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Resources in the University of Michigan Histology Dropbox. There are three major types of muscle, and their structure reflects their function. Skeletal and cardiac muscle cells are called striated muscle because of the very regular arrangement of their intracellular contractile units, sarcomeres, at the light microscope LM and electron microscope EM levels. This regular arrangement imparts a cross-striated or striped appearance.
Such an arrangement is not seen in smooth muscle cells. Skeletal muscle is also called voluntary muscle, because its contraction is under conscious neural control. In contrast, cardiac and smooth muscles are called involuntary muscles because their contractions are either spontaneously generated or are under the control of the autonomic nervous system.
Each of these three types of muscle has a characteristic appearance in both cross and longitudinal sections. You should be able to recognize each type of muscle in both planes of section. In longitudinal sections of skeletal muscle Slide 58 , observe the following :. Again the answer to the question is in the plane of section. Cells with peripheral nuclei that are cut at an angle can appear to have centrally located nuclei. This is why it is important to look at other features of the cell to determine what exactly it is.
It is admittedly difficult to see the Z line and especially the H zone with the light microscope. However, they can be seen clearly on some areas of almost all slides, and it is just necessary to do some looking around for a favorable area on your slide.
Some good areas of skeletal muscle showing cross striations can be found in slide thin View Image. In transverse sections of skeletal muscle cells slide 58 , observe the cylindrical shape of the cells fibers and the peripherally-located nuclei.
Note also the the cytoplasm of the muscle cells has a stippled, punctate appearance which is due to the bundling of thick and thin filaments into myofibrils as mentioned above. Know what exactly is a muscle cell and what's the difference between a muscle fiber and a muscle fibril.
The basic units of muscle are the contractile proteins actin and myosin arranged in sarcomeres. Placed end to end, these sarcomeres form long bands called myofibrils. Within a skeletal muscle cell, the numerous myofibrils are separated by glycogen, mitochondria, and muscle triads two terminal cisternae and a T tubule and other organelles.
Chances are, if you are looking at an electron micrograph of muscle tissue, you are looking at myofibrils. Groups of these fibrils form a muscle fiber, which is surrounded by endomysium.
Muscle fiber and muscle cell are synonymous. Groups of individual cells that are surrounded by perimysium are known as fascicles and groups of these fascicles, surrounded by epimysium make up a muscle. This is a transverse section of an entire fetal forearm, and contains many elements in addition to the muscle, such as nerves and tendons , both of which are, unfortunately, simlarly bundled into fascicles and therefore easily confused with muscle.
So, make sure you're looking at the muscles. Three layers can be seen in slide View Image [see orientation]. Cardiac muscle will be studied in the wall of the ventricle of the heart. In comparison with skeletal muscle, note the following differences. Cardiac muscle cells branch and form a three-dimensional network. These branch points can sometimes be seen in your sections, and you should also note that the muscle fibers are less parallel than in skeletal muscle. Make sure you can differentiate between cardiac and skeletal muscle in both longitudinal and transverse sections!
Slide vagina Masson View Virtual Slide. Smooth muscle may be studied using slide smooth muscle View Image or slide View Image , both in the intestine. To find the muscle layer, look at the at slide at the lowest power this is about the same as looking at the glass slide with the naked eye. The purple layer is largely the epithelium and the lamina propria filled with plasma cell and lymphocytes.
Next to that you see a lighter region of connective tissue the submucosa you looked at to see loose connective tissue and fibroblasts , then a darker pink region which is made up of the two layers of smooth muscle you want to look at.
Slide 29 is a cross section of the intestine, so the inner, circular layer of muscle will have cells oriented longitudinally or, in places, the cells may appear to be oriented more obliquely. Move further out to see the outer sheet of smooth muscle, which runs longitudinally along the intestine, and will therefore be seen in cross section. Look at slide , which is a longitudinal section of the GI tract at the gastro-esophageal junction, to see more smooth muscle in various planes of section.
The smooth muscle in the esophagus the part lined with a stratified, non-keratinizing squamous epithelium sample region from slide View Image is organized in the "classic" inner circular and outer longitudinal arrangement top half in longitudinal section and bottom half in cross section.
Correct answer: Cardiac muscle and skeletal muscle. Explanation : There are three types of muscle tissue. Smooth muscle is not directly related to exercise. Example Question 5 : Muscle Tissue. Possible Answers: Connective, separative, and dissociative. Correct answer: Smooth, skeletal, and cardiac. Explanation : Skeletal muscle is a form of striated muscle under the control of the somatic nervous system voluntary control.
Example Question 6 : Muscle Tissue. Possible Answers: Myofibril, myofilament, muslce fiber. Correct answer: Myofilament, myofibril, muscle fiber. Explanation : This is the correct order because in every muscle fiber there are many myofibrils, and in every myofibril there are many myofilaments.
Example Question 7 : Muscle Tissue. Which of these is NOT a type of muscle tissue? Possible Answers: Cardiac. Correct answer: Epithelial. Explanation : The three types of muscle tissues are: skeletal, cardiac, and smooth. Copyright Notice. View Tutors. Katie Certified Tutor. Jordan Certified Tutor.
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This notification is accurate. I acknowledge that there may be adverse legal consequences for making false or bad faith allegations of copyright infringement by using this process. Find the Best Tutors Do not fill in this field. Cardiac muscle fibers cells also are extensively branched and are connected to one another at their ends by intercalated discs.
An intercalated disc allows the cardiac muscle cells to contract in a wave-like pattern so that the heart can work as a pump. View the University of Michigan WebScope to explore the tissue sample in greater detail. Intercalated discs are part of the sarcolemma and contain two structures important in cardiac muscle contraction: gap junctions and desmosomes.
A gap junction forms channels between adjacent cardiac muscle fibers that allow the depolarizing current produced by cations to flow from one cardiac muscle cell to the next. This joining is called electric coupling, and in cardiac muscle it allows the quick transmission of action potentials and the coordinated contraction of the entire heart. This network of electrically connected cardiac muscle cells creates a functional unit of contraction called a syncytium. The remainder of the intercalated disc is composed of desmosomes.
A desmosome is a cell structure that anchors the ends of cardiac muscle fibers together so the cells do not pull apart during the stress of individual fibers contracting Figure. Contractions of the heart heartbeats are controlled by specialized cardiac muscle cells called pacemaker cells that directly control heart rate. Although cardiac muscle cannot be consciously controlled, the pacemaker cells respond to signals from the autonomic nervous system ANS to speed up or slow down the heart rate.
The pacemaker cells can also respond to various hormones that modulate heart rate to control blood pressure.
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