skeletol system

Compact bone

osteons, strong, outer layer, dense/hard

spongy bone

trabeculae, found inside bones, lightweight

Epiphysis

end of long bones

Diaphysis

shaft / mid part of bone

Medullary cavity

Hollow space inside the bone

red bone marrow

Makes blood cells and platelets (child)

Yellow bone marrow

stores fat (adult)

Epiphyseal plate

made of cartilage that allows the bone to grow longer (child), red bone marrow

Epiphyseal line

Remains after the growth plate closes The bone can no longer grow longer (adult), yellow bone marrow

Hematopoiesis

makes blood cells

Periosteum

double layered

endosteum

covers inside of bone

Fibrous layer

dense ireg ct

Osteogenic layer

contains osteoblasts and osteoclasts

Osteogenic cells

Cells that develop into osteoblasts

Osteoblasts

Build new bone (secrete)

Osteocytes

mature bone

Osteoclasts

breaks down bone

Lamellae

layer of bone tissue

Central (Haversian) canal

contains blood vessels and nerves

Perforating (Volkmann's) canals

connacts bone vessels and nerves to canal

Lacunae

Small spaces that hold osteocytes

Canaliculi

Tiny channels connecting lacunae

Prenatal ossification

bone making before birth

Postnatal ossification

bone growth after birth

Intramembranous ossification (prenatal)

Bone forms directly from connective tissue membrane and results in formation of membrane bones (cranial / clavical)

Endochondral ossification (prenatal)

from hyaline cartilage produced by chondroblasts (all bones in the body expect cranial and cartilage)

Mesenchymal cells

Early cells that can develop into bone-forming cells

Chondroblasts

Cells that make cartilage

Chondrocytes

Mature cartilage cells

Longitudinal growth

bone grows longer (epiphyseal plates)

Appositional growth

Bone grows wider or thicker (Occurs through bone formation on the outer surface)

Growth (proliferative) zone

Cartilage cells divide and increase in number

Hypertrophic zone

Cartilage cells get bigger

Calcification zone

Cartilage hardens with minerals and cells die

Ossification zone

new bone forms

Resorption zone

Bone is removed to enlarge the medullary cavity

Growth hormone (GH)

Hormone that helps bones grow

Insulin-like growth factors (IGFs)

Help cartilage grow at growth plates

Epiphyseal plate closure

Growth plate closes and bones stop growing longer

Gigantism

Excessive height from too much growth hormone in childhood

Acromegaly

Excessive bone and tissue growth from too much growth hormone in adults

Dwarfism

Very short stature that can result from growth-related problems

Bone resorption

breaking down bone

Osteoporosis

Condition where bones lose density and become weaker

Wolff's law

bone changes in response to stress being put on it

Parathyroid hormone (PTH)

raises blood calcium

Calcitonin

Helps lower blood calcium by promoting bone formation

Active vitamin D

Helps the intestines absorb calcium and phosphate

Hypocalcemia

Low blood calcium

Hypercalcemia

High blood calcium

when theres low blood calcium?

PTH is released.

when theres high blood calcium?

calcitonin is released.

Why is growth hormone’s effect on longitudinal bone growth indirect?

does not directly stimulate the cartilage cells in the growth plates. Instead, it stimulates the liver to produce insulin-like growth factors (IGFs). These IGFs stimulate cartilage cell division and growth, allowing the bones to lengthen.

How does the growth spurt after puberty occur

testosterone and estrogen, work with GH.

This increases IGF production.

IGFs stimulate cartilage cells to divide and produce more cartilage at the growth plates. The cartilage is replaced by bone, making long bones longer and increasing height.