Download Name: Pd. _______ Chapter 5: The Skeletal System Objectives

Name: ______________________________________
Pd. ____________
Chapter 5: The Skeletal System
Objectives:
Students will be able to:
 Identify the subdivisions of the skeleton as axial or appendicular.
 List at least three functions of the skeletal system.
 Name four main classifications of bones.
 Identify the major anatomical areas of a long bone.
 Briefly describe the process of bone formation in the fetus, and summarize the
events of bone remodeling.
 Name various types of fractures.
 Identify and name the bones of the skull.
 Discuss the importance of vertebral discs and spinal curvatures.
 Identify the bones of the shoulder and pelvic girdle, and their limbs attached.
 Identify some of the causes of bone and joint problems throughout life.
Although the word skeleton comes from the Greek word meaning “dried-up body,” our
internal framework is so beautifully designed and engineered that it puts any skyscraper
to shame. Our bones are strong, yet light, and perfectly adapted for its functions.
Bones: An Overview
The skeletal system consists of:
1. _____________________
2. _____________________
3. _____________________
4. _____________________
The skeleton is subdivided into two divisions: the ___________ skeleton (bones that form the
longitudinal axis of the body) and the __________________________ skeleton (bones of the limbs
and girdles).
Besides contributing to body shape and form, our bones perform several important
functions:
1. _______________________
2. _______________________
3. _______________________
4. _______________________
5. _______________________
Classification of Bones
The adult skeleton is composed of ____ bones. There are _____ basic types if osseous,
or bone tissue:
1. _________________ bone
 dense smooth homogenous appearance
2. _________________ bone
 small needle-like pieces of bone, with lots of open space
Bones come in many sizes and shapes.
1. ____________ bones
 typically longer than wide
 have a shaft with heads at both ends
 contain mostly compact bone
o ex. femur, humerus
2. ____________ bones
 generally cube-shaped
 contain mostly spongy bone
o ex. carpals, tarsals
3. ____________ bones
 Thin and flattened
 Usually curved
 Thin layers of compact bone around a layer of spongy bone
o ex. skull, ribs, sternum
4. _________________ bones
 Irregular shape
 Do not fit into other bone classification categories
o ex. vertebrae and hip
Structure of a Long Bone: Gross Anatomy
The gross structure of a long bone is depicted below. The _______________, or shaft,
make up most of the bone’s length and is composed of ___________ bone. The ________________,
or ends of bone, is composed mostly of ____________ bone coated with a thin layer of
compact bone. The diaphysis is covered and protected by a fibrous connective tissue
membrane called __________________, which is secured to the bone by a connective e tissue
called ________________ (Sharpey’s) fibers. There are _____________ supplying the bone with
nutrients. The ends of bone are not covered with periosteum, but instead with hyaline
cartilage called _____________ cartilage. The glassy texture of the hyaline cartilage provides a
smooth, slippery surface that _____________ friction at the joint surfaces.
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In adult bones, there is a thin line of bony tissue spanning the epiphysis that looks
slightly different from the rest of the bone in the area, called the epiphyseal line. The line
is remnant of the epiphyseal plate found in a young, growing bone. Epiphyseal plates
cause the lengthwise growth of a long bone. By the end of puberty, when hormones inhibit
long bone growth, epiphyseal plates have been completely replace by bone, leaving only
the epiphyseal line.
In adults, the cavity of the shaft is primarily storage for _____________ tissue, this area
is called the _____________ (yellow marrow) cavity. In infants, this area contains _________
marrow, where blood cells form.
Bone markings are sites of attachment for __________, _____________, and
__________________. Some serve as passages for ____________ and __________ _____________. Bone
markings fall into two categories:
1. _________________ or _______________, which grow out from the bone surface
-usually terms beginning with T
2. _________________ or _______________, which are indentations in the bone
-usually terms beginning with F
Microscopic Anatomy
To the naked eye, spongy bone has a spiky, open appearance, whereas compact
bone appears to be dense. Looking at compact bone microscopically it is riddled with
passageways carrying nerves and blood vessels, which provide the living bone cells with
nutrients and a route for waste disposal.
