What is the function of stomach?



Seconds after swallowing, food enters the stomach, the J-shaped, stretchy bag that links the oesophagus to the small intestine. While food is stored in the stomach it is churned into a creamy liquid called chime. This is released gradually into the small intestine, where digestion is completed.



Two types of digestion happen in the stomach. Firstly, food is doused in acidic gastric juice that contains pepsin, an enzyme that digests proteins. Secondly, muscles in the stomach’s wall create waves of contractions that crush and churn food into mushy chyme.



The stomach secretes acid and enzymes that digest food. Ridges of muscle tissue called rugae line the stomach. The stomach muscles contract periodically, churning food to enhance digestion. The pyloric sphincter is a muscular valve that opens to allow food to pass from the stomach to the small intestine.



 



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What is the function of abdomen and pelvis?



The abdomen contains hardworking organs from many of the body’s systems. Most of them help to digest food, clean the blood, or dispose of waste. Supporting them from beneath is a strong framework of bone and muscle called the pelvis.



The abdomen is the body region found between the thorax and the pelvis. Its superior aperture faces towards the thorax, enclosed by the diaphragm. Inferiorly the abdomen is open to the pelvis, communicating through the superior pelvic aperture (pelvic inlet). These two apertures, together with abdominal walls, bound the abdominal cavity.



The pelvis opens superiorly to the abdomen through the pelvic inlet, while its inferior opening (the pelvic outlet) is closed by the pelvic floor (levator ani and coccygeus muscles). The pelvic inlet is the boundary between the greater pelvis superiorly and lesser pelvis inferiorly.



 



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What is the function of hand?



Because humans walk upright on two feet, it leaves our hands free to take on other tasks. Human hands are incredibly versatile tools, able to perform a huge range of movements.



The hand’s adaptability is made possible by the combination of a framework of small, flexible bones, including long finger bones and a highly moveable thumb. This structure is overlain with an intricate network of muscles and tendons, which move the bones.



Hand function has great significance for occupational performance. The greater the difficulties with hand function, the greater the impairment in skills that allow for independence and participation in academic and social activities.



The human arm, supported and controlled by a large number of muscles, together with the elbow and wrist joints, gives freedom to a hand that has become the willing servant of the human intellect. The hands are, as Kant is reported to have said, "Man’s outer brain."



 



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What is the function of skeletal muscle?



Body movement is controlled by skeletal muscle. About 650 skeletal muscles move the arms, legs, fingers and toes.



The muscle is attached to the bones via flexible cords, called tendons. The series of ridges across the muscle show its two interlocking proteins, actin and myosin. When the actin slides over myosin, the muscle contracts. The darker areas show actin and myosin overlapping, while the paler areas show actin alone. When skeletal muscle contracts, its tendon pulls on bone to make the body move.



Muscles are ennervated by motor neurons. A motor neuron and the muscle fibers ennervated by it form a motor unit. Size of motor units varies in the body, depending on the function of the muscle. Fine movements (eyes) have fewer muscle fibers per neuron to allow for fine movement. Muscles that require a lot of strength have many muscle fibers per unit. The body can control strength by deciding how many motor units it activates for a given function.



 



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How to maintain muscle?



Muscles must be kept strong and healthy, so the body can move easily and function properly. Diet and exercise play a major part in building and maintaining muscle.



Muscle food



Protein, such as that found in pulses such as beans and lentils, meat, nuts, and fish, is needed for building repairing muscle. Carbohydrates such as cereals, bread, and pasta provide energy for muscles t work. A balanced, healthy diet will provide enough protein and carbohydrate for muscles to stay healthy and active.



Resistance training



Some people build bigger muscles by resistance training. Regular exercise of this kind forces muscles to contract respectively, which builds and strengthens them. It also tears muscle fibres, which then grow back bigger, weight training, gymnastics, and some kinds of dancing are all forms of resistance training.



 



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What are the types of muscle fibers?



Muscles are either fast-twitch or slow-twitch. Fast-twitch muscles contract quickly to generate lots of power. Slow-twitch muscles contract slowly and generate less power, but they work for longer without tiring. A healthy body has an equal split of fast- and slow-twitch muscle.



