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Questions and Answers: The Skeletal System
1. Besides supporting other tissues of the body, what else do
bones do?
Bones provide protection. Their strength protects many delicate and vital
organs and tissues by surrounding them partially or completely. An example:
The skull bones protect the brain and delicate structures of the eyes
and ears. Bones also act as levers for the skeletal muscles to move the
body. Attachment of muscles to bones via the tendons allows the muscles
to move the joints. This enables animals to move around in their environment.
Bones act as storage sites for minerals, particularly calcium. They act
as reservoirs or “banks for this important mineral. This enables
the body to deposit and withdraw calcium as needed to precisely control
its level in the bloodstream. Some of the bones serve as sites for blood
cell formation called hematopoiesis – in the marrow that fills their
interiors.
2. What are the three types of bone cells?
What role does each play in the life of a bone?
Osteoblasts – are the cells that form bone. They
secrete the matrix of the bone and then supply the minerals necessary
to harden it. Once they are trapped in the ossified matrix, they are called
osteocytes.
Osteocytes will again become obsteoblasts if and if necessary,
form new bone. Osteoclasts eat done. They also allow the body to withdraw
calcium from the bones when it is needed to raise the calcium level in
the blood.
3. What is the matrix of the bone made of?
What makes it so hard?
The osteoblasts secrete the matrix of the bone and supply the minerals
needed to harden it. Calcium makes bone hard.
4. What are the main differences between
the structures of cancellous and compact bone? Why does the body need
these two types of bone?
Cancellous bone is sometimes called spongy bone because
it looks sponge. It consists of tiny spicules of bone that appear randomly
arranged with space between them. The spaces between are filled with bone
marrow. It is light, strong, and reduces the weight of the bones of the
skeleton without reducing strength. The spicules are not random, but arranged
to stand up to the forces the bone is subjected to. Muscles, gravity,
and other bones push and pull on the bones. The makeup of the cancellous
bone keeps the bones light while also preventing them from being damaged
by the forces that are acting on them.
Compact Bone is dense, strong,
and heavy. It makes up the shafts of the long bones and the outside layer
of all bone. It is composed of tiny, tightly compacted cylinders called
haversian Systems. Each haversian system runs lengthwise to the bone and
consists of a multi-layered Or laminated cylinder composed of concentric
layers of ossified bone matrix arranged around a central haversian canal.
This canal contains blood vessels, lymph vessels, and nerves that supply
the osteocytes. The osteocytes are located at the junctions between the
layers of bone that make up each haversian system. In a cross section,
these bone layers look like the growth rings of a tree. Tiny channels
through the bone, called canaliculi, allow osteocytes to contact each
other and exchange nutrients and wastes. The body needs these two types
of bone for support, leverage, storage, protection, and blood cell formation.
What are the main characteristics of fibrous
joints, cartilaginous joints, and synovial joints?
Fibrous joints are immovable in that
the bones are firmly united by fibrous tissue. Examples include the sutures
that unite most of the skull bones, and the fibrous union of the splint
bones of horses with the large metacarpal and metatarsal bones. Cartilaginous
joints are termed Amphiarthorosis. They are only capable of a slight rocking
movement. Examples include the the intervertebral disks between the bodies
of adjacent vertebrae in the spine and the symphyses between the two halves
of the pelvis and the two sides of the mandible. Synovial Joints are freely
moveable joints such as the shoulder and stifle join. The anatomical term
for synovial joints is diarthoroses. Most of the joints of the body can
be classified into four basis hinge types: hinge, gliding, pivot, and
ball-and-socket joints
2. What is synovial fluid and why is it
important to the functioning of a synovial joint?
Synovial fluid lubricates the joint surfaces. It is normally transparent,
and has the viscosity Of medium-weight motor oil. Without it, the bones
cannot move freely.
3. What’s the difference between a
tendon and a ligament?
Ligaments are bands of fibrous connective tissue that are present in,
and around many synovial joints. Tendons connect muscle to bone, and ligaments
connect bone to bone.
4.Name some examples of each of these kinds
of synovial joints:
Ball and socket joints – Shoulder and hip joints.
Allows for the most extensive movement of all the joint types, and allows
all the synovial joint movements. Permit flexion, abduction, adduction,
rotation, and circumduction.
Gliding joints – carpus or wrist.
Hinge joints – elbow joint, alantoocipital joint. (Moves the skull
up and down in a nodding “yes” motion.
Pivot joints -- joint between the first and second cervical
vertebrae. Referred to as the no joint Because the only movement it allows
is a rotation back and forth in a no movement. The movement is actually
occurring between the vertebrae, but the head goes along with the first
cervical vertebrae as it pivots on the second cervical vertebrae.
The Skeletal System