Chapter 6 Questions
what type of tissue makes up the epiphyseal plate?
composed of hyaline cartilage that does not ossify during endochondral ossification.
Walk through the basic steps of fracture repair
1) A hematoma fills the gap between the bone fragments. 2) Fibroblasts and chondroblasts infiltrate the hematoma, and a soft callus forms 3) Osteoclasts build a bone callus 4) The bone callus is remodeled and primary bone is replaced with secondary bone.
Explain why a person who is wheelchair-bound or bed-bound often has very low bone mass, especially in his or her legs.
An individual who is not bearing weight regularly is not placing an adequate load on his or her bones. This leads to insufficient stimulation of bone deposition, and so bone resorption predominates. This leads to progressive loss of bone mass.
The disease osteogenesis imperfecta is characterized by defective collagen in the organic matrix of bone. Predict the effects of such a disease
Bones affected by osteogenesis imperfecta are extremely brittle, as they lack the collagen fibers to give them tensile strength. This makes them much more likely to fracture when subjected to even normal physical forces
Lacunae
Cavities that house osteocytes
Where are compact bone and spongey bone located and what are their functions?
Compact bone: Walls of all bones, Osteons and central canal. provides protection, support, and movement Spongey bone: Epiphasis of long bone between walls of sort, irregular, flat, and sesamoid bones. Trabeculae, soak in red bone marrow. blood cell production
What would probably happen to bone with more osteoclast than osteoblast activity?
Excess osteoclast activity would mean that more ECM would be broken down than built, which would lead to progressive weakening of the bone.
Compare and contrast the locations and functions Osteoblast, Osteocytes, and Osteoclasts.
Osteoblast: -located on the surface of existing bone matrix, formation of bone. Osteocytes: -inside spaces called lacunae and canaliculi, strengthen your bones through bony remodeling Osteoclasts: -in pits in the bone surface which are called resorption bays, break down old bone cells to make way for osteoblasts to stimulate new bone growth.
Walk through the basic steps of Intramembranous ossification
1) Osteoblasts develop in the primary ossification center from mesenchymal cells. 2) Osteoblasts secrete organic matrix, which calcifies, and trapped osteoblasts become osteocytes. 3) Osteoblasts lay down trabeculae of early spongy bone, and some of the surrounding mesenchyme differentiates into the periosteum 4) Osteoblasts in the periosteum lay down early compact bone
Predict the effect that a parathyroid hormone-secreting tumor would have on bone tissue. What would happen to the concentration of calcium ions in the blood with such a condition?
A tumor that secretes parathyroid hormone would trigger excessive osteoclast activity, and the resulting breakdown of bone would lead to more frequent bone fractures. In addition, it would cause the concentration of calcium ions in the blood to be much higher than normal because the normal negative feedback loop would be ineffective.
A young girl develops a tumor that secretes excess estrogen. Predict the effect of this excessive secretion on her bone growth and final height.
A young girl with excessive estrogen secretion is likely to have a significant increase in longitudinal bone growth, but is also likely to suffer from premature closure of the epiphyseal plates. Her height would increase in the short term, but her adult height might be less than average
How do bone resorption and bone deposition differ?
Bone deposition is the process of forming new bone materials while bone resorption is the process of breaking old or damaged bones.Osteoblasts are responsible for bone deposition while osteoclasts are responsible for bone resorption.
How can excessive growth hormone increase the size of bones even after the epiphyseal plates have closed?
Growth hormone also promotes appositional bone growth, so if it is secreted in excess, the bones will grow in width, even if they can no longer grow in length
Look at figure 6.2 and classify the following bones as long, sort, flat, or irregular. 1) Humerus 2) Phalanges 3) Ribs 4) Carpals 5) Pelvis
Humerus= Long Phalanges= Long Ribs= Flat Carpals= Short Pelvis= Irregular
Predict how the characteristics of a person's bones would change if compact bone were located on the inside and spongy bone on the outside
If the spongy bone were on the outside, the thin trabeculae would be subjected to more mechanical trauma than usual, which would damage their structure. In addition, the bone marrow housed within the trabeculae could also sustain damage without the outer shell of compact bone to protect it
For each type of ossification: Does spongey bone or compact bone come first?
