Bones Different bones in our skeleton have different functions

Bones in the axial and appendicular skeleton- The axial skeleton is composed of the skull, hyoid bone, auditory ossicles, vertebral column, sternum bones and the ribs. The axial skeleton has two purposes. The first purpose being to care and protect the organs in the dorsal and ventral cavities. The second one being giving a surface for the attachment of muscles. It also shields the nerves and blood vessels from the brain and spinal cord. The appendicular skeleton  is composed of 126 bones.  the appendicular skeleton has a upper and lower limb. The function of the lower limbs is to bear the weight of the body providing support and stability, also to allow for movement such as walking or running. The upper limbs have a different function is purpose to have the ability to rapidly change and used for many activities. Types of bones- The skeleton works in many ways to protect our organs. Different bones in our skeleton have different functions and jobs. We have 5 types of bones and they are flat, short, irregular, flat and sesamoid. Long bones as stated in their name are the longest bones in skeleton. Some examples include the Femur, Humerus and Tibia. These bones have growth plates (epiphysis) at both ends of the bone. These ends are then coated in hyaline cartilage to help shock absorption and play a part in protecting the bone. Short bones are equal in length and width. Some examples of this bone are the Carpals and Tarsals (that are in the wrist and foot bones). They are composed of a small layer of dense, strong bone with cancellous bone on the inner part with a lot of bone marrow. The purpose of this bone is to support the bone and stabilise the bone when making little movements. Flat bones-Flat bones are dense, flat plates of bones in which their leading purpose is to provide protection to the vital organs in the body or to act as a base for muscular attachment. Examples of flat bones are scapula which is the shoulder blade, sternum the breastbone, cranium the skull, the coxae the hip bone, pelvis and ribs. In adult’s majority of the red blood cells take formation in the flat bones. Sesamoid bones –The sesamoid bones are implanted into the tendons. They are small and round that are usually found in the tendons of the hands, knees and feet. Their function is to protect the tendons from fatigue due to repeating the same action over a long period of time. Irregular bones- Irregular bones can come in many different shapes and structures, hence the name. They are put into a different group as they don’t match the features of any of the other groups. Their compound shape aids the internal organs. The vertebrate in the vertebral column shields the spinal cord and the irregular bones in the pelvis the pubis, ilium and ischium protect the organs in the pelvic cavity.Composition of bones- spongy/compact, bone marrow, and how calcium is regulated inside –Spongy bones sometimes referred to cancellous bone or trabecular bone. These bones offer tissues or structures with blood vessels and they also hold red bone marrow.  Spongy bones are normally found at the ends of long bones (the epiphyses), covered with compact bones. It can also be found in the vertebrae which consist of the ribs, skull and in the bones of joints. Spongy bones as you can tell by the name are soft and weak in comparison to compact bones, however they are more flexible. This bone is given its soft appearance by a lattice-like matrix network referred to as the trabeculae. Compact bones-Compact bone usually cortical bones, they make up 80% of the human skeleton.  Compact bones have a spongy appearance that has big spaces which are found in the marrow space, the medullary cavity of the bone. These compact bones cover the cancellous bone; they are also the primary material of the long bones of the arms, legs and other bones. These compact bones are necessary for bones that need strength and rigidity. We have two types of compact bones mature and immature. The mature compact bone is layered in structures. They structural units are called osteons, they contain a blood supply for the osteocytes and the bones are set out in concentric layers around the canals. The immature compact bones don’t have osteons and they have a woven structure.  The immature compact end up being exchanged for the mature bones in a process of remodelling of bone resorption and the formation of new bones creates osteons. How is calcium regulated inside bones-?   Calcium is mainly stored in the bones and the movement of calcium in and out of the bond helps to regulate blood calcium levels. Calcium enters the bone as osteoblast to create new bone and leaves as osteoclast for the bone to break down. It’s crucial to maintain the blood calcium levels for the function of muscle contraction and membrane potentials to take place. When there’s not enough calcium blood in the body the term used is hypocalcaemia and when there’s too much calcium it’s called hypercalcemia. The hormones responsible for maintaining blood calcium levels are parathyroid hormone and calcitonin. The calcitonin is released by the thyroid glands hinders osteoclast and helps osteoblast, therefore lowering the blood calcium levels.  