RESPIRATORY SYSTEM

           the job of respiratory system is to keep the body constantly supplied with oxygen and to remove carbon dioxide. The respiratory system consists of the nasal passages, pharynx, larynx, trachea, bronchi and lung. Within the lungs are tiny air sacs. It is though the thin walls of these air sacs that gas exchanges are made to and from the blood.

The Nasal Cavities- Air makes its initial entrance into the body through the openings in the nose called the nostrils. Immediately inside the nostrils, located between the roof of the mouth and the cranium, are the two spaces known as the nasal cavities. These two spaces are separated from each other by a

Partition, the nasal septum. The septum and the walls of the nasal cavities are constructed of bone covered with mucous membrane. From the lateral (side) walls of each nasal cavity are three projections called the conchae. The conchae greatly increase the surface over winch air must travel on its way

Through the nasal cavities.

The Pharynx- The muscular pharynx (throat) carries air into the respiratory tract and foods and liquids into the digestive system. The upper portion located immediately behind the nasal cavity is

Called the nasopharynx, the middle section located behind the mouth is called the oropharynx, and the lowest portion is called the laryngeal pharynx. This last section opens into the larynx toward the front and into the oesophagus toward the back.

The Larynx- The larynx (voice box) is located between the pharynx and the trachea. It has a framework of cartilage that protrudes in the front of the neck and sometimes is referred to as the Adam’s

Apple. The larynx is considerably larger in the male than in the female; hence, the Adam’s apple is much more prominent in the male. At the upper end of the larynx are the vocal cords, which serve in the production of speech. They are set into vibration by the flow of air from the lungs. A difference in the

Size of the larynx is what accounts for the difference between the male and female voices; because a man’s larynx is larger than a woman’s, his voice is lower in pitch. The nasal cavities,

The sinuses and the pharynx all serve as resonating chambers for speech, just as the cabinet does for a stereo speaker. The space between these two vocal cords is called the glottis,

And the little leaf-shaped cartilage that covers the larynx during swallowing is called the epiglottis. The epiglottis helps keep food out of the remainder of the respiratory tract. As the

Larynx moves upward and forward during swallowing, the epiglottis moves downward, covering the opening into the larynx. You can feel the larynx move upward toward the epiglottis during this process by placing the flat ends of your fingers on your larynx as you swallow. The larynx is lined with ciliated mucous membrane. The cilia trap dust and other particles, moving them upward to the pharynx to be expelled by coughing, sneezing, or blowing the nose.

The Trachea (Windpipe) -The trachea is a tube that extends from the lower edge of the larynx to the upper part of the chest above the heart. It has a framework of cartilages to keep it open. These cartilages, shaped somewhat like a tiny horseshoe or the letter C, are found along the entire length of the trachea. All the open

Sections of these cartilages are at the back so that the esophagus can bulge into this section during swallowing. The purpose of the trachea is to conduct air between the larynx

And the lungs.

The Bronchi and Bronchioles -The trachea divides into two bronchi which enter the lungs. The right bronchus is considerably larger in diameter than the left and extends downward in a more vertical direction. Therefore, if a foreign body is inhaled, it is likely to enter the right lung. Each bronchus enters the lung at a notch or depression called the hilus or hilum. The blood vessels and nerves also connect with the lung in this region

The Lungs -The lungs are the organs in which external respiration takes place through the extremely thin and delicate lung tissues. The two lungs, set side by side in the thoracic cavity, are constructed in the following manner:

Each bronchus enters the lung at the hilus and immediately subdivides. Because the subdivision of the bronchi resembles the branches of a tree, they have been given the common name bronchial tree. The bronchi subdivide again and again, forming progressively smaller divisions, the smallest of which

Are called bronchioles. The bronchi contain small bits of cartilage, which give firmness to the walls and serve to hold the passageways open so that air can pass in and out easily. However, as the bronchi become smaller, the cartilage decreases in amount. In the bronchioles there is no cartilage at all; what remains is mostly smoothly muscle, which is under the control of the autonomic nervous system. At the end of each of the smallest subdivisions of the bronchial tree, called terminal bronchioles, is a cluster of air sacs, resembling a bunch of grapes. These sacs are known as alveoli. Each alveolus is a single-cell layer of squamous (flat) epithelium. This very thin wall provides easy passage for the gases entering and leaving the blood as it circulates through millions of tiny capillaries of the alveoli. Certain cells

In the alveolar wall produce surfactant, a substance that prevents the alveoli from collapsing by reducing the surface tension (“pull”) of the fluids that line them. There are millions of alveoli in the human lung. Because of the many air spaces, the lung is light in weight; normally a piece of lung tissue

Dropped into a glass of water will float.

PREPARED BY: HAZEL MAE VILLEJO MW 2:30-4:00