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Skeletal System (Bones & Bone types (Flat bones
Clavicle
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Skeletal System
Bones & Bone types
Flat bones
- Clavicle
- Mandible
- Frontal
- Parietal
- Nasal
- Maxilla
- Temporal
- Zygomatic
- Mandible
- Scapula
- Ribs
Short bones
- Carpals
- Patella (kneecap)
- Tarsals
- Talus
- Calcanous
Irregular bones
- Cervical
- Lumbar
- Thoracic
- Coccyx
- Sacrum
Long bones(embedded within a tendon or muscle)
Long bones
- Humerus
- Radius
- Ulna
- Metacarpals
- Phalanges
- Femur
- Fibula
- Tibia
- Metatarsals
Microscopic Anatomy of compact bone tissue
Five major cell types populate bone tissue: Osteoprogenitor cells, osteoblasts, osteocytes, bone lining cells, and osteoclasts
Bone-lining cells
- Flat cells found on bone surfaces where bone remodeling is not going on
- Like osteocytes, they are thought to help maintain the matrix
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Osteoblasts
- Bone-forming cells that secrete bone matrix, actively miotic
- Bone matrix they secrete includes collagen and calcium-binding proteins that make up unmineralized bone (osteoid), Play a role in matrix calcification
- Become osteocytes when completely surrounded by the matrix being secreted
Osteoclasts
- giant multi nucleate cells located at sites of bone resorption
- Lie in a shallow depression when actively breaking down bone
Osteoprogenitor cells (osteogenic cells)
- Mitotically active stem cells found in the membranous periosteum and endosteum, In growing bones, they are squamous cells.
- when stimulated, differentiated into osteoblasts
Anatomy of the long bone
Spongy bone
- Internal to the compact bone, also called trabecular bone
- A honeycomb of small needle-like or flat pieces called trabeculae
- In living bones, the open spaces are filled with red or yellow bone marrow
Typical structure of long bones
- Generally, all have a shaft, bone ends, and membranes
Epiphyses (bone ends)
- An outer shell of compact bone forms the epiphysis exterior and the interior contains spongy bone
- A thin layer of hyaline cartilage covers the joint surface of each epiphysis
- Between the diaphysis and epiphysis is an epiphyseal line, a remnant of the epiphyseal plate (growth plate)
- The epiphyseal plate is a disc of hyaline cartilage that grows during childhood to lengthen the bone
Membranes
- A glistening white, double-layered membrane called the periosteum covers the external surface of the entire bone except the joint surfaces
- A delicate connective tissue membrane called the endosteum covers internal bone surfaces
Diaphysis (shaft)
- Forms the long axis of the bone, constructed of a relatively thick collar of compact bone that surrounds a central medullary cavity
- Medullary cavity contains no bone tissue, but yellow marrow (fat) in adults
- Between the marrow and compact bone, there is a thin layer of spongy bone
Blood vessels and nerves
- Bones are well vascularized, the main vessels serving the diaphysis are a nutrient artery and a nutrient vein, both run through the nutrient foramen
Compact bone
- External layer, smooth and solid, found in the periosteum
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Joint classifications
Cartilaginous joints
- both rigid and slightly movable
Two types of cartilaginous joints: Symphyses and synchondroses
Synchondrosis
- A plate of hyaline cartilage that unites bones, virtually immovable
Symphyses
- Where fibrocartilage unites the bones
- Acts as a shock absorber and permits a limited amount of movement
- designed for strength and flexibility
Synovial joints
- freely movable
- Adjoining bones covered with articular cartilage, separated by a joint cavity, and enclosed within an articular capsule lined with synovial membrane
Fibrous joints
- immovable
- There are three types of fibrous joints: sutures, gomphoses, syndesmoses
Sutures
- Seams that occur only between the bones of the skull
- filled with short connective tissue fibers that are continuous with the periosteum
- Knit bones together, allow the skull to expand as the brain grows
Syndesmoses
- Bones are connected exclusively by ligaments
- The amount of movement allowed depends on the length of the connecting fibers
Gomphoses
- Peg in socket fibrous joint
Synarthroses - immovable joints
Amphiarthroses - slightly movable joints
Diarthroses - freely movable joints
Bone remodeling
Bone deposition
- Osteoblasts deposit new matrix
- Begins as an osteoid seam, an unmineralized band of gauzy looking bone matrix
- Between the osteoid seam and the older mineralized bone, there is an abrupt transition called the calcification front
-Calcium salts deposited throughout the osteoid, creating calcified bone matrix
Bone resorption (breaking down)
- Osteoclasts accomplish resorption
- They move along bone surfaces digging grooves as they break down the bone matrix
- osteoclasts secrete acid that dissolve the bone matrix
- Osteoclasts die after resorption is complete (apoptosis)
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Bone fracture repair
- Bones are very susceptible to fractures/breaks
- Hematoma forms, the hemorrhaged blood clots
- Fibrocartilaginous callus forms
- Bony callus forms
- Bone remodeling occurs