development and growt of bone

Question 1

what are the functions of bone

Answer 1

support body shape

system of levers for muscle action

protection of internal organs eg ribs and pelvis

site of blood cell formation - marrow

mineral storage pool - ca

Question 2

what are the machanical properties of bone

Answer 2

cable like flexibility and resistance to tension - because framework is collage and other bone proteins (this is the osteoid)

pillar like stiffness and resistance to compression - because of impregnation of collagen with cyrstalline mineral hydroxyapatute (complex ca hydroxyphosphate)

Question 3

what are the 2 types of bone tissue

Answer 3

woven (immature bone) - formed in healing, early stages of repair

lamellar (mature bone)

Question 4

describe how you can see the structure of lamellar bone and what it is

Answer 4

use polarising microscopy - show up when tings are aligned

sow the concentric lamellae around the central canals

Question 5

describe the structure of woven bone

Answer 5

random arrangement - needs to be remodelled to form lamellar bone

Question 6

what is the arrangement of bones

Answer 6

have head at either side of the bone

articular cartilage on both heads

shaft (diaphysis) is between the heads

medullary cavity in diaphysis - marrow here and makes bones lighter

nutrient arteries leave and enter through nutrient foramen/canal - veins run with them

outer hard layer of compact bone - cortical bone

inner layer of interlacing spikes of lamella bone tis is cancellous bone (spongy/trabecular bone) - like a meshwork

Question 7

describe the arrangement of lamellar bone

Answer 7

spongy bone is strong because te interlocking tubercles old it together and distribute force - however, not as resistant to compression as compact bone

compact bones made of ostions - a column of bone with bv and nerves running through middle (central canal) - around here have concentric cells

between the circles have interstitial lamellae - still lamellar bone

trabecular are made of lamellar bone even though irregularly arranged

osteocytes have protusions connecting to other cells via gap junctions so cells sare the nutrients from the central canal

ave ca deposits

Question 8

what is periosteum

Answer 8

it is te outer surface of bone - a fibrous and cellular layer

involved in bone growth and repair - osteoblasts develop from cells in the periosteum

vascular

sensory nerve supply - what causes pain from fractures

Question 9

describe the generation of osteocytes

Answer 9

osteogenic cell develops into an osteoblast which forms bone matrix and turns into an osteocyte whic maintains bone tissue

Question 10

describe osteoclasts

Answer 10

function is bone resorption, the breakdown of the bone matrix

multinuclear

ruffled border

similar lineage to macrophages

Question 11

how long are bones growing

Answer 11

skeleton forms from 6 weeks in foetus bup to 25 yrs of age

Question 12

what are the 2 types of ossification

Answer 12

intramembranous

endochondrial - more common

Question 13

describe intramembranous bone development

Answer 13

in existing vascular connective tisssue - signals to develop into bone

calcified bone matrix proteins (ostein) is deposited around collagen

mineralises to form woven bone

vascularised

remodels to form lamellar bone

used for the flat bone of the skull and mandible

Question 14

describe endocondrial bone development

Answer 14

within existing fetal cartilage models - short small version of early cartilage

cartilage calcifies and condrocytes die

periosteal osteoclasts cut channels for sprouting vessels

osteoblasts enter with vessels to build bone around them

Question 15

what is the thing you need to overcome for bone growth and how is it overcome

Answer 15

long bones support forces whilee growing

if tried to grow at end these forces would disrupt te terminal appositional growth because of the articulates

solution;

shaft ossifies first then the epiphyses

growth continues by ossification of growing cartilage plate between them

growt cessation occurs when cartilage growt ceases and plate overrun by ossification

Question 16

describe endochondrial ossification

Answer 16

have calcified matrix which attracts bv

osteoclasts remodel bone

there is a secondary ossification centre in the head

cells are arranged in a column, proliferate and push the head forward

teh epiphysial plate remains cartilage until late

epiphysial surface not affected - bone can still support weight

Question 17

describe te age related change in appearance of normal bones

Answer 17

in wrist epiphyses ossify in 2nd year

the epiphyseal plates remain cartilaginous until after puberty, growth occurs here until hormones tell it to ossify

Question 18

what is te effect of a child breaking their hand at an epiphysial plate

Answer 18

affect growth

have to scaffold it in place to ensure normal growth

Question 19

give examples of how bone is adaptable

Answer 19

can grow witout comprimising func

increase/decrease bulk and density depending on its pattern of use

can alter internal and external shape in response to pattern of use = remodelling

repair when fractured

Question 20

how can bone remodel

Answer 20

bone has a large blood supply - cells near o2 and nutrient source and waste removal

osteocytes maintain matric but can activate osteoblasts for new bone building

osteoclasts giant cells specialised for destruction of bone matrix

Question 21

describe te growth of bone diameter

Answer 21

it is called apposition

cells in the periosteum activated to become osteoblasts and produce new bone

osteoblasts and osteoclasts create ridges and grooves on the bone surface

bv align in the grooves

ridges fuse around the vessels

osteoblasts build new osteons round vessels

osteoclasts remove bone from the endosteal surface

Question 22

describe fracture healing

Answer 22

fractures damage bv = haemotoma - this is the first part of healing

osteoprogenitor cells and inactive osteoblasts from periosteum and endosteum differentiate into aactive osteoblasts and migrate to fracture

the migrating osteoblasts form a provisional type of bone and cartilage called the external callus - this bridges the end of bones. internal callus forms between bone ends

connective tissue and bv invade clotting region

chondrocytes produce cartilage that is replaced by bone

forms woven bone

this is remodelled to form lamellar bone (first cancellous then cortical) - reactive cartilage undergoes endochondrial ossification

Question 23

what happens if blood ca levels are high

Answer 23

calcitonin released by parafollicular thyroid cells - osteoclasts inibited - ca uptake into bone promoted

Question 24

what happens if the blood ca levels are low

Answer 24

pth released by chief cells of parathyroid gland - osteoclast bone resorption promoted - increase ca resorption in kidney - ca released into the blood

Question 25

what effects bone remodelling *

Answer 25

physical stresses

metabolic and hormonal factors