Bones provide structure, protect organs, allow movement, and store minerals. The 206 bones in the human body develop through two processes - intramembranous ossification and endochondral ossification. Bones continuously remodel through the actions of osteoclasts which break down bone and osteoblasts which build new bone. Joints connect bones and allow varying degrees of movement. The three types are synarthroses, amphiarthroses, and diarthroses. Muscles connect to bones via tendons and contract to create movement by applying force at leverage points. They work antagonistically and synergistically to move the body.

1. Bones, Joints and Muscles

2. Bones: 206 in human body
Function:
– support (eg) pelvic bowl, legs
– protect (eg) skull, vertebrae
– mineral storage (eg) calcium, phosphate, inorganic
component
– movement (eg) walk, grasp objects
– blood-cell formation (eg) red bone marrow
Osteoblasts: secrete organic part of bone matrix = osteoid
Osteocytes: mature bone cells, maintain bone matrix

3. Some Reminders about Bones
Bone = bone tissue (type of CT)
A Bone = an organ
Compact vs. Spongy Bone
Composition: Hydroxyapatite, protoplasm, collagen,
blood vessels, marrow
Skeleton = bones, cartilage (avascular, no nerves, 80%
H2O), joints, ligaments
Shapes of Bones
– Long, Flat, Irregular, Short
Before 8 weeks, embryo is all cartilage

4. Structure of Bone

5. Anatomy of a Long Bone
Diaphysis
– Medullary Cavity
– Nutrient Art & Vein
2 Epiphyses
– Epiphyseal Plates
– Epiphyseal Art & Vein
Periosteum
– Outer: Dense irregular CT
– Inner: Osteoblasts, osteoclasts
– Does not cover epiphyses
– Attaches to bone matrix via collagen fibers
Endosteum
– Osteoblasts, osteoclasts
– Covers trabeculae, lines medullary cavity

6. 2 Types of Bone Formation
1) Intramembranous Ossification
– Membrane bones: most skull bones and clavicle
– Osteoblasts in membrane secrete osteoid that mineralizes
– Osteocytes maintain new bone tissue
– Trabeculae forms between blood vessels
– Grows into thickened plates at periphery = compact bone
– Periosteum forms over it

7. 2 Types of Bone Formation :
2) Endochondral Ossification: All other bones
– Begins with a cartilaginous model
– Perichondrium becomes replaced by periosteum
– Cartilage in diaphysis calcifies
– Trabeculae forms from Periosteal bud
Periosteal bud = arteries & veins, cells forming bone marrow, osteoblasts,
osteoclasts
– Medullary cavity is formed by action of osteoclasts
– Epiphyses grow and eventually calcify
Epiphyseal plates remain cartilage for up to 20 years

8. Bone Growth & Remodeling
GROWTH
Appositional Growth = widening of bone
– Bone tissue added on surface by osteoblasts of periosteum
– Medullary cavity maintained by osteoclasts
Lengthening of Bone
– Epiphyseal plates enlarge by chondroblasts
– Matrix calcifies (chondrocytes die and disintegrate)
– Bone tissue replaces cartilage on diaphysis side
REMODELING
Due to mechanical stresses on bones, their tissue needs to be replaced
– Osteoclasts-take up bone ( = breakdown)
release Ca2++
, PO4 to body fluids from bone
– Osteoblasts-lay down bone
secrete osteoid to form new bone
Ideally osteoclasts and osteoblasts work at the same rate!

9. Joints (articulations)
Where parts of skeleton meet
Allows varying amounts of mobility
Classified by structure or function
Arthrology: study of joints

10. Classification of Joints
Function:
– Synarthroses = no/little movement
– Amphiarthroses = slight movement
– Diarthroses = great movement

11. Joints by Functional Classification
Type Movement Example
Synarthrosis None
(minimal)
Sutures, Teeth,
Epiphyseal plates,
1st
rib and costal cart.
Amphiarthrosis Slight Distal Tibia/fibula
Intervertebral discs
Pubic symphysis
Diarthrosis Great Glenohumeral joint
Knee joint
TMJ

12. Joint Classification
Structure
– Cartilagenous
Synchondrosis: connected by hyaline cartilage (synarthroses)
Symphysis: connected by fibrocartilage (amphiarthroses)
– Fibrous
Sutures: connected by short strands of dense CT (synarthroses)
Syndesmoses: connected by ligaments (varies)
Gomphosis: peg in socket w/short ligament (synarthroses)
– Synovial (diarthroses)

13. Joints by Structural Classification
Structure Type Example
Cartilagenous Synchondrosis
Symphysis
Epiphyseal plates
Intervertebral discs
Fibrous Sutures
Syndesmoses
Gomphosis
Skull
Distal Tibia/fibula
Teeth in sockets
Synovial Glenohumeral joint
Knee joint
TMJ

14. Components of SYNOVIAL JOINTS:
(Structural Joint Classification continued)
Articular cartilage: hyaline; covers ends of both bones
articulating
Synovial (joint) cavity: space holding synovial fluid
Articular capsule: Made of 2 layers
– Fibrous: external, dense CT for strength
– Synovial membrane: internal, produces synovial fluid
Synovial fluid: viscous; lubricates and nourishes;
contained in capsule and articular cartilages
Reinforcing ligaments: extracapsular/intracapsular
Nerves + vessels: Highly innervated, Highly vascular
Meniscus (some): fibrocartilage; improves the fit of 2 bones
to increase stability

