 Hi everyone, this is Leah, your lead course instructor for Advanced E-Clinical Training. And I know you've all been following along now with our anatomy and physiology lessons. And so today we are going to go over the muscular skeletal system. So the muscular skeletal system consists of the skeleton, muscles, cartilage, tendons, ligaments, joints, and other connective tissues. And again, these are all part of the muscular skeletal system. And all of these components work together to provide your body with support, protection, and movement. So some functions of the muscular skeletal system include the bones of the skeletal system help to protect the body's internal organs and support the weight of the body. And it serves as the main storage system for calcium and phosphorus. And then the muscles of the muscular system keep bones in place. They assist with movement by contracting and pulling on the bones. To allow motion, bones are connected by joints, which are connected to other bones and muscle fibers of the connective tissues, such as the tendons and ligaments. And also cartilage prevents the bone ends from rubbing directly on each other. So the muscular skeletal system is actually subdivided into two subdivisions, the skeletal system, and then there's the muscular system. So the skeletal system, again, gives the entire body shape and form and helps to both protect and support the entire body and protect the organs. And then the bone and cartilage tendons, joints, ligaments, and other connected tissues composed of the skeletal system. And then you have the muscular system, and this is an organ system consisting of skeletal muscle, smooth muscle, and cardiac muscle. And the muscular system permits movement of the body, maintains your posture, and helps to circulate blood through the body as well. We are going to first begin by talking about the skeletal system. So the skeleton makes up about 20% of a person's entire body weight. And an adult's skeleton contains 206 bones, and there are also some definite differences between the male and the female skeleton. Obviously, the male skeleton is usually longer and it has a higher bone density or bone mass. And then the female skeleton, on the other hand, has a broader pelvis to accommodate for a pregnancy and childbirth. And the skeletal system is then further broken down into two parts known as the axial skeleton and the appendicular skeleton. So we'll start first by talking about the axial skeleton. As you can see here, that the adult axial skeleton consists of 80 bones. It's made up mostly of the bones that form the vertical axis of the body, such as the bones of the head, the neck, the chest, and spine. The skull bones, as you can see here in this diagram, the adult skull comprises of 22 bones total, and these bones can be further classified by location into cranial bones. There are eight cranial bones, which form the bulk of your skull, and they help to protect your brain. Then you have the facial bones, and there are 14 facial bones, and they're found on the front of the skull and make up the face, as you can see here in this diagram. So this would be the skull bones, and then these are all of the facial bones, all part of the axial skeleton. So the axial skeleton continued. We also have the auditory ossicles, and the auditory ossicles are six smaller bones found within the inner ear canal and the skull that work together to help to transmit sound waves from the environment to the structures of the inner ear. They are known as the three auditory ossicles on each side of the head. Their names are the Malleus, or otherwise known as the Hammer, the Incas, otherwise known as the Anvil, and the Stapes, otherwise known as the Sterob. And again, here in this diagram, you can see all three of these auditory ossicles. So there are six total, three on each side, one in three on the right and then three on the left. Continuing on with the axial skeleton, we have the hyoid bone. And except for the cervical vertebrae, which we'll talk about here next slide, the hyoid bone is the only one located at the anterior of the neck or the front of the neck. And the hyoid bone is a U-shaped bone that is found at the base of the jaw. And it serves as a point of attachment for muscles and ligaments in the neck that help you to turn your head and to swallow. Unlike other bony structures, the hyoid bone does not directly articulate with other bones. So instead, it is connected to neighboring bones by muscular and ligamentous attachments. Continuing on with the axial skeleton, we have the vertebral column or the spine. The vertebral column is made up of 26 bones. The first 24 are all vertebrae followed by the sacrum and the coccyx, otherwise known as the tailbone. The 24 vertebrae can further be divided into the cervical vertebrae, which you can see here. So C1 through C8, and this is at the top of your neck. And then you have the thoracic vertebrae. These 12 bones are found in the upper to mid-back. And that is T1 to T12. And then you have the lumbar vertebrae. And these five bones are found in the lower back. So L1 through L5. And then the sacrum and the coccyx are both made up of several fused vertebrae. They help to support the weight of the body while sitting. And they also