HUBS191-Musculoskeletal system

The cells of tissue tend to be widely separated from each other. The large amounts of are found in these . Loose connective tissue keeps and epithelial in place while connective tissue forms both and tendons. tissue (fat) is also connective tissue. , bone and are also kinds of connective tissue.

tissue is arranged next to one another and there is little . The tissue protects outer surfaces (our skin) and is lines .

It is possible to palpate the whole length of the clavicle because it is more and no is covering it.

An epicondyle is a on the part of a bone serving for the attachment of muscles and .

The forearm is defined as the region from to . The forearm has two bones, the and .

Bones are made of tissue; they consist of cells embedded in an . Bones begin as preforms in infancy and as we age. Because bones are and contain cells, they have the ability to adapt and .

The of a bone is different from other types of tissue as it only consists of of organic material and of material

The outer surface of bone is covered and protected by the , a fine sheet of tissue. There are small holes in the periosteum called . The foraminae allow blood vessels and to pass into the bone and the cells. Osteocytes are found in living spaces called , trapped in sheets of known as . Each lamellae is made up of fibres that are in a specific direction. Bone has many of lamellae and their fibres run in many different directions, so bone is resistant to in many directions. Lamellae arrange themselves into -shaped structures known as .

A , through which blood vessels and pass, runs down the middle of an . Blood and nerves penetrate into the to supply the through channels called that connects to the lacunae to the central canal and to each other. These allow delivery of nutrients and of wastes.

In the middle of shafts of long bones is a cavity in which the bone marrow is found: the . Lining this is a fine sheet of connective tissue called .

Cancellous bone is comprised of the same tissue as compact bone but it is arranged quit differently. form struts of bone known as , which interconnect to form a or sponge-like structure. is found between the trabeculae. Trabeculae are thinner than , so osteocytes can communicate with each other and with nerves and blood vessels directly.

Bone growth first occurs in the ; as the bone develops, more is formed from the center towards the of bones. Then, blood vessels grow into the bone and are reshaped by s so that the central cavity contains bone marrow.

Osteocytes reside in .

Thickening, or addition of the bone, occurs at the surface, and bone is removed or resorbed (by ) at the surface.

Osteoclasts remove bone by releasing and . Enzymes break down the of the bone tissue, and acid breaks down the .

In the first stage of fracture repair, broken blood vessels lead to a formation of a (a soft ), which takes 0 to days to form. grow into the haematoma. (white blood cells) engulf the .

In stage 2 of a fracture repair, the next days to weeks, arrive through the and begin producing fibres to form a matrix of collagen. Some of these fibroblasts differentiate into . They then form a that splints the bone ends together and movement.

In stage 3 of bone fracture repair, which is during the next to weeks, transform the fibrocartilage callus () into a .

In stage 4 of fracture repair, the bone is completely and converts callus into more organized structure of bone tissue, and refashioning the bone into its original shape. This starts to happen to months after initial fracture has occurred, but it may take years to completely .

The lower the congruence, the more .

Chondrocytes are a cell; a former that has become enclosed in a in the cartilage matrix.

Cartilage is (contains no blood vessels), so and oxygen must diffuse through the to nourish the , so it takes a long time for cartilage to heal after an and it can never grow very thick.

Hyaline cartilage is and contains fibres arranged randomly throughout the . This arrangement traps and makes hyaline cartilage appear smooth. It has less and more than fibrocartilage. It covers the surfaces of bones, and also allows bone surfaces involved with a joint to move against one another and with little friction.

The extracellular matrix of connective tissue consists of fibres embedded in ground substances. are spread throughout the . The collagen is densely packed in , which makes the DFCT extremely good at resisting . DFCT is partially , it takes a long time for it to repair, but not as long as cartilage.

The shape of ends of involved in the determines the amount and type of possible at the joint. For example, the head of the allows a wide range of at the , and its deep with the hip gives the joint stability.

Articular cartilage covers the bones where they and promotes a surface.

In a synovial joint, the thickenings of capsule form the ligaments. These reinforce joints and movement where it is not . For example, the capsular ligaments at the knee joint are called ligaments and prevent and abduction.

The ligaments of a synovial joint may be divided into capsular ligaments (those that lie outside the capsule), ligaments (those that are thickened and parts of the capsule) and -capsular ligaments (those that lie within the capsule).

The hinge joint is a bone joint in which the surfaces are to each other in such a manner as to permit motion only in plane. It permits motion back and forth like a . This joint creates movement of and extension. An example of a hinge joint are the joints in the .

