Additional A & P Knowledge Lesson 57 Unit 1 Additional A & P Knowledge

Aims of the Session This session will allow candidates to have an understanding of the neuroendocrine system, its functions & effects of massage on it.

Learning Outcomes By the end of the lesson the candidate will be able to Explain the 4 stages of bone repair Explain two characteristics of tendons & ligaments Describe the 4 main stages of the sliding filament theory

Bone Repair

4 Stages of Bone Repair Inflammation Stage The Inflammation Stage begins the moment the bone is broken and lasts for around five days. Bleeding at the fracture site is what causes immediate swelling and bruising in the area. The damaged bone tissue at the edges of the fracture fragments die back and the dead cells release chemicals which initiate the healing process. Osteoclasts work to remove the dead bone cells. Within hours of the fracture, the blood from the fracture fragments forms a mesh of clotted blood. The mesh contains special cells called Fibroblasts, which begin to lay down tissue called Granulation tissue between 4 and 10 days after the fracture occurs. The Granulation tissue forms a 'scaffold' between the two fragments, from which the formation of a Soft Callus can begin.

4 Stages of Bone Repair Soft Callus Formation Stage The chemical and metabolic reactions that produce the Soft Callus begin a few days after the bone is broken. Fibroblast cells that are present in the Granulation tissue begin to form Cartilage and Fibrocartilage. This is a spongy collagen material that fills the gap between the two fracture fragments. After a couple of weeks, despite being quite fragile, the Soft Callus provides sufficient stability at the fracture site for new blood vessels to begin forming and for Osteoblasts at the Periosteum (the outer surface of the bone) to begin laying down what is called 'Woven bone'.

4 Stages of Bone Repair 4 Hard Callus Formation Stage From two to three weeks onwards a process begins whereby the fragile cartilage material of the Soft Callus is transformed completely into ‘woven bone’ through osteoblasts laying down new bone tissue. This process typically continues for between six and twelve weeks. Hard Callus formation is a complex process that is guided by the release of mineral compounds such as Calcium and Phosphate into the Cartilage tissue, which subsequently transforms into a bridge of Hard Callus over the fracture site.

4 Stages of Bone Repair 5 Bone Remodelling Stage Bone Remodelling begins once the fracture has united and may continue for several years, as a continuum of normal bone function. Bone is laid down where it is needed by Osteoblasts and removed by Osteoclasts, causing a change in the hard callus woven bone which is gradually replaced by Lamellar bone due to osteoblast and osteoclast work. Ultimately, once the fracture healing process is complete, the bone should be at least as strong as it was originally.

Tendons & Ligaments

Characteristics of Tendons Tendons are tough bands of connective tissue found in the joints. They extend from the end of muscular tissue to connect muscles to bones. Tendons are designed to only stretch a small amount. Each muscle has tendons attached at each end. Their job is to transmit force between the bones and the muscles. Tendons have a poor blood supply.

Characteristics of ligaments Ligaments connect the bones to each other, and are designed to help stabilize the joints and provide a structure for the bones. They are tough, white, non-extensible fibrous tissue. Their fibres are strung together like a cord or strap. Since they have limited stretching ability, they limit how far a joint moves to help protect against injury. They have a very poor blood supply.

Sliding Filament Theory

Sliding Filament Theory Cocking Phase ATP is broken down, releasing energy which primes the mysoin head into a cocked position, Binding Phase Calcium ions are released from the sarcoplasmic reticulum and release the binding sites on actin to allow the myosin head to attach.

Sliding Filament Theory Power Stroke The myosin head rotates, pulling the actin towards the centre of the sarcomere to generate tension/muscle contraction, Re-setting ATP binds to the myosin head, releasing it from the actin binding site.