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The skeletal system anatomy
1.
2. The bones primarily give support to the appendages
and protect the fragile organs of the body such as
the brain, spinal cord, heart, and lungs.
They also store calcium and phoshorus in the hard
bone matrix, which can be released when needed
elsewhere.
The bumps, ridges, and grooves on the surface of
bones provide attachment sites for the skeletal
muscles.
Additionally, many bones contain a soft tissue called
marrow that produces new blood cells and stores fat
3. Bone is one of the hardest parts of the body
Very lightweight
Can resist tension
◦ Calcium salts make it hard
◦ Collagen fibers make it strong and flexible
4. Support
Internal framework of body
Ex: Legs support body trunk,
rib cage supports chest wall
Protection
Protects soft body organs (skull
protects brain, ribs protect
heart and lungs, etc)
Movement*
Muscles use bones as levers to
move body
NOT a function skeletal system
can do on it’s own
Storage
Fat storage
In yellow marrow
Mineral storage
Calcium, phosphorus, and
others.
Blood cell formation
Hematopoeisis
Occurs in bone marrow of long
bones
5. The adult human skeleton is a framework of 206
bones and is anatomically divided into two parts,
◦ The axial skeleton
◦ The appendicular skeleton
Two types of bone
◦ Compact bone
Homogeneous appearance
Dense, looks smooth
◦ Spongy bone
Small needle-like pieces
Lots of open spaces
(Looks like a sponge, hence the name)
6. In embryos…
◦ Skeleton made of hyaline cartilage
◦ Gets replaced by bone with age
Cartilage remains in a few places…
◦ Bridge of nose
◦ Parts of ribs
◦ Joints
7. Epiphyseal plates allow for growth of long bone
during childhood
New cartilage is continuously formed
Older cartilage becomes ossified
Cartilage is broken down
Bone replaces cartilage
Bones remodeled, lengthened until growth stops
Bones change shape somewhat
Bones grow in width
8.
9.
10. Osteocyte
◦ Mature bone cell
Osteoblast
◦ “Bone builders”
Osteoclast
◦ “Bone destroyers”
◦ Break down bone matrix to remodel and/or release
calcium
11. Bone remodeling is done by osteoblasts and osteoclasts
Essential for bones to keep normal proportions and
strength
Bones get larger/thicker when…
Large muscles are attached to them
Need more bone to attach the large muscle to
Bones get smaller/weaker when…
Physical inactivity
Non-use of musclesatrophy
Small muscles don’t need large bones to attach to
Bones remodeled to become smaller
12. Long Bones
Longer than wide
Contain shaft with head at
each end
Mostly compact bone
Limbs (not ankle or wrist
bones)
Short Bones
Cube-shaped
Mostly spongy bone
Wrist and ankle bones
Patella (kneecap)
Flat Bones
Thin, flat, usually curved
Two layers of compact
bone with spongy bone in
between
Skull, ribs, breastbone
Irregular Bones
Don’t fit into the other
categories
Vertebrae, hip bones
13.
14. Diaphysis
Shaft
Made of compact bone
Epiphyses
Ends of long bone
Made of compact bone
surrounding spongy
bone
Covered with articular
cartilage
Smooth, glassy, decreases
friction at joints
15. Epiphyseal Line
◦ Line of bone tissue that
looks different from rest
of bone
◦ Remnant of epiphyseal
plate
Hyaline cartilage
Causes long bones to grow
lengthwise
16. Periosteum
◦ Outer covering of shaft
◦ Like “skin” on chicken
bone
Sharpey’s fibers
◦ Attach periosteum to
bone
Arteries
◦ Supply nutrients to bone
cells
17. Medullary Cavity
◦ In shaft
◦ Contains yellow marrow
(adipose) in adults
◦ Contains red marrow in
infants (for blood cell
formation)
18. Osteon (Haversian system)
◦ A “unit” of bone
Central (Haversian) canal
◦ Opening in center of osteon
◦ Contains blood vessels
Perforating (Volkman’s) canal
◦ Perpendicular to central canal
◦ Contains blood vessels and nerves
19.
20. Lacunae
Cavities that contain
osteocytes (bone cells)
Arranged in concentric
rings (like tree rings)
Lamellae
Rings around the central
canal
Where the lacunae can
be found
21. Canaliculi
◦ Tiny canals
◦ Radiate from central
canal to lacunae
◦ Transport nutrients to
bone cells
22. The human skeleton can be divided into two
◦ The axial skeleton
◦ The appendicular skeleton.
The axial skeleton is formed by the vertebral
column, the rib cage, the skull and other associated
bones.
The appendicular skeleton, which is attached to the
axial skeleton, is formed by the shoulder girdle,
the pelvic girdle and the bones of the upper and
lower limbs.
23.
24. The core of the skeleton is referred to as the axial
skeleton. It consists of the following 80 bones.
The upright posture of humans is maintained by the
axial skeleton, which transmits the weight from the
head, the trunk, and the upper extremities down to
the lower extremities at the hip joints.
◦ Skull: 22 bones
◦ Hyoid: 1 bone
◦ Vertebrae: 32 -34 bones
◦ Ribs: 24 bones
◦ Sternum: 1 bone
25.
26. The skull consists of 22 bones and 7 associated
bones. All the larger skull bones are shown in this
exploded view. They fall into two main groups.