One type of a synovial joint, is a joint, which is . This joint allows for and pronation. An example includes the joints (both proximal and ).

The saddle joint is and creates movements such as flexion & and also abduction & , which ultimately causes . An example of this joint is joint at the base of the .

The ellipsoid joint is and causes flexion, , adduction, and . An example is the joint which is located in the .

The plane joint is and causes sliding/. The and intertarsal joints, which are between carpal and bones, are an example.

Ball and socket joints are , and therefore can cause , abduction, , extension, circumduction and . An examples include the joint and the shoulder joint.

The three types of tissue involved in the structure of a muscle are the , perimysium and endomysium. The epimysium is a layer of connective tissue that wraps around the whole muscle. The wraps around the fascicles inside the muscle. The wraps around each . All of these tissues will eventually connect to one another and form a that connects the skeletal muscle to the . Therefore, the layers of connective tissue support the muscle and transmit the of contraction to the bones.

Each skeletal muscle is comprised of and each fascicle is made up of muscle cells called . Myocytes are long , skinny and cells and are multi-. They are made of , which are made up of . Myofilaments come in two different varieties: filament of myosin and filament of . The myosin and actin proteins are arranged in a contractile units called and work together to produce muscle .

The boundaries of sarcomeres are marked by -lines. These are placed at intervals along the , and anchor the thin filaments together. The myosin filament lies in the of the sarcomere. During muscle contraction, the thick myosin filaments on the thin actin filaments, causing the to slide over the . This draws Z lines together and shortens the .

The size of a motor unit can vary. A small motor unit enables control as each only causes the contraction of a small number of . Small motor units are therefore found in muscles that move eyes and fingers. Large motor units are found in areas where fine control is not found, such as the maximus.

Activation of motor units is an 'all' or 'nothing' response: either all the innervated will contract, or none of them will. However, whole muscles can contract with different amounts of . The force of contraction depends on the number of motor units, the of potentials arriving at the motor unit and the of the motor unit.

If the muscle is to the joint, concentric action will produce flexion.

If a muscle is to the joint, concentric action will cause extension.

If a muscle is lateral to the joint, concentric action will produce .

If the muscle is to the joint, concentric action will produce adduction.

The is the variable that the system is trying to keep the same. The is the optimal target for the variable to be at. The is the range of acceptable limits of that variable.

can either be positive or negative. A loop causes an increase in response (stretch in giving birth), where as a negative loop causes a decrease in response (change in temperature).

The compares the change in the to the set point and elicits an appropriate response.

The uses mechanisms to bring about change in the controlled variable, according to information received from the .

is when a sensor senses a in the controlled variable and immediately effects a change to resist it, bypassing the integration center (anticipation). Usually is complimentary to , so any mistakes can be fixed, or response can be exaggerated. An example of this is gag reflex.

Flexion and extension occur on the . Abduction and adduction occur on the .

bone has a high surface area to mass ratio, as it is less than compact bone. The main functional unit is the , which are aligned towards the distribution of mechanical force on the bone, helping to absorb the . Often found in the of the bone.

originate from osteoblasts once they become trapped in the . Their function is to maintain tissue. Osteoblasts originate from cells and are found in areas of growth. Their function is to secrete bone . Osteoclasts originate from and their function is to bone tissue during the remodeling and healing of bone.

Each lacunae is connected to one another via .

A fracture occurs when bone tissue is broken as a result of external force. Bone tissue is highly vascularized and so there is often a lot of associated with the injury. Bone tissue also has an extensive supply which is why there is a lot of pain involved with a fracture. The first stage is , which is when a blood clot forms around the site of injury to stop excessive bleeding. This is important because excessive blood leads to death and reparative cells arrive to the site of injury through . A process known as then occurs to increase supply to the fracture. arrive from the blood capillaries and clean up the dead tissue and debris. After that, stage 2 occurs when the callus forms. arrive at the site of injury where they differentiate into . The chondrocytes secrete a matrix forming a fibrocartilaginous callus (this callus is soft because it is made up of cartilage, not bone). Stage three is when the callus forms; the turn fibrocartilaginous callus into a hard boney callus is a process known as ossification. The last stage is when and osteoblasts work together to remodel the bone into its normal .

Fibrocartilage are high quantities of bundles aligned towards the or pressure. Main function is to resist . Found where some movement is required but is also needed, for example the of the knee joint.

Muscle form depends on three factors:

1) Length of muscle fibres: muscle fibres = larger .

2) Number of muscle fibres: higher number of fibres means more can be generated, thus more strength

3) Arrangement of muscle fibres: Fibres can be parallel or .