Sunday, March 3, 2024

Luís's Growth Was Influenced By Hormones

 Luís's Growth Was Influenced By Hormones

Epiphyseal growth

In our previous week's module we saw the importance of two hormones - PTH and estrogen - to bone health.  

Estrogen and another hormone, growth hormone, will be relevant to Luís's scenario.

Hopefully you saw in the animation

Links to an external site. and other information on the last page that our bones grow using a process similar to the way our skin grows.  In our epidermis we have a layer of keratinocyte stem cells that continuously divide and push the new cells away - in that case, toward the surface of the skin.  Near the epiphyses of our long bones, we again have rapidly dividing cells.  In this case they are rapidly dividing ("proliferating") chondrocytes.  As they push the new chondrocytes away from them, the cells form stacks that lengthen our bones.  That's how we get taller - lengthening stacks of dividing chondrocytes!  Then the osteoblasts replace the cartilage with bone and the process of bone formation is complete.
 

Growth hormone, which becomes more prevalent during puberty, stimulates division and activity in both chondrocytes and osteoblasts.  As a result, it tends to stimulate a more rapid growth in height.  As you learned last week, estrogen also stimulates osteoblast activity.  But estrogen also shortens the lifespan of chondrocytes!  Estrogen is released in increasing concentrations during puberty in both females and males.  Eventually, all those rapidly dividing chondrocytes in our epiphyses will die off due to the estrogen.  The osteoblasts then replace any remaining cartilage with bone and the epiphyseal cartilage is now gone.  What do you suppose that means for our potential to grow taller later in life?  Remember that this form of bone growth requires a cartilage model to be established first.

MSK1: Bone Formation, Growth, & Remodeling

Bone elongation - processes at the epiphyseal plate

Week 8 - Bone Growth: Explain Bones Are Not Just Calcium???

 
Week 8 - Bone Growth: Explain
Bones Are Not Just Calcium???
 

Before we try to uncover how Luís's bones grew - and why they seem not to be growing taller now - we should remind ourselves of what is in bone.  Most people would quickly point out that our bones are made of calcium.  After all, kids in the United States often hear that they should drink milk to get calcium for strong bones!  While calcium is an important part of our bone tissue, it is not the only or even primary ingredient!  Our bones include a lot of protein, in the form of collagen, which you might remember as a main component of the dermis of our skin and of cartilage.  Collagen is a strong protein with just enough elasticity to provide bones with some resistance to fracture.  In creating bone, our osteoblasts first lay down a collagen mixture, called osteoid.  They then mineralize the bones with a calcium phosphate mixture to make the bone hard.  That's where the calcium comes in!

mineralization of bone

Take a look at the diagram on this page, which shows how we think osteoblasts mineralize bones - a process physiologists still don't entirely understand.  I bring this in, because it shows a couple physiological concepts we studied earlier at work again!  For example, note the arrow on the left showing calcium and phosphate moving through osteoblasts and into the bone.  Physiologists think that osteoblasts use a combination of facilitated diffusion and active transport to shuttle calcium and phosphate from the blood into bone.  Of course, we know one of those methods would be necessary, since calcium and phosphate are charged chemicals (so hydrophilic) and could not move by simple diffusion.  Also note the arrows on the upper right showing two types of cell junctions.  Remember that cell junctions are physical connections between cells formed by membrane proteins.  Physiologists have shown that osteoblasts work in teams with each osteoblast physically connected by cell junctions.  That helps the osteoblast teams coordinate their efforts.

 
Ways of Growing Bones
In this module we will be exploring two different methods our cells have for laying down osteoid and performing mineralization to grow bones.  One of those methods of bone growth, endochondral ossification, is especially relevant to our scenario surrounding Luís and his desire to grow taller later in life.  Endochondral ossification is quite the long and complicated-sounding term, but it's not nearly as tricky as it sounds!  It's most helpful to remember that "chond" refers to cartilage and "os" refers to bone.  Put that together with "endo" (which means "within") and you get the definition of endochondral ossification - within cartilage bone formation.  We're going to try to see how this type of bone formation occurred in Luís's body and why it seems to have stopped.


 Bone Growth & Fractures

fractured fibula

Think about how your skeleton has changed during your life.  Did you ever have a growth spurt where you got much taller over a relatively short time period?  Are you still growing now?  On the other hand, have you ever experienced damage to your bones in the form of fractures?  If so, what caused those fractures and what happened to your bones afterward?  This week we will explore those topics.


This Week's Goals

This week's activities will build directly on your last couple weeks of Scientist Spotlights and online module work.  You will encounter some familiar cells, chemicals, and processes, but will hopefully get to explore that prior knowledge in relation to some new physiological phenomena.


Given all of the above, we will seek to...


Explain to a hypothetical friend why they are unlikely to grow taller late in life.


Make an argument for rigidly immobilizing broken bones based on the physiological steps in fracture healing.


Some Advice!

