Chapter 5: Skeletal system 021108
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Objectives
·
What are the basic tissues that make the skeletal system.
·
How is bone made originally, and how is it reformatted once you get older.
·
Describe the functions
of the bone.
·
How are connections
between bones made.
·
What are some of
the diseases
and disorders of the skeletal system.
·
Be able to
identify the major bones and their function.
Important Figures
5.1 Know the basic structure of bone.
5.2 Know
how bone develops
5.6 Know the parts
of the skeleton
5.13
Know
how the knee functions
5.14
Know
Flexion, extension and Hyperextension.
1. Characteristics of Bone: To bone or not to bone?
A. Basic
Bone functions and Structure
1) Bones serve these 5 functions:
a) Bones
are moved by the contraction of muscles: thus, the whole body is movable.
b) Bones
enclose and protect vital organs such as the brain, lungs and female
reproductive organs.
c) The
bones support and anchor muscles.
d) Bone
tissue acts as a depository for calcium, phosphorus, and other ions.
e) Some
bones are sites of red blood cell production.
2) There are four types of bones listed according to their shapes: long (arms), short (wrist), flat (skull), and irregular (vertebrae).
3) Bone
is a connective tissue with living cells (osteocytes) and collagen
fibers distributed throughout a ground substance that is hardened by calcium
salts.
a) As
the bone develops, precursor cells called osteoblasts
secrete collagen fibers and ground substance of proteins and carbohydrates.
b) Eventually,
osteocytes reside within lacunae in the ground
substance, which becomes mineralized by calcium deposits
4) The
strong or “compact”
bone tissue forms the bone’s shaft and the outer portion of its two ends: a periostem covers the bone shaft.
a) Concentric
layers surround osteons (haversian
systems) and the Haversian canals at their
centers, which contain blood vessels and nerves.
b) Osteocytes (live bone cells) in the lacunae
communicate by way of canaliculi.
5) “Spongy”
bone tissue may have red marrow that produces blood cells: adults have reserve
yellow marrow (mostly fat), which can be converted to red marrow if blood cell
production needs to be increased.
6) Bone
tissue it not dead. It is constantly
being reorganized and renewed. The more
your bones are used the stronger they become.
The less your bones are used the weaker they become. This can be a problem for those who are
confined or who are in micro gravity environments for extended periods.
B.
How bones Develop: the pattern for your bones is first set out
in cartilage that then turns into bone.
1) Osteoblasts secrete material (Hydroxyapatite) inside the shaft of the
cartilage model of long bones
2) Calcium
is deposited: cavities merge to form the marrow cavity.
3) Eventually
osteoblasts become trapped within their own
secretions and become osteocytes (mature bone
cells).
C. In
growing children, the epiphyses (ends of bones) are separated
form the shaft by an epiphyseal plate
(cartilage), which continues to grow under the influence of growth hormone
until late adolescence.
2. Growth and maintenance of the skeleton quiz
A. Bone is renewed
constantly as minerals are deposited (by osteoblasts) and withdrawn (by osteoclasts) during the “remodeling” process. Bone is constantly being built up and broken
down depending on usage. This is why
astronauts who do note exercise loose bone mass.
1) Bone
turnover helps to maintain calcium levels for the entire body.
B. Parathyroid
hormone causes bone cells to release enzymes that will dissolve bone tissue
and release calcium to the interstitial fluid and blood: calcitonin
stimulates the reverse.
C. Your
bone is constantly being remodeled time and time again.
1) Before
adulthood, bone turnover is especially important in increasing the diameter of
certain bones.
2)
Osteoporosis (decreased bone density) is
associated with decreases in osteoblast activity, sex
hormone production, exercises, and calcium uptake.
3) Bone
remodeling depends on the force that is exerted on the bone. The greater the force the greater the deposit
of bone.
4) Regular
exorcise will substantially increase your bone mass.
D. Overview
of the skeleton.
1) The
206 bones of a human are arranged in two major divisions (axial and Appendicular).
2) Bones
are attached to bones by ligaments: bones are connected to muscles by tendons.
3. Axial skeleton quiz
A.
The Skull
1) The
skull consists of more than two dozen bones.
2) The
cranial vault, or brain case, is a grouping of eight bones.
a) Frontal
bone makes up the forehead and contains the sinuses.
b) Temporal
bones form the lower sides of the cranium and surround the ear canals.
c) A sphenoid bone
forms the eye socket.
d) Parietal
bones form a large part of the skull above the temporal bones.
e) An
occipital bone forms the back of the skull and encloses the foramen
magnum, which is a passageway for the spinal cord.
B. Facial bones
1) The mandible forms the lower jaw: two maxillary bones form the upper jaw
2) Zygomatic bones form the cheekbones : lacrimal bones form the inner eye sockets
3) Palatine bones make up the nasal cavity: a vomer bone forms the nasal septum
C. The vertebral
column, or backbone, extends form the base of the skull to the hipbones
1) The spinal cord extends through a cavity formed by the vertebrae.