serve as attachment points for various ligaments as well. So you could see the sacral vertebrae here. And then lastly, the coccyx, all the way at the bottom, the tailbone. Again, continuing on with the axial skeleton, we have the thoracic cage or the thoracic cavity. And this is made up of the sternum, the breastbone, the really hard flat bone that you can see right here that protects the heart. And 12 pairs of ribs. And these bones form a protective cage around the organs of the upper torso, including the heart and the lungs. And some of the ribs attach directly to the sternum while others are linked to the sternum via cartilage. So some have no attachment point and are referred to as floating ribs. You can see here in this diagram. So next we're going to discuss the appendicular skeleton because as I said before, the skeleton is subdivided into the axial skeleton, which we just discussed. And now the appendicular skeleton beginning with the pectoral girdle here that we'll talk about. But the appendicular skeleton, there are a total of 126 bones in the appendicular skeleton. It consists of the bones that make up the arms, the legs, as well as the bones that attach them to the axial skeleton. So as you can see here, and what's known as the pectoral girdle is where the arms attach to the axial skeleton. And it's made up of the calavicle or the collarbone, which you can see right here. And it's also made up of the scapula or the shoulder blade. And that's this big bone here. It actually kind of looks like an ear in this diagram, but that's not an ear, that's a scapula. And again, there are two of each of these, one on each arm. Continuing with the appendicular skeleton, you have the upper limbs or the arms. Each arm contains 30 bones known as the humerus. That's the long bone of the arm right here. Then you have the radius. And the radius is one of the two longer bones of the forearm found on the thumb side. So right here. And then you have the ulna, and the ulna is the second long bone of the forearm found on the pinky side of the arm, which you can see right here. Then you have the carpals, and the carpals are a group of eight bones found in the wrist, which is right here. You have the metacarpals. The metacarpals are five bones found in the middle area of the hand. And then you have the phalanges. Your phalanges are 14 bones that make up the fingers. Continuing on with the appendicular skeleton. Now you have the pelvic girdle. And the pelvic girdle is commonly known as the hips. It's where the legs attach to the axial skeleton. And it's made up of two hip bones, one for each leg again. And each hip bone consists of three parts known as the ilium, which you can see here. The ischium, which you can see here. And then the pubis bone, which is located in front of the hip bone, which is seen right here. Continuing on with the appendicular skeleton. You have the lower limbs or your legs. Each leg is composed of 30 bones. And you have, of course, the femur, which you can see right here, which is the long big bone of the leg. You have the tibia, and that's the main bone of the lower leg. And that's otherwise known as the shin bone. And then you have the fibula. And that's the second bone of the lower leg found on the outside or the lateral side of the leg, lower leg. That's the smaller bone. Then you have the patella, which is your amicap. And you also have your tarsals. And those are the seven bones that make up the ankle. Like we had the metatarsals. And those are the five bones that make up the middle area of the foot. And then again, you have the phalanges. And those are the 14 bones that are composed, comprised of the toes. Now, I think it's important to know that this skeletal system can, bones in the skeletal system, whether they're the axial bones or the appendicular skeleton can be classified as either a long bone, which help to facilitate movement and support the weight of the body. And these long bones include the major bones of the arms and the legs, such as the humerus and the femur and the tibia and the fibula and the radius and the owner. And then we have short bones. And these short bones help to provide stability and movement within the ankle and the wrist joint. So they provide little to no movement, but these short bones are kind of shaped like cubes and are kind of like as long as they are wide. So some examples of these short bones would include the carpals, the metacarpals and the wrists and then the tarsals and the metatarsals in the ankles. There's the flat bones and the primary purpose of this type of bone is to protect internal organs, such as the brain, the heart and the lungs. And it also provides a large surface area for muscles to attach to. So some examples of this type of bone would be the skull bones, the cranium, the thoracic cage, which would include the sternum and the ribs and the ilium or the pelvis bone. We also have irregular bones and these types of bones vary in size and structure. Irregular bones serve different functions depending on their location. For example, vertebrae protect the spinal cord and together make up the spinal column. Another example would be the hyoid bone, which we talked about being in the front or the anterior part of the neck, which helps to