This week's content includes a decent amount of vocabulary and terminology that can look and sound a bit complicated.  There are some tongue twisters in there!  The strange thing is, most of the ideas and processes the terms describe are not so complicated.  So don't let the funny names cause you anxiety!  The processes aren't too tricky to figure out!


bone AI answer

 Bones are fascinating structures that form the skeletal system in our bodies. Let’s explore some key facts about bones:


What Is a Bone?

A bone is a living, rigid tissue composed of calcified connective tissue.

Within the bone matrix, osteocytes (bone cells) play a crucial role in maintaining bone growth and density.

Calcium and phosphate are stored in bones, strengthening and densifying their structure.

Bones are connected to each other via joints, allowing movement.

The inner core of bones contains either red bone marrow (where blood cells are produced) or yellow bone marrow (filled with adipose tissue).

Bones develop through endochondral and membranous forms, contributing to their unique shapes and functions.

Types of Bones:

Flat Bones: Examples include skull bones. They provide protection and serve as attachment sites for muscles.

Long Bones: The femur (thigh bone) is a classic example. Long bones support body weight and facilitate movement.

Short Bones: Carpal bones in the wrist are short bones. They provide stability and allow fine movements.

Irregular Bones: Vertebrae are irregular bones. Their unique shapes suit specific functions.

Sesamoid Bones: The patella (kneecap) is a sesamoid bone. It forms within tendons and protects joints.

Functions of Bones:

Somatic Rigidity: Bones maintain the body’s shape and provide structural support.

Structural Outline: They define our body’s form and proportions.

Posture Maintenance: Bones contribute to an upright posture.

Movement: Bones, along with muscles, allow us to walk, run, and perform various activities.

Protection: Bones shield internal organs and delicate structures.

Blood Cell Production: Red bone marrow produces blood cells.

Mineral Storage: Bones store essential minerals like calcium and phosphorus.

Remember, bones are more than just rigid structures—they’re essential for our overall well-being! 🦴123


If you have any specific questions about bones or want to explore further, feel free to ask! 

DR. AUGUSTUS WHITE ELIZABETH HOFHEINZ, M.P.H., M.ED. • FRI, SEPTEMBER 24TH, 2010

 Walking through his tightly knit Memphis neighborhood in the late 1940s, Augustus White regularly encountered one question from the concerned elders all around him: “What are you going to do with your life?” Given the extraordinary list of accomplishments that he has achieved, it is safe to assume that Augustus White has made his elders proud. Dr. White is the Ellen and Melvin Gordon Distinguished Professor of Medical Education and professor of orthopedic surgery at Harvard Medical School, winner of the Bronze Star, author of the definitive work on the biomechanics of the spine, and the recipient of numerous orthopedic awards. And through much of it, Augustus White sat at the crossroads of his own personal history and the history of his country…he set out to be his best at a time when the U.S. was far from a place of racial equality. He would not only succeed personally, but would go on to change the fabric of race relations in the medical world.


The first African-American to graduate from Stanford University School of Medicine and the first African-American orthopedic resident at Yale Medical Center, Augustus White grew up in the segregated south. While there were limits imposed by the wider society, in his home, neighborhood, and school, the sky was the only limit. “My inspirational father, who passed away when I was 8 years old, was a doctor, while my mother was a librarian. My teachers were black, and were profoundly dedicated to ensuring that they squeezed every ounce of talent from us. I was later blessed to have an excellent stepfather, who, as a football and boxing coach, taught me the lessons of sportsmanship.”


And his mother turned those into life lessons. “After I lost in a boxing tournament I told my mom, ‘I don’t feel like going to school today.’ Her response was, ‘Are you sick? Can you walk?’ The lesson was: keep going no matter what.”


Augustus White did press on, attending a prep school where everyone worked in exchange for partial tuition reimbursement. “The level of education at Mount Herman was exceptional, and my time there began to teach me that I really might be able to succeed in life.”


Confidence comes in stages…and it was a brief encounter that forever shifted Augustus White’s vision of what his life could be. “When I was in college at Brown I was leaving class one day when the professor said to me, ‘You are a very good student. Come talk to me about doing a research project.’ This simple interaction altered my life course more than anything else. No one had ever told me that I was a good student. I needed that. It was rare then (and now) for a minority student to be told such a thing.”


In part, Dr. White credits his “never be afraid to fail” attitude for pushing him to great professional heights. “I learned early on to put aside any thoughts that I might fail, and kept going. I aimed high, applying for medical school at Harvard and Stanford; I was waitlisted at Harvard, and in the meantime was accepted to Stanford with a full scholarship.”


And why medicine? Because Augustus White’s talent and determination were driven by the emotions of his early days.“As a young boy I considered several options: doctor, teacher, football coach."


It later struck me that whenever I played cops and robbers or other games, and someone was hurt, I always felt sorry for them. I began to like the idea of helping people in need.


After completing internships at the University of Michigan and Stanford, Dr. White entered the Yale orthopedic residency, where he came under the edifying spell of Dr. Wayne Southwick. “Wayne’s ability to mentor should be canned…he brought an unparalleled level of knowledge and wisdom to the residents. I studied spine surgery with him, which eventually led to my obtaining a Ph.D. with the esteemed Dr. Karl Hirch at the Karolinska Institute in Sweden.”


