The human skeleton can be divided into two parts: the axial skeleton and the appendicular skeleton. The axial skeleton consists of 80 bones including the skull, vertebral column, ribs, and sternum, and forms the core of the body providing support and protecting organs. The appendicular skeleton is made up of 126 bones organized into the upper and lower limbs, including shoulders, pelvis, arms, forearms, hands, thighs, legs, feet, and ankles. Together the skeleton provides structure, movement, protection, storage, and production of blood cells to the body.

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

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 musclesatrophy
 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

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

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.

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

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

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

31.  Vertebrae named for
their location
◦ 7 cervical vertebrae
 C1 = Atlas
 C2 = Axis
◦ 12 thoracic vertebrae
◦ 5 lumbar vertebrae
◦ Sacrum
 5 fused vertebrae
◦ Coccyx
 4 fused vertebrae
 Vertebrae separated by
fibrocartilage discs
◦ Cushions/absorbs shock

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).

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

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

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

52. THANK YOU