what physiological properties give muscles their ability to create motion
Musculoskeletal organisation
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The musculoskeletal system (locomotor arrangement) is a human trunk system that provides our body with motility, stability, shape, and support. It is subdivided into two broad systems:
- Muscular arrangement, which includes all types of muscles in the torso. Skeletal muscles, in item, are the ones that act on the body joints to produce movements. As well muscles, the muscular arrangement contains the tendons which attach the muscles to the bones.
- Skeletal system, whose chief component is the bone. Bones articulate with each other and form the joints, providing our bodies with a hard-core, yet mobile, skeleton. The integrity and role of the bones and joints is supported past the accessory structures of the skeletal system; articular cartilage, ligaments, and bursae.
Besides its main function to provide the body with stability and mobility, the musculoskeletal arrangement has many other functions; the skeletal part plays an of import part in other homeostatic functions such as storage of minerals (due east.g., calcium) and hematopoiesis, while the muscular organization stores the majority of the body'due south carbohydrates in the class of glycogen.
This commodity will innovate you lot to the anatomy and function of the musculoskeletal arrangement.
| Definition | A human body system that provides the torso with motility, stability, shape, and support |
| Components | Muscular system: skeletal muscles and tendons Skeletal organization: bones, joints; associated tissues (cartilage, ligaments, articulation capsule, bursae) |
| Function | Muscles: Movement production, joint stabilization, maintaining posture, body heat production Bones: Mechanical basis for movements, providing framework for the trunk, vital organs protection, blood cells production, storage of minerals |
Contents
- Muscular system
- Skeletal muscles
- Construction
- Muscle contraction
- Tendons
- Functions of the muscular system
- Skeletal system
- Bones
- Cartilage
- Joints
- Ligaments
- Bursae
- Functions of the skeletal organisation
- Clinical correlation
- Osteoporosis
- Sarcopenia
- Arthritis
- Muscular dystrophy
- Sources
+ Show all
Muscular system
The muscular system is an organ system composed of specialized contractile tissue called the muscle tissue. There are iii types of muscle tissue, based on which all the muscles are classified into three groups:
- Cardiac muscle, which forms the muscular layer of the middle (myocardium)
- Smooth musculus, which comprises the walls of blood vessels and hollow organs
- Skeletal muscle, which attaches to the bones and provides voluntary motility.
Based on their histological appearance, these types are classified into striated and non-striated muscles; with the skeletal and cardiac muscles being grouped as striated, while the smooth muscle is not-striated. The skeletal muscles are the only ones that we can command by the ability of our will, as they are innervated by the somatic role of the nervous organization. In contrast to this, the cardiac and smooth muscles are innervated by the autonomic nervous system, thus being controlled involuntarily by the autonomic centers in our brain.
Skeletal muscles
The skeletal muscles are the main functional units of the muscular system. There are more than 600 muscles in the human torso. They vary greatly in shape in size, with the smallest one existence the stapedius muscle in the inner ear, and the largest one beingness the quadriceps femoris musculus in the thigh.
The skeletal muscles of the human torso are organized into four groups for every region of the body:
- Muscles of the head and cervix, which include the muscles of the facial expression, muscles of mastication, muscles of the orbit, muscles of the tongue, muscles of the pharynx, muscles of the larynx, and muscles of the neck
- Muscles of the trunk, which include the muscles of the back, anterior and lateral abdominal muscles, and muscles of the pelvic floor
- Muscles of the upper limbs, which include muscles of the shoulder, muscles of the arm, muscles of the forearm and muscles of the hand
- Muscles of the lower limbs, which include hip and thigh muscles, leg muscles and human foot muscles
The fact that at that place are more than than 600 muscles in the body tin exist quite intimidating. If you're tired of all the large, comprehensive anatomy books, take a look at our condensed muscle anatomy reference charts, which comprise all the muscle facts in one place organized into not bad tables!
Structure
Structurally, the skeletal muscles are composed of the skeletal muscle cells which are called the myocytes (muscle fibres, or myofibrils). Muscle fibers are specialized cells whose main feature is the ability to contract. They are elongated, cylindrical, multinucleated cells bounded by a cell membrane called sarcolemma. The cytoplasm of skeletal muscle fibers (sarcoplasm), contains contractile proteins chosen actin and myosin. These proteins are arranged into patterns, forming the units of contractile micro-apparatus called sarcomeres.