Before that, however, a war intervened. With thoughts of his boyhood in his head, Dr. White penned a note with a solemn promise to Uncle Sam. “Not three weeks after completing my residency I was in Vietnam. I had written myself a note in which I told Uncle Sam that I would give it my all; also, I was excited about my new skills and wanted to do as much surgery as possible. And I was needed. I was five years old when Pearl Harbor was bombed, and I recall marching around to the song ‘Remember Pearl Harbor.’ Over time it became clear that I was alive because others had sacrificed.”


Dr. White signed on to sacrifice his life, if necessary, but not his dignity.


I was a fully trained and confident orthopedic surgeon when I reached Vietnam. Most of the European American doctors I worked with had never competed with an African-American male off the athletic field, and I encountered some hostility.


"I learned the technique of counting to ten before you respond. And I found that there are appropriate times to fight, but that you should give people a chance first. A fundamental tenet of mine is that I treat everyone with respect. If they continue to act poorly, then I decide how to approach them.”


Despite encountering egos and racism, Dr. White took something critical from his military service. “Vietnam pointed up our common humanity. There were no more powerful moments than sitting beside soldiers as they were gradually dying. Also, along with the wonderful Dr. John Feagin, the CEO of our hospital, I worked at a local leper colony. At the military hospital we saw man’s inhumanity to man; at the leper colony we witnessed nature’s inhumanity to man. In the end, however, the common human struggle was evident.”


His sense of duty intact, and his compassion deepened, one day Dr. White put himself even more in harm’s way. “I volunteered to help save a wounded soldier who was stranded on a mountainside. This was in an ‘unsecured’ area, i.e., one that we didn’t control. I knew that I must focus intensely so that I could get the splinting done and we could all get back safely.”


For his bravery and dedication, Dr. White was awarded the Bronze Star. “Having my efforts recognized meant so much, particularly in this patriotic context. I take it as a license to constructively criticize my country when we mess up.”


And when Dr. White himself performed less than perfectly, he learned. “In the melee of helicopters bringing in multiple patients one day, a badly wounded soldier asked me, ‘Am I going to be OK?’ I hurriedly said, ‘Yes, yes, you’ll be fine.’ Although I worked hard to help him, I was wrong…he didn’t make it. That was a significant, difficult lesson. We physicians have to be technicians, but we also must look someone in the eye and be present. Depending on the situation, you may be the last person they interact with.”


As intellectual as he is compassionate, Dr. White is renowned for his standout orthopedic reference book: Clinical Biomechanics of the Spine. “I co-authored the book with Manohar Panjabi, Ph.D. In it, we bring together the biomechanics and clinical care of patients with spine problems. I think it’s fair to say that it is a standard reference for the majority of residents in this country.”


In 2001 Dr. White was honored with the American Orthopaedic Association Alfred R. Shands Jr. Award and Lecture. “In delivering my speech I focused on helping my colleagues change their thinking and behavior with regard to race, pointing out that I was not doing so in the spirit of blame, but of friendship and concern for our patients. After taking my colleagues through a difficult, abbreviated, voyage through the history of racial matters, I asked them to go forth and apply the following criterion to each and every patient: ‘Is this the way I would treat my friend or my family member?’”


Dr. White is devoted to educating others about the unconscious biases in the medical world. He is a founding member of the J. Robert Gladden Orthopaedic Society, a multicultural organization dedicated to advancing excellent musculoskeletal care for all patients. Dr. White also received the American Academy of Orthopaedic Surgeons' AAOS Diversity Award and the AAOS Orthopaedic Research Education Foundation William W. Tipton Jr. M.D. Leadership Award.


I am much inspired by Ruth Simmons, the President of Brown, who says that diversity is an evolving concept. When democracy was in its youth, it was not necessarily what it is now after having been enriched by our desires for progress. So it is with diversity.


Sometimes Dr. White’s first words at the podium are, “Greetings, my fellow humans!” An African-American surgeon, Dr. White is a human being first…and knows that patients get frightened. “I learned something powerful from a surgeon friend of mine who called his patients the night before surgery. Now, I do the same, saying, ‘Mrs. Jones, I wanted to see if you have any last minute questions.’ It takes a mere 30-90 seconds; patients rarely have questions and it means everything to that person that you cared enough to call. I throw in a bit of humor as well, saying, ‘I also thought you’d like to know that I’m sane and sober and intend to get a good night’s sleep.’”


With his genuine nature, warmth, and superb character, Dr. White surely has many fans. But none are more devoted than his wife, three daughters, and two grandchildren. “My wife and I met when I was studying in Sweden. We have one daughter in Stockholm who has a precious little boy. Another daughter lives in Indianapolis and has a delightful 15-month-old; our other daughter lives in Boston. I’m thrilled to enjoy good health, take great enjoyment in music (Jazz and classical), and enjoy traveling to Sweden with my wife.”


Dr. Augustus White…leading the field in its common human struggles and common opportunities for growth.


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