Essay: Musculoskeletal System

1 Introduction
This report covers tasks 1-3 of the musculoskeletal system. Task 1 will cover the identification of the main parts of an adult skeleton, using diagrams and tables there will be details of a long bone and its structure. There will also include an explanation of the different properties of bone and cartilage, and how bone develops from birth to adulthood. Task 2 covers joints and the different types in the body with the range of movement for each joint. Lastly, Task 3 describes the gross and microscopic structure of striated muscles and a diagram of the sliding filament hypotheses.
2 Task 1 Skeleton
2.1 Write a short summary of how bones are used to help the body move (1.1) – Diagram 1
Bones not only support the skeleton and protect vital organs but they play a big part in how the body moves. Bones will not be able to move without the aid of muscles. Bones also help us with weight bearing which allow us to stand and hold our heads up. Bones are strong and especially the appendage bones like legs and arms. The muscles and bone in these areas have to be really strong and according to Jones and Jones many bones have approximately four times the compressive strength of concrete. The joints in bones help us to move but they also prevent dangerous movements too. There are three different levers within bone movement. First class lever where the effort is at one end the load is at the other, fulcrum in the middle for example a pair of scissors is a good example of a first class lever. Second class lever would have the effort at one end and the fulcrum at the other with the load in the middle. A wheelbarrow would be a good example of a second class lever. Movement includes standing on tiptoes. Third class lever would have the load at one end fulcrum at other end and force in the middle for example a pair of tweezers and lifting using bicep would be a good example of a third class lever.
(Jones and Jones, 1997).
2.2 Structure of a long bone – See diagram 2 (3.1)
A few examples of a long bone are the femur, radius and phalanges. They consist of an elongated body Diaphysis and two ends the proximal epiphysis and the distal epiphysis. (Jones and Jones, 1997)
Medullary Cavity:
Central cavity is found in the centre of the long bone. This is where the lipid rich yellow bone marrow can be found and is protected by the medullary cavity.
Yellow Bone Marrow:
This is where blood cells are made. Bone marrow in children is red but yellow in adults.
Blood vessels:
Like rivers inside the bone through which the blood circulates carrying the nutrients and minerals.
Compact Bone:
Dense bone tissue which protects the spongy bone from pressure and shock
Spongy Bone:
Tissue made of compartments, like holes, separated by cavities that are filled with bone marrow, blood vessels and nerves. This material gives bones their light weight.
Articular Cartilage:
Smooth elastic tissue which allows bones to connect with other bones. It helps with movements and absorbs shock.
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2.2a Make a table that lists the different properties between bone and cartilage: (1.3)
Bone Cartilage Differences
Type There are two types of bone in terms of material, either spongy or compact and they are classified under shape. You have Long bones, short, flat irregular sesamoid and sutural bones. There are three types of cartilage. Hyaline cartilage which is found bronchial tubes, larynx, nose and trachea and in the end of long bones It provides arrangement and movement. Fibrocartilage is tough and can be positioned in between discs and joints such as the knee and hip and provides firmness and structure. Then there is Elastic cartilage which is found in the external ear, auditory tubes and the epiglottis Bone is hard and living tissue that forms the skeletal structure of the body. Cartilage is not as hard and rigid as bone.
Function Bones do many different things, they support the whole body enabling us to stand and sit and move, essentially providing a framework and shape for our bodies. They also protect organs for example the ribs protect your heart and lungs etc providing protection from mechanical damage. Bones is a living tissue and it provides a place for storing essential minerals and helps to produce red and white blood cells. Cartilage has many functions too. It helps to reduce friction at joints. Due to the material it supports the respiratory tract. It acts shock absorbers between joints and weight baring bones. Cartilage also maintains the shape and flexibility of fleshy parts like our ears and nose. The function of bones in our bodies is support, protection, movement. They also provide storage for minerals like calcium and phosphorus. Bone marrow which produces Red blood cells (erythrocytes) and white blood cells (leucocytes). The function of cartilage includes reducing friction at joints, supporting tracheal and bronchial tubes, shock absorbers between vertebrae and flexibility of the ear and nose etc.
Structure A bone is vascularised which means it has a blood supply. They are made up of osteoblasts which are cells that secrete the matrix for bone formation. They are also made up of osteoclasts that are large cells that absorb bone tissue during growth and healing. Osteocytes are a mature bone cell once the osteoblast has become embedded in the matrix. Bone is also made up of 25% water, bone cells, collagen fibres, phosphate and calcium which allow the bone to be hard. GAG proteins are also present in bone. Ostyonectin is another protein found in bone but not cartilage this is a bone connecting protein. Another protein found in bone is Ostyocalcin which binds calcium. Cartilage is avascular which means it doesn’t have its own blood supply. Chondroblast are cartilage forming cells that make cartilage proteins a dividing cell of growing cartilage tissue which once matures becomes Chondrocytes, a cell that has secreted the matrix of cartilage and become embedded into it, there is also present in this structure a dense matrix of collagen and elastic fibres which help the chondrocytes embed. Cartilage is also made up of 70% water, cartilage cells and fibroblasts, collagen and elastin fibres, polysaccharides (sugars) and glycosaminoglycan (GAG) Proteins
Bone contains blood vessels and cartilage doesn’t. The Matrix of bone is made up of compact bone, spongy bone and bone marrow containing blood vessels. Bones contains phosphates and calcium. Cartilage produces an extracellular matrix consisting of collagen fibres and elastin fibres.