◦ One group (including the frontal, parietal, and temporal
bones) surrounds the brain and is fused together to form the
cranium.
◦ The remainder of the bones form the face.
Sutures
◦ Interlocking, immovable joints holding most skullbones
together
Mandible-only freely movable bone in skull
27.
28. This highly flexible structure, also called the
vertebral column, supports the head and body.
It also protects the delicate tissues of the spinal
cord.
It is made up of 32-34 bones called vertebrae,
separated by intervertebral discs, which act as shock
absorbers.
The bones of the spine are kept in place and
supported by attached ligaments and muscles.
29. Hollow portions of bone around nasal cavity
◦ Named for bones they are found in
◦ Lighten skull
◦ Amplify sounds when speaking/ give resonance
30. Large in comparison
to body length of
infant
Contains fontanelles
◦ Soft fibrous membranes
connecting cranial bones
“Soft Spots”
Usually convert to bone
around 24 months after
birth
33. Forms a cage to protect
organs
Three parts
◦ Sternum
Flat bone
3 fused bones
Manubrium
Body
Xyphoid process
Attached to first 7 pair of
ribs
◦ Rib Cage
12 pairs
True Ribs= 7 pair
False Ribs = 5 pair
Floating Ribs = 2 pair
◦ Thoracic vertebrae
34. The appendicular skeleton is
divided into six major regions:
Pectoral girdles (4 bones) –
◦ Left and right clavicle (2)
◦ Scapula (2).
Arms and forearms (6 bones) –
◦ Left and right humerus (2) (arm)
◦ Ulna (2)
◦ Radius (2) (forearm).
Hands (54 bones) –
◦ Left and right carpals (16) (wrist)
◦ Metacarpals (10)
◦ Proximal phalanges (10),
◦ Intermediate phalanges (8)
◦ Distal phalanges (10)
Pelvis (2 bones) –
◦ Left and right hip bone (2).
Thighs and legs (8 bones) –
◦ Left and right femur (2) (thigh)
◦ Patella (2) (knee)
◦ Tibia (2)
◦ Fibula (2) (leg).
Feet and ankles (52 bones)
Left and right tarsals (14) (ankle)
Metatarsals (10)
Proximal phalanges (10)
Intermediate phalanges (8)
Distal phalanges (10).
35.
36. Pectoral girdles (4 bones)
◦ Left and right clavicle (2)
◦ Scapula (2).
37. Arms and forearms (6 bones) –
◦ Left and right humerus (2) (arm)
◦ Ulna (2)
◦ Radius (2) (forearm).
38. Hands (54 bones) –
◦ Left and right carpals (16) (wrist)
◦ Metacarpals (10)
◦ Proximal phalanges (10),
◦ Intermediate phalanges (8)
◦ Distal phalanges (10)
39. Three pairs of fused
bones
◦ Ilium
◦ Ischium
◦ Pubic bone
Carries total weight of
upper body
Protects
◦ Reproductive organs
◦ Bladder
◦ Part of large intestine
40. Female inlet larger/more
circular
Female pelvis is shallower,
bones lighter/thinner
Female hip bones flare
wider
Female sacrum is
shorter/less curved
Female pubic arch is more
rounded/angle is greater
41. ◦ Left and right femur
(2) (thigh)
◦ Patella (2) (knee)
◦ Tibia (2)
◦ Fibula (2) (leg).
42. Left and
right tarsals (14)
(ankle)
Metatarsals (10)
Proximal
phalanges (10)
Intermediate
phalanges (8)
Distal phalanges (10).
43. Articulations of bones
Functions
◦ Hold bones together
◦ Mobility
Classified by
structure/function
Fibrous joints
◦ Immovable
EX: sutures of skull
Cartilaginous joints
◦ Immovable OR slightly
movable
EX: Pubic symphysis and
Vertebrae
Synovial joints
◦ Freely movable
44. Articulating bones
separated by joint cavity
◦ Articular cartilage covers
bone ends
◦ Joint surfaces enclosed by
fibrous capsule
◦ Cavity contains synovial
fluid
◦ Ligaments help reinforce
the joint
Associated Joint
Structures
◦ Bursae
Flat fibrous sacs
Lined with synovial
membrane
Contains synovial fluid
Common where ligaments,
muscles, skin, tendons rub
together
◦ Tendon sheath
Elongated bursa wrapping
around a tendon that deals
with lots of friction
Like a bun around hot dog
45.
46.
47.
48. A break in a bone
Types of Fractures
◦ Simple (closed) fracture
Bone breaks cleanly, does not penetrate skin
◦ Compound (open) Fracture
When bone ends penetrate through skin
Treated by reduction and immobilization
◦ Realignment of bone ends
49.
50. Hematoma forms
Blood vessels rupture
when bone breaks
Blood filled swelling
Cells without nutrients die
Fibrocartilage callus
forms
Made of connective tissue
Splints the break
Phagocytes dispose of dead
tissue
Bony callus forms
Osteoblasts/clasts move in,
create callus of spongy
bone
Remodeling
Osteoblasts/clasts remodel
in response to stress on the
bone
Helps strengthen bone
Creates a permanent “patch”
at the site
Often, a healed fracture can
be stronger than the rest of
the bone