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Lecture Presentation by

Patty Bostwick-Taylor

Florence-Darlington Technical College

Chapter 5

The Skeletal System

© 2015 Pearson Education, Inc.


The Skeletal System

Two subdivisions of the skeleton

1. 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.

Spongy

bone

Compact

bone


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.

Spongy

bone

Compact

bone


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).

Proximal

epiphysis

Diaphysis

Distal

epiphysis (a)

Articular

cartilage

Spongy bone

Epiphyseal

line

Periosteum

Compact bone

Medullary

cavity (lined

by endosteum)


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

(c)

Endosteum

Yellow bone

marrow

Compact bone

Periosteum

Perforating

(Sharpey’s) fibers

Nutrient

arteries



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).

(b)

Articular

cartilage

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



Proximal

epiphysis

Diaphysis

Distal

epiphysis (a)

Articular

cartilage

Spongy bone

Epiphyseal

line

Periosteum

Compact bone

Medullary

cavity (lined

by endosteum)



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



Proximal

epiphysis

Diaphysis

Distal

epiphysis (a)

Articular

cartilage

Spongy bone

Epiphyseal

line

Periosteum

Compact bone

Medullary

cavity (lined

by endosteum)


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 continues into medullary cavity containing marrow

Blood vessel

Compact bone

Central (Haversian) canal

Perforating (Sharpey’s) fibers

Periosteum

Periosteal blood vessel

Osteon (Haversian system)

Lamellae

(a)


Microscopic Anatomy of Bone


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

rings


Figure 5.4b Microscopic structure of compact bone.

Lamella

Osteocyte

Canaliculus Lacuna


(b)


Figure 5.4c Microscopic structure of compact bone.

Osteon

Interstitial

lamellae

Lacuna


(c)


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

Canaliculus Lacuna


(b)


Bone Components

Organic parts of the matrix make bone flexible

Calcium salts deposited in the matrix make bone

hard


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.

Hyaline

cartilage

New center of

bone growth

Medullary

cavity

Bone starting

to replace

cartilage

Hyaline

cartilage

model

Bone collar

In an embryo In a fetus In a child

Articular

cartilage

Spongy

bone

Epiphyseal

plate

cartilage

New bone

forming

Growth

in bone

width

Growth

in bone

length

Invading

blood

vessels

New bone

forming

Epiphyseal

plate cartilage



Two major phases of ossification in long bones

1. 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 in

length because:

1

2

1

2 3

3

4

Growing shaft is

remodeled as:

Bone growth Bone remodeling

Articular cartilage

Epiphyseal plate

Bone is

resorbed here.

Bone is added

by appositional

growth here.

Bone is

resorbed here.

Cartilage

grows here.

Cartilage

is replaced

by bone here.

Cartilage

grows here.

Cartilage

is replaced by

bone 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

1

External

callus

Internal

callus

(fibrous

tissue and

cartilage)

New

blood

vessels

Spongy

bone

trabecula

Hematoma

forms.

2 3 Fibrocartilage

callus forms.

Bony callus

forms.

Bone

remodeling

occurs.

Bony

callus of

spongy

bone

Healed

fracture

4


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.

Skull

(a) Anterior view

Thoracic

cage

Vertebral

column

(ribs and

sternum)

Sacrum

Facial bones

Cranium

Clavicle

Scapula

Sternum

Rib Humerus

Vertebra Radius Ulna

Femur Patella

Tibia

Fibula

Tarsals Metatarsals Phalanges

Carpals

Phalanges

Metacarpals


Figure 5.8b The human skeleton.

(b) Posterior view

Bones of

pectoral

girdle

Upper

limb

Bones of

pelvic

girdle

Lower

limb

Cranium

Clavicle

Scapula

Rib Humerus


Carpals

Phalanges

Metacarpals Femur

Tibia

Fibula


Concept Link


The Skull

Two sets of bones

1. 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

joint


The Skull

8 cranial bones protect the brain

1. 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 suture

Occipital bone

Zygomatic process

External acoustic

meatus Mastoid process

Styloid process

Mandibular ramus

Frontal bone

Sphenoid bone

Ethmoid bone

Lacrimal bone

Nasal bone

Zygomatic bone

Maxilla

Alveolar processes

Mandible (body)

Mental foramen


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

Sphenoid

bone

Temporal bone

Internal

acoustic meatus

Parietal bone

Occipital bone

Foramen magnum

Frontal bone

Ethmoid

bone

Cribriform plate

Crista galli

Optic canal

Sella turcica

Foramen 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

Hard

palate

Zygomatic bone

Temporal bone

(zygomatic process)

Vomer

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 bone

Lacrimal bone

Zygomatic bone

Maxilla

Frontal bone

Superior orbital

fissure

Temporal bone

Optic canal

Middle nasal concha

of ethmoid bone

Vomer

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

Sphenoidal

sinus

Maxillary

sinus

(a) Anterior view


Figure 5.13b Paranasal sinuses.

