The Skeletal System

Parts of the skeletal system

Bones (skeleton), Joints, Cartilages, Ligaments

Two subdivisions of the skeleton

Axial and Appendicular Skeleton

Support the body, Protect soft organs, Attached skeletal muscles allow movement, Store minerals and fats, Blood cell formation (hematopoiesis)

Bones

protect brain and spinal cord

Skull and vertebrae

protects thoracic cavity organs

Rib cage

What are the minerals and fats stored in the Bones

Calcium and phosphorus, Fat in the internal marrow cavity

What other term is the Blood cell formation

hematopoiesis

The adult skeleton has ___ bones

206

Two basic types of osseous (bone) tissue

Compact and Spongy Bone

A type of Osseous(bone) tissue: Dense, smooth, and homogeneous

Compact bone

A type of Osseous(bone) tissue: Small needlelike pieces of bone and Many open spaces

Spongy bone

Bones are classified on the basis of shape into four groups

Long, flat, short, irregular

Examples of Long Bone

humerus and femur

Examples of Flat bone

sternum, ribs, Most bones of the skull

Examples of Irregular bone

Vertebrae, hip bones

Examples of Short bone

talus, tarsals, carpals

• Typically longer than they are wide

• Shaft with enlarged ends

• Contain mostly compact bone; spongy bone at ends

• All of the bones of the limbs (except wrist, ankle, and

• kneecap bones)

Long bones

• Thin, flattened, and usually curved

• Two thin layers of compact bone sandwich a layer of

• spongy bone between them

Flat bones

• Generally cube-shaped

• Contain mostly spongy bone with an outer layer of

  compact bone

• Sesamoid bones are a type of short bone that form

  within tendons (patella)

Short bones

are a type of short bone that form within tendons (patella)

Sesamoid bones

• Irregular shape

• Do not fit into other bone classification categories

Irregular bones

Bones are organs, so they not only contain osseous tissue but also other connective tissues like:

Fibrous, cartilage, adipose, and blood

Long bone anatomy

Diaphysis (shaft) and Periosteum

Long bone anatomy:

• Makes up most of bone’s length

• Composed of compact bone

Diaphysis (shaft)

Long bone anatomy:

• Outside covering of the diaphysis

• Fibrous connective tissue membrane

• Perforating (Sharpey’s) fibers secure periosteum tonunderlying bone

Periosteum

These fibers secure periosteum to underlying bone

Perforating (Sharpey’s)

Long bone anatomy: Composed mostly of spongy bone enclosed by thin layer of compact bone

Epiphysis (ends)

Long bone anatomy:

• Covers the external surface of the epiphyses

• Made of hyaline cartilage

• Decreases friction at joint surfaces

Articular cartilage

Long bone anatomy:

• Remnant of the epiphyseal plate

• Seen in adult bones

Epiphyseal line

Long bone anatomy:

• Flat plate of hyaline cartilage seen in young, growing bone

• Causes lengthwise growth of a long bone

Epiphyseal plate

Long bone anatomy:

▪ Lines the inner surface of the shaft

▪ Made of connective tissue

Endosteum

Long bone anatomy:

▪ Cavity inside the shaft

▪ Contains yellow marrow (mostly fat) in adults

▪ Contains red marrow for blood cell formation in infantsnuntil age 6 or 7

Medullary cavity

▪ Sites of attachments for muscles, tendons, and ligaments

▪ Passages for nerves and blood vessels

Bone markings

Categories of bone markings:

• grow out from the bone surface

• Terms often begin with “T”

Projections or processes

Categories of bone markings:

• Indentations

• Terms often begin with “F”

Depressions or cavities

Projections that are sites of muscle and ligament attachment: Large, rounded projection; may be roughened

Tuberosity

Projections that are sites of muscle and ligament attachment: Narrow ridge of bone; usually prominent

Crest

Projections that are sites of muscle and ligament attachment: Very large, blunt, irregularly shaped process (the only examples are on the
femur)

Trochanter

Projections that are sites of muscle and ligament attachment: Narrow ridge of bone; less prominent than a crest

Line

Projections that are sites of muscle and ligament attachment: Small, rounded projection or process

Tubercle

Projections that are sites of muscle and ligament attachment: Raised area on or above a condyle

Epicondyle

Projections that are sites of muscle and ligament attachment: Sharp, slender, often pointed projection

Spine

Projections that are sites of muscle and ligament attachment: Any bony prominence

Process

Projections that help to form joints: Bony expansion carried on a narrow neck

Head

Projections that help to form joints: Smooth, nearly flat articular surface

Facet

Projections that help to form joints: Rounded articular projection

Condyle (kon'dil)

Projections that help to form joints: Armlike bar of bone

Ramus (ra'mus)

Depressions and openings For passage of blood vessels and nerves: Furrow

Groove

Depressions and openings For passage of blood vessels and nerves: Narrow, slitlike opening

Fissure

Depressions and openings For passage of blood vessels and nerves: Round or oval opening through a bone

Foramen

Depressions and openings For passage of blood vessels and nerves: Indentation at the edge of a structure