Slow-twitch muscle fibers have high concentrations of mitochondria and myoglobin. Although they are smaller than the fast-twitch fibers, they are surrounded by more capillaries. This combination supports aerobic metabolism and fatigue resistance, particularly important for prolonged submaximal (aerobic) exercise activities. 



Fast-twitch fibers have a high threshold and will be recruited or activated only when the force demands are greater than the slow-twitch fibers can meet. Fast-twitch fibers can generate more force, but are quicker to fatigue when compared to slow-twitch fibers. Strength and power training can increase the number of fast-twitch muscle fibers recruited for a specific movement. Fast-twitch fibers are called “white fibers” because do not contain much blood, which gives them a lighter appearance than slow-twitch fibers. 



Genetics determines how much of each muscle-fiber type you possess; however, identifying whether you are fast- or slow-twitch dominant would require an invasive muscle biopsy. Therefore, if you find that you tend to enjoy more endurance-based activities and that they are relatively easy for you, you probably have a greater number of slow-twitch fibers. Conversely, if you really dislike going for long runs, but enjoy playing sports that rely on short bursts of explosive movements, or if you like weight training because it is relatively easy, you are probably fast-twitch fiber dominant. 



 



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How muscles work?



Muscles work by contracting, which means they shorten. As a muscle contracts, it pulls on whatever it is attached to. In general, the larger the muscles, the more pulling power it has. Muscles can pull but not push, which is why they work in pairs, acting in opposite directions. When one muscle pulls, its partner muscle relaxes.



Pulling together



All the skeletal muscles work in pairs, in the upper arm, the biceps and triceps muscles work as a team to bend and straighten the arm. The triceps pulls the forearm down, and the biceps pulls it up again.



Triceps



When the triceps muscle contracts, it straightens the arm at the elbow. The biceps, opposite the triceps, is relaxed.



Muscle attachment



The triceps is attached to the shoulder blade at this point.



Firmly fixed



The biceps is attached to the shoulder blade at these two points.



Biceps



When the biceps contracts, it pulls the forearm bones up and bends the arm. The triceps muscle is relaxed.



Tendons



Muscles are firmly attached to bones by tendons.



 



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How are nerves connected to muscles?



Muscles receive their instructions from nerves. Signals from the brain travel down the spinal cord, and then go out to the muscles along nerves. Nerves branch out so they reach each part of the muscle. The signals tell the muscles to contract, and the body moves.



Nerves and muscles, working together as the neuromuscular system, make your body move as you want it to. They also make sure you do things you don’t even think about, such as breathe.



Nerves have cells called neurons. Neurons carry messages from the brain via the spinal cord. The neurons that carry these messages to the muscles are called motor neurons.



Each motor neuron ending sits very close to a muscle fibre. Where they sit together is called a neuromuscular junction. The motor neurons can release a chemical, which is picked up by the muscle fibre. This tells the muscle fibre to contract, which makes the muscles move.



 



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What are the types of muscles?



Muscles are packed full of parallel bundles of fibres. These consist of many cells, called myocytes. When they contract, the muscle shortens and so creates a pulling action. There are three types of muscle in the body.



Skeletal muscle



This type of muscle pulls on bones to move the skeleton. Skeletal muscle is made of long, cylindrical cells called muscle fibres, each crammed with threads called myofibrils. These contain long protein filaments that slide over each other to make muscles contract.



Smooth muscles



Arranged in muscular sheets, smooth muscle makes things move along inside the body. For example, it mixes food in the stomach and pushes it through the intestines. It is the weakest type of muscle but has an essential role in moving food along the digestive tract and maintaining blood circulation through the blood vessels.



Smooth muscle acts involuntarily and cannot be consciously controlled.



Heart muscles



This type of muscle is found only in the heart, where it is used to pump blood around the body. Heart muscle never gets tired, and it never stops working. This type of muscle is strong and acts involuntarily.



 



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What are the functions of muscles?



Every movement you make uses muscles. They allow you to smile, walk, lift, and run. Muscles also move blood around the body and food through the digestive system. Some muscles must be ordered by the brain to move, while others work without us even thinking about them.



The involuntary cardiac and smooth muscles help your heart beat and blood flow through your body by producing electrical impulses. The cardiac muscle (myocardium) is found in the walls of the heart. It’s controlled by the autonomic nervous system responsible for most bodily functions.



