lecture presentation by patty bostwick-taylor florence-darlington technical college chapter 5 the...

Lecture Presentation by Patty Bostwick-Taylor

Florence-Darlington Technical College

Chapter 5

The Skeletal System

Two subdivisions of the skeleton1. Axial skeleton

2. Appendicular skeleton Parts of the skeletal system

Bones (skeleton) Joints Cartilages Ligaments

Functions of Bones

Support the body Protect soft organs

Skull and vertebrae protect brain and spinal cord Rib cage protects thoracic cavity organs

Attached skeletal muscles allow movement Store minerals and fats

Calcium and phosphorus Fat in the internal marrow cavity

Blood cell formation (hematopoiesis)

Bones of the Human Body

The adult skeleton has 206 bones Two basic types of bone tissue

1. Compact bone Dense, smooth, and homogeneous

2. Spongy bone Small needle-like pieces of bone Many open spaces

Figure 5.1 Flat bones consist of a layer of spongy bone sandwiched between two thin layers of compact bone.

Spongybone

Compactbone

Classification of Bones

Bones are classified on the basis of shape, as: Long Short Flat Irregular

Figure 5.2 Classification of bones on the basis of shape.

(a) Long bone(humerus)

(b) Irregular bone(vertebra),right lateral view

(d) Short bone(talus)

(c) Flat bone(sternum)

Long bones Typically longer than they are wide Shaft with heads situated at both ends Contain mostly compact bone All of the bones of the limbs (except wrist, ankle, and

kneecap bones) are long bones Examples:

Femur Humerus

Figure 5.2a Classification of bones on the basis of shape.

(a) Long bone(humerus)

Short bones Generally cube-shaped Contain mostly spongy bone Include bones of the wrist and ankle Sesamoid bones are a type of short bone that form

within tendons (patella) Examples:

Carpals Tarsals

Figure 5.2d Classification of bones on the basis of shape.

(d) Short bone(talus)

Flat bones Thin, flattened, and usually curved Two thin layers of compact bone surround a layer of

spongy bone Examples:

Skull Ribs Sternum

Figure 5.1 Flat bones consist of a layer of spongy bone sandwiched between two thin layers of compact bone.

Spongybone

Compactbone

Figure 5.2c Classification of bones on the basis of shape.

(c) Flat bone(sternum)

Irregular bones Irregular shape Do not fit into other bone classification categories Examples:

Vertebrae Hip bones

Figure 5.2b Classification of bones on the basis of shape.

(b) Irregular bone(vertebra),right lateral view

Concept Link

Anatomy of a Long Bone

Diaphysis Shaft Makes up most of bone’s length Composed of compact bone

Periosteum Outside covering of the diaphysis Fibrous connective tissue membrane Perforating (Sharpey’s) fibers secure periosteum to

underlying bone

Figure 5.3a The structure of a long bone (humerus of arm).

Proximalepiphysis

Diaphysis

Distalepiphysis(a)

Articularcartilage

Spongy bone

EpiphyseallinePeriosteum

Compact boneMedullarycavity (linedby endosteum)

Figure 5.3c The structure of a long bone (humerus of arm).

Endosteum

Yellow bonemarrowCompact bone

Periosteum

Perforating(Sharpey’s) fibers

Nutrientarteries

Epiphysis Ends of the bone Composed mostly of spongy bone enclosed by thin

layer of compact bone Articular cartilage

Covers the external surface of the epiphyses Made of hyaline cartilage Decreases friction at joint surfaces

Figure 5.3b The structure of a long bone (humerus of arm).