maintain tracheal and pharyngeal support, the muscles attached to that bone to help you with swallowing and turning your neck as well. And then you have a sesamoid bone and that function of the bone is to protect tendons and diminished friction and wear on joint surfaces. So this type of bone is usually smaller and it's found in the hands, the feet, and the knees, a common type of sesamoid bone is the patella or the kneecap. Also, the skeletal system, it's important to understand that the bones can be categorized as cortical bone or spongy bone. You can see here in this picture that cortical bone is a hard outer layer of the bone and it's also called compact bone and it's also much denser than the spongy bone. It forms the hard exterior surface of bones and it gives the bone its smooth white solid appearance. So the compact or the corticobone, cortical bone part of the bone is right here. And then you have the spongy bone and that spongy part of the bone contains the red blood cells that are used in production of red blood cells and it helps in storing the yellow bone marrow which is primarily composed of fat in the medullary cavity which you can see here. Okay, so also there are three layers of bone which consists of the periosteum which is the outer layer that covers all the bones except for the long bones. And then you have that endosteum which is the lining around the innermost layer of the bone then the medullary cavity which is the innermost part of the bone which again holds the bone marrow which we just talked about. And so you can see those layers of the bone here in these pictures. There are also different kinds of cells that make up bone and they're described here. We have osteocytes and these are cells that are the building blocks of the bone. The osteocytes form the inner matrix of the bone tissue that gives bones their strength. You have the osteoclasts and the osteoclasts help to maintain the integrity and strength of the bones. It also helps to break down bone and reabsorb it so that the bones can renew themselves and repair themselves. And then we have osteoblasts which are sort of like the osteoclasts in terms of the process of maintaining the integrity and strength of the bone except osteoblasts build new remodeled bones by producing collagen. And so that the osteocyte can remain healthy and in good functioning condition. And then you have the stem cells of the bone also known as osteogenic cells. And these cells help to form the inner surface of the bone and they are immature osteoblasts that will later transform or mature into osteoblasts. So next we're going to talk about cartilage, cartilage which is part of the skeletal system as we discussed we in the beginning of this lesson. So cartilage is a flexible connective tissue composed of specialized cells called chondrocytes, collagen fibers and elastin fibers. And cartilage is classified into two main compositions. First you have the hyaline cartage which is composed of type two collagen and it also gives the cartilage its glassy appearance. And that's typically found in the nose, the larynx, the trachea and the ribs and then you have elastic cartilage that's like hyaline cartilage but contains more elastic fibers to help move and contract more and it's found in structures such as the ear, the auditory tube and the epiglottis. And then you have fibrocartilage and that's composed of lots of collagen fibers and examples of fibrocartilage included in tervertibral discs, the pubic symphysis and other symphysis throughout the body but here in this picture this is a picture of this would be the femur and this would be the tibia and then here is the fibula. So this would be the knee and you can see the cartilage where it's showing it where it would be here in the knee. Continuing on with the skeletal system we have as part of the system joints and each of the muscular system is connected to one or more bones via the joint. So joints help the bones pivot and allow movements of body parts. So based on the type of tissue that holds the bones together and the range of motions the exhibit joints can be classified into the following. You have synovial joints which are freely mobile joints. Some examples of synovial joints include the knee, the shoulder, sternocleavicular and the elbow joints. And then you have fibrous joints and some examples of fibrous joints are found in the cranial sutures and the tibiofibular joints and then you have cartilaginous joints and these joints are articulations in which the bones are connected by cartilage which we just discussed and these bones have a range of motion between the synovial and the fibrous joints. So if you need to go back and take a look at that joint you can just go back to the previous slide which we showed the knee joints with the cartilage there. So some other tissues and structures that are within the skeletal system include ligaments and ligaments connect to bones at the point where they articulate or move and are near each other. So here in this picture you can see this tendon right here. I'm sorry, you can see this ligament right here. So this ligament is connecting bone to bone and then you have the tendons and tendons are the connective tissues with collagen that connect bones to muscles. So