The musculoskeletal system

Question 1

-what is the role of the skeleton?

Answer 1

• Acts as a framework for the body: bones of the skeletal system provide attachments or soft tissues and organs
• Protect delicate structures: essential organs such as the brain and spinal chord protected from direct injury
• Bones act as levers: bones and their associated joints dictate the range of movement in the body
• Bones provide storage: bones store and act as a calcium reserve

Question 2

what are the 2 types of skeleton?

Answer 2

• The AXIAL skeleton (midline) provides stability and consists of the cranium, vertebral column (spine), ribs and sternum.

• Protects the brain, spinal cord, heart and lungs.
• Provides anchor points for muscles that move the head, neck and back, and for muscles that act across the shoulder and hip joints to move their corresponding limbs.

• The APPENDICULAR skeleton: consist of bones from the extremities such as the Fe,ur Humerus. Clavicles and Scapula.
-Also consists of the bones that attach directly to the Axial skeleton. The upper section allows humans to grasp and manipulate objects. Lower allows for locomotion.

Question 3

how many bones does the skelton as a whole have?

Answer 3

• The skeleton as a whole has 206 bones- 80 axial, 126 appendicular

Question 4

Bones are “replacement tissues”…what does this mean?

Answer 4

• Bones are “replacement tissues” so uses a model tissue on which to lay down its mineral matrix, the model tissue is cartilage.

• Throughout foetal development and into growth, this bone then forms on the cartilaginous matrix.
• Ossification describes the process of laying down bone over the cartilage structure.

Question 5

what are osteoblasts and what do they do? what are osteocytes in relation to this?
what are canaculli?

Answer 5

• Osteoblasts are the cells that lay down structure, repair and remodel damaged bone.

• Eventually, they get surrounded and confined in bone in small chambers” lacuna”.
• Osteoblasts confined in the minerals they secrete are “ Osteocytes”.
• Osteocytes communicate with others through small channels in the lacuna, called “Canaliculi”. These allow nutrients and waste products to pass to/from osteocytes.
• Even though confined, osteocytes are the most abundant type of cell in mature bone and live as long as the bone they occupy. Essential for remodelling and bone health.

Question 6

what is ossification?

Answer 6

-Ossification describes the process of laying down bone over the cartilage structure.

Question 7

what are osteoclasts responsible for?

Answer 7

• While osteoblasts and osteocytes are responsible for bone formation. Osteoclasts, produced in the bone marrow are responsible for the large scale removal of bone. Bone is continuously being broken down and restructured in response to such influences as structural stress (e.g. injury/physical exercise) and the body’s requirement for calcium.

Question 8

what are the main bone cells and what do they do IN SIMPLE TERMS?

Answer 8

• Osteoblasts: build bones. Make osteoid made of collagen, then secrete alkaline phosphatase to make sites for calcium and phosphate deposition so bone mineral crystals grow so that the osteoid gets mineralised and forms a bone.
• Osteocytes: maintain bone tissue. Main role is homeostasis the correct oxygen and mineral levels in the bone.
• Osteoclasts: break down tissue and responsible for reabsorption. Travel to specific sites on surface of bone and secrete phosphotase to unfix calcium in mineralised bone to break it down.

Question 9

How do bones grows in length?

Answer 9

• Long bones have epiphyseal plates at either end, they are where growth occurs. Epiphyseal plates contain a layer of hyaline cartilage where ossification (laying down new bone) occurs in childhood.
• On the epiphyseal side of the epiphyseal plate (the outer side facing away from the centre of the bone), cartilage is formed.
• On the diaphyseal side (the inner side facing toward the centre of the bone), this cartilage is ossified, and the diaphysis grows in length.
• As the epiphyseal plate continues to lay down cartilage replaced on the diaphyseal side, the plate continues to move away from the centre of the bone, increasing the bones length.
• AKA cartilage is replace by the bone on the dia side of the epiph

Question 10

when does bone length stop?

Answer 10

• When no new cartilage is produced at the epiphyseal, bone growth (length) stops. The epiphyseal plate becomes the epiphyseal line. Growth terminates between ages 12–16 for girls and 14-19 for boys.

Question 11

what are the different types of bones

Answer 11

• Short bones
 Shaped roughly like a cube and made of spongey bone. Outside comprised of a thin layer of compact bone. Short bones located in hands/feet. Patella (kneecap) is a short bone.