Articularcartilage

Spongy bone

Compact bone

Epiphyseal plate Flat plate of hyaline cartilage seen in young, growing

bone Causes lengthwise growth of a long bone

Epiphyseal line Remnant of the epiphyseal plate Seen in adult bones

Proximalepiphysis

Diaphysis

Distalepiphysis(a)

Articularcartilage

Spongy bone

Marrow (medullary) cavity Cavity inside the shaft Contains yellow marrow (mostly fat) in adults Contains red marrow for blood cell formation in

infants In adults, red marrow is situated in cavities of

spongy bone and epiphyses of some long bones

Proximalepiphysis

Diaphysis

Distalepiphysis(a)

Articularcartilage

Spongy bone

Bone Markings

Surface features of bones Sites of attachments for muscles, tendons, and

ligaments Passages for nerves and blood vessels

Categories of bone markings Projections or processes—grow out from the bone

surface Terms often begin with “T”

Depressions or cavities—indentations Terms often begin with “F”

Table 5.1 Bone Markings (1 of 3).

Microscopic Anatomy of Compact Bone

Osteocytes are situated within cavities known as lacunae

Lacunae are arranged in concentric rings called lamellae

Lamellae are rings situated around the central (Haversian) canal

Figure 5.4a Microscopic structure of compact bone.

Spongy bone

Perforating(Volkmann’s) canal

Blood vessel continuesinto medullary cavitycontaining marrow

Blood vessel

Compact bone

Central (Haversian) canal

Perforating (Sharpey’s) fibers

Periosteum

Periosteal blood vessel

Osteon(Haversiansystem)

Lamellae

Microscopic Anatomy of Bone

Central (Haversian) canal Opening in the center of an osteon Runs lengthwise through bone Carries blood vessels and nerves

Osteon (Haversian system) A unit of bone containing central canal and matrix

Figure 5.4b Microscopic structure of compact bone.

Lamella

Osteocyte

CanaliculusLacunaCentral(Haversian) canal(b)

Figure 5.4c Microscopic structure of compact bone.

Osteon

Interstitiallamellae

LacunaCentral(Haversian) canal

Microscopic Anatomy of Bone

Canaliculi Tiny canals Radiate from the central canal to lacunae Form a transport system connecting all bone cells to

a nutrient supply Perforating (Volkmann’s) canal

Canal perpendicular to the central canal Carries blood vessels and nerves

Figure 5.4b Microscopic structure of compact bone.

Lamella

Osteocyte

CanaliculusLacunaCentral(Haversian) canal(b)

Bone Components

Organic parts of the matrix make bone flexible Calcium salts deposited in the matrix make bone

Bone Formation and Growth

Ossification Process of bone formation Occurs on hyaline cartilage models or fibrous

membranes Long bone growth involves two major phases

Figure 5.5 Stages of long-bone formation in an embryo, fetus, and young child.

Hyalinecartilage

New center ofbone growth

Medullarycavity

Bone startingto replacecartilage

Hyalinecartilagemodel

Bone collar

In an embryo In a fetus In a child

Articularcartilage

Spongybone

Epiphysealplate cartilage

New boneforming

Growthin bonewidth

Growthin bonelength

Invadingblood vessels

New boneforming

Epiphysealplate cartilage

Two major phases of ossification in long bones1. Osteoblasts

Bone-forming cells Cover hyaline cartilage model

2. Enclosed cartilage is digested away, opening up a medullary cavity

By birth, most cartilage is converted to bone except for two regions in a long bone:

1. Articular cartilages

2. Epiphyseal plates New cartilage is formed continuously on external

face of these two cartilages Old cartilage is broken down and replaced by bony

matrix

Figure 5.6 Growth and remodeling of long bones.

Bone grows inlength because:

Growing shaft isremodeled as:

Bone growth Bone remodeling

Articular cartilage

Epiphyseal plate

Bone isresorbed here.

Bone is addedby appositionalgrowth here.

Bone is resorbed here.

Cartilagegrows here.

Cartilageis replacedby bone here.

Cartilagegrows here.

Cartilageis replaced bybone here.

