SKELETAL SYSTEM

Bones and Bone Tissue

Bone Functions

1. Support-framework 2. Protection-skull,

vertebrae, ribcage 3. Movement-levers for

muscles 4. Storage-Ca, other

minerals, fat 5. Blood cell formation-

marrow

Bone Classification Bones are classified according to:

Shape Type of osseous tissue they contain

Types of osseous tissue Compact/dense bone Spongy/cancellous bone

Bone Structure

Shape Flat Bones (sternum, ribs & most of skull)

Thin, flat, usually curved Spongy bone sandwiched between

2 layers of compact bone

Irregular Bones (vertebrae, facial & pelvic

bones Don’t fit into other categories-mostly spongy

bone with a thin layer of compact

Bone Classification (continued) Shape

Long Bones (arms, legs, hands, feet)

mostly compact bones Short Bones (wrist, ankles)

Mostly spongy bone with thin

covering of compact bone

Sesamoid bones (patella)- specialized

short bones formed within a tendon

Bone Structure Long Bones

Diaphysis Compact bone Medullary cavity Contains Yellow bone marrow

Epiphysis Ends of long bone Spongy (cancellous) bone with thin layer of compact Epiphyseal plate/line- place where bone gets longer

in children. Closes after puberty and become epiphyseal line in adults

Bone structure(cont.) Periosteum- Membrane

Covering outside of bone Endosteum- surrounds

medullary cavity. Contains

osteoblasts and osteoclasts

Articular Cartilage- articulation=joint (place where two bones meet). Ends of bones in joints area covered with cartilage

Bone Structure (continued)

Flat Bone “bone sandwich” Surface covered by

periosteum Internal cavities

lined with endosteum

periosteum

endosteum

Spongy bone

Markings on Bones Process--any bump or projection on a

bone Types of processes

Sites of muscle attachment Tuberosity-large rough process Trochanter- very large, rough process at the

femur Crest-prominent ridge (iliac crest)

Markings on Bones continued

Types of processes(continued) Processes that help make joints

Head-end of epiphysis-with a neck(head of femur)

Condyle-rounded process at a joint(femur or humerus)

Depressions or openings Foramen-round passage for blood

vessels or nerves Sinus –cavity in bone, lined with

mucous membrane, filled with air

Microscopic Bone Structure Basic unit of compact bone = Osteon

Lamellae (hard bony matrix) Haversian canal (central opening) Osteocytes(bone cells) are in lacunae

(pockets) Osteocytes connect by

canaliculi(little canals)

Microscopic Bone Structure (continued)

Cancellous (spongy) bone—no osteons Matrix—network (trabeculae) form in

response to stress Woven around

blood vessels

Bone Development Osteogenesis/Ossification= bone

formation and growth 2 types

Intramembranous ossification-bone forms from fibrous membrane. Less common. Found in flat bone and irregular bone

Endochondral ossification- bone forms from cartilage. Long and Short bones. Most bones form this way.

Bone Growth Grow in length at epiphyseal plate

Bones stop growing longer at about Age 18 in women Age 21 in men

Bones grow in diameter by appositional growth New osteons form on outer

edge of bone (osteoblasts) Osteoclasts break down bone on the

inner edge

Bone Growth

Hormones and bone growth Hormones control bone growth during childhood Growth hormone-from pituitary gland

Too much- giantism Too little - dwarfism

Thyroid hormones- work with growth hormone to keep growth at epiphyseal plate normal

Sex hormones at puberty lead to a growth spurt

Stresses on Bones

Stress on bones creates a tiny electrical charge that attracts osteoblasts to the site of the stress

Stresses on Bones Because of stresses on bones

Long bones are thickest in middle of shaft Curved bones thickest where they are most

likely to buckle Trabeculae of spongy bone form along

stress lines (for strength) Large processes grow where heavy, active

muscles attach(weightlifters) Unstressed bones shrink-ex: bedridden

paralyzed

Fractures

Fracture=Broken bone 8 Types

1. Closed/simple-bone is broken but skin is intact

Fractures

2. Open/compound- broken ends of the bone protrude through the skin. More serious injury. May lead to infection

Fractures

3. Comminuted- many fragments. More common in the elderly

Fractures 4. Compression- bone is

crushed. Common in osteoporosis Often in vertebrae

Fractures

5. Depressed-broken part of bone is pressed in.

Fractures

6. Impacted-broken bone ends are forced into one another Arms /wrists /shoulders- when one

tries to break a fall with one’s hands Legs/hips- with falls when a person

lands on their feet

Fractures

7. Spiral- ragged break that happens when excessive twisting is involved

Fractures

8. Greenstick- bone breaks incompletely (as a green twig) Occurs most often in children because

their bones are more flexible (not completely ossified)

Fracture Repair Reduction= realignment of broken

bone ends Closed- no surgery, external manipulation Open- requires surgery. Bone ends are

brought together with pins, plates, wires

After reduction a cast or traction are used to immobilize the site

Healing for a simple fracture is 6-8 weeks- longer for larger bones or in elderly

Fracture Repair

Repair steps Hematoma formation-causes damaged bone

cells to die. The area becomes swollen, reddened and painful

Cartilage callus forms-allows blood vessels to grow, phagocytes clean up dead cells. Fibroblasts and osteoblasts migrate to area to begin reconstruction

Bony callus forms- - spongy/cancellous bone Remodeling –takes months to complete.