you can see the tendon here, here's the muscle the tendons connecting it to the patella or the knee bone that's right here. And then there's something known as fascia which is also made of connected tissue and it can actually connect muscles to other muscles. And although fascia is really technically part of the subdivision, the muscular system it's being covered here because the composition of fascia is the same as the tendons and ligaments and it plays a similar role in terms of bodily mobility and movement. So moving on to the second subdivision of this muscular skeletal system we just finished up talking about the skeletal system. Now we're going to talk about the muscular system. So the muscular system is responsible for the movement of the human body attached to the bones of the skeletal system are about 708 muscles that make up roughly half of a person's body weight. Muscles are known as either voluntary or involuntary and are also found in the heart and in the digestive system. So the muscles in the muscular system plays several roles which include voluntary bodily movement with skeletal muscles. We have involuntary actions of the body, the organs with the smooth muscles such as within the digestive tract. And then you have involuntary contractions and relaxation of the heart with the cardiac muscle. So here you can see that there are different cells that make up different kinds of muscles in the body which we just previously discussed in the previous slide. The muscular system can be described as having three different types of muscles all of which are anatomically different. So these three types of muscles include the cardiac muscle, skeletal muscle and smooth muscle or otherwise known as visceral muscle. So the cardiac muscle is only found in the heart and we'll talk about that here in these next few slides coming up but I just wanted to show everybody the difference with the cardiac muscles, the smooth or visceral muscle and the skeletal muscle here. So the cardiac muscle obviously is only found in the myocardium of the heart and we did talk about this in the cardiovascular anatomy and physiology lesson. And so we know that from that lesson that the cardiac muscle is responsible for pumping blood throughout the entire body. Cardiac muscle cannot be controlled consciously so meaning like we cannot control by thinking about making our heart beat. So it is known as an involuntary muscle for that reason. The cardiac and the smooth muscles are innervated by the autonomic nervous system that's being controlled involuntarily by the autonomic centers in our brain. And we also did talk about the autonomic nervous system if you remember from the first week when we talked about the nervous system we did talk about the autonomic nervous system and how that controls the involuntary parts of our body meaning the beating of our heart. The cells of the cardiac muscle tissues are what's called striated. That is they appear to have a light and dark stripes when viewed under a light microscope. And cardiac muscle is made from cells called cardiocytes. So you can see the striations here in this cardiac muscle fiber. Moving on to the smooth muscle or a visceral muscle and these muscles are associated with your internal organs. So for this reason it is also referred to as visceral muscle. The name smooth muscle refers to the microscopic appearance of it because it's very smooth. It lacks the striations of the skeletal muscle and of the cardiac muscle as well. So smooth muscle is found in the walls of the hollow organs such as the stomach, the respiratory airways and blood vessels. It's responsible for the involuntary muscle actions associated with movement of the internal organs such as digestion, turning food, moving food through your intestines and your stomach. Also it helps to smooth muscle helps to construct blood vessels and it helps with uterine contractions as well. Moving on to skeletal muscle. So skeletal muscle is the only voluntary muscle tissue in the human body meaning that it is controlled consciously. So if you consciously say that you want to raise your arm that physical action you're consciously performing and that requires skeletal muscle. So the function of skeletal muscle is to contract to move parts of the body closer to the bone that the muscle is attached to. Most skeletal muscles are attached to two bones across a joint. So the muscle serves to move parts of the bones closest to each other. Now in this picture here that you can see that muscular I'm sorry skeletal muscle is striated just like the cardiac muscle and these skeletal muscle fibers are very strong. That's why they're striated. So skeletal muscle actually derives its name from the fact that these muscles always connect to the skeleton and at least one place. I think that it's important to talk about skeletal muscle cell structure since it's so important in how we consciously move our body. So we have right here we have the, I'm sorry the sarcoma and many oval, this is many oval nuclei can be seen just beneath the plasma membrane which is called the sarcoma and the muscle cells. You have the myofibrils and the myofibrils are the nuclei that are pushed aside by long ribbon like organelles which nearly fill the site of plasma. And