Respiratory+System+MV

Molly Vaughn 17 September 2008 Human Bio.

Respiratory System (Chapter 9) Part 1. Describe structure and function of each of these terms (in great detail...read the pages in the book from 170 to 174) in this order (the pathway of air from the nasal cavities to the lungs). Inserting a picture of your respiratory system would be nice.

Nasal cavity-The nasal cavities are narrow canals separated from each other by a septum composed of bone and cartilage. Large stiff hairs that act as a screening device, filtering the air of dust so it doesn’t enter air passages. The rest of the nasal cavities are lined by mucous membrane with a submucosa that has plentiful capillaries. These capillaries help warm and moisten the air, but they also make us more susceptible to nose bleeds if the nose suffers an injury. The mucus secreted by the mucus membrane also helps trap dust and move it to the pharynx, where it can be swallowed. The tear glands drain into the nasal cavities by way of tear ducts. The nasal cavities also communicate with the cranial sinuses, air-filled mucosa-lined spaces in the skull. If inflammation due to a cold or allergic reaction blocks the ducts leading from the sinuses, fluid may accumulate, causing a sinus headache.

Pharynx- The pharynx is a funnel-shaped passageway that connects the nasal and oral cavities to the larynx. Therefore, the pharynx, which is commonly referred to as the “throat,” has three parts: the nasopharynx, where the nasal cavities open above the soft plate; the oropharynx, where the oral cavity opens; and the laryngopharynx, which opens into the larynx. The tonsils form a protective ring at the junction of the oral cavity and the pharynx. Inhaled air passes directly over the tonsils, making them the primary lymphatic defense during breathing. In the pharynx, the air passage and the food passage cross because the larynx, which receives air, is in front of the esophagus, which receives food.

Glottis- The glottis is an opening between the vocal cords. The high or low pitch of the voice is regulated when speaking and singing by changing the tension on the vocal cords. The greater the tension, as when the glottis becomes narrower, the higher the pitch. When the glottis is wider, the pitch is lower.

Larynx- The larynx is a cartilaginous structure that serves as a passageway for air between the pharynx and the trachea. The larynx can be pictured as a triangular box whose apex, the Adam’s apple, is located at the front of the neck. The larynx is called the voice box because it houses the vocal chords. At the time of puberty, the growth of the larynx and the vocal chords is much more rapid and accentuated in the male than in the female, causing the male to have a more prominent Adams’s apple and a deeper voice. The voice “breaks” in the young male due to his inability to control the longer vocal cords. These changes cause the lower pitch of the voice in males.

Trachea- The trachea, commonly called the windpipe, is a tube connecting the larynx to the primary bronchi. Its walls consist of connective tissue and smooth muscle reinforced by C-shaped cartilaginous rings. The trachea lies ventral to the esophagus. The open part of the C-shaped rings faces the esophagus, and this allows the esophagus to expand when swallowing. The mucous membrane that lines the trachea has an outer layer of pseudostrarified ciliated columnar epithelium. It the trachea is blocked because of illness or the accidental swallowing of a foreign object, it is possible to insert a breathing tube by way of an incision made in the trachea. This tube acts as an artificial air intake and exhaust duct. The operation is called a tracheotomy.

Bronchus- The trachea divides into right and left primary bronchi (sing., bronchus), which lead into the right and left lungs. The bronchi branch into a few secondary bronchi that also branch, until the branches become about 1 mm in diameter and are called bronchioles.

Bronchioles-The bronchi resemble the trachea in structure, but as the bronchial tubes divide and subdivide, their walls become thinner, and the small rings of cartilage are no longer present. During an asthma attack, the smooth muscle of the bronchioles contracts, causing bronchiolar constriction and characteristic wheezing. Each bronchiole leads to an elongated space enclosed by a multitude of air pockets, or sacs, called alveoli. The components of the bronchiole tree beyond the primary bronchi compose the lungs.

