Bone Structure II

Question 1

Compact Bone - 5 points (contains few spaces)

Answer 1

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

Question 2

How is Compact Bone arranged - 4 points

Answer 2

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

Question 3

Concentric Lamellae

Answer 3

rings of hard calcified intercellular substance circling the central canals

Question 4

Lacunae

Answer 4

small spaces between the lamellae - contains osteocytes

Question 5

Canaliculi - 4 points

Answer 5

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

Question 6

Cancellous Bone - 6 points

Answer 6

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

Question 7

Children bones are …

Answer 7

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

Question 8

human embryo skeleton made of …

Answer 8

fibrous membranes and hyaline cartilage shaped like bones - a medium for ossification to occur

Question 9

cartilage is formed by …

Answer 9

chondroblasts

Question 10

2 types of bone formation

Answer 10

Intramembranous Ossification and Endochondral Ossification (both replace pre-existing connective tissue with bone

Question 11

Describe Intramembranous Ossification - 2 points

Answer 11

bone forms directly on/within fibrous membranes (along a template of membrane), primarily in compact flat bones in skull - don’t have Haversion Systems

Question 12

Explain Intramembranous Ossification - 3 points

Answer 12

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

Question 13

Fontanels

Answer 13

6 soft spots in the skull of a baby - 1 frontal, 2 sphenoidal, 2 mastoidal, 1 occipital

Question 14

Describe Endochondral Ossification - 2 points

Answer 14

Replacement of cartilage by bone, mineral salts calcify along the cartilage within the developing foetus

Question 15

Explain Endochrondral Ossification - 5 points

Answer 15

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

Question 16

Both types of bone formation rely on …

Answer 16

thyroid hormone, calcitonin - regulates metabolism of calcium

Question 17

Remodelling - 3 points

Answer 17

where the bone replaces itself throughout adult life, takes place at different rates in various body regions, allows injured/worn out bone to be removed &replaced by new new tissue