Skeletal Muscle: Levels of Organization (Nursing)

00:01 Greetings.

00:01 In this lecture we will be discussing the muscular system.

00:07 So first let's talk about the different types of muscles that are found in the body.

00:11 We have skeletal muscle tissue, cardiac muscle tissue, and smooth muscle tissue.

00:19 Of these three types of muscle tissue, we will focus mainly on the skeletal muscles for this lecture.

00:26 We will talk briefly about cardiac muscles and smooth muscles But we will talk more extensively about those in other lectures.

00:36 So, first let's discuss the functions of the muscular tissue.

00:40 The muscle tissue is involved in producing body movements, stabilizing the body's position, storing and mobilizing substances within the body, and also generating heat.

00:55 Other properties as a muscular tissue include electrical excitability, the ability to contract, the ability to extend, and finally, the ability to return back to its normal size or elasticity.

01:13 So now let's look at the structural organization of our skeletal muscles.

01:19 Starting with the largest part, the actual muscle itself.

01:24 This organ is made up of vesicles that are going to contain muscle fibers as well as blood vessels, nerves, and all of this is wrapped in a connective tissue layer known as the epimysium.

01:38 If we go inside or the next smallest unit of the muscle, we have the fascicles.

01:45 This is going to be a bundle of muscle fibers that are wrapped in a connective tissue layer known as the perimysium.

01:52 If you like pulled pork, you are actually looking at the individual fascicles of the muscle.

02:01 The third level or the next smallest level is going to be the muscle fiber itself.

02:07 We actually refer to muscle cells as muscle fibers.

02:12 And this is because of the shape and the organization of the cells.

02:17 In the muscle fiber we start out with a connective tissue layer known as the endomysium.

02:24 Inside of that we have the sarcolemma.

02:27 The sarcolemma would be synonymous with the plasma membrane of a regular cell.

02:34 Inside of the sarcolemma, we have the sarcoplasm, which is synonymous with the cytoplasm of a regular cell.

02:42 Also inside of the cell, we have myofibrils, which are the contractile units of the muscle, as well as multiple nuclei, which is unique to muscle cells.

02:53 We also have mitochondria which are very important for allowing us to have the energy for our muscles to contract.

03:00 And other structures include transverse tubules, the sarcoplasmic reticulum, and the terminal cisterns, which are going to be very important for bringing in calcium so that we can undergo a muscle contraction.

03:14 When you look at a muscle fiber, it has a striated or striped appearance.

03:19 We'll discuss why this is later.

03:23 The final and smallest unit of the muscle is going to be the myofibril.

03:28 As I said, this is a contractile unit of the muscle.

03:32 This threadlike contractile element is going to be found within the sarcoplasm of the muscle fiber and it's going to extend the entire length of the fiber.

03:42 Within the myofibril.

03:44 We have several different filaments including thick and thin filaments.

03:49 We'll discuss these in more detail shortly.

03:54 So speaking of the filaments of the muscle, we have the thick filaments which are going to be composed of a protien known as myosin, and then the thin filaments which are composed of a protein known as actin.

04:07 There are also several regulatory proteins including tropomyosin and troponin.

04:14 This part of the myofibril these filaments are going to be what we use in order for our muscles to contract or shorten.