Intramembranous- Spongey Endochondral- compact
For each type of ossification: which bones form by each type?
Intramembranous- collarbones; the patella or kneecap; the parietal, frontal, occipital and temporal bones in the skull; and the upper and lower jawbones Endochondral- Bones at the base of the skull and long bones
For each type of ossification: What is the model for ossification?
Intramembranous- mesenchymal cells Endochondral- Hyaline cartilage
Why do you think that astronauts are often faced with decreased bone mass after returning from periods of prolonged weightlessness?
Load-bearing exercise exerts compression and tension on bones, which increases osteoblast activity. Astronauts in space for a long period are not able to engage in load-bearing activities, and so their osteoblasts are less stimulated than normal, leading to reduced bone mass
how is appositional growth different from longitudinal growth?
Longitudinal -> only long bones in epi. plate -> growth in length Appositional -> All bones -> growth in width
Lucy Dupre is a 2-year-old girl living in northern Canada. You notice that her growth seems abnormally slow and she has exhibited signs of weakened bones, including fractures. Her parents admit they have not supplemented her diet with vitamin D, as they feel that any supplementation is "unnatural" and "not organic." Explain why Lucy is having problems with her bones and bone growth
Lucy lives in an environment in northern Canada where she likely receives inadequate amounts of ultraviolet radiation. This has decreased the amount of vitamin D synthesis taking place in her skin. This decrease, combined with the lack of vitamin D supplementation, has resulted in a severe lack of vitamin D overall and the consequent leaching of calcium ions out of her bones. Such a condition has led to her stunted growth and weakened bones.
Fouz Akkad is a 6-year-old girl who has been diagnosed with a rare genetic defect in which her lysosomes are unable to maintain an acidic pH. What are lysosomes? Why do lysosomes require an acidic pH? How will this affect the ability of certain bone cells to function? What consequences will this disease have on Fouz's bones?
Lysosomes are organelles that generally perform digestive functions. Their main enzymes for catalyzing these breakdown reactions are functional only at an acidic pH. The lysosomes of osteoclasts contain enzymes responsible for catalyzing reactions that break down the organic component of bone. If the lysosomes are unable to maintain an acidic pH, these enzymes cannot function. This will lead to an imbalance in which bone deposition abnormally dominates bone resorption.
Predict what would happen if osteoclasts did not function properly during endochondral and intramembranous ossification
Osteoclasts function in both types of ossification to resorb the initial primary bone so that it can be replaced with secondary bone. If osteoclasts failed to function, the weaker, less organized primary bone would remain instead of being replaced.
How do primary bone and secondary bone differ?
Primary bone is much weaker than secondary bone because it has little inorganic matrix, which makes it much less able to resist compressive forces. In addition, the irregularly arranged collagen bundles make primary bone less resistant to tensile forces, which further weakens it.
Predict what would happen if primary bone were not replaced by secondary bone.
Primary bone is much weaker than secondary bone because it has little inorganic matrix, which makes it much less able to resist compressive forces. In addition, the irregularly arranged collagen bundles make primary bone less resistant to tensile forces, which further weakens it.
What are primary and secondary bone, and how do they differ?
Primary bone is the first bone tissue that appears in embryonic development and in fracture repair Secondary bone replaces primary bone, its stronger
Lamalle
Rings of bone matrix
Central Canal
Runs down the center of the osteon, contains blood vessles
what are the primary functions of the skeletal system?
Structure, Movement, Protection, Blood Cell Production, Storage.
Explain why young men who take anabolic steroids (which mimic the actions of testosterone) often display stunted growth and have an overall shorter stature.
Testosterone and other anabolic steroids accelerate the closure of the epiphyseal plates. If anabolic steroids are taken during adolescence, the elevated levels of androgens will cause the plates to close even more rapidly, which will lead to shorter stature.
