Chapter 5 Skeletal
System
Functions of Bone
- How do bones contribute to homeostasis?
-Protection
-Support
-Movement
-Storage- store fat & minerals
-Blood cell formation- blood cells are formed within the
marrow cavities of certain bones
Anatomy of Bone
Types of Bone
How many bones make up our skeleton?!?
-206!
All bones fall under these two basic types:
Compact Bone:
-Dense
-Smooth
Spongy Bone:
-Composed of
small pieces of
bone
-Lots of space
Types of Bone
After a bone is classified as either compact or spongy they
are further classified according to their shape
-4 types of shape:
Long Bone
-longer then they are wide
-mostly compact bone
Flat Bone
-thin, flattened
-usually curved
-made up of layers of
spongy bone squished
between 2 compact bones
Types of Bone Cont’d
Irregular Bone
-bones that don’t fit into
the other categories
Short Bone
-cubed shaped
-mostly spongy bone
Classification of Bones
- Take a few minutes to classify the bones of the skeleton
Closer look at long
bones
-important structures of long
bone: in the picture your femur
-diaphysis
-periosteum
-epiphyses
-articular cartilage
-epiphyseal line
-epiphyseal plate
Closer look at long
bones
-important structures of long
bone:
-diaphysis: AKA the shaft
-makes up the bone’s length
-covered in protective fibrous
connective tissue called
periosteum
epiphyses: ends of long
bone
-covered by protective
cartilage, articular cartilage
Closer look at long
bones
-important structures of long
bone:
-epiphyses: 2 ends of the bone
-proximal epiphyses
-remember what proximal
means?
-closer to trunk/torso
-distal epiphyses
-distal is the opposite,
further away from the
trunk/torso
Closer look at long
bones
-important structures of long
bone:
-epiphyseal line: found in adult
bones
-remnant of epiphyseal plate
-which is seen in young
growing bones
-cause growing of long
bones
-end of puberty
hormones stop growth of long
bones, the plate is replaced by
bone leaving a line to mark its
location
Microscopic look at long bones
-important structures of compact bone that is only visible
under a microscope:
-riddled with passageways carrying nerves, blood vessels
& provide living bone cells with nutrients
-osteocytes: mature bone cells
-found in tiny cavities within the matrix called
lacunae
-lacunae arranged in circles called lamellae
around central canals
-each complex contains a central canal & matrix
rings are known as osteon or Haversian system
-osteocytes: mature bone cells
-found in tiny cavities lacunae
-lacunae arranged in circles called lamellae around
central canals
-each complex contains a central canal & rings are called osteon or
Haversian system
Red & Yellow Bone Marrow
Yellow Marrow
-middle cavity of a long bone shaft
stores yellow marrow,
AKA medullary cavity
-made of adipose fat tissue
Red Marrow
-in infants middle cavity forms blood
cells & red marrow
-in adults red marrow is confined to
the cavities in spongy none
- Found in flat bones (ribs, vertebrae,
pelvic bones)
Hyaline Cartilage
Abundant cartilage fibers
hidden by a rubbery matrix
with glassy blue-white
appearance
Bone Growth and Formation
Babies
Adults
-Embryo: hyaline cartilage
-Infant: cartilage replaced
by bone
-Almost entirely bone
-Isolated cartilage
remains (nose, ear, etc)
Fibrous membranes connecting flat
bones
Flat bones replace connective
membranes
Bone Growth and Formation
-bones use cartilage as “models” during bone formation
(ossification)
-ossification happens in two steps:
1.Hyaline cartilage model is superficially covered with bone
matrix by osteoblasts
2.Hyaline cartilage is broken down, leaving behind an empty,
medullary cavity.
Ossification
Ossification Cont’d
After birth, only two regions of cartilage remain: articular
cartilages and epiphyseal plates
-articular cartilage covers ends of long bones
https://www.youtube.com/watch?v=p-3PuLXp9Wg
Bone Remodeling
Bones change as the body grows. Why is this
necessary?
As the body changes in size and weight, our bones must
compensate for the additional mass.
Additionally, bones become thicker & form projections where
bulky muscles attach
Bone Remodeling
occurs in response to two factors:
Blood Calcium Levels
Calcium, PTH
PTH activates osteoclasts,
which break down bone to
release Calcium
Calcium, Calcium is
deposited in bones for storage
Determines when skeleton is
remodeled
Pull of gravity and muscles
on the skeleton
Determines where
skeleton is remodeled
Axial & Appendicular Skeleton
Our skeleton is divided into two parts:
Axial Skeleton:
-divided into 3
parts:
-skull
-vertebral column
-bony thorax
Appendicular
Skeleton:
-composed of 126
bones of the limbs
-pectoral & pelvic
gridle
Axial Skeleton
Skull, vertebral column, bony thorax
Appendicular Skeleton
Bones of the limbs and girdles
Joints in our body
Place where two bones come together
Classified by the amount of movement they allow
-immovable
-slightly movable
-freely movable
Joints in our body
4 types of joints in our body:
1. Hinge- only one single action is allowed
-similar to opening & closing a door
Ex:
-our elbow & fingers
2. Ball & socket- rounded curved shape surface of one
bone fits into concave, cup shaped surface of another
bone
-allows for 360 degree movement
Ex:
-our
hip & shoulder bone
Joints in our body
4 types of joints in our body:
3. Pivot- movement occurs in a half circle, rotation of one
bone around another
Ex:
-joint between the axis & atlas of neck
4. Plane/gliding- surfaces are flat, only sliding & twisting
movements are allowed without any circular movement
Ex:
-carpals in our wrist, tarsals in our ankle
Healing a Bone
Occurs in 4 Steps:
1.Hematoma is formed
2.Break is splinted by fibrocartilage
3.Bony callus is formed
4.Bone remodeling occurs