Chapter 37

Seite 1

Vertebrate bones develop:

1. precursor cells differentiate into osteoblasts that begin producing bone - membranous bone

2. formed as cartilage first

- preursor cells being chondroblasts and grow into cartilage in the embryo

-same as articular cartilage

-cartilage grows by expansion- letting fetus grow

-blood vessels enter the cartilage- making it turn into hard bone

Cartilage template of a bone replacement

1. compact bone

-bone shaft

-dense mineralized bone tissue containg bone cells called osteocytes, and blood vessels

2. spongy bone

-small paltes and rods called trabeculae

-found in ends of limb bones in vertebrate

-Bone marrow found between trabeculae has many cell populations

Bone marrow

-grow in length and width

-growth in length happens at growth plate

-Growth plate

-region of cartilage between a middle region (diaphysis) and the end (epiphysis)

-growth plate adds new cartilage toward diaphysis

-growth plate fuses after maturity

Limb bones

-grow in diameter when osteoblasts put new bone on external surface

-at same time of addition, bone is removed from inner surface to expand the cavity

-bone removal slower than bone growth

-bone removed from cavity by osteoclasts- put out an enzyme to dissolve calcium mineral and collagen, and is later recycled

-advantage of endoskeleton: bone can be repaired by osteoblasts and osteoclasts

-older adults bones are weaker bc osteoclasts remove more bone than osteoblasts produce

Joint

-shapes on bones that meet determine range of motion in joint

-Hinge joints: axis in one rotation

-Ball and socket: rotation in three rotations

-finger bones intermediate bc odd range of motion

-broader range of motion= less stable and most dislocated

-hinge joints have 2 antagonist muscles

-ball and socket have 3 sets of muscles

Muscle Forces

-muscles transmit forces that cause joint rotation

-Muscles attached further away from joint axis have slower but stronger movements

-Muscles attached closer from join axis have faster but weaker movements

Torque

-Torque - strength of rotational movement

- determined by muscles force and lever distance from the axis of joint rotation

-F times r

-Stronger rotational movements when have a larger force or larger lever distance between joint and muscle attachment site, more range of motion

-Weaker rotational movements when have a smaller force or shorter lever distance between joint and muscle attachment site, and less range of motion

Muscles on Skeleton

-Animals like horses have a long leg, and their knee is closer to the muscle, but their ankle , the output force, is farther away, so they produce faster movements with less force

-and vice versa , a hamster has short limbs and the muscle is farther from the attachment site and a shorter distance from the output force, the foot.

-aka hamsters have more weight in their foot and horses have more weight in whole leg so the foot of a hamster has more force than the foot of a horse, but the horse can move faster with less force