Each muscle cobweb is enclosed with a loose connective tissue sheath chosen endomysium. Multiple muscle fibers are grouped into muscle fascicles or muscle bundles, which are encompassed by their own connective tissue sheath chosen the perimysium. Ultimately, a group of muscle fascicles comprises a whole muscle belly which is externally enclosed by another connective tissue layer called the epimysium. This layer is continuous with even so another layer of connective tissue called the deep fascia of skeletal musculus, that separates the muscles from other tissues and organs.
This structure gives the skeletal musculus tissue four master physiological backdrop:
- Excitability - the ability to detect the neural stimuli (action potential);
- Contractibility - the ability to contract in response to a neural stimulus;
- Extensibility - the ability of a muscle to be stretched without tearing;
- Elasticity - the power to render to its normal shape after beingness extended.
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Muscle contraction
The nigh of import property of skeletal muscles is its ability to contract. Musculus contraction occurs as a issue of the interaction of myofibrils inside the muscle cells. This process either shortens the musculus or increases its tension, generating a force that either facilitates or slows down a motility.
There are two types of muscle contraction; isometric and isotonic. A muscle wrinkle is deemed equally isometric if the length of the muscle does not change during the contraction, and isotonic if the tension remains unchanged while the length of the muscle changes. In that location are two types of isotonic contractions:
- Concentric contraction, in which the musculus shortens due to generating enough force to overcome the imposed resistance. This blazon of contraction serves to facilitate any noticeable movement (eastward.g. lifting a barbell or walking on an incline).
- Eccentric contraction, in which the muscle stretches due to the resistance beingness greater than the forcefulness the muscle generates. During an eccentric wrinkle, the muscle maintains high tension. This type of contraction usually serves to tiresome down a movement (e.thousand. lowering a barbell or walking downhill).
The sequence of events that results in the wrinkle of a musculus prison cell begins as the nervous organisation generates a indicate called the action potential. This bespeak travels through motor neurons to reach the neuromuscular junction, the site of contact between the motor nerve and the musculus. A group of musculus cells innervated by the branches of a unmarried motor nervus is called the motor unit.
The incoming action potential from the motor nerve initiates the release of acetylcholine (ACh) from the nerve into the synaptic cleft, which is the space between the nervus ending and the sarcolemma. The ACh binds to the receptors on the sarcolemma and triggers a chemic reaction in the muscle jail cell. This involves the release of calcium ions from the sarcoplasmic reticulum, which in turn causes a rearrangement of contractile proteins within the muscle cell. The chief proteins involved are actin and myosin, which in the presence of ATP, slide over each other and pull on the ends of each muscle cell together, causing a contraction. As the nervus point diminishes, the chemical process reverses and the muscle relaxes.
Tendons
A tendon is a tough, flexible band of dense connective tissue that serves to attach skeletal muscles to bones. Tendons are found at the distal and proximal ends of muscles, binding them to the periosteum of bones at their proximal (origin) and distal attachment (insertion) on the os. Equally muscles contract, the tendons transmit the mechanical force to the bones, pulling them and causing motion.
Existence made of dense regular connective tissue, the tendons take an abundance of parallel collagen fibers, which provide them with high tensile strength (resistance to longitudinal strength). The collagen fibers within a tendon are organized into fascicles, and private fascicles are ensheathed by a sparse layer of dumbo connective tissue called endotenon. In plow, groups of fascicles are ensheathed by a layer of dense irregular connective tissue chosen epitenon. Finally, the epitenon is encircled with a synovial sheath and fastened to it past a delicate connective tissue band called mesotenon.
Functions of the muscular organisation
The master function of the muscular organization is to produce movement of the body. Depending on the centrality and airplane, at that place are several dissimilar types of movements that can exist performed past the musculoskeletal system. Some of the about important ones include:
- Flexion and extension: move of decreasing or increasing the angle betwixt the bones involved in the movement, respectively. This motion takes place in the sagittal plane around a frontal axis. An example of flexion is bending the leg at the knee joint, whereas extension would be straightening knee from a flexed position.
- Adduction and abduction: movements of bringing the parts of the trunk towards or abroad from the midline, respectively. These movements are carried out in the frontal plane around a sagittal centrality. For example, abduction of the arm at the shoulder joint involves moving the arm away from the side of the torso, while adduction involves bringing it back towards the body.
