Axial Skeleton (160)

Bones of the:

Skull

Throax

Vertebral Column

Appendicular Skeleton (80)

Bones of the:

Limbs

 Girdles

attach to the Axial Skeleton

Functions of the Skeletal System

Support- support for body, attachment for soft tissue

Storage of Minerals- calcium and phosphate

Blood Cell Production

Protection- surrounds delicate tissues and organs

Leverage- work with skeletal muscles to move body

6 Categories of Bones

Flat Bones- thin, roughly parallel surfaces

Sutural Bones- irregular bones formed bewteen cranial bones

Long Bones- relatively long and slender

Irregular Bones- complex shapes

Sesamoid Bones- small, flat, and somewhat shaped like a sesame seed

Short Bones- small and boxy

Skull Surface Features

Canal or Meatus- large passageway

Process- projection or bump

Sinus- chamber within bone, usually filled with air

Foramen- small, rounded passageway

Fissure- elongated cleft or gap

Humerus Surface Features

Head- expanded proximal end that forms part of joint

Tubercle- small, rounded projection

Sulcus- deep, narrow groove

Tuberosity- small, rough projection; may occupy broad area

Diaphysis- shaft; elongated body

Trochlea- smooth, grooved articular process

Condyle- smooth, rounded articular process

Femur Surface Features

Tronchanter- large, rough projection

Head

Neck- narrow connection bewteen head and diaphysis

Diaphysis

Facet- small, flat articular surface

Condyle

Pelvis Surface Features

Crest- prominent ridge

Fossa- shallow depression or recess

Line- low ridge; more delicate than crest

Spine- pointed or narrow process

Ramus- extension that makes and angle with the rest of the structure

4 Bone Cell Types

Osteocytes

Osteoblasts

Osteoprogenitor

Osteoclasts

Long Bone Features

Epiphysis- consists largely of spongy bone, outer covering of compact bone, articular cartilage

Metaphysis

Diaphysis- contains medullary cavity (marrow)

Periosteum Features

Smaller Blood Vessels- supply superficial osteons

Lymphatic Vessels- collect lymph from bone and osteons

Sensory Nerves- innervate diaphysis, medullary cavity, and epiphyses

Bone Matrix Components

Collagen Fibers- provides flexibility, accounts for 1/3 of bone weight

Calcium Phosphate- accounts for 2/3 of bone weight, interacts with calcium hydroxide to form crystals of hydroxyapatite

Compact Bone

Functional Unit- Osteon

organized concentric lamellae around a central canal

canaliculi connect lacunae with each other and central canal

strong along its length

Osteocytes

mature bone cells that cannot divide

most numerous bone cell type

maintain protein and mineral content of adjacent matrix

occupy lacunae

Osteoblasts

produce new bony matrix (osteogenesis or ossification)

become osteocytes once surrounded by bony matrix

Osteoprogenitor Cells

mesenchymal (stem) cells that produce cells that differentiate into osteoblasts

important in fracture repair

location: inner lining of periosteum, lines endosteum in medullary cavity, lines passageways containing blood vessels 

Osteoclasts

remove and remodel bone matrix

giant cells with 50+ nuclei

release acids and proteolytic enzymes to dissolve matrix and release stored minerals (osteolysis)

Pituitary Growth Failure

reduction in growth hormone leads to reduced epiphyseal crtilage activity and short bones 

rare due to treatment with synthetic growth hormone

Achondroplasia

epiphyseal cartilage grows unusually slow

limbs are short

trunk is normal size 

Marfan Syndrome

excessive cartilage formation at epiphyseal cartilage

causes long, slender limbs

other connective tissue abnormalities cause cardiovascular issues

Gigantism

overproducion of growth hormone before puberty

Fibrodysplasia Ossificans Progressiva (FOP)

gene mutation that causes bone deposition around skeletal muscles

hetertopic/ectopic: bones developing in unusual places 

Acromegaly

growth hormone levels rise after epiphyseal plates close

bones get thicker, especially those in the jaw, hands, and face

Fracture

crack or break due to extreme mechanical stress

most heal as long as the blood supply and cellular parts of the periosteum and endosteum survive 

Steps of Fracture Repair

large blood clot (fracture hematoma) develops

calluses form

-internal calluses: network of spongy bone uniting inner edges

-external calluses: cartilage and bone stabilizes outer edges

calluses replaced and dead bone removed

remodeling of healed bone