Functions of the Human Skeleton
 Support and protect body organs
 Provide movement
 Contain red marrow, the site of blood cell
production
 Stores calcium, fats, and other substances
for the body
Two Types of Bone Tissue
1. compact bonedense and looks
smooth and
homogeneous
2. spongy bone –
composed of small
needlelike pieces
of bone and lots of
open space
Structure of Bones
 4 types of bones (classified by shape and their
composition)
1. long – longer than wide, shaft with head at both
ends. Mostly compact bone . Examples: arms and
legs
2. short – generally cube shaped and contain mostly
spongy bone. Examples: wrist & ankles
3. flat – thin, flattened, and usually curved. They
have two thin layers of compact bone sandwiching a
layer of spongy bone between them. Examples: most
bones of the skull, ribs, and sternum
4. irregular – Bones that do not fit into other
categories. Examples: vertebrae and hip bones
Classification of Bones
Classification of Bones
Structure of Long Bones
Structure of a Long Bone
 The diaphysis, or shaft, makes up most of the bone’s
length and is composed of compact bone; in adults it’s
cavity contains yellow marrow for storage of adipose
tissue.
 The epiphyses are the ends of the long bone. They are
covered with hyaline cartilage and they contain spongy
bone. In adults, red marrow is found there and is the
site of blood cell formation.
Femur
Bone markings: Table 5.1
 Projections or processes:
sites of muscles and
ligament attachment;
help form joints












Tuberosity
Crest
Trochanter
Line
Tubercle
Epicondle
Spine
Proccess
Condyle
Ramus
Head
Facet
 Depressions or cavities:
indentations in the bone;
openings that allow blood
vessels and nerves to pass






Meatus
Sinus
Fossa
Groove
Fissure
Foramen
Microscopic Anatomy
 Mature bone cells are
 Canals carry blood
called osteocytes and are
found in tiny cavities
called lacunae.
 The lacunae are arranged
in concentric circles
called lamellae around
central (Haversian
canals).
vessels and nerves to all
area of the bone to
provide the living bone
cells with nutrients and a
route for waste disposal.
 Tiny canals, called
canaliculi, radiate
outward from the central
canals to all lacunae.
Bone Cells
Each
complex
consisting of
central canal
and matrix
rings is
called an
osteon (or
Haversian
system)
Microscopic Anatomy
 Because of the elaborate network of
canals, bone cells are well nourished in
spite of the hardness of the matrix, and
bone injuries can heal well.
Bone formation
 The skeleton is formed from two of the strongest and
most supportive tissues in the body: cartilage and
bone.
 Process of bone formation: ossification
 Bone forming cells: osteoblasts
 Bone destroying cells: osteoclasts
 When blood calcium levels drop below normal, the
parathyroid glands release PTH (parathyroid hormone),
which stimulates osteoclasts to break down bone matrix
and release calcium ions into the blood
Bone Growth

Early years - rapid bone
growth (mostly cartilage)
 Middle life - balance is
reached.
 Older life - bone mass
slowly begins to decrease.
 Changes occur in response
to hormones and
mechanical stresses acting
on the skeleton
Bone Fractures: Table 5.2
 A fracture is a break in bone.
 Simple – bone breaks cleanly and does not penetrate the
skin
 Compound – broken bone ends penetrate through the
skin
 Compression – Bone is crushed
 Comminuted – Bone breaks into many fragments
 Greenstick – Bone breaks incompletely
 Impacted – Broken bone ends are forced into each other
 Spiral – Ragged break occurs when excessive twisting
forces are applied to a bone