MSCI M131 Lecture 3Outline of Current Lecture I. Bonea. Anatomyb. Maintenancec. Formationd. Resorption balanceCurrent LectureI. Bonea. Bone anatomy: 3 types of active cellsi. Osteoblasts: lay down collagenous fiber, which will be mineralized to build new boneii. Osteoclasts: erode bone by releasing acid to etch away the outer layeriii. Osteocytes: former osteoblasts, now buried in bone matrix. Provide sensory details and signal for osteoclast and osteoblast activity iv. Why have both osteoblasts and osteoclasts?1. Old bone – potentially brittle2. New bone – release of calcium into blood3. Reabsorption – old material to form new bone4. Fractures and microfracture damage – erode bone to create betterfix b. Bone maintenance:i. Bone turnover or remodeling1. Mechanism: osteoclast and osteoblast balance2. Purpose: to fix microfractures, prevent loss of structure; bone continues to reshape itself in response to stressors3. Is it true that a bone is stronger after a fracture?a. After one starts exercising, there is a bias shift for osteoblasts to lay down more bone, creating more densityb. After stopping exercise, the osteoblasts back off and the bias may reverse, since heavier bones require more energyto sustainc. Yes and no– there are more deposits at the fracture site, but not necessarily on the whole bone – the deposits also cause a coupling of weak points to the newly created These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.strong point, which could contribute to more microfractures. ii. Bone formation1. Mechanism: transition from cartilage to bone at the epiphyseal plates (osteoblasts lay down substrate, which is then calcified)a. As one ages, the growth plates are less active, until the growth plates turn into spongy bone as wellb. How do forensic experts determine the age of a skeleton?i. They look at the distance between the epiphyseal plate and the epiphyseal line in a variety of bones –each bone reaches maturity at different times (humerus 9-11 years, clavicle 25-30 years) once the clavicle has matured, they look at bone degradationto determine ageiii. Bone resorption and calcium/ phosphorous balance1. Bones store calcium and phosphorous, used to mineralize osteoblast substrate2. But free calcium is needed in the blood for muscle contraction andneurotransmitters (so osteoclasts needed to destroy