Frontal sinus

Ethmoid sinus

Sphenoidal

sinus

Maxillary

sinus

(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

Body


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

Parietal

bone

Posterior fontanel

(a)

Anterior

fontanel

Occipital

bone


Figure 5.15b The fetal skull.

Parietal bone

Posterior

fontanel

Anterior fontanel

Sphenoidal

fontanel

Frontal

bone

Temporal bone

Occipital

bone

Mastoid

fontanel


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

back



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

Coccyx

4 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.

Lamina Posterior

Vertebral

arch Transverse

process

Spinous

process

Vertebral

foramen

Body

Anterior

Pedicle

Superior

articular

process

and

facet


Figure 5.20a Regional characteristics of vertebrae.

Transverse

process

(a) ATLAS AND AXIS

Posterior

arch

Superior view of axis (C2)

Anterior arch

Superior view of atlas (C1)

Transverse

process

Spinous process

Dens

Body

Facet on

superior

articular

process


Figure 5.20b Regional characteristics of vertebrae.

(b) TYPICAL CERVICAL VERTEBRAE

Right lateral view

Spinous process Facet on

superior

articular

process

Vertebral

foramen

Transverse

process Superior view

Body

Facet on inferior

articular process

Transverse

process

Superior articular

process

Spinous

process


Figure 5.20c Regional characteristics of vertebrae.

(c) THORACIC VERTEBRAE

Right lateral view

Transverse

process

Body

Body

Spinous process

Facet

for rib

Vertebral

foramen

Facet on

transverse

process Spinous

process

Costal facet

for rib

Superior view

process

Facet on

superior

articular

Facet on

superior

articular

process


Figure 5.20d Regional characteristics of vertebrae.

(d) LUMBAR VERTEBRAE

Right lateral view

Transverse

process

Vertebral

foramen

Facet on

superior

articular

process Body

Body Superior

articular

process

Spinous

process Facet on inferior

articular process

Superior view

Spinous process


Figure 5.21 Sacrum and coccyx, posterior view.

Ala

Sacrum

Coccyx Sacral

hiatus

Posterior

sacral

foramina

Median

sacral

crest

Body

Auricular

surface

Superior

articular

process Sacral

canal


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

True

ribs

(1–7)

False

ribs

(8–12)

(a)

Floating

ribs (11, 12)

L1

vertebra Costal cartilage

Intercostal

spaces

T1 vertebra

Jugular notch

Manubrium

Sternal angle

Body

Xiphisternal

joint

Xiphoid

process

Sternum


Figure 5.22b The bony thorax (thoracic cage).

Jugular

notch

Sternal

angle

Heart

Xiphisternal

joint

T2

T3

T4

T9

(b)


The Appendicular Skeleton

Composed of 126 bones

Limbs (appendages)

Pectoral girdle

Pelvic girdle


Figure 5.8a The human skeleton.

Skull

(a) Anterior view

Thoracic

cage

Vertebral

column

(ribs and

sternum)

Sacrum

Facial bones

Cranium

Clavicle

Scapula

Sternum

Rib Humerus


Femur Patella

Tibia

Fibula

Tarsals Metatarsals Phalanges

Carpals

Phalanges

Metacarpals


Figure 5.8b The human skeleton.

(b) Posterior view

Bones of

pectoral

girdle

Upper

limb

Bones of

pelvic

girdle

Lower

limb

Cranium

Clavicle

Scapula

Rib Humerus


Carpals

Phalanges

Metacarpals Femur

Tibia

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

Clavicle Acromio-

clavicular joint

(a) Articulated right shoulder (pectoral)

girdle showing the relationship to

bones of the thorax and sternum


Figure 5.23b Bones of the shoulder girdle.

Inferior view

(b) Right clavicle, superior and

inferior views

Posterior

Acromial end

Anterior

Sternal

(medial)

end

Acromial

(lateral) end

Superior view

Anterior

Posterior

Sternal end


Figure 5.23c Bones of the shoulder girdle.

Suprascapular notch

Superior

angle

Spine

Medial

border

Lateral border

Coracoid process

Acromion

Glenoid cavity

at lateral angle

(c) Right scapula, posterior aspect


Figure 5.23d Bones of the shoulder girdle.

Suprascapular notch Acromion

Coracoid

process

Glenoid

cavity

Superior border

Superior

angle

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.

Greater

tubercle

(a)

Lesser

tubercle

Head of

humerus

Anatomical

neck Intertubercular

sulcus

Deltoid

tuberosity

Medial

epicondyle

Trochlea

Radial

fossa Coronoid

fossa

Capitulum


Figure 5.24b Bones of the right arm and forearm.