Bones grow in length and width Appositional growth

Growth in diameter

Controlled by hormones such as growth hormone Epiphyseal plates are converted to bone during

adolescence Growth in length ends

Bone Remodeling

Bones are lengthened until growth stops Bones are remodeled throughout life in response to

two factors:1. Blood calcium levels

2. Pull of gravity and muscles on the skeleton

Bone Remodeling

Parathyroid hormone (PTH) Released when blood calcium levels are low Activates osteoclasts (bone-destroying cells) Osteoclasts break down bone and release calcium

ions into the blood Hypercalcemia (high blood calcium levels) prompts

calcium storage to bones

Bone Fractures

Fracture: break in a bone Types of bone fractures

Closed (simple) fracture: break that does not penetrate the skin

Open (compound) fracture: broken bone penetrates through the skin

Bone Fractures

Bone fractures are treated by reduction and immobilization Closed reduction: bones are manually coaxed into

position by physician’s hands Open reduction: bones are secured with pins or

wires during surgery

Repair of Bone Fractures

Hematoma (blood-filled swelling) is formed Fibrocartilage callus forms

Cartilage matrix, bony matrix, collagen fibers splint the broken bone

Bony callus replaces the fibrocartilage callus Osteoblasts and osteoclasts migrate in

Bone remodeling occurs in response to mechanical stresses

Figure 5.7 Stages in the healing of a bone fracture.

Hematoma

Externalcallus

Internalcallus(fibroustissue andcartilage)

New bloodvessels

Spongybonetrabecula

Hematomaforms.

2 3 Fibrocartilagecallus forms.

Bony callusforms.

Boneremodelingoccurs.

Bonycallus ofspongybone

Healedfracture

Common Types of Fractures

Comminuted: bone breaks into many fragments Compression: bone is crushed Depressed: broken bone portion is pressed inward Impacted: broken bone ends are forced into each

other Spiral: ragged break occurs when excessive

twisting forces are applied to a bone Greenstick: bone breaks incompletely

Table 5.2 Common Types of Fractures.

The Axial Skeleton

Forms the longitudinal axis of the body Divided into three parts

1. Skull

2. Vertebral column

3. Bony thorax

Figure 5.8a The human skeleton.

(a) Anterior view

Thoraciccage

Vertebralcolumn

(ribs andsternum)

Sacrum

Facial bones

Cranium

Clavicle

ScapulaSternumRibHumerus

VertebraRadiusUlna

FemurPatella

Fibula

TarsalsMetatarsalsPhalanges

Carpals

PhalangesMetacarpals

Figure 5.8b The human skeleton.

(b) Posterior view

Bones ofpectoralgirdle

Upper limb

Bones ofpelvicgirdle

Lowerlimb

Cranium

Clavicle

Scapula

RibHumerus

VertebraRadiusUlna

Carpals

PhalangesMetacarpalsFemur

Fibula

Concept Link

The Skull

Two sets of bones1. Cranium bones enclose the brain

2. Facial bones Hold eyes in anterior position Allow facial muscles to express feelings

Bones are joined by sutures Only the mandible is attached by a freely movable

The Skull

8 cranial bones protect the brain1. Frontal bone

2. Occipital bone

3. Ethmoid bone

4. Sphenoid bone

5–6. Parietal bones (pair)

7–8. Temporal bones (pair)

The Skull

There are 14 facial bones. All are paired except for the single mandible and vomer.

1–2. Maxillae

3–4. Zygomatics

5–6. Palatines

7–8. Nasals

9–10. Lacrimals

11–12. Inferior nasal conchae

13. Mandible

14. Vomer

Figure 5.9 Human skull, lateral view.

Coronal suture

Parietal bone

Temporal bone

Lambdoid suture

Squamous sutureOccipital bone

Zygomatic process

External acousticmeatus

Mastoid process

Styloid process

Mandibular ramus

Frontal bone

Sphenoid bone

Ethmoid bone

Lacrimal bone

Nasal bone

Zygomatic boneMaxilla

Alveolar processes

Mandible (body)

Mental foramen

Figure 5.10 Human skull, superior view (top of cranium removed).

Sphenoidbone

Temporal bone

Internalacoustic meatus

Parietal bone

Occipital bone

Foramen magnum

Frontal bone

Ethmoidbone

Cribriform plateCrista galli

Optic canal

Sella turcicaForamen ovale

Jugular foramen

Figure 5.11 Human skull, inferior view (mandible removed).

