the skeletal system

ByMuhammad Iqbal Khan

SS BiologyEmail ID: mikhan1313@yahoo.com

0923135448175

The Skeletal System

Function Support

Internal framework of body Ex: Legs support body trunk, rib cage supports chest wall

Protection Protects soft body organs (skull protects brain, ribs protect heart

and lungs, etc) Movement*

Muscles use bones as levers to move body NOT a function skeletal system can do on it’s own

Storage Fat storage

In yellow marrow Mineral storage

Calcium, phosphorus, and others. Blood cell formation

Hematopoeisis Occurs in bone marrow of long bones

Bones206 bones in the adult skeletonTwo types of bone

Compact boneHomogeneous appearanceDense, looks smooth

Spongy boneSmall needle-like piecesLots of open spaces(Looks like a sponge, hence the name)

Bone ClassificationLong Bones

Longer than wideContain shaft with

head at each endMostly compact boneLimbs (not ankle or

wrist bones)Short Bones

Cube-shapedMostly spongy boneWrist and ankle

bonesPatella (kneecap)

Flat BonesThin, flat, usually

curvedTwo layers of

compact bone with spongy bone in between

Skull, ribs, breastbone

Irregular BonesDon’t fit into the

other categoriesVertebrae, hip bones

Bone Classification

Long Bone AnatomyDiaphysis

ShaftMade of compact

boneEpiphyses

Ends of long boneMade of compact

bone surrounding spongy bone

Covered with articular cartilageSmooth, glassy,

decreases friction at joints

Long Bone AnatomyEpiphyseal Line

Line of bone tissue that looks different from rest of bone

Remnant of epiphyseal plateHyaline cartilageCauses long bones to

grow lengthwise

Long Bone AnatomyPeriosteum

Outer covering of shaft

Like “skin” on chicken bone

Sharpey’s fibersAttach periosteum

to boneArteries

Supply nutrients to bone cells

Long Bone AnatomyMedullary Cavity

In shaftContains yellow

marrow (adipose) in adults

Contains red marrow in infants (for blood cell formation)

Microscopic Anatomy of BoneOsteon (Haversian system)

A “unit” of boneCentral (Haversian) canal

Opening in center of osteonContains blood vessels

Perforating (Volkman’s) canalPerpendicular to central canalContains blood vessels and nerves

Microscopic Anatomy of Bone

Microscopic Anatomy of BoneLacunae

Cavities that contain osteocytes (bone cells)

Arranged in concentric rings (like tree rings)

LamellaeRings around the

central canalWhere the lacunae

can be found

Microscopic Anatomy of BoneCanaliculi

Tiny canalsRadiate from

central canal to lacunae

Transport nutrients to bone cells

Other FactsBone is one of the hardest parts of the

bodyVery lightweightCan resist tension

Calcium salts make it hardCollagen fibers make it strong and flexible

Bone FormationIn embryos…

Skeleton made of hyaline cartilageGets replaced by bone with age

Cartilage remains in a few places…Bridge of noseParts of ribsJoints

Bone GrowthEpiphyseal plates allow for growth of long bone

during childhoodNew cartilage is continuously formedOlder cartilage becomes ossifiedCartilage is broken downBone replaces cartilageBones remodeled, lengthened until growth

stopsBones change shape somewhatBones grow in width

Long Bone Growth

Long Bone Growth

Types of Bone CellsOsteocyte

Mature bone cellOsteoblast

“Bone builders”Osteoclast

“Bone destroyers”Break down bone matrix to remodel and/or

release calcium

Bone RemodelingBone remodeling is done by osteoblasts and

osteoclastsEssential for bones to keep normal proportions

and strengthBones get larger/thicker when…

Large muscles are attached to them Need more bone to attach the large muscle to

Bones get smaller/weaker when…Physical inactivity

Non-use of musclesatrophySmall muscles don’t need large bones to attach to

Bones remodeled to become smaller

FracturesA break in a boneTypes of Fractures

Simple (closed) fractureBone breaks cleanly, does not penetrate skin

Compound (open) FractureWhen bone ends penetrate through skin

Treated by reduction and immobilizationRealignment of bone ends

Common Fractures

Bone RepairHematoma forms

Blood vessels rupture when bone breaks

Blood filled swellingCells without

nutrients dieFibrocartilage callus

formsMade of connective

tissueSplints the breakPhagocytes dispose

of dead tissue

Bony callus formsOsteoblasts/clasts

move in, create callus of spongy bone

RemodelingOsteoblasts/clasts

remodel in response to stress on the boneHelps strengthen boneCreates a permanent

