Ciliary

Low humidity also affects comfort and health. Comfort complaints about dry nose, throat, eyes, and skin occur in low-humidity conditions, typically when the dew point is less than 0 °C. Low humidity can lead to drying of the skin and mucous surfaces. On respiratory surfaces, drying can concentrate mucus to the extent that ciliary clearance and phagocytic activities are re-... 

Cilia are thin cylindrical hair-like structures with a cross-sectional radius of 0.1 gm projecting from the apical epithelial surface of ciliated columnar cells. Ciliary length is thought to correspond to periciliary fluid depth and range from approximately 7 gm in proximal airways to roughly 5 gm in more distal airways.- Each ciliated epithelial cell supports approximately 200 cilia at a density of eight cilia/gm. Short microvilli, possibly associated with secretory functions, are interspersed among the cilia. 

Nonciliated cells separate fields of ciliated epithelial cells from each other. Synchronized ciliary movement, with a beat frequency in human proximal airways under normal conditions of 8-15 EIz, propels mucus along the mucociliary escalator at a rate of up to 25 mm/min. Beat frequencies appear to slow to roughly 7 Hz in more distal airways. Cilia move in the same direction and in phase within each field but cilia in adjacent fields move in slightly different directions and are phase shifted. These beat patterns result in metachronal waves that steadily move mucus at higher velocities ( -12-18 mm/min) than would be achievable by summing the motion of individual cilia. 

Mucus gel is propelled toward the epiglottis by a two-phase ciliary beat cycle. Forward mucus movement occurs during the effective or power phase of the cycle, when cilia fully extend and traverse an arc perpendicular to the epithelial surface (Fig. 5.24). Claw-like structures, 25-35 nm long, project from each cilia tip and appear to assist in the mechanical transfer of momentum from cilia to mucus gel. Maximum mucus velocity depends on the extent cilia penetrate the epiphase during the power phase, periciliary and mucus gel viscosity, and cilia density. 

During the recovery or preparatory phase, cilia bend over, swing back to start position generally parallel to the epithelial surface, and stiffen in anticipation of the next power phase. Ciliary bending and axial movement... 

FIGURE 5.24 Components of ciliary movement, (a) Power and recovery phases of ciliary movement. Arrows indicate the direction of ciliary travel, (b) Net mucociliary transport. Dotted arrows show the direction of cilia while the solid arrows show mucus transport. Note that net gel movement is forward in I and III while no gel movement occurs in II during the cilia recovery phase. Modified from Ful-ford and Blake. ... 

Disruption of these defense mechanisms can lead to bacterial colonization or viral infection. Mucus temperature is important in controlling respiratory infections because decreasing below central body core temperature not only impairs ciliary movement,hut also enhances viral replication,- greatly increasing the likelihood of respiratory infection. Drying of airway mucus also increases the possibility of respiratory infection by reducing mucus thickness and impairing mucociliary clearance, i- i--... 

Luk, C. K., and Dulfano, M. J. (1983). Effect of pH, viscosity and ionic-.srrengtb changes on ciliary beating frequency of human bronchial explants. Clin. Sc. 64, 449-451. 

Ciliary beat frequency Rate at which cilia travel through both the power... 

Ciliary beat power phase Interval during which forward ciliary movement... 

Ciliary beat recovery phase Interval during which cilia bends and returns... 

Metachronal wave Synchronized ciliary movement over a relatively large... 

Mucociliary escalator Mechanism that removes extracellularly-derived materials from the conducting airways by entrapping these materials in mucus that is continuously moved toward the epiglottis by synchronized ciliary movement. 

Vision is vital for human activities, and eyes are very sensitive to a number of toxic insults induced by chemical compounds. The most serious outcome is permanent eye damage which may be so severe as to cause loss of vision. The eye consists of the cornea and conjunctiva, the choroid, the iris, and the ciliary body. It also contains the retina, which is of neural origin, and the optic nerve. The retina contains photoreceptors, a highly specific light-sensitive type of neural tissue. The eye also contains the lens and a small cerebrospinal fluid system, the aqueous humor system, that is important for the maintenance of the steady state of hydration of the lens and thus the transparency of the eye. 

