Skeletal System

the \_____ provides structure, support, rigidity, and protection to organs

skeletal system

the skeletal system serves as a reservoir of \_____ and \_____ substances

inorganic; organic

\_____ skeletons belong to organisms without bones, especially backbones

invertebrate

insects tend to have \_____, which are skeletons on the outside of the organism

exoskeletons

\_____ skeletons belong to organisms that have a backbone

vertebrate

vertebrates have \_____, which are skeletons on the inside of the organism

endoskeletons

what are the 2 parts of human endoskeletons?

axial; appendicular skeletons

what are the types of bones?

long; short; flat; sesamoid; irregular

long bones are \_____ than they are \_____

longer; wide

what are some examples of long bones?

femur; radius; ulna

what are some of the predominant structural features of long bones?

epiphyses; diaphysis; a medullary cavity; metaphyses; epiphyseal growth plates

(note growth plate \= epiphyseal line in this picture)

\_____ are the bumpy parts at the ends of long bones

epiphyses

\_____ covers epiphyseal compact bone in synovial joints

articular cartilage

articular cartilage covers epiphyseal compact bone in \_____ joints

synovial

what type of joint is formed between long bones?

synovial joints

at birth and early adolescence, all bone marrow is \_____ bone marrow, which gradually gets replaced with \_____ bone marrow at certain bone locations

red; yellow

(yellow bone marrow mainly replaces the red bone marrow in long bone medullary cavities)

\_____ bone marrow is located in spongy trabecular bone of adults

red

\_____ is the process where stem cells create new blood cells

hematopoiesis

(this picture shows red bone marrow in the medullary cavity, so the bone must belong to a young child)

hematopoiesis occurs in the \_____ bone marrow of \_____ bone

red; spongy trabecular

the \_____ of a long bone is the shaft between the ends

diaphysis

the \_____ is the "hollow" part of the diaphysis, which contains \_____ bone marrow in adulthood

medullary cavity; yellow

the \_____ bone marrow stores energy as fat

yellow

(hematopoiesis does not occur at yellow bone marrow)

\_____ are found between the medullary cavity and epiphyseal plates of a long bone

metaphyses

metaphyses have a similar structure to the \_____ of a long bone

epiphyses

(structure is spongy trabecular bone)

epiphyseal plates are \_____ cartilage during adolescence, and they \_____ to an epiphyseal line during puberty

hyaline; ossify

epiphyseal plates grow before ossification to promote \_____

bone lengthening

epiphyseal plates grow toward the \_____ to lengthen the \_____ of a long bone

metaphyses; diaphysis

epiphyseal lines are found between long bone \_____ and \_____ in adults

epiphyses; metaphyses

(same holds true for epiphyseal plates in adolescents)

cartilage is \_____, which makes it difficult to heal

avascular

breaking a bone at the epiphyseal plate can stunt growth because epiphyseal plates are made of \_____, which is avascular and difficult to heal

hyaline cartilage

\_____ bones are cuboidal and provide support with little movement

short

short bones are primarily \_____ bone covered by a thin layer of \_____ bone

cancellous (spongy trabecular); cortical (dense)

what are some examples of short bones?

carpals of the wrist or tarsals of the ankle

\_____ bones are thin, with outer layers of cortical bone surrounding spongy, cancellous interiors

flat

what are some examples of flat bones?

sternum and the bones forming the skull

sesamoid bones are found in \_____, and they act to increase muscle power - what is an example of a sesamoid bone?

tendons

irregular bones have \_____ layers surrounding \_____ interiors; however, their shapes do not fit any other bone class

dense, cortical; spongy, cancellous

what are some examples of irregular bones?

vertebrae; sacrum; pelvis

\_____ bone is the outer layer of bones

cortical

what allows bones to support weight?

cortical bone density

what are the microstructures in cortical bone?

osteons; Haversian canals; lamella; lacunae; canaliculi; Volkmann's canals

\_____ are the functional unit of cortical bone, and they appear as multi-layer cylinders

osteons

what direction do osteons travel within cortical bone?