The mature bone cells, _____________________, are found in tiny cavities called
_________________. The lacunae are arranged in concentric circles called _________________.
Lammellae form around central canals, which together make a Haversian system, or
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osteon. Tiny canals called ____________________ radiate outward from the central canals to all
lacunae, to form a transport system that connects all bone cells to the nutrient supply
through the hard bone matrix.
Bone Formation, Growth, and Remodeling
The skeleton is formed from two of the strongest and most supportive tissues in the
body—cartilage and bone. In embryos, the skeleton is primarily made of _____________
_______________. During development of a young child, this replaced by __________. Cartilage
remains only in isolated areas such as the ________ of the nose, parts of the ________, and the
_____________. Except for flat bones, which form on fibrous membranes, most bones develop
using hyaline cartilage as their “models.” The process of bone formation, or ossification,
involves two major phases. First, the hyaline cartilage model is completely covered in
bone matrix by bone forming cells called ___________________. Then the enclosed hyaline
cartilage model is digested away, opening a medullary cavity within the newly formed
bone.
By birth, or shortly after, most hyaline cartilage models have been converted to
bone except for two regions: the articular cartilages, and the epiphyseal plates.
_______________ _________ allow for growth of long bones during childhood. New cartilage is
continuously formed. Older cartilage becomes ossified: cartilage is broken down and bone
replaces cartilage.
Bones are ______________ and _____________ until growth stops. Bones change shapes
somewhat—bones grown in width (appositional growth). The process of long bone
growth is controlled by hormones, most importantly growth hormone, and during puberty,
the sex hormones.
 ______________________________
 ___________________________
o mature bone cells
o bone-destroying cells
o break down bone
 _________________________
o Bone forming cells
o Matrix for remodeling & release of calcium
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Bone remodeling is a process by both osteoblasts and osteoclasts.
Bone Fractures
A ______________ is a break in a bone. There are two main types:
1. _________________________ break that does not penetrate the skin
2. _________________________ broken bone penetrates through the skin
Bone fractures are treated by _____________ (the realignment of the broken ends) and
immobilization (via a cast or traction). Realignment in closed reduction, the ends of the
bone are coaxed back to normal position via physician’s hands. In open reductions, surgery
is performed, and ends are secured with pins or wires.
The repair of bone fractures involves four major events:
1. Hematoma (blood-filled swelling) is formed
2. Break is splinted by fibrocartilage to form a callus
3. Fibrocartilage callus is replaced by a bony callus
4. Bony callus is remodeled to form a permanent patch
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Axial Skeleton
The skeleton is divided into two parts: the __________ skeleton, and the _________________
skeleton. The axial skeleton forms the __________________ axis of the body. It can be divided
into three parts:
1. _____________________
2. _____________________
3. _____________________
The Skull
The skull is formed by two sets of bones: the _________________, which protects the
brain tissue, and the _________ bones, which holds the eyes I the anterior position, and
allows facial muscles to show feelings. All but one bone of the skull are joined together by
_____________ (interlocking immoveable joints). Only the ___________ (jawbone) is attached to
the rest of the skull by a freely moveable joint.
The cranium is composed of _________ large flat bones. They are all single bones
except for two pair bones (the __________ and ____________).
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1. _____________ bone forms the forehead, the bony projections under the eyebrows, and
the superior portion of each eye orbit.
2. ____________ bones are paired bones that form the most superior and lateral walls of
the cranium. They meet at the midline of the skull at the _____________ suture, and
form the __________ suture where they meet with the frontal bone.
3. ____________ bones lie inferior to the parietal bones, and join them at the _____________
sutures.
4. _____________ bone is the most posterior bone of the cranium. It forms the _______ and
back wall of the skull. It joins the parietal bones anteriorly at the lambdoid suture. In
the base of the occipital bone is a large opening called the _____________ magnum,
which surrounds the lower part of the brain and allows the brain to connect to the
spinal cord.
