1. Prayer
Attendance
Homework

2. Musculoskeletal System
Ms. Doshi

3. Bone Structure Compact Bone Is composed of dense, hardened bone matrix
Contains both organic and inorganic material
Organic material:
proteins (collagen fibers and glycoproteins)
Inorganic material:
Calcium, phosphate, and hydroxide (join to form hydroxyapatite crystals), as well as sodium, potassium, and magnesium ions.
Hydroxyapatite crystals and collagen fibres give bone its strength.

4. Bone Structure: Microscopic
The bony matrix is deposited (증착 Verb: 두다 , 퇴적시키다 , 보증금을 주다 , 낳다) in osteons (Haversian systems)
Each osteon has a Haversian canal that has lamellae (circles of bony matrix) surrounding the canal.
Inside the Haversian canals, there are blood vessels, nerve fibers, and lymph.
The lacuna is a space inside the bone matrix. In these spaces (lacunae), are mature bone cells called osteocytes.
Osteocytes help with bone maintenance.
Canaliculi are small canals radiating (방사) from each lacuna.
The canaliculi interconnect with each other and with Haversian canals.
The canaliculi allow for exchange of nutrients and wastes.

5. Bone Cells Osteoblasts
make and secrete the organic materials of the bone matrix.
once they are surrounded by bone matrix, they become mature bone cells, osteocytes.
Osteoclasts
large, multinucleated cells that help in bone resorption.
several = many

6. Questions Part 2-1

7. Bone Formation (Ossification)
Two processes: endochondral ossification or intramembranous ossification.
Endochondral ossification:
Existing cartilage is replaced by bone.
Example: long bone
Intramembranous ossification:
Mesenchymal (embryonic) connective tissue is transformed into, and replaced by, bone.
Example: skull bones (except the mandible)

8. Bone Remodeling
Bone matrix is dynamic (it continuously and simultaneously degrades and reforms)
2 processes for bone remodeling: bone reformation and bone resorption
Bone reformation
Inorganic ions (calcium and phosphate) are absorbed from the blood for use in bone formation
Bone resorption
the inorganic ions are released into the blood
Vitamin D, and hormones, such as parathyroid hormone and calcitonin, help with regulating bone remodeling.
Bone use and stress during exercise affect bone remodeling.

9. Joints
Joints are connective tissue structures that join bones together.
Immovable joints
Bones that do not move relative to each other (서로에 대해 움직이지 않는다) are held in place by immovable joints
Example: skull bones
Movable joints
Bones that move relative to each other (서로에 대해 이도) are held together by movable joints
Movable joints are supported and strengthened by ligaments.

10. Movable Joint Synovial capsule (articular capsule) Synovial fluid
surrounds the synovial (joint) cavity
Synovial fluid
Helps with movement
Lubricates the joint
Articular cartilage
Reduces friction (마찰을 감소) during movement.

11. Questions Part 2-2