parallel to the bone's long axis

the layers that make-up an osteon are called \_____

lamellae

\_____ contain cortical bone and collagen fibers

lamellae

\_____ are the central canals of an osteon

Haversian canals

Haversian canals contain blood vessels to supply nutrients to the \_____ of an osteon

osteocytes

(Haversian canals connect to osteocytes through canaliculi)

\_____ are small spaces between lamellae that house osteocytes

lacunae

canaliculi connect \_____ and \_____ of a single osteon

lacunae (housing osteocytes); Haversian canals

\_____ canals connect adjacent osteons, and they also connect peripheral osteons to the periosteum

Volkmann's

\_____ bone is soft and flexible, and it is made of \_____ that soak up bone marrow like a sponge

cancellous; trabeculae

(trabecular/cancellous bone \= spongy bone)

\_____ are precursors to osteoblasts

osteoprogenitors

osteoblasts contain \_____ nucleus

1

what is the main function of osteoblasts?

to build bone (secrete collagen + proteins that make osteoid)

\_____ are mature bone cells that develop from osteoblasts

osteocytes

how do osteoblasts become osteocytes?

osteoblasts get trapped in the osteoid they secrete

osteoclasts contain \_____ nuclei, and they are found in \_____

multiple; Howship's lacunae

what cell type gives rise to osteoclasts?

monocytes

what is the main function of osteoclasts?

to resorb ("chew") bone

Howship's lacunae

pits created by osteocytes

what is bone remodeling?

the back and forth between resorption (osteoclasts) and ossification (osteoblasts)

what are the primary factors that affect bone remodeling?

parathyroid hormone, vitamin D, calcitonin

parathyroid hormone (PTH) is secreted from the parathyroid gland, and it \_____ blood Ca2+

increases

PTH stimulates \_____ (bone cell) and depresses \_____ (bone cell)

osteoclasts; osteoblasts

vitamin D is activated by \_____ to \_____ blood Ca2+

PTH; increase

activated vitamin D provides \_____ to PTH

negative feedback

vitamin D stimulates Ca2+ \_____ in the intestines, and increases the \# of \_____ for resorption

absorption; osteoclasts

calcitonin is secreted by the \_____ gland, and it opposes PTH to \_____ blood Ca2+

thyroid; lower

calcitonin decreases the activity of \_____, so \_____ have less competition

osteoclasts; osteoblasts

\_____ is made of proteins and type 1 collagen fibers, to provide bones with tensile strength

osteoid

\_____ provides bone density, and it is made of inorganic crystals of Ca2+, phosphate, & H2O

hydroxyapatite

what are the 2 types of embryonic ossification?

intramembranous and endochondral

what is the most common type of embryonic ossification?

endochondral ossification

\_____ ossification occurs when bone is created directly within a fibrous membrane

intramembranous

what types of bones are usually made by intramembranous ossification?

flat bones

\_____ ossification occurs when bones are created indirectly, from a cartilage model

endochondral

what bones are made through endochondral ossification?

long bones

what are the 3 main types of connective tissue?

fibrous; cartilage; joints

fibrous connective tissue includes what 3 things?

tendons; ligaments; periosteum/endosteum

\_____ connect bones to muscle

tendons

\_____ connect bones to other bones

ligaments

the \_____ is a protective fibrous membrane that covers cortical bone

periosteum

what are the 2 sublayers of the periosteum?

outer fibrous layer; inner/cambium layer

(cellular layer \= inner/cambium layer)

the outer fibrous layer of the periosteum is \_____

vascularized

the \_____ layer of the periosteum contains collagen and osteoprogenitor cells

inner/cambium

the \_____ is a single layer membrane between cortical and cancellous bone

endosteum

cartilage is \_____ and not \_____

avascular; innervated

how do cells living in cartilage get nutrition/immune support?

from the surrounding fluid

(cartilage does not contain blood vessels and it is not innervated)

cartilage building cells are called \_____

chondroblasts

(analogous to osteoblasts)