chapter 6: skeletal system

joints

allow movement between bones

flat bones

contain spongy bone sandwhiched between 2 layes or compact bone.

surface of trabeculae

covered with single layer of cells consisting mostly of osteoblasts with few osteoclasts

undifferentiated cell grows and develops into final form is named with the suffix

cyte

bone is added to

diaphysis

short and irregular bones do not have what?

diaphysis

what is the center portion of the bone

diaphysis

concentration of Ca2+ and PO4 form what

hydroxyapatite crystals that mineralize matrix

osteoblasts remove ca2+ from blood to make bone

if blood ca2+ is high

osteoclasts release ca2+ to blood

if blood ca2+ is low

what will show in a young bone

presences of epiphyseal plates

osteoprotegerin (OPG)

prevents osteoclast differentiation by preventing the binding

collagen

provides stregth and flexibily

exception where yellow marrow does not replace red marrow

proximal part of arm bones and thighbones. -also hip bone (illium) because its large bone

spongy bone and medullary cavity is filled with

red marrow and yellow marrow

insufficient vitamin d causes

rickets which is reduced mineralization of the bone matrix(growing)

surrounding the central canal is

rings of bone matric called concentric lamellae (4-20)

osteoclasts

secrete acid and protein-digesting enzymes that are bone-destroying cells

chondroblasts

secrete matrix, surrounds the chondroblasts. and becomes chondrocyte

-blast term meaning

seed or bud

how does PTH increase osteocyte formation

RANKL binds to receptor rank and activates osteoclast precursor cells

what is stored within bone in the body

ca2+

osteocytes are in contact with each other through

canaliculi

osteocytes get nutrients by

canaliculi

osteocyte cell extensions termed as

canaliculi that contact other cells and lets nutrients pass through

callus ossification steps

cartilage and callus are replaced by woven spongy bone

chondrocytes

cells occupy a space called lacuna within matrix

center of osteon

central canal

appositional cartilage growth

chondroblasts in the perichondrium add new cartilage to outside edge of existing cartilage

interstitial growth

chondrocytes in the center of the tissue divide and add more matrix in between existing cells.

osteoblasts produce what

collagen and proteoglycans packaged by Golgi and excreted by exocytosis

perforating fibers

collagen fibers of the tendons or ligaments penetrate the periosteum in the outer part of the bone.

if mineral in long bone is reduced then?

collagen is the primary constituent and bone is overly flexible

matrix has what that provides what

collagen- strength proteoglycans-makes cartilage resilient by trapping water

outer layer of bone:

compact bone

bone is what tissue

connective tissue

red marrow

connective tissue in the spaces of spongy bone or in medullary cavity. site of blood cell production

long bone of hand and foot have how many epiphysis

one

1st step of bone growth

osteoblasts beneath periosteum lay bone down to form ridges separated by grooves where blood vessels are

3rd step of bone growth

osteoblasts from endosteum lay down concentric lamella

periosteum and endosteum consists of what cells

osteoblasts, osteoclasts, and osteochondral progenitor cells.

osteoblasts derived from

osteochondral progenitor cells

what breaks down woven bone to build stronger permanent lamellar bone

osteoclasts

functional unit of long bone is?

osteon or haversian system

osteoblasts add bone from?

outside

Growth Hormone (GH) function

overall bone growth (height), interstitial cartilage growth and appositional bone growth

low blood calcium levels stimulus and response

parathyroid cells detect low ca2+ and secrete PTH -PTH activates calcitriol in kidney response: PTH and calcitriol stimulate osteoclast formation -PTH stimulate Ca2+ reabsorption in kidneys tubules -calcitriol stimulate ca2+ uptake in small intestine.

calcium homeostasis is regulated by 3 hormones

parathyroid hormone (PTH), calcitriol (active form of vitamin D), and calcitonin

cartilage is covered by connective tissue sheath

perichondrium

where does perforating canals get their blood vessels

periosteum or medullary cavity.

mineral storage of what in bones

phosphorus and calcium

perforating fibers function

(sharpey fiber) they strengthen the attachment of the tendons or ligaments to the bone.

aging process

1st. spongy bone is lost and trabeculae is thin/weak 2. compact bone is loss under the endosteum

ossification occurs multiple times during lifetime like:

-as a fetus -anytime in life a fracture is repaired

osteoclasts derived from

-osteoblasts -stem cells in red bone marrow

organic material in bone

35% and is collagen and proteoglycans

endochondral ossification steps

1. cartilage model formation- osteochondral progenitor cells becomes chondroblasts 2. bone collar formation-compact bone and enlarged cartilage 3. 1st ossification center formation- osteoblasts produce spongy bone on calcified cartilage and medullary cavity 4. 2nd ossification center- at the epiphysis without medullary cavity 5. adult bone

intramembranous ossification steps

1. osteoblast formation 2. spongy bone formation 3. compact bone formation

bone resorption process detailed

1. osteoclasts enter the matrix 2. osteoclasts in contact with bone form attachment by integrins 3. podosomes develop and form sealed compartment under osteoclasts 4. membrane becomes highly folded ruffled border. 5. secretion of H is acidic for sealed compartment and causes decalcification. 6. breakdown of matrix and products 7. products secreted into extracellular space

Vitamin C deficiency causes (3)

1. scurvy, ulceration and hemorrhage because collagen synthesis is not occurring. 2. teeth can fall out because ligaments break down, 3. wounds can hinder healing

bone repair steps

1.hematoma 2. callus 3.callus ossification 4. bone remodeling

inorganic material

65% and is calcium phosphate, aka hydroxyapatite

high blood calcium levels stimulus and response

C cells in the thyroid gland detect high Ca2+ and secrete calcitonin response: calcitonin inhibits osteoclasts slowing bone reabsorption

bone resorption process

Ca2+ goes back into blood.