How is bone growth effected by the sex hormones estrogen and testosterone?
Testosterone increases appositional bone growth, causing bones in males to become much thicker and have greater calcium salt deposits than bones in females estrogen increases the rate of longitudinal bone growth and inhibits osteoclasts
Malnutrition in children often leads to a decreased rate of mitosis in different cell populations. What effect would this have on growth at the epiphyseal plate? Explain.
The decreased rate of mitosis would reduce the number of chondroblasts at the epiphyseal plate, and therefore slow the production of hyaline cartilage and the longitudinal growth of the bones. In addition, malnutrition would lead to an insufficient intake of calcium salts, vitamin D, vitamin C, and other nutrients needed for ossification, which could weaken the bones and further delay their growth
How could a disease that affects primarily cartilage impact bone growth and bone formation?
The epiphyseal plate is composed of hyaline cartilage. Any disease that affects hyaline cartilage will impair the function of the epiphyseal plate, and therefore the structure and function of the bone as it grows.
Sometimes a bone is injured at the epiphyseal plate. Predict the long-term effect this might have on the injured bone
The epiphyseal plate is the structure from which a bone grows in length. If this structure is damaged, longitudinal growth could be impacted, and the bone on one side of the body could be shorter than the same bone on the other side of the body
How does the structure of compact bone follow its function?
The function of compact bone is to provide a hard outer shell that resists all types of forces and protects the inner spongy bone and marrow. The concentric rings of bone matrix that characterize compact bone make it extremely strong and hard and enable it to perform these function
Predict the potential consequences of damaging the nutrient artery in a bone injury. How would this affect the ability of the bone to heal?
The nutrient artery supplies a good portion of the blood flow to the bone. If this artery is damaged, portions of the bone could be cut off from the normal blood supply, which could lead to further bone injury. A bone with a damaged nutrient artery will take longer to heal
It used to be common practice in surgical fracture repair to strip and remove the periosteum. Now, however, surgeons take great care to avoid damaging the periosteum. Explain why, and describe what would likely happen to bone healing with the periosteum missing.
The periosteum is where the majority of the osteoblasts reside. Osteoblasts are needed in fracture repair to rebuild the bone and bridge the gap between bone fragments. If the periosteum is stripped, bone healing will occur much more slowly because the population of osteoblasts will be dramatically reduced
How could diseases of the kidney, skin, and/or intestines cause diseases of the bone?
The skin is involved in the production of vitamin D, and the kidneys and intestines must be able to absorb calcium ions into the blood. If any of these organs are diseased and unable to perform their functions, levels of vitamin D and/or calcium ions in the blood will be inadequate to maintain bone mass
How does growth hormone affect bone growth?
an increase in the rate of mitosis of chondrocytes in the epiphyseal plate, promoting longitudinal growth an increase in the activity of osteogenic cells, including their activity in the zone of ossification direct stimulation of osteoblasts in the periosteum, triggering appositional growth.
What are the main organs of the skeletal system?
bones, ligaments, tendons, and cartilage. Bones= provide framework, promote mobility, and serve as protection. Ligaments= are fibrous tissues that connect one bone to another. Tendons= fibrous tissue and serve to connect muscles to the bones. Cartilage= flexible connective tissue that protects the bones and helps to form body parts.
what role does parathyroid hormone play in calcium ion homeostasis?
decreased concentration of calcium ions in the blood The response of the feedback loop involves parathyroid hormone. The response to an increase in the number of calcium ions in the blood triggers a different negative feedback loop. The first response is a decline in parathyroid hormone secretion
what are the two types of bone marrow and what are their functions?
red marrow: produces red blood cells, white blood cells, and platelets. ensures that the body always has the proper level of blood cells Yellow marrow: produces fat cells. responsible for storing fats and producing blood cells during life-threatening situations
Perforating canal
runs perpendicular to osteons, contains blood vessels
How does bone grow in length from the epiphyseal plate?
from the division of chondrocytes
Canaliculi
tiny canals, connecting lacunae