12. Bones and skeletal tissues

Question 1

what are the diff types of cartilage

Answer 1

Elastic: areas starting w/ E: external ear, epiglottis

Fibrocartilage: areas that have lots of pressure: intervertebral disc, pubic symphysis, meniscus

Hylane: everytihg else

Question 2

how does cartilage grow?

Answer 2

1. Appositional growth
   
   • growth occurs at surface between existing cartilage and perichondrium
   • Adds protuberance to surfaes (bumps)
2. Interstitial growth
   
   • gets bigger fron inside
   • chondrocytes divide (isogenous groups) and secrete new matrix
   • inc overall size of cartilage

Question 3

why and how does cartilage calcify

Answer 3

• Why
  
  • sites where cartilage connects with bone
  • caritage about to be replaced by one
  • nutritionally/oxygen comprised (injury/aging) (deprived)
• How
  
  • chondrocytes hypertorphy and secrete enzymes to reode extracelular matrix
  • Calcium Phosphate is deposited & matrix crystalizes
  • Chondrocytes die (leaves spaces)

*callify the cartilage not bone

Question 4

what are the two bone textures

Answer 4

• spongy (cancellous/trabecular ) bone
  
  • honeycomb mesh of bonny spines called trabeculae
  • spaced filled with bone marrow
• Compact bone
  
  • dense outer layer
  • appears smooth and solid to naked eye

Question 5

Describe the periosteum membrane of the bone

Answer 5

• composed of 2 layers: fibrous layer & osteogenic (cellular) layer
• secured to underlying bone by perforating (sharpey’s) fibers

Question 6

describe the endosteum membrane of the bone

Answer 6

• delicate membrane on itnernal surface of bone that covers:
• > trabeculae of spongy bone
• > canals of compact bone
• > marrow cavity

*constains osteogenic cells

Question 7

decsribe the microscopic anatomy of compact bone

Answer 7

• Haversian system (osteon)
  
  • ​structural unit
• Central (haversian) canal
  
  • ​goes thru middle
  • contains blood vessels and nerves (why hurts to break)
• Lamellae
  
  • ​weight beaing
  • column like atrix tubes
  • collagen fibers & bone salts in each layer run in same direction
  • interstitial lamellae found between osteons
  • Circumferential lamellae found deep to periosteum & linig of medullary cavity

Question 8

describe perofrating (volmann’s) canals

Answer 8

• at right angles to central canal
• connects blood vessels and nerves of periosteum & central canal
• lined with edosteum

Question 9

describe the microscopic anatomy of compact bone

Answer 9

• has Lacunae: small cavities that contain osteocytes

*located at jucntions of lamellae

• canaliculi: hairlike canals that connect lacunae to each other and to the central canal

*allows cells to communciate with each other and the central cannal

Question 10

what are trabeculae

Answer 10

• part of microscopic anatomy of spongy bone
• align along lines of stress
• contain irregularly arranges lamellae, osteocytes and canaliculi (no osteons)

*no tubes but still organization of sheets

= capillaries in endosteum supply nutrients

Question 11

short, irregular and flat bones are covered by

Answer 11

• thin plates of cpongy bone covered by compact bone
• then covered by periostem and endosteum
• hyaline cartilage covers articulation points
• contains bone marrow between trabeculae

Question 12

describe the strucutre of long bone

Answer 12

• Diaphysis (shaft)
  
  • compact bone collar surrounds medullary cavity
  • medullary cavity (adults) contain fat = yellow marrow
• Epiphyses (expanded ends)
  
  • spongy bone interior (red marrow)
  • epiphyseal line (aka metaphysis) is adult remnant of growth plate
  • arituclar (hyaline) cartilage on joint surfaces

Question 13

bone is vasular or avasculat

Answer 13

• vascular
• nerve fibers, nutrient blood vessels and lymphatic nessels enter bone via nutrient foramina

Question 14

wbere is hematopoietic tissue located?

Answer 14

• in red marrow
• Red marrow cavities in adults:
  
  • trabecular cavities of heads of femur and humerus
  • trabecular cavities of spongy bone of flat bones
• Red marrow of newborn infants
  
  • medullary cavities & all spaced in spongy bone

Question 15

what cells are involved bone

Answer 15

* make of the organic portion

• Oseogenic (osteoprogenitor) cells
  
  • mitotically active stem cells in periosteum and endosteum
  • stored as resevoir, like stem cells they can divide and differentiate
• Osteoblast (b, build bone)
  
  • mitotically active bone-forming cells that synthesize osteoid
  • can become osteocytes or bone lining cells
• Osteocytes
  
  • mature bone cells in lacunae that maintain bone matrix
  • occurs when they are completely surrounded by matrix they control
• Bone lining cells
  
  • mature cells on bone surfaces that maintain bone matrix
• Osteoclasts
  
  • fused macrophages (multinucleated) that break down (resorb) bone matrix