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Osseous Tissue & Bone Structure
Chapter 6
42
Anatomy
Undergraduate 2
10/17/2015

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Cards

Term
Five Primary Functions of the Skeletal System.
Definition

1. Support

2. Storage of minerals & Lipids

3. Blood Cell Production

4. Protection (skulls, ribs, pelvis)

5. Leverage (Change the mangitude & direction of forces generated by the skeletal muscle.)

Term
Six Categories of Bone with examples.
Definition

1. Long Bones: humerus, femur, fingers

2. Flat Bones: roof of skull, rubs, scapulae, sternum

3. Sutural Bones: Tiny bones between cranial bones

4. Irregular Bones: vertebrae, pelvis

5. Short Bones: Carpals, Tarsals

6. Sesmoid Bones: Patella

 

 

Term
If the activity of Osteoclasts exceeds the activty of osteoblasts in abone how will the mass of the bone be affected?
Definition
Because osteocalsts break down or demineralzie bone, the bone would have a reduced mineral content (Less Mass); as a result it would also be weaker.
Term
During the growth of a long bone, how is the epiphysis forced farther from the shaft?
Definition
Cartilage cells divide and multiply on the epiphyseal side making it thicker, at the same time old cartilage cells on the diaphyseal side are being replaced by bone.
Term
Osteocyte
Definition
  • Mature bone cells
  • Most abundant
  • Cannot divide
  • Occupies a lacunae
  • Linked by gap junctions

Functions:

  • Maintain the protein/mineral content of the surrounding matrix
  • When released from lacunae, osteocytes can change to osteoblasts to aid in repair of damaged bone.

 

Term
Osteoblast
Definition
  • Produce new bone matrix through osteogenesis (ossification)
  • Osteocytes develop from osteoblasts that have become completely surrounded by bone matrix
  • Osteoprogenitor (mesenchymal) cells
  • Divide to produce osteoblasts
  • Important in repair (e.g., fracture)

 

Term
Osteoclast
Definition
  • Remove and recycle bone matrix
  • Giant cells with 50+ nuclei
  • Produced from the same stem cells that produce monocytes and macrophages
  • Enzymes secreted by the osteoclasts dissolve matrix and release stored minerals – osteolysis (reabsorption)
  • Important in the regulation of calcium and phosphorus concentrations in body fluids
Term
Lamella
Definition

 

layers of bone nesting around the central canal

 

Term
Central Canal
Definition

(Haversian Canal) – contains blood vessels (i.e., capillaries and venules)

 

Term
Trabeculae
Definition

 

struts and plates formed by the matrix

 

Term
Calcification
Definition
Depositing of calcium salts, occurs during ossification. Can occur in the tissue
Term
Ossification
Definition

Process of the synthesis of bone from cartilage.

Intramembranous: transformation of mesenchyme to bone.

Endochondral: Gradual replacement of cartilage by bone during development.

Term
Periosteum
Definition
Connective tissue covering of the bones.
Term
Endosteum
Definition
incomplete connective tissue layer that lines the medullary cavity
Term
Compact (Dense) Bone
Definition
  • Sturdy protective area
  • Haversian system (osteon)
  • Osteocytes are arranged in concentric layers around a central canal
  • Central canal
  • Lamella
  • Thickest in areas of stress
  • Strength along the axis of alignment (i.e., straw)

 

Term
Spongy (cancellous) Bone
Definition

 

  • Lamella are not arranged in osteons
  • Trabeculae
  • No capillaries or venules
  • Nutrients reach the osteocytes by diffusion along canaliculi that open to the surface of trabeculae
  • Red bone marrow found between the trabeculae
  • Located where bones are not heavily stressed or where stress is from many directions
  • Lighter than compact bone
  • Yellow bone marrow - contains adipose tissue for energy reserve
  • Red bone marrow – blood cell formation

 

Term
Endochondral Ossification Part 1
Definition
  • Chondrocytes near the center increase in size
  • The lacunae expand
  • The matrix is reduced to thin struts that begin to calcify
  • The enlarged chondrocytes surrounded by calcified tissue start to die

 

Term
Endochondral Ossification Part 2
Definition
  • Blood vessels grow into the perichondrium surrounding the shaft of the cartilage
  • The cells of the inner layer differentiate into osteoblasts
  • The new osteoblasts begin to produce a thin layer of bone around the shaft of cartilage

 

Term
Endochondral Ossification Part 3
Definition
  • The blood supply to the periosteum increases
  •   Capillaries and fibrocytes migrate into the heart of the cartilage
  •   Fibrocytes differentiate into osteoblasts that replace remaining cartilage with bone
  •   Primary ossification center because bone development begins at this site
  • Bone development spreads toward both ends of the cartilaginous model
  • The diameter of the diaphysis is small and filled with spongy bone with no medullary cavity present

 

Term

Endochondral Ossification Part 4

 

Definition
  • The bone enlarges
  • Osteoclasts appear and begin to erode the trabeculae in the center of the diaphysis, creating a medullary cavity

 

Term
Endochondral Ossification Part 6
Definition
  • The epiphysis become filled with spongy bone
  • A thin cap of the original cartilage model remains in the joint cavity as articular cartilage; prevents bone-on-bone at joint
  • At the metaphysis, a narrow cartilaginous region called the epiphyseal cartilage separates the epiphysis from the diaphysis

 

Term
In endochondral ossification, what is the original source of osteoblast?
Definition
The cells of the inner layer of periosteum differentiate into osteoblasts. They then differentiate into osteocytes.
Term
How could X-rays of the femur determine if a person has reached full height?
Definition

Long bones have epiphyseal cartilage, a plate of cartilage that seperates the epiphyses from the diaphysis as long as the long bone is growing in length. An x-ray could tell if the epiphyseal cartilage is present. If it is not, they are at full height.

