Respiratory System. Student Learning Objectives:

Transcription

1 Respiratory System Student Learning Objectives: Identify the primary structures of the respiratory system. Identify the major air volumes associated with ventilation. Structures to be studied: Respiratory structures: External nares Nasal cavity Nasal conchae Pharynx Larynx Thyroid cartilage Cricoid cartilage Arytenoid cartilage Epiglottis Trachea Bronchus Lung Bronchioles Alveoli Diaphragm Air Volumes: Tidal volume Inspiratory reserve volume Expiratory reserve volume Vital capacity Residual volume Introduction The respiratory system consists of the upper and lower airways. The upper airways begin in the nasal cavity and extend through the throat region. A cold usually affects these structures leading to symptoms of stuffy nose and scratchy throat. The lower airways begin at the larynx and extend to the alveoli. Conditions such as pneumonia and bronchitis are common ailments affecting these structures. The respiratory system plays a vital role in the body. Oxygen is a necessary ingredient in the process of cellular respiration which the cells use to manufacture the energy storage molecule called ATP. During this cellular respiration process, carbon dioxide is produced as a waste product during this process. The respiratory system and circulatory system work closely together to ensure that these materials are delivered to the appropriate places. The pulmonic circulation transports blood to the lungs where carbon dioxide will be dispose of into the air and oxygen will be picked up. The systemic circulation delivers oxygen to and picks up carbon dioxide from the tissues. The lungs serve as the site of exchange between the blood and the environment. Ventilation, the process of breathing, helps to move the air into and out of the lungs. Within the tiny airsacs of the lungs, the process of respiration occurs. During respiration, diffusion moves gases across epithelial membranes into and out of the blood supply.

2 During this anatomy exercise, you will examine the structures of the respiratory system and look at the role that each plays in this system s function in the body. We will also look at the various air volumes associated with the ventilation process. Your discussion of ventilation and respiration will occur exclusively in the lecture. Respiratory System Organs The upper airways begin at the external nares, more commonly known as the nostrils. These openings allow air to enter into the body. The air enters into one of two nasal cavities. The left and right nasal cavities are separated by a bone and cartilage wall known as the nasal septum which cannot be seen on this picture. Three bony shelf-like structures, the nasal conchae, project from the lateral wall of each nasal cavity. Each of these bony scrolls is covered by a mucous membrane which helps to warm and humidify the air as it passes through the nasal cavity. In addition, to adding heat and moisture to the air, mucus produced by these membranes traps large debris particles and filters the air as it passes through the nasal cavities. Mucus secretions from the paranasal sinuses assist with the humidification and filtering processes. These sinuses are large chambers in the maxilla, ethomoid, sphenoid, and frontal bones. Air exits the nasal cavities through small holes at the back of the cavity which open into the pharynx. The pharynx is more commonly known as the throat. This area is shared by several organ systems: the respiratory and the digestive systems. This creates some problems when both the systems want to use the space at the same time! During swallowing, breathing is temporarily halted until the food materials clear the pharynx region. Because of the huge exposure of the pharynx to the environment, there are a large number of lymphatic structures (primarily tonsils) in this region, as well.

3 As enters the lower airways, it passes through the larynx. The larynx is the beginning of a series of tubular structures composed of cartilage lined by epithelial tissue. The main component of the larynx is a large piece of cartilage that covers the anterior portion of the larynx called the thyroid cartilage. This can be felt in the upper neck area, just under the chin. In males the thyroid cartilage enlarges under the influence of testosterone and is sometimes referred to as the Adam s apple. The thyroid cartilage anchors onto the hyoid bone which is attached by muscles to the pharynx region. You looked at the hyoid bone in the anatomy exercise associated with the skeleton earlier this semester. Inferior to the thyroid cartilage is a ring of cartilage known as the cricoid cartilage. Because this cartilage completely encircles the airway, it can cause problems with airway obstructions if materials become lodge in the ring. This can lead to choking. The epiglottis is a flap of cartilage that is attached at only one end. This structure helps to cover over the airways during swallowing, preventing food materials from entering. The trough-like shape of the epiglottis directs food to the posterior pharynx and the esophagus. When the larynx is viewed from behind, parts of thyroid cartilage, cricoid cartilage, and epiglottis can again be seen. From the posterior view, you can also see the other main cartilages of the larynx: the arytenoids cartilages. These triangular pieces of cartilage attach to the vocal cords and are involved in the production of sounds. Movement of the arytenoids cartilages changes the tension on the fibrous vocal cords leading to the production of sounds that are of different pitches. In the male, because of the enlargement of the larynx caused by testosterone, the pitch of the sound is much lower than in the female.

