Respiratory System PDF

Respiratory System cardiovascular and respiratory systems share responsibility for supplying the body with oxygen and disposing of carbon dioxide organs of the respiratory system include the nose, pharynx, larynx, trachea, bronchi and their smaller branches, and the lungs, which contain the alveo...

Respiratory System cardiovascular and respiratory systems share responsibility for supplying the body with oxygen and disposing of carbon dioxide organs of the respiratory system include the nose, pharynx, larynx, trachea, bronchi and their smaller branches, and the lungs, which contain the alveoli gas exchange with the blood happens only in the alveoli The passageways from the nose to the larynx are called the upper respiratory tract trachea to the alveoli are the lower respiratory tract These conducting passageways also purify, humidify, and warm incoming air. **Nose** - the only externally visible part of the respiratory system During breathing, air enters the nose by passing through the **nostrils**, or **nares**. divided by a midline **nasal septum**. The **olfactory receptors** for the sense of smell are located in the **mucosa** in the slitlike superior part of the nasal cavity, just beneath the ethmoid bone The rest of the mucosa lining the nasal cavity, called the respiratory mucosa, rests on a rich network of thin-walled veins that warms the air as it flows past sticky mucus produced by this mucosa's glands moistens the air and traps incoming bacteria and other foreign debris, and **lysozyme** enzymes in the mucus destroy bacteria chemically. **Conchae -** The lateral walls of the nasal cavity are uneven, owing to three mucosa-covered projections - - The nasal cavity is separated from the oral cavity below by a partition, the **palate**. **Anteriorly**, where the palate is supported by **bone**, is the **hard palate**; the **unsupported** **posterior** part is the **soft palate** **cleft palate** - failure of the bones forming the palate to fuse medially The nasal cavity is surrounded by a ring of paranasal sinuses located in the frontal, sphenoid, ethmoid, and maxillary bones. The sinuses lighten the skull and act as resonance chambers for speech. They also produce mucus which drains into the nasal cavities The nasolacrimal ducts, which drain tears from the eyes, also empty into the nasal cavities **rhinitis** - inflammation of the nasal mucosa.The excessive mucus produced results in nasal congestion and postnasal drip. **Sinusitis** - sinus inflammation, is difficult to treat and can cause marked changes in voice quality pharynx - a muscular passageway about 13 cm (5 inches) long - - - - nasopharynx from the nasal cavity and then descends through the oropharynx and laryngopharynx to enter the larynx below. Food enters the mouth, then travels the same route as air through the oropharynx and laryngopharynx. But instead of entering the larynx, food is directed into the esophagus posteriorly by a flap called the **epiglottis** **pharyngotympanic tubes** - drain the middle ears, open into the nasopharynx. The mucosae of these two regions are continuous, so ear infections such as otitis media may follow a sore throat or other types of pharyngeal infections Clusters of lymphatic tissue called **tonsils** single **pharyngeal tonsil**, often called the **adenoid**, is located high in the nasopharynx The two **palatine tonsils** are in the oropharynx at the **end of the soft palate** **lingual tonsil** - lies at the base of the tongue **tubal tonsils** protect the openings of the pharyngotympanic tubes in the nasopharynx. The tonsils also play a role in protecting the body from infection **Tonsillitis** - If the pharyngeal tonsil becomes inflamed and swollen (as during a bacterial infection), it obstructs the nasopharynx and forces the person to breathe through the mouth **larynx** - voice box, routes air and food into the proper channels and plays a role in speech - - **Epiglottis** - spoonshaped flap of elastic cartilage - - **Thyroid Cartilage** - The largest of the hyaline cartilages is the shield-shaped which protrudes anteriorly and is commonly called the **Adam's apple**. If anything other than air enters the larynx, a cough reflex is triggered to prevent the substance from continuing into the lungs **vocal folds**, or **true vocal cords**, which vibrate with expelled air. This ability of the vocal folds to vibrate allows us to speak. The slitlike passageway between the vocal folds are called the **glottis**. **Trachea** or windpipe, from the larynx travels down its length (10--12 cm, or about 4 inches) to the level of the fifth thoracic vertebra, which is approximately midchest - - - **open parts** of the rings **abut the esophagus** (the openings face posteriorly) and allow it to expand anteriorly when we swallow a large piece of food. The **solid portions** support the trachea walls and **keep it patent**, or open, in spite of the pressure changes that occur during breathing. The trachealis muscle lies next to the esophagus and completes the wall of the trachea posteriorly The **Heimlich maneuver**, a procedure in which the air in a person's own lungs is used to "pop out," or expel, an obstructing piece of food has saved many people from becoming