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The Respiratory System of Human
The respiratory system are made up of those tubes that transport air in and out of the lungs, and microscopic sack where gasses are exchanged. Breathing is the taking in of air (oxygen) into the lungs and the taking carbon dioxide out of the lungs, the gas transport in blood between the lungs and body cell, and the gas exchange between blood and the cells are called internal respiration. While the gas exchange between the blood and air in the lungs is called external respiration. All these process of gas exchange between the atmosphere and the cells is called respiration.
The organs of respiration can be divided into two portions, the upper respiratory tracts, and the lower respiratory tract. The upper respiratory tract includes the nose, nasal cavity, and pharynx while the lower respiratory tract include the larynx, trachea, bronchial tree, and lungs.
Bones and cartilage support the nose internally. It consist of two nostrils, an opening through which air enters and leaves the nose. The nostrils contains some air that filters and prevent the entrance of large particles in the air into the lungs.
This is a hollow space posterior to the nose. The nasal cavity are separated into left and right by septum. A nasal conchae are bones and cartilage that divides the nasal cavity into passageways, it also support the mucous membrane that lines the nasal cavity. As air passes over the mucous membrane, heat leaves the blood and warms the air adjusting the air's temperature to that of the body. The air and mucous lining the nasal cavity help to trap dust and other environmental contaminant from entering the inner portion of the body. Air coming in are moistened as water evaporates from the mucous lining.
The pharynx or throat is located posterior to the oral cavity, the nasal cavity, and the larynx. This is an opening or passageway for air passing between the nasal cavity and larynx. The pharynx is divided into three main portion, the nasopharynx, oropharynx, and the laryngopharynx. Another function of the pharynx is that it is the passageway for food coming from the oral cavity to the esophagus and it also help to produce sounds of speech.
This is an enlargement in the airway. The larynx is composed of a framework or muscles and cartilages, the largest cartilage are the thyroid also known as Adams apple, cricoid, and epiglottis cartilage. The larynx connects the laryngopharynx and the trachea. It conducts air in and out of the trachea and prevents foreign object from entering the trachea. The larynx also houses the vocal folds, which allows the body to produce speech and singing. The vocal folds are divided into two pairs of horizontal vocal folds composing of muscle tissue and connective tissue, the false vocal fold and the true vocal fold. The upper false vocal fold do not produce sound; the muscle fibers within them mainly help close the airway during swallowing, while the true vocal fold vibrates to produce sound. Contracting or relaxing muscles that alter the tension on the vocal cords, controls the pitch of a sound.
The trachea also known as windpipe of about 2.5 centimeters in diameter and 12.5 centimeters in length is a cylindrical tube. The trachea extends downward anterior to the esophagus and into the thoracic cavity, where it splits into right and left bronchi. It connects the larynx to the bronchi and allows the passage of air through the neck into the thorax. The inner wall of the trachea is lined with a ciliated mucous membrane containing many goblet. This membrane filters incoming air and entrap large particles upward into the pharynx where the mucous can be swallowed and digested. Within the trachea is made up of about twenty C-shaped hyaline cartilage ring. The open ends of the rings are directed posteriorly towards the esophagus, prevents the trachea from collapsing and blocking the airway. The soft tissue that complete the rings in the back allowing the esophagus to expand accumulates food moving through the esophagus to the stomach.
The bronchial tree consist of branched airways extending from the trachea to the microscopic air sacs in the lungs. its branches starts with the right and left primary bronchi, this two primary bronchi further divides into secondary bronchi which then turn-split into the tertiary bronchi and then into bronchioles that continue to divide, giving rise to terminal bronchioles, respiratory bronchioles and finally to a thin tube called the alveolar ducts. The alveolar duct leads to a thin walled out- pouching called alveolar sacs, which also lead to smaller microscopic air sacs called alveoli. The structure of the bronchus is similar to that of the trachea, but the tubes that branch from it have less cartilage in their wall, also bronchioles lack cartilage. The presence of smooth muscle surrounding the tube becomes more prominent and allows the smaller bronchi, and bronchioles to become more flexible. The bronchi carries air from the trachea into the lungs. The branches of the bronchial tree are air passages, which filters incoming air, and distribute the air to alveoli throughout the lungs. Oxygen diffuses through alveolar walls and enters the blood in nearby capillaries, and carbon dioxide diffuses from the blood through the walls and enters the alveoli.
The lungs are soft spongy, organ found in the thoracic cavity. The lungs are separated into right and left by mediastinum, while the diaphragm and the thoracic cage encloses them. The left and right lungs are slightly different in shape, the left lung consist of two lobes while the right lung consist of three lobes. The difference in the number of lobes on the left lung is due to the space occupied by the heart. The wall of the lungs are lined with a membrane called the parietal pleura while the lung itself is covered with a membrane called the visceral pleura. The pleural cavity contains a thin film of serous fluid that lubricate and reduces friction as the lungs move against one another during breathing.
Breathing or ventilation is the movement of air from the outside the body into the bronchial tree (inspiration or inhalation) and the movement of air out of the bronchial tree to the outside (expiration or exhalation).
INSPIRATION: atmospheric pressure is the force that moves air into the lungs. At sea level, the atmospheric pressure is sufficient to support a column of mercury about 760 millimeters high in a tube. Air pressure is exerted on all surfaces in contact with the air, and because we breathe air the inside surface of our lungs are subjected to pressure. If the pressure inside the lungs and alveoli decreases, atmospheric pressure will push outside air into the airways.in summary, surface tension aid lung expansion.
EXPIRATION: the force for expiration come from the elastic recoil of tissue and from surface tension. the lungs and thoracic wall contain considerable elastic tissue, as the diaphragm lowers, it compresses the abdominal organs beneath it.as the diaphragm and external intercostal muscle relax after inspiration, the elastic tissue cause the lungs and thoracic cage to recoil and return to the original shape. Similarly, the abdominal organ spring back into their previous shapes, thereby pushing the diaphragm upward.in summary, the abdominal wall, and thoracic muscle aid expiration.