8 Questions
Which type of bone cell is responsible for forming the bone matrix and collagen fibers?
Osteoblasts
What is the function of osteoclasts in bone remodeling?
To carve out small tunnels and resorb bone
What is the purpose of the central canal in an osteon?
To house blood vessels
Which type of joint is characterized by the presence of collagen fibers?
Fibrous Joints
What is the purpose of parathyroid hormone (PTH) in calcium homeostasis?
To increase calcium levels in the blood
Which type of bone is formed during the fracture repair process?
Spongy bone
What is the function of the cribriform plate in the ethmoid bone?
To allow passage of olfactory nerves
What is the term for the remains of old osteons?
Interstial lamellae
Study Notes
Cell Types of Bone
- Osteoprogenitor cells: undifferentiated cells that can divide to replace themselves and become osteoblasts; found in the inner layer of periosteum and endosteum.
- Osteoblasts: form bone matrix and collagen fibers, but cannot divide.
- Osteocytes: mature cells that no longer produce bone matrix.
- Osteoclasts: huge cells formed from fused monocytes (WBC) that function in bone resorption at surfaces such as endosteum.
Bone Matrix
- Compact bone: looks solid and hard, making up the shaft of long bones and the external layer of all bones; resists stresses produced by weight and movement.
- Osteon parts:
- Central canal: a tube that blood vessels go through.
- Lamella: concentric rings of calcified bone matrix.
- Lacunae: osteocytes found in spaces.
- Canaliculi: canals that transport materials to and from osteocytes.
- Interstitial lamellae: remainders of old osteons.
Bone Remodeling
- Osteoclasts carve out small tunnels, and osteoblasts rebuild osteons.
- Fracture repair:
- Formation of fracture hematoma to stop bleeding (6-8 hours).
- Inflammation brings in phagocytic cells for cleanup duty.
- New capillaries grow into the damaged area.
- Formation of bony callus: osteoblasts secrete spongy bone that joins the two broken ends of bone (lasts 3-4 months).
- Bone remodeling: osteoclasts burrow out, and osteoblasts rebuild.
Calcium Homeostasis
- Parathyroid hormone (PTH) is secreted if calcium blood levels are too low.
- Calcitonin is secreted if calcium blood levels get too high.
Bones/Locations/Functions
- Cranial bones:
- Frontal bone: forms the forehead and anterior part of the cranial floor.
- Supraorbital foramen: passage for blood vessels for the eyebrow and eyelids.
- Ethmoid bone: forms the inferior, central portion of the anterior cranial floor.
- Cribriform plate: roof of the nasal cavity through which olfactory nerves pass to the brain.
Classification of Joints
- Functional classification:
- Synarthrosis: immovable joints.
- Amphiarthrosis: slightly movable joints.
- Diarthrosis: freely movable joints.
- Structural classification:
- Fibrous joints: collagen fibers.
- Sutures (no movement; synarthrosis): examples include sutures.
- Syndesmosis (some movement; amphiarthrosis): examples include ulna/radius and tib/fib.
- Gomphoses (some movement; amphiarthrosis): examples include teeth.
- Cartilaginous joints: made of cartilage, with little to no movement.
Learn about the different cell types involved in bone development, including osteoprogenitor cells, osteoblasts, osteocytes, and osteoclasts, as well as the structure of bone matrix.
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