What Type Of Tissue Is Skeletal Muscle – Muscle tissue is characterized by properties that allow movement. Muscle cells are excitable; they respond to stimuli. They are contractile, that is, capable of shortening and generating traction. When two movable objects, in other words, are attached between bones, the contraction of muscles causes the bones to move. Some muscle movement is voluntary, meaning it is under conscious control. For example, a person opens a book and decides to read a chapter on anatomy. Other movements are involuntary, meaning they are not under conscious control, such as pupil contraction in bright light. Muscle tissue is classified into three types based on their structure and function: skeletal, cardiac, and smooth (Table 1).
Involuntary movement, moves food, involuntarily controls breathing, moves secretion, regulates blood flow in arteries by contraction.
What Type Of Tissue Is Skeletal Muscle
Skeletal muscle is attached to bones and its contractions make locomotion, facial expressions, posture, and other voluntary body movements possible. Forty percent of your body weight is skeletal muscle. Skeletal muscles produce heat as a byproduct of their contractions and thus participate in thermal homeostasis. Shivering is an involuntary contraction of skeletal muscles in response to the sensation of body temperature below normal. A muscle cell or myocyte develops from myoblasts derived from the mesoderm. Myocytes and their number remain relatively constant throughout life. Skeletal muscle tissue is arranged in bundles surrounded by connective tissue. Under a light microscope, muscle cells appear striated with many nuclei compressed along the membranes. The striatum depends on the constant alternation of the contractile proteins actin and myosin, as well as the structural proteins that connect the contractile proteins to connective tissue. Cells become multinucleated as a result of the fusion of many myoblasts that form each long muscle fiber.
Skeletal Muscle And Its Contraction
Cardiac muscle forms the contractile walls of the heart. Heart muscle cells, called cardiomyocytes, also appear striated under the microscope. Unlike skeletal muscle fibers, cardiomyocytes are typically single cells with a centrally located nucleus. The main characteristic of cardiomyocytes is that they contract according to their own internal rhythm without any external stimulation. Cardiomyocytes are attached to each other by special cell junctions called intercalated discs. Intercalated discs have both anchoring joints and holes. Attached cells form long, branching cardiac muscle fibers, which are essentially mechanical and electrochemical syncytiums that allow the cells to synchronize their actions. The heart muscle pumps blood through the body and is under voluntary control. Adhesion junctions hold adjacent cells together through the dynamic pressure changes of the cardiac cycle.
Contraction of smooth muscle tissue is responsible for involuntary movements in internal organs. It forms the contractile component of the digestive, urinary and reproductive systems, as well as the respiratory tract and arteries. Each cell is spindle-shaped with a single nucleus and no visible bands (Figure 1).
Figure 1. Muscle tissue. (a) Skeletal muscle cells have prominent bands and nuclei at their periphery. b) Smooth muscle cells have a single nucleus and no visible striations. (c) Cardiac muscle cells appear striated and contain a single nucleus. From top, LM × 1600, LM × 1600, LM × 1600. (Micrographs courtesy of the Regents of the University of Michigan Medical School © 2012)
Watch this video to learn more about muscle tissue. How can you distinguish skeletal muscle tissue from smooth muscle under a microscope? Muscle is one of the body’s four major tissue types (along with epithelium, nervous, and connective tissue), and there are three types of muscle tissue in the body: skeletal muscle, cardiac muscle, and smooth muscle (Figure 10.1.1). All three muscle tissues have common properties; they all exhibit a quality called excitability because their plasma membranes can change their electrical state (from polarized to depolarized) and send an electrical wave called an action potential along the entire length of the membrane. Although the nervous system can influence cardiac and smooth muscle excitability to some extent, skeletal muscles are completely dependent on nervous system signaling for proper functioning. On the other hand, both cardiac muscle and smooth muscle can respond to other stimuli such as hormones and local stimuli.
Section 2: The Muscular System
Figure 10.1.1 – Three types of muscle tissue: There are three types of muscle tissue in the body: (a) skeletal muscle, (b) smooth muscle and (c) cardiac muscle. From top, LM × 1600, LM × 1600, LM × 1600. (Micrographs courtesy of the Regents of the University of Michigan Medical School © 2012)
A unique property shared by all three types of muscle is the ability to contract, shorten cells, and generate force. Muscle tissue can shorten during contraction, and it also exhibits the ability to stretch and stretch beyond the cell’s resting length. After stretching, the elasticity of the muscle allows it to return to its original length.
