Dense regular connective tissue is represented in the skeletal system by ________, band-like structures that strap one _____ to _____.
ligaments, bone, another
Ligaments
Ligaments join bones together (Tendons join muscles to bone)
the strong parallel orientation fo collagen fibers at the microscopic level gives ligaments a striated appearance
Periosteum
a very important dense irregular tissue in the skelatal system
a thin membrane that surrounds all bones.
paperl-like membrane theat you encounter on the suface of ribs at a barbecue
it has a rich blood supplay
has plenty of nerve endings, so its the source of both blood (swelling) and pain when you break a bone
it connects tendons and ligaments to bones
its also important in bone repair and remodeling.
What are the freatures of a long bone?
they are longer than they are wide
cylindrical bones like the femur, tibia and fibula of the lowere extremity, and the phalanges(finger and toe bones of the upper and lower extremities)
Three natural parts ( or regions) of long bones
1. epiphysis (nearest articular surfaces)
-proximal epiphysis
- distal epiphysis
- these are where new bone develope in children
- in adults epiphyseal line is a rmnant of this location
2. metahpysis
3diaphysis ("shaft" of bone)
epiphysis
Located on either end of a long bone
these are the knoby ends of bone and form joint surfaces
diaphyisis
The shaft of a long bone
Mataphysis
the transistion between the epiphysis and the diaphysis
epiphyseal plate
the site if bone growth in an immature skeleton
this increases the length of long bones until the pituitary stops providing human growth hormone( hGH)
when epiphyseal plate continues growth -the plates are "open"
when hGH levels drop- the plates "close" or become mineralized.
The growth of lang bones at the epiphyseal plate, and the growth of bones in many other places, occurs through ________ ____ ________.
endochondral bone formation
Endochondral bone formation
bone formation using a cartilage "model" to shape the bone
cartilage is evetually replaced with compact or spongy bone
In fetuses and young children, many of the future bones are conpletely cartiliginous.
Primary Ossification center appears in the center of a forming bone where the diaphysis will be
Later secondary ossification center will develope near the joint surface.
Both of these will expand, the leftover region of cartilage between these is where the epiphyseal plate lies
epiphyseal line
the remnant of the epiphyseal plate, found in adults, who are done growing in height (this is seen as a landmark in x-rays of bone).
Intramembranous bone formation
again the future bone begins as a cartilage model
they are multiple ossification centers that start as islands and then spreat outward. As these spread, they form spongy bone.
Along the out side of the bone, spongy bone eveentually remodels to a thin shell of compact bone with the spongy bone remaining in the center
Occurs in bones of he skull and other flat bones
Osteoblasts
they make bone
they lay down the organic and inorganic extyracellular matrix of bone
they follow behaind osteoclasts rebuilding bone
in this way bone is constanly remodeled
If osteoblastic activity > osteoclastic activity
-calcium is deposited into inoganic matrix
-bone becomes thicker and stronger
Osteoclasts
brake bone into pieces
they constantly travel throu bone, using acid to dissolve mineralized matix and enzymes to dissolve organic matrix
If osteoclasts activity > osteoblasts activity
-calcium is released from inorganic matrix into bloodstreem
-bone becomes thinner and weaker
If blood _________ is low, the body breaks down ________ _______ to release calcium into the bloodstream. If blood calcium is high, the body stores ______ in ______for future needs.
calcium, mineralized bone, calcium, bone
True or False: A balance between osteoblasts and osteoclasts is critical, and is under hormonal control.
True.
If you have low blood calcium...
the body withraws calcium from its calcium "bank": bone tissue
Parathyroid hormone is released from a set of small pea-shaped glands next to the thyroid
this increased osteoclasts activity
Osteoclasts break down the mineral portion of bone and calcium is released into the bloodstream.
If blood calcium is too high...
Calcitonin is made by parafolicular cells (C cells) in the thyroid gland
-it is released when calcium is high and stimulates osteoblasts
Theses absorb calcium form the bloodstream and dposit it as hydroxyapatite in bone.
What are the three hormones involved in hormonal control of the blood?
1. Calcitonin
2. Parathytroif hormone (PTH)
3. Calcitriol
Calcitonin
inhibirs osteoclasts
stimulates osteoblasts
decreases blood calcium
increases bone formation
Parathyroid hormone (PTH)
stimulates osteoclasts
inhibits osteoblasts
increase blood calcium
decrease bone formation
Calcitriol
not directly invoved with bone
however, PTH stimulates kidneys to release calcitriol, which increases absorption of calciumfrom food
There are two D vitamins. Vitamin D2 (___________) and vitamin D3 (___________) are made in the skin with the help of UV-B light (i.e. ______ _______).
ergocalciferol, cholecalciferol, natural sunlight
True or false: Vitamin D is importand in the intestinal absoption of calcium.
true.
In the absences vitamin D...
blood calcium levels drop and bones become soft and flexible (bones are nostly colagen because mineral portion is lacking)
In children this results in rickets
Osteomalacia
In adults, inability to form mineralized bone
May result from metabolic disturbances, cancer, or cancer chemotherapy
Scan shows radioactiv 99Tc concentrating in areas that are making organic bone matrix but not the inorganic materialized porttionof bone.