- Rotation is the movement in which a part of the body rotates effectually its vertical (longitudinal) axis in the transverse plane. This movement is defined relative to the midline, where internal rotation involves rotating the segment towards to the midline, while external rotation involves moving it abroad from the midline. Examples include lateral or medial rotation of the thigh.
- Supination and pronation are special types of rotatory movements usually used to describe the movements of the forearm. Supination is essentially a lateral rotation of the forearm which turns the palms anteriorly (if the arm is anatomical position) or superiorly, when the elbow is flexed. These movements are besides sometimes used to depict movements in the ankle and pes, in which supination means rolling the foot outwards, while pronation means rolling the foot inwards.
Both during motion and stationary positions, muscles contribute to the overall back up and stability of joints. Many muscles and their tendons pass over joints and thereby stabilize the articulating bones and hold them in position. In improver, the muscles as well play an important role in maintaining posture. While the movements occur mainly due to muscles intermittently contracting and relaxing, the posture is maintained by a sustained tonic contraction of postural muscles. These muscles act against gravity and stabilize the body during standing or walking. The postural muscles include the muscles of the dorsum and intestinal muscles.
Some other important function of muscles is heat product. Muscle tissue is one of the most metabolically active tissues in the body, in which approximately 85 percent of the estrus produced in the body is the result of muscle contraction. This makes the muscles essential for maintaining normal trunk temperature.
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Skeletal system
The adult human skeleton is composed of 206 bones and their associated cartilages. The basic are supported by ligaments, tendons, bursae, and muscles. The bones of the body are grouped within the two distinct divisions:
- Centric skeleton, that includes the bones forth the long axis of the body. The axial skeleton consists of the vertebral column, bones of the head and bones of the thoracic cage.
- Appendicular skeleton, that involves the bones of the shoulder and pelvic girdle, besides as the bones of the upper and lower extremities.
Bones
Bones are rigid structures made of calcified dumbo connective tissue. Bone tissue is equanimous of a mineralized os matrix that consists of type 1 collagen fibers dispersed throughout the ground substance. The cellular component of the bones is represented past three types of specialized bone cells chosen osteocytes, osteoblasts and osteoclasts.
The basic consist of two distinct layers that differ in histological advent and characteristics;
- Compact (cortical) bone is the outer much denser layer of the bone which gives it its shine, white, and solid appearance. The outer surface of the meaty bone is covered with a layer of dumbo connective tissue chosen the periosteum. On its inner surface, the compact bone is covered with endosteum, which is the boundary between the meaty and spongy basic.
- Spongy (cancellous) bone is the deep airy layer of the bone. Unlike the compact bone, spongy bone is highly vascularized and more metabolically agile. It is typically found within the ends of long bones and in the vertebrae. In sure basic, similar the hip bone, sternum or femur, the primal function of spongy bone houses the bone marrow, which is the site of hematopoiesis in the adult.
Types of bones
Basic can exist classified according to their shapes as follows:
- Long bones take a tubular shape, with a longer longitudinal and a shorter transverse bore. They are composed mostly of compact os, while the spongy bone and bony marrow make full the ends of the bones. Examples of long basic include the humerus, ulna, tibia and clavicle.
- Curt bones accept a roughly cuboid or circular shape, and but contain a sparse layer of compact bone surrounding the spongy bone. Examples include the tarsal and carpal bones.
- Flat bones are mostly thin, flattened and usually curved. They contain two parallel layers of compact bones surrounding a layer of spongy bone. Examples include most of the skull basic, scapula, sternum and sacrum.
- Sesamoid bones are pocket-sized, rounded unique types of bones that are embedded in musculus tendons where the tendon passes over a joint. The largest sesamoid bone in the trunk is the patella, but several other smaller sesamoid bones can be constitute in the hand and foot, usually in close proximity to the joints.
- Irregular bones do non fit into any of the other categories. Generally, irregular basic contain foramina through which soft tissue and neurovascular structures laissez passer. Examples include the vertebrae, hip os and some basic of the skull.
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A typical long bone consists of a long shaft (diaphysis) that extends into a cervix (metaphysis) and head (epiphysis) on its proximal and distal ends. It also features diverse markings and formations that give passage to neurovascular structures, also as the attachment sites to the ligaments and tendons. Some of those features include:
- Sulcus – a shallow groove on the bone surface (e.g. radial sulcus of humerus)
- Condyle – rounded articular area (due east.thou. lateral condyle of tibia)
- Epicondyle – eminence superior to a condyle (medial epicondyle of femur)
- Crest – ridge of bone (e.grand. iliac crest)
- Facet – smooth, flat surface area, usually covered with cartilage (e.one thousand. articular facet on vertebrae)
- Foramen – passage through a os (e.thou. foramen magnum on the occipital os)
Cartilage
Cartilage is a flexible connective tissue found in multiple organ systems of the body. Cartilage is composed of specialized cells called chondrocytes, collagen fibers and abundant ground substance rich in proteoglycan and elastin fibers.
