The Skeletal System€¦ · Developmental Aspects of the Skeletal System At birth, the skull bones...

PowerPoint® Lecture Slide Presentation

by Patty Bostwick-Taylor,

Florence-Darlington Technical College

PART A5

The Skeletal

System

The Skeletal System

Parts of the skeletal system

Bones (skeleton)

Joints

Cartilages

Ligaments

Two subdivisions of the skeleton

Axial skeleton

Appendicular skeleton

Functions of Bones

Support the body

Protect soft internal organs

Allow movement due to attached skeletal muscles

Storage of minerals (calcium and phosphorus)

and fats in Yellow Marrow

Blood cell production in Red Marrow

Bones of the Human Body

The adult skeleton has 206 bones

Two basic types of bone tissue (composition is identical)

Compact bone

Solid, dense

Found in diaphysis

and external surfaces

Spongy bone (cancellous)

Small needle-like pieces of bone

Lightweight, honeycombed

Found in epiphysis (ends), short bones, and flat bones

Figure 5.2b

Classification of Bones on the Basis of Shape

Figure 5.1

Classification of Bones

Long bones

Typically longer than they are wide

Tubular with articular surface at each end

Contain mostly compact bone

Example:

Femur, Tibia, Fibula

Humerus, Radius, Ulna

Figure 5.1a

Short bones

Generally cube-shape

Contain mostly spongy bone

Example:

Carpals

Tarsals

Metacarpals

Metatarsals

Phalanges

Figure 5.1b

Flat bones

Thin, flattened, and usually curved

Two thin layers of compact bone surround a

layer of spongy bone

Example:

Sternum

Scapula

Figure 5.1c

Irregular bones

Irregular shape

Do not fit into other bone classification

categories

Compact in nature

Example:

Vertebrae

Hip bones

Facial Skeleton

Figure 5.1d

Sesamoid Bones

Small bones found in joints where there are

tendons

Example:

Patella

Anatomy of a Long Bone

Diaphysis

Composed of compact bone

Epiphysis

Ends of the bone

Composed mostly of spongy bone

Contains red marrow

Figure 5.2a

Periosteum

Outside covering of the diaphysis

Fibrous connective tissue membrane

Arteries

Supply bone cells with nutrients

Figure 5.2c

Articular cartilage

Covers the external surface of the epiphyses

Made of hyaline cartilage

Decreases friction at joint surfaces

Epiphyseal plate

Flat plate of hyaline cartilage seen in young,

growing bone

Epiphyseal line

Remnant of the epiphyseal plate

Seen in adult bones

Figure 5.2a

Medullary cavity

Cavity inside of the shaft

Contains yellow marrow (mostly fat) in adults

Contains red marrow (for blood cell formation)

in infants

Figure 5.2a

Microscopic Anatomy of Bone

Figure 5.3a

Microscopic Anatomy of Bone

Figure 5.3b–c

Types of Bone Cells

Osteocytes—mature bone cells

Osteoblasts—bone-forming cells

Osteoclasts—bone-destroying cells

Break down bone matrix for remodeling and

release of calcium in response to parathyroid

hormone

Bone remodeling is performed by both

osteoblasts and osteoclasts

Formation of the Human Skeleton

In embryos, the skeleton is primarily hyaline

cartilage

During development, much of this cartilage is

replaced by bone

Cartilage remains in isolated areas

Bridge of the nose

Parts of ribs

Joints

Bone Growth (Ossification)

Epiphyseal (growth) plates allow for lengthwise

growth of long bones during childhood

New cartilage is continuously formed

Older cartilage becomes ossified into bone

tissue

Cartilage is broken down

Enclosed cartilage is digested away,

opening up a medullary cavity

Bone replaces cartilage through the action

of osteoblasts

Bone Growth (Ossification)

Bones are remodeled and lengthened until growth

Bones are remodeled in response to two

factors

Blood calcium levels

Pull of gravity and muscles on the

skeleton

Bones grow in width (called appositional

growth)

