The study of bones involves four classifications: long, short, flat, and irregular. Dense and hard exterior surface bone is called compact or cortical bone, which is a dense, hard outer layer that surrounds the medullary cavity and contains blood vessels and nerves. The medullary cavity has a delicate membranous lining called the endosteum, and the outer surface of bone, except in regions covered with articular cartilage, is covered with a fibrous membrane called the periosteum.
The diaphysis, a hollow region in the bone, is filled with yellow marrow and has walls composed of dense and hard compact bone. The outer walls of the diaphysis are composed of dense and hard compact bone, a form of osseous tissue. The medullary cavity is filled with bone marrow, and the outer walls of the diaphysis are composed of dense and hard compact bone.
The medullary cavity is surrounded by a dense, hard outer layer of cortical bone, which is much denser than cancellous bone. The outer walls of the diaphysis are composed of dense and hard compact bone, a form of osseous tissue. The medullary cavity is surrounded by a solid, hard outside part of the bone, which looks like ivory and is extremely strong.
The end of a long bone is covered by articular cartilage. The dense and hard exterior surface bone is called compact bone. The walls of the diaphysis are composed of dense and hard compact bone. The wider section at each end of the bone is called the epiphysis (plural = epiphyses).
📹 The Skeletal System: Crash Course Anatomy & Physiology #19
Today Hank explains the skeletal system and why astronauts Scott Kelly and Mikhail Kornienko are out in space studying it.
What is the spongy bone also known as?
Cancellous bone, also referred to as spongy or trabecular bone, represents a specific type of bone tissue found within the human body. It is located at the extremities of long bones, pelvic bones, ribs, the skull, and vertebrae within the spinal column.
What is the hard outer surface of bone called?
The periosteum is the outer membrane covering bones, containing tunnels and canals that transport nutrients through blood and lymphatic vessels. It can also support muscles, ligaments, and tendons. Bones are classified by shape, such as long (femur and forearm), short (wrist and ankle), flat (sklood), or irregular (spine). The adult human skeleton consists of 206 bones, excluding teeth and sesamoid bones. These bones include the femur, forearm, wrist, ankle, skull, and spine.
What is the hard outer layer of bone made of?
The hard outer layer of bones, known as cortical bone or compact bone, forms the hard exterior (cortex) and accounts for 80 percent of an adult human skeleton’s total bone mass. Cortical bone is composed of multiple microscopic columns called osteons, which are layers of osteoblasts and osteocytes around a central canal called the osteonic canal. These columns are metabolically active and change as bone is reabsorbed and created.
Cancellous bone, also known as spongy bone, is the internal tissue of skeletal bone and follows the material properties of biofoams. It has a higher surface-area-to-volume ratio than cortical bone and is less dense, making it weaker and more flexible. Cancellous bone is typically found at the ends of long bones, near joints, and in the interior of vertebrae. It is highly vascular and often contains red bone marrow where hematopoiesis, the production of blood cells, occurs.
The primary anatomical and functional unit of cancellous bone is the trabecula, which are thin formations of osteoblasts covered in endosteum. Trabeculae create an irregular network of spaces, including bone marrow and hematopoietic stem cells that give rise to platelets, red blood cells, and white blood cells. Trabecular bone accounts for the remaining 20 percent of total bone mass but has nearly ten times the surface area of compact bone.
The terms “cancellous” and “trabecular” refer to the tiny lattice-shaped units (trabeculae) that form the tissue.
What is the difference between hard bone and spongy bone?
Spongy bone tissue, also known as cancellous bone, is the inner layer of all bones. It consists of trabeculae, lamellae arranged as rods or plates, and red bone marrow. Blood vessels within this tissue deliver nutrients to osteocytes and remove waste. The red bone marrow of the femur and the interior of other large bones form blood cells. Spongy bone reduces bone density and allows long bones to compress due to stresses applied to the bone.
It is prominent in areas of bones not heavily stressed or where stresses arrive from many directions. The epiphyses of bones, such as the neck of the femur, are subject to stress from many directions.
An example of spongy bone tissue is holding a heavy framed picture flat on the floor with a toothpick perpendicular to the floor and the picture. The toothpick transmits the downward pressure of the picture to the wall, breaking off at the wall.
What is the hard dense bone that forms the outer surface of bones?