Notch

Depressions and openings For passage of blood vessels and nerves: Canal- or tunnel-like passageway

Meatus

Depressions and openings For passage of blood vessels and nerves: Cavity within a bone, filled with air and lined with mucous membrane

Sinus

Depressions and openings For passage of blood vessels and nerves: Shallow, basin-like depression in a bone, often serving as an articular surface

Fossa

Microscopic anatomy of spongy bone: Composed of small, needlelike pieces of bone called ____ and ___

trabeculae, open spaces

Microscopic anatomy of spongy bone: ___are filled by marrow, blood vessels, and nerve

Open Spaces

Microscopic anatomy of compact bone: Mature bone cells situated in bone matrix

Osteocytes

Microscopic anatomy of compact bone: Cavities in bone matrix that house osteocytes

Lacunae

Microscopic anatomy of compact bone: Concentric circles of lacunae situated around the central (Haversian) canal

Lamellae

Microscopic anatomy of compact bone:

• Opening in the center of an osteon (Haversian system)

• Runs lengthwise through bone

• Carries blood vessels and nerves

Central (Haversian) canal

Microscopic anatomy of compact bone:

• A unit of bone containing central canal and matrix rings

• Structural and functional unit of compact bone

Osteon (Haversian system)

Microscopic anatomy of compact bone:

• Tiny canals

• Radiate from the central canal to lacunae

• Form a transport system connecting all bone cells to a nutrient supply

Canaliculi

Microscopic anatomy of compact bone:

• Canal perpendicular to the central canal

• Carries blood vessels and nerves

Perforating (Volkmann’s) canal

___are relatively lightweight and resists tension and other forces

Bones

___of the bone make bone flexible and have great tensile strength

Organic parts (collagen fibers)

___deposited in the bone make bone hard to resist compression

Calcium salts

is the process of bone formation

Ossification

Occurs on hyaline cartilage models or fibrous membranes

Bone formation and growth

1. Osteoblasts (bone-forming cells) cover hyaline cartilage model with bone matrix

2. In a fetus, the enclosed cartilage is digested away, opening up a medullary cavity

two major phases of ossification in long bones

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

Articular cartilages and Epiphyseal plates

___is formed continuously on external face of these two cartilages

New cartilage

___is broken down and replaced by bony matrix

Old cartilage

• Bones grow in width

• Osteoblasts in the periosteum add bone matrix to the outside of the diaphysis

• Osteoclasts in the endosteum remove bone from the inner surface of the diaphysis

Appositional growth

___is controlled by hormones, such as growth hormone and sex hormones

Bone growth

___ in the periosteum add bone matrix to the outside of the diaphysis

Osteoblasts

___in the endosteum remove bone from the inner surface of the diaphysis

Osteoclasts

___ in the blood determines when bone matrix is to be broken down or formed

Calcium ion level

________ on the skeleton determines where bone matrix is to be broken down or formed

Pull of gravity and muscles

Calcium ion regulation:

• Released when calcium ion levels in blood are low

• Activates osteoclasts (bone-destroying cells)

• Osteoclasts break down bone and release calcium ions into the blood

Parathyroid hormone (PTH)

____(high blood calcium levels) prompts calcium storage to bones by osteoblasts

Hypercalcemia

break in a bone

Fracture

Types of bone fractures

Closed/Simple and Open/Compound

Types of bone fractures: is a break that does not penetrate the skin

Closed/Simple

Types of bone fractures: is a broken bone that penetrates through the skin

Open/Compound

Bone fractures are treated by:

reduction and immobilization

What Kind of Reduction: bones are manually coaxed into position by physician’s hands

Closed reduction

What Kind of Reduction: bones are secured with pins or wires during surgery

Open reduction

Healing time of bone Fractures

6–8 weeks

Repair of bone fractures involves four major events: (blood-filled swelling, or bruise) is formed

Hematoma

Repair of bone fractures involves four major events: This forms Cartilage matrix, bony matrix, collagen fibers splint the broken bone

Fibrocartilage callus

Repair of bone fractures involves four major events:

• This replaces the fibrocartilage callus

• Where Osteoblasts and osteoclasts migrate in

Bony callus

Repair of bone fractures involves four major events: This occurs in response to mechanical stresses

Bone remodeling

Common types of Fractures: Bone breaks into three or more fragments

• Particularly common in older people, whose bones are more brittle

Comminuted

Common types of Fractures: Bone is crushed

• Common in porous bones (i.e., osteoporotic bones of older people)

Compression

Common types of Fractures: Broken bone portion is pressed inward

• Typical of skull fracture

Depressed

Common types of Fractures: Broken bone ends are forced into each other

• Commonly occurs when someone attempts to break a fall with outstretched arms

Impacted

Common types of Fractures: Ragged break occurs when excessive twisting forces are applied to a bone

Spiral

Common types of Fractures: Bone breaks incompletely, much in the way a green twig breaks

• Common in children, whose bones are more flexible than those of adults

Greenstick

Forms the longitudinal axis of the body

Axial Skeleton

Three parts of the Axial Skeleton

Skull, Vertebral column, bony thorax