The Skeletal System

1
The Skeletal System

• Bones, joints, and connective tissues

2
Skeletal System Functions

• Support
• Protection of organs
• Framework for
• movement
• Mineral storage
• (calcium phosphate)
• Hematopoiesis
• (Blood cell production
• in bone marrow)

3
Axial vs. Appendicular Skeleton

• Axial
• Skull, rib cage,
• vertebrae
• Appendicular
• Limbs and
• girdles (shoulder,
• pelvic)

4
Skeletal cartilage

• Properties of cartilage
• Made of mostly water
• Contains cells called chondrocytes
• Avascular and has no nerve endings (heals very
  slowly)
• Stops growing during adolescence (deteriorates
  from this point on)
• 3 different types

5
Types of Cartilage (see figure 6.1)

• Fibrocartilage - resists very high compression
  forces (in knee and between vertebrae)
• Hyaline - Most common
• 1) articular - at joints
• 2) costal - (connect ribs to sternum)
• 3) respiratory - larynx and trachea
• 4) nasal
• Elastic - least common type - very flexible
  (external ear and epiglottis)

6
Types of Bones (see figure 6.2 pg.178)
7
Structure of a Long Bone

• Epiphyses - end of long bone
• Diaphysis - shaft
• Articular cartilage - covers epiphyses (provides
  cushion and lubrication at joints)
• Periosteum - double membrane surrounding bone
• Endosteum - lines inner cavities of bone

8
Structure of a Long Bone

• Medullary cavity - contains bone marrow
• Spongy (trabecular) bone - contains red marrow
  (found in epiphyses)
• Compact (cortical) bone - found in diaphysis
• Epiphyseal plate - hyaline cartilage from which
  bone growth occurs in childhood and adolescence

9
Microscopic Anatomy of Compact Bone (see Figure
6.6 on pg.183)
Haversian Canal
10
Chemical Composition of Bone

• Organic component (35) bone cells and osteoid
• Osteoid - secreted by osteoblasts (most collagen
  as well as other protein compounds)
• Responsible for bone flexibility
• Inorganic component (65) mineral component
• Hydroxyapatites - Ca3(PO4)2 aka calcium phosphate
• Responsible for hardness of bone

11
Cell Types

• Osteoblasts - bone building cells
• Osteoclasts - resorb (break down) bone (secrete
  HCl)
• Osteocytes - mature bone cells (maintain bone
  matrix)

12
What is Ossification?

• Ossification (also osteogenesis) means bone
  formation
• Starts before birth and extends throughout life
• Types
• - intramembranous ossification (forms bones of
  the skull as well as clavicles)
• - endochondral ossification (forms all bones
  below the skull and clavicles)

13
Endochondral Ossification

• Replacement of hyaline cartilage with bone - see
  Figure 6.8 on pg 185
• Ossification begins in the middle of the bone
  (primary ossification center)
• At birth, epiphyses remain mostly cartilaginous
• By early childhood, hyaline cartilage only
  remains in the epiphyseal plate and covering the
  epipyses (articular cartilage)

14
Post-natal Bone Growth

• Growth occurs from the epiphyseal plate (see left
  side of Figure 6.10 on pg.187)
• Diaphysis also increases in width as bone
  lengthens (gives bone more stability)
• Regulated by growth hormone (hGH) in childhood
• Growth spurt in teen years cause by androgens
  (sex hormones)
• testosterone (males)
• estrogen (females)

Bone growth at epipyseal plate
15
Post-natal Bone Growth

• After epiphyseal plate has completely ossified,
  bones can only grow in width (appositional
  growth)
• Bone remodeling occurs throughout life
• Bone deposit (osteoblasts) and bone resorption
  (osteoclasts) balance each other out in healthy
  young adults
• See right side of Figure 6.10 on pg 187

Bone growth at epipyseal plate
16
Bone Remodeling

• Bone deposit and bone resorption of the adult
  skeleton
• Occurs to prevent bones from becoming brittle
• Spongy bone is replaced every 3-4 years compact
  every 10 years

17
Control of Bone Remodeling

• Mechanical stress
• weight bearing activity leads to bone deposit to
  strengthen areas most in need (Wolffs Law)
• Hormonal control (see figure 6.12 on pg. 189)
• Calcitonin - stimulates bone deposit
• Parathyroid hormone (PTH) - stimulates bone
  resorption

18
Types of fractures (pg.191)

• Nondisplaced vs. displaced
• Complete vs. incomplete
• Linear vs. transverse
• Open (compound) vs. closed (simple)
• Fractures are treated with closed reduction
  (hands are used to align bone ends) or open
  reduction (screws, rods, wires, etc are used to
  keep bone ends together)

19
What is a joint?

• Area where two bones meet

20
Ligaments and Tendons

• Ligaments
• Connect two bones together at a joint
• Tendons
• Connect muscles to bones

21
Joint Classification (structural)

• fibrous - bone ends joined by fibrous tissue (ex.
  Sutures in skull, teeth in sockets)
• cartilaginous - bone ends joined by cartilage
  (ex. Vertebral joints, pubic symphysis)
• synovial - bone ends covered by cartilage and
  surrounded by a fluid filled joint capsule lined
  with a membrane (all joints of the limbs and most
  joints in the body)

22
Joint Classification (functional)

• Synarthroses - immovable joints (ex. Sutures in
  skull)
• Amphiarthroses - slightly movable (ex. Vertebral
  joints)
• Diarthroses - movable (most joints)

23
Joint Classification (functional)

• Synarthroses - immovable joints (ex. Sutures in
  skull)
• Amphiarthroses - slightly movable (ex. Vertebral
  joints)
• Diarthroses - movable (most joints)

24
Synovial joint movements and types of synovial
joints

• Movements allowed by synovial joints
• See pages 260-263
• Types of Synovial joints
• Plane, pivot, hinge, condyloid, saddle,
  ball-and-socket
• See pages 264-265

25
Synovial Joints - a type of diarthrotic joint
26
Bursae and Tendon Sheaths

• Function to reduce friction during joint movement
• Bursae are fluid filled sacs found where
  ligaments, muscles, tendons, skin, and bones rub
  together.
• Tendon sheaths wrap around tendons that are
  subjected to friction

27
Synovial joint movements and types of synovial
joints

• Movements allowed by synovial joints
• See pages 260-263
• Types of Synovial joints
• Plane, pivot, hinge, condyloid, saddle,
  ball-and-socket
• See pages 264-265