The Skeletal System The Skeletal System (Bones and Joints)(Bones and Joints)

Anatomy & Physiology IChapter 7

Bone as a TissueBone as a Tissueosteology – the study of bone

skeletal system - composed of bones, joints, cartilages, and ligaments◦form strong flexible framework of the

body◦cartilage – forerunner of most bones

covers many joint surfaces of mature bone

ligaments – hold bones together at the joints

tendons – attach muscle to bone

7-3

Functions of the SkeletonFunctions of the Skeletonsupport – hold the body up, supports

muscles, mandible and maxilla support teeth

protection – brain, spinal cord, heart, lungs

movement – limb movements, breathing, action of muscle on bone

electrolyte balance – calcium and phosphate ions

acid-base balance – buffers blood against excessive pH changes

blood formation – red bone marrow is the chief producer of blood cells

7-4

Bones and Osseous TissueBones and Osseous Tissue

bone (osseous tissue) - connective tissue with the matrix hardened by calcium phosphate and other minerals

mineralization or calcification – the hardening process of bone

individual bones consist of bone tissue, bone marrow, cartilage, adipose tissue, nervous tissue, and fibrous connective tissue

continually remodels itself and interacts physiologically with all of the other organ systems of the body

permeated with nerves and blood vessels, which attests to its sensitivity and metabolic activity

The Matrix of BoneThe Matrix of Bone matrix of osseous tissue is, by dry weight, about one-

third organic and two-thirds inorganic matter organic matter – synthesized by osteoblasts

◦ collagen, carbohydrate – protein complexes, such as proteoglycans and glycoproteins

inorganic matter◦ 85% calcium phosphate (hydroxyapatite)◦ 10% calcium carbonate◦ other minerals (fluoride, sodium, potassium, magnesium)

bone is a composite – combination of two basic structural materials, a ceramic and a polymer◦ combines optimal mechanical properties of each component◦ bone combines the polymer, collagen, with the ceramic,

hydroxyapatite and other minerals◦ ceramic portion allows the bone to support the body weight,

and protein portion gives bone some degree of flexibility rickets – soft bones due to deficiency of calcium salts osteogenesis imperfecta or brittle bone disease –

excessively brittle bones due to lack of protein, collagen

Bone StructureBone StructureTypes of osseous (bone) tissueCompact bone - Dense outer layerSpongy (cancellous) bone - Honeycomb of

trabeculae Bone marrow

◦ Red marrow

◦ Yellow marrowBone membranes

◦ Periosteum

◦ Endosteum

Compactbone

Trabeculae

Spongy bone(diploë)

Structure of a Long BoneStructure of a Long BoneDiaphysis (shaft)

◦Compact bone collar surrounds medullary (marrow) cavity

◦Medullary cavity in adults contains fat (yellow marrow)

Epiphyses◦Expanded ends ◦Spongy bone interior ◦Epiphyseal line (remnant of

growth plate) ◦Articular (hyaline) cartilage

on joint surfaces Living Dried

Marrow cavity

Periosteum

Nutrient foramen

Compact bone

Spongy bone

Epiphysis

Epiphysis

Diaphysis

Articularcartilage

Epiphysealline

Red bonemarrow

Yellow bone marrow

Epiphysealline

Articularcartilage

Proximalepiphysis

Epiphysealline

Articularcartilage

Periosteum

Spongy bone

Compact bone

Medullarycavity (lined

by endosteum)

Compact bone

Diaphysis

Distalepiphysis

Structure of a Long BoneStructure of a Long Bone

Membranes of BoneMembranes of BonePeriosteum

◦ Outer fibrous layer

◦ Inner osteogenic layer

Osteoblasts (bone-forming cells)

Osteoclasts (bone-destroying cells)

Osteogenic cells (stem cells)

◦ Nerve fibers, nutrient blood vessels, and lymphatic vessels enter the bone via nutrient foramina

◦ Secured to underlying bone by Sharpey’s fibers

Membranes of BoneMembranes of BoneEndosteum

◦Delicate membrane on internal surfaces of bone

◦Also contains osteoblasts and osteoclasts

Yellowbone marrow

Endosteum

Compact bone

Periosteum

Perforating(Sharpey’s) fibers

Nutrientarteries

Structure of Short, Irregular, Structure of Short, Irregular, and Flat Bonesand Flat Bones

