The Howler Monkey (Mycetes) is a genus of South American monkey characterized by a remarkable loudness of voice, which is due to the presence of a large chamber within the hyoid bone and the enlargement of the ventricles of the larynx. They are prehensile-tailed, large and heavy of body with a high pyramidal head flattened on the summit. Research Howler Monkey
Androgen is a term embracing any of the male sex hormones, substances that induce and maintain secondary sex characteristics in males. The principal androgens are testosterone and androsterone. They are found in the male testes and adrenal glands, in which they are produced; in the blood, in which they circulate; and in the urine, in which they are excreted. Androgens function principally, beginning at puberty, in the stimulation of such secondary sex characteristics as development of the genital organs and maturation of sperm, growth of body hair, and changes in the larynx that lower the voice. They also account for the growth of muscle mass and bonetissue in the developing male. Research Androgen
Aphonia is the greater or less impairment, or the complete loss of the power of emitting vocal sound. The slightest and less permanent forms often arise from extreme nervousness, fright, and hysteria. Slight forms of structural aphonia are of a catarrhal nature, resulting from more or less congestion and tumefaction of the mucous and submucous tissues of the larynx and adjoining parts. Severer cases are frequently occasioned by serous infiltration into the submucous tissue, with or without inflammation of the mucousmembrane of the larynx and of its vicinity. The voice may also be affected in different degrees by inflammatory affections of the fauces and tonsils; by tumours in these situations; by morbid growths pressing on or implicating the larynx or trachea; by aneurisms; and most frequently by chronic laryngitis and its consequences, especially thickening, ulceration, etc. Research Aphonia
During swallowing, the aryepiglottis muscle draws the epiglottis downward to close the larynx, preventing food and drink from being inhaled. It originates from the arytenoid cartilage and inserts in the epiglottic cartilage near the thyroepiglotic ligament. It is innervated by the laryngeal branch of the vagus nerve. Research Aryepiglottis
The arytenoid cartilages are two small, upward protrusions located at the back of the larynx. They pivot on the ring-like cricoid cartilage and are attached to it by the cricoarytenoid muscles. The vocal cords are attached to the arytenoid cartilages, from which they span across the larynx to part of the thyroidcartilage on the other side. By flexing or relaxing the cricoarytenoid muscles, the arytenoid cartilages are forced to pivot, causing the vocal cords to be brought together for speech or separated, for breathing. The vocal and cricothyroid muscles then control their tension. This variable tension in the vocal cords allows a wide range of tones to be produced from them. Research Arytenoid Cartilages
Cartilage, or gristle, is a firm and very elastic substance occurring in vertebrate animals. When cut, the surface is uniform, and contains no visible cells, cavities, nor pores, but resembles the section of a piece of glue. It enters into the composition of parts whose functions require the combination of firmness with pliancy and flexibility, the preservation of a certain external form with the power of yielding to external force or pressure. The ends of bones entering into the formation of a joint are always coated with cartilage. Temporary cartilages are those from which bones are formed by ossification. The permanent cartilages are of various kinds. They are found in the external ear and aid in forming the nose, the larynx, etc. Research Cartilage
A cough is a sudden and forcible expiration immediately preceded by closure of the glottis or narrowed portion of the box of the windpipe. The force for the action is obtained by a deep breath, then follows the closure of the glottis, succeeded by the expiratory effort forcing open the glottis. The action is performed by the expiratory muscles, that is the abdominal muscles, by whose contraction the diaphragm is forced up, and the muscles of the chest, by which the ribs are pulled down. The cavity of the chest being thus diminished air is driven out of the lungs.
The object of the cough is usually to expel any foreign material in the lungs or air-tubes. The offending material may be there present as the result of inflammation, catarrh, etc. It may also have gained entrance from without. Thus the irritating material may be merely some food or drink which has slipped into the larynx, or it may be dust, etc, in the air inhaled, and the cough is the means of expelling the intruder. But a cough may also be produced when there is no irritating material present. The larnyx or windpipe may be in an inflamed and irritable condition, in which state even the entrance of cold air will excite coughing. Moreover, cough may be produced by irritation of nerves, distant from the lungs and air-passages, by what is called reflex action. Thus irritation of the stomach, irritation connected with the ear, irritation of certain nerves by pressure of growths, etc, may produce a cough, when the respiratory organs are not directly affected at all. Irritation at the back of the throat, as of the tickling of a long uvula, and so on, also produces it. Research Cough
The important muscular structures of the larynx include the vocal muscles, the lateral and posterior cricoarytenoid muscles, and the oblique and vertical cricothyroid muscles. The vocal muscles extend along each vocal cord and help adjust their tension, controlling vocal tone. The lateral and posterior cricoarytenoid muscles help pivot the arytenoid cartilages, bringing the vocal cords together for speech and separating the vocal cords to open the glottis for breathing. The lateral cricoarytenoid and posterior cricoarytenoid muscles are innervated by the inferior laryngeal nerve, a branch of the vagus nerve. They are supplied by the inferior and superior laryngeal arteries. The cricothyroid muscles help regulate vocal cord tension in conjunction with the vocal muscles. It is innervated by the external branch of the superior laryngeal nerve, which is a branch of the vagus nerve. The cricothyroid muscle is supplied by the inferior and superior laryngeal arteries. Research Cricoarytenoid Muscles
The cricoid cartilage is a ring-shaped structure which reinforces the lower larynx where it meets the trachea. It serves as the anchor point for the arytenoid cartilages (which pivot upon the back part of the cricoid cartilage). The arytenoid cartilages are also connected to the cricoid cartilage by cricoarytenoid muscles. The vocal cords are attached to the arytenoid cartilages, from which they span across the larynx to the inside part of the thyroidcartilage on the other side of the airway. By flexing or relaxing the cricoarytenoid muscles, the arytenoid cartilages are forced to pivot, causing the vocal cords to be brought together for speech or separated, for breathing. The vocal and cricothyroid muscles then regulate the degree of tension in the vocal cords, changing the tone of voice during speech. Research Cricoid Cartilage
Croup, or acute laryngotracheo-bronchitis, is an inflammation of upper and lower respiratory system, including the larynx, due to a viral infection. The inflammation causes a narrowing of the air passages. The most common causative agents are the parainfluenza viruses, especially type 1, the respiratory syncytial viruses (RSV), and influenza A and B viruses.
Croup occurs mainly in children between the ages of three months and three years. In older children and adults, the air passages are too wide and the cartilage in the wall too stiff for swelling or inflammation to cause the walls to collapse. The condition is characterised by fever, cough and breathing difficulty which is accompanied by a harsh croaking noise. Research Croup
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Howler Monkey
