Make-Up of the Human Body PDF

MAKE-UP OF THE HUMAN BODY The systems of the human body System is an arrangement of organs closely allied to each other and concerned with the same functions. A system is made up of organs which in turn are made up of cells. The cell of the human body is the biological basis of life. These c...

MAKE-UP OF THE HUMAN BODY The systems of the human body System is an arrangement of organs closely allied to each other and concerned with the same functions. A system is made up of organs which in turn are made up of cells. The cell of the human body is the biological basis of life. These cells are alive, and so they have to take in food and oxygen and give off waste material. 1. The skeletal system The skeletal system consists of bones of the body and the connective tissues that bind them. It performs the functions of: support, protection, and motion. Movement is made possible by the joints which are basically of two kinds: ball and socket joints, and hinge joints. Examples of ball and socket joints are those of the shoulder and hip. The movements made possible are rotation, circling and twisting. The hinge joints are those of the elbow, knee, or finger. The movements made possible are stretching and bending. Ball and socket joint Hinge joint Function The skeleton serves 6 major functions. Support The skeleton provides the framework which supports the body and maintains its shape. The pelvis and associated ligaments and muscles provide a floor for the pelvic structures. Without the ribs, costal cartilages, and the intercostal muscles the heart would collapse. Movement The joints between bones permit movement, some allowing a wider range of movement than others, e.g. the ball and socket joint allows a greater range of movement than the pivot joint at the neck. Movement is powered by skeletal muscles, which are attached to the skeleton at various sites on bones. Muscles, bones, and joints provide the principal mechanics for movement, all coordinated by the nervous system. Protection The skeleton protects many vital organs: The skull protects the brain, the eyes, and the middle and inner ears. The vertebrae protects the spinal cord. The rib cage, spine, and sternum protect the lungs, heart and major blood vessels. The clavicle and scapula protect the shoulder. The ilium and spine protect the digestive and urogenital systems and the hip. The patella and the ulna protect the knee and the elbow respectively. The carpals and tarsals protect the wrist and ankle respectively. Blood cell production The skeleton is the site of haematopoiesis, which takes place in yellow bone marrow. Marrow is found in the center of long bones. Storage Bone matrix can store calcium and is involved in calcium metabolism, and bone marrow can store iron in ferritin and is involved in iron metabolism. However, bones are not entirely made of calcium,but a mixture of chondroitin sulfate and hydroxyapatite, the latter making up 70% of a bone. Endocrine regulation Bone cells release a hormone called osteocalcin, which contributes to the regulation of blood sugar (glucose) and fat deposition. Osteocalcin increases both the insulin secretion and sensitivity, in addition to boosting the number of insulin-producing cells and reducing stores of fat. Divisions of the skeletal system The skeleton is divided into the axial skeleton and the appendicular skeleton. The axial skeleton includes the bones of the skull, the hyoid bone, the bones of the middle ear, the vertebral column, and the bony thorax. The appendicular skeleton includes the bones of the extremities and the bones of the hip and shoulder girdles. Axial skeleton The axial skeleton (80 bones) is formed by the Vertebral column (26), the Rib cage (12 pairs of ribs and the sternum), and the skull (22 bones and 7 associated bones). The axial skeleton transmits the weight from the head, the trunk, and the upper extremities down to the lower extremities at the hip joints, and is therefore responsible for the upright position of the human body. Most of the body weight is located in back of the spinal column which therefore have the erectors spinae muscles and a large amount of ligaments attached to it resulting in the curved shape of the spine. The 366 skeletal muscles acting on the axial skeleton position the spine, allowing for big movements in the thoracic cage for breathing, and the head. Conclusive research cited by the American Society for Bone Mineral Research (ASBMR) demonstrates that weight-bearing exercise stimulates bone growth. Only the parts of the skeleton that are directly affected by the exercise will benefit. Non weight-bearing activity, including swimming and cycling, has no effect on bone growth. Appendicular skeleton The appendicular skeleton (126 bones) is formed by the pectoral girdles (4), the upper limbs (60), the pelvic girdle (2), and the lower limbs (60). Their functions are to make locomotion possible and to protect the major organs of locomotion, digestion, excretion, and reproduction.  