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Bone Tissue
Anatomy of bone tissue
| Question | Answer |
|---|---|
| Hyaline cartilage | - most abundant cartliage - rich in collagen fibers - support through flexibility and resisting compression - articular cartliage at ends of adjoining bones of movable joints - attachments of ribs to sternum - nose |
| Elastic cartliage | - many elastic fibers as well as collagen fibers - able to tolerate repeated bending - present in ear pinna and epiglottis |
| Fibrocartilage | - resists strong compression and strong tension - located in pubic symphysis, some ligaments - articular discs of some joints (ex. knees) - annulus fibrosis portion of discs between vertebrae |
| Perichondrium | - membrane of fibrous CT that surrounds external surface of cartilage |
| Appositional growth | - chondroblasts in surrounding perichondrium produce new cartilage |
| Interstitial growth | - chondrocytes within cartilage divide and secrete new matrix |
| Osteocalcin | - stimulates pancreas to produce more insulin and fat cells to become more insulin sensitive |
| Bone ECM composition | 35% organic components 65% inorganic mineral salts |
| Osteogenic cells | stem cells that differentiate into osteoblasts |
| Osteoblasts | - actively produce and secrete bone matrix - bone matrix = osteoid |
| Osteocytes | - keep bone matrix healthy |
| Osteoclasts | - resorb bone - derived from white blood cells - secrete HCl and lysosomal enzymes - multinucleated |
| Long bones | - longer than wide - a shaft plus two ends - common in extremities of body |
| Short bones | - roughly cube-shaped - in wrist and ankle - special type: sesamoid bones (in kneecap) |
| Flat bones | - thin and flattened, usually curved - ribs, sternum, scapula, and some cranial bones |
| Irregular bones | - bones of various shapes that don't fit into other categories - vertebrae and hip bones |
| Compact bone | - dense outer layer of bone |
| Spongy bone | - internal 3D network of bones with small needle-like pieces called trabeculae - open spaces between trabeculae are filled with red or yellow bone marrow |
| Diaphysis | - "shaft" - long axis of bone |
| Epiphysis | - ends of a bone with joint surfaces typically covered with a thin layer of articular cartilage (hyaline) |
| Epiphyseal line | - runs between diaphysis and epiphysis in adults - remnant of epiphyseal plate |
| Medullary cavity | - interior of all bones consists largely of spongy bone with marrow in between trabeculae - the very center of the diaphysis has no spongy bone and is filled with yellow bone marrow |
| Periosteum | - CT membrane which covers external surface of the bone except for ends of epiphyses - provides insertion points for tendons and ligaments |
| 2 layers of periosteum | - Superficial outer layer: dense irregular CT that resists tension placed on bone - Deep inner layer: abuts compact outer surface of compact bone --> osteogenic layer |
| Perforating fibers (Sharpey's fibers) | - secure periosteum to the underlying bone with thick bundles of collagen that run from periosteum into bone matrix |
| Endosteum | - thin CT layer which lines internal bone surfaces - includes trabeculae of spongy bone and inner surface of central canals of osteons - osteogenic; contains both osteoblasts and osteoclasts |
| Structure of short, irregular, flat bones | - no diaphysis - hard dense compact outer layer of bone - diploe: internal spongy bone with trabeculae flat bones - no deep marrow cavity is present |
| Bone design and stress | - trabeculae of spongy bones align alongside lines of stress in an organized pattern to provide structural support - anatomy of a bone reflects stresses |
| Bone markings | - superficial surfaces of bones reflect stresses on them - 3 broad categories: projections for muscle and ligament attachment, surfaces that form joints, and depressions & openings |
| Osteons (Haverson systems) | - long cylindrical structures oriented parallel to long axis of bone - function in support - group of concentric tubes |
| Osteon structure | - group of concentric tubes - each concentric tube is a lamella with layer of bone matrix in which collagen fibers & mineral crystals align + run in one direction - fibers and crystals of adjacent lamella run in opposite direction |
| Central canal/Haversian system | - canal which runs through each osteon - lined with osteogenic endosteum layer - Perforating canals lie perpendicular to central canals; connect blood and nerve supply of periosteum to central canals and central marrow cavity |
| Canaliculi | - connect neighboring lacunae to one another and to capillaries for nutrient supply - within the canaliculi, extensions of neighboring osteocytes touch and form gap junctions for nutrient exchange |
| Lamellae | - Interstitial lamellae: groups of incomplete lamellae which lie between osteons; remains of old osteons cut through by bone remodeling - Circumferential lamelllae: extends around entire circumference of diaphysis |
| Microscopic structure of spongy bone | - trabeculae are too small to contain osteons or its own blood vessels - osteocytes receive nutrients from capillaries in endosteum surrounding trabecular via connections through the canaliculi |
| Membrane bones | - form directly from mesenchym without first being modeled in cartilage through intramembranous ossification |
| Endochondrial bones | - bones are modeled in hyaline cartilage - all bones except some bones of the skull and clavicles |
| Epiphyseal growth areas | - cartilage is organized for quick, efficient growth - cartilage cells form tall stacks - pushes epiphysis away from diaphysis - lengthens entire long bone |
| Epiphyseal plate | - Resting zone - Proliferation zone - Hypertrophic zone - Ossification zone |
| Hormonal regulation of bone growth | - growth hormone, produced by pituitary gland; stimulates epiphyseal plates - thyroid hormone: ensures skeleton retains proper proportions - sex hormones: promote bone growth, later induce closure of epiphyseal plates |
| Bone remodeling | - occurs at periosteal and endosteal surfaces - bone deposition: accomplished by osteoblasts - bone resorption: accomplished by osteoclasts - maintains constant levels of calcium and phosphate in body fluids |
| Bone fractures | - simple fracture: bone fracture without penetrating skin - compound fracture: bone fracture that breaks the skin - treatment by reduction: closed = manually set with hands, open = surgically set with pins/wires |
| Phases of bone healing | - Hematoma formation - Fibrocartilage callus formation - Bony callus formation - Bone remodeling |
| Osteoporosis | - characterized by low bone mass - bone resorption outpaces bone deposition - compact bone becomes thinner and less dense and spongy bone has fewer trabeculae |
Created by:
peckman12
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