Cartilage is classified into the following types based on its composition:
- Hyaline cartilage is composed of type II collagen and an abundance of ground substance, which gives it a sleeky appearance. It is the most abundant type of cartilage found in joints (articular cartilage), too as the nose, larynx, trachea and ribs.
- Rubberband cartilage is like to hyaline cartilage but contains more than elastic fibers. It is found in structures such as the pinna of the ear, auditory tube and epiglottis.
- Fibrocartilage is composed of plenty of collagen fibers type I and a smaller amount of footing substance. Examples of fibrocartilage include intervertebral discs, pubic and other symphyses.
The musculoskeletal arrangement specifically contains articular cartilage, a type of cartilage that lines the articulating surfaces of basic. The articular cartilage provides congruence to the articulating basic and allows them to bear weight and glide over each other with very little friction.
Joints
Each os of the musculoskeletal organization is connected to one or more bones via a joint. Joints provide a fulcrum to the bones, on which they pivot and thereby allow movements of body parts. Even so, motility is not a necessary aspect of a articulation every bit some joints do not motility, such as joints between the bones of the skull. The integrity or stability of a joint is provided past several factors including the bony congruence and structures that cross the articulation, such as tendons and ligaments.
Based on the type of tissue that holds the neighboring bones together and the range of motion they exhibit, joints can exist classified into the following:
- Synovial joints are freely mobile joints in which the bones are non in directly contact, but are separated by a potential infinite chosen the synovial cavity. The synovial cavity is lined past a synovial membrane that secretes the synovial fluid which nourishes and lubricates the articulating surfaces in gild to reduce friction. The articulating basic in most synovial joints are lined with hyaline cartilage. These joints normally have a wide range of motion, which is defined by the joint capsule, the supporting ligaments and muscles that cross the joint. Examples of synovial joints include the human knee, shoulder, sternoclavicular and elbow joints.
- Fibrous joints are the articulations in which the bones are continued past dense fibrous connective tissue. The bones in fibrous joints are firmly held together then that the articulation allows negligible movement. Fibrous joints are constitute between the cranial sutures, the distal tibiofibular and cuboideonavicular joints.
- Cartilaginous joints are articulations in which the bones are connected by cartilage. The bones have a range of motion betwixt synovial and gristly joints. Cartilaginous joints are subdivided into synchondrosis (due east.chiliad. costochondral joints) and symphysis joints (e.chiliad. pubic symphysis).
According to movements they allow, the synovial joints are further subdivided into:
- Ball and socket joints (e.g. hip joint)
- Condylar joints (e.1000. human knee articulation)
- Hinge joints (east.g. elbow joint)
- Pivot joints (east.g. proximal and distal radioulnar joints)
- Ellipsoid joints (e.g. 2nd – 5th metacarpophalangeal joints)
- Plane joints (east.m. joints betwixt the carpal bones)
Ligaments
Ligaments are fibrous bands made of dense regular connective tissue which are similar in structure to tendons. Unlike the tendons that connect muscles to os, the ligaments connect bone to os. Too the musculoskeletal system, the ligaments are besides found in many other parts of the body, where they usually stabilize and concord internal organs in place and transmit neurovascular structures.
In the musculoskeletal system, ligaments stabilize the articulating basic and reinforce the joints. Depending on their anatomic position relative to the articulation capsule, ligaments are classified into:
- Capsular ligaments are substantially thickenings of the articulation capsule that form either elongated bands or triangular structures. These ligaments serve to reinforce the integrity of the articulation sheathing. An case of the capsular ligament is the iliofemoral ligament of the hip joint.
- Intracapsular ligaments are the ligaments that lie internal to the joint capsule. These ligaments reinforce the connection of the articulating surfaces of the joint, merely allow a far wider range of motion than other ligaments. Examples include anterior and posterior cruciate ligament of the genu joint.