4 When viewed from the top, the thyroid cartilage, cricoid cartilage, epiglottis, and arytenoids cartilages are once again in view. From this superior view, however, you can also see the vocal cords (represented by brown leather in the picture) and the glottis. The glottis is the space between the vocal cords through which the air passes. During choking, food materials enter into the glottis and become trapped when they try to pass through the opening in the cricoid cartilage. As air leaves the larynx, it enters into the trachea which leads into the thoracic cavity. The trachea contains a series of C- shaped cartilage pieces connected by a fibrous band on the posterior surface and muscles between the cartilages. Anterior and posterior views of the trachea can be seen in the pictures on the previous page. Posterior to the heart, near the center of the thoracic cavity, the trachea branches into two bronchi. Each bronchus travels to the lung where it branches into smaller and smaller tubes, much like the branching of a tree from the trunk. Near the ends of the smaller bronchi are tubes called bronchioles. These tiny tubes can dilate and constrict to control air flow within the lung tissue. At the end of the bronchioles are the alveoli. These rounded, balloon-like airsacs are the site of external respiration, gas exchange between the blood and the air. The microscopic bronchioles and alveoli cannot be seen on the pictures. The lungs consist of the branches of the bronchi, the bronchioles, and the alveoli. Because the heart occupies a portion of the left thorax, the right lung is larger than the left lung. The right lung has 3 lobes, or sections, while the left has only two. The diaphragm is a large muscular sheet that separates the thorax from the abdomen. This lies inferior to the lungs and helps with the process of ventilation.

5 Air Volumes Depending upon the kind of activity that you are engaging in, the amount of air that enters and leaves your lungs during ventilation can change quite dramatically. If you are merely sitting in a chair watching TV, the amount of air you need is very small. If, you are trying to blow out your birthday candles, however, a significantly larger volume of air will be needed. (Some of us require more air than we are capable of moving ) Respiratory diseases such as asthma, emphysema, and pneumonia can adversely affect the amount of air that you are able to move into and out of your lungs. Below is a chart that summarizes the various air volumes that might be studied in the medical setting. A spirometer is an instrument that is used to measure air volumes. Individuals with respiratory disease may be asked to perform a breathing test using a spirometer. The material associated with air volumes is being provided to assist you with lecture and your future coursework, but you will not be tested on this material for the respiratory quiz. Air Volume Description Amount of air moved Tidal Volume Amount of air moved during a typical breath. 500 ml Involves contraction of thoracic muscles and the diaphragm. Inspiratory reserve volume Amount of extra air that can be inhaled after the normal inhalation. Requires contraction ml Expiratory reserve volume Vital capacity Residual volume Total lung volume of additional thoracic muscles. Extra amount of air that could be removed from the lungs after the normal exhalation. Requires contraction of additional muscles, especially abdominal muscles. Largest volume of air that can be moved by the lungs. Involves maximum inhalation to maximum exhalation. Volume of air that still remains in the lungs even after a maximum exhalation. This air helps to keep the lungs inflated and attached to the thoracic wall making ventilation easier. Maximum amount of air that the lungs can hold (total of vital and residual capacities) ml ml ml ml