then you have light and dark bands, alternating dark and light bands along the length of the aligned myofibrils give the muscle salad striped appearance. Then you have the sarcoma and as that you can see right here and then the myofilaments and these are two types of thread like protein myofilaments within each of our box car sarcoma. So the four main physiological properties of skeletal muscle tissue include excitability. So the ability to detect neural stimuli. Also contractability and contractability is the ability to contract and respond to that neural stimulus. And then there's extensibility and this is the ability of the muscle to be stretched without tearing. And then you have elasticity and that is the ability to return to its normal shape after being extended. So the musculoskeletal muscles of the human body are organized into four groups for every region of the body. You first have the muscles of the head and neck which include the muscles that help with facial expression, smiling, frowning. You also have muscles of mastication or chewing, muscles of the orbit. You have to help move your eye, muscles of the tongue, muscles of the pharynx, muscles of the larynx and then muscles of the neck all to help you swallow. You also have the muscles of the trunk which include the muscles of the back, the anterior and lateral abdominal muscles and muscles of the pelvic floor. You also have muscles of the upper limbs which include muscles of the shoulder, of the arm, of the forearm and of the hand. And then you have muscles of the lower limbs which include the hip, the thigh muscles, leg muscles and foot muscles as well. While we're talking about the muscular system it is very important to talk about muscle contraction. And the most important property of skeletal muscles is its ability to contract. So muscle contraction occurs as a result of the interaction of the myofibrils which we just discussed inside the muscle cells. So there are two types of muscle contraction. There is the isometric and the isotonic. And then there are two types of isotonic contractions that are broken down here which is the concentric contraction. And this is in which the muscle shortens due to generating enough force to overcome the overcome resistance. So this would be here the concentric contraction. So you think about lifting a barbell, curling a barbell I should say. And then you have the isocentric contraction in which the muscle stretches due to the resistance being greater than the force the muscle generates. So this would be during this type of contraction the muscle maintains high tension. And this type of contraction usually serves to slow down a movement such as lowering the barbell back down or walking down a hill. There are also several types of muscle movements. First we have flexion as you can see here. So flexion usually means to decrease the angle of the joint and brings two bones closer together. And it's a type of this happens flexion at the hinge joint or otherwise known as the ball and socket joint. So the elbow is the ball and socket joint. So when you are flexing or flexing, this is flexing in extending out is extending your arm all the way out. Then we have rotation is a movement of a bone around a longitudinal axis. It's a common movement of ball and socket joints as well. So if you're thinking about your ankle, if you are turning your right ankle in, that would be a medial rotation, medial leading into the plant of the body. And then you have, if you took your right ankle and you turned it out, rotated it out, that would be a lateral rotation because you are rotating your ankle laterally or away from the body. You also have abduction and abduction is moving the limb away from the midline or medial of the plane. You also have adduction and adduction is the obviously opposite of abduction. So it's a movement of a limb toward body midline. Then you have supination and pronation and supination occurs when the forearm rotates laterally. So the palm of your hand faces anteriorly. And then pronation occurs when the forearm rotates medially so that the palm faces posteriorly or behind. And then lastly, we have special movements, certain movements that did not fit into any of the previous slides or categories and occur only at a few joints. And we have the dorsiflexion and plantar flexion. So lifting the foot so that it's, the surface approaches the shin is called dorsiflex. So if you take your ankle and you lift it all the way up, that's dorsiflex. And whereas depressing the foot is called plantar flexion. So if you're thinking about pressing on a gas pedal, that would be plantar flexion. And then you have inversion and eversion to invert the foot you turn your foot medially or into the plane of the body and to evert the foot you turn the foot laterally or outside of the plane of the body. So this concludes our anatomy and physiology lesson for the muscular skeletal system. Thank you all so much for joining me if you have any questions or if you need clarification about anything. I know it was kind of a long lesson with a lot of detail but please do reach out to me via email or you could always schedule office hours with me on my call in place. So thanks again for listening and we'll see you next week. Bye-bye.