Muscle location

Alpha-1 Receptors. A primary location of these receptors is the smooth muscle located in various tissues throughout the body. Alpha-1 receptors are located on the smooth muscle located in the peripheral vasculature, intestinal wall, radial muscle of the iris, ureters, urinary sphincter, and spleen capsule. The response of each tissue when the alpha-1 receptor is stimulated varies depending on the tissue (see Table 18-2). Research also suggests that there might be three subtypes of alpha-1 receptors, identified as alpha-1 A, alpha-IB, and alpha-ID receptors.4 Much of this research, however, has focused on the characteristics of alpha-1 receptor subtypes in various animal models. Studies are currently underway to determine the exact location and functional significance of these alpha-1 receptor subtypes in humans. 

Alpha-1 blockers can also be used to treat the symptoms of benign prostatic hypertrophy because they decrease sympathetic-mediated contraction of smooth muscle located in the prostate gland.34,91 Reduction of muscle tone in the prostate decreases constriction of the ureter, thereby improving urinary flow and the ability to empty the bladder.58,83... 

The ventricular papillary muscles attached to cups of the auriculo-ventricular valves contract before ventricular systole and maintain tension to prevent backflow of blood in the auricles. It has been well documented that ventricular arrhythmias can originate from the papillary muscles located in the right [59] or the left [60-63] ventricle. The ex vivo preparations of papillary muscles from different laboratory animals are used for investigation of inotropic and lusitropic effect or effect on AP duration induced by different drugs [64-68]. 

Effector organs are mainly the respiratory muscles, as described previously. Other effectors are muscles located in the airways and tissues for mucus secretion. Control of respiration appears to be based on two criteria (1) removal of excess CO2 and (2) minimization of energy expenditure. It is not the lack of oxygen that stimulates respiration but increased CO2 partial pressure that acts as a powerful respiratory stimulus. Because of the buffering action of blood bicarbonate, blood pH usually falls as more CO2 is produced in the working muscles. Lower blood pH also stimulates respiration. 

Medial pterygoid A thick quadrilateral muscle located deep to the ramus of the mandible it embraces the inferior head of the lateral pterygoid muscle. 

The intrinsic muscles of the hand lie on the palm and can be divided into three main groups the thenar muscles for the thumb the hypothenar muscles for the little finger the lumbrical muscles and the interosseous muscles located in the central palm and in between the metacarpals respectively (Fig. 11.6). 

The thenar muscles are innervated by the recurrent branch of the median nerve and are basically responsible for the complex movement of the thumb. They include the superficial abductor pollicis brevis, the flexor pollicis brevis and the deep opponens pollicis muscles. The abductor pollicis brevis is a broad flat muscle located on the more lateral side of the thenar eminence. It arises from the radial side of the transverse carpal ligament and the tubercle of the trapezium and inserts into the base of the proximal phalanx. The flexor pollicis brevis is located medial to the abductor pollicis and has two muscular bellies the superficial head arises from the transverse carpal ligament and the tubercle of the trapezium, the deep head (first palmar interosseous muscle) from the trapezoid and the capitate. Both heads insert through the radial sesamoid over the metacar-... 

US can accurately image the muscles located superficially to the hip joint. They are best depicted... 

This muscle is the central muscle of the three muscles located in the most superficial muscular layer of the foot. 

Paraspinal muscles are a generic anatomical term used to identify all those muscles located at each side of the spinous process of the spinal column. They are divided in 3 regions the Cervical, the Thoracic, and... 

Muscles located at the anterior surface of the cervical spine are ... 

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