• Flat bones
Bones who have the primary function is either extensive protection or the provision of broad surface for muscular attachment.
Bones are expanded into broad, flat panes, as is the cranium. The ilium (pelvis), sternum and the ribcage.

• Irregular bones
Complex shapes. The spine is the place in the human body where the most irregular bones can be found. Total 33 there.

• Sesamoid bones
A bone embedded in a tendon. Only a few in the body e.g patella

Question 12

what are joints?

Answer 12

-The bones of the body come together to form joints thus movement. The type and extend of movement depends on the structure and function of the joint. The form and function of joints, allows them to be grouped into 3 main classes. The degree of mobility increases from fibrous to synovial.

Question 13

what are fibrous joints?

Answer 13

• Fibrous
-Fibrous joints are connected by dense connective tissue consisting mainly of collagen. The bones are direct connected to each other and do not have a moveable joint. Sutures in the skull are fibrous joints, they connect bone, but DO NOT allow movement.

Question 14

what are cartilaginous joints?

Answer 14

• Cartilage is a resilient and smooth elastic tissue, a rubber like padding that covers and protects the ends of long bones at the joints, in cartilaginous joints the two bones are united by a continued pad of cartilage.
• The joints allow more movement that fibrous but less that synovial. This type of joint forms the growth regions.

Question 15

what are synovial joints?

Answer 15

• Freely mobile joints, with movement limited by ligaments, muscles and joint capsules crossing the joint.
• Most limb joints are synovial. Synovial joints also contain cartilage to allow bones to move against eachother with minimal friction.
• Also contain synovial membranes, they secrete synovial fluid within the joint to lube and nourish the cartilage and bone surfaces.

Question 16

what are facet joints?

Answer 16

These are hinge-like and link vertebrae together. Located in back of spine (posterior) and are synovial. Help the spine to bend, twist and extend in different directions. Enable movement but also restrict excessive movement such as hyperextension and hyperflexion, each vertebra had 2 sets of facet joints.

Question 17

what is facet joint sydrome?

Answer 17

• Because they’re always in motion they degenerate over time. The stress on the facet joints increases further as the intervertebral disc degenerates and becomes thinner. This results in inflammation formation of spinal bone spurs, leading to arthritis of the facet joint and facet syndrome.
• Arthritic joints can produce pain and reflective muscle spasms

Question 18

what are ligaments?

Answer 18

• Ligaments are tendons are both made of connective tissue and both can be torn or overstretched, but they differ in function. Ligaments attach one bone to another. Tendons attach a muscle to a bone. Both needed for proper body mechanics.

• Ligaments are like a rope- with elastic fibres that allow the joint to move, but not enough to move beyond its capacity.
-Example: The knee joint has 4 major ligaments, one on each side of the knee and two that run diagonally across the front and back of the kneecap. The help to stabilise the knee and keep it from moving too far to the left or right, f/b.

Question 19

what are tendons?

Answer 19

• Tendons are also tough cords but have more give. Also help absorb some of the impact muscles take as they spring into action.

Question 20

how much of adult body weight do muscles make up?

-what are the 3 main types?

Answer 20

There are 3 varieties: involuntary or involuntary, striated or non-striated.

• Involuntary muscles are not under conscious control e.g. heartbeat. Voluntary muscles are under conscious control e.g. deciding to move your forearm.
• Striated striped) muscle are long, elongated fibres aligned to produce a constant directional tension. Non-striated muscles lack striations and are not under voluntary control.

Question 21

muscles have 4 functional characteristics which are?

Answer 21

• Contractility: capacity to contract or shorten forcefully.
• Excitability: responds to stimulation by the nervous and endocrine systems.
• Extensibility: can be stretched to normal resting length and beyond to a degree.
• Elasticity: is muscles are stretched they recoil to their OG length.

Question 22

what are the different types of muscle?

Answer 22

• Smooth muscle: Forms the muscular layers in the walls of blood vessels and hollow organs, such as the stomach. Non-striated and involuntary, they contract slower and do not fatigue easily, they are less powerful than skeletal muscles.
• Cardiac muscle: Found only in the walls of the heart myocardium). Cardiac muscles are striated and are not under voluntary control.
• Skeletal muscle: Striated voluntary muscles, which means that we can actively control its function. Skeletal muscles support skeletal movement, maintain posture and generate heat.