Part I: Margaret’s Broken Hip
Margaret Donovan, a 72-year-old female, was brought to the emergency room by her son-in-law after falling in her bathtub. She was previously in good health, despite leading a relatively sedentary lifestyle ad having a 30-pack-year history of cigarette smoking. She fell upon entering the bathtub when her right leg slipped out from under her; she landed on her right hip. There was no trauma to the head, nor does she complain of right or left wrist pain. However, she reports severe pain in the right hip and upper thigh, and was unable to get up after her fall. After an injection of pain medication, she was taken to the radiology department to get an x-ray of her right leg and hip. The x-ray revealed an intertrochanteric fracture of the right hip and osteoporotic changes in the femur, tibia, and fibula.
1. Look ahead in your textbook to Chapter 8 and find a picture of a femur. Can you determine the most likely site of the break?
2. The femur is an example of a long bone. What are the three main areas of a long bone? Where would you find compact bone in a long bone? Where would you find spongy bone in a long bone?
3. Explain how the arrangement of spongy and compact bone allow the femur to withstand stresses from many directions.
4. Why was Margaret’s femur more likely to break than a normal femur? Explain the cause for Margaret’s loss of bone mass by discussing her risk factors (e.g. age and sedentary lifestyle) and how they affect the bone remodeling process.
5. The doctor suggests that Margaret avoids long periods of bed rest and to begin weight-bearing activities as soon as possible. Why?
6. Describe the changes that a broken bone undergoes as it is healing.
Steps in repair:
A. fracture hematoma (i.e. blood clot) forms
B. soft tissue callus
• fibroblasts and osteoblasts migrate in from the periosteum and (1st 3 to 4 weeks) endosteum
• fibroblasts lay down a collagen matrix - some of the fibroblasts differentiate into chondroblasts (i.e. cartilage-forming cells) and lay down a fibrocartilage splint (i.e. soft tissue callus)
C. bony callus - osteoblasts begin to replace the fibrocartilage splint with spongy bone, forming a bulge that is initially wider than the after the injury.
7. Margaret’s doctor has told her to start taking oral calcium supplementation. What is required in order for Margaret’s digestive system to absorb the calcium into her body? Then, describe the role of blood calcium homeostasis and how the homeostatic mechanisms to control blood calcium can affect the bones.
8. Margaret’s doctor also puts Margaret on oral estrogen therapy. Why?

Part II: Bone Growth & Hormones
1. A race between two runners is often used as an analogy to describe the mechanism of endochondral ossification. Review endochondral ossification. In endochondral ossification, who are the two runners? Did each runner begin the race at the same time? Who is in the lead at the beginning? How does the race end?
2. What roles do osteoclasts and osteocytes play in endochondral ossification?
3. 8-year-old Sandra breaks her leg in a car accident. X-rays indicate that her left femur is fractured at the epiphyseal plate. The bone fracture eventually heals. Years later, Sandra begins to notice that her right leg is slightly longer than her left leg. What might account for the difference in length between Sandra’s two legs? Explain Sandra’s condition with respect to the race that you described in question #1.
4. 20-year old Sandra begins to worry about her lopsided legs. She wonders if her right leg will continue to grow longer than her left. Sandra consults a doctor who takes an x-ray of each of her femurs. After the x-ray, the doctor informs Sandra that she has reached full height; she should expect no further different in length between the two legs. How did the doctor use the x-rays to determine that Sandra had reached full height?
5. 6-year-old José inherited a disorder that increases the activity of cells in his pituitary gland. Therefore, José experiences an overproduction of growth hormone (GH) before puberty. What effect would you predict this will have on his height? Explain.
6. Russell enters puberty about 5 years later than the average age. What effect would you predict this will have on his height? Explain.
7. Explain why adult women are typically shorter than adult men.

Part I: Margaret’s Broken Hip Margaret Donovan, a 72-year-old fema...