15. Synovial Joint
pg 215

16. Bursae & Tendon Sheaths
Bursae: flat, fibrous sac
w/synovial membrane
lining
Tendon Sheaths:
elongated bursae that
wraps around tendons
3 Factors in Joint
Stability:
– Muscle Tone
– Ligaments
– Fit of Articular Surface
pg 219

17. Joint Shapes
Hinge: cylindrical end of 1
bone fits into trough shape of
other
– angular movement-1 plane (eg)
elbow, ankle, interphalangal
Plane: articular surface in flat
plane
– Short gliding movement
– (eg) intertarsal, articular processes
of vertebrae
pg 224

18. Joint Shapes
Condyloid: egg-shape articular
surface + oval concavity
– side-to-side, back+forth movement
– (eg) metacarpophalangeal (knuckle)
Pivot: round end fits into ring of
bone + ligament
– rotation on long axis
– (eg) prox. radius/ulna, atlas/dens
pg 225

19. Joint Shapes
Saddle: articular surface both
concave + convex
– side-to-side, back-forth movement
– (eg) carpometacarpal jt of thumb
–
Ball + Socket: spherical head +
round socket
– multiaxial movement
– (eg) shoulder, femur
pg 225

20. !Muscles!
Function: 1) movement
2) maintain posture
3) joint stability
4) generate heat
!Muscles!

21. Special Features of Muscle
Contractibility = cells generate pulling force
Excitibility = nervous impulses travel through
muscle plasma membrane to stimulate
contraction
Extensibility = after contraction muscle can be
stretched back to original length by opposing
muscle action
Elasticity = after being stretched, muscle
passively recoils to resume its resting length

22. Muscle System: uses levers to move objects
How it works: A rigid bar moves on fixed point
when a force is applied to it, to move object
Lever = rigid bar = bone
Fulcrum = fixed point = joint
Effort = force applied = muscle contraction
Load = object being moved = bone

23. Movements of Muscles
Extension: increasing angle between body parts
Flexion: decreasing angle between body parts
– Dorsiflexion vs. Plantarflexion
– Inversion vs. Eversion
Abduction: moving away from the median plane
Adduction: moving towards the median plane
Rotation: moving around the long axis
Circumduction: moving around in circles

24. Elevation: lifting body part superiorly
Depression: moving body part inferiorly
Supination: rotating forearm laterally
Pronation: rotating forearm medially
Protraction: Anterior movement
Retraction: Posterior movement
Movements of Muscles

25. Muscle Basics to Remember
3 Types: Skeletal, Cardiac, Smooth
Origin vs. Insertion
Direct vs. Indirect Attachments
– direct = right onto bone
– indirect = via tendon/aponeurosis
more common
leave bony markings = tubercle, crest, ridge, etc.
Sometimes attach to skin

26. Functional Muscle Groups
Agonist = primary mover of a muscle, major
response produces particular movement
– (eg) biceps brachii is main flexor of forearm
Antagonists = oppose/reverse particular
movement, prevent overshooting agonistic motion
– (eg) triceps brachii is antagonist to biceps brachii

27. Functional Muscle Groups
Synergists = muscles work together, adds extra
force to agonistic movement, reduce undesirable
extra movement
– (eg) muscles crossing 2 joints
Fixators = a synergist that holds bone in place to
provide stable base for movement
– (eg) joint stablilizers

28. Naming Muscles
Location: (eg) brachialis = arm
Shape: (eg) deltoid = triangle
Relative Size: (eg) minimus, maximus, longus
Direction of Fascicles: (eg) oblique, rectus
Location of Attachment: (eg) brachioradialis
Number of Origins: (eg) biceps, quadriceps
Action: (eg) flexor, adductor, extensor

29. Arrangement of Muscle Fibers
Parallel: long axis of fascicles parallel to axis of
muscle; straplike (eg) biceps, sternocleidomastoid
Convergent: O = broad, I = narrow, via tendon; fan
or triangle shaped (eg) pectoralis major
Circular: fascicles arranged in concentric circles;
sphincter (eg) around mouth

30. Arrangement of Muscle Fibers
Pennate: fascicles short + attached obliquely to
tendon running length of muscle; featherlike
– Unipennate = fascicles insert on only 1 side
(eg) flexor pollicis longus
– Bipennate = fascicles insert both sides
(eg) rectus femoris
– Multipennate = many bundles inserting together
(eg) deltoid

31. Arrangements of Muscle Fascicles
pg 269

32. STOP
More on Levers on the following pages

33. First Class Lever
Effort at 1 end
Load at other end
Fulcrum in middle
(eg) scissors
(eg) moving head up and down
pg 267

34. Second Class Lever
Effort at 1 end
Fulcrum at other end
Load in middle
(eg) wheelbarrel
(eg) standing on tip toes (not common in body)
pg 267

35. Third Class Lever
Load at 1 end
Fulcrum at other end
Force in middle
(eg) using a tweezers
(eg) lifting w/biceps pg 267

36. Mechanical Advantage
When the load is close to
the fulcrum, effort is
applied far from fulcrum
Small effort over large
distance = move large load
over short distance
(eg) Using a jack on a car
pg 266

37. Mechanical Disadvantage
When the load is farther
from the fulcrum than the
effort, the effort applied
must be greater than the
load being moved
Load moved quickly over
large distance
(eg) using a shovel
pg 266