All muscles begin the process of mechanical contraction (shortening) when a protein called actin is pulled by a protein called myosin, and there are differences in the microscopic organization of these contractile proteins between the three types of muscles. In skeletal and cardiac muscle, the actin and myosin proteins are arranged in a very regular pattern in the cytoplasm of individual muscle cells, creating an alternating light and dark band pattern known as striations. Bands are visible under a light microscope at high magnification (see Figure 10.1.1). Smooth muscle (so named because of the lack of striations) does not form this striated pattern because the contractile proteins are not arranged in a regular manner.
Skeletal muscle cells (also called muscle fibers) are unique in that they are multinucleated with their nuclei located at the periphery of the cell beneath the cell’s plasma membrane (also called the sarcolemma in muscle). During early development, embryonic myoblasts, each with its own nucleus, fuse with hundreds of other myoblasts to form long multinucleated skeletal muscle fibers. Each heart muscle cell usually has a single nucleus located in the center of the cell, but the cells are physically and electrically connected to each other so that contraction signals are transmitted through the cells and the whole heart contracts as a unit. Smooth muscle cells consist of a single nucleus and can contract as a single unit in electrically coupled units or multiunit smooth muscle in which the cells are not electrically coupled.
Structure And Functions Of Muscle Tissue
The best known property of skeletal muscle is its ability to contract and cause movement. Skeletal muscles act not only to produce movement but also to stop movement, such as resisting gravity to maintain posture. Keeping the body upright or balanced in any position requires small, constant adjustments of the skeletal muscles. Muscles also prevent excessive movement of bones and joints, maintain skeletal stability, and prevent damage or deformation of the skeletal structure.
Skeletal muscles are located in pathways throughout the body to control the movement of various objects. These muscles allow for voluntary control of functions such as swallowing, urination, and defecation. Skeletal muscles also protect the internal organs (especially the abdominal and pelvic organs) by acting as an external barrier or shield against external injury and by supporting the weight of the organs.
Skeletal muscles contribute to maintaining homeostasis in the body by producing heat. Muscle contraction requires energy, and heat is generated when ATP is broken down. This heat is most evident during exercise, when constant muscle movement causes an increase in body temperature, and when extreme cold causes involuntary contractions of skeletal muscles to generate heat during shivering.
Cardiac muscle is found only in the heart and functions to create force and pressure gradients to drive blood flow throughout the body. Smooth muscle in the walls of arteries is an important component that regulates blood pressure and blood flow through the circulatory system. Smooth muscle in the skin, internal organs, and internal passageways is also essential for moving materials through the body. Neither cardiac muscle nor smooth muscle are attached to bone, so they cannot perform the heavy movements we associate with skeletal muscle.
Overview Of Muscle Tissues
Muscle is the tissue in animals that allows active movement of the body or substances within the body. There are three types of muscle tissue: skeletal muscle, cardiac muscle, and smooth muscle. Most of the body’s skeletal muscles produce movement by acting on the skeleton. The heart muscle is located in the wall of the heart and pumps blood through the circulatory system. Smooth muscle is found in the skin, where it is associated with hair follicles; it is also found in the walls of internal organs, blood vessels, and internal passageways, where it helps move materials.
Striated muscle in the heart; in intercalated discs and combined with regulation of pacemaker cells that contract as a single unit to pump blood through the circulatory system. The heart muscle is under involuntary control.
Striated, multinucleated muscle that requires a signal from the nervous system to initiate contraction; Most of the skeletal muscles are called voluntary muscles, which move bones and cause movement
A cutaneous, mononucleated muscle associated with hair follicles; helps move materials along the walls of internal organs, blood vessels, and internal passages
Muscle Tissue Type Activity Worksheet Cardiac, Skeletal And Smooth
This Anatomy and Physiology work is adapted from the book Anatomy and Physiology by Stax, licensed under CC BY. This publication,
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