In bone development. The cartilage in bone slowly disappears making room for hardened bone. During bone development in children this has its benefits. For a child to sustain the trips and falls they endure it is much safer for their, for example, Patella to be constructed of cartilage as it is more flexable than bone.
Fibrous Covering Periostium which is a layer of vascular connective tissue rich in nerve endings It envelopes the bones but not on the surfaces of joints Perichondrium which is a layer of connective tissue that surrounds the cartilage where it is not a joint. These connective tissues are different as they have to connect to different tissues.
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2.3 Stages of Bone Development – See Diagram 3 (1.3)
3 Task 2 Joints
3.1 Design a table to show all different types of joints in the body, their range of movement and where they can be found. Including all Synovial joints. See Diagram 4, 4.31 and 4.2 (1.2)
Joint Type Range of Movement Location in Body
Gliding Synovial Joint Two plates sliding across each other Carpal Bones of the wrist
Condyloid Synovial Joint Similar to gliding joints but they differ because the shape is more irregular and is like two bowls fitting together Radio carpal joint of the wrist and fingers and toes.
Saddle Synovial Joint Two bones that fit together like rider and a saddle and allow bending motion in different directions without sliding. Thumb
Hinge Synovial Joint Hinges formed between two bones and allow the movement of flexion and extension without sliding or aberration Elbow, knee
Ball and Socket Synovial Joint Stable movement in many directions without slipping Hip, Shoulder
Pivot Syniovial Joint Rotational motion without gliding or slipping First and second cervical vertebrae, allows the head to move whilst keeping the neck and back stable.
Fiberous Joints Sutures Syndesmoses, Gomphoses Sutures and Gomphoses joints are immovable or fixed joints. Syndesmoses joints are slightly movable but still classified as fibrous joints. Sutures found in the Skull and Gomphoses joints are found in the mouth holding teeth in place. Syndesmoses joints Found between the tibia and fibula
Cartilageous Joints Synchondroses (Primary) SYmphyses (Secondary)` Where two bones connect but is made of cartilage and allows for limited movement but more movement than a fibrous joint and less than a synovial joint This kind of joint can be found in between every vertebrae and in long bones that are still growing.
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4 Task 3 Muscles
4.1 Describe gross and microscopic structure of striated muscle – See diagram 5 and 5.1 (2.1)
There are three types of muscle, skeletal, cardiac and smooth. Striated skeletal muscles are cylinder in shape and need lots of energy for movement they contain many Nuclei and many Mitochondria which is why these muscles tire easily. They have many fibres which are made up of myofilaments, which are the filaments of myofibrils which are principally the proteins myosin or actin. They are covered by a connective tissue called sarcolemma which is effectively a transparent tubular sheath. Once the muscle fibres reach their smallest these are called sarcomere. The myosin which are thick and actin fibres, which are thin, slide across each other allowing muscles to contract and stretch.
Diagram 4 shows a skeletal muscle in its gross state and under a microscope. The gross state shows the muscle broken down and once each muscle fibre is pulled back you reach the sarcomere. The microscopic picture shows the sarcomere overlapping when the muscle is relaxed and contracted you can see the difference.
(Jones and Jones,1997)
4.2 Explain the Sliding Filament hypothesis of muscle contraction. See Diagram 5 2.2
When muscles contract the sarcomeres become smaller but they do not change in length, they slide past each other and overlap. The actin filaments slide between the myosin filaments. See Diagram 6 for an annotated explanation. (Jones and Jones, 1997).
5 Conclusion
With the aid of diagrams and tables Tasks 1-3 have been identified. The Skeletal system is very complicated with many different aspects helping us to move. The differences between bone and cartilage are varied with bone being hard and cartilage flexible, both are as important within our bodies. Throughout growth our bones are changing all the time with the cartilage being replaced by bone at all stages of development and renewing bone throughout our lives.
The many different types of joints we have to enable the range of movement are vast and complicated and covered in this report. Finally the structure of our muscles and the explanation of how these move with the sliding filament hypotheses explains how our striated muscles work and under a microscope shows how intricate this is and why our skeletal muscles require so much energy to work.