The alkaloid is principally used in medicine to cause dilatation of the pupil of the eye (mydriasis), due to paralysis of the circular muscle of the ns. The accommodation is also paralysed as a result of action on the ciliary muscle (cycloplegia). Atropine is also used in conditions where... 

FIGURE 17.7 A mechanism for ciliary motion. The sliding motion of dyneins along one microtnbnle while attached to an adjacent microtnbnle resnlts in a bending motion of the axoneme. 

Flimmer-. ciliated, ciliary, vibrating, -messer, m. scintillometer. 

Strahlen-. pertaim ng to rays or radiation radiated, radiating Anat.) ciliary, -art,/, kind of ray or rays. 

Wimperinfusorien, /.pi. (Zodl.) CiUata. wimperad, p.a. ciliated, ciliary winking. Wind, m. wind, breeze air blast. -blSser, m. 

During COPD, the following symptoms occur, usually in the order mucus hypersecretion, ciliary dysfunction, airflow limitation, pulmonary hyperinflation, gas exchange abnormalities, pulmonary hypertension and cor pulmonale. Acute exacerbations appear to be mainly triggered by bacteria, viruses or environmental pollutants. They lead to a worsening of lung functions, wasting and increased mortality their psychosocial impacts include depression and anxiety that may be associated with the will to die. 

Some specialized eukaryotic cells have cilia that show a whiplike motion. Sperm cells move with one flagella, which is much longer than a cilium but has a nearly identical internal structure called axoneme. It is composed of nine doublet MTs that form a ring around a pair of single MTs. Numerous proteins bind to the MTs. Ciliary dynein motors generate the force by which MTs slide along each other to cause the bending of the axoneme necessary for motion. 

Sleeman MW, Anderson KD, Lambert PD et al (2000) The ciliary neurotrophic factor and its receptor, CNTFRa. Pharm Acta Helv 74 265-272... 

Radial muscle of iris 2. 5hincter muscle of iris 3. Ciliary muscle Skin Contraction (pupil dilates) a Contraction (pupil constricts) Contraction... 

FIGURE 24-1. In the normal eye, aqueous humor flows through the ciliary body into the posterior chamber, through the pupil into the anterior chamber, and out through the trabecular meshwork to the canal of Schlemm into the venous drculation. 

Cycloplegic mydriatics cause mydriasis and cyclople-gia (paralysis of the ciliary muscle, resulting in an inability to focus the eye). These drugs (see Chap. 25) are used in the treatment of inflammatory conditions of the iris and uveal tract of the eye and for examination of the eye... 

Dynein sidearms interact with the walls of B-microtubules of adjacent doublets by means of a sliding-filament mechanism to produce ciliary movement. The process is energized by ATP hydrolysis. Movement of the cilium occurs in two stages, termed the power stroke and the recovery stroke. 

Several groups of drugs that bind to tubulin at different sites interfere with its polymerization into microtubules. These drugs are of experimental and clinical importance (Bershadsky and Vasiliev, 1988). For example, colchicine, an alkaloid derived from the meadow saffron plant Colchicum autumnale or Colchicum speciosum), is the oldest and most widely studied of these drugs. It forms a molecular complex with tubulin in the cytosol pool and prevents its polymerization into microtubules. Other substances such as colcemid, podophyllotoxin, and noco-dazole bind to the tubulin molecule at the same site as colchicine and produce a similar effect, albeit with some kinetic differences. Mature ciliary microtubules are resistant to colchicine, whereas those of the mitotic spindle are very sensitive. Colchicine and colcemid block cell division in metaphase and are widely used in cytogenetic studies of cultured cells to enhance the yield of metaphase plate chromosomes. 

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