Bones consist of various layers, including compact bone (cortical bone), cancellous bone (trabecular bone), osteoblasts and osteoocytes (bone-forming cells), osteoclasts (bone-resorbing cells), and osteoid (non-mineral, organic part of the bone matrix made of collagen and non-collagenous proteins). These cells are responsible for bone formation, resorption, maintenance, and remodeling, and are influenced by various factors.
What are the four types of bones?
Bones are made up of connective tissue reinforced with calcium and specialized bone cells. They are divided into three types: long bone, short bone, flat bone, and irregular bone. Long bones are long, thin, and include the bones of arms and legs. Short bones have a squat, cubed shape, flat bones have a flattened, broad surface, and irregular bones have a shape that does not conform to these types. Healthy bone requires a balanced diet, regular weight-bearing exercise, and the right levels of hormones.
What is dense bone called?
The skeletal structure consists of cortical bone, which makes up about three-quarters of the total skeletal mass, and trabecular bone, which makes up 25%. The bony skeleton serves both structural and reservoir functions, providing mobility, support, and protection. During childhood and adolescence, bones undergo modeling, allowing for the formation of new bone and removal of old bone. This process allows individual bones to grow in size and shift in space.
The remodeling process, which involves removal and replacement at the same site, occurs throughout life and becomes dominant by the time bone reaches its peak mass. Most adult skeletons are replaced about every 10 years.
What is the external portion of the bone called?
The periosteum is the outer covering of bones, covering the entire surface except for ligament attachment, tendon attachment, and an area covered by articulating cartilage. It is absent in sesamoid bones. Bones are specialized, living connective tissues that support and protect vital organs. They are classified into two types: cortical or compact bone, which has a bone marrow cavity and is walled by dense material, and cancellous bone or spongy bone. Bones are composed of specialized, living connective tissue that provides support and protection to the body.
What is the hard exterior surface of bone?
The periosteum is the outer membrane covering bones, containing tunnels and canals that transport nutrients through blood and lymphatic vessels. It can also support muscles, ligaments, and tendons. Bones are classified by shape, such as long (femur and forearm), short (wrist and ankle), flat (sklood), or irregular (spine). The adult human skeleton consists of 206 bones, excluding teeth and sesamoid bones. These bones include the femur, forearm, wrist, ankle, skull, and spine.
What is the dense hard exterior of the bone?
Compact bone is the dense outer part of a bone, containing blood vessels and nerves. The medullary cavity is the hollow part containing bone marrow. Long bones, such as the humerus, ulna, and radius in arms and the femur, tibia, and fibula in legs, act as levers for movement. Short bones provide support and movement assistance in wrists and ankles. Flat bones, such as the skull, breast bone, and ribs, shield and protect important organs.
📹 Structure of Bone | Lamellar Bone | Compact and Cancellous Bone | Bone Histology
This video is on the structure of bone, the layers and the arrangement of bone tissue forming lamellar bone. I hope it helps!
Bones: Made of active connective tissue Stores calcium phosphate and minerals Hematopoiesis~blood cell production 206 bones Axial or perpendicular | | Vertical. Appendages/others Shape: Long bones longer than wide Short bones short cube like Flat bones thin ones Irregular bones can’t classify Compact bone smooth Spongey porous: cross hatching supports (trabeculae)~resist stress & bone marrow red=blood cells yellow =fat Flared ends=epiphyses Middle=dialysis Middle layer=medullary cavity Osteons: cylindrical/weight baring/cented of bone (animation of bone being cut in half they are outside the center hole of bone, and appear to be like frog eggs) Each “frog egg” is a lamellae and filled with collagen fibers that run in same directions. Central canals: hold nerves and blood vessels~nutrients Lucanae spaces by central canals~astrocytes: mature bone cells that monitor and maintain your bone matrix Bone remodeling~ Osteo blasts & Osteo clasts #1. O. Blasts: bone makers Cartilage is framework for bone #2. O. Clasts: bone breakers ~resorption, apoptosis (self destruct)
As a nursing student, we constantly have to go back to anatomy and physiology to understand what happens during disease processes. These articles are super helpful and so much more convenient compared to flipping books open. Thanks so much for these! I was super impressed by how detailed and accurate your A&P articles are.
