AG

Lec 20

Musculoskeletal SYstem

  1. Types of skeleton

    1. Hydrostatic- based on liquid

      1. Found in soft bodied invertebrates

      2. Circular and longitudinal muscles contract against extracellular liquid (incompressible)




  1. Exoskeleton- complete outside of the body, arthropods

    1. Hardened outer surface where muscles attach- made of chitin (protein and carbohydrate) 


trapdoor spider

weevil 

trap jaw ant, generated escape jump by closing its jaws on the ground

  1. Muscles caused joint segments of exoskeleton to move

  2. Drawback?... cannot grow. Have to shed.

    1. Increased predation risk

    2. Absence of hard support to pull against

  1. Endoskeleton- inside of body, bony often derived from cartilage

    1. Can grow with organism

    2. Develops from cartilaginous template (endochondral bone, hardened or ossified)

    3. Many components needed for construction

      1. Osteoblasts- cells that lay down new matrix (blasting new bone)

      2. Matrix- gelatinous substance that contains calcium phosphate (eventually hardened part of bone)

      3. Collagen fibers

      4. Osteoclasts- cells that dissolve bone

Bones are dynamic organs!

  1. Healing from a bone break- balance between osteoblasts and osteoclasts



Two general categories of skeleton

  1. Axial- skull, vertebral column, sternum, ribs

  2. Appendicular- pectoral girdle, pelvic girdle, arms, legs, hands, feet


Formation of cartilaginous bone

  1. We start off as complete cartilage

  2. Construction of endochondral bone- we get blood vessels (inside long bones is where we make RBC)

How do maximize force or speed?

All the muscles integrate with the skeletons so we can either get force or speed (where fulcrum and load are)


Galapagos islands- darwin's finches

What causes the rapid diversification in beak sizes in Darwin’s finches?

  • This has to do with the skeleton

  1. Bmp- Bone Morphogenetic Protein

    1. A cytokine (small protein that is important in cell signaling)

    2. Some cells have bmp receptors on their surface that induce some change in the cell

    3. Bmp4 binding may stimulate the production of certain proteins that cause bone proliferation

    4. Scientists tested embryos of darwin's finches and saw variation in bmp4 levels positively correlated with beak size