateral walls of the larynx. The cricoid cartilage connects the larynx to the trachea. The bronchi are also supported by C-shaped cartilages. The bronchi transport air into the lungs following bifurcation of the trachea.

The right lung has 3 lobes while the left lung has 2 lobes. This is because the right lobe has 2 fissures, while the left lobe only has 1. The right lobe is separated into the superior, middle, and inferior lobes by the horizontal and oblique fissures, respectively. The left lobe is divided into the superior and inferior lobes by the oblique fissure. 

In the right lung, the pulmonary artery is anterior to the bronchus. Instead, in the left lung, the pulmonary artery is superior to the bronchus. The mnemonic "RALS" is a helpful tool to remember this. RALS stands for in the Right lung, the pulmonary artery is Anterior to the bronchus, while in the Left lung, the pulmonary artery is Superior to the bronchus. It is important to be able to identify these features because they will help us know which lung we are looking at. 

In the right lung, the pulmonary artery is anterior to the bronchus. Instead, in the left lung, the pulmonary artery is superior to the bronchus. The mnemonic "RALS" is a helpful tool to remember this. RALS stands for in the Right lung, the pulmonary artery is Anterior to the bronchus, while in the Left lung, the pulmonary artery is Superior to the bronchus. It is important to be able to identify these features because they will help us know which lung we are looking at.

The left is smaller and has only two lobes because it allows room for the heart in its cardiac notch. The right lung has three lobes. Remember, if you are looking at the anterior side of a human (face side), the right lung is on your left side as the observer. 

Air from the nose or mouth meets the trachea, then the bronchi, then the bronchioles (primary, secondary, tertiary, terminal, then respiratory), then to the alveolar sacs and ducts, and finally the alveoli. Each structure after the bronchi is more branched and thinner to allow the successive expansion of air volume to meet the alveoli. The first part in the respiratory tract where gas exchange occurs is across the respiratory bronchioles, every structure leading to these have been purely for ventilation. However, the alveoli are the main site of gas exchange in the lungs.

The diaphragm is innervated by C3-C5 (phrenic nerve). The phrenic nerve receives innervation from parts of both the cervical plexus and the brachial plexus. The phrenic nerve contains motor, sensory, and sympathetic nerve fibers, providing motor supply to the diaphragm as well as sensation to the central tendon. Pain from the diaphragm can be referred to the shoulder.

The epiglottis is a flaplike cartilaginous structure. During breathing it stands upright, allowing air to enter the larynx. However, upon swallowing the epiglottis folds downward to a more horizontal position in order to cover the opening of the windpipe. This movement directs food to the esophagus and prevents food from entering air passages.

The right lung consists of 3 lobes: the superior lobe, the middle lobe, and the inferior lobe (also known as: upper, middle, and lower lobes). The superior and middle lobes are divided by the horizontal fissure, while the middle and inferior lobes are separated by the oblique fissure. The left lung is made up of 2 lobes, the superior and inferior lobes. These are separated by the oblique fissure.