Bio Chapter 6 Bone Tissue
The 6 Steps of Endochondral Ossification
1. Development of the Cartilage Model 2. Growth of the Cartilage Model 3. Development of the Primary Ossification Center 4. Development of the Medullary Cavity 5. Development of Secondary Ossification Center 6. Formation of Articular cartilage & Epiphyseal Plate
The 4 Steps of Intramembranous ossification
1. Development of the ossification Center 2. Calcification 3. Formation of Trabeculae 4. Development of Periosteum
7 Parts of Long Bones
1. Diaphysis 2. Epiphyses 3. Metaphyses 4. Articular Cartilage 5. Periosteum 6. Medullary Cavity 7. Endosteum
Medullary Cavity
A hollow, cylindrical, space within the diaphysis that contains yellow bone marrow and numerous blood vessels in adult long bones
Periosteum
A tough connective tissue sheath (and its blood supply) that surrounds the bone surface wherever its not covered by articular cartilage Has an inner osteogenic layer and an outer fibrous layer Helps bone grow in width, repair fractures, nourish the bone, and provide attachment points
Nutrient Foramen and Nutrient Artery
A whole in the bone that this passes through Divides once in bone and goes to the distal and proximal ends of the bone Supplies the inner diaphysis of compact bone and red bone marrow of spongy bone
Spongy Bone Tissue
Always located inside the bone Doe not contain osteons Consists of trabeculae Makes up interior of most short, flat, sesamoid, and irregular bones Makes up the core of the epiphyses in long bones
Perforating Fibers
Attaches the periosteum to the underlying bone Thick bundles of collagen fibers that extend from the periosteum into the bone ECM
Intramembranous ossification
Bone forms directly within mesenchyme Flat bones are formed this way
Endochondral Ossification
Bone forms within hyaline cartilage that develops from mesenchyme Most bones formed this way
Osteoblasts
Bone-building cells Synthesize and secrete collagen fibers and other ECM components Initiate calcification They become trapped in their secretions and the become osteocytes
Red Bone Marrow
Connective tissue found in certain bones It produces; RBC's, WBC's, and platelets It consists of; developing blood cells, fibroblasts, adipocytes, and macrophages All within a network of reticular fibers
Yellow Bone Marrow
Consists mainly of adipose cells They store triglycerides Which are a potential chemical energy reserve
Compact Bone Tissue
Contains few spaces, therefore is the strongest form of bone Found beneath the periosteum of all bones Makes up the bulk of the diaphyses Is composed of osteons and a central canal
Osteons
Cylindrical vascular tunnels The structural units of compact bone tissue Consists of concentric lamellae arranged around a central canal
Circumferential Lamellae
Developed during initial bone formation Arranged around the entire outer and inner circumference of the shaft of a long bone
Perichondrium
Develops around the cartilage model
Epiphyseal Artery
Enters the epiphyses, supplies the red bone marrow and bone tissues in those areas
Metaphyseal Artery
Enters the metaphysis, supplies red bone marrow and bone tissue of those areas
Appositional (Exogenous) Growth
Growth at the outer surface Happens in endochondral ossification ECM deposites on the surface of the growing bone
Interstitial (Endogenous) Growth
Growth from within Occurs in endochondral ossification Grows cartilage model in length
Osteoclasts
Huge cells derived from the fusion of as many as 50 monocytes (WBC) Concentrated in the endosteum The side facing the bones surface has its plasma membrane deeply folded into a ruffled border, which has powerful lysosomal enzymes and acids which digest the protein and minerals of the ECM
Calcification
Hydroxyapatite combines with other mineral salts in bone to crystallize in ECM and hardens tissue
Trabeculae
Lamellae arranged in an irregular patter of thin columns The small spaces between them hold red and yellow bone marrow Contains blood vessels to nourish the osteocytes
Osteocytes
Mature bone cells The main bone cell Maintain daily metabolism
Calcitrol
PTH stimulates the formation of this The active form of vitamin D Which increases the absorption of dietary calcium in the GI tract Increasing the blood levels of calcium
Ossification
Process of bone formation Occurs in 4 situations: 1. Initial formation in an embryo/fetus 2. Growth during infancy until adult size is reached 3. Remodling throughout life 4. Repair of fractures throughout life
Canaliculi
Radiate in all directions from the lacunae Filled with ECF Inside are slender processes of osteocytes Connect lacunae with each other and with the central canal Form interconnected canals through out the bone Help to transport nutrients and watses to and from osteocytes
Parathyroid Hormone (PTH)
Regulates calcium exchange Will increase blood levels of calcium by telling the osteoclasts to increase bone resorption and for the kidneys to retain calcium
Concentric Lamellae
Resembles growth rings of a tree circular plates of mineralized ECM of increasing diameter Surrounds a small network of blood vessels and nerves located in the central canal
Rickets (children)/Osteomalacia (adults)
Result from inadequate calcification of the extracellular bone matrix, usually caused by a vitamin D deficiency bones become "soft" or rubbery and are easily deformed
Periosteal Arteries
Small arteries accompanied by nerves that enter the diaphysis through perforating canals Supply the periosteum an outer part of compact bone
Lacunae
Small spaces between concentric lamellae Contains osteocytes
Bony (hard) Callus
The Fibrocartilaginous (soft) Callus is converted to spongy bone Lasts about 3-4 months
Bone Deposition
The addition of minerals and collagen fibers by osteoblasts
Resorption
The breakdown of the ECM of bone Done by the osteoclasts
Epiphysis
The proximal and distal ends of long bones
Metaphysis
The region between the diaphysis and the epiphysis
Diaphysis
The shaft/body of a long bone Long, cylindrical, main portion
Ossification Center
The site of mesenchyme cells clustering to begin to form bone They differentiate into osteoprogenitor cells
Articular Cartilage (long bones)
Thin layer of hyaline cartilage covering the epiphysis where the bone forms an articulation with another bone Reduces friction and absorbs shock in moveable joints Lacks perichondrium and blood vessels (therefore repair is limited)
Calcitonin (CT)
Thyroid glands secrete this This decreases blood levels of calcium by inhibiting activity of osteoclasts, speeds blood calcium uptake by bones, and accelerates calcium deposition into bones
Osteoprogenitor Cells
Unspecialized bone stem cells Derived from mesenchyme Only bone cell that undergoes cell division With the resulting cell being osteoblasts Found along inner portion of periosteum in, endosteum, and the canals within bone that contain blood vessels
Epiphyseal Line
What is formed when the epiphyseal plate is completely replaced by bone in a fully grown bone Located in the metaphysis region of long bones
Epiphyseal (growth) Plate
a layer of hyaline cartilage that allows the diaphysis of the bone to grow in length located in the metaphysis area of the bone in growing bones
Fibrocartilaginous (soft) Callus
a mass of repair tissue consisting of collagen fibers and cartilage that bridges the broken ends of the bone Takes about 3 weeks
Stress Facture
a series of microscopic fissures in bone that forms without any evidence of injury to other tissues
Fracture Hematoma
blood clot that forms at the fracture site Forms 6-8 hours after injury
Osteoporesis
bone resorption outpaces bone deposition. In large part this is due to depletion of calcium from the body—more calcium is lost in urine, feces, and sweat than is absorbed from the diet.
Cartilage Model
the hyaline cartilage that takes the shape of the future bone during endochondral ossification
Bone Resorption
removal of minerals and collagen fibers from bone by osteoclasts
Hydroxyapatite
the combination of calcium phosphate and calcium hydroxide Forms crystals of this
Endosteum
thin membrane that lines the medullary cavity, contains a single layer of bone-forming cells and a small amount of connective tissue