Tissue and bone growth, calcium balance Flashcards
Functions of bones
Storage
hematopoiesis
protection
movement
types of bones
Long bones
short bones
flat bones
irregular bones
What two structures make up bones
Cancellous( spongy) and compact bones
Describe compact bone
dense and solid
describe cancellous bones
open spaces
filled with needle-like structures
parts of long bones
Diaphysis Epiphyses Articular cartilage Periosteum medullary ( bone marrow) cavity
Diaphysis
main shaft of long bones
hollow cylindrical shape and thick compact bone
they provide strength minus the weight.
Epiphysis
bulbous
made of spongy bone
found on both ends of longs bones.
Provide attachment for muscles and joints
articular cartilge
layer of hyaline cartilage found on epiphyses to cushion jots and blows.
periosteum
- dense white fibrous membrane that covers the bone.
- attaches tendons firmly to bones
- contains blood vessels important for growth and repair
- essential bone for survival and bone fomation
Medullary cavity
tubelike hollow filled with marrow
Lined by endosteum:
Endosteum
a thing epithelial layer that lines the medullary cavity
characteristics of short flat and irregular bones
The inside is cancellous bone and outside is compact bones
Spaces inside the cancellous bone of irregular bones are filled with red marrow
- Large amounts of red bone marrow are found in flat bones of ribs, pelvis and skull
What makes up the bones matrix
inorganic salts
organic matrix
what inorganic salts are found in the bones matrix
- Hydroxyapatite crystals made of phosphate and calcium
characteristics of inorganic salts in the bone matrix
- it is found in collagen fibres
- it is about 10% calcium carbonate
- they are slender needle like crystals
- magnesium and sodium are also found in it.
What role do inrganic salts play in the bone matrix
meant to effectively resist stress and mechanical deformations
what makes the organic matrix
It is secreted by the bone cells called osteoblasts which then become imprisoned in the matrix
what is ground substance made of
collagenous fibes and mixtures of proteins and polysaccharides which form the gelatanous substance
What is the importance of ground substance
- Imprisoning organic matrix substances
- important in the healing and restoring as it acts as a medium for diffusion of nutrients, oxygen and metabolic waste
- Gives bone its rigidity by combining with calcium
structure of compact bones
4 layers
- lamella
- Lacunae
- canaliculi
- Haversian canal
describe the 4 layers of the compact bone
lamella - concentric rings that are islands of calcified matrix. They change with growth like tree rings.
lacunae- small spaces that contain tissue fluid in which bone cells are located between hard layers of lamella
canaliculi- small canals that radiate and connect osteocytes and to the haversian canal
Harvesian canal- extends lengthwise through the center if each osteon and contains blood vessels and lymphatic vessels.
Do cancellous bones have osteons
no they do not
what do cancellous bones have instead of osteons
tribeculae- needle
how are nutrients delivered and waste removed from compact bone
diffusion through tiny canaliculi
how do bony spicules enhance the bones strength
they are arranged along a line of stress
Explain how the bone help in storage
The bone serves as a depot for stored calcium. Osteoblast deposit calcium as they create new bone matrix
what do osteoclasts do
they break down matrix during bone resorption,
types of bone cells
Osteoblast
osteoclast
characteristics of osteoclasts
giant multinucleated cells responsible for the erosion of bone mineral
t
how are osteoclasts formed
by the fusion of several precursor cells this is why they are multinucleated
how are osteoclsts formed
from stems cells in the bone marrow that attach to bone surface by integrins
what do osteoblasts do?
- they bring about the formation of new bone
- facilitate the deposition and exchange of calcium
- determine the osteoclast formation through the RANKL receptor ligand system.
what are Osteoclasts
Giant multinucleated cells
what do osteoclasts do?
they are responsible for the erosion of bone minerals
How are osteoclasts formed
by the fusion of different precursor cells and this is why they are multiuclaeated
These cells are stems cells of the bone marrow that attach to the surface of integrins
what are osteocytes
these are trapped osteoblasts that are trapped int he surrounding bone matrix
why is long bone hollow
to provide for a less cumbersome weight
does the epiphyses have marrow or not?
yes it does
what is one function of the periosteum in terms of tendones
it attaches tendons firmly to the bone
what part of the bone is filled with yellow marrow in adults
medullary cavity
what is the medullary cavity lined by
endosteum
do all irregular and flat bones have red marrow in them
no, just a few of them do and it is mostly in flat bones like ribs, pelvis and skull
what bone cells excrete the organic matrix
osteoblasts, they become imprisoned in the matrix
what is ground substance
a part of the organic matrix that is a gelatanous material formed from collagenous fibres and a mixture of proteins and polysaccharides
what are some functions of organic matrix
it is important in bone growth and maintance as it acts as a medium for the diffusion of nutrients, oxygen and metabolic wastes.
