White meat or dark?\u00a0 This question will be asked thousands of times as families and friends gather around the Thanksgiving turkey.<\/p>\n
But why are there two kinds of muscles?\u00a0 We\u2019ll need to explore some muscle physiology to answer the question.\u00a0 Muscles are made of many elongate cells called muscle fibers.\u00a0 Each fiber is capable of contracting, causing the muscle to shorten.\u00a0 The muscles are attached to bones via a piece of connective tissue called tendons.\u00a0 When all the fibers of a muscle contract, the muscle is capable of remarkable force, causing movement in the part of the body to which the muscle inserts.<\/p>\n
All muscles contain a mixture of two types of fibers: white and dark (or red).\u00a0 They differ in their metabolism and their contractile properties.\u00a0 Dark fibers are sometimes referred to as slow-twitch muscles or aerobic muscles.\u00a0 As the name implies, aerobic fibers require a constant supply of oxygen to continue to function.\u00a0 This oxygen supply is enabled by the myoglobin molecules in the muscle fibers.<\/p>\n
Like the related hemoglobin in the blood, myoglobin is a molecule that readily binds to oxygen.\u00a0 Oxygenated blood courses through muscles and oxygen is transferred from the hemoglobin in the red blood cells to the myoglobin molecules in the muscle fibers.\u00a0 The more myoglobin within the muscle fibers of a muscle, the darker the muscle appears.<\/p>\n
Dark fibers are great for activities involving endurance.\u00a0 Walking and running are generally powered by the contraction of aerobic fibers.<\/p>\n
White fibers, also called fast-twitch fibers or anaerobic fibers, are used for rapid, short-term activities like fleeing from danger.\u00a0 These fast-twitch muscles are able to contract more quickly than the dark, slow-twitch muscles.\u00a0 However, they fatigue very quickly.\u00a0 These fibers operate in an anaerobic mode, a mode not requiring the continuous input of oxygen.\u00a0 To fuel their contraction, white fibers take up the starch glygogen, stored in the muscle fibers.\u00a0 The glycogen stores are quickly depleted so the rapid contraction of the white fibers is necessarily limited in duration.<\/p>\n
In life, muscles made mostly of white fibers appear translucent and glossy.\u00a0 When cooked, the proteins in the muscle fibers denature and coagulate, resulting in the white, opaque appearance we associate with a chicken or turkey breast.<\/p>\n
The myoglobin in the dark muscles also breaks down during cooking, imparting the brownish color to the meat.\u00a0 The breakdown of myoglobin also makes a steak brown when it is cooked.<\/p>\n
Birds that migrate long distances have breast muscles made mostly of dark muscle fibers to enable long bouts of strenuous flight.\u00a0 Ducks and geese have breast muscles made of aerobic fibers and are dark when cooked.\u00a0 Wild Turkeys do not fly for great distances.\u00a0 These birds have breast muscles that contain fewer dark fibers than a duck but more dark fibers than a domesticated turkey.<\/p>\n
Domesticated turkeys have far larger breast muscles than Wild Turkeys. Selective breeding by turkey farmers has led to the increase in these muscles. \u00a0The breast muscles of a male turkey are so massive that the tom turkeys are incapable of getting close enough to a hen turkey to mate.\u00a0 Domesticated turkeys are produced by artificial insemination.<\/p>\n
In a cooked turkey or chicken, you can see two distinct muscles in the breast: the smaller supracoracoideus (closer to the base of the breastbone) and the much larger pectoralis muscle.\u00a0 Both attach to the upper wing bone, the humerus.\u00a0 The pectoralis pulls the wing down, providing the power for flight.\u00a0\u00a0 The supracoracoideus muscle pulls the wing back up in preparation for the next power stroke.<\/p>\n
How does a muscle below the wing raise the wing?\u00a0 The supracoracoideus runs through a canal between the humerus, the scapula and the coracoid bone to attach on the upper side of the humerus.\u00a0 With a downward tug, the wing is raised.<\/p>\n
[First published on November 26, 2013]<\/p>\n\n
White meat or dark?\u00a0 This question will be asked thousands of times as families and friends gather around the Thanksgiving turkey. But why are there two kinds of muscles?\u00a0 We\u2019ll need to explore some muscle physiology to answer the question.\u00a0 Muscles are made of many elongate cells called muscle fibers.\u00a0 Each fiber is capable of […]<\/p>\n","protected":false},"author":146,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_s2mail":"yes","ngg_post_thumbnail":0,"footnotes":""},"categories":[430],"tags":[],"builder_content":"","_links":{"self":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/629"}],"collection":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/users\/146"}],"replies":[{"embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/comments?post=629"}],"version-history":[{"count":1,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/629\/revisions"}],"predecessor-version":[{"id":630,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/629\/revisions\/630"}],"wp:attachment":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/media?parent=629"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/categories?post=629"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/tags?post=629"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}