Periosteum-covered compact bone on the outside

Endosteum-covered spongy bone within

Spongy bone called diploë in flat bones

Bone marrow between the trabeculae

Compactbone

Trabeculae

Spongy bone(diploë)

Bone MarrowBone Marrowbone marrow – general term for soft tissue

that occupies the marrow cavity of a long bone and small spaces amid the trabeculae of spongy bone

red marrow (myeloid tissue)◦ in nearly every bone in a child

◦ hemopoietic tissue - produces blood cells and is composed of multiple tissues in a delicate, but intricate arrangement that is an organ to itself

◦ in adults, found in skull, vertebrae, ribs, sternum, part of pelvic girdle, and proximal heads of humerus and femur

yellow marrow found in adults◦ most red marrow turns into fatty yellow

marrow◦ no longer produces blood

Location of Hematopoietic Location of Hematopoietic Tissue (Red Marrow)Tissue (Red Marrow)Red marrow cavities of adults

◦Trabecular cavities of the heads of the femur and humerus

◦Trabecular cavities of the diploë of flat bones

Red marrow of newborn infants◦Medullary cavities and all spaces in

spongy bone

Microscopic Anatomy of Microscopic Anatomy of BoneBoneCells of bones

◦Osteogenic (osteoprogenitor) cells – give rise to osteoblasts Stem cells in periosteum, endosteum and

central canals ◦Osteoblasts – manufacture bone matrix

Bone-forming cells◦Osteocytes – maintain and repair existing

bone matrix Mature bone cells

◦Osteoclasts – breakdown (resorb) bone matrix Cells that break down and release minerals from

bone matrix

Microscopic Anatomy of Microscopic Anatomy of Bone: Compact BoneBone: Compact Bone

Haversian system, or osteon—structural unit◦Lamellae

Weight-bearing Column-like matrix tubes

◦Central (Haversian) canal Contains blood vessels and nerves

Compact bone tissue

Microscopic Anatomy of Microscopic Anatomy of Bone: Compact BoneBone: Compact BonePerforating (Volkmann’s) canals

◦At right angles to the central canal◦Connects blood vessels and nerves

of the periosteum and central canalLacunae—small cavities that

contain osteocytesCanaliculi—hairlike canals that

connect lacunae to each other and the central canal

Endosteum lining bony canalsand covering trabeculae

Perforating (Volkmann’s) canal

Perforating (Sharpey’s) fibers

Periosteal blood vesselPeriosteum

Lacuna (withosteocyte)

Lacunae

Lamellae

NerveVeinArtery

Canaliculi

Osteocytein a lacuna

Circumferentiallamellae

Osteon(Haversian system)

Central(Haversian) canal

Centralcanal

Interstitial lamellae

Lamellae

Compactbone

Spongy bone

Compact Bone Compact Bone

Lacunae

Lamellae

Nerve

Vein

Artery

Canaliculus

Osteocytein a lacuna

Centralcanal

Compact Bone Compact Bone

Hormonal Regulation of Bone Hormonal Regulation of Bone GrowthGrowthGrowth hormone stimulates

epiphyseal plate activityThyroid hormone modulates

activity of growth hormoneTestosterone and estrogens (at

puberty)◦Promote adolescent growth spurts◦End growth by inducing epiphyseal

plate closure

Bone DepositBone Deposit

Occurs where bone is injured or added strength is needed

Requires a diet rich in protein; vitamins C, D, and A; calcium; phosphorus; magnesium; and manganese

Bone ResorptionBone ResorptionOsteoclasts secrete

◦Lysosomal enzymes (digest organic matrix)

◦Acids (convert calcium salts into soluble forms)

Dissolved matrix is transcytosed across osteoclast, enters interstitial fluid and then blood

Control of RemodelingControl of RemodelingWhat controls continual

remodeling of bone?◦Hormonal mechanisms that maintain

calcium homeostasis in the blood◦Mechanical and gravitational forces

Hormonal Control of Blood Hormonal Control of Blood CaCa2+2+

The level of blood calcium (Ca2+) must be maintained (homeostasis)

Calcium is necessary for◦Transmission of nerve impulses◦Muscle contraction◦Blood coagulation◦Secretion by glands and nerve cells◦Cell division

Which hormones are responsible for maintaining blood calcium?