Maxilla

Sphenoid bone(greater wing)

Foramen ovale

Carotid canal

Jugular foramen

Occipital condyle

Foramen magnum

Maxilla(palatine process)

Palatine bone

Hardpalate

Zygomatic bone

Temporal bone(zygomatic process)

Mandibular fossa

Styloid process

Mastoid process

Temporal bone

Parietal bone

Occipital bone

Figure 5.12 Human skull, anterior view.

Mandible

Coronal suture

Parietal bone

Nasal bone

Sphenoid bone

Ethmoid boneLacrimal bone

Zygomatic bone

Maxilla

Frontal bone

Superior orbitalfissure

Temporal boneOptic canal

Middle nasal conchaof ethmoid bone

Inferior nasal concha

Alveolar processes

Paranasal Sinuses

Hollow portions of bones surrounding the nasal cavity

Functions of paranasal sinuses Lighten the skull Amplify sounds made as we speak

Figure 5.13a Paranasal sinuses.

Frontal sinus

Ethmoid sinus

Sphenoidalsinus

Maxillarysinus

(a) Anterior view

Figure 5.13b Paranasal sinuses.

Frontal sinus

Ethmoid sinus

SphenoidalsinusMaxillarysinus

(b) Medial view

The Hyoid Bone

Closely related to mandible and temporal bones The only bone that does not articulate with another

bone Serves as a movable base for the tongue Aids in swallowing and speech

Figure 5.14 Anatomical location and structure of the hyoid bone.

Greater horn

Lesser horn

The Fetal Skull

The fetal skull is large compared to the infant’s total body length Fetal skull is 1/4 body length compared to adult skull,

which is 1/8 body length Fontanels are fibrous membranes connecting the

cranial bones Allow skull compression during birth Allow the brain to grow during later pregnancy and

infancy Convert to bone within 24 months after birth

Figure 5.15a The fetal skull.

Frontal bone

Parietalbone

Posterior fontanel

Anteriorfontanel

Occipitalbone

Figure 5.15b The fetal skull.

Parietal bone

Posteriorfontanel

Anterior fontanelSphenoidalfontanel

Frontalbone

Temporal bone

Occipital bone

Mastoidfontanel

Vertebral Column (Spine)

Vertebral column provides axial support Extends from skull to the pelvis

26 single vertebral bones are separated by intervertebral discs 7 cervical vertebrae are in the neck 12 thoracic vertebrae are in the chest region 5 lumbar vertebrae are associated with the lower

9 vertebrae fuse to form two composite bones Sacrum formed by the fusion of 5 vertebrae Coccyx (tailbone) formed by the fusion of 3 to 5

vertebrae

Figure 5.16 The vertebral column.

1st lumbar vertebra

Intervertebral foramen

Intervertebral disc

Spinous process

Transverse process

1st thoracic vertebra

1st cervical vertebra(atlas)

2nd cervical vertebra(axis)

Anterior Posterior

Cervical curvature (concave)7 vertebrae, C1 – C7

Thoracic curvature (convex)12 vertebrae, T1 – T12

Lumbar curvature (concave)5 vertebrae, L1 – L5

Sacral curvature (convex)5 fused vertebrae

Coccyx4 fused vertebrae

Primary curvatures Spinal curvatures of the thoracic and sacral regions Present from birth Form a C-shaped curvature as in newborns

Secondary curvatures Spinal curvatures of the cervical and lumbar regions Develop after birth Form an S-shaped curvature as in adults

Figure 5.17 The C-shaped spine typical of a newborn.

Figure 5.18 Abnormal spinal curvatures.

(a) Scoliosis (b) Kyphosis (c) Lordosis

Parts of a typical vertebra Body (centrum) Vertebral arch

Pedicle Lamina

Vertebral foramen Transverse processes Spinous process Superior and inferior articular processes

Figure 5.19 A typical vertebra, superior view.

LaminaPosterior

Vertebralarch

Transverseprocess

Spinousprocess

Vertebralforamen

Superiorarticularprocessandfacet

Figure 5.20a Regional characteristics of vertebrae.