- It combines with calcium to give bone its rigidity
Where in compact bone are bone cells located
In the tissue fluid in lacunae between layers of lamella
what connects osteocytes together and to the haversian canal
Canaliculi. This connection to the haversian canal allows for the excretion and absorption of nutrients
how are nutrients and wastes delivered and taken away from cancellous bone
through canaliculi radiating from bone cells
How do osteoclasts break down bone
they secrete acid and enzymes that dissolve the bone
what are the activators for the PANKL differentiation process
- Parathyroid hormone from the thyroid glands
what is an inhibiter for the RANKL differentiation system
Estrogen acting via osteoprotegrin
Calcitonin
what cells and processes control the amount of calcium in the blood
esteoblast leads to decrease in calcium levels in blood by reabsorbing it into the bone.
Esteoclasts leads to the increase in calcium levels in the bloods by releasing it during bone breakdown
Factors that affect bone balance
age
disease
diet
medications
How does PTH help with the up regulation of calcium levels in the blood in response to low Ca+ in the plasma
1- encourages reabsorption of Ca+ in the kidney
2- Encourages bone break down/erosion which results in the release of Ca+ into the blood
3- it stimulates the release of calcitrol which encourages the absorption of calcium in the intestines
describe the action of calcitonin
It is released by the thyroid hormone and it encourages loss of Ca+ in the urine and the action of osteoblasts
how does vitamin D work to put Ca+ in the bones
It encourages the reabsoption on Ca in the Kidney
It stimulates Osteoblast activity
In the intestines it increases the synthesis of of calcium binding proteins on intestinal cells
A vitamin D difficiency may result in…
Rickets in children
Osteomalacia in adults
what is a fetus’s skeleton made of
cartilage which is later replaced with a calcified bone matrix
Osteogenesis in children and adults
in children there is high activity of osteoclasts and osteoblasts and calcification which is the laying down of calcium salts.
how does exercise help people have stronger bones
It stimulates Osteoblasts to produce more collagen and this makes for stronger bones
mention the twi 2 mechanisms for for bone formation
intramembranous- some flat bones, no cartilage
Endochondrial- Cartilage, vascular, long and flat bones
Intramembranous bone formation
it is less common and does not start with cartilage. Some flat bones like the skull and jaw line form this way.
They lay mesechymal cells which differentiate and start to lay bone around them
It begins in connective membrane, mesechymal cells migrate to site of formation and differentiate into osteoblasts these cluster together in ossification sites and release matrix materuak abd collagenous fibrils.
mineralization then occurs and when the organic strands when mineralised are called trabecula
Endochondral bone development
Mesechymal cells migrate to region of bone formation and differentiate to chondrocytes which then differentiate into a hard avascular mass in the shape of the bone that is to be formed
periosteum covers the cartilage and its inner surface differentiates into osteoblasts which make acollar around the cartilage
Primary ossification centers form and blood vessels enter the cartilage through the center of the diaphysis and the bone grows as ossification occurs in the diaphysis outward
As endochondral bone formation is occuring what happens to the epiphyseal plate
It stays between the diaphysis and the epiphysis and bone has grown to its full length
what five layers makeup the epiohyseal plate
zone of resting cartilage Proliferation hypertrophy calcification diaphysis
mechanism of estrogen on bones
estrogen causes osteoblasts to produce TGF-beta which then causes them to produce osteoprotegrin which bines to RANKL and this prevents preosteoclasts from binding to RANK and forming osteocytes. This stops resoption.
what happens when there is less estrogen in the body
Bone resorption increases
Osteoporosis symptomes
vertabrae, wrist and hip fructures
Lower back pain, neck pain and tenderness
Stooping over
Osteoporosis drugs
uscalcitonine of drugs like
Raloxifene and calcitriol
or estrogen therapy and EXERCISE