Hormonal Control of Blood Hormonal Control of Blood CaCa2+2+

Primarily controlled by parathyroid hormone (PTH)

Blood Ca2+ levels

Parathyroid glands release PTH

PTH stimulates osteoclasts to degrade bone

matrix and release Ca2+

Blood Ca2+ levels

When blood calcium levels fall, PTH is released causing blood calcium levels to increase.

Hormonal Control of Blood Hormonal Control of Blood CaCa2+2+

May be affected to a lesser extent by calcitonin

Blood Ca2+ levels

Parafollicular cells of thyroid release calcitonin

Osteoblasts deposit calcium salts

Blood Ca2+ levels

When blood calcium levels rise, calcitonin is released causing blood calcium levels to decrease.

Response to Mechanical Response to Mechanical StressStress

Wolff’s law: A bone grows or remodels in response to forces or demands placed upon it

Observations supporting Wolff’s law:◦ Handedness (right or left handed) results in

bone of one upper limb being thicker and stronger

◦ Curved bones are thickest where they are most likely to buckle

◦ Trabeculae form along lines of stress◦ Large, bony projections occur where heavy,

active muscles attach

Bone MarkingsBone MarkingsBulges, depressions, and holes

serve as◦Sites of attachment for muscles,

ligaments, and tendons◦Joint surfaces◦Conduits for blood vessels and

nerves

Bone Markings: Bone Markings: ProjectionsProjectionsSites of muscle and ligament

attachment◦ Tuberosity—rounded projection

◦ Crest—narrow, prominent ridge

◦ Trochanter—large, blunt, irregular surface

◦ Line—narrow ridge of bone

◦ Tubercle—small rounded projection

◦ Condyle – rounded projection

◦ Epicondyle—raised area above a condyle

◦ Spine—sharp, slender projection

◦ Process—any bony prominence

Bone Markings: Bone Markings: ProjectionsProjectionsProjections that help to form joints

◦Head Bony expansion carried on a narrow

neck◦Facet Smooth, nearly flat articular surface

◦Condyle Rounded articular projection

◦Ramus Armlike bar

Bone Markings: Depressions Bone Markings: Depressions and Openingsand OpeningsMeatus

◦ Canal-like passageway

Sinus◦ Cavity within a

boneFossa

◦ Shallow, basinlike depression

Groove◦ Furrow

Fissure◦ Narrow, slitlike

openingForamen

◦ Round or oval opening through a bone

The skeleton

Bones of the Axial Bones of the Axial SkeletonSkeletonTwo main groups of bonesAxial skeleton—80 bones of the

head and trunkAppendicular skeleton—126

bones of the extremities

Framework of the SkullFramework of the Skull

Cranial bonesFacial bonesInfant skull

Framework of the Skull, Framework of the Skull, cont’dcont’d

Cranial bones◦Frontal ◦Parietal ◦Temporal ◦Ethmoid ◦Sphenoid ◦Occipital

Framework of the Skull, Framework of the Skull, cont’dcont’dFacial bones

◦Mandible ◦Maxillae ◦Zygomatic ◦Nasal ◦Lacrimal ◦Vomer◦Palatine◦Inferior nasal conchae◦Ossicle◦Hyoid

Framework of the Skull, Framework of the Skull, cont’dcont’d

Infant skull◦Anterior fontanel

ZOOMING IN • What type of joint is between bones of the skull?

The skull

The skull, inferior view.

ZOOMING IN • What two bones

make up each side of the hard palate?

ZOOMING IN

• What is a foramen?

Floor of cranium, superior view.

The skull, sagittal section.

ZOOMING IN • Which is

the largest fontanel?

Infant skull, showing Infant skull, showing fontanelsfontanels

Framework of the TrunkFramework of the TrunkVertebral column

◦ Cervical vertebrae◦ Thoracic vertebrae◦ Lumbar vertebrae◦ Sacral vertebrae (sacrum)◦ Coccygeal vertebrae (coccyx)

Thorax◦ Sternum◦ Ribs

True ribs False ribs

◦ Manubrium◦ Clavicular notch◦ Sternal angle◦ Xiphoid process

The Vertebral Column The Vertebral Column (Spine)(Spine)

five vertebral groups◦7 cervical in the

neck◦12 thoracic in the

chest◦5 lumbar in lower

back◦5 fused sacral at

base of spine◦4 fused coccygeal

Cervical vertebrae

Thoracic vertebrae

Atlas (C1)Axis (C2)

