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Structure of the respiratory system

This system is responsible for providing the oxygen for the body and removingthe carbon dioxide from the body. In the body oxygen is required for every cellin your body.

Air needed for body is usually drawn into the body through the nose butsometimes it comes through the mouth, and passes through a network ofairways to reach the lungs. The network of airways is called the respiratorytract and is divided into two main parts. They are referred as the upperrespiratory tract, which includes such things as the nose, nasal cavity, mouthpharynx and the larynx.The other is the lower respiratory tract, which consists of the trachea, bronchiand lungs.For example for the upper respiratory tract we have the Nasal cavity.

Nasal cavity

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Overall the nose is divided the external nose and the internal nasal cavity.Once breathing the air enters the cavity by passing through the nostrils. Insidethe nose hairs filter out dust, pollen and other foreign particles.Then the air passes into two passages and this is where the air warmed andmoistened and passes into the nasopharynx. This is a sticky mucous where

layers trap smaller foreign particles and which cilia which are tiny cellstransport the pharynx to be swallowed.

Epiglottis

This is a small flap of cartilage at the back of the tongue. This closes the topof the trachea when you swallow to ensure food and drink pass into yourstomach.

Pharynx

This is a funnel shape, which connects to the nasal cavity and mouth to thelarynx and oesophagus. This is a small tube that measures the skull to thelevel of the sixth cervical vertebrae. It is composed of the skeletal muscle. Itsthe passageway for food as well as air, so certain requirements are requiredto prevent choking when food or anything else is swallowed.

Larynx

This is the voice box of the throat .It has rigid walls of the muscle and cartilagewhich contains the vocal cords and connect the pharynx to the trachea. A lotof it extends for about 5 cm from the level of the third to sixth vertebrae.

Trachea

This is located in the lower respiratory tract. It is commonly known as thetrachea and the windpipe. It contains rings of cartilage to prevent it fromcollapsing and it is very flexible. The trachea travels down the neck in front ofthe oesophagus and branches into the right and left bronchi.

Bronchus

The right and left division of the trachea forms these. It carries air out of thelungs. The right is shorter and wider than the left and is a more common sitethe air once it has reached the bronchi it becomes warm and clear. Onceinside the bronchus they are then each subdivided. Three on the right and twoon the left. The lobar bronchi branch into segmental bronchi, which is thendivided into smaller and smaller bronchi.There are approximately 23 orders of branching bronchial airways in thelungs. This is due to the branching pattern .The network in the lungs is knownas the bronchial tree.

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Bronchioles

These are small airways that extend from the bronchi. They are about 1mm indiameter and are the first airway branches of the respiratory system. Theyend in clusters of thin walled air sacs, which are known as alveoli.

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Lungs

These are paired right and left lung, which are occupying most of the thoraciccavity. They extend down to the diaphragm. The left lung is smaller than the

right.

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Lobes

Each lung is divided into lobes. The right lung has three lobes and the left hastwo.

Pleural membrane and cavity

Membranes known as pleura surround these lungs. It contains a cavity withfluid that lubricates the surfaces of the pleural and expands and contract,which prevents friction and keeping them airtight.

Thoracic cavity

In the wall it is the chamber of the chest that protects the thoracic wall. It isseparated from the abdominal cavity by the diaphragm.

Visceral pleura

This is the innermost of the two pleural membranes. It covers the surface ofthe lung and dips into the spaces between the lobes.

Pleural Fluid

These produce pleural fluid, which fill the space between them. Thelubricating fluid allows the lungs to glide easily over the thoracic wall duringthe respiration stage. During this period the separation is resisted by thesurface tension of the fluid and keeps the surface in contact with the chestwall.

Alveoli

This is the name given to the air sacs or bronchioles. A dense network ofcapillaries surrounds the alveoli to facilitate this process. With each other thealveolar and capillary walls form the respiratory membrane that has gas onone side and blood flowing past on the other. Oxygen passes from the alveoliinto the blood and carbon dioxide leaves the blood to enter the alveoli.

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Diaphragm

This separates the chest from the abdomen. This is the most importantmuscle involved in breathing. It contracts the diaphragm and increases thevolume of the chest cavity. While relaxation it involves recoil of the diaphragmand decreases the volume of the chest cavity.

Internal and intercostals muscles

These lie between the ribs. These help with the inhalation and exhalation.The internal intercostals muscles lie inside the ribcage. The ribs movedownward and inwards decreasing the volume of the chest cavity and forcingair out of the lungs.

The external intercostals muscles lie outside the ribcage. It pulls the robsupwards and outwards, increasing the volume of the chest cavity and drawingair into the lungs during respiration.