AP Exam 3 skeletal

Hematopoiesis

blood cell formation, happens in red bone marrow

skeletal system functions

protection, mineral storage, blood cell formation, fat storage, movement, support

arthropods

animals with jointed appendages

hyaline cartilage

makes up articular and costa cartilage, also in non-skeletal system places (respiratory and nasal cartilages) found at ends of bones when forming a joint

bone shapes

long bone, short bone, flat bone, irregular bone, seasmoid bone

long bone

bone is longer than it is wide

bones are

living things- there are nevrous system components and blood supplies

periosteum

covers surface of bone, outer fibrous later and inner layer containing osteoblasts

endosteum

lines inner cavities (medullary cavirty) of bones

medullary cavity

in shaft of long bone- where bone marrow is found

epiphyses

ends of long bone

diaphysis

shaft of long bone

structure of short, flat, irregular, and seasmoid bones

spongy bone surrounded by compact bone

red bone marrow in children

found in all spongy bone and all medullary cavities everywhere

red bone marrow in adults

more restricted than children- axial skeleton and balls of ball and socket koints at shoulders, hips and femurs

red bone marrow function

hematopoiesis

yellow bone marrow function

adipose tissue, fat storage

osteon

Basic structural unit of compact bone; concentric rings around a central canal.

lamellae

Thin layers or rings of bone matrix -circumferential and interstitial

circumferential lamellae

Layers of bone matrix that wrap around the outer and inner surfaces of bone

interstitial lamellae

Incomplete layers of bone matrix found between osteons

central canal (haversian canal)

Channel through an osteon containing blood vessels and nerves

Canaliculi

Tiny channels connecting lacunae; allow nutrients and waste to pass between cells

Lacunae

Small space in the bone matrix where osteocytes are located

Osteocyte

mature bone cell that maintains the bone matrix connected by gap junctions, come from osteoblast cells

How do osteocytes get oxygen and nutrients

Osteocytes are trapped in lacunae, but get nutrients via canaliculi

• nutrients come from blood supply through central channels and diffusion through canaliculi. Osteocytes also communicate via gap junctions

spongy bone components

same as long bone but no central canal

osteogenic cell

stem cell, daughter cells may differentiate into osteoblasts. Found at endosteum and periosteum

Osteoblast

matrix-synthesizing cell responsible for bone growth, “bone builders”, come from osteogenic cells, help to get calcium phosphate from blood

Osteoclast

cells responsible for breaking down matrix (didn’t come from osteogenic cell – these are made in bone marrow)

Bone matrix

Bone is composite material- made of organic and inorganic components

Organic components

1/3 of bone matrix, osteoid (secreted from osteoblasts); ground substance(protein +sugars), collagen (fiber + strength)

Inorganic components

hydroxyapatite; calcium phosphate is from blood via osteoblast action, mineral salts account for 65% of bone mass

bone w/o organic matrix (collagen)

brittle and shatters easily

bone w/o inorganic matrix (minerals)

cannot resist compression, weak bones that cannot bear weight

lack of calcium

from low intake or low absorption (vit D) = bendy bones that don’t resist weight

bone formation

skeleton starts out as cartilage skeleton as fetus and replaced by bone one of two ways

• endochondral ossification (inside cartilage)

  • below skull bones, aslo used by long bones to achieve adult height

• Intramembranous ossification

  • skull and clavicles

endochondral ossification

Hyaline cartilage model is first

Blood vessels come in

Chondrocytes die and are replaced by osteoblasts

Osteoblasts become osteocytes as they are trapped by the ECM

Osteoclasts also at work (e.g.enlarge medullary cavity)

longitudinal bone growh

at epishyseal plates, regulated by several hormones, mimics endochonral ossification (b/c cartilage 1st then replaced with bone), organized array of proliferating, enlarging and mineralizing chondrocytes lead bone formation and growth, new bone is added toward medullary cavity

intramembranous ossification

mesenchymal cells at site of bone formation differentiate into osteoblasts

fontanelles

soft spots on skull of newborn, so head ban be squished to fit through birth canal, and brain can expand

Mesenchyme

embryonic connective tissue

mesenchymal cells

multipotent cells originating from mesenchyme (their progeny can become many things

bone remodeling

happens continually, osteogenesis and angiogenesis are coupled; for normal bone health, proper mineralization- need appropriate balance of osteoblast and osteoclast activity

Bone Deposition (Mineralization)

Osteoid laid down by osteoblasts.

Proteins and enzymes that come from osteoblasts are needed for mineralization

Bone resportion

Osteoclasts secrete enzymes & low pH solution (acid) to break apart matrix.

Osteoclasts transfer broken down material to blood.

When finished, they undergo apoptosis

Mechanical stress

necessary for normal bone development, determines where remodeling occurs, vigorous exercise can strengthen bone

Vitamin D

needed for small intestine to absorb calcium from diet,

sex hormones

affect bone

building blocks

certain physical and chemical signals for building bone, lack of = other signals for resorbing bone

calcium purpose

Besides being in the ECM of bone, calcium is a molecule that is essential for muscle contraction and for neuron-neuron communication (among other things)

calcium location

99% in bones

if calcium is low

negative feedback- parathyroid glands sense low level, PTH gets release, osteoclast activity increased to break down ECM to release calcium to blood, or increase calcium absorption at intestines to decrese loss in urine

Hormone PTH

PTH recruits and activates osteoclasts to promote matrix break-down

also promote bone formation - signilaing sytems are complex

blood vessels purpose in bone repair

newly sprouting blood vessels are necessary to bring in nutrients, oxygen and collagen-forming and osteogenic cells to the site of injury

bone formation and blood vessel formation

intricately linked with each other; The vascular system cells and skeletal system cells respond to some of the same molecular signals and also signal back and forth to each other (in a positive feedback loop)

cells involved in bone repair

Chondroblasts, chondrocytes, osteogenic cells, osteoblasts, and osteoclasts.

How is bone repair similar to bone growth and development?

Both involve bone formation by osteoblasts and bone remodeling by osteoclasts.

How is bone repair different from bone growth and development?

Repair replaces damaged bone; growth and development form and shape bones as the body develops

osteogeneis

The process of forming new bone tissue

what is osteogenesis coupled with

Angiogenesis (formation of new blood vessels), which supplies developing bone with oxygen and nutrients.