Anatomy and Physiology- Bone Tissue

osteology

the study of bone

skeletal system

bones, cartilage, and ligaments

loose

flexible

dense

tough

cartilage

-forerunner/precursor of most bones

-covers many joint surfaces of mature bone

ligaments

hold bones together at the joints

tendons

attach muscle to bone

functions of the skeleton

support, protection, movement, electrolyte balance, blood formation

electrolyte balance

calcium and phosphate ions

Bone (osseous tissue)

connective tissue with the matrix hardened by calcium phosphate and other minerals

mineralization

hardening process of bone

calcification

calcium deposits

what do individual bones consist of?

bone tissue, marrow, cartilage, adipose tissue, nervous tissue, fibrous connective tissue

do bones consist nerve and blood vessels?

yes

long bones

rigid levers acted upon by muscles

short bones

equal in length and width; glide across one another in multiple directions

flat bones

protect soft organs

irregular bones

elaborate shapes that dont fit into the other categories

compact (dense) bone

outer shell of long bone

What is another name for spongy bone?

Trabecular bone

Where is spongy bone found?

In the ends of long bones and the middle of nearly all others

What type of bone covers spongy bone?

Compact bone

diaphysis (shaft)

cylinder of compact bone

medullary cavity (marrow cavity)

space in the diaphysis that contains bone marrow

epiphyses

enlarged ends of a long bone
-enlarged to strengthen joint and attach ligaments and tends

articular cartilage

a layer of hyaline cartilage that covers the joint surface where one bone meets another
-allows joint to move more freely and relatively friction free

foramina

on the surface of bone tissue + holes in the bone surface that allows blood vessels to penetrate

Periosteum

external sheath that covers bone

Endosteum

thin layer of reticular connective tissue lining marrow cavity
-has cells that dissolve osseous tissue and others that deposit it

epiphyseal plate (growth plate)

area of hyaline cartilage that separates the marrow spaces of the epiphysis and diaphysis
-enables growth in length

epiphyseal line

in adults, a bony scar that marks where growth plate used to be

structure of flat bone

sandwich-like construction
-two layers of compact bone enclosing a middle layer of spongy bone

diploe

spongy layer in the cranium; absorbs shock

histology of osseous tissue

bone is connective tissue that consists of cells, fibers, and ground substance

four principle types of bone cells

osteogenic cells (osteoprogenitor) cells; osteoblasts, osteocytes, osteoclasts

osteogenic (osteoprogenitor) cells

stem cells found in endosteum, periosteum, and in central canals
-multiple continuously to produce new osteoblast

osteoblasts

bone forming cells
-line up as single layer of cells under endosteum and periosteum
-synthesize soft organic matter of matrix which then hardens by mineral deposition

stress and fractures

stimulate osteogenic cells to multiple more rapidly and increase number of osteocytes to reinforce or rebuild bone

secrete osteocalcin

thought to be the structural protein of bone

osteocytes

former osteoblasts that have become trapped in the matrix they have deposited

lacunae

tiny cavities where osteocytes reside

What are canaliculi?

Little channels that connect lacunae.

What do cytoplasmic processes do in relation to canaliculi?

They reach into canaliculi.

What homeostatic mechanisms do canaliculi contribute to?

Bone density and calcium and phosphate ions.

What happens to canaliculi when stressed?

They produce biochemical signals that regulate bone remodeling.

What are osteoclasts?

Bone dissolving cells found on the bone surface.

What is the origin of osteoclasts compared to other bone cells?

Osteoclasts have a different origin from the rest of bone cells.

How are osteoclasts formed?

Osteoclasts are unusually large cells formed from the fusion of several stem cells.

How many nuclei do osteoclasts typically have?

