By A. Berek. Bridgewater State College.

Explain how the air got inside the thoracic cavity (assuming it did not enter through the puncture wound) cheap 4 mg aceon visa. FIGURE: The thoracic viscera and their associated serous membranes present interesting anatomical cheap aceon 8 mg with amex, functional buy aceon 8mg amex, and clinical relationships safe aceon 4 mg. Localized trauma frequently causes extensive and predictable problems elsewhere order 2 mg aceon with visa. Respiratory System © The McGraw−Hill Anatomy, Sixth Edition Body Companies, 2001 Chapter 17 Respiratory System 603 • The system must have an extensive capillary network. INTRODUCTION TO THE • The system must include an effective ventilation mecha- RESPIRATORY SYSTEM nism to constantly replenish the air. The respiratory system can be divided structurally into upper and • The system must function autonomically through effective lower divisions, and functionally into a conducting division and a monitoring and feedback mechanisms. The principal functions of the respiratory sys- also be able to function voluntarily for desired increased or tem are gaseous exchange, sound production, and assistance in decreased rates. The respiratory system adequately meets all of these requirements, Objective 1 Describe the functions associated with the term thus ensuring that all of the trillions of cells of the body will be respiration. Objective 2 Identify the organs of the respiratory system and describe their locations. Functions of the Respiratory System The four basic functions of the respiratory system, not all of Objective 3 List the functions of the respiratory system. Venti- • It assists in abdominal compression during micturition (uri- lation and the exchange of gases (oxygen and carbon dioxide) nation), defecation (passing of feces), and parturition between the air and blood are collectively called external respira- (childbirth). Gas exchange between the blood and other tissues are col- tive during a deep breath when the air is held in the lungs lectively known as internal respiration. This same A relaxed adult breathes an average of 15 times a minute, technique is used when lifting a heavy object, in which ventilating approximately 6 liters of air during this period. Strenuous exer- • It enables protective and reflexive nonbreathing air move- cise increases the demand for oxygen and increases the respira- ments, as in coughing and sneezing, to keep the air pas- tory rate fifteenfold to twentyfold, so that about 100 liters of air sageways clean. If breathing stops, a person will lose consciousness after 4 or 5 minutes. Brain damage may occur after 7 to 8 minutes, and the person will die after 10 minutes. Knowl- Basic Structure edge of the structure and function of the respiratory system is of the Respiratory System therefore of the utmost importance in a clinical setting. The major passages and structures of the respiratory system are the nasal cavity, pharynx, larynx and trachea, and the bronchi, bronchioles, and pulmonary alveoli within the lungs (fig. Physical Requirements The structures of the upper respiratory system include the of the Respiratory System nose, pharynx, and associated structures; the lower respiratory The respiratory system includes those organs and structures that system includes the larynx, trachea, bronchial tree, pulmonary function together to bring gases in contact with the blood of the alveoli, and lungs. In order to be effective, the respiratory system On the basis of general function, the respiratory system is must comply with certain physical requirements. The conducting division includes all of the cavities and • The surface for gas exchange must be located deep within structures that transport gases to and from the pulmonary alveoli. Early Greek and Roman scientists placed great emphasis on the invisible material that was breathed in. They knew nothing • The membrane must be kept moist so that oxygen and car- about oxygen or the role of the blood in transporting this vital sub- bon dioxide can be dissolved in water to facilitate diffusion. For that matter, they knew nothing about microscopic structures like cells because the microscope had not yet been in- vented. Early Greeks referred to air as an intangible, divine spirit called respiration: L. Respiratory System © The McGraw−Hill Anatomy, Sixth Edition Body Companies, 2001 604 Unit 6 Maintenance of the Body Nasal cavity Nostril Choana Hard palate Soft palate Pharynx Epiglottis Esophagus Larynx Left principal (primary) bronchus Trachea Lobar bronchus Segmental bronchus Right lung: Superior lobe Left lung: Superior lobe Middle lobe Inferior lobe Inferior lobe Cardiac impression FIGURE 17. Objective 4 List the types of epithelial tissue that characterize Knowledge Check each region of the respiratory tract and comment on the 1. What are the physical requirements of the respiratory sys- Objective 5 Identify the boundaries of the nasal cavity and tem? List in order the major passages and structures through of the respiratory system. Objective 6 Describe the three regions of the pharynx and identify the structures located in each. Objective 7 Discuss the role of the laryngeal region in digestion and respiration. CONDUCTING PASSAGES Objective 8 Identify the anatomical features of the larynx Air is conducted through the oral and nasal cavities to the phar- associated with sound production and respiration. These structures deliver warmed and humidified air to the respira- tory division within the lungs.