Transverseprocess

(a) ATLAS AND AXIS

Posteriorarch

Superior view of axis (C2)

Anterior arch

Superior view of atlas (C1)

Transverseprocess

Spinous process

DensBody

Facet onsuperiorarticularprocess

Figure 5.20b Regional characteristics of vertebrae.

(b) TYPICAL CERVICAL VERTEBRAE

Right lateral view

Spinous processFacet onsuperiorarticularprocess

Vertebralforamen

Transverseprocess

Superior view

Facet on inferiorarticular process

Transverseprocess

Superior articularprocessSpinousprocess

Figure 5.20c Regional characteristics of vertebrae.

(c) THORACIC VERTEBRAE

Right lateral view

Transverseprocess

Spinous process

Facetfor rib

Vertebralforamen

Facet on transverseprocess

Spinous process

Costal facetfor rib

Superior view

process

Facet onsuperiorarticular

Facet on superiorarticular process

Figure 5.20d Regional characteristics of vertebrae.

(d) LUMBAR VERTEBRAE

Right lateral view

Transverseprocess

Vertebralforamen

Facet on superiorarticular processBody

BodySuperior articularprocess

Spinousprocess

Facet on inferiorarticular process

Superior view

Spinous process

Figure 5.21 Sacrum and coccyx, posterior view.

Sacrum

CoccyxSacralhiatus

Posteriorsacralforamina

Mediansacralcrest

Auricularsurface

SuperiorarticularprocessSacral

The Bony Thorax

Forms a cage to protect major organs Consists of three parts

1. Sternum

2. Ribs True ribs (pairs 1–7) False ribs (pairs 8–12) Floating ribs (pairs 11–12)

3. Thoracic vertebrae

Figure 5.22a The bony thorax (thoracic cage).

Clavicular notch

Trueribs(1–7)

Falseribs(8–12)

(a)Floatingribs (11, 12)

vertebra Costal cartilage

Intercostalspaces

T1 vertebraJugular notch

ManubriumSternal angleBodyXiphisternaljointXiphoidprocess

Sternum

Figure 5.22b The bony thorax (thoracic cage).

Jugularnotch

Sternalangle

Xiphisternaljoint

The Appendicular Skeleton

Composed of 126 bones Limbs (appendages) Pectoral girdle Pelvic girdle

Figure 5.8a The human skeleton.

(a) Anterior view

Thoraciccage

Vertebralcolumn

(ribs andsternum)

Sacrum

Facial bones

Cranium

Clavicle

ScapulaSternumRibHumerus

VertebraRadiusUlna

FemurPatella

Fibula

TarsalsMetatarsalsPhalanges

Carpals

PhalangesMetacarpals

Figure 5.8b The human skeleton.

(b) Posterior view

Bones ofpectoralgirdle

Upper limb

Bones ofpelvicgirdle

Lowerlimb

Cranium

Clavicle

Scapula

RibHumerus

VertebraRadiusUlna

Carpals

PhalangesMetacarpalsFemur

Fibula

The Pectoral (Shoulder) Girdle

Composed of two bones that attach the upper limb to the axial skeletal

1. Scapula

2. Clavicle Pectoral girdle (2)

Light, poorly reinforced girdle Allows the upper limb a great deal of freedom

Figure 5.23a Bones of the shoulder girdle.

Scapula

ClavicleAcromio-clavicular joint

(a) Articulated right shoulder (pectoral)girdle showing the relationship tobones of the thorax and sternum

Figure 5.23b Bones of the shoulder girdle.

Inferior view

(b) Right clavicle, superior andinferior views

Posterior

Acromial end

Acromial(lateral) end

Superior view

Sternal end

Figure 5.23c Bones of the shoulder girdle.

Suprascapular notch

Superiorangle

Medialborder

Lateral border

Coracoid process

Acromion

Glenoid cavityat lateral angle

(c) Right scapula, posterior aspect

Figure 5.23d Bones of the shoulder girdle.

