Use one of the skeletons in the room to help you fill out the following:
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If you look underneath the skull of your skeleton, you would be looking inferiorly and see a large hole where the vertebral column
meets the base of the skull. This allows nerves to pass up into the brain and is the ___foramen magnum_________________
_________________, which is an example of a __foramen_________________ a round or oval opening in the bone which allows
blood vessels and nerves to pass through.
If you decided to put your skeleton’s hands on its hips, you would be resting their hands on the iliac _crest_______, which is an
example of a _crest_____________ defined as a narrow ridge of bone, usually prominent that is the site of a muscle and ligament
attachment.
Find the distal anterior portion of the humerus. Notice the two large bumps with the groove in the middle (a metal wire goes
through the groove on our class skeletons). The two bumps are called the medial and lateral __epicondyles__________________.
More generally, __epicondyles_______________________ are raised areas on or above a condyle (a condyle is a rounded articular
projection).
The groove that separates them (#3) is an example of a __fossa_________________, which is a shallow basin like depression in a
bone, often serving as an articular surface.
Now, find where the clavicle articulates with the scapula. The ridge that it articulates with runs along the entire posterior scapula
(run your hand along this). This is an example of _spine________________ which is defined as a sharp, slender, often pointed
projection.
Look at the posterior part of the vertebral column and notice the projections on the vertebra. Which one(s) is/are transverse? Which
one(s) is/are spinous? transverse point to the sides and spinous points directly backwards
These are technically called _processes__________________, which are defined as any bony prominence that attaches to muscles
and ligaments. Look at the proximal end of the femur and find the head, which is the portion that articulates with the hip bone.
Define head. A head is a bony expansion carried on a narrow neck.
Now look at the distal posterior portion of the femur – see the two large bumps. Each of these would be an example of a
__condyles___________________, which is a rounded articulation that helps to form a joint.
Finally, find the hole that is posterior to the zygomatic arch (cheekbone). What is this? external acoustic meatus
Well, we know it’s a type of ___meatus________________ which is a canal-like passageway that allows blood vessels and nerves to
pass through.
Bone Modeling and Remodeling:
Bone is a connective tissue so it is made up of both cells and extracellular matrix. The main cells are
_osteocytes_________________, ___osteoblasts_____________________, and _____osteoclasts______________. The extracellular
matrix is made of both inorganic and organic components. The _osteoblasts_________________ secrete the organic component,
which is mostly made of __collegen_______________ fibers. This gives bone its ___tensile strength_______________, whereas the
inorganic component of bone is made of __calcium ____________ __salts_____________, which give bone its strength and
hardness.
1. Describe the role of these bone cells in the growth of a long bone. Osteoblasts build bone is ossification centers (centers where
blood vessels invade and bone is built up). They also deposit bone in the epiphyseal plate, which replaces cartilage. Finally, they
are present in the periosteum. During appositional growth they add bone tissue to the outside of bones. Osteoclasts eat away
at the spongy bone that forms first to create the space known as the medullary cavity. They are also present in the endosteum
and resorb bone tissue from the inside while osteoblasts present in the periosteum add it on the outside. Osteocytes would be
present wherever osteoblasts had been functioning before because osteoblasts will eventually become osteocytes after they
get trapped in the matrix that they secrete.
2. Describe the role of these long bones in bone remodeling. What regulates their functioning? Osteoblasts build bone in response
to the pull of gravity. Osteoclasts are activated by the parathyroid hormone to resorb bone when calcium levels get too low so
that calcium can be released into the bloodstream. Osteocytes will be present wherever osteoblasts were previously active.
3. Describe the role of these bone cells in the healing of a fracture. Osteoblasts form spongy bone in the third step to make the
bony callus (in place of he fibrocartilage callus). They also deposit bone to form the spongy or compact bone that replaces the
bony callus in the fourth step. Osteoclasts destroy/resorb/eat away at the spongy bone that is formed in the bony callus. They
also function in the fourth step and may resporb some compact bone as the bone is continually being remodeled back to its
original shape.
Bone is made up of spongy and compact bone. Spongy bone is arranged in lattice-like __trabeculae____________________, which
compact bone is arranged in _osteons_________________.
1. Describe the distribution of spongy vs. compact bone in the 4 different types of bones (long, short, flat, and irregular)
Long is mostly compact bone (overall by weight). The spongy bone that is in a long bone is mostly in the epiphysis
Short bones are mostly spongy
Flat bones have two layers of compact bone with spongy bone present in between the two layers.
Describe how the distribution of compact vs. spongy during the growth of a long bone
First a bone collar (made of compact bone will form). Then, spongy bone will form within the compact bone. Finally, most of the spongy bone in the
diaphysis will be removed by osteoclasts so that the medullary cavity can form.
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Describe the distribution of compact vs. spongy in the process of fracture healing.
Spongy bone will form to replace the cartilaginous callus. Depending on where the bone breaks, the bony callus will retain spongy bone or will be
replaced with compact bone and/or a medullary cavity.