PP16 Pre and Postnatal Skeletal Development 1

1
PP16Pre and Postnatal Skeletal Development 1

• Chapter 8 pg 137-147
• ANS 3043
• University of Florida
• Dr. Michael J. Fields

2
Functions of Bone

• Support load and stress bearing as well as
  allowing flexibilty for growth
• Locomotion serve as levers via joints
• Protection surround vital organs
• Blood Formation from medullary cavity of bone
• Mineral Homeostasis
• Energy Storage lipids

3
Types of Bone

• Flat and Irregular
• Ribs, skull, pelvis, vertebrae, scapula
• Long
• Femur, tibia, fibula, etc.

4
Types of Bone Tissue

• Figure 2.16
• Compact Bone
• Very dense
• Found in periphery of bones
• Provides rigidity and strength to bone
• Compact bone arranged parallel to lines of stress
• Serves as scaffolding for spongy one

5
Types of Bone Tissue

• Spongy or Cancellous
• Trabeculae long, flattened reinforcements
  internal to compact bone
• Spicules elongated, cylindrical structures
• Part of bone continually being changed during
  bone remodeling process
• Found in vertebrae, flat bones, skull, shafts and
  ends of long bones

6
Femur
Support on edge
Thin scaffolding on inside
7
Organization of Bone Tissue

• Consists of numerous cell types isolated in
  matrix of collagen fibers impregnated with
  calcium salts
• Collagen fibers for flexibility (organic portion)
  
• Prevalent in young animal
• Calcium salts for strength (inorganic portion)
• Prevalent in older animal

8
Where bone lengthens
Thin membrane on outer layer of bone
Shaft
Thin membrane on inner layer of bone
Anatomy of long bones (Fig 2.15)
9
(Only place where long bone growth occurs)
10
(No Transcript)
11
(No Transcript)
12
Anatomy of Long Bones

• Epiphysis ends of long bones
• Composed of hard and spongy bone
• Contains the cartilaginous epiphyseal (growth)
  plate
• Articular cartilage on the joint side (hyaline)
• Diaphysis shaft of bone between two epiphyses
• Composed of hard (outer) bone and spongy (inner)
  bone
• Contains marrow for red blood cell formation
  (especially in young animals)

13
Anatomy of Long Bones

• Metaphysis between epiphysis and diaphysis
• Composed of hard and spongy bone
• Joints form ends of each epiphysis
• Entry of vascular nerves and lymph supply (1st
  point of entry)
• Surface has articular cartilage to form levers
  and decrease friction
• Joints are bound together by ligaments
• Muscles are attached to bone by tendons (regular
  dense connective tissue)

14
Anatomy of Long Bones

• Other Significant Structures
• Periosteum
• Outer connective layer with and inner cell-rich
  layer containing osteoblasts
• Responsible for increase in diameter of bone by
  appositional growth
• Second point of entry for blood vessels and
  nerves into bone
• Endosteum
• Tissue lining inside of long bones, facing marrow
• Contains ostoprogenitor cells
• Osteoblasts bone growth
• Osteoclasts bone breakdown

15
Osteocytes
16
Compact bone
17
Anatomy of Long Bones

• Medullary Cavity
• Consists of soft connective tissue
• Red bone marrow
• Chief blood cell forming organ in adult
• Located in spongy bone of epiphysis of the long
  bones and main bodies of sternum, ribs and
  vertebrae
• Yellow bone marrow
• Composed of adipose tissue
• Located in medullary cavities of long bones

18
Outside
Inside
19
Outside
______________
Osteocytes
Osteon (circle)
Inside
20
(No Transcript)
21
Other Structures of Bone

• Haversian System
• Cylindrical in nature with long axis parallel to
  long axis of long bone
• Provides vasculature that communicates with
  external surfaces and marrow
• Central canal is surrounded by concentric layers
  of bone called lamellae
• Interstitial lamellae area between osteons
• Contains osteocytes that communicate via
  canaliculi
• Osteon functional unit of bone

22
Other Structures of Bone

• Haversian System
• Contains lacunae (little lakes), which contain
  osteocytes
• Osteocytes communicate through a network of
  canals known as canaliculi
• Interstitial fluid flows through lacunae and
  canaliculi from blood vessels to maintain the
  health of osteocytes
• Volkmans Canals perpendicular to long axis of
  bone and contains vessels that communicate
  between osteons

23
Types of Bone Cells

• Osteoprogenitor Cells
• Mesenchyme cells
• Interact with epithelial cells
• Determine site of bone formation
• Oteoblasts
• Differentiated osteoprogenitor cells
• Produce collage and ground substance of
  unmineralized bone (bone matrix)

24
Types of Bone Cells

• Osteocytes
• Mature osteoblasts enclosed in bone matrix
• Differentiation into an osteocyte requires
  expression of a transcription factor cbfa1 (core
  binding factor alpha 1)
• In adult bone there are 10x more osteocytes than
  osteoclasts
• Maintains bone matrix by synthesis and limited
  reabsorption of the matrix
• Connected to other osteocytes by cytoplasmic
  processes

25
Types of Bone Cells

• Note
• Chondrocytes produce cartilage
• Fibroblasts produce collagen
• Osteoclasts
• Large, multinucleated and motile bone resorbing
  (breakdown) cells
• Precursors are stem cells in blood producing
  tissues of bone and marrow
• In adult bone, number is much smaller compared to
  osteoblasts

26
Types of Bone Cells

• Bone Lining Cells
• Inactive cells found on bone surfaces
• May serve as osteoblast precursors

27
Composition of Adult Bone

• Water 25
• Minerals 45
• Calcium and Phosphorous
• Calcium phosphate (hydroxyapatite)
• Calcium carbonate
• Organic portion 30
• Collagen 90 of organic portion

28
Cells of Adult Bone

• Osteoprogenitor Cells
• Osteoblasts
• Osteocytes
• Collagen / Mineralized Bone
• Osteoclasts