ch6 Flashcards
Main functions of the skeleton
- Supports the body
- Organ protection
- Produces blood cells
- Stores minerals and fat
- Permits flexible body movement
what are the main components of the skeletal system
bones, cartillage, tendons and ligaments
ligaments
strong bands of fibrous connective tissue that hold bones together
what cartilage is associated with more with bone?
hylaine cartilage
how does a chondrocyte form
hyaline cartilage chondroblasts produce a matrix surrounding themselves. Once the matrix is surrounded the chondroblasts, the cells differentiate into chondrocytes
perichondrium
double layer of protective connective irregular tissue that surrounds cartilage with fibroblasts
contains contains blood vessels and nerves.
articular cartilage
hyaline cartilage that covers ends of bones where they come together to form joints, has no pericardium, blood vessels, or nerves.
appositional growth
chondroblasts in the perichondrium add new cartilage to the outside edge of the existing cartilage. the chondroblats lay down a new matrix and add new chondrocytes to the outside of the tissue
interstitial growth
chondrocytes in the center of the tissue divide and add more matrix in-between the existing cells.
by weight how much of bone matrix is organic and inorgnic
35% organic and 65% inorganic
what is the inorganic portion of bone
hydroxy apeptite, calcium phosphate crystal
what are the components for the major functional characteristics of bone
collagen and mineral components
what organelles are important in osteoblasts, and what do they do
ER and Ribosomes
they form collagen and proteoglycans which are packaged into vessicels from the golgi and released by exocytosis
how does ossification occur
appositionaly on the surface of prexisiting cartilage or bone
osteocyte
osteoblast the is completely surrounded by the matrix
mostly inactive
lacunae
spaces without the matrix but occupied by the osteocyte cell bodies
canaliculi
spaces that are occupied by the osteocyte cell extensions ]
what do osteoclasts do?
reabsorb, breakdown, of bone that mobilizes crucial Ca + and phosphate ions for use in many metablic processes
osteochondrial progenitor cells
are stem cells that can become osteoblasts or chondroblasts
where are osteochondrial progenitor cells located?
inner layer of the perichondrium and in layers of the CT that cover the bone
what do the collagen fibers do to the bone matrix
lend flexible strength to the matrix
woven bone
weak and new bone
randomly oriented fibers in many directions
bone remodeling
process of removing old bone and
lamellar bone
is mature bone that is organized into thin, concentric sheets or layers
compact bone has more ____ and less ____
matrix and is denser with fewer pores than spongy bone
concentric lamellae
circular layers of bone matrix that surround the central canal
circumferential lamellae
on the outer surface of compact bone
thin plates that extend around the bones
interstitial lamellae
between ostedons
remnants of concentric or circumferential lamellae that were partially removed during bone remodeling
how do osteocytes recieve and eliminate waste products
through the canal system within compact bone
flat bones are
relatively thin, flattened, and usually curved
examples of irregular bones
vertebrae and facial bones
diaphysis
SHAFT
primarily made of compact bone but some spongy
where is the primary ossification center
diaphysis
epiphysis
part of the long bone that develops from a center of ossification distinct from the diaphysis
one at the end of each long bone
epiphyseal plate
GROWTH PLATE
located between the epiphysis and diaphysis
growth in length
epiphyseal line
when bone stops growing in length, the epiphyseal pate turn in the epiphyseal line
medullary cavity
the hollow center of the diaphysis
the cavities of spongy bone and medullary cavity are filled with
marrow
red marrow
site of blood cell formation
yellow marrow
mostly adipose tissue
completely replaces the red marrow in the long bones of the limbs, except for some red marrow in the proximal part of the arm bones and thighbones
marrow from fetus to adult
in fetus, the spaces within bones are filled with red marrow,
red marrow begins to turns into yellow marrow just before birth and well into adulthood.
