BIOLOGY ASSIGNMENT

Biology Assignment



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Biology Assignment

The structure of the respiratory system

The human respiratory system is composed of the nasal passage, the pharynx, larynx, the trachea, bronchi and lungs. It is responsible for the process of respiration that is vital to the survival of living beings. Respiration is the process of obtaining and using oxygen, while eliminating carbon dioxide. It is the process by which human beings take in the oxygen from their environment and give out the carbon dioxide that is produced as a result of chemical reactions within the cells.

Nasal passages: Air entering from the nostrils is led to the nasal passages. The nasal cavity that is located behind the nose comprises the nasal passages that form an important part of the respiratory system in human beings. The nasal cavity is responsible for conditioning the air that is received by the nose. The process of conditioning involves warming or cooling the air received by the nose, removing dust particles from it and also moistening it, before it enters the pharynx.

Pharynx: It is located behind the nasal cavity and above the larynx. It is also a part of the digestive system of the human body. Food as well as air passes through the pharynx.

Larynx: It is associated with the production of sound. It consists of two pairs of membranes. Air causes the vocal cords to vibrate, thus producing sound. The larynx is situated in the neck of mammals and plays a vital role in the protection of the trachea.

Trachea: The term refers to the airway through which respiratory air travels. The rings of cartilage within its walls keep the trachea open.

Bronchi: The trachea divided into two main bronchi. The bronchi extend into the lungs spreading in a tree-like manner as bronchial tubes. The bronchial tubes subdivide and with each subdivision, their walls get thinner. This dividing of the bronchi into thin-walled tubes results in the formation of bronchioles. The bronchioles terminate in small air chambers, each of which contains cavities known as alveoli. Alveoli have thin walls, which form the respiratory surface. The exchange of gases between the blood and the air takes place through these walls.

Lungs: Lungs form the most vital component of the human respiratory system. They are located on the two sides of the heart. They are responsible for transporting oxygen from the atmosphere into blood and releasing carbon dioxide from blood to the atmosphere.

The Mechanics of Breathing

The action of breathing in and out is due to changes of pressure within the thorax, in comparison with the outside. This action is also known as external respiration. When we inhale the intercostal muscles (between the ribs) and diaphragm contract to expand the chest cavity

The diaphragm flattens and moves downwards and the intercostal muscles move the rib cage upwards and out. This increase in size decreases the internal air pressure and so air from the outside (at a now higher pressure that inside the thorax) rushes into the lungs to equalise the pressures. When we exhale the diaphragm and intercostal muscles ...