victims of choking. Smoking inhibits and ultimately destroys the cilia. The right and left main (primary) bronchi are formed by the division of the trachea. Each main bronchus runs obliquely before it plunges into the medial depression (hilum) of the lung on its own side The right main bronchus is wider, shorter, and straighter than the left. The lungs are fairly large organs. They occupy the entire thoracic cavity except for the most central area, the mediastinum which houses the heart, the great blood vessels, bronchi, esophagus and other organs The **narrow superior portion** of each lung, the **apex**, is just deep to the clavicle. The **broad lung area** resting on the diaphragm is the **base** Each lung is divided into lobes by **fissures**; the left lung has two lobes, and the right lung has three The surface of each lung is covered with its own visceral serosa, called the pulmonary pleura or visceral pleura The **walls** of the thoracic cavity are lined by the **parietal pleura**. The **pleural membranes produce pleural flui**d, slippery serous fluid, which allows the lungs to glide easily over the thorax wall during breathing and causes the two pleural layers to cling together **Pleurisy** - inflammation of the pleurae, can be caused by insufficient secretion of pleural fluid. **The Bronchial Tree** main bronchi subdivide into smaller and smaller branches (secondary and tertiary bronchi, and so on), finally ending in the smallest of the conducting passageways, the bronchioles terminal bronchioles lead into respiratory zone structures, even smaller conduits that eventually terminate in alveoli The respiratory zone, which includes the respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli, is the only site of gas exchange All other respiratory passages are conducting zone structures that serve as conduits to and from the respiratory zone Alveolar pores connect neighboring air sacs and provide alternative routes for air to reach alveoli whose feeder bronchioles have been clogged by mucus or otherwise blocked. oxygen passes from the alveolar air into the capillary blood, and carbon dioxide leaves the blood to enter the alveoli The final line of defense for the respiratory system is in the **alveoli**. Remarkably efficient **alveolar macrophages**, sometimes called "**dust cells**," wander in and out of the alveoli picking up bacteria, carbon particles, and other debris. - **Pulmonary ventilation**. Air must move into and out of the lungs so that the gases in the alveoli of the lungs are continuously refreshed. This process of pulmonary ventilation is commonly called **breathing**. **External respiration**. Gas exchange (oxygen loading and carbon dioxide unloading) between the pulmonary blood and alveoli must take place. between the blood and the body exterior **Respiratory gas transport**. Oxygen and carbon dioxide must be transported to and from the lungs and tissue cells of the body via the bloodstream. **Internal respiration**. At systemic capillaries, gas exchange occurs between the blood and cells inside the body. This time, oxygen is unloaded from blood and CO2 is loaded. **Inspiration** When the inspiratory muscles, the diaphragm and external intercostals, contract, the size (volume) of the thoracic cavity increases **intrapulmonary volume** (the volume within the lungs) increases, the gases within the lungs spread out to fill the larger space. The resulting decrease in gas pressure in the lungs produces a partial vacuum pressure in the lungs is less than atmospheric pressure outside the body **Expiration** (exhalation) in healthy people is largely a passive process that depends more on the natural elasticity of the lungs than on muscle contraction As the intrapulmonary volume decreases, the gases inside the lungs are forced more closely together, and the intrapulmonary pressure rises to a point higher than atmospheric pressure Normally the pressure within the pleural space, the intrapleural pressure, is always negative (meaning it is lower than the pressure inside the lungs). During atelectasis, or lung collapse, the lung is useless for ventilation. Normal quiet breathing moves approximately 500 ml of air into and out of the lungs with each breath. This respiratory volume is referred to as the tidal volume (TV). The amount of air that can be taken in forcibly above the tidal volume is the inspiratory reserve volume (IRV), which is around 3,100 ml The amount of air that can be forcibly exhaled beyond tidal expiration, the expiratory reserve volume (ERV), is approximately 1,200 ml. Even after the most strenuous expiration, about 1,200 ml of air still remains in the lungs and cannot voluntarily be expelled. This is the residual volume The total amount of exchangeable air (around ,800 ml in healthy young men and 3,100 ml in healthy young women) is the **vital capacity** Dead space volume - some of the air that enters the respiratory tract remains in the conducting zone passageways and never reaches the alveoli to participate in gas exchange. Cough - - Sneeze - - Crying - - Laughing - Hiccups - - Yawn - Respiratory capacities are measured with a **spirometer** **Nonrespiratory Air Movements** are a result of reflex activity, but some may be produced voluntarily. **Respiratory