Skeletal system

what are the main components of the skeletal system

bones cartilage and ligaments

what is in each bone

connective tissue blood vessels nerve lymph vessels cartilage connective tissue coverings

hyaline cartilage

found in articular costal respiratory and nasal

elastic cartilage

external ear and epiglottis

fibrocartilage

meniscus between vertebrae

axial skeleton

creates the longitudinal axis of the body houses vital organs

axial skeleton pic

appendicular skeleton

appendages girdles connects to axial much greater mobility

appendicular skeleton pic

long bone

longer than wide humerus femur

short

roughly cube-shaped ex wrist and ankle bone

flat

thin flattened curved ribs sternum cranial bones

irregular

complex shape vertebrae

sesamoid

shaped like a sesame seed at points of high friction patella

sutural

forms between cranial bones vary between individuals

compact bone

forms outer layer of most bones

spongy bone

surround inner cavity

compact bone pic

spongy bone pic

whats the deepest one

diploe

layer of spongy bone in cranial bones

short irregular and flat bone anatomy

sandwich of compact bone - spongy bone - compact bone

epiphysis

end

diaphysis

middle

metaphysis

connects epiphyses to diaphysis

layers of long bones

periosteum

compact

spongy

endosteum

medulllary cavity ( marrow

connective tissue- periosteum loc

covers the outer surface of living bone

periosteum func

isolates and protects bone

supports blood vessels and nerves

connects to other tissues

growth and repair

fibrous layer

interwoven collagen fibers with either deep fascia or bone

osteogenic layer

contains osteogenic cells (bone stem cells)

endosteum location

lines medullary cavity and covers spongy bone surface

endosteum function

reticular connective tissue

contains osteogenic cells that are important for bone growth

skeletal blood supply

extensive network of blood vessels

skeletal innervation

sensory neurons throughout the periosteum

osseous tissue

support connective tissue

contain specialized cells -protein fibers-ground substance

osteogenic cells

stem cells

formed from mesenchyme and give rise to osteoblasts

osteogenic cells processes

osteogenic cells - mitosis - daughter osteogenic cells - differentiation - osteoblasts

osteoblasts

builders and secrete organic components of extracellular matrix

initiate calcification

osteogenic cells

stem cells

osteoblats are

builders

osteocytes are

maintenance crew

osteocytes

mature bone cells

maintain existing matrix in response to bone density needs

act as strain sensors - regulate remolding in response to mech areas

send signals to osteoblasts and osteoclasts via dendritic process

osteoclasts are

destroyers

osteoclats

derived from blood cells

contain resorption bays where they secrete acid and proteolytic enzymes to dissolve matrix (bone respiration)

special about osteoclasts

resorption bay

ruffled border

resorption bay

pit in the compact bone where remodeling is active

ruffled border

exaggerated portion of the osteoclasts membrane where enzymes and acid are released and broken-down minerals are brought into the cells

osseous matrix organic

1/3 of matrix

produce and secretes by osteoblasts

glycosaminoglycans

proteoglycans

collagen fibers

glycosaminoglycans

trap water due to negative charge

glycoproteins

collagen fibers

fibrous protein arranged in helical form

very resistant to pulling forces

provides flexibility and a framework for the deposition of calcium crystals

type 1 collagen fibers

must abundant collagen and also the most abundant protein in the human body

found in the bone as well as fibrous tissue like tendons ligaments and skin

glycine combo with another amino acid to make a collagen polypeptide three collagen polypeptides coil around each other to make tropocollagen

inorganic matrix

other 2/3

crystallizes around collagen fibers

osseous matrix

composite material

combined very strong slightly flexible matrix

composite material

combo of a ceramic + polymer

inorganic on its on strong and inflexible

organic- tough but too flexible

what does bone need for strength

collagen and minerals

osseous matrix special property

the sacrificial bond between collagen molecules

break under mech stress which dissipates the force and reduces the likelihood of fracture

can reform once the stress is removed

rickets

calcium deficiency due to lack of vitamin D

leads to bowed legs

scurvy

problem with collagen synthesis due to vitamin c deficiency

leads to brittle bones that can fracture

compact bone

functional unit bone

concentric lamellae around central canal

made up of osteons

perforating canals connect osteons to each other and medullary cavity

interstitial lamellae

circumferential lamellae

surround entire bone at internal and external surfaces

interstitial lamellae

fill in gaps between osteons

usually remnants of olds osteons

spongy bone made of

spicules and trabeculae

spicules and trabeculae

thin silvers or branching plates

interconnected spaces throughout

same cells as compact

strong but light

compact bone vs spongy bone

compact

-dense

covers bone surface

thick where stress is high

handles stress well in one direction

spongy bone

-lightweight

resists stress from multiple directions

provides support for bone marrow

diaphysis loc

shaft of long bone

diaphysis func

leverage

epiphysis loc

head of long bone

epiphysis func

strengthen joint and surface area for the attachment of ligaments and tendons

articular cartiledge

a thin layer of hyaline cartilage covering the articular surface of the bone as at a synovial joint, serving to reduce friction and ease joint movement

periosteun

a layer of fibrous connective tissue covering surface of a bone

lacuna

A small cavity or depression in a tissue such as bone or cartilage

ossification

the formation of bone

step one of intramembranous ossification

mesenchymal cells line blood cells

osteogenic cells become osteoblasts

osteoblasts start secreting osteoid

second step of IO

calcium salts crystallize on osteoid calcification to spicules

osteoblasts turn into osteocytes when surrounded by matrix

third step of IO

mesenchyme differentiates to periosteum

ossification centers meet and make branching plate called trabeculae

fourth step of IO

osteoblasts in the periosteum crate outside layer of compact bone called diploe structure

continued remodeling of spongy bone by osteoblasts and osteoclasts

calcification

deposition of ca

ossification

replacement of connective tissue by bone tissue

diploe

layer of spongy bone in cranial bones

spongy bone

made of spicules and trabeculae

strong but light

compact bone

mostly osteons and circumferential lamellae

composite material

combo of ceramic and polymer

inorganic on its own

strong but inflexible and would easily shatter

organic on its own

tough but too flexible and wouldn’t resist direct pressure well

what is the special property of the osseous matrix

sacrificial bonds between collagen molecules

rickets

inorganic component deficiency which leads to bowed legs

scurvy

organic component deficiency leads to brittle bones and problems with collagen synthesis

osseous matrix

produced and secreted by osteoblasts

contain glycosaminoglycans

perichondrium

fibrous connective tissue that envelops the surface of hyaline or elastic cartilage

periosteum

layer of connective tissue that covers the surface of a bone

chondrocytes

cartilage cell that was chondroblast enclosed in lacunae in cartilage matrix

endochondral ossification precursor and bones it creates

use hyaline cartilage precursor - most bones below the skull

step one of endochondral ossifciation

mesenchyme turns into hyaline cartilage surrounded by perichondrium

step 2 of endochondral ossifciation

bone growth begins in middle of future diaphysis creating primary ossification center

step 3A of EO

periosteal but invades shaft making primary marrow cavity

step 3B of EO

secondary ossification centers form

step 4 of EO

secondary marrow cavities form in epiphyses

step 5 of eo

further growth due to inc in cartilage first followed by ossification

epiphyseal plate

thin wall or cartilage separating diaphysis and epiphysis

primary ossification

marrow cavity formed

replaces all cartilage with bone

located in diaphysis

occurs before birth

secondary ossification

no marrow cavity

some cartilage is left for the epiphyseal plate and articular cartilage

found in epiphyses

occurs around the time of birth