- Extracapsular ligaments are ligaments that lie outside the joint sheathing. These ligaments provide the virtually stability to the articulating bones, and are important for preventing dislocations. Extracapsular ligaments can lie in shut proximity (eastward.thou. medial collateral ligament of the ankle joint) or a bit farther from the joint capsule (vertebral ligaments).
Bursae
Bursae are small sac-like outpouchings of the joint cavity lined by synovial membrane. They are plant around the joints, providing cushioning of the associated basic, tendons and muscles and reducing friction betwixt adjacent structures.
The majority of synovial bursae are located almost the large joints of the artillery and legs. For example, one of the bursae of the knee joint is the suprapatellar bursa, establish superior to the patella, between the femur and the tendon of the quadriceps femoris muscle. The suprapatellar bursa allows for these structures to slide over each other without friction during flexion and extension of the human knee joint.
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Functions of the skeletal organisation
The skeletal system serves a variety of functions. The basic give the shape to the body and provide the site of attachment to muscles, tendons, ligaments and cartilage. These tissues function together every bit a whole to generate a forcefulness that provides the biomechanical basis of movement.
Due to its structural integrity, the skeletal arrangement protects the internal organs, most importantly the brain, which is surrounded by the skull, besides as the heart and lungs, which are protected past the rib muzzle.
Moreover, the skeletal system serves several metabolic functions. The bones are the storage site of of import minerals, most notably calcium and phosphorus. This makes the bones essential for balancing calcium levels in the blood, which is regulated by adjusting the rate of bone resorption.
Lastly, the bone marrow establish in spongy bone is the site of hematopoiesis, which is a process of product of new claret cells. Cells that are produced in the bone marrow are red blood cells, platelets and white blood cells, such every bit monocytes, granulocytes and lymphocytes.
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Clinical correlation
There is a variety of atmospheric condition that affect the muscles, bones, and joints. Disorders of the musculoskeletal system may range from diseases to pocket-size physical disabilities. The following are some clinical conditions of the musculoskeletal system:
Osteoporosis
Osteoporosis is a condition that affects os strength (the word osteoporosis literally means "porous bones"). It is a condition in which the bones become fragile and brittle, leading to a higher chance of fractures than in normal bone. Equally a result, fifty-fifty a minor bump or accident can cause serious fractures.
Osteoporosis is the "bone of the former", especially, in women. The hard, rock-like quality of bone is dependent upon calcium. When besides much calcium is dissolved from bones or not plenty is replaced, bones lose density and are easily fractured. Estrogen, the female sex hormone, helps maintain proper calcium levels in basic. In one case the ovaries end producing the hormone, women are at higher take a chance of developing osteoporosis. A collapse of bony vertebrae of the spinal cavalcade results in loss of height and stooped posture. Hip fractures are a mutual occurrence.
Sarcopenia
Sarcopenia is a syndrome characterized by progressive and generalized loss of skeletal muscle mass and strength with a risk of adverse outcomes such every bit physical disability, poor quality of life and death.
Arthritis
Arthritis is a group of conditions affecting the joints. These conditions cause harm to the joints, usually resulting in pain and stiffness due to aging. Arthritis can affect many different parts of the joint and near every articulation in the body.
Every bit an individual ages, the joint tissues go less resilient to article of clothing and tear and starting time to degenerate. This degeneration manifest as swelling, pain, and frequently-times, loss of mobility of joints. Changes occur in both articulation soft tissues and the articulating bones, a status chosen osteoarthritis. A more serious class of affliction is chosen rheumatoid arthritis. The latter is an autoimmune disease wherein the body produces antibodies against joint tissues causing chronic inflammation resulting in astringent joint damage, pain and immobility.
Muscular dystrophy
Muscular dystrophy is a grouping of muscle diseases that weaken the musculoskeletal system and hamper locomotion. Muscular dystrophies are characterized by progressive skeletal muscle weakness, defects in muscle proteins, and the death of muscle fibres (muscle cells) and tissue.
It is a group of inherited diseases in which the muscles that control move progressively weaken. The prefix, dys-, means aberrant, while the root, -trophy, refers to maintaining normal nourishment, structure and function. The most common form in children is called Duchenne muscular dystrophy and affects only males. It usually appears between the ages of ii to 6 and the afflicted live typically into belatedly teens to early on 20s.
Other conditions involving the musculoskeletal system include:
- Lupus erythematosus
- Myasthenia gravis
- Rotator cuff tear
- Tendonitis
- Carpal tunnel syndrome
- Osteomalacia
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