2. The muscular system The muscular system consists of the striated (skeletal) and the unstriated (smooth) muscles.the main function is to cause movement by contraction. the musculature of the human body is essential to movement. There are three distinct types of muscles: skeletal muscles(striated muscle, cardiac or heart muscles, and smooth (non-striated) muscles. 1. Skeletal muscles gives shape to the body and are essential in performing physical movements. They account for about 40 percent of body weight. They work in pairs, while one contracts, its counterpart extends. When it contracts, bones are pulled by tendons, which attach muscles to bones. Muscles that bend a limb at the joint are called flexors; those that straighten a limb are called extensors. 2. Cardiac muscle are special type of striated tissue that forms the walls of the heart. 3. Smooth muscles is located in such places as the intestines and blood vessels. Are controlled directly by the autonomic nervous system and are involuntary, meaning that they are incapable of being moved by conscious thought. Functions such as heart beat and lungs (which are capable of being willingly controlled, be it to a limited extent) are involuntary muscles but are not smooth muscles. Muscles provide strength, balance, posture, movement and heat for the body to keep warm. Muscles are also responsible for moving bones, pumping blood, moving food through the digestive system and controlling air movement in and out of your lungs. (Glencoe Health) STRUCTURE OF MUSCLE A muscle consists of a mass of fibers grouped together. A muscle fibers are made up of smaller fiber called myofibrils. Thick and thin filaments make up each myofibril. The thick filaments are made up of the protein myosin while thin filaments are made up of protein actin. Myofibrils are divided into sections called sarcomeres. Muscle tissue has four main properties: Excitability (ability to respond to stimuli), Contractibility (ability to contract), Extensibility (ability of a muscle to be stretched without tearing) and Elasticity (ability to return to its normal shape). Through contraction, the muscular system performs three important functions: Motion To understand how the muscles combine with the skeleton in providing motion we must look at the basic mechanics of movement. The main framework of the body is covered by muscle, whose function is to permit movement. We know that to move or lift a load against another force, it is easier to use levers, and it is this principle which the musculoskeletal system adopts and which we must examine. Heat production Muscle contractions produce heat and as much as 70% of body heat is produced by energy produced in muscle tissue. Blood is an essential element in temperature control during exercise, taking heat from the body core and working muscles and redirecting it to the skin when the body is overheating. When the internal heat of the body reaches too low a level thermo receptors in the skin relay a message to the hypothalamus in the brain. In response to this signal, the skeletal muscles contract and relax in an involuntary manner (shivering) increasing muscle activity to generate heat. In turn, muscles are also responsive to exterior heat - cold air increases muscle tone, and hot conditions have a relaxing effect on muscles. Maintenance of posture As well as enabling movement, muscles also maintain posture and body position. Sensory receptors in the muscles monitor the tension and length of the muscles and provide the nervous system with crucial information about the position of the body parts, therefore enabling posture to be maintained. Muscles are never completely at rest, nor do they actually have to shorten in length when they contract. The tension or tone produced as a result of these contractions between various opposing groups of muscle helps us remain in a static position, even when we are asleep. What makes muscles Contract? Skeletal muscles, attached to bone by tendons, produce movement by bending the skeleton at movable joints. The connecting tendon closest to the body or head is called the proximal attachment: this is termed the origin of the muscle. The other end, the distal attachment, is called the insertion. During contraction, the origin remains stationary and the insertion moves. The force producing the bending is always exerted as a pull by contraction, thus making the muscle shorter: Muscles cannot actively push. Reversing the direction in which a joint bends is produced by contracting a different set of muscles. For example, when one group of muscles contracts, an antagonistic group stretches, exerting an opposing pull, ready to reverse the direction of movement. The contracting unit is the muscle fiber. Muscle fibers consist of two main protein strands - actin and myosin. Where the strands overlap, the fiber appears dark. Where they do not overlap, the fiber appears light. These alternating bands of light and dark give skeletal muscle its characterisitc striated appearance. The trigger which starts contraction comes from the motor nerve attached to each muscle fiber at the motor end plate.