Sounds** **Bronchial sounds** are produced by air rushing through the large respiratory passageways (trachea and bronchi) **Vesicular breathing sounds** occur as air fills the alveoli. The vesicular sounds are soft murmurs that resemble a muffled breeze. Blood returning from the body delivers CO2 to the lungs as it picks up O2. In the systemic circuit, blood delivers O2 to body tissues and picks up CO2. external respiration is the actual exchange of gases between the alveoli and the blood (pulmonary gas exchange), and internal respiration is the gas exchange process that occurs between the blood and the tissue cells (systemic capillary gas exchange) External Respiration - - **Gas Transport in the Blood** Oxygen is transported in the blood in two ways. Most attaches to hemoglobin molecules inside the red blood cells (RBCs) to form oxyhemoglobin Carbon dioxide is 20 times more soluble in plasma compared to oxygen. As a result, most carbon dioxide is transported in plasma as bicarbonate ion A smaller amount of the transported CO2 (between 20 and 30 percent) is carried inside the RBCs bound to hemoglobin. Carbon dioxide binds to hemoglobin at a different site from oxygen, so it does not interfere with oxygen transport. Before carbon dioxide can diffuse out of the blood into the alveoli, it must first be released from its bicarbonate ion form. bicarbonate ions must enter the red blood cells, where they combine with hydrogen ions carbonic acid. Carbonic acid quickly splits to form water and carbon dioxide, and carbon dioxide then diffuses from the blood into the alveoli. Hypoxia - inadequate oxygen delivery to body tissues Carbon monoxide poisoning- - - **Internal Respiration** Internal respiration, the exchange of gases between the blood and the tissue cells,what occurs in the lungs. In this process, oxygen leaves and carbon dioxide enters the blood In the blood, carbon dioxide combines with water to form carbonic acid, which quickly releases bicarbonate ions **Neural Regulation: Setting the Basic Rhythm** The activity of the respiratory muscles, the diaphragm and external intercostals, is regulated by nerve impulses transmitted from the brain by the **phrenic nerves** and **intercostal nerves**. Neural centers that control respiratory rhythm and depth are located mainly in the **medulla oblongata** and **pons** The medulla oblongata contains two respiratory centers - - - - During exercise, we breathe more vigorously and deeply because the brain centers send more impulses to the respiratory muscles. This respiratory pattern is called **hyperpnea** **Nonneural Factors Influencing Respiratory Rate and Depth** - - - - **Hyperventilation** is an increase in the rate and depth of breathing that exceeds the body's need to remove carbon dioxide we exhale more CO2 than we should, resulting in elevated blood pH (there is less carbonic acid) By contrast, when blood starts to become slightly alkaline, or basic, breathing slows and becomes shallow. Slower breathing allows carbon dioxide to accumulate in the blood and brings the blood pH back into the normal range. apnea - cessation of breathing, until the carbon dioxide builds up in the blood again. **chronic obstructive pulmonary diseases** **(COPD**) - - major cause of death and disability in the world \(1) Patients almost always have a history of smoking \(2) dyspnea- difficult or labored breathing, occurs and becomes progressively worse \(3) coughing and frequent pulmonary infections are common \(4) most COPD victims are hypoxic, retain carbon dioxide and have respiratory acidosis, and ultimately develop respiratory failure **chronic bronchitis** the mucosa of the lower respiratory passages becomes severely inflamed and produces excessive mucus. The pooled mucus impairs ventilation and gas exchange and dramatically increases the risk of lung infections, including pneumonias. **emphysema** the walls of some alveoli are destroyed, causing the remaining alveoli to be enlarged. In addition, chronic inflammation promotes fibrosis (scarring) of the lungs. As the lungs become less elastic, the airways collapse during expiration and obstruct outflow of air The three most common types of lung cancer are \(1) adenocarcinoma (40 percent of cases), which originates as solitary nodules in peripheral lung areas and develops from bronchial glands and alveolar cell \(2) squamous cell carcinoma (25-- 30 percent), which arises in the epithelium of the larger bronchi and tends to form masses that hollow out and bleed \(3) small cell carcinoma(about 20 percent), which contains lymphocyte-like cells that originate in the main bronchi and grow aggressively in small grapelike clusters within the mediastinum, a site from which metastasis is especially rapid. **surfactant** - - - **infant respiratory distress syndrome (IRDS**). - - **Cystic Fibrosis** - - - - The respiratory rate is highest in newborn infants, about 40 to 80 respirations per minute In **sudden infant death syndrome (SIDS),** also called crib death, apparently healthy infants stop breathing and die in their sleep. **sleep apnea** increases as we age. It can occur when throat muscles relax, blocking the airway, or when signals to the respiratory muscles are improperly delivered or not delivered at all