periosteum
a CT membrane covering the outer surface of a bone
what is the outer surface of bone
fibrous layer is dense irregular collagenous CT that contains blood vessels and nerves
what is the inner layer of bone
a single layer with osteoclasts, blasts and oseteochondrial progenitor cells
perforating fibers
bundles of collagen fibers that streghten the attachment of the tendons or ligaments to the bone
endosteum
single cell layers of connective tissue that line the internal surfaces of all cavities within bones such as the medullary cavity of the diaphysis and the smaller cavities in spongy and compact bone
includes osteoclasts, blasts and oseteochondrial progenitor cells
sinuses
Air filled spaces lined by mucus membranes
intramembranous ossification
bone forms form pre-exisiting CT membranes
endochondralal ossification
bone forms fome a preexisting cartilage model
center of ossification
locations in the membrane where ossification begins
have the oldest bone
fontanels
soft spots
developing skull bones that have not yet been ossified
when does the formation of cartilage begin
the end of the 4th week of embryonic dev
endochondrial ossification begins
8th week of embryonic dev
but other cartilage may not start until 18-20 years
bone collar
is formed when osteoblasts produce compact bone on the surface of the cartillage model
secondary ossification centers
are created in the epiphysis by osteoblasts that migrate into the epiphysis
primary ossification centers appear
during early fetal development
secondary ossification centers appear
in the proximal epiphysis of the femur, humerus, and tibia about 1 month after birth
when does the last secondary ossification center appear
in the medial epiphysis of the clavicle
18-20 years
metabolic disorders that affect the ___ affects bone growth
rate of cell proliferation or the production of collagen and the other matrix components
vitamin d
necessary for normal calcium absorbtion
rate of absorption increases when the skin is exposed to the sun
vitamin d can be
synthesized or ingested by the body
rickets
not enough vitamin d in children
reduced materialization of the bone matrix
osteomalacia
a softening f the bones due to calcium depletion
can cause adult rickets
vitamin c
neccessay for callogen synthesis by osteoblasts
vitamin c dificiency
results in bones and cartilage with fewer collagen fibers bc collagen synthesis is impaired
retard growth in children
scurcy for both adults and children
scurvy
marked by ulceration and hemorrhage in almost any area of the body because normal collagen sysnthesis is not occurring in CTs
in extreme cases, teeth fall out because of the ligaments that hold them bread
growth hormone
from the anterior pituitary increases general tissue growth including overall bone growth, by stimulating interstitial cartilage growth and appositional bone growth
thyroid hormone
necessary for normal growth of all tissue including cartilage
reproductiv hormone
duruing puberty
stimulate ossification of epiphyseal plates and thus the cessation of growth
why do females stop growing earlier than males
estrogen vauses quicker closure of the epiphyseal plate than testosterone
bone remodeling
osteoclats remove old bone and osteoblasts deposit new bone
converts woven bone to lamellar bone
bone remodeling is involved in what processes
bone growth, changes in bone shape, adjustments of the bone to stress, bone repair, and calcium and ion regulation in the body
what is the structure of long bone
hollow cylinder with with medullary cavity in the center
what are the mechanic advantages of the structure of long bone
hollow cylinder is lighter than a solid rod
hollow cylinder with the same height, weight, composition as a solid rod but with greater diameter, can support much more weight without bending
basic multicellular unit BMU
a temporary assembly of osteoclasts and osteoblasts that travels through of across the surface of bone
what is the average lifespan of a BMU
6 months
mechanical stress applied to bone
increases osteoblast activity in bone tissue
pressure in bone
causes an electrical change that increases the activity of ostoblasts
hematoma
is a localized mass of blood released from blood vessels but confined within an organ or a space.
callus
mass of tissue that forms at a fracture site and onnects the broken ends of the bone
internal callus
forms between then ends of broken bone, as well as in the marrow cavity if the fracture occurs in the disphysis id a long bone
exterenal callus
forms a collar around the opposing ends of the bone fragments.
what determines Ca levels
bone
major storage of ca
calcium ions move
into the bone as osteoblats build new bone, and move out as osteoclasts break down bone.
how is cacium maintained by homeostasis
When blood Ca k=levels are low, osteoclastss activity increase bc osteoclasts release more Ca from bone into the blood than osteoblasts remove from the blood to make new bone
calcium homeostasis is controlled by what hormones
parathyroid H, vitamin D, and calcitonin from C cells in the thyroid gland
PTH
is the major regulator of blood Ca levels
PTH is secreted from the parathyroid glands
when blood Ca levels are too low, stimulates an increase in the number of osteoclasts, which break down the bone and elevate blood Ca levels.
Which of these connective tissue types has proteoglycans in its matrix?
cartilage
Cartilage
often occurs in thin plates or sheets.
receives nutrients and oxygen by diffusion.
Which portion of a long bone stores yellow marrow in adults?
the medullary cavity
Which of these substances is present in the largest quantity in bone?
A) collagen B) hydroxyapatite C) proteoglycan aggregates D) lacunae cartilage
B Hydroxyapeptie
whats structures are found in osteons
A) concentric lamella
B) interstitial lamella
C) circumferential lamella
D) periosteum
In endochondral ossification, the perichondrium that surrounded the hyaline cartilage becomes
periosteum
Growth in the length of a long bone stops when
appositional growth at the periosteum stops
Which type of bone growth is responsible for an increase in the diameter of bones?
appositional growth
PTH is secreted from the __________ , whereas calcitonin is secreted from the __________ .
parathyroid gland, thyroid gland
Parathyroid hormone causes
increased bone breakdown.