perforating canals

Volkmann canals which deliver blood to central canals of the osteons. -runs perpendicular to bone.

vitamin d is a nutrition factor important for

absorption of calcium from the intestines

spongy bone

appears porous and has less bone matrix and more space with rode of bone called trabeculae (no blood vessels) -found mostly in epiphysis

ossification occurs by what growth

appositional growth on bone or cartilage

bones increase in size only by

appositional growth unlike cartilage that can undergo interstitial growth.

within joints the ends of long bone is covered with hyaline cartilage called

articular cartilage

BMU- basic multicellular unit

assembly of osteoclasts and osteoblasts through/across bone

conversion of red marrow to yellow marrow begins when

before birth and continues until adulthood. it will replace all red marrow in long bones.

interstitial lamellae

between osteons and remnants of concentric or circumferential lamellae that were partially removed during bone remodeling.

epiphyseal plate located where

between the epiphysis and the diaphysis

central canal cells are

blood vessels, nerves, and loose connective tissue

skeletal system function

body support, organ protection, body movement, mineral storage, blood cell production

calcified cartilage is replaced by

bone

hormone calcitonin site and action

bone cells action: decrease ca2+

if blood Ca2+ levels are depleted what happens

bone is demineralized and weak

osteocytes are located within

bone matrix in spaces called lacunae

breakdown of bone called

bone reabsorption

osteoblasts

bone-building cells

external callus is known as

bone-cartilage collar

skeletal system has 4 components:

bones, cartilage, tendons, and ligaments

growth in long bones occur where

both ends of diaphysis

osteogenesis imperfecta OI

brittle bone disorder that can causes loose joints, brittle teeth, hearing loss and blue tint to eyes

calcitonin is secreted from

c cells in the thyroid gland when blood ca2+ is too high

perichondrium

double-layered outer layer of dense irregular connective tissue containing fibroblasts while inner layer has chondroblasts

central canals and internal surfaces are lined by

endosteum

what will show in an adult bone

epiphyseal line

growth in bone length occurs where

epiphyseal plate

cartilage forms on

epiphyseal side of plate

reproductive hormone in men and female

estrogen= girls testosterone=males

boy or girl stops growing earlier?

females (18)

woven bone

first bone that osteoblasts form during ossification. it is weak because collagen fibers are oriented in many directions

circumferential lamellae

form the outer surfaces of compact bone which are thin plates that extend around the bone.

ossification or osteogenesis

formation of new bone by osteoblasts

Growth Hormone (GH) from?

from: anterior pituitary gland

osteoblasts connecter to extensions of other osteoblasts by

gap junctions

precursor to healed tissue

granulation tissue

2nd step of bone growth

groove is transformed into tunnel because ridges extends and what was the periosteum is now the endosteum

hormones affecting bone growth

growth hormone (GH), Thyroid hormone, reproductive hormone

most bones start out as?

hyaline cartilage

articular cartialge

hyaline cartilage that covers the ends of bones and come together to form joints. -no perichondrium, blood vessels, or nerves

3 types of cartilage

hyaline, fibrocartilage, elastic cartilage.

increase mechanical stress and physical pressure does what

increase osteoblast activity

Increased PTH promotes activation of calcitriol in kidneys which?

increases absorption of ca2+ in small intestine

osteoclasts remove bone from?

inside

periosteum

is outer bone and contains blood vessels and nerves and inner is osteoblasts, osteoclasts and osteochondral progenitor cells

hormone PTH site and action

kidney tubules, bone cells action: activate calcitriol and increase Ca2+

hormone calcitriol site and action

kidney tubules, small intestines and bone cells action: increase Ca2+

trabeculae are oriented along where?

lines of mechanical stress within a bone

hematoma (bone repair)

localized mass of blood released from blood vessels but confined with a space/orgnan. -clots

osteocytes form when

once osteoblasts create sufficient bone matrix

osteporosis

loss of bone matrix and makes bones porous and weak

proteoglycans

make cartilage resilient by trapping water

external callus

mass of bone tissue forming at the break of fracture and connects the broken ends of the bone

internal callus

mass of bone tissue that forms between ends of broken bones and marrow cavity if in diaphysis.

lamellar bone

mature bone. thin layers= 3-7 micrometers called lamella. -collagen fibers of lamella are parallel to one another -osteocytes are arranged in layers sandwiched between lamellae.

what is the hollow center of a bone within the diaphysis

medullary cavity

if collagen is reduced in the bone then?

mineral component is the primary constituent and the bone is brittle

compact bone

more bone matrix and less space than spongy bone

yellow marrow

mostly adipose tissue. fat stored within the medullary cavity or in spaces of spongy bone

sinuses are lined by what

mucous membranes and are air-filled spaces

tendons

muscles attach to bones

vitaman c is nutrition factor important for

necessary for osteoblasts to synthesize collagen

Thyroid hormone function

normal growth of tissues and cartialge

tendons

skeletal muscles attach to bones

fontanels

soft spots, that have not been ossified and between developing skull bones

osteomalacia

softening of bones due to calcium depletion

endochondral ossification

starts with a cartilage model

intramembranous ossification

starts within embryonic connective tissue membranes. -8th week-2 years -skull, mandible, clavicles

ligaments

strong bands of fibrous connective tissue, holding bones together.

4th step of bone growth

the lamellae fills the tunnel and forms the osteon

trabeculae

thin and consists of lamellae with osteocytes located in lacunae between lamellae. within spongy bone

2 bones formed during ossification

woven bone and lamellar bone

bone remodeling is finished when

woven bone is replaced by compact bone