Suprascapular notchAcromion

Coracoidprocess

Glenoidcavity

Superior borderSuperiorangle

Lateral(axillary)border

Medial(vertebral)border

Inferior angle(d) Right scapula, anterior aspect

Bones of the Upper Limbs

Humerus Forms the arm Single bone Proximal end articulation

Head articulates with the glenoid cavity of the scapula Distal end articulation

Trochlea and capitulum articulate with the bones of the forearm

Figure 5.24a Bones of the right arm and forearm.

Greatertubercle

Lessertubercle

Head ofhumerus

Anatomicalneck

Intertubercularsulcus

Deltoidtuberosity

Medialepicondyle

Trochlea

RadialfossaCoronoidfossa

Capitulum

Figure 5.24b Bones of the right arm and forearm.

Head ofhumerus

Anatomicalneck

Surgicalneck

Radialgroove

Deltoidtuberosity

Olecranonfossa

Lateralepicondyle

Medialepicondyle

Trochlea

The forearm has two bones1. Ulna—medial bone in anatomical position

Proximal end articulation Coronoid process and olecranon articulate with the

humerus

2. Radius—lateral bone in anatomical position Proximal end articulation

Head articulates with the capitulum of the humerus

Figure 5.24c Bones of the right arm and forearm.

NeckRadialtuberosity

Radius

TrochlearnotchOlecranon

CoronoidprocessProximalradioulnarjoint

Inter-osseousmembrane

UlnarstyloidprocessDistal

radioulnar joint

Radialstyloidprocess

Hand Carpals—wrist

8 bones arranged in two rows of 4 bones in each hand

Metacarpals—palm 5 per hand

Phalanges—fingers and thumb 14 phalanges in each hand In each finger, there are 3 bones In the thumb, there are only 2 bones

Figure 5.25 Bones of the right hand, anterior view.

Distal

Middle

Proximal

Phalanges(fingers)

Metacarpals(palm)

Carpals(wrist)

Hamate

Pisiform

Triquetrum

Lunate

Trapezium

Trapezoid

Scaphoid

Capitate

Radius

Bones of the Pelvic Girdle

Formed by 2 coxal (ossa coxae) bones Composed of three pairs of fused bones

1. Ilium

2. Ischium

3. Pubis Pelvic girdle 2 coxal bones, sacrum Bony pelvis 2 coxal bones, sacrum, coccyx

Bones of the Pelvic Girdle

The total weight of the upper body rests on the pelvis

Pelvis protects several organs Reproductive organs Urinary bladder Part of the large intestine

Figure 5.26a The bony pelvis.

Ischium

Coxal bone(or hip bone) Sacrum

Coccyx

Pubic arch

Iliac crest

Sacroiliacjoint

Pelvic brim

Ischial spine

Acetabulum

Pubic symphysis

Figure 5.26b The bony pelvis.

Iliac crest

Anterior superioriliac spine

Anterior inferioriliac spine

Acetabulum

Body of pubis

Inferior pubicramus

Obturatorforamen

Posteriorsuperioriliac spine

Posteriorinferioriliac spine

Greater sciaticnotchIschial body

Ischial spine

Ischial tuberosity

Ischium

Ischial ramus(b)

Gender Differences of the Pelvis

The female’s pelvis: Inlet is larger and more circular Pelvis as a whole is shallower, and the bones are

lighter and thinner Ilia flare more laterally Sacrum is shorter and less curved Ischial spines are shorter and farther apart; thus, the

outlet is larger Pubic arch is more rounded because the angle of the

pubic arch is greater

Figure 5.26c The bony pelvis.

False pelvis

Inlet oftruepelvis

Pelvic brim

False pelvis

Inlet oftruepelvis

Pelvic brim

Pubic arch(less than 90°)

Pubic arch(more than 90°)

Bones of the Lower Limbs

Femur—thigh bone The heaviest, strongest bone in the body Proximal end articulation

Head articulates with the acetabulum of the coxal (hip) bone

Distal end articulation Lateral and medial condyles articulate with the tibia in

the lower leg

Figure 5.27a Bones of the right thigh and leg.

Inter-trochantericline

Lessertrochanter

Lateralcondyle

Patellarsurface

Figure 5.27b Bones of the right thigh and leg.