I’m finally going to reach out and thank you via a comment… little do you know, I am a nursing student and I have used your articles for every biology course I’ve had to take as a quick refresher before exams. I cannot thank you enough for these articles! You explain it in a language that I can understand as opposed to the boring lull of the borderline medical journal of a textbook that I have! (why do they insist on being so sleep provoking?!) So, THANK YOU, your website rocks and I recommend them to all my fellow students that need a quick rehash. 🙂
Hank you honestly are my favourite everything! You are helping me through SO many classes where my teacher sounds like hes speaking friggin German when explaining anatomy. When I become an RMT, you have a free massage ready for you as a thank you!!!! I had NO idea just how medical this profession is going to be or the training to get there. You are saving me!
Spooky, scary skeletons ♫♪ send shivers down your spine♫♪ Shrieking skulls will shock your soul ♫♪ Seal your doom tonight ♫♪ Spooky, scary skeletons ♫♪ speak with such a screech ♫♪ You’ll shake and shudder in surprise ♫♪ when you hear these zombies shriek ♫♪ We’re so sorry, skeletons♫♪ You’re so misunderstood ♫♪ You only want to socialize ♫♪ (but I don’t think we should) ‘Cause Spooky, scary skeletons ♫♪ shout startling, shrilly screams ♫♪ They’ll sneak from their sarcophagus ♫♪ and just won’t leave you be ♫♪ Spirits, supernatural ♫♪ are shy, what’s all the fuss? ♫♪ But bags of bones seem so unsafe ♫♪ It’s semi-serious! ♫♪ Spooky, scary skeletons ♫♪ are silly all the same ♫♪ They’ll smile and scrabble slowly by ♫♪ and drive you so insane! ♫♪ Sticks and stones will break your bones ♫♪ They seldom let you snooze ♫♪ Spooky, scary skeletons ♫♪ will wake you with a BOO! ♫♪♫♪♫♪♫♪♫♪♫♪♫♪♫♪♫♪♫♪♫♪♫♪♫♪♫♪♫♪♫♪♫♪♫♪♫♪♫♪
To all the people saying he needs to talk slower please shut up and pause the article or rewind and contemplate what he is saying. The beauty in his articles is they are so short because he speaks so quickly and includes so much information in such a small set. He teaches what it takes my teacher in two hours in ten minutes.. again shut up !!
I have to do a 20 slide “slideshow” for a final. My textbook is so confusing. literally bolds and italicizes everything that is important. Crash course is the only reason I’ll be passing this year. I’m just perusal these articles. I won’t even bother reading. Thank you Crash Course! You guys are the absolute best!
Even though certain life circumstances prevented me from pursuing my lifetime goal of becoming a physician, I still love learning all I can about our miraculous human form! I am especially interested in diseases and rare diseases that can, and do, afflict our mortal selves and the advances (and failures) that so many dedicated researchers, scientists, physicians and nurses have devoted their careers to understand, and to hopefully discover the treatments and cures so many us are looking forward to! Kudo’s to you all!
Great Job. I started teaching Massage Therapy. Your Anatomy & Physiology articles are great for my class. I give them as homework assignments to review and it really helps them understand the systems better. Keep up the great work. I haven’t seen all your articles yet because I just recently found your website on YouTube. But do you guys have or plan to make anything on Kinesiology?
I have a hypothesis id like to express, my idea is that while in null g or zero g the bone cells are tricked into thinking that your in the fulid cavity called the womb, that simulates null g. Why do i say this, well i personally talked to a nurse friend of mine and he mentioned that newborns have very rubbery skeletons, more cartilage and connective tissue than calcium phosphate that is our bones. If our bones think there in a womb like state then they want to get ready for birth, that involves reducing the mass of our bones in our body. It is just a hypothesis, if anyone has anything thed like to add I welcome it.pardon any grammatical mistakes it natural.
I watched this article with my daughter, she is 3 and fascinated with bones, as well as many other things. During the article she had many questions, about bones and blood and dinosaurs, but one that I could not answer for her, what is the skeletons name? She told me to type “Hank, I wanted to know what the skeletons name was. Thank you. From Lizzy” If anyone could answer this she would be very happy.
I’m probably wrong since I have no real education in this field but if I were to guess as to why micro gravity results in more bone “breaking” rather than making, and using information from this article itself?.. I’d say it’s that the system is detecting the weak gravity like a form of damage or otherwise a threat to the bone, it is then breaking down the bone without replacing it so it will have the materials to do so when regular gravity comes back into play?