Lung-The lungs are paired, cone-shaped organs that occupy the thoracic cavity, except for the central area that contains the trachea, the heart, and esophagus. The right lung has three lobes, and the left lung has two lobes, allowing room for the heart, which points left. A lobe is further divided into lobules, and each lobule has a bronchiole serving many alveoli. The lungs follow the contours of the thoracic cavity, including the diaphragm, the muscle that separates the thoracic cavity from the abdominal cavity. Each lung is enclosed by pleura, a double layer of serous membrane that produces serious fluid. The parietal pleura adhere to the thoracic cavity wall, and the visceral pleura adhere to the surface of the lung. Surface tension is the tendency for water molecules to cling to one another due to hydrogen bonding between molecules. Surface tension holds the two pleural layers together, and therefore, the lungs must follow the movement of the thorax when breathing occurs.

Diaphragm- In its relaxed state, the diaphragm is dome-shaped; during inspiration, it contracts and becomes a flattened sheet of muscle. Following the contraction of the diaphragm and the external intercostal muscles, the volume of the thoracic cavity will be larger than it was before.

Picture of the Respiratory System

Part 2. Describe the structure and function of alveoli in great detail. (Inserting a picture of an alveolus would be nice.) - The lungs have about 300 million alveoli, with a total cross-sectional area of 50-70 m2. Each alveolar sac is surrounded by blood capillaries. The wall of the sac and the wall of the capillaries are largely simple saquamous epithelium-think flattened cells- and this facilitates gas exchange. Gas exchange occurs between air in the alveoli and blood in the capillaries. Oxygen diffuses across the alveolar wall and enters the bloodstream, while carbon dioxide diffuses from the blood across the alveolar wall to enter the alveoli. The alveoli of human lungs are ling with a surfactant, a film of lipoprotein that lowers the surface tension of water and prevents them from closing. The lungs collapse in some newborn babies, especially premature infants, who lock this film. The condition, called infant respiratory distress syndrome, is now treatable by surfactant replacement.

Part 3. (p. 178) Describe in great detail how Carbon Dioxide is carried in the blood and how Oxygen is carried in the blood. - The principles of diffusion, alone, govern whether O2 or CO2 enters or leaves the blood in the lungs and in the tissues. Gases exert pressure, and the amount of pressure each gas exerts is called its partial pressure, symbolized as p O2 and P CO2. If the partial pressure of oxygen differs across a membrane, oxygen will diffuse from the higher to lower partial pressure.

Part 4. Describe 4 respiratory disorders of your choice (in great detail). 1. Sinusitis develops when nasal congestion blocks the tiny openings leading to the sinuses. Symptoms include postnasal discharge, as well as facial pain that worsen when the patient bends forward. Pain and tenderness usually occur over the lower forehead or over the cheeks. If the latter, toothache is also a complaint. Successful treatment depends on restoring proper drainage of the sinuses. Even a hot shower and sleeping upright can be helpful. Otherwise, spray decongestants are preferred over oral antihistamines, which thicken rather than liquefy the material trapped in the sinuses. 2. Otitis media is an infection of the middle ear. This infection is considered here because it is a complication often seen in children who have nasal infection. Infection can spread by way of auditory tube from the nasopharynx to the middle ear. Pain is the primary symptom of a middle ear infection. A sense of fullness, hearing loss, vertigo, and fever may also be present. Antibiotics are prescribed if necessary, but physicians are aware today that overuse of antibiotics can lead to resistance of bacteria to antibiotics. Tubes are sometimes placed in the eardrums of children with multiple reoccurrences to help prevent the buildup of pressure in the middle ear and the possibility of hearing loss. Normally, the tubes fall out with time. 3. Acute bronchitis is an infection of the primary and secondary bronchi. Usually, it is preceded by a viral URI that has led to a secondary bacterial infection. Most likely, a nonproductive cough has become a deep couch that expectorates mucus and perhaps pus. 4. Laryngitis is an infection of the larynx with accompanying hoarseness, leading to the inability to talk in an audible voice. Usually, laryngitis disappears with treatment of the URI. Persistent hoarseness without presence of a URI is one of the warning signs of cancer and therefore should be looked into by a physician.