C7

Lumbar vertebrae

Sacrum

Coccyx Coccyx

Anterior view Posterior view

T1

T12

L1

L5

S1

S5

Newborn Spinal CurvatureNewborn Spinal Curvature

spine exhibits one continuous C-shaped curve at birth

known as primary curvature

Adult Spinal CurvaturesAdult Spinal Curvatures s-shaped vertebral column

with four normal curvatures◦ cervical◦ thoracic◦ lumbar◦ pelvic

primary curvatures – present at birth◦ thoracic and pelvic

secondary curvatures – develop later◦ cervical and lumbar◦ lifting head as it begins to

crawl develops cervical curvature

◦ walking upright develops lumbar curvature

Cervical curvature

Thoracic curvature

Lumbar curvature

Pelvic curvature

C7T1

T12

L1

S1L5

C1

Abnormal Spinal CurvaturesAbnormal Spinal Curvatures from disease, paralysis of trunk

muscles, poor posture, pregnancy, or congenital defect

scoliosis – abnormal lateral curvature◦ most common◦ usually in thoracic region◦ particularly of adolescent girls◦ developmental abnormality in which

the body and arch fail to develop on one side of the vertebrae

kyphosis (hunchback) – exaggerated thoracic curvature◦ usually from osteoporosis, also

osteomalacia or spinal tuberculosis, or wrestling or weightlifting in young boys

lordosis (swayback) – exaggerated lumbar curvature◦ is from pregnancy or obesity

KeyNormalPathological

(b) Kyphosis (“hunchback”) (c) Lordosis

(“hunchback”)

(a) Scoliosis

General Structure of VertebraGeneral Structure of Vertebra body (centrum)

◦ mass of spongy bone that contains red bone marrow

◦ covered with thin shell of compact bone◦ weight bearing portion◦ rough superior and inferior surfaces

provide firm attachment for intervertebral discs

vertebral foramina◦ collectively form vertebral canal for spinal

cord vertebral arch

◦ composed of two parts on each side◦ pedicle – pillarlike and lamina - platelike

spinous process◦ projection extending from the apex of arch◦ extends posteriorly and downward

transverse process◦ extends laterally from point where pedicel

and lamina meet superior articular processes

◦ project upward from one vertebra and meets inferior articular processes from the vertebra above

facets◦ flat articular surfaces covered with hyaline

cartilage

Spinous process

Lamina

Pedicle

Body

2nd lumbar vertebra (L2)Anterior

Posterior

Superior articularfacet

Transverseprocess

Vertebral foramen

Vertebralarch

Nucleus pulposus

Anulus fibrosus

Intervertebral disc

Intervertebral Foramen and Intervertebral Foramen and DiscsDiscs

intervertebral foramen◦ when two vertebrae are joined

they exhibit and opening;◦ intervertebral foramen -

passageway for spinal nerves◦ inferior vertebral notch in the

pedicle of the upper vertebra◦ superior vertebral notch in the

pedicle of the lower vertebra

intervertebral discs (23)◦ pad consisting of:

nucleus pulposus - inner gelatinous mass

anulus fibrosus – outer ring of fibrocartilage

◦ bind vertebrae together◦ support weight of the body◦ absorb shock◦ herniated disc (‘ruptured’ or

‘slipped’ disc) puts painful pressure on spinal nerve or spinal cord

L1

L2

L3

Intervertebral disc

Spinous process

Superior articularprocess of L1

Inferior vertebralnotch of L1

Superior vertebralnotch of L2

Inferior articularprocess of L3

Intervertebralforamen

The first two cervical The first two cervical vertebrae: Atlas and Axisvertebrae: Atlas and Axis

Atlas and Axis Articulation

Dens

Axis of rotation

Atlas

Axis

Transverseligament

Atlantoaxial joint

ZOOMING IN • To what bones do the costal cartilages attach?

Bones of the thorax Bones of the thorax

Bones of the Appendicular Bones of the Appendicular SkeletonSkeleton

Two divisions UpperLower

The Upper Division of the The Upper Division of the Appendicular SkeletonAppendicular Skeleton

The shoulder girdle◦Clavicle (collarbone)◦Scapula (shoulder blade)◦Supraspinous fossa and infraspinous

fossa◦Acromion◦Glenoid cavity◦Coracoid process

The Upper Division of the The Upper Division of the Appendicular Skeleton, Appendicular Skeleton, cont’dcont’d

The upper extremity◦Humerus (arm bone)◦Medial and lateral epicondyles◦Trochlea◦Ulna and radius (forearm bones)◦Distal projection (styloid process)◦Olecranon◦Trochlear notch (semilunar notch)◦Carpal bones◦Metacarpal bones◦Phalanges (finger bones)

ZOOMING IN • What does the prefix supra mean? • What does the prefix infra mean?