Wow guys !! You are doing a very super job 💖🙏🏻 .. I’m really happy, because the informations that I have got in this article are so much 👌🏻😭 .. I was searching about something like this from long time ! 🥺 I’m thankful for you all of us guys.. Keep going, I will support you always 🙏🏻🌹 .. And I will be waiting for more interesting articles from you guys 😆👍🏻 ..
Great article. In space, is it possible the body is rapidly recalibrating the need for bone density and therefore breaking down bone quickly as it thinks the bone is no longer needed (redirecting resources elsewhere)? Form following function….zero gravity is very extreme so you are seeing an extreme reaction. Just from a causal observer pov, i don’t think exercise will be enough to reverse 1-2% bone loss per month. Some kind of artificial gravity environment (ala star trek) would ultimately be required for extended periods in space. Need to figure that out before you even think about a Mars trip. Don’t ask me how that’s done. haha
Hank and the Crashcourse team: I already yelled at the Scishow Space team twice about mispronouncing the Russian name “Mikhail.” I don’t expect perfect Russian pronunciation, but pronouncing it like “Mi-kale” is pretty bad. Saying “Mi-ha-EEL” (with three syllables, H-sound rather than K-sound), is much closer to the correct pronunciation.
I’m a Pre-med student starting medicine soon. Our Prof came today and said “you guys have been performing excellently so far, lets throw in some MD anatomy in your skeletal system content, you’ll thank me later”. Long story short, here i am learning about the skeletal system and then I gotta learn the name of 50 bones after this article. Feelsbadman
Great episode as always! I met John Glenn sometime around 1996 and he’d gone up on the shuttle as part of an experiment on physiologic changes in space. He’d had to work out on a stationary bike every day at regular intervals. He said an extra bonus was that he was a few nanoseconds (milliseconds? I can’t remember) younger than he should have been because of relativity. I also recall that he was taller than I expected.
206 bones, let just go over 5 of them in the article… AHH!!! How am I supposed to memorized all the bones… and all the part of each bone.. and spell all the name correctly!!! UGHHHHH tests are so hard!! 8 bones in the wrist… 7 in the tarsals… 42 in the head… with different holes known as foramens… and sutures.. and condyles… canals… processes.. fossas… JEEZZ
Ok. So I don’t know what the hell my bio teacher does to her tests but I fail almost all of them. Thanks to this I do understand the material but I still fail her tests. If you ask me any question, I could answer you but. Idk. I am passing the class tho. And I know it’s just her bc I have straight A’s in every single class except her class. And I just wished I knew what she does to them damn tests. Like. I just. Want. To. Understand!!
These articles really make me wonder how did a bunch of molecules decide to do all these complicated forms? I’m a somewhat Agonist Normally I believe if god existed and made the universe we were mere side effect and we’re not the center of her creation. but then again seeing this makes me think god engineered living beings. What do you guys think? Talking to atheist, agonists, deists… You Religous people, please shut the fuck up. Edit: why I call god her is because I think of her as a really hot chick!
The body eats through its bone mass in prolonged zero gravity for the same reason that it shrinks muscles cells when we stop exercising: because the body does not need it. The human body is designed at a fundamental level to survive, and it will do all it can to maximize chances of survival. And one of the most common reasons for dying is not having enough calories to sustain life. So the body looks for ways to use as little energy as possible. This miserly behavior is exhibited to great effect by the creation and destruction of tissue on the basis of necessity. If you’re not using those muscles as much, the body will shrink the muscles down to a level more in tune with its current needs, because every cell in the body requires calories, and unlike the state, the body isn’t going to pay its people to do nothing. If more stress is put on the muscles – or in this case the bones – then the body will repair the damage and build it stronger for next time. But it’ll only keep it strong so long as that strength is needed. This is why one must keep a regular exercise regiment to prevent muscle atrophy, and why astronauts in space lose bone mass. The body sees that the bone mass is not needed as much, and works to cut back on it. The problem, of course, arises both because that bone mass is necessary for general survival (creating blood cells and all), and because the person will eventually return to Earth and suffer for the bone lost.
