Chapter 5: skeletal system Flashcards
How many bones are in the body?
206
There are 2 division to the skeletal system. What are they? briefly describe them
axial: head and center of body
appendicular: movement (limbs and pelvis)
What are the two types of bone tissue?
compact: dense smooth bone
spongy: bone with open spaces within
What are the four components of the skeletal system?
bone
cartilage
ligaments
tendons
What are the five functions of the skeletal system?
Protection Support (rigid structure) Movement (bones act as levers) Storage (Ca, P, and fat) Blood cell production
cartilage consists of what two things?
cells and an extracellular matrix
what cells are found in cartilage and where are they located?
Chondrocytes and they are found in compartments called lacunae
what are the two components to the extracellular matrix of cartilage?
Collagen/elastic fibers and a ground substance made of chondrotin sulfates
does cartilage have arteries, veins, or lymphocytes? what does this mean?
no; it means it heals slowly
what are the three types of cartilage?
hyaline
elastic
fibrocartilage
describe hyaline cartilage and give its structure and location
Most common but weakest
Structure: chondrocytes, chondrotin sulfate, some collagen
Location: embryonic skeleton, articular surfaces, respiratory passages, nasal septum, between ribs and sternum
Give the structure and location of elastic cartilage
Structure: chondrocytes, chondrotin sulfate, densely packed elastic fibers
Location: auricle, tip and lateral walls of nose, epiglottis
-flexible
Give the structure and location of fibrocartilage
Structure: chondrocytes, chondrotin sulfate, densely packed collagen fibers
Location: intervertebral discs, public symphysis, articular cartilage in knee
describe the perichondrium
fibrous connective tissue that surrounds the cartilage, It provides support and protection and new chondrocytes
where is the perichondrium located?
absent?
Located: hyaline cartilage and elastic cartilage
Absent: articular surface and fibrocartilage
describe the inner and outer layers of the perichondrium
inner: for growth and maintenance
outer: binds cartilage to adjacent tissues; provides protection and support
describe appositional growth
- starts in the perichondrium
- Mesenchymal (stem) cells at periphery form in inner layer of perichondrium
- Mesenchyme move toward matrix to become chondrogenic cells
- Chondrogenic cells aggregate and become chondroblasts
- Chondroblasts secrete matrix –> forces cells apart
- Chondroblasts become enclosed in matrix and become chondrocytes
describe interstitial growth
- Chondrocytes are enclosed in matrix and divide
- As they move apart, matrix forms between them
- Growth of cartilage from within
what are three general traits of osseous tissue?
- supportive connective tissue
- contains specialized cells
- solid extracelliular matrix
what is found in the solid extracellular matrix of osseous tissue?
osteoid: organic portion, protein fibers
ground substance: Ca salts water
What do Osteoprogenitor cells do?
play role in initial bone growth and fracture repair
describe osteoblasts
- derived from osteogenic cells
- secrete osteoid
- common in growing bone
- Predecessor to osteocytes
- Increased osteoblast activity = stronger bone
describe osteocytes
- mature cells
- exist within matrix
- maintain Ca and PO4 homeostasis
- found in spaces called lacunae
describe osteoclasts
involved in osteolysis
Break down of bone
Increase osteoclast activity weaker bone
Very large
Formed from the fusion of many white blood stem cell
look at slide 20
:)
Compact bone is arranged in______
Spongy bone is arranged in______
osteons
trabeculae
Osteocytes communicate through _______ that radiate outward and connect one cell to the next cell
canaliculi
what are osteons?
units of compact bone
___________ of matrix surrounding a ______________
concentric lamellae; central (Haversian) canal
do osteons contain blood vessels and nerves?
yes
Osteons connected to each other by
perforating canals
what are three characteristics of lamellae?
Concentric
Interstitial
Circumferential
**look at slide 24
What does spongy bone contain?
what does it not contain?
contains: Trabeculae osteocytes in lacunae canaliculi matrix does not contain: osteons central canal
what is trabeculae?
Latticework of thin plates of bone oriented along lines of stress
the spaces in trabeculae are filled with what?
red marrow (where blood cells develop
where is trabeculae found?
Found in ends of long bones and inside flat bones.
what does trabeculae do?
Lightens the bone, allows for movement
what does the periosteum do?
it encloses bone
where is the periosteum absent?
Absent at site of attachment of muscles, tendons & ligaments; surfaces covered by articular cartilage
the periosteum has two layers, an inner and an outer layer. What does each layer do?
Outer fibrous: gives rise to collagen
Inner: for growth or new cells & maintenance
describe the edosteum. what cells are located here?
