bone growth

Question 1

functions of bone

Answer 1

protects organs, blood cell production, mineral storage pool, levers for muscle action, supports body shape

Question 2

mechanical properties of bone

Answer 2

CABLE -LIKE FLEXIBILITY (some flexibility)- made out of mainly collagen, so resistant to TENSION PILLAR-LIKE STIFFNESS- collagen enforced by hydroxyapatite crystals, so resistant to COMPRESSION

Question 3

DIAGRAM structure of bone

Answer 3

bone has two types of tissue- woven (immature bone), and lamellar (mature bone)- lamellar more organised, woven more irregular

Question 4

woven bone in adults

Answer 4

not found in adults- only in repairing fractures

Question 5

DIAGRAM features of the long bone (femur)

Answer 5

head (epiphysis) has spongy bone, shaft (diaphysis) has compact bone, and distal end also epiphysis most of shaft is hollow (medullary cavity) with marrow inside

Question 6

arrangement of lammellar bone

Answer 6

outer compact layer (CORTICAL bone), with inner spongy/CANCELLOUS/trabecular bone (NOT woven, even though it looks irregular)

Question 7

what is lamellar bone arranged like this

Answer 7

so that bone is not too heavy, and it allows space for lots of bone marrow

Question 8

DIAGRAM cortical vs spongy bone and blood supply

Answer 8

they have structures of OSTEONS, which has a central canal of vessels- bone has a large blood supply

Question 9

periosteum DIAGRAM

Answer 9

the outer surface of bone- needed for bone growth/repair also vascular, and well innervated (pain in bone due to this region)

Question 10

bone cells

Answer 10

osteogenic cells form osteblasts (form bone matrix), which form osteocytes (maintain bone tissue) osteoclasts also present (has RUFFLED BORDER), which breaks down bone matrix

Question 11

bone development landmarks

Answer 11

skeleton develops at 6 weeks of fetal life, and continues until 25 yrs of age

Question 12

bone development- two types of ossification

Answer 12

intramembranous- in vascular connective tissue, where bone matrix (osteoid) built around collagen, and its mineralised to form woven bone, which becomes lamellar endochondral

Question 13

use of intramembranous ossification

Answer 13

for flat bones like in skull, and mandible

Question 14

endochondral ossification and growth in bone length

Answer 14

long bones have to cope with large forces whilst still needing to grow eg as a toddler- thus wouldn’t make sense to grow at its ends, so shaft ossified first, THEN epiphyses

Question 15

DIAGRAM how endochondral ossification works when growing

Answer 15

a cartilage model of bone develops: this model then is calcified and dies: primary ossification centre forms at shaft and matrix calcified- secondary centre forms at epiphyses, and cartilage/epiphyseal plates form between the shaft and epiphyses, where growth occurs (first shaft, then epiphyses

Question 16

DIAGRAM adult vs child hand

Answer 16

hand not broken, arrows pointing to epiphyseal plates wrist bones in child spaced out due to cartilage in between

Question 17

adaptability of bone

Answer 17

grows whilst withstanding force can remodel- increases/decreases density depending on usage (eg less dense in space), or even external shape can also repair in fractures

Question 18

keys of growth/remodelling

Answer 18

large blood supply osteocytes maintain matrix, but activate osteblasts as well osteoclasts important for remodelling

Question 19

growth in bone DIAMETER (width)

Answer 19

known as apposition ie cells in periosteum activated to become osteoblasts, which form ridges- these ridges close off to form central canal, and bone grows around it

Question 20

DIAGRAM healing of fractures

Answer 20

hematoma forms in fractures, which is infiltrated by connective tissue cells and blood cells, which forms woven, then mature bone thus BLEEDING IMPORTANT

Question 21

role of calcium

Answer 21

if Ca2+ high, calcitonin by parafollicular cells releasts, INHIBITING osteoclasts, and Ca2+ uptake into bone promoted if low, PTH released, promoting osteoclast bone resorption+ reabsorption by kidneys