Muscular tissue is a collection of muscle cells and fibers that are extremely distinctive in their ability to shorten or contract in order to conveniently move physiological parts. The tissue is densely packed with cells and well-served by blood arteries. Muscle fibers refer to the long, slender cells that make up muscle tissue. These are often grouped in bundles or layers and are encased in connective tissue. Contractile proteins in muscle tissue such as actin and myosin.
The word muscle derived form Latin word musculus ” little mouse”, referring to muscles like the biceps, which pop up as though a mouse were scurrying about under the skin. Muscles includes very specialized thin and elongated cell called muscle fibres. There are about types of muscles in the human body which forms about 40% of body weight. Its function is to produce force and cause motion, either locomotion or movement within internal organs.
Much of muscle contraction occurs without conscious through and is necessary for survival, like the contraction occurs without conscious through and is necessary for survival, like the contraction of the heart or peristalsis, which pushes food through the digestive system. Voluntary muscle contraction is used to move the body and can be finely controlled, such as movements of the finger or gross movements like the quadriceps muscle of the thigh.
It is contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells except the iridial and ciliary muscles of the eye which is ectodermal in origin.
General Properties Of Muscular Tissue
it is the special property of muscular tissue in wihch the cells of muscular tissue called myocytes can shorten considerably and return to the original relaxed state. this special feature of muscles is called contractility. it is due to the contractile protoplasm of muscle cells and presence of myofibrils.
Excitability is another special property of muscle; it is due to the energy stored in the electrical potential difference across the plasma membrane.
Structures of Muscular Tissue
The muscles include long, narrow, and thin cells called muscle fibres. The specialized cytoplasm of the muscle cells is called sarcoplasm which includes a network of membranous sarcoplasmic reticulum. Sarcoplasm is largely occupied by finer, parallel protein threads, called myofibrils, which are arranged in the long axis of the fibre. The myofibrils are composed of actin and myosin. it also contains abundant mitochondria and glycogen granules. It may contain one or more nuclei. The plasma membrane of muscle fibre is called sarcolemma. Individual muscle cells are lined it endomysium. Muscle cells are bound together by perimysium into bundles called fascicles; the bundles are then grouped together to form muscle, which is lined by epimysium. Muscle spindles are distributed throughout the muscles and provide sensory feedback information to the central nervous system.
Muscular activity account of most of the body’s energy conduction. Muscle store energy for their own use in the form of glycogen, which represents about 1% of their mass. This can be rapidly converted to glucose when energy is required for sustained, powerful contractions. Within voluntary skeletal muscles, the glucose muscle is split into two-three carbon molecules is known as Lactic acid-producing two Adenosine Triphosphate (ATP) molecules in the process, which are then used to power the movement of the myosin heads. Muscle cell also contains globules of fat, which are used for energy during aerobic exercise. The aerobic energy systems take longer to produce the ATP and reach peak efficiency, and requires many more biochemical steps, but produces significantly more ATP than a glucose molecule.
Cardiac muscle on the other hand, can readily consume any of the three macronutrients. (Protein, Glucose and Fat) without a ‘ warm up’ period and always extracts the maximum ATP yield from and molecule involved. The heart will also consume lactic acid produced and excreted by skeletal muscles during exercise.
Functions of Muscular Tissue
- It helps in movement of body pars and movement of an individual.
- It supports the bones and other structures of body.
- It also helps in contraction and expansion of heart, alimentary canal (peristalsis), blood vessels, lymphatic vessels, lungs, etc.
- It is responsible for the flow of air the respiratory tract, for the sound production and for the propulsion of secretions and waste materials through the excretory ducts.
- It helps in mating, in taking of food delivering a baby and movement of sense organs for collection of different types of senses.
- The facial expression and gesture is also depends on muscles.
Readers Also Read: Simple Epithelial Tissue
Types of Muscular Tissue
There are three types of muscles on the basis of structure; location and function. They are stripped smooth and cardiac muscle. The Three Types of muscle have significant differences. However, all three users the moment of action against myosin to create contraction. In skeletal muscle, contraction is stimulated by electrical impulses transmitted by the nerves, the motor nerves, and motor neurons in particular. Cardiac and smooth muscle contraction is stimulated by internal pacemaker cells that regularly contract and propagate connections to other muscle cells they are in contact with. All skeletal muscle and smooth muscle contraction are facilitated by the neurotransmitter acetylcholine.
1. The Skeletal or Stripped Muscle
When it comes to vertebrates, the most frequent type of muscle is skeletal muscle. Skeletal muscles are attached to bones via tendons, and they are responsible for all of the motions that occur within the body. Skeletal muscle, in contrast to smooth and cardiac muscle, is a voluntary muscle. Strictly speaking, skeletal muscle differs from cardiac muscle in that it has long, thin, multinucleated fibers that cross in a regular pattern of fine red and white lines, whereas cardiac muscle does not. Connective tissue is the tissue that connects skeletal muscle fibers to neurons and blood vessels.
Properties of Stripped Muscle
- Commonly called as voluntary or bony or striated or stripped muscles.
- Long, cylindrical and non-tapering. Length about 2.5cm and width 0.05 mm.
- Sarcolemma is present.
- Presence of transverse alternate length and dark bands.
- Each fibre multinucleate shows coenocytic character.
- Have both motor and sensory nerves.
- Have rich blood supplies.
- Show fatigue character.
- Usually attached to bones.
2. Unstriated or Smooth or Involuntary Muscles
Involuntary movements include the flow of food through the digestive tract and the contraction and relaxation of blood vessels. This type of muscle is also called smooth muscle. Muscles in the iris of the eye, the ureters, and the bronchi of the lungs are just a few examples. Contraction elements are elongated spindle-shaped cells with centrally located nuclei and a length of 20-200 mcc, or even longer in the pregnant uterus; transverse striations are absent, but both thick and thin myofibrils occur; smooth muscle fibers are bound together into sheets or bundles by reticular fibers, and frequencies of reticular fibers are common.
Read in detail: Involuntary Muscles
Properties Of Unstriated Muscle
- Commonly called involuntary or visceral muscles or unstraited or unstripped.
- Elongated, both ends pointed or branched, looks spears like, Length about 1/20th mm and width about 1/160th mm.
- No true sarcolemma
- No bands
- Uninucleate, nucleus hardly seen.
- Nerves from sympathetic and para sympathetic nervous system.
- Have poor blood supplies.
- No fatigue.
- Found in viscera.
- Help during peristalsis, secretion, absorption, etc. activities.
3. Cardiac Muscle
Cardiac Muscle (myocardium) is one of three types of muscle found only in the heart of vertebrates. Cardiac muscle, like skeletal muscle, has sarcomeres, which separate it from smooth muscle, the third primary muscle type. Cardiac muscle has rhythmic contractions and is not controlled by the brain. The sinoatrial node, or pacemaker, regulates the rhythmic contraction of cardiac muscle. Heart muscle cells make up the majority (or myocardium). The heart’s function is characterized by contractility, which is the basis for pumping, and rhythmicity.
Properties Of Cardiac Muscle
- Commonly called cardia muscles
- No separate fibres due to bridges in between tissues or fibres
- Sarcolemma is present
- Cross striations are seen
- Multinucleate between each plate
- Nerves from cranial and autonomic
- Have rich blood supplies
- Immune to fatigue
- Only found in heart
- Help to conduct movement of the heart
Hence, the Muscularly system consists of the whole muscles of our body. On the basis of usage, location and structure there are three types of muscles invertebrate animals. Hope this article helped you to understand muscular tissue, types, and its structure. If you have any confusion related to this topic then feel free to comment.
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