11. Skeletal System Flashcards
Functions of Skeletal System
- Supports the body
- Facilitates movement
- Protection of internal organs
- Haematopoiesis
- Stores and releases minerals and fat
Organic Nature of Skeletal System
• Osteogenic cells, osteoblasts, osteocytes, osteoclasts
- Osteoid—organic bone matrix secreted by osteoblasts
- Ground substance
- Collagen fibers: Provides tensile strength and flexibility
Inorganic Nature of Skeletal System
- Mineral salts
* 65% of bone by mass
* Mainly calcium phosphate crystals
* Responsible for hardness and resistance to compression
Histology of Bone
Osteoprogenitor Cell -> Osteoblast -> Osteocyte | Osteoclast
Osteoprogenitor Cell
Develops into Osteoblast
Osteoblast
-Develops into osteoblasts
-Forms bone extracellular matrix
-LOCATION: Growing portions of bone, including
periosteum and endosteum
Osteocyte
- Maintains bone tissue
- Maintain mineral concentration of matrix
- LOCATION: Entrapped in matrix
Osteoclast
-Functions in resorption, the breakdown of bone
extracellular matrix
-Bone Resorption
-LOCATIONS: Bone surfacesand at sites of old,
injured, or unneeded bone
Osteogenic Cells
- Develop into osteoblasts
- LOCATION: Depp layers of the periosteum and bone marrow
How many bones do we have?
206
5 categories of bones
- Long (greater length than width
- Short (cube shaped)
- Flat (thin layers of parallel plates)
- Irregular (complex shapes)
- Sesamoid (shaped like a sesame seeds)
Ossification (osteogenesis)
Formation of bone
Bones form in 4 situations
- During embryological and fetal development
- Bone growth prior to adulthood
- When bones remodel
- When fractures heal
Endochondral Ossification
Replaces cartilage with bone in the developing embryo and fetus
3 Different Phases of Bone Repair
- Reactive phase (early inflammation)
- Reparative phase (includes formation of a fibrocartilaginous callus first and the bony callus second)
- Bone remodeling phase (last step as the bony callus is remodeled)
Calcitonin
Released by thyroid gland to make osteoblasts deposit Ca into bone. Osteoclasts are inhibited. Decrease Ca from intestines; increase excretion to filtration
Parathyroid Hormone (PTH)
Secreted by parathyroid glands when Ca is low. Stimulates osteoclasts tk release Ca from bone. Increase Ca uptake from institutes and increase reabsorption from filtrate
Chondrocytes
Cells in cartilage. Located in spaces called lacunae
Matrix if cartilage contains:
Ground substance composed of proteoglycans which contribute to the flexible, resilient consistency of cartilage
Articulate cartilage
- Hyaline cartilage lining many joint surfaces
- Absorbs compression and prevents bone damage
Articular discs
- Wedges fibrocartilage in freely movable joints
- improves the fit between irregular bone services
- Improves joint stability
Synovial Joints
Two bones are separated by a joint cavity which is enclosed by a fibrous capsule: Freely movable, articulating surfaces of bones lined by hyaline cartilage