5. _____________ bone is the butterfly-shaped bone that spans the width of the skull, and
forms part of the roof of the nasal cavity, and the medial walls of the eye orbits.
6. ____________ bone is very irregularly shaped and lies anterior to the sphenoid, forming
the roof of the nasal cavity, and the medial walls of the eye orbits.
__________________ bones compose the face. __________ are paired, and only the __________ and
______ are single.
1. ______________ or maxillary bones fuse together to form the upper jaw. All facial
bones except the _____________ join the maxillae, thus is called the ____________________
bones of the face.
2. _____________ bones are paired bones that lie posterior to the maxillae, this forming
the posterior portion of the hard palate. Failure of these bones to fuse results in
__________ palate.
3. ______________ bones are commonly called cheekbones. They form a good portion of
the lateral walls of each eye orbit.
4. ___________ bones are fingernail-sized bones forming part of the medial walls of
each eye orbit.
5. _______ bones are small rectangular bones forming the bridge of the nose.
6. _______ bone is the single bone in the medial line of the nasal cavity.
7. ___________ _______ _________ are the thin curved bones projection from the lateral
walls of the nasal cavity.
8. _____________, or lower jaw is the largest strongest bone of the face. It joins the
temporal bones on each side of the face, forming the only freely moveable joint of
the skull.
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The ________ bone is not really a part of the skull, but is closely related to the
mandible and temporal bones. It is the only bone that does not _______________ with another
bone. It serves as a ______________ base for the _____________.
The maxillae contain sinuses, which are ____________ portions of bones surrounding
the nasal cavity. These sinuses function in _____________ the skull bones and ____________ the
sounds we make as we speak.
The fetal skull is ___________ compared to the infant’s total body. The infant’s face is
small compared to the size of the cranium, but the entire skull is one-fourth as long as the
entire body, whereas in an adult it is one-eighth as long as the entire body. When a baby is
born, its skeleton is incomplete—some areas are still hyaline cartilage. Most importantly,
the skull has fibrous regions that have yet to be converted to bone, called ________________
(soft spots). The baby’s pulse can be felt in these regions. These “soft spots” allow for brain
growth during the latter part of pregnancy, and are usually converted to bone by ___
months after birth.
Vertebral Column (Spine)
The vertebral column serves as the axial support of the body. It extends from the
skull, down to the pelvis, where it transmits the weight of the body to the lower limbs. The
spine is composed of ___ irregular bones called vertebrae, and is connected and reinforced
by ligaments in such a way that a flexible curved structure results. Before birth the spine
consists of ___ separate bones, but 9 of these eventually fuse to form two composite bones:
the sacrum, and the coccyx. Of the remaining 24 bones, __ vertebrae compose the cervical
region of the spine, ___ make up the thoracic region, and the remaining __ support the
lower back and make up the lumbar region.
Vertebrae are separated by pads of fibrocartilage
called _______________ discs. These pads cushion the
vertebrae and absorb shock while allowing the spine
flexibility. In a young person, the discs are composed
of about 90% waste, and are spongy and compressible.
As a person ages, the water content decreases, and
the discs become harder and less compressible.
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Bony Thorax
The ____________ (breastbone), ________, and _______________ vertebrae make up the bony
thorax. It forms a cage to ___________ major organs of the thoracic cavity. There are ____ pairs
that form the walls of the bony thorax. All ribs articulate
with the __________________ _____________ posteriorly, and
then curve downward and toward the anterior body
surface. The first ___ pairs of ribs attach directly to the
___________ by costal cartilage, and are called ____ ribs.
The next five pairs either attach indirectly or do not
attach at all and are called ________ ribs. The last two
pairs of false ribs lack sternal attachment and are
called ____________ ribs.
Appendicular Skeleton
The appendicular skeleton is composed of _______ bones of the _________ (or
appendages), the ___________ (shoulder) girdle, and the _________ girdle. Each pectoral girdle
consists of ___ bones: a _____________ (or collarbone) and a ____________ (or shoulder blade).