“patch” at the siteOften, a healed fracture

can be stronger than the rest of the bone

Bone Repair

Axial SkeletonMakes up longitudinal part of the bodyThree parts

SkullVertebral columnBony thorax

**Note: notes on specific bones are not included. Make sure you are using your textbook to help identify shapes/functions of bones!!

Axial Skeleton **Shown in green

SkullFormed by two sets of bones

CraniumEncloses/protects brain

Facial bonesHolds eyes forward (anterior position)Allow facial muscles to show feelings

SuturesInterlocking, immovable joints holding most

skullbones togetherMandible-only freely movable bone in skull

Skull

Skull

Paranasal SinusesHollow portions of bone around nasal cavity

Named for bones they are found inLighten skullAmplify sounds when speaking/ give resonance

Fetal SkullLarge in comparison

to body length of infant

Contains fontanellesSoft fibrous

membranes connecting cranial bones “Soft Spots”Usually convert to

bone around 24 months after birth

The Vertebral ColumnVertebrae named for

their location7 cervical vertebrae

C1 = Atlas C2 = Axis

12 thoracic vertebrae5 lumbar vertebraeSacrum

5 fused vertebraeCoccyx

4 fused vertebrae

Vertebrae separated by fibrocartilage discsCushions/absorbs shock

Vertebrae Structure

Regional Characteristics

Regional Characteristics

Bony Thorax Forms a cage to protect organs

Three partsSternum

Flat bone3 fused bones

Manubrium Body Xyphoid process

Attached to first 7 pr of ribs

Rib Cage12 pairs

True Ribs= 7 pr False Ribs = 5 pr Floating Ribs = 2 pr

Thoracic vertebrae

Appendicular SkeletonLimbs

(appendages)Pectoral girdlePelvic girdle

**shown in yellow

Pectoral Girdle (shoulder)Two bones

Clavicle-collarboneScapula-shoulder

blade

Upper Limb (arm)Arm bone-

humerusForearm bones-

Radius (thumb side)

UlnaHand bones

Carpals-wristMetacarpals-palmPhalanges-fingers

Pelvic Girdle (hip bones)Three pairs of

fused bonesIliumIschiumPubic bone

Carries total weight of upper body

ProtectsReproductive

organsBladderPart of large

intestine

Gender Differences in PelvisFemale inlet

larger/more circularFemale pelvis is

shallower, bones lighter/thinner

Female hip bones flare wider

Female sacrum is shorter/less curved

Female pubic arch is more rounded/angle is greater

Lower Limb (leg)Thigh bone-femurTwo leg bones

Tibia (larger, medial bone)

Fibula (smaller, lateral bone)

FootTarsals-ankleMetatarsals-solePhalanges-toes

JointsArticulations of

bonesFunctions

Hold bones togetherMobility

Classified by structure/function

**we’ll use structural classification

Fibrous jointsImmovable

EX: sutures of skull

Cartilaginous jointsImmovable OR

slightly movableEX:Pubic symphysis

and Vertebrae

Synovial jointsFreely movable**Be familiar with types of

synovial joints (illustrations to follow)

Synovial JointsArticulating bones

separated by joint cavityArticular cartilage

covers bone endsJoint surfaces enclosed

by fibrous capsuleCavity contains

synovial fluidLigaments help

reinforce the joint

Associated Joint StructuresBursae

Flat fibrous sacs Lined with synovial

membrane Contains synovial fluid Common where

ligaments, muscles, skin, tendons rub together

Tendon sheath Elongated bursa

wrapping around a tendon that deals with lots of friction Like a bun around hot dog

Synovial Joints

Types of Synovial Joints by Shape

Types of Synovial Joints by Shape