The con- sequently GH secretion is impaired; therefore cheap aceon 8 mg with amex, a thyroid verse occurs when the blood concentrations of T4 and T3 hormone-deficient individual will also be GH-deficient purchase aceon 4 mg with mastercard. The fact that thyroid hormones af- this condition occurs in a child buy 8mg aceon mastercard, it will cause growth retar- fect the amount of oxygen consumed by the body has been dation cheap 8mg aceon otc, largely a result of the lack of the growth-promot- used clinically to assess the status of thyroid function order 4 mg aceon with amex. This measurement is the thyroid hormones have additional effects on growth. Not all tissues are sensitive to the thermo- stimulate the synthesis of structural proteins of mitochon- genic action of thyroid hormones. Tissues and organs that dria, as well as the formation of many enzymes involved in give this response include skeletal muscle, the heart, the intermediary metabolism and oxidative phosphorylation. These are also tissues in which thy- Thyroid hormones also promote the calcification and, roid hormone receptors are abundant. The adult brain, hence, the closure, of the cartilaginous growth plates of the skin, lymphoid organs, and gonads show little thermogenic bones of the skeleton. How the thyroid hormones promote calcification adult brain, these tissues contain few thyroid hormone re- of the growth plates of bones is not understood. The thermo- Energy Economy of the Body genic action of the thyroid hormones is poorly under- stood at the molecular level. The thermogenic effect When the body is at rest, about half of the ATP produced takes many hours to appear after the administration of by its cells is used to drive energy-requiring membrane thyroid hormones to a human or animal, probably be- transport processes. The remainder is used in involuntary cause of the time required for changes in the expression muscular activity, such as respiratory movements, peri- of genes involved. T3 is known to stimulate the synthesis stalsis, contraction of the heart, and in many metabolic of cytochromes, cytochrome oxidase, and Na /K -AT- reactions requiring ATP, such as protein synthesis. This action suggests that T3 may energy required to do this work is eventually released as regulate the number of respiratory units in these cells, af- body heat. A greater rate of oxidative phosphorylation would Basal Oxygen Consumption and Body Heat Production. The major site of ATP production is the mitochondria, Thyroid hormone also stimulates the synthesis of uncou- where the oxidative phosphorylation of ADP to ATP takes pling protein-1 (UCP-1) in brown adipose tissue. The rate of oxidative phosphorylation depends on synthesized by ATP synthase in the mitochondria when pro- the supply of ADP for electron transport. UCP-1 acts is, in turn, a function of the amount of ATP used to do work. As the protons move ATP is used and more ADP is generated, increasing the rate down their electrochemical gradient uncoupled from ATP syn- of oxidative phosphorylation. Adult humans have little phosphorylation occurs is reflected in the amount of oxygen brown adipose tissue, so it is not likely that UCP-1 makes a consumed by the body because oxygen is the final electron significant contribution to nutrient oxidation or body heat acceptor at the end of the electron transport chain. However, several uncoupling proteins (UCP-2 Activities that occur when the body is not at rest, such and UCP-3) have recently been discovered in many tissues, as voluntary movements, use additional ATP for the work and their expression is regulated by thyroid hormones. Thyroid Hormones Development of CNS Inhibit nerve cell replication Thyroid Hormones Stimulate Intermediary Stimulate growth of nerve cell bodies Metabolism Stimulate branching of dendrites Stimulate rate of axon myelinization In addition to their ability to regulate the rate of basal en- Body growth Stimulate expression of gene for ergy metabolism, thyroid hormones influence the rate at GH in somatotrophs which most of the pathways of intermediary metabolism Stimulate synthesis of many operate in their target cells. When thyroid hormones are structural and enzymatic proteins deficient, pathways of carbohydrate, lipid, and protein me- Promote calcification of growth plates of bones tabolism are slowed, and their responsiveness to other reg- Basal energy economy of Regulate basal rates of oxidative ulatory factors, such as other hormones, is decreased. How- the body phosphorylation, body heat ever, these same metabolic pathways run at an abnormally production, and oxygen high rate when thyroid hormones are present in excess. The amplifying effect of thy- pathways of carbohydrate, lipid, roid hormones on intermediary metabolism is mediated and protein metabolism through the activation of genes encoding enzymes in- Thyroid-stimulating Inhibit TSH secretion by decreasing volved in these metabolic pathways. As discussed in Chapter 32, that affect certain steps in the biosynthesis of thyroid hor- T3 exerts an inhibitory effect on TSH secretion by thy- mones and hypothalamic or pituitary diseases that interfere rotrophs in the anterior pituitary gland by decreasing thy- with TRH or TSH secretion. Obviously, radioiodine abla- rotroph sensitivity to thyrotropin-releasing hormone tion or surgical removal of the thyroid gland also causes (TRH). Consequently, when the circulating concentration thyroid hormone deficiency. Hypothyroidism is the dis- of free thyroid hormones is high, thyrotrophs are relatively ease state that results from thyroid hormone deficiency. The resulting fall of TSH levels in the blood re- of most tissues in the body. As described earlier, a defi- duces the rate of thyroid hormone release from the follicu- ciency of thyroid hormones at birth that is not treated lar cells in the thyroid.

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