The shoulder girdle and The shoulder girdle and scapulascapula

Appendicular Skeleton: Appendicular Skeleton: Lower Lower DivisionDivision

The pelvic bones◦ Ilium

Iliac crest Anterior superior iliac spine

◦ Ischium Ischial spine Ischial tuberosity

◦ Pubis Pubic symphysis Acetabulum Obturator foramen Ossa coxae

ZOOMING IN • What bone is nicknamed the “sit bone”?

The Pelvic BonesThe Pelvic Bones

Comparison of male and female pelvisComparison of male and female pelvis

The lower extremity◦ Femur

Greater trochanter Lesser trochanter Linea aspera

◦ Patella◦ Tibia (shin bone)

Medial malleolus◦ Fibula

Lateral malleolus◦ Tarsal bones

Calcaneus (heel bone)◦ Metatarsal bones◦ Phalanges

Appendicular Skeleton: Appendicular Skeleton: Lower Lower Division, cont’dDivision, cont’d

The right femur (thigh bone)The right femur (thigh bone)

ZOOMING IN • What is

the medial bone of the leg?

Tibia and fibula of the Tibia and fibula of the right legright leg

Disorders of BoneDisorders of Bone

Metabolic diseasesTumorsInfectionsStructural problems

Metabolic DisordersMetabolic Disorders

Characterized by a lack of normal bone formation or excess loss of bone tissue

Osteoporosis◦Osteopenia

Paget’s disease (osteitis deformans)

Osteomalacia (in children, rickets)

TumorsTumors

Two types found in bone tissueBenignMalignant

◦Osteosarcomas◦Chondrosarcomas

InfectionInfection

Two types found in bone tissueOsteomyelitis

◦Inflammation of the bone caused by pyogenic bacteria

Tuberculosis◦Pott disease (tuberculosis of the

spine)

Structural DisordersStructural Disorders

Curvatures of the spine◦Kyphosis (hunchback)◦Lordosis (swayback)◦Scoliosis

Cleft palateFlatfoot

FracturesFracturesTypes of fracturesClosedOpenGreenstickImpactedComminutedSpiralTransverseOblique

Skeletal Changes in the Skeletal Changes in the AgingAging

Bones undergo significant changesLoss of calcium saltsDecrease in proteinReduction in collagenLoss of heightDecrease in chest diameter

The JointsThe Joints

Classified by material between adjoining bones and by degree of movement permitted

Fibrous◦Synarthrosis (immovable)

Cartilaginous◦Amphiarthrosis (slightly movable)

Synovial◦Diarthrosis (freely movable)

More About Synovial More About Synovial JointsJointsBones are joined by other

structures in synovial jointsLigamentsJoint capsuleHyaline (articular) cartilageMedial meniscus and lateral

meniscusFatBursae

Structure of a synovial joint.Structure of a synovial joint.

Types of Synovial JointsTypes of Synovial Joints

Classified by types of movement they allow

Gliding HingePivotCondyloidSaddleBall-and-socket

Movement at Synovial Movement at Synovial JointsJointsFlexionExtensionAbductionAdductionCircumductionRotation

Movement at Synovial Movement at Synovial Joints, cont’dJoints, cont’dMovements characteristic of

forearm and ankle◦Supination◦Pronation◦Inversion◦Eversion◦Dorsiflexion◦Plantar flexion

Disorders of JointsDisorders of JointsMechanical disorders

◦Dislocation◦Sprain

Arthritis◦Osteoarthritis (degenerative joint

disease [DJD])◦Rheumatoid arthritis◦Septic (infectious) arthritis◦Gout

Disorders of Joints, cont’dDisorders of Joints, cont’dHerniated disk

Backache◦Vertebrae diseases◦Intervertebral disk disorders◦Supporting structure abnormalities◦Abdominopelvic disorders◦Lumbosacral joint strains

Arthroscopic examination of the kneeArthroscopic examination of the knee

End of PresentationEnd of Presentation