Long Bone Formation and Growth

Figure 5.4a

Bone starting

to replace

cartilage

Epiphyseal

cartilage

Articular

cartilage

Spongy

In a childIn a fetusIn an embryo

New bone

forming

Growth

in bone

Growth

in bone

length

Epiphyseal

plate cartilage

New bone

forming

vessels

Hyaline

cartilage

New center of

bone growth

Medullary

cavity

Bone collar

Hyaline

cartilage

Long Bone Formation and Growth

Figure 5.4b

PART A5

The Skeletal

System

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 are treated by reduction and immobilization

Common Types of Fractures

Table 5.2

Repair of Bone Fractures

Hematoma (blood-filled swelling) is formed

Break is splinted by fibrocartilage to form a callus

Fibrocartilage callus is replaced by a bony callus

Bony callus is remodeled to form a permanent

Stages in the Healing of a Bone Fracture

Figure 5.5

Hematoma

Externalcallus

Bonycallus ofspongybone

Healedfracture

Newbloodvessels

Internalcallus(fibroustissue andcartilage)

Spongybonetrabecula

Hematoma

formation

Fibrocartilage

callus formation

Bony callus

formation

Bone remodeling

The Axial Skeleton

Forms the longitudinal axis of the body

Divided into three parts

Vertebral column

Bony thorax

The Axial Skeleton

Figure 5.6a

The Axial Skeleton

Figure 5.6b

The Skull

Two sets of bones

Cranium

Facial bones

Bones are joined by sutures

Only the mandible is attached by a freely movable

Human Skull, Lateral View

Figure 5.7

Human Skull, Superior View

Figure 5.8

Human Skull, Inferior View

Figure 5.9

Human Skull, Anterior View

Figure 5.11

Paranasal Sinuses

Hollow portions of bones surrounding the nasal

cavity

Functions of paranasal sinuses

Lighten the skull

Give resonance and amplification to voice

Paranasal Sinuses

Figure 5.10a

Paranasal Sinuses

Figure 5.10b

PART A5

The Skeletal

System

The Fetal Skull

The fetal skull is large compared to the infant’s

total body length

Fontanels—fibrous membranes connecting the

cranial bones

Allow the brain to grow

Convert to bone within 24 months after birth

The Fetal Skull

Figure 5.13a

The Fetal Skull

Figure 5.13b

Fetal Development

ProportionalChanges

The Vertebral Column

The spine has a normal curvature

Primary curvatures are the spinal curvatures

of the thoracic and sacral regions

Present from birth

Secondary curvatures are the spinal

curvatures of the cervical and lumbar regions

Develop after birth

Figure 5.15

Figure 5.16

The Appendicular Skeleton

Composed of 126 bones

Limbs (appendages)

Pectoral girdle

Pelvic girdle

The Appendicular Skeleton

Figure 5.6a

Fibrous Joints

Immovable Joints

Example:

Sutures

Types of Synovial Joints

Figure 5.30a–c

Types of Synovial Joints

Figure 5.30d–f

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

Clinical Forms of Arthritis

Osteoarthritis

Most common chronic arthritis

Probably related to normal aging processes

Rheumatoid arthritis

An autoimmune disease—the immune system

attacks the joints

Symptoms begin with bilateral inflammation of

certain joints

Often leads to deformities

Rheumatoid Arthritis

Clinical Forms of Arthritis

Gouty arthritis

Inflammation of joints is caused by a

deposition of needle-shaped uric acid crystals

from the blood

Can usually be controlled with diet

Sprain

• Ligaments or tendons

reinforcing a joint are damaged

by stretching or are torn away

from the bone.

• Due to lack of good blood

supply, sprains heal slowly and

are extremely painful

Developmental Aspects of the Skeletal System

At birth, the skull bones are incomplete

Bones are joined by fibrous membranes called

fontanels

Fontanels are completely replaced with bone

within two years after birth

Ossification Centers in a 12-week-old Fetus

Figure 5.32

Skeletal Changes Throughout Life

Long bones are formed of hyaline cartilage

Flat bones begin as fibrous membranes

Flat and long bone models are converted to

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 5.33a

Figure 5.33b

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 5.16

Osteoporosis

Bone-thinning disease afflicting

50% of women over age 65

20% 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 5.34

Figure 5.35

The Skeletal System€¦ · Developmental Aspects of the Skeletal System At birth, the skull bones...

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