Lessertrochanter

Glutealtuberosity

Greatertrochanter

Inter-trochantericcrest

Lateralcondyle

Intercondylarfossa

Medialcondyle

The lower leg has two bones1. Tibia—shinbone; larger and medially oriented

Proximal end articulation Medial and lateral condyles articulate with the femur to

form the knee joint

2. Fibula—thin and sticklike; lateral to the tibia Has no role in forming the knee joint

Figure 5.27c Bones of the right thigh and leg.

Intercondylareminence

LateralcondyleHead

Proximaltibiofibularjoint

Medialcondyle

Tibialtuberosity

Interosseousmembrane

Anteriorborder

Medialmalleolus

Distaltibiofibularjoint

Lateralmalleolus

Fibula

The foot Tarsals—7 bones

Two largest tarsals Calcaneus (heel bone) Talus

Metatarsals—5 bones form the sole of the foot

Phalanges—14 bones form the toes

Figure 5.28 Bones of the right foot, superior view.

Medialcuneiform

Tarsals:

Phalanges:

Metatarsals

Tarsals:Intermediatecuneiform

Navicular

DistalMiddle

Proximal

Lateralcuneiform

Cuboid

Calcaneus

Arches of the Foot

Bones of the foot are arranged to form three strong arches Two longitudinal One transverse

Figure 5.29 Arches of the foot.

Medial longitudinal arch

Transverse arch

Lateral longitudinalarch

Joints

Joints are articulations Two or more bones meet

Functions of joints Hold bones together Allow for mobility

Two ways joints are classified Functionally Structurally

Functional Classification of Joints

Synarthroses Immovable joints

Amphiarthroses Slightly movable joints

Diarthroses Freely movable joints

Structural Classification of Joints

Fibrous joints Generally immovable

Cartilaginous joints Immovable or slightly movable

Synovial joints Freely movable

Concept Link

Fibrous Joints

Bones united by fibrous tissue Types

Sutures Immobile

Syndesmoses Allow more movement than sutures but still immobile Example: Distal end of tibia and fibula

Gomphosis Immobile

Figure 5.30a Types of joints.

Fibrousconnectivetissue

(a) Suture

Fibrous joints

Figure 5.30b Types of joints.

(b) Syndesmosis

FibulaFibrousconnectivetissue

Fibrous joints

Cartilaginous Joints

Bones connected by fibrocartilage Types

Synchrondrosis Immobile

Symphysis Slightly movable Example: Pubic symphysis, intervertebral joints

Figure 5.30c Types of joints.

First rib

Cartilaginous joints

(c) Synchondrosis

Hyalinecartilage

Sternum

Figure 5.30d Types of joints.

(d) Symphysis

Vertebrae

Fibro-cartilage

Figure 5.30e Types of joints.

(e) Symphysis

PubisFibro-cartilage

Synovial Joints

Articulating bones are separated by a joint cavity Synovial fluid is found in the joint cavity Four distinguishing features of synovial joints

1. Articular cartilage

2. Articular capsule

3. Joint cavity

4. Reinforcing ligaments

Figure 5.30f Types of joints.

(f) Multiaxial joint

Humerus

Articular (hyaline)cartilage

(shoulder joint)

Scapula

Articularcapsule

Synovial joints

Figure 5.30g Types of joints.

(g) Uniaxial joint

Radius

Articular capsule

Articular (hyaline)cartilage

Humerus

(elbow joint)

Synovial joints

Figure 5.30h Types of joints.

Synovial joints

(h) Biaxial joint(intercarpal joints of hand)

Carpals

Radius

Articularcapsule

Synovial Joints

Bursae—flattened fibrous sacs Lined with synovial membranes Filled with synovial fluid Not actually part of the joint

Tendon sheath Elongated bursa that wraps around a tendon

Synovial Joints

Types of synovial joints based on shape: Plane joint Hinge joint Pivot joint Condylar joint Saddle joint Ball-and-socket joint

Figure 5.31 General structure of a synovial joint.