2) Humans have 24 separate vertebrae: 7 cervical, 12 thoracic, 5 lumbar, plus a sacrum and a coccyx (which contain fused bones)
3) Cartilaginous
intervertebral disks serve as shock absorbers but may
rupture (herniate) to release fluid, which presses
against adjacent nerves.
D. The
ribs and Sternum.
1) Ribs
(12 pairs) are attached to the vertebrae dorsally and serve as a scaffolding
for the upper body torso
2) Most
of the ribs are attached to the sternum ventrally.
4. Appendicular Skeleton.
A. Pectoral girdle and upper
limbs
1) The
pectoral girdle includes the bones of and attached to the shoulder.
a) The
scapula is a large, flat shoulder blade with a socket for the upper arm
bone.
b) The
clavicle (collarbone) connects the scapula to the sternum.
2) Each
upper limb includes some 30 separate bones.
a) The
humorous is the bone of the upper arm.
b) The
radius and ulna extend form the hinge like
joint of the elbow to the wrist.
c) The
carpels form the wrist: the metacarpals the
palm of the hand and the phalanges the fingers.
B. The pelvic girdle and
lower limbs.
1) The
pelvic girdle includes the pelvis and the legs.
a) The
pelvis is made up of coaxial bones.
b) The
pelvis is broader in females than males: this is necessary for childbearing.
2) The legs contain the body’s large bones.
a) The
femur is the longest bone, expending form the pelvis to the knee.
b) The
tibia and fibula form the lower leg: the kneecap bone is the patella.
Tarsal bones compose the
ankle metatarsals the foot, and phalanges the toes.
A. A synovial joints are the most common and move
freely: they include the ball and socket joints of the hips and the hinge like
joints such as the knee.
1) They
are stabilized by ligaments.
2) A capsule of dense connective tissue surrounds
the bones of the joint.
3) In osteoarthritis, the cartilage at the
end of the bone degenerates.
4) In rheumatoid arthritis, the synovial membrane
becomes inflamed, the cartilage degenerates, and bone is deposited into the
joint.
B. Cartilaginous
joints (such as between the vertebrae) have no gap, but are held together
by cartilage and can move only a little.
C. Fibrous joints also have no gap between
the bones and hardly move: flat cranial bones are an example
6.
Diseases and disorders of the skeletal system
A. Sprain is a stretched or torn ligament. May take a long time to heal because the ligaments have every few cells and a poor blood supply. A large ligament that is torn will not heal and needs to be fixed surgically.
B. Bursitis
and tendonitis
a) Inflammation of the tendons and bursae after injury. Located usually at joints where repetitive banging occurs.
C. Arthritis, or inflammation of the joints.
a) General term for joint inflammation.
b) Mostly
due to general wear and tear occurring over a lifetime, and usually in older
adults.
c) In
time, the cartilage protecting the end of the joints wears out.
d) Rheumatoid
arthritis involves joint inflammation and is caused by the bodies own immune
system.
7. Terms for movement
A. Flexion: decreases the angle of a joint
B. Extension: Increases the angle of a joint
C. Abduction: movement of a limb away form the body's
midline
D. Adduction:
movement of a limb toward the body's midline
E.
Possible assignments:
things to think about
1. Why
do some people consider bone non-living?
Is this true? How would you counter this argument?
2. What is the difference between bone production
in a fetus and the way a bone heals after a break?
3. What muscles are collectively called the
hamstrings, in which sports are these injured
4. What
is a slipped or herniated disc? What are
its most common causes?
5. What
is the effect of exorcising on the production of bone.
6. Why
are two types of cells (ones that break down materials and one that build up
bone) required for healthy dynamic bones??
Multiple-choice questions Click on the letters to see if the answer is correct. If you need to review click on the hyper linked words in the question or the answers.
Click below to see the
question |
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1) The difference between osteoblasts
and osteoclasts are
Osteoblasts make up epithelial tissue and osteoclasts are connective tissue. |
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Osteoclasts are osteoblasts that are trapped within the solid matrix of the bone |
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Osteoblasts deposit (make) bone and osteoclasts remove bone, constantly renewing the structure. |
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Osteoblasts secrete material inside the cartilage model of bones found in infants. |
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Osteoblasts work in the epiphyses and help the bones grow long. |
2. A fellow student was not wearing a helmet and crashes
his motorcycle. She says that she broke
several bones in her skull. Which of the following would be bones that he
may have broken?
The sphenoid bone |
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The occipital bone |
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The mandible |
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The thoracic |
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The sacrum |
Answers 1) C,D,E 2) A,B,C |
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Index This feature is not complete
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