Lecture 3 - Bones Flashcards
What makes up the Skeletal System?
Bones, Cartilages, Joints, Ligaments (strip of connective tissue that surrounds joint to keep the joint stable) and other connective tissues.
What are the functions of the skeletal system?
Support against gravity,
storage (Calcium (95% stored in bone without calcium muscles cant contract so the heart wont beat, when calcium is needed in the blood/body its released), phosphorous, fat),
Blood cell production (blood cells are produced in bone marrow by metabolic active tissue),
Protection of soft internal organs (skull protects brain and ribs protect thoracic organs)
Leverage for muscle action.
Describe flat bones
Flat bones= it has an external table and internal table which is separated by dipole, good rigid protection, has a double layer giving extra strength in case of impact but is still light. They’re thin, have parallel surfaces and are found in the ribs and shoulder blades.
Describe the long bones
Longer than they are wide, arms, legs, fingers and toes have these bones, useful for leverage.
Long part of the bone is called the diaphysis (shaft), made up of compact bone on the outside and a medullary cavity running through the middle. The Epiphyses (ends) are at the end of the bone have compact bone on the outside and have the trabecular (spongy) bone in the middle, this bone joins to the joints. These are usually covered by articular cartilage.
Describe short bones
Short bones = width is equal to length. Bones are in wrists, tightly fitted together but can slide slightly allowing more suppletory of movement.
Describe irregular bones
Irregular bones= complex shapes, the vertebra, bones in the pelvis and some bones in the skull have these bones, bones stack up giving support and protection of the spinal cord.
Describe sutural bones
Sutural bones= found between flat bones in the skull, they’re small, flat and oddly shaped.
Describe sesamoid bones
Sesamoid bones= Small, round, flat and develop in tendons, is found the knee cap (patella).
What’s the microscopic structure of bone?
- Ground Substance= two thirds of bone matrix and is made up of minerals, a prominent mineral is hydroxyapatite which contains calcium salts and ions.
- Protein= this reinforces the bone and is mainly made up of collagen fibres and makes it less brittle, this one third of the bone matrix
- Bone cells= only 2% of bone mass, these contain mesenchymal stem cells which turn into osteoblasts cells (which ar bone builder cells), these then turn into osteocytes (adult bone cells) and there’s osteoclasts which dissolve away old bone. The osteocytes are found within lacunae, lacunae are organised around blood vessels.
- In the bone cells (osteocytes) there’s also narrow passageways running through the matrix which form a network so nutrients and waste products etc, can be exchanged.
What are Osteoblasts?
Osteoblasts =they make proteins in bone which is a jelly like substance before its mixed with the mineral part and it’s a surface bone. Also produce new bone matrix either by ossification or osteogenesis
What are Osteocytes?
Osteocytes are mature bone cell maintaining the bone matrix, it’s has a cell body with branching arms (called canaliculi) that allow nutrients to diffuse around, stores minerals, detects damage and knows when old bone needs dissolving.
What are Osteoclasts?
Osteoclast= has lots of nuclei, big surface area that has acids and enzymes which break down mineral and fibres to dissolve the bone, this releases stored minerals. The erosion process is called Osteolysis and it’s useful for regulating the calcium and phosphate ion concentration in body fluids.
What’s compact bone?
Compact bone has a very dense structure with lacunae in it, Osteons are parallel to each other with a hole running down the middle in a central canal, the central canal is responsible for the blood supply (contains blood vessels) running to the bones. Also, there’s perforating canals which supply blood to deeper areas in the blood and tissue, these run perpendicular to the surface. Lamellae are concentric layers of matrix running around the outer bit of the bone. The collagen fibres line up in different directions to give maximal strength and resiliency.
Compact bones are strongest when the forces applied to it are coming from the same direction, along the same axis.
What’s trabecular (spongy) bone?
Trabecular (Spongy) Bone = it has no osteons but does contain trabeculae, bundles of supporting fibres, which branch in lots of different directions, run in different direction which increases strength but its lighter than compact bone, making it easier for muscles to move. Trabeculae is found in areas where there’s less stresses There’s red bone marrow which is between trabeculae and they form red blood cells and provide nutrients to the osteocytes.
Yellow bone marrow is found in the medullary cavity and this stores fat. There are canaliculi on the surface which provides diffusion between the blood and bone.
What’s Periosteum?
Periosteum is on the outside of the bone and is a membrane, the outer layer (fibrous) is made of collagen fibres which are continuous with bones, joints, ligaments…
It covers the compact bone but the medullary cavity. The role of the Periosteum is to isolate the bone from surrounding tissues, provide a route for blood vessels and nerves and take part in bone growth and repair.
At joints, the periosteum becomes continuous with the connective tissue that’s holding the bone in place. The periosteum fibres also entwine with tendons so that when they grow, they become part of the lamellae. Collagen fibres also get joined into bone tissue from tendons and ligaments are called perforating fibres.