Acromion ofscapula

Ligament

Tendonsheath

Tendon ofbiceps muscle

Joint cavitycontainingsynovial fluid

Articular(hyaline)cartilage

Synovial membrane

Fibrous layer of thearticular capsule

Humerus

Figure 5.32a Types of synovial joints.

(a) Plane joint

NonaxialUniaxialBiaxialMultiaxial

(a)(e)(d)

Figure 5.32b Types of synovial joints.

(a)(e)(d)

HumerusUlna

(b) Hinge joint

Figure 5.32c Types of synovial joints.

(a)(e)(d)

(b)(c) Pivot joint

UlnaRadius

Figure 5.32d Types of synovial joints.

(a)(e)(d)

(b)MetacarpalPhalanx

(d) Condylar joint

Figure 5.32e Types of synovial joints.

(a)(e)(d)

(b)(e) Saddle joint

CarpalMetacarpal #1

Figure 5.32f Types of synovial joints.

(a)(e)(d)

Head ofhumerus

Scapula

(f) Ball-and-socket joint

Inflammatory Conditions Associated with Joints

Bursitis—inflammation of a bursa, usually caused by a blow or friction

Tendonitis—inflammation of tendon sheaths Arthritis—inflammatory or degenerative diseases of

joints Over 100 different types The most widespread crippling disease in the United

States Initial symptoms: pain, stiffness, swelling of the joint

Clinical Forms of Arthritis

Osteoarthritis (OA) Most common chronic arthritis Probably related to normal aging processes

Rheumatoid arthritis (RA) An autoimmune disease—the immune system

attacks the joints Symptoms begin with bilateral inflammation of

certain joints Often leads to deformities

Figure 5.33 X-ray image of a hand deformed by rheumatoid arthritis.

Clinical Forms of Arthritis

Gouty arthritis (gout) Inflammation of joints is caused by a deposition of

uric acid crystals from the blood Can usually be controlled with diet More common in men

Developmental Aspects of the Skeletal System

Fontanels Allow brain growth and ease birth passage Present in the skull at birth Completely replaced with bone within 2 years after

Developmental Aspects of the Skeletal System

Growth of cranium after birth is related to brain growth Increase in size of the facial skeleton follows tooth

development and enlargement of the respiratory passageways.

Figure 5.34 Ossification centers in the skeleton of a 12-week-old fetus are indicated by the darker areas. Lighter regions are still fibrous or cartilaginous.

Frontalbone of skull

Parietalbone

Occipitabone

Clavicle

Scapula

Mandible

RadiusUlna

Humerus

Vertebra

Hip bone

Skeletal Changes Throughout Life

Fetus Long bones are formed of hyaline cartilage Flat bones begin as fibrous membranes Flat and long bone models are converted to bone

Birth Fontanels remain until around age 2

Adolescence Epiphyseal plates become ossified, and long bone

growth ends Size of cranium in relationship to body

2 years old—skull is larger in proportion to the body compared to that of an adult

8 or 9 years old—skull is near adult size and proportion

Between ages 6 and 11, the face grows out from the skull

Figure 5.35a Differences in the growth rates for some parts of the body compared to others determine body proportions.

Human newborn Human adult

Figure 5.35b Differences in the growth rates for some parts of the body compared to others determine body proportions.

Newborn 2 yrs. 5 yrs. 15 yrs. Adult

Curvatures of the spine Primary curvatures are present at birth and are

convex posteriorly Secondary curvatures are associated with a child’s

later development and are convex anteriorly Abnormal spinal curvatures (scoliosis and lordosis)

are often congenital

Figure 5.18 Abnormal spinal curvatures.

(a) Scoliosis (b) Kyphosis (c) Lordosis

Osteoporosis Bone-thinning disease afflicting

50 percent of women over age 65 20 percent of men over age 70

Disease makes bones fragile, and bones can easily fracture

Vertebral collapse results in kyphosis (also known as “dowager’s hump”)

Estrogen aids in health and normal density of a female skeleton

Figure 5.36 Osteoporosis.

Figure 5.37 Vertebral collapse due to osteoporosis.

Age 40 Age 60 Age 70

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