The clavicle attaches __________ to the sternum, and __________ to the scapula, where it helps
to form the shoulder joint. The clavicle acts as a brace to hold the arm away from the top
of the thorax, and prevents shoulders dislocation. The ___________ are triangular and
commonly called “wings” because they flare when we move our arms posteriorly.
The shoulder girdle is very light and allows the upper limb to have exceptionally free
movement due to the following factors:
 Each shoulder girdle attaches to the axial skeleton at only one point---the
sternoclavicular joint.
 The loose attachment of the scapula allows it to slide back and forth against the
thorax as muscles act.
 The glenoid cavity is shallow, and ligaments poorly reinforce the shoulder joint.
Due to this exceptional flexibility, the shoulder girdle is very easily dislocated.
Bones of the Upper Limbs
__________ separate bones form the skeletal
framework of each upper limb (the arm, forearm,
and hand). The arm is formed by a single bone
called the ____________. The two bones of the
forearm are the _________ and ________. The radius is
the ___________ bone (located on the thumb side of
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the forearm). The ulna is the _________ bone
(near the little finger) of the forearm.
The hand consists of the ______________, the ________________, and the ___________________.
There are ___ carpal bones arranged in two irregular rows of four bones each, which form
the __________, commonly called the wrist. Ligaments bind
them together restricting movement between them.
The palm of the hand consists of the ___________________, which
are numbered 1 to 5 from the thumb side of the hand to the
little finger. When the first is clenched, the heads of the
metacarpals become obvious as the _________________. The
_______________ are the bones of the fingers. Each hand consists
of ____ phalanges. There are ___ in each finger (named proximal,
middle, and distal), except the ________, which only has __
(____________ and ___________).
Bones of the Pelvic Girdle
The pelvic girdle is formed by __ coxal bones commonly called hip bones. The coxal
bones, the coccyx and sacrum come together to form the bony pelvis. Unlike the bones of
pectoral girdle, the pelvic girdle attach securely to the axial skeleton. Each hip bone is
formed by the fusion of three bones: _________, ____________, and _________. The ilium connects
posteriorly with the sacrum. It is the large flaring bone that forms the hip. The ischium is
the “sit-down bone,” since it forms the most inferior part of the coxal bone. The pubis is
the most anterior part of the coxal bone.
There are consistent differences between a male and female pelvis.
1. The female inlet is the larger and more circular.
2. The female pelvis as a whole is shallower, and the
bones are lighter and thinner.
3. The female ilia flare more laterally.
4. The sacrum is shorter and less curved.
5. The female ischial spines are shorter and further
apart; thus the outlet is larger.
6. The female pubic arch is more rounded because
the angle of the pubic arch is more rounded
because the angle of the pubic arch is greater than
90o.
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Bones of the Lower Limbs
The lower limbs carry our total body weight when we are erect. Therefore these
three bones are much thicker, and stronger than the bones of the upper limbs. The lower
limbs are composed of three segments each: the __________, the _____, and the __________.
The _________ or thigh bone is the
only bone in the thigh. It is the heaviest
and strongest bone of the entire body.
The femur slants medially as it runs
downward to join the leg bones, thus
bringing the knees in line with the
body’s center of gravity. The _________
and __________ comprise the leg. The
_______ or shinbone is larger and
more medial. The anterior border of
the tibia is unprotected by the muscles,
thus us easily felt beneath the skin. The _______ lies alongside the tibia.
The foot is composed of __________, _________________, and ________________. The foot has
two important functions:
1. _________________________________
2. _________________________________
The __________ forms the posterior half of the foot, is composed of __ tarsal bones. Body
weight is mostly carried by the two largest tarsal bones (calcaneus, or heel bone, and the
talus or ankle bone). _______ metatarsals form the toes. Like the fingers of the hand, each
toe has three phalanges, except the great toe, when has ___ bones. The bones in the foot are
arranged to form three strong arches:
 ___________________________________
 ___________________________________
__________________ (which bind the foot bones together), and ________ (which help hold the
muscles of the foot to the bones) help hold the bones in firmly. In the arched position but
still allow a certain amount of give or springiness. Weak arches are referred to as “fallen
arches” or “flat feet.”
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