CT 2 A Flashcards
function of skeletal system:
- Protection for critical organs (e.g. the ribs for the heart and lungs, the skull for the brain)
- Mechanical support for locomotion; by supporting and providing attachments for muscles and joints for flexible movement.
- Calcium and phosphate homeostasis: Bone is a tightly regulated reservoir of calcium for the entire body.
- To house, protect, and regulate the stem cell precursors of blood cells (the hematopoietic system) (a function of bone).
Like all connective tissues, bone and cartilage are composed of ______.
collagen-containing extracellular matrix secreted by cells of the connective tissue family
connective tissues contain specialized cell types that lead to ______.
precise structural organizations and produce specialized ECMs
In particular, the matrix of bone is _____.
mineralized or calcified, i.e. it contains crystals of calcium (Ca2+) and phosphate (PO4)
Bone is a _____ tissue.
highly dynamic
It is associated with numerous blood vessels (vascularized) and is constantly turned over and remodeled even in adults.
Bone maintains a population of precursor cells that are capable of ________.
cell division and differentiation into new bone cells
This flexibility of precursor cells is required to _______.
adjust blood calcium and phosphate levels, to allow repair of damage, and allow changes in structure in response to various stimuli
Cartilage is _____.
avascular in its matrix and is very limited in its ability for repair in adults
cartilage is a template for ____.
conversion into bone
In adults, cartilage retains the capacity to ___
convert into bone, which can cause problems as people age.
Cartilage has two main functions:
(1) to provide a resilient but pliable support structure.
(2) to direct the formation and growth of bone.
Where is cartilage in the fetus?
large segments of the skeleton are composed of cartilage.
This is replaced by bone, so that by adulthood only the articular surfaces of bones (where bones come together at joints) retain cartilage tissue.
Cartilage is also found in specific places such as the:
tracheal rings, nasal passages, the external ear, intervertebral discs, ribs, skull sutures and where certain tendons attach to bones.
Chondrocytes make ____.
cartilage matrix and tissue
Chondrocytes arise initially from _____.
primitive mesenchymal cells during fetal development
Once cartilage structures are formed, chondrocytes can also arise from ____
an external layer of connective tissue that surrounds the cartilage called the perichondrium
undifferentiated mesenchymal cells or fibroblasts of the perichondrium generate new _____
chondrocytes during growth
During cartilage growth, chondrocytes are _____
proliferative and secrete the components of the cartilage extracellular matrix (ECM).
As chondrocytes secrete and surround themselves with matrix they become____
isolated from other cells, coming to reside in an isolated compartment called a lacuna.
Proliferative chondrocytes are called ____
chondroblasts, but in essence they are the same cells engaged in the cell division cycle.
After growth is completed chondrocytes _____
withdraw from the cell cycle, but retain the capacity to secrete cartilage matrix, albeit at lower rates.
Chondrocytes secrete a ___
special extracellular matrix.
three different kinds of cartilage that are distinguished by characteristics of matrix they contain:
- hyaline cartilage
- elastic cartilage
- fibrocartilage
Hyaline cartilage contains _____.
collagen that forms relatively thin fibrils that are generally arranged in an irregular three dimensional pattern
The ground substance of hyaline cartilage is rich in _____
proteoglycans and the free glycosaminoglycan hyaluronic acid, which promotes hydration and flexibility
This structural properties of hyaline cartilage ECM:
- Allows metabolites to readily diffuse through the tissue.
- Promotes resiliency to compression forces during joint movement.
- Allows growth of chondrocytes and matrix from within the matrix.
- During growth, it can calcify and attract cell that initiate bone formation.
Elastic cartilage contains _____.
thin collagen fibrils and proteoglycans, but is distinguished by abundant elastic fibers and interconnecting sheets (lamellae) of elastic material
Elastic cartilage is found in ______.
the external ear, in the epiglottis, and the larynx
Elastic cartilage matrix is designed for ____
elasticity and flexibility, and, at least under normal circumstances, does not calcify
Fibrocartilage contains ______.
large bundles of regularly arranged collagen that is very similar to dense regular connective tissue
Fibrocartilage is found as a _____.
continuation of dense regular connective tissue where tendons attach to bones, and also in the intervertebral discs
Fibrocartilage ECM is designed to ____
resist compression and sheer forces.
Cartilage tissue ______.
avascular
all of the nutrients and metabolites that are needed and produced by chondrocytes must _____
diffuse within the matrix to and from the perichondrium.
What facilitates diffusion of nutrients and metabolites in cartilage?
diffusion is facilitated by the large amounts of hydrated glycosaminoglycans.
