skeletal system

Question 1

what does the skeletal system consist of?

Answer 1

bones and joints(articulations)

Question 2

what are its functions?

Answer 2

protects/supports organs
mineral storage calcium and phosphate
blood cell synthesis in red bone marrow
framework for muscle attachment

Question 3

what tissues does it consist of?

Answer 3

compact/cortical (strong/dense organized into osteons)
cancellous/spongy (network of trabeculae)
cartilage

Question 4

what are the three types of cartilage?

Answer 4

elastic-forms external ear and epiglottis
fibrous- forms mensici and intervertebral discs
hyaline- forms nasal cartilages, respiratory cartilages, costal cartilages, covers ends of long bones

Question 5

what are bone cells?

Answer 5

osteocytes

Question 6

how is compact bone organized?

Answer 6

organized into units called osteons with central canals
containing blood vessels and nerves
osteocytes sit in lucanae within matrix

Question 7

what is the matrix of bone organized into?

Answer 7

concentric rings (lamellae)

Question 8

what are the lacunae connected by?

Answer 8

small canals called canaliculi

Question 9

what is spongy bone?

Answer 9

osteocytes and trabeculae web-like network
light but strong

Question 10

how many bones in adults vs children?

Answer 10

206 in adults and 300+ in infants before fusion

Question 11

what are bones considered in the skeletal system?

Answer 11

organs

Question 12

what are the four classifications of bones?

Answer 12

long bones- femur, humerous, tibia, fibula, ulna, phalanges
short bones- round/square tarsals carpels
flat bones- scapula, sternum, ribs, cranial bones
irregular bones- vertebrae, maxilla, mandible, ossicles

Question 13

what are bones that form between tendons?

Answer 13

sesamoid bones eg the patella

Question 14

what are bones between the cranial bones?

Answer 14

sutural/wormian bones

Question 15

what does spongy bone contain and covered in?

Answer 15

covered in endoosteum and contains red bone marrow

Question 16

what does red bone marrow do?

Answer 16

site of blood cell synthesis

Question 17

what is the process describing bone growth?

Answer 17

osteogenisis or ossification

Question 18

when does bone growth begin?

Answer 18

begins during embryonic development approx 8 weeks gestation

Question 19

what regulates bone growth?

Answer 19

regulated by the growth horomone GH secreted by the pituitary gland

Question 20

what are the bones first modelled in before growth?

Answer 20

fibrous membrane or hyaline cartilage

Question 21

how does growth occur?

Answer 21

mineral matrix is deposited in tissue “calcification”

Question 22

when does calcification cease?

Answer 22

early adulthood male-22 female-18 when the epiphyseal plates ossify

Question 23

what are epiphyseal plates?

Answer 23

are regions at the ends of long bones where growth occurs when these plates ossify an epiphyseal line remains (no more growth possible)

Question 24

what are osteoprogenitors/mesenchymal cells?

Answer 24

stem cells- differentiate into osteoblasts
located in endosteum and periosteum

Question 25

what are osteoblasts?

Answer 25

bone building cells
secrete osteoid (collagen and proteogylcans)

Question 26

what are osteoclasts?

Answer 26

bone-consuming cells (large multinucliate cells derived from stem cells in bone marrow)
secrete acids and enzymes that dissolve and re-shape bones

Question 27

what are osteocytes?

Answer 27

mature bone cells (derived from osteoblasts)
maintain bone matrix

Question 28

what are the two types of ossification?

Answer 28

intramembranous and endochondral

Question 29

what is intramembranous ossification?

Answer 29

growth of flat bones of skull and clavicles
bones are initially modeled in fibrous membrane (similar to dermis in structure)

Question 30

what are the steps in intramembranous ossification ?

Answer 30

1. osteoprogenitor cells cluster in fibrous membrane
2. then differentiate into osteoblasts
3. which secrete osteiod (collagen network) around a network of blood vessels
4. osteoids then go through calcification and CaPO4 is deposited and spicules connect to form trabeculae (spongy bone)

Question 31

when trabeculae thicken at surface what does it form?

Answer 31

compact bone

Question 32

what do trapped osteoblasts mature to become what?

Answer 32

osteocytes

Question 33

what is endochondral ossification?

Answer 33

most bones( long,short,irregular)
bones initially modeled in hyaline c.t
growth occurs in several ossification centres
chondrocytes die as ossification proceds and c.t in replaced by bone
growth in length occurs at epiphyseal plates in long bones

Question 34

steps in endochondral ossification?

Answer 34

1. hyaline c.t model surrounded by perichondrium
2. chondrocytes of c.t die/enlarge
   3.osteoprogenitor cells in perichondrium convert to osteoblasts and from periosteum
3. osteoblasts and blood vessels invade c.t forming a primary ossification centre in diaphysis
4. osteoblasts secrete osteoid; medullary cavity formed by osteoclasts
5. blood vessels/ osteoblasts migrate into epiphyses forming secondary ossification centre
6. osteoblasts secrete osteoid at epiphysis (epiphyseal c.t seperates epiphysis from diaphysis
7. new c.t produced at epiphyseal c.t as bone continues to lengthen
8. appositional growth (increase in bone diameter) occurs when osteoprogenitor cells in periosteum differeintiate into osteoblasts and secrete osteoid
   8.