Excess bone tissue is removed by osteoclasts

Bone Disorders

Osteomalacia- soft bones. Bones are not adequately mineralized. Bones bend and deform causing a lot of pain Linked to Vit. D deficiency Rickets- Vit. D deficiency in

children- bow legs Head rib cage and pelvis often

deformed

Bone Disorders Osteoporosis-bone mass decreases

More porous and lighter Compression of the spine are not uncommon Fractures at the neck of femur common (hip

fractures) Highest risk- women over 50 (after Menopause)

Estrogen deficiency Diet Decreased activity

Bone Disorders Paget’s Disease- excessive and

abnormal bone formation and breakdown Bones get soft and thick leading to

increased deformities and irregular thickening

Seen in those over 40 Affects spine,femur,

pelvis and skull

Bone Development

At birth most long bones are ossified By age 25 almost all bones are

completely ossified Bone formation vs. Bone breakdown Bone mass differences by race Preventing bone loss with age

Axial Skeleton 206 bones in entire

skeleton Axial skeleton—80 bones

(skull, vertebral column, ribcage)

Axial skeleton functions1. Framework to protect &

support organs2. Attachments for muscles

that move head, neck, and torso

Appendicular Skeleton

How many bones are there in the entire skeleton?

How many bones in the axial skeleton?

How many does that leave in the appendicular skeleton?

What is the appendicular skeleton?

Parietal bone

Occipital bone

Frontal bone

Nasal bone

Maxilla

Mandible

Zygomatic bone

Sphenoid bone

Temporal boneMastoid process

Styloid Process

External Auditory Meatus

Occipital bone

Temporal bone

Foramen magnum

Occipital condyles

Styloid process

Zygomatic arch

Frontal bone

Supra-orbital ridge

Zygomatic bone

Maxilla

Mandible

Alveolar process

OrbitTemporal bone

Zygomatic boneMaxilla

Parietal bone

Sinuses Hollow places in skull

Lined with mucous membrane Filled with air

Functions: 1. Make skull lighter 2. Lined with mucous membrane

Mucous functions: 1. warms, adds moisture to incoming air 2. traps particles so they are swallowed

AtlasAxis

Cervical Vertebrae C1-7

Thoracic Vertebrae T1-12

Lumbar Vertebrae L1-5

Sacrum

Coccyx

True Ribs (1-7)

False Ribs (8-12)

Floating Ribs (11, 12)

Abnormal Spinal Curvatures

Scoliosis

Lordosis

Kyphosis

sternum

Parietal Frontal

Occipital MaxillaMandible

Clavicle Scapula Sternum

Acromion Process

RibcageHumerus

Vertebral Column

Coxa IliumPubisIschium

RadiusSacrumUlna

CarpalsMetacarpals

Phalanges

Iliac Crest

Ischial tuberosity

Symphysis Pubis

Trochanter

Key:

Black = Axial Skeleton

Red = Pectoral Girdle

Blue = Pelvic Girdle

Femur

Patella

Tibia

Fibula

Talus TarsalsMetatarsals Phalanges

Coccyx

Skeletal Development At 4 weeks after conception, limb buds

form At 5 weeks cartilage appears around

neural tube At 8 weeks ossification begins At birth—significant cartilage at both ends

of long bones and in the pelvis At birth—bones of skull are not fused

Fontanelles, sutures

Individual Variations

Skeletal remains can often be identified because of variations among races and between sexes

There are racial differences in the skull and pelvis

Muscle development can be determined by bone mass and the size of processes

Age can be determined by epiphyseal plates (closed in adults)

Skeletal Differences by Sex

Male Generally heavier,

rougher bones Sloping forehead Larger skull &

mandible Larger teeth Pelvis—narrow, heavy,

heartshaped, angle below symphysis < 90o

Female Lighter, smoother

bones More vertical forehead

Pelvis—broad, light, oval, angle below symphysis >100o

ARTICULATIONS

Articulation= the point at which 2 bones meet

Articulation functions Hold bones together Allow movement

TYPES OF ARTICULATIONS

1. Synarthroses Examples: sutures in skull, gomphosis

2. Amphiarthroses Examples: joints between ribs 2-10 and

sternum, symphysis 3. Diarthroses

Examples: joints of limbs

DIARTHROSES

Synovial joints Articular capsule Synovial fluid

The more movable a joint is, the weaker and less stable it is.

MOVEMENTS ALLOWED BY ARTICULATIONS Gliding Flexion/Extension

Dorsiflexion Plantar flexion Hyperextension

Abduction/Adduction Circumduction Rotation Supination/Pronation Inversion/Eversion Protraction/Retraction Elevation/Depression

INJURIES/DISORDERS

Sprain-ligaments around joint are stretched or torn

Cartilage injuries-fall or twisting with high pressure

Dislocation- bones forced out of normal position in a joint

Arthritis Osteoarthritis Rheumatoid arthritis

TYPES OF DIARTHROSES

Hinge-allows flexion and extension Pivot-allows rotation Saddle joint- allows broad range of

movement Ball and socket- allows broad range of

movement