1 cell layer
Covers surfaces of spongy bone & medullary cavity
Cell types: Osteogenic, Osteoblasts, Osteoclasts
for long bones the shaft is known as the…
diaphysis
for long bones the epiphysis is …
one end of a long bone
for long bones the growth plate region is known as the what?
metaphysis
for long bones the articular cartilage is located….
over the joint surfaces…acts as friction and shock absorder
for long bones the medullary cavity is the…..
marrow cavity
describe yellow marrow
Areolar and adipose CT
In medullary cavity of long bones
Energy storage
Absent in infants
describe red marrow
where is it located?
Areolar and myeloid tissue Produces all types of blood cells Locations: Medullary cavities of infants Spongy bone in adults
what are some of the arteries in the bone?
periosteal arteries
nutrient arteries
Metaphyseal & epiphyseal arteris
what do the periosteal arteries do?
supply the periosteum
where do the nutrient arteries enter the bone? what do they do?
enter through nutrient foramen
supplies compact bone of diaphysis & yellow marrow
what do the metaphyseal and epiphyseal arteries do?
supply red marrow & bone tissue of epiphyses and metaphyses
true or false:
ALL the arteries described that are located in bone have corresponding veins
true
what is ossification?
replacing CT with bone
what is Intramembranous ossification?
mesenchymal cells–>spongy bone
what is Endochondral ossification?
hyaline cartilage ->spongy bone
when does Intramembranous Ossification begin?
end?
week 8 in the embryo and ends in week 15
what does intramembranous ossification form?
Cranial flat bones Facial bones Dentary bones Clavicle Sesmoid bones
what is the Primary ossification center?
location where bone growth begins
what is important about intramembranous ossification?
- Mesenchymal cells arrange around BVs
- bone morphogenic proteins released
- mesenchymal cells become recruited, divide, and differentiate into osteoblasts
in intramembranous ossification, osteoblasts secrete…..
osteoid
when osteoblasts become isolated in intramembranous ossification they become what? what do they do?
osteocytes
Produce spicules of bone that interconnect
Look at slide 36
:)
what replaces what in Endochondral Ossification
bone replaces the cartilage model
when does Endochondral Ossification begin? end?
begins at week 7 in the embryo and lasts until adulthood
what does endochondral ossification form?
Long bones
Most short bones
Non-cranial irregular & flat bones
Middle ear ossicles
describe what happens in endochondral ossification
where does bone growth elongation occur?
Occurs at epiphyseal plate
when does growth in length end?
Growth in length continues until 2 ossification centers meet
Relative thickness of epiphyseal plate (does/does not) change until growth almost complete; then:
does not; cartilage depleted & epiphyseal plate narrows to epiphyseal line
describe appositional bone growth
- Compact bone deposited beneath periostium
- Bone thickens
- Bone remodeling occurs throughout life due to osteoclasts & osteoblasts
does bone remodeling ever end? explain
bone modeling never ends, it is ongoing since osteoclasts carve out small tunnels and osteoblasts rebuild osteons. this means there is continual redistribution of bone matrix along lines of mechanical stress
_____% of compact bone, ___% of spongy bone remodeled per year
4%=compact
20%=spongy
distal femur is fully remodeled every __ months
4
what are the two types of breaks? describe them
Simple: break that does not penetrate skin
Compound: broken bone penetrates through skin
how are fractures treated?
reduction & immobilization
what are the four steps in bone repair?
fracture hematoma
fibrocartilage callus
Bony callus
Remodel tissue
within hours of an injury, a ________ forms
what is this and why does this happen?
- fracture hematoma
- it is a mass of blood
- Swelling and inflammation occur in response to dead bone cells
in a fracture hematoma, _________ and ______ eliminate dead cells/broken matrix
phagocytes and osteoclasts
A fibrocartilaginous callus consists of …..
a mass bridging the broken ends of the bone.
what do fibroblasts in the perisoteum produce?
collagen
in Fibrocartilaginous callus formation, _________ cells differentiate into _______ cells. This results in______
periosteum, chondrocytes, fibrocartilage
the formation of the bony callus occurs as the ________________is converted to _________________
fibrocartilaginous callus, spongy bone trabeculae.
The bony callus lasts about how long?
3-4 months
what happens in bone remodeling?
Remaining dead bone fragments are resorbed, and compact bone replaces spongy bone
if a bone fracture heals properly, can you tell later?
nope its virtually undetectable!
what are four factors that effect the growth and repair of bones?
Nutrition: Vit. D
Sunlight
Hormones: PTH, calcitonin, GH, thyroid hormone, sex hormones
Physical stress
what is osteoporosis?
abnormal reduction of bone mass
what are reasons for osteoporosis?
Loss of estrogen at menopause
Deficiency of minerals in youth
Imbalance in activity between osteoblasts & osteoclasts
describe Fibrodysplasia Ossificans Progressiva
Fibrous tissue becomes ossified
Genetic disorder
Injury results in inappropriate bone formation
Early adulthood: “freezing” of major joints
Early 20’s: confined to wheelchair
Starvation & pneumonia can result
No treatment
