Lecture 3 - Intro to the Skeletal System Flashcards
what are the five main functions of bone tissue?
- supports and protects soft tissue
- supports and generates the shape of the body
- provides attachment for muscles, tendons, and ligaments
- dynamic mineral storage
- makes bone marrow
connective tissue in medullary cavity where blood formation occurs
red marrow
connective tissue in medullary cavity where adipose is stored
yellow marrow
bone is composed of:
calcium phosphate (minerals = inorganic) and type I collagen (protein = organic)
bone cells are embedded in a:
mineralized matrix
bone is covered by other connective tissue such as:
periosteum and endosteum
bone remodels itself under the influence of:
forces
bone is anisotropic, which means:
it has different strength depending on its orientation
how are bones classified?
by location and shape
what are the two main types of bone?
spongy (cancellous/trabecular) bone and compact (cortical) bone
- open network of struts surrounded by blood
- shape and direction depend on external forces
- 20% of bone in all the body, 80% of bone remodelling (due to assoc. with vasculature)
these are all characteristics of what type of bone?
spongy/trabecular bone
- relatively dense and solid (lamellae = layers)
- thickness and density also depends on external forces
- 80% of bone in all the body, 20% of bone remodelling
these are all characteristics of what type of bone?
compact/cortical bone
epiphysis
the end of a bone
diaphysis
the shaft of a bone
highly vascularized connective tissue and contain mesenchymal stem cells
endosteum and periosteum
contain many sensory nerves (where pain is felt)
periosteum
where does appositional growth occur?
periosteum and endosteum
contains red marrow and yellow marrow
medullary cavity
what is articular cartilage?
hyaline-like cartilage at the ends of bone, remnants of bone growth
what are osteoblasts?
immature bone cell which secretes matrix
what is the function of osteoblasts?
bone forming
what are osteocytes?
mature bone cells that live in the lacunas
what is the function of osteocytes?
to maintain the matrix
canals that allow osteocytes to communicate
canaliculi
what are osteoclasts?
bone cells which come from blood which reabsorb the matrix
what is the function of osteoclasts?
bone reabsorbing
secretes acidic substance which break down bone
osteoclasts
bone cells which come from mesenchymal cells
osteoblasts and osteoclasts (ossified version of osteoblasts)
functional unit of the the bone which are oriented in the line of stress
osteons
organized in concentric layers around a central canal containing blood vessels and nerves supplying the osteon
osteocytes
transmits blood vessels from the periosteum into the bone and communicates with the Haversian canal
perforating (transverse) canals
bone remodelling is a dynamic process that allows:
- bone renewal and microcrack repair
- liberation of bone minerals
- fracture healing
what type of bone development is responsible for bone formed from the mineralization of mesenchymal tissue?
intramembranous ossification
why do the circles of the osteons have alternating directions?
to resist forces
what bones are formed by intramembranous ossification?
the clavicle, mandible, skull, and facial bones
type of bone development where the formed bone replaces hyaline cartilage
endochondral ossification
what bones are formed by endochondral ossification?
limb bones, vertebral coloumn, thoracic cage, and pelvic girdle
what are the four main steps of intramembranous growth?
1) formation of an ossification centre
2) osteoid calcifies and osteoblasts become osteoclasts; new osteoblasts are produced and move outward
3) developing bone forms trabeculae and blood vessels supply the new bone
4) mesenchymal cells condense around outside of bone to form periosteum
how is the ossification centre formed?
chemical messages to mesenchymal cells to crowd together –> cells differentiate into osteoblasts –> aggregation of osteoblasts secreting ECM
what are the main functions of cartilage tissue?
- supports and preserves soft tissues
- provides a smooth, frictionless, shock absorbing surface at articulations (joints)
- provide a model for the formation of the majority of the bones in the body
how does cartilage resist compression?
contains a high amount of ground substance
does cartilage have its own blood supply?
no, it is avascular and needs another connective tissue close by to survive
most cartilage is covered by:
a connective tissue sheath (perichondrium)
what are the three main types of cartilage?
- hyaline cartilage
- elastic cartilage
- fibrocartilage
type of cartilage which provides support, flexibility and resilience and is found in growth plates, costal cartilage, most respiratory cartilage, nasal cartilage, and articular cartilage
hyaline cartilage
type of cartilage which maintains the shape of a structure while allowing flexibility and is found in the epiglottis and external ear
elastic cartilage
type of cartilage which is highly compressed with great tensile strength and is found in the menisci of synovial joints (knee), intervertebral discs, pubic symphysis, and temporomandibular joint (TMJ)
fibrocartilage
what are the steps of endochondral growth (pre-natal)?
1) mesenchymal cells condense to form outer covering (perichondrum)
2) large chondrocytes secrete an attractant for blood vessels and then undergo apoptosis
3) invading blood vessels stimulate cells which differentiate into osteoblasts and osteoclasts
what are the steps of endochondral growth (post-natal)?
1) secondary ossification centres appear in the epiphyses
2) epiphyseal cartilage plate is formed and remains between the epiphysis and diaphysis
does articular cartilage heal well?
no
as you age, articular cartilage will be replaced by:
bone
is it possible for bones to grow in length when the bone plates close?
no
after growth plates close, bones can grow appositionally in response to:
stimuli like muscular activity and bone damage
what are the three main factors that impact bone modelling and remodelling?
- minerals
- vitamin A and C
- hormones
what is appositional bone growth?
a change in the shape/diameter of the bone
what are the four main steps of bone remodelling and repair?
1) fracture hematoma: rupture of blood => hemorrhage
2) fibrocartilaginous callus: invasion of macrophages
3) bony callus: healthy blood vessels are produced, bringing in osteogenic cells to form osteoblasts, spongy bone laid down, cartilage replaced by bone
4) bone remodelling: osteoclast activity increases, spongy bone replaced by cortical bone
why is the fracture hematoma necessary?
after 6-8 hours, the hematoma causes blood vessels to constrict to stop future bleeding
what is the fibrocartilaginous callus made of?
cartilage
what is the purpose of the fibrocartilaginous callus?
bridges the gap between the broken pieces of bone (immobilization)
joints can be classified in two ways:
- the connective tissue that binds the bones together and the potenial space between them
- functionality
what are fibrous joints?
type of joint where bones are held together by fibrous connective tissue
where are fibrous joints found?
cranial sutures, gomphosis, interosseous membrane
what are cartilaginous joints?
type of joint where bones are joined by cartilage
what are the two types of cartilaginous joints?
- primary/synchondrosis
- secondary/symphysis
where are synchondrosis cartilaginous joints found?
cartilage of growth plates
where are symphisis cartilaginous joints found?
intervertebral discs, pubic symphysis
what are synovial joints?
fluid-filled cavity that separates cartilage-covered joint surfaces
the shape of the articular surfaces of a synovial joint dictates its:
range of motion