If you were able to put one of those GForce simulators onto the space station safely somehow. Assuming you pressurized the cabin of the simulator. Could that potentially help prevent bone loss in astronauts? You would just need to spin it enough so that the person would experience the effects of gravity. It would need to be a little stronger than 1G. Enough G’s will press them hard against the wall but I imagine if you dialed it back to a certain threshold a person could somewhat comfortably stand sideways. Simulating the stress of gravity. This could intern help stave off bone loss if an astronaut uses it frequently. Just a thought though…
But isnt kinda obvious. Your osteoclast destroy your bones because why do you need mote bone if you need less weight in microgravity situations? So they wouldnt have a need to activate osteoblasts to rebuild the bone because your not doing anything. Your bones dont have a lot of weight bearing support needed. The pelvic girdle, the femur, legs and arms all start deteriating because they barely have to left anything. Same with muscles. I would be surprised their muscles didn’t deteriorate.
For those of you saying he speaks too fast… I have a suggestion. Make your note cards, memorize the definitions and what these things are… and then review the article. He speaks fast, but if you are familiar with the content, it can really help make connections and see how it all relates together…. hope it helps
so learning from the articles basically, the cells are the one that makes you strong, healthy, and even young and when you get older the cells get weaker and weaker and you experience memory lose (because you losing brain cells) bone gets weaker (because you lose bone cells) you get old skin (because your loseing skin cells).
I was wondering if you could share you’re sources on bone remodeling, because I am currently in a research group that is looking into that and how the osteoblasts and osteoclasts know where to remove or make bone. It has not been confirmed whether it is a mechanical or a chemical stimulus. Also there has not been shown to be a significant correlation between locations of microdamage, resorption cavities and high strains. What you said in the article makes sense and is what we are trying to prove, but a relationship has yet to be shown, at least in cancellous bone.
For me as a teacher, these articles are excelent. Unfortunatelly, such a fast way of speaking does not help my non-native english speaking students’ understanding. I hope, in the upcoming articles, you could improve this aspect for everyone to be able to understand clearly your great explanations. Best regards!
At first glance studying human anatomy may appear extremely complicated. It is tru?e that it is not simple and your studies wont change that. As for it being overwhelming, this can be solved if you take your study one step at a time. I discovered an article on Sebs Study Crammer extremely helpful for this.
I’m loving CC A&P, Biology and Chemistry its helping me to understand how bones grow/repair which is something i’m particularly interested in at the moment due to having a broken femur. It’s helpful to know whats going on right under my skin at this very moment and what i can do to make sure it grows back to full strength. CC A&P has helped translate some of the Doctor speak to English which i’m really thankful for. Keep up the good work and DFTBA (if I had money spare it would sub on Patreon)
I just had an really important exam in my life that can determine my future (its a national exam) two weeks ago, and this particular lesson ( also the nervous etc) appeared as question in those exam. If only this lesson came quicker, I can study from this for it… But I understand how hard it is to even just make a 10 minute show script… Sorry
Love these articles! Quick question though: when you say astronauts lose 1-2% of their bone mass every month, is that cumulative? Like… after the second month (and after the astronaut lost 1-2% of their original bones mass in the first month,) is the astronaut going to lose another 1-2% of their original bone mass, or 1-2% of their new bone mass?
This was the first episode of the entire list I’ve seen & WOW! I never knew alot of this & I was able to understand it better. The only thing that threw me off was that he talks super fast & bubbles don’t stay long enough to read. I’m definitely going to use this series to study my Anatomy & Physiology!
I am a pharmacy student, but i enjoy learning these things which I also learned in my course with you! your notes and handwriting are neat, simple and pretty. Don’t stop teaching us! ❤ You’re definitely will get excellent academic results bcs you are kind. Thank you. BTW those pictures are drawn by you or sticker? may I ask how u get it, I see you are using goodnotes same as me
May I say that certain osteoblasts present in cellular layer of periosteum move down and start producing straight layers of bone matrix which are called as circumstantial lamellae and concentric layers of bone matrix called as concentric lamellae…. around them…while in between circumstantial and concentric lamellae certain ring shaped spaces called as lacunae left where these osteoblasts stuck themselves in the lamellae and mature themselves and then they are called as osteocytes … These lamellae are perforated by horizontal Volkmann’s cannals which connect haversian pores of osteons??. Is that understanding is right 🥹🥺😢😢