Your diaphragm is the main muscle at work during quiet breathing. Heavier breathing, like what you experience during exercise, may require accessory muscles to help the diaphragm. These can include the abdominal, neck, and back muscles.



All the muscles in your urinary system work together so you can urinate. The dome of your bladder is made of smooth muscles. You can release urine when those muscles tighten. When they relax, you can hold in your urine.



 



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What is inside a joint?



The six types of joint are all synovial joints. They allow movement while protecting the bones from damage when they move against each other. Bone ends are covered with smooth, slippery cartilage, which helps reduce friction. The space between the bones is filled with a liquid called synovial fluid. This lubricates the joint and provides a liquid cushion between the bones. Non-synovial joints, such as the sutures of the skull, do not move.



In most free-moving joints, the ends of bones do not touch each other but are held together by tough straps called ligaments. Although they held the joint together, ligaments are elastic enough to allow you to move. The ends of bones in free-moving joints are covered with smooth, slipper cartilage. The space between bone ends also contains some oily liquid. Together the cartilage and liquid allow the bone ends to slide over each other so that the joint can move smoothly.



 



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What are the types of joint?



There are six different types of moving joint in the body. Each of them allows a different range of movements. The arms and hands contain examples of all of these types of joint, but they are found in other parts of the body, too.



Plane joint



Also called a gliding joint, this is where two flat-ended bones slide against each other. This type of joint is found in the ankles and wrists.



Ball and socket



The ball-shaped head of one bone fit into the cup shape of another bone. This type of joint allows for a wide range of movement, and is found in the shoulder and the hip.



Pivot joint



This allows one bone to swivel around another. In the forearm, the ulna forms a pivot with the radius just below the elbow, allowing the arm to twist palm-up or palm-down.



Hinge joint



Just as a door hinge only allows a door to open or close, the hinge joint at the elbow lets the arm bend and straighten. The knee is also a hinge joint.



Saddle joint



This is found at the base of the thumb where two U-shaped bones meet, allowing the thumb to rotate in two directions. This enables the thumb to touch each fingertip, as well as sweep across the palm of the hand.



Condyloid joint



This joint is found in the knuckles and toes. An oval, rounded bone fits into am oval, cup-shaped bone. This enables side-to-side and up-and-down movement, so you can spread your fingers apart and move them up and down.



 



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What are flexible joints?



Wherever two or more bones meet, they form a joint. Some of these joints aren’t moveable, such as the skull, but most are flexible, allowing some movement between the bones.



Joints give skeletons flexibility for all the different ways we move our bodies – from running and jumping to pickling up objects, or sitting down. It is still the muscles that make the movement happen by pulling on the bones, but the kind of movement each joint makes depends on the shape of the ends of the bones that meet.



Flexibility varies between individuals, particularly in terms of differences in muscle length of multi-joint muscles. Flexibility in some joints can be increased to a certain degree by exercise, with stretching a common exercise component to maintain or improve flexibility.



 



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What is the function of arm and elbow?



Walking on two legs has freed our arms up to evolve a huge range of movements. The shoulder joint is the basis for arm flexibility, but the hinged elbow joint provides even more movement.



The elbow is the visible joint between the upper and lower parts of the arm. It includes prominent landmarks such as the olecranon, the elbow pit, the lateral and medial epicondyles, and the elbow joint. The elbow joint is the synovial hinge joint between the humerus in the upper arm and the radius and ulna in the forearm which allows the forearm and hand to be moved towards and away from the body.



The three bones that form the elbow joint – the humerus, ulna, and radius – interact with one another so that the forearm forms a hinge with the upper arm, and can also rotate almost 180 . These different kinds of movement are helpful when we eat, for example – the hand can reach out to pick an apple, twist it off its stem, then bring the fruit to the mouth.



 



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What muscles are used when throwing a ball?



This sequence shows the range of muscles, and the amount the shoulder rotates in order to perform a throwing action.



Preparing to throw



Muscles in the shoulder, back, and arm contract to raise the arm and pull it backwards.



Snapping forward



Just before throwing, the chest and upper arm muscles contract to lift the arm up and forward, rotating the shoulder joint.



Following through



As the ball is released, chest and side muscles contract to pull the arm down and around the body, rotating the shoulder further.



 



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