SKELETAL SYSTEM
radtech-board.ohd.hr.state.or.us
Functions of the Skeletal
System
•Provide points for attachment for muscles,
assistance in movement
•Protect and support softer tissues
•Blood cell production
•Stores minerals such as calcium and phosphorus.
and releases into or absorbs minerals from
bloodstream
•Form passageways for blood vessels and nerves
Bones classified according to
shape
1. Long bones– long with expanded ends
– thigh bones (femur) and forearm
2. Short bones– cube-like
– wrists and ankles
3. Flat bones– plate-like structures with
broad surfaces
– Ribs, scapula and some bones of skull
4. Irregular bones– variety of shapes
– Vertebrae and many facial bones
5. Sesamoid bones– small and nodular
– Kneecap (patella)
Parts of a Long Bone
1. Epiphysis– expanded
portion at end of bone
which forms joint with
other bones
2. Articular Cartilage–
hyaline cartilage coating
on epiphysis
3. Diaphysis– shaft of
bone
4. Periosteum– tough,
vascular covering of
fibrous tissue enclosing
the the bone
Parts of a Long Bone
5. Compact bone– found in
wall of diaphysis is
compact bone (no
spaces)
6. Spongy bone– found in
epiphysis, has numerous
branching bony plates,
helps to reduce weight
• Both compact and spongy
bone are strong and resist
bending
Compact Bone
• Makes up 80% of the
skeleton
• Forms external layer
of all bones/bulk of
the diaphyses of long
bone
• Provides protection,
support, resists stress
• Arranged in units
called osteon or
Haversian canals
Parts of a Long Bone
7. Medullary Cavity–
hollow chamber along
diaphysis
8. Endosteum– thin
layer of cells line
medullary cavity
9. Marrow– specialized
type of connective
tissue
Endochondral Bones
(and bone growth)
• Most of the bones in the skeleton
• Develop in the fetus from masses of
hyaline cartilage shaped like future bony
structures
• Ossification– formation of bones
• Osteoblasts– bone-forming cells
• Ossification (bone growth) begins in the
center of the diaphysis
Bone Growth
• Starts in diaphysis (primary ossification
center)
• Epiphyseal plate– band of cartilage that is
between the primary ossification center
and secondary ossification center and has
layers of dividing cells (mitosis)
• Bone stops growing when ossification
centers meet
Growth of Bones
Bone Growth
• Osteoblasts deposit bony matrix around
them in the connective tissue
• When they are completely surrounded by
the bony matrix, they are osteocytes
• Osteocytes are bone cells.
• Osteoclasts– secrete an acid and clean
up old bone cells so new bone can be
produced.
Homeostasis of Bone tissue
• Osteoclasts clean up old bone cells and
osteoblasts produce new bone matrix
• 3 to 5% of bone tissue is exchanged each
year
Factors Affecting Bone
Development, Growth and Repair
1. Nutrition
• In the absence of vitamin D, calcium is
poorly absorbed… bones have less
calcium (softening and bone deformation
can occur)
2. Hormonal Secretion
• a) Growth hormone secreted by pituitary
gland stimulates division of the cartilage
cells in the epiphyseal plates.
Factors Affecting Bone
Development, Growth and Repair
continued…
•
B) Sex hormones stimulate
ossification of the epiphyseal
plates
3. Physical Exercise
• Pulling on muscular
attachments to bones
stresses the bones,
stimulating the bone tissue to
thicken and strengthen
Bone Fractures
Use the info on page 137
• Define open fracture (compound fracture)
• Complete the chart on Bone Fracture
types.
Blood Cell Formation
•
Hematopoiesis– the process of blood
cell formation
• As a fetus, hematopoeisis occurs in the
yolk sac, then later in the liver and
spleen, then in the bone marrow.
2 types of marrow:
1. Red marrow– in an infant, it is found in
the cavities of most bones
• As you age, yellow marrow replaces it
• And red marrow is found in the spongy
bones of the skull, ribs, sternum,
clavicles, vertebrae and hip
Blood Cell Formation
continued
Red Marrow:
• Site of formation of red blood cells, white
blood cells and platelets.
