Flashcards in Bone Structure II Deck (17):
Compact Bone - 5 points (contains few spaces)
forms external layer of all bones, lies over internal spongy bone tissue, thicker in diaphysis than the epiphysis of long bones, provides protection and support, resists stresses produced by weight/movement
How is Compact Bone arranged - 4 points
in concentric rings called Osteons/Haversion Systems, within these there are Central (Haversion) Canals running Longitudinally through the bone - contain blood vessels and nerves, nerves/blood/lymphatic vessels from periosteum penetrate the compact bone through transverse Perforating (Volkmann's) Canals - to connect with blood vessels and nerves of medullary cavity and the central Haversion canals
rings of hard calcified intercellular substance circling the central canals
small spaces between the lamellae - contains osteocytes
Canaliculi - 4 points
minute canals which radiate from lacunae - contain the slender processes of the osteocytes, connect with other lacunae and eventually the central canals - creating an intricate network - provide routes for nutrients to reach osteocytes
Cancellous Bone - 6 points
lies medial to compact bone, doesn't contain osteons, an irregular latticework of thin plates of bone = trabeculae, some bones have spaces between trabeculae which stores red bone marrow, lacunae containing osteocytes lie within trabecular, blood vessels from periosteum penetrate through cancellous bone and nourish the osteocytes directly
Children bones are ...
Pliable, their final shape/hardness takes years to develop, bone forms due to ossification from 6th/7th week of embryonic life and continues through adult life
human embryo skeleton made of ...
fibrous membranes and hyaline cartilage shaped like bones - a medium for ossification to occur
cartilage is formed by ...
2 types of bone formation
Intramembranous Ossification and Endochondral Ossification (both replace pre-existing connective tissue with bone
Describe Intramembranous Ossification - 2 points
bone forms directly on/within fibrous membranes (along a template of membrane), primarily in compact flat bones in skull - don't have Haversion Systems
Explain Intramembranous Ossification - 3 points
Skull & Mandible of foetus is 1st laid down as membrane, osteoblasts attach ossifiying from the centre of the bone outwards, edges of the skull bones don't completely ossify to allow for moulding of the head during birth - 6 soft spots (fontanels) formed
6 soft spots in the skull of a baby - 1 frontal, 2 sphenoidal, 2 mastoidal, 1 occipital
Describe Endochondral Ossification - 2 points
Replacement of cartilage by bone, mineral salts calcify along the cartilage within the developing foetus
Explain Endochrondral Ossification - 5 points
osteoblasts carried in blood attach themselves to cartilage, primary centre of ossification = diaphysis - forms spongy bone tissue along cartilage, secondary centres = epiphyses, separated from diaphysis by layer of uncalcified cartilage (epipyseal plate) - all growth occurs here, compact bone tissue covering bones surface = produced by osteoblasts in inner layer of periosteum - producing growth in diameter
Both types of bone formation rely on ...
thyroid hormone, calcitonin - regulates metabolism of calcium