Skeletal System (A&P Bootcamp hiegh yield) Flashcards
5 types of Bone
- long bones
- short bones
- flat bones
- sesamoid bones
- Irregular bones
Long bones
made of cortical bone(compact) and pockets of cancellous bone(spongy). Important features include the epiphysis, diaphysis, medullary cavity, metaphysis, and epiphyseal plate.
Epiphysis
end of a long bone that forms
joints with other bones and contains red
bone marrow for hematopoiesis (blood
cell synthesis).
Diaphysis
long hollow shaft in center of
bone.
Medullary cavity
located within the
diaphysis and contains red and yellow
bone marrow (area of fat storage).
Metaphysis
similar to epiphyses and
found between the medullary cavity and
epiphyseal plates.
Epiphyseal plate
“growth plate” located
between epiphysis and metaphysis. Made
out of hyaline cartilage and works to
lengthen the diaphysis through growth and
ossification .
Short bones
as wide as they are long and
mainly provide support (eg. parts of the
wrist).
Flat bones
mainly provide protection (eg.
skull).
Sesamoid bones
found within tendons to
help muscles pull (eg. kneecap).
irregular bones
irregularly shaped (eg.
pelvis).
Cortical bone
is the dense outer layer of bone that
supports the weight of our bodies. It is composed
of many microstructures: Osteons, Haversian canals, Lamellae, Lacunae, Canaliculi, Volkmann’s canals
Osteons
cortical bone’s functional unit,
composed of tiny multi-layered cylinders.
Also known as haversian systems because
they contain a haversian canal in their center.
Haversian canals
‘tubes’ that contain blood
vessels for nutrient supply.
Lamellae
layers of the osteon.
Lacunae
small spaces between lamellae that
hold bone cells and interconnect through
canaliculi .
Canaliculi
small channels that connect
lacunae and the haversian canal.
Volkmann’s canals
connect Haversian canals
to the periosteum , which provides nutrients.
Cancellous bone
is the spongy inner layer of bone
that soaks up red bone marrow via a web of
trabeculae (connective tissue that supports
cancellous bone).
Bone remodeling
is the process of going back and
forth between the processes of ossification (bone
formation) and resorption (bone loss).
Types of cells
Osteoprogenitors
Osteoblasts
Osteocytes
Osteoclasts
Osteoprogenitors
immature precursor cells
that differentiate into osteoblasts .
Osteoblasts
build bone by secreting
proteins and utilizing blood calcium. They
mature into osteocytes after getting trapped
inside the bone matrix they create.
Osteocytes
live in lacunae in osteons to
maintain bone.
Osteoclasts
eat and resorb bone, bringing
calcium back into the blood. Derived from
monocytes .
Mechanisms involved in bone remodeling
Parathyroid hormone
Vitamin D
Calcitonin
Parathyroid hormone
increases blood calcium levels by stimulating osteoclasts and depressing osteoblasts . Secreted by the
parathyroid gland .
Vitamin D
increases blood calcium levels by raising intestinal calcium absorption. Activated by parathyroid hormone, but provides negative feedback on PTH production.
Calcitonin
decreases blood calcium levels by depressing osteoclasts , allowing osteoblasts to build bone without competition. Secreted by parafollicular cells (C cells) of the thyroid gland .
Osteoid
is the organic component of bone
containing many proteins such as collagen (gives bone tensile strength).
Hydroxyapatite
is the inorganic mineral component of bone that gives the bone density and strength.
Two types of embryonic ossification:
Intramembranous ossification
Endochondral ossification
Intramembranous ossification
bone is created directly within fibrous membranes, mainly for flat bones . Osteoblasts start by secreting osteoid, which hardens and houses osteocytes. Eventually, cortical bone is created.
Endochondral ossification
bone is created indirectly through a cartilage model, mainly for long bones . The cartilage model calcifies during fetal development, creating ossification centers that help form the features of long bones.
Types of connective tissue:
Fibrous connective tissue
Cartilage
Joints
Fibrous connective tissue
has a matrix made up of fibers.
Ex tendons, ligaments, periosteum, endosteum
Tendons
connect muscle to bone.
Ligaments
connect bone to bone.
Periosteum
membrane that covers cortical bone with an outer fibrous layer (vascularized) and an inner/cambium layer (collagen for attachment to cortical bone)
Endosteum
membrane located between cortical and cancellous bone.
Cartilage
is avascular (lacks blood vessels) and is not innervated (as opposed to bone which is highly vascular and innervated).
Chondroblasts
build cartilage by secreting collagen and elastin.
Hyaline cartilage
Fibrous cartilage
Elastic cartilage
Hyaline cartilage
slightly flexible and important in providing support and stability to joints.
Fibrous cartilage
high rigidity and resists tension, found in intervertebral discs and knee meniscus.
Elastic cartilage
highly flexible and found in ears and epiglottis.
Joints
are vascularized and innervated. They
are found between bones. Below are types of joints.
Synarthroses
Amphiarthroses
Diarthroses
Synarthroses joints
dense, fibrous joints that do not move.
Amphiarthroses joints
cartilaginous joints that partially move.
Diarthroses
synovial joints that fully move. Typically contain hyaline cartilage .