The parathyroid does that opposite thing by raising the blood calcium levels; it’s released from the parathyroid glands. The parathyroid hinders the osteoblasts and helps the osteoclasts, this lowers the amount of calcium the kidney releases and it causes the small intestine to absorb more calcium therefore increasing the blood calcium levels. Function of periosteum-  The periosteum is thin but it has a tough outer layer of bones. It has a lot of collagen fibres to aid the bone and to join it to the structures around it. The periosteum contains osteogenic cells which play major part in the growth and repair of bony tissue. The outer layer of periosteum is fibrous connective tissue, this makes the bone strong.  The synovial joint is given its name due to the synovial fluid that present in the joint. The hinge, ball and socket, gliding, and saddle are types of synovial joints.  The hinge can be found in the fingers and toes, the ball and socket is located in the shoulder and hip joint, the gliding is found in the radius and lunate bones, the saddle is found in the thumb joint and the pivot is found in between the axial and atlas bones, in the neck bones. the gliding joint enables smooth movement to take place in all routes. we have a gliding joint in our wrist (carpal bones). The ball and socket joints enable steady maneuvering and bending to take place in all directions without sliding, which forms accurate stability and a strong joint. The fibrous joints are fixed; this means that move at all. These joints don’t have joint cavity but they are connected by fibrous connective tissue. They are composed of dense connective tissue which is mainly collagen. An example of the fibrous joint is the skull bone. The synovial joints are slight immoveable, this means that it doesn’t allow a lot of move but does allow for a little bit. These bones have fibrous joint capsule with endless periosteum of the bones. , the outer layer has the synovial cavity and it surrounds the bones surface. This joint can be found in the shoulder bone or the hip bone. The cartilaginous joints are movable this means they are completely free to move.  They are composed of units of cartilage; this is flexible yet tough connective tissue.  These joints don’t have a lot of cavity. The joints can be found in the knees.What are tendons? Tendons are tissues that connect muscle to body parts mainly bones. Tendons are really strong, amongst one of the strongest soft tissues. Their strength is needed to withhold of muscular contractions. Tendons are composed of fibrous connective tissues and also collagen. The collagen is a protein which provides stability and strength to the tissue. What are ligaments? Ligaments are also a connective tissues, its purpose is to support internal organs and group bones together. It’s composed of collagen fibres and spindle-shaped cells known as fibrocytes. Ligaments have two main groups one which is white ligament with a lot of collagen fibres, they are stable and inelastic.  The other being the yellow ligament this has a lot of elastic fibres, this makes it strong and it means that the bones attach won’t break due to the elasticity. What do muscle fibres consist of and how are they formed? Every muscle fibres contain the same things to allow for muscle contraction and to support them. They are composed of a lot of mitochondria because the muscle contractions need ATP hydrolysis.  They also have specialised endoplasmic reticulum which stores calcium ions, it’s called the sarcoplasmic reticulum. Muscle fibres have tubular myofibrils that are composed of two myofilaments which are the thin filament, the actin and the thick filament, the myosin.  The muscle fibres also have a continuous membrane the covers the muscle fibre which is called the sarcolemma and it have invaginations called T tubules. Antagonistic muscles-These muscles function through getting shorter they do this by contracting through a process known as contraction. As muscles are joined to bones by tendons when these muscles contract, the muscles drags on the bone and the bone is then able to move if is a component of the joint. Muscles are unable to push, this doesn’t make a difference as the joint is controlled by more than one muscle. The joint being controlled by more than one muscle avoids the muscle contracting and pulling on the bone, and the bone not being able to go back to its original place. The antagonistic muscles that come in pairs prevent this from happening. The biceps and triceps are examples of antagonistic muscles.