Osteoclasts typically have 3-4 nuclei, but may have up to 50.

remodeling

results from combined action of bone-dissolving osteoclasts and the bone-depositing osteoblasts

matrix of osseous tissue

1/3 organic, 2/3 inorganic matter

organic matter

synthesized by osteoblasts
-collagen, carbohydrate-protein complexes, such as glycosaminoglycans, proteoglycans, and glycoproteins

inorganic matter

85% hydroxyapatite (crystallized calcium phosphate salt)
10% calcium carbonate
Other minerals (fluoride, sodium, potassium, magnesium)

bone is a…

composite

inorganic portion

allows the bone to support the body weight, and protein portion gives bone some degree of flexibility

compact bone

the hard, dense outer layer of bone tissue that provides structural support, protection, and rigidity to the skeletal system

osteon (haversian system)

basic structural unit of compact bone

what is compact bone formed by?

a central canal and its concentric lamella connected to each other by canalaculi (compact bone)

perforating (Volkman) canals are…

transverse or diagonal passages along the length of the osteon

lamellae

parallel layers of bone with osteocytes; central canals- vertical canals

spongy bone consists of..

-slivers of bone called spicules, thin plates of bone called trabeculae, spaces filled with red bone marrow, provides strength with minimal weight

spicules

tiny, needle-like structures, typically made of silica or calcium carbonate, that form the skeletons of sponges and can also serve as a defense mechanism

trabeculae

regions of mesenchyme become a network of soft sheets

bone marrow

soft tissue that occupies that marrow cavity of a long bone and spongy bone

red marrow

in nearly every bone in a child, produces blood cells

where is red marrow found in adults?

skull, vertebrae, ribs, sternum, part of pelvic girdle, and proximal heads of humerus and femur

yellow marrow

found in adults, most red marrow turns into fatty yellow marrow, no longer producing blood

ossification or osteogenesis

the formation of bone

two methods of bone development

intramembranous ossification and endochondral ossification

intramembranous ossification

Produces flat bones of skull and clavicle

skull and clavicle

these bones develop within a fibrous sheet similar to epidermis of the skin (dermal bones)

mesenchyme

embryonic connective tissue condenses into a layer of soft tissue with dense supply of blood capillaries

mesenchymal cells differentiate into..

osteogenic (stem) cells

osteogenic cells differentiate into…

osteoblasts
-deposits organic matrix (osteoid tissue)
  +cells deposit organic matrix

as trabeculae grows thicker, what is deposited into the matrix?

calcium phosphate

converting spongy bone to compact bone

trabeculae at the surface continue to calcify until the spaces between them are filled in

What is endochondral ossification?

It is the process in which bone develops from a pre-existing cartilage model.

What does mesenchyme develop into during endochondral ossification?

Mesenchyme develops into a body of hyaline cartilage in the location of future bone.

What covers the cartilage model in endochondral ossification?

The cartilage model is covered with fibrous perichondrium, which becomes the periosteum.

perichondrium

produces chondrocytes (cartilage cells) initially, and later produces osteoblasts

What happens to chondrocytes in the secondary ossification center?

Chondrocytes in the middle of the model enlarge.

What occurs to the matrix between lacunae in the secondary ossification center?

The matrix between lacunae is reduced to thin walls.

What happens to the thin matrix walls in the secondary ossification center?

The walls of this thin matrix ossify and block nutrients from reaching chondrocytes.

comminuted fracture

bones shattered in pieces

simple fractures

no break in skin

compound fractures

bones sticking out

spiral fractures

bones broken due to twisting force

greenstick

incomplete break; broken on one side, bent on the side; seen in young children

stress/hairline fracture

small crack

intramembranous ossification

Intramembranous ossification

Produces flat bones as in the bones of the roof of the skull.

When the epiphyseal plate is replaced by bone

Long bones have reached their adult length.

In normal adult bones

A portion of the protein and mineral content is replaced each year.

All of the following are functions of bone EXCEPT which one?

Serving as an endocrine organ.

account(s) for almost two-thirds of the weight of bone.

Calcium phosphate.

Cells that secrete the organic components of the bone matrix are called

Osteoblasts.

A lack of exercise could

Result in porous and weak bones.

Which of these terms best describes a small hole going through a bone?

Foramen.

The lining of the medullary cavity is called the

Endosteum.