(b)

Head of

humerus

Anatomical

neck Surgical

neck

Radial

groove

Deltoid

tuberosity

Olecranon

fossa

Lateral

epicondyle

Medial

epicondyle

Trochlea



The forearm has two bones

1. Ulna—medial bone in anatomical position


Coronoid process and olecranon articulate with the

humerus

2. Radius—lateral bone in anatomical position


Head articulates with the capitulum of the humerus


Figure 5.24c Bones of the right arm and forearm.

(c)

Head

Neck

Radial

tuberosity

Radius

Trochlear

notch

Olecranon

Coronoid

process

Proximal

radioulnar

joint

Ulna

Inter-

osseous

membrane

Ulnar

styloid

process Distal

radioulnar joint

Radial

styloid

process



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

Ulna

Trapezium

Trapezoid

Scaphoid

Capitate

Radius

1

2 3 4 5


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.

Ilium

Pubis

Ischium

(a)

Coxal bone

(or hip bone) Sacrum

Coccyx

Pubic arch

Iliac crest

Sacroiliac

joint

Pelvic brim

Ischial spine

Acetabulum

Pubic symphysis


Figure 5.26b The bony pelvis.

Ilium

Iliac crest

Anterior superior

iliac spine

Anterior inferior

iliac spine

Acetabulum

Body of pubis

Pubis

Inferior pubic

ramus

Obturator

foramen

Ala

Posterior

superior

iliac spine

Posterior

inferior

iliac spine

Greater sciatic

notch

Ischial 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 of

true

pelvis

Pelvic brim

False pelvis

Inlet of

true

pelvis

Pelvic brim

(c)

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


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.

Neck

Inter-

trochanteric

line

Lesser

trochanter

(a)

Lateral

condyle

Patellar

surface

Head


Figure 5.27b Bones of the right thigh and leg.

Lesser

trochanter

Gluteal

tuberosity

Greater

trochanter

Inter-

trochanteric

crest

(b)

Lateral

condyle

Head

Intercondylar

fossa

Medial

condyle



The lower leg has two bones

1. Tibia—shinbone; larger and medially oriented


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.

Intercondylar

eminence

Lateral

condyle

Head

Proximal

tibiofibular

joint

Medial

condyle

Tibial

tuberosity

Interosseous

membrane

Anterior

border

Tibia

Medial

malleolus

Distal

tibiofibular

joint

Lateral

malleolus (c)

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.

Medial

cuneiform

Tarsals:

Phalanges:

Metatarsals

Tarsals:

Intermediate

cuneiform

Navicular

Talus

Distal

Middle

Proximal

Lateral

cuneiform

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 longitudinal

arch


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.

Fibrous

connective

tissue

(a) Suture

Fibrous joints


Figure 5.30b Types of joints.

(b) Syndesmosis

Tibia

Fibula

Fibrous

connective

tissue

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


(c) Synchondrosis

Hyaline

cartilage

Sternum


Figure 5.30d Types of joints.

(d) Symphysis

Vertebrae

Fibro-

cartilage



Figure 5.30e Types of joints.

(e) Symphysis

Pubis

Fibro-

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

Articular

capsule

Synovial joints


Figure 5.30g Types of joints.

(g) Uniaxial joint

Ulna

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

Ulna

Radius

Articular

capsule


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 of

scapula

Ligament

Bursa

Ligament

Tendon

sheath

Tendon of

biceps muscle

Joint cavity

containing

synovial fluid

Articular

(hyaline)

cartilage

Synovial membrane

Fibrous layer of the

articular capsule

Humerus


Figure 5.32a Types of synovial joints.

(f)

(a) Plane joint

Nonaxial Uniaxial Biaxial Multiaxial

(c)

(a)

(e)

(d)

(b)


Figure 5.32b Types of synovial joints.

(f)


(c)

(a)

(e)

(d)

(b)

Humerus

Ulna

(b) Hinge

joint


Figure 5.32c Types of synovial joints.


(f)

(c)

(a)

(e)

(d)

(b) (c) Pivot joint

Ulna

Radius


Figure 5.32d Types of synovial joints.


(f)

(c)

(a)

(e)

(d)

(b) Metacarpal Phalanx

(d) Condylar joint


Figure 5.32e Types of synovial joints.


(f)

(c)

(a)

(e)

(d)

(b) (e) Saddle joint

Carpal Metacarpal #1


Figure 5.32f Types of synovial joints.


(f)

(c)

(a)

(e)

(d)

(b)

Head of

humerus

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

birth


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.

Frontal

bone

of skull

Parietal

bone

Occipita

bone

Clavicle

Scapula

Mandible

Radius

Ulna

Humerus

Femur

Tibia

Ribs

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

(a)


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

(b)

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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