Frumil

By F. Will. Gwynedd-Mercy College.

List the paired and unpaired cartilages of the larynx and the functional units of the respiratory system generic frumil 5mg fast delivery. Describe the structure of the conducting airways from the surface area (60–80 square meters, or 760 square feet) for the diffu- trachea to the terminal bronchioles. The diffusion rate is further increased by the fact that the wall of each pulmonary alveolus is only one cell layer thick, so that the total air-blood barrier is only one pulmonary alveolar cell with its basement membrane and one blood capillary cell across, or PULMONARY ALVEOLI, about 2 micrometers. This is an average distance because type II alveolar cells are thicker than type I alveolar cells (fig. LUNGS, AND PLEURAE Type I alveolar cells permit diffusion, and type II alveolar cells Pulmonary alveoli are the functional units of the lungs, where gas (septal cells) secrete a substance called surfactant that reduces the exchange occurs. Right and left lungs are separately contained in tendency for pulmonary alveoli to collapse. Pulmonary alveoli are polyhedral in shape and are usually clustered together, like the units of a honeycomb, in the alveolar Objective 9 Describe the structure and function of the sacs at the ends of the alveolar ducts (fig. Objective 10 Describe the surface anatomy of the lungs in relation to the thorax. Respiratory System © The McGraw−Hill Anatomy, Sixth Edition Body Companies, 2001 Chapter 17 Respiratory System 613 Blood flow Pulmonary venule Capillary network on surface of Pulmonary arteriole pulmonary alveolus Pulmonary venule Bronchiole Smooth muscle Pulmonary Terminal arteriole bronchiole Respiratory bronchiole Alveolar duct Alveolar sac Pulmonary alveoli FIGURE 17. The respiratory tubes end in pulmonary alveoli, each of which is surrounded by an extensive pulmonary capillary network. Fluid with surfactant Type I alveolar cell Type II alveolar cell Pulmonary alveolus White blood cell Macrophage Red blood cell Alveolar sacs Pulmonary alveoli FIGURE 17. Respiratory System © The McGraw−Hill Anatomy, Sixth Edition Body Companies, 2001 614 Unit 6 Maintenance of the Body Thyroid cartilage Cricoid cartilage Trachea Clavicle Apex of left lung Scapula Superior lobe of left lung Superior lobe of right lung Sternum Middle lobe of right lung Cardiac impression Inferior lobe of right lung Inferior lobe of left lung Base of left lung Costal cartilage Creek FIGURE 17. The superior surface, called the apex (cupola) of the lung, extends above the level of the clavicle. Finally, the broad, rounded sur- Lungs face in contact with the membranes covering the ribs is called The large, spongy lungs are paired organs within the thoracic cav- the costal surface of the lung. Each lung extends from the diaphragm to a point Although the right and left lungs are basically similar, they just above the clavicle, and its surfaces are bordered by the ribs to are not identical.