Term
Compare and contrast endochondral and appositional bone development.
Definition

Appositional: Increase thickness and is responsible for remodling of all the long bones

Endochondral: Turns cartilage into bone, most growth is lengthwise.

Term
Steps of Intramembraneous ossification (1)
Definition
  • Mesenchymal cells cluster together and secrete organic compounds of the matrix
  • The resulting osteoid becomes mineralized through crystallization of calcium salts
  • As calcification occurs, mesenchymal cells differentiate into osteoblasts
  • The developing bone grows outward from the ossification center (i.e., location where ossification begins) in spicules
  • Mesenchymal cell divisions continue to produce additional osteoblasts

 

Term

 

Steps in Intramembraneous Ossification (2)

 

Definition
  • Blood vessels begin to grow in the area
  • As spicules meet and fuse, some of these blood vessels   
  • become trapped within the developing bone

 

Term
Steps in Intramembraneous Ossification (3)
Definition
  • Initially the bone consists of spongy bone only, but subsequent remodeling around trapped blood vessels can produce osteons typical of compact bone
  •  As growth slows, connective   tissue around bone forms   the periosteum

 

Term
Your patient is 13 yo and lives in an urban apartment.  He spends most of this time watching TV and eating "junk food".  One afternoon, he falls on the playground and breaks his leg.  Although he appears to be healthy, his leg take longer to heal than expected.  What might be the cause of the longer healing time?
Definition

His poor diet consisting of little nutrients and vitamins would result in a slower healing process. His inactivity may also contribute to a slower reate. (bones may be thin/brittle)

Term

Compare and contrast the functions/actions of calcitonin and parathyroid hormone.

 

Definition

Calcitonin: Homeostatic control of calcium (thyroid)

Parathyroid: homeostatic control of phosphorus (parathyroid)

Term
Would you expect to see changes in blood levels of the hormone calcitonin and PTH as a result of Vitamin  D deficiency?  Explain.
Definition
Yes, Vitamin D is vital for normal calcium & phosphorus absorption from the intestines
Term
Which vitamins are essential for normal bone maintenance?  What role do these vitamins play?
Definition

Vitamin A: Stimulates osteoblasts

Vitamins K&B12: Required for sunthesis of proteins in bone

Vitamin D: Calcium and Phosphours levels.

Term
Which hormones are essential for normal bone development?  What role do these hormones play?
Definition

 

oGrowth Hormone

 

nProduced by the pituitary gland

 

nStimulates protein synthesis and cell growth throughout the body

 

oThyroxine

 

nProduced by the thyroid gland

 

nStimulates cell metabolism

 

nIncreases the rate of osteoblast activity

 

oCalcitonin and Parathyroid Hormones

 

nImportant in the homeostatic control of calcium and phosphorus

 

nExcreted by the thyroid and parathyroid glands

 

oEstrogens and Androgens

 

nStimulate osteoblasts to produce bone faster than the rate at which epiphyseal cartilage expands

 

nThe toes may complete ossification by age 11

 

nParts of the pelvis and wrist may continue to enlarge until 25 years of age

 

nEstrogens cause faster epiphyseal closure than androgens

 

oWomen are usually shorter than men

 

oGenetics also play a role in bone length

 

Term
How does exercise alter the structure of bone?
Definition

Heavily stressed bones become thicker and stronger

Term
What role do the bones, digestive tract, and kidneys play in maintaining calcium levels in the blood.
Definition

Bones: Store 99% of calcium in body

Digestive Tract: Absorb Calcium

The Kidneys: Excrete Calcium

Term
List reasons why osteopenia is most often seen in elderly patients.
Definition

Inadequate ossification. Gradually lose osteoblasts activity with age.

Term
Steps involved in healing a bone fracture (1)
Definition

 

nFracture hematoma

 

oCloses off injured vessels

 

oLeaves a fibrous meshwork in the damaged area

 

oLoss of circulation kills osteocytes

 

Term
Steps involved in healing a bone fracture (2)
Definition
  • External callus forms
  • Enlarged collar of cartilage and bone, encircles the bone at the level of fracture
  • The cells of the intact endosteum and periosteum undergo rapid cell division to replace missing cells in the fractured area
  • Internal callus forms
  • Organizes within the medullary cavity and between the broken ends of the shaft
  • Callus cells differentiate into chondrocytes that produce a layer of hyaline cartilage that stabilizes the bone

 

Term
steps involved in healing a bone fracture (3)
Definition

nOsteoblasts replace the cartilage of the callus

nStruts of spongy bone unite the broken ends

nInternal and external callus form an extensive and continuous brace at the fracture site

nCast can be removed

 

Term
Dwarfism
Definition

nPituitary failure leading to inadequate production of growth hormone and resulting in reduced epiphyseal cartilage activity

nThe result is abnormally short bones

nBecoming increasingly rare in US

oSynthetic growth hormone supplementation

 

Term
Gigantism
Definition

 

nOverproduction of growth hormone before puberty

 

Term
Acromegaly
Definition

 

nOverproduction of growth hormone after puberty

 

nSkeleton doesn’t grow longer; instead thicker bones especially face, hands, and jaw

 

Term
Marfan's Syndrome
Definition

 

nVery tall stature with long, slender limbs

 

nExcessive cartilage formation at the epiphyseal plates

 

nThe underlying genetic mutation affects structural connective tissue throughout the body, but most significantly affects the cardiovascular system

 

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