Muscle Cell Report (Human Biology) PDF

University of Imam Jaafar Al-Sadiq Faculty of Medical Technologies Department of Pathological Analysis Group: D2 Muscle cell Preparation by : Athraa Amer Edan Supervisor: Dr.haider Abbas 14...

University of Imam Jaafar Al-Sadiq Faculty of Medical Technologies Department of Pathological Analysis Group: D2 Muscle cell Preparation by : Athraa Amer Edan Supervisor: Dr.haider Abbas 1445AH 2024AD Introduction: The muscle cell, also known as the myocyte is the smallest subunit of all muscular tissues and organs throughout the body. It is here in the myocyte, where the physiological steps of muscle contraction and where the pathophysiology of numerous muscular diseases takes place. There are three types of muscle cells in the human body: skeletal, smooth, and cardiac muscle. The common function of each specialized myocyte is the contraction of their various organs, some essential for life. Therefore, dysregulation of these crucial functions can lead to significant morbidity and mortality. This article examines the role of the muscle myocyte in various systems, the physiology of myocyte contraction and the pathophysiology of diseases involving the myocyte Structure The anatomy of muscle cells differs from that of other body cells and biologists have applied specific terminology to different parts of these cells. The cell membrane of a muscle cell is known as the sarcolemma and the cytoplasm is called sarcoplasm. The sarcoplasm contains myoglobin, an oxygen storage site, as well as glycogen in the form of granules in the cytosol, which both provide an energy supply. Sarcoplasm also contains many tubular protein structures called myofibrils, which are made up of myofilaments. There are 3 types of myofilament; thick, thin, and elastic. Thick myofilaments are made from myosin, a type of motor protein, whilst thin myofilaments are made from actin , another type of protein used by cells for structure. Elastic myofilaments are composed of a springy form of anchoring protein known as titin. Together these myofilaments work to create muscle contractions by allowing the myosin protein heads to walk along the actin filaments creating a sliding action. The basic unit of striated (striped) muscle is a sarcomere comprised of actin (light bands) and myosin (dark bands) filaments. Functions Movement Skeletal muscles pull on the bones causing movements at the joints. Skeletal muscles pull on the soft tissues of the face causing facial expressions. Movement caused by the respiratory muscles enables breathing. Support Muscles of the body wall support the internal organs. As these muscles lose their tone, the internal organs of the abdominal-pelvic cavity may bulge outward as seen in some individuals as they age. Protection Heat is a waste product of muscle metabolism, which helps maintain an internal body temperature of 98.6 F. Shivering is a mechanism of the muscular system that generates heat to warm an overly cooled body. Heat generation Heat is a waste product of muscle metabolism, which helps maintain an internal body temperature of 98.6 F. Shivering is a mechanism of the muscular system that generates heat to warm an overly cooled body. Blood circulation Cardiac muscles aid pumping action of the heart by aiding blood circulation. Types of muscle cells 1-Skeletal muscle cells Skeletal muscle cells are long, cylindrical, and striated. They are multinucleated meaning that they have more than one nucleus. This is because they are formed from the fusion of embryonic myoblasts. Each nucleus regulates the metabolic requirements of the sarcoplasm around it. Skeletal muscle cells have high energy requirements, so they contain many mitochondria in order to generate sufficient ATP.Skeletal muscle cells, a striated muscle cell type, form the muscle that we use to move, and are compartmentalized into different muscle tissues around the body, such as that of the biceps Skeletal muscles are attached to bones by tendoms and can be as long as 30 cm, although they are usually 2 to 3 cm in length. 2-Cardiac muscle cells Cardiomyocytes are short and narrow, and fairly rectangular in shape. They are around 0.02 mm wide and 0.1 mm (millimeters) long. Cardiomyocytes contain many sarcosomes, which provide the required energy for contraction. Unlike skeletal muscle cells, cardiomyocytes normally contain a single nucleus. Cardiomyocytes generally contain the same cell organelles as skeletal muscle cells, although they contain more sarcosomes.Cardiomyocytes are large and muscular, and are structurally connected by intercalated discs which have gap junctions for diffusion and communication. The discs appear as dark bands between cells and are a unique aspect of cardiomyocytes. They result from membranes of adjacent myocytes being very close together, and form a kind of glue between cells. This allows the transmissionof contractile force between cells as electrical depolarization propagates from cell to cell. The key role of cardiomyocytes is to generate enough contractile force for the heart to beat effectively. They contract together in unison, causing enough pressure to force blood around the body. 3- Smooth Muscle cells Smooth muscle cells are spindle-shaped and contain a single central nucleus. They range from 10 to 600 μm (micrometers) in length, and are the smallest type of muscle cell. They are elastic and therefore important in the expansion of organs such as the kidneys, lungs, and vagina. The myofibrils of smooth muscle cells are not aligned like in cardiac and skeletal muscle meaning that they are not striated, hence, the name smooth.Smooth muscle cells are arranged together in sheets and this organization means that they can contract simultaneously. They have poorly developed sarcoplasmic reticulums and do not contain T-tubules, due to the restricted size of the cells. However, they do contain other normal cell organelles such as sarcosomes but in lower numbers. Smooth muscle cells are responsible for involuntary contractions and are found in the walls of blood vessels and hollow organs such as the gastrointestinal tract, uterus , and bladder. They are also present in the eye and contract changing the shape of the lens causing the eye to focus. Smooth muscle is also responsible for waves of contraction throughout the digestive system, forcing food to move through the body (peristalsis).As with cardiac and skeletal muscle cells, smooth muscle cells contract as a result of depolarization of the sarcolemma. In smooth muscle cells this is facilitated by gap junctions. Gap junctions are tunnels which allow impulses to be transmitted between them, so that depolarization can spread, causing the myocytes to contract together in unison. Figure - Types of Muscle cells