Under such conditions generic frumil 5 mg without a prescription, proteins are several physiological mechanisms come into play to in- broken down into amino acids that provide energy for con- crease the blood supply (and, thus, the oxygen) to the traction and that can be resynthesized into glucose to meet working muscle. The gly- ing energy for contraction and the recycling of metabolites colytic pathway can continue to operate because the ex- (e. In addition to its oxygen- and formation of lactic acid, by preventing a buildup of pyru- carbon dioxide-carrying functions, the enhanced blood vic acid, also allows for the restoration of the enzyme supply to exercising muscle provides for a rapid exchange cofactor NAD , needed for a critical step in the gly- of essential metabolic materials and the removal of heat. Thus, ATP can continue to be produced under Those muscles adapted for mostly aerobic metabolism anaerobic conditions. This The accumulation of lactic acid is the largest contributor iron-containing molecule, essentially a monomeric form of (more than 60%) to oxygen deficit, which allows short-term the blood protein hemoglobin (see Chapter 11), gives aer- anaerobic metabolism to take place despite a relative lack of obic muscles their characteristic red color. Other depleted muscle oxygen stores have a smaller gen storage capacity of myoglobin is quite low, and it does capacity but can still participate in oxygen deficit. The largest not make a significant direct contribution to the cellular of these is the creatine phosphate pool (approximately 25%). Chapters 9 and 10 ATP levels return to normal, the energy stored in the crea- discuss metabolic adaptations that are specific to skeletal, tine phosphate energy pool is also replenished. REVIEW QUESTIONS DIRECTIONS: Each of the numbered (C) Maintain the separation of thick stretched beyond its optimal length items or incomplete statements in this and thin filaments when the muscle is (but not to the point where damage section is followed by answers or at rest occurs), the reduction in contractile completions of the statement. Select the (D) Promote the binding of calcium force is due to ONE lettered answer or completion that is ions to the regulatory proteins (A) Lengthening of the myofilaments so BEST in each case. Calcium ions are required for the that crossbridges become spaced farther normal activation of all muscle types. Skeletal, smooth, and cardiac muscle Which statement below most closely (B) Decreased overlap between thick all have which of the following in describes the role of calcium ions in and thin filaments, which reduces the common? During the shortening of skeletal filaments action potential muscle, (D) A high concentration of calcium (B) A rapid release of calcium from its (A) The distance between Z lines stays ions in the myofilament space is storage sites in the T tubules the same required to maintain muscle in a (C) A rapid release of calcium from the (B) The width of the I band changes relaxed state. The normal process of relaxation in reticulum (D) All internal spacings between skeletal muscle depends on (D) A release of calcium that is bound repeating structures change (A) A sudden reduction in the amount to cytoplasmic proteins in the region proportionately of ATP available for the crossbridge of the myofilaments 3. The relaxation of skeletal muscle is energy for muscle contraction during (B) Metabolically supported pumping associated with a reduction in free the crossbridge cycle.

After oral administration alone most dopa is rapidly decarboxylated to DA in the gut and blood with some o-methylated (COMT) to o-methyl/dopa (OMD) generic 5mg frumil with mastercard. Blocking just the peripheral dopa decarboxylase (DD) with inhibitors like carbidopa and benserazide, that cannot enter the CNS (extra cerebral dopa decarboxylase inhibitors, ExCDDIs), stops the conversion of levodopa to DA peripherally, so that more enters the CNS or is o-methylated peripherally to OMD. The deamination of DA to DOPAC can be prevented by MAOB inhibitors such as selegiline while COMT inhibitors stop its further o-methylation to HVA and the conversion of dopa to OMD. COMT inhibitors can act just peripherally (entacapone) or in the CNS as well (tolcapone). DD Ð dopa decarboxylase; MAO Ð monoamine oxidase; COMT Ð catechol-o- methyl transferase raise BP. In fact DA synthesis is favoured, since dopa decarboxylase is widely distri- buted and never saturated, but further synthesis to NA is limited by the restriction of dopamine B-hydroxylase to vesicles in NA nerve terminals. Fortunately Cotzias and his colleagues (1967), after finding that large doses of levodopa (in excess of 3 g) were effective in South American miners suffering from manganese poisoning and showing symptoms akin to PD, tried them successfully in Parkinsonism patients. It is generally accepted that the improvement is very good in 35% of patients, good in 30% and moderate in 30% with some (55%) not really responding. Indeed its effect is so dramatic that the validity of PD diagnosis in the non- responders is questioned. DISEASES OF THE BASAL GANGLIA 307 It is not the object of this text to cover the detailed pharmacology and use of drugs but levodopa must be an exception. Its use in PD illustrates the problems that still have to be overcome even after the cause of a disease of the CNS has been established and a treatment devised. Mode of action Levodopa itself has virtually no affinity for DA receptors and if its conversion to DA is stopped by inhibiting its decarboxylation in the brain then it has no behavioural (DA-like) effects in animals. More importantly, it loses its efficacy in primates with experimental (MPTP) Parkinsonism. Unfortunately most of the DA nerves that would normally do that in the striatum have degenerated and the remainder are already working overtime.