ch 6 - skeletal system Flashcards
Ossification is…?
the mineralization or hardening of bone
What is os and osteo- refers to….?
bone
What are osteocytes?
Bone cells (osteoblasts that have become trapped in the ossified matrix they have created) osteocytes can revert back to osteoblasts and form new bone if needed
Bone is….?
second hardest substance in the body, composed of cells embedded in a matrix,
Matrix is…? Why is it so hard?
the intercellular material of connective tisuse - in which bone is embedded. It is hard because calcium and phosphate crystals are deposited in it
What are functions of bone?
Support, protection, leverage, storage, blood cell formation (marrow)
What are two types of bone?
Cancellous bone; light and spongy- long bones
Compact bone; dense and heavy - bones around head & face
What are cancellous bone
Tiny “spicules” of bone that appear that appear randomly arranged
Spaces between the spicules contain bone marrow
What is compact bone?
Shafts of long bone and the outside layer of all bones
Composed of haversian systems that run lengthwise with the bone
The cells that produce bone are called..?
osteoblasts - they also secrete the matrix of bone and then supply the minerals necessary to harden it.
The suffix -blast indicates…?
a cell that produces something
What is the lacunae?
small cavities within the matrix of some connective tissues, such as cartilage and bone, within which cells (chondrocytes, and osteocytes) are contained.
Once surrounded by bone, osteoblasts get a new name, what is that name?
osteocytes or bone cells
What is canaliculi?
threadlike, cellular processes in tiny channels - osteocytes get food and communicate with each other through these slots (channels)
What allows the muscles to move the joints?
bones act as levers for the skeletal muscles; attachment of skeletal muscles to bones via the tendons allows the muscles to move the joints
How are bones storage sites?
act as storage sites for minerals, such as calcium. They enable the body to deposit and withdrawal minerals as needed to control levels in the bloodstream.
Why is calcium important?
involved in important body functions including muscle contraction, blood clotting, milk secretion, and skeleton formation and maintenance.
Two hormones act as “cashiers” at the calcium bank, what are they?
parathyroid hormone from the parathyroid glands, calcitonin from the thyroid gland
Calcitonin helps prevent ________ which is too high a level of calcium in the blood, largely by depositing excess calcium in the bones.
hypercalcemia
Parathyroid hormone does the opposite: it helps prevent _________ which is too low a level of calcium in the blood, in part by withdrawing calcium from the bones.
hypocalcemia
What is it called when some of the bones serve as sites for blood cell formation?
hematopoiesis — in the blood marrow that fills their interiors
What does the haversian canal contain?
blood vessels, lymph vessels, and nerves that supply the osteocytes
What is located at the junctions between the layers of bone that make up each haversian system?
the osteocytes
The outer surfaces of bones are covered by a membrane called the …?
periosteum
The outer layer of the periosteum is composed of …?
fibrous tissue
The inner layer of the periosteum is composed of ..?
bone-forming cells (osteoblasts)
What does the inner layer of the periosteum do?
enables bones to increase in diameter and is involved in the healing of bone fractures
What does the membrane endosteum do?
lines the hollow interior surfaces of bones - also contains osteoblasts
What are the three types of cells that make up bone?
osteoblasts, osteocytes, osteoclasts
What are osteoclasts?
osteocytes eat bone, necessary for remodeling - remove bone where it is not needed
osteocytes also allow the body to withdraw calcium from the bones when it is needed to raise the calcium level in the blood
Why does the body need cancellous and compact bones?
two different types of bone are important because cancellous bone keeps an animal’s bod weight lower, being lighter than compact bone. Both types of bone are needed to stand up to the stresses encountered by an animals skeleton
What is the difference between a haversian canal and a Volkmann’s canal?
Haversian canals are part of the haversian system of compact bone. These canals contain the blood, lymph, and nerve supply for the osteocytes.
Volkmann canals are channels through which blood vessels travel to supply bones. These canals join with the blood vessels in the haversian canals to bring nutrients to the osteocytes in the haversian systems.
What is the nutrient foramina?
it is large channels where large blood vessels, along with lymph vessels and nerves enter many large bones–especially long bones
Bone is formed by one of two mechanisms, what are they?
endochondral or cartilage bone formation - grows into and replaces a cartilage model or
intramembranous or membrane bone formation - fibrous tissue membranes
Most bones develop by…?
endochondral bone formation - the body first creates a casrtilage “template’ that is subsequently replaced by bone
What are cell the types that make up bone?
osteoblasts,
The function of osteoblasts is?
Bb