• Gets its color from hemoglobin in the red
blood cells
2. Yellow Marrow
• NOT ACTIVE IN BLOOD CELL
PRODUCTION
• Stores fat
Storage of Inorganic Salts
(Homeostasis of Calcium)
• Bones store calcium
• Mostly in the form of calcium phosphate
• If blood is low in calcium, osteoclasts will
break down calcium phosphate and
release Ca to blood stream
• High blood calcium stimulates osteoblasts
to form bone tissue and store calcium
• Maintaining proper Ca levels is important
to muscle contractions, nerve impulses,
and blood clotting
Osteoporosis
low bone density
2 Main Parts of Skeleton
1. Axial Skeleton– supports the head,
neck and trunk
• Skull– cranium (brain case) and facial
bones
• Hyoid– between lower jaw and larynx
supports the tongue and attachments
• Vertebral Column-- backbone
• Thoracic cage– protects organs of the
thoracic cavity
2 Main Parts of Skeleton
2. Appendicular Skeleton—consists of
bones of upper and lower limbs and
bones that anchor the limbs to the axial
skeleton
• Pectoral Girdle– connects upper limbs to
axial skeleton
• Upper limbs
• Pelvic Girdle– connects lower limbs to
axial skeleton
• Lower limbs
Infantile Skull
• Skull is incompletely developed with
fibrous membranes connecting the cranial
bones
• Fontanels– incomplete intramembranous
ossification or “soft spots”
• Allows the skull to be compressible and
change shapes to pass through birth
canal.
• Fontanels will close after birth
Skeleton Parts
• Complete skeleton chart
• Define words and be able to label bones
Function of Joints
Joint– functional junctions between bones
• They bind parts of the skeletal system
• Make possible bone growth
• Permit parts of the skeleton to change
shape during childbirth
• Enable the body to move in response to
skeletal muscle contractions
Types of Joints
•
Classified by type of tissue (most
commonly used type of classification)
1. Fibrous joint– lie between bones that
closely contact one another
• A thin layer of dense connective tissue
joins the bones at such joints
• No appreciable movement
• Called a SUTURE between skull bones
Types of Joints
2. Cartilaginous Joints
• Hyaline or fibrocartilage connects the
bones at these joints
• Slight flexibility at the discs allows for
limited movement
• Examples: intervertebral discs,
symphysis pubis and 1st rib with the
sternum
Types of Joints
3.
•
•
•
•
Synovial Joints
Most joints are this type
Allow free movement
Articular ends of bones
are covered with
hyaline cartilage and a
surrounding dense
connective tissue holds
them together
Has an inner lining of
synovial fluid which
lubricates the joint
Types of Synovial Joints
• Gliding (or Planar)
– Side to side, back and forth gliding movement
– Ex: carpal bones at the wrist
• Hinge
– Produces opening-closing motion
– Ex: knee, elbow
• Pivot
– Rotation around its own longitudinal axis
– Ex. Atlanto-axial joint to allow head to turn from side to side (“no”)
• Condyloid
– Movement in all planes, no rotation
– Ex: movement of index finger
• Saddle
– Mainly in two planes, surface of one bones fit into complementary surface
of another
– Ex: joint between the carpal and metacarpal of thumb
• Ball and socket
– Multi-axial movement
– Ex: shoulder and hip joints
Condyloid Joint
Rheumatism and Arthritis
Rheumatoid
arthritis
Cartilage has
eroded and
fibrous tissues
ossifies and fuses
the joints so that
it becomes
immovable
Types of Joint Movement
Define the types of joint movement and be
able to give examples
Flexion
Extension
Plantar flexion
Dorsiflexion
Hyperextension
Abduction
Adduction
Rotation
Circumduction
Pronation
Supination
Eversion
Inversion
Retraction
Protraction
Skeletal System Interaction
(with other systems)
Complete skeletal system interaction chart.