The Human Skeletal System

1
The Human Skeletal System
2
Skeletal System Form

• bone
• Cartilage fibrous connective tissue
• ligament bone to bone
• tendon bone to muscle

3
Skeletal System Function

• support and anchor muscles
• storage of calcium
• Blood cell Production
• Protection of soft internal organs
• Movement in combination with the muscular system

4
Structure of Bone

• Bone osseous tissue
• Four general shapes
• Long bone
• Short bone
• Flat bone
• Irregular bone

5
Long Bone Features

• Diaphysis
• central shaft
• Surrounds marrow cavity
• Compact bone (dense and solid)
• Yellow marrow fatty tissue (can convert to red)
• Epiphisis
• Expanded ends
• Covered by cartilage
• Spongy bone
• Red marrow makes RBCs
• Periosteum (membrane)
• Protection, growth and repair
• Endosteum (membrane)
• Lines marrow cavity
• Repair and remodeling

6
Bone Tissue Two Types
7

• Are bones alive?

8
Structure of long bone

• Haversian System (osteon) thin circular layers
  around a central canal.
• Central canals are channels for blood vessels and
  nerves
• Canals are connected
• Osteoclast
• living bone cell

9
Bone Remodeling

• Bone is alive and changing.
• This constant changing is called remodeling.
  Remodeling is happening all the time from birth
  to death.
• There are two different types of  bone cells
  involved in the remodeling cycle, osteoclasts and
  osteoblasts. 
• Osteoclasts are responsible reabsorbing bone
• dissolving small pits into the bone they increase
  the concentration of free Ca while decreasing
  the strength and density of the bone.
• osteoblasts BUILD NEW BONE
• Normally this process is precisely balanced and
  has almost no net change in density.

10
Parathyroid hormone and calcitrol increase Ca
in blood
Calcitonin decrease Ca in blood
11

• How do broken bones heal?

12
Bone Fractures (Breaks)

• Bone fractures are classified by
• The position of the ends of the bone after
  fracture (displaced, nondisplaced)
• Completeness of the break (complete, incomplete)
• The orientation of the break to the long axis of
  the bone (linear, transverse)
• Whether or not the bones ends penetrate the skin
  (simple, compound)

13
1. Stages in the Healing of a Bone Fracture

• Hematoma formation
• Torn blood vessels hemorrhage
• A mass of clotted blood (hematoma) forms at the
  fracture site
• Site becomes swollen, painful, and inflamed

14
2. Stages in the Healing of a Bone Fracture

• Granulation tissue (soft callus) forms a few days
  after the fracture
• Capillaries grow into the tissue and phagocytic
  cells begin cleaning debris
• Fibrocartilaginous callus forms

15
Stages in the Healing of a Bone Fracture
Fibrocartilaginous Callus a mass of repair
tissue, occurs when Osteoblasts and fibroblasts
migrate to the fracture and begin reconstructing
the bone Fibroblasts secret collagen fibers that
connect broken bone ends Osteoblasts begin
forming spongy bone (osteoblasts farthest from
capillaries secrete a cartilaginous matrix that
later calcifies)
16
Stages in the Healing of a Bone Fracture
New bone trabeculae appear in the
fibrocartilaginous callus Fibrocartilaginous
callus changes to a bony (hard) callus Bone
callus begins 1-4 weeks after injury, and
continues until firm union is formed 2-3 months
later
17
Stages in the Healing of a Bone Fracture
Bone remodeling begins during bony callus
formation Excess material on the bone shaft
exterior and in the medullary canal is
removed Compact bone is laid down to reconstruct
shaft walls Final remodeled structure resembles
original because it reponds to the same
mechanical stresses
18
Things to Consider

• Why is it good for bones when you exercise?
• Why do you lose weight off the bone of an injured
  leg when you are in a cast?
• Why do astronauts lose bone density?

19
Intro to the Skeleton

• Axial Skeleton
• Skull
• Ribcage
• Vertebral column
• Appendicular Skeleton
• Pectoral girdle (clavical scapula)
• Pelvic girdle
• Limbs
• Humerus, radius, ulna
• Femur, patela, tibia, fibula

20
RAT DISSECTION