1. Nucleus
      2. Connective Tissue
      3. Smooth Muscle Cell

      • Smooth Muscle Tissue are non-striated, involuntary, single-nucleated, elongated spindle-shaped cells. These are supplied by autonomic nerves (sympathetic and parasympathetic) and are located in the walls of the gastrointestinal tract, blood vessels, respiratory tract, urinary tract, arrector pili muscle. Its main function is contraction. They are typically shorter than skeletal muscle cells. The nucleus is centrally positioned, and the sarcoplasm is composed of fibrils. Thick (myosin) and thin (actin) filaments are dispersed throughout the sarcoplasm and connected to adhesion densities on the cell membrane and focal densities within the cytoplasm. Since the contractile proteins of these cells are not organized into myofibrils like those of skeletal and cardiac muscle, they have a smooth appearance as opposed to a striated one.

        In the illustration, the longitudinal section of smooth muscle displays long fusiform smooth muscle cells with centrally located, elongated nuclei. Since the muscle fibers are arranged in staggered arrays, they can be packed very closely, with only a limited amount of intervening connective tissue. Each smooth muscle cell is sur rounded by a basal lamina and reticular fibers, neither of which is evident in this figure. Capillaries are housed in the connective tissue separating bundles of smooth muscle fibers.

        1. Intercalated Discs
        2. Branching Fiber
        3. Cardiac Myocyte
        4. Centrally placed oval nuclei of cardiac myocyte
        5. Fibroblasts
          • Cardiac Muscle Tissue shares important characteristics with both skeletal and smooth muscle. Functionally, cardiac muscle produces strong contractions like skeletal muscle. However, it has inherent mechanisms to initiate continuous contraction like smooth muscle. The rate and force of contraction is not subject to voluntary control, but is influenced by the autonomic nervous system and hormones.
            Histologically, cardiac muscle appears striated like the skeletal muscle due to arrangement of contractile proteins. It also has several unique structural characteristics:

            • The fibers of cardiac muscle are not arranged in a simple parallel fashion. Instead, they branch at the ends to form connections with multiple adjacent cells, resulting in a complex, three-dimensional network.
            • Cardiac muscle fibers are long cylindrical cells with one or two nuclei. The nuclei are centrally situated like that of smooth muscle.
            • Cardiac muscle sarcoplasm has a great number of mitochondria to meet the energy demands.
            • Similar to the skeletal muscle, cardiac muscle cells have an invaginating network

            1. Myofibrils
            2. Nucleus
            3. Z disc
            4. Sarcomere
            5. H zone
            6. Connective Tissue
            7. A band
            8. I band
              • Skeletal muscle is mainly responsible for the movement of the skeleton, but is also found in organs such as the globe of the eye and the tongue. It is a voluntary muscle, and therefore under conscious control. Similar components and structures are present in skeletal muscle cells, although these components and structures are described using different terminology. The sarcolemma is the plasma membrane of skeletal muscle; sarcoplasm is its cytoplasm; and the sarcoplasmic reticulum is its endoplasmic reticulum.

                Each muscle cell is defined by a sarcolemma and contains many nuclei along its length. The nuclei are displaced peripherally within a cross section of the sarcoplasm while a large number of longitudinal myofibrils, groups of arranged contractile proteins, occupy most of the center space. The myofibril contains several important histological landmarks:

                • The myofibril is composed of alternating bands. The I-bands (isotropic in polarized light) appear light in color and the A-bands (anisotropic in polarized light) appear dark in color. The alternating pattern of these bands results in the striated appearance of skeletal muscle.
                • The Z-lines (Zwischenschieben) bisect the I-bands.
                • A light band called the H-band (Heller) sits within each A-band.
                • The M-line (Mittelschiebe) bisects each A-band (and, in doing so, bisects each H-band).

                1. Dendrites
                2. Cell Body
                3. Glial cells
                4. Axon
                  • Multipolar neurons are the most common type of neuron. They are located in the central nervous system (brain and spinal cord) and in autonomic ganglia. Multipolar neurons have more than two processes emanating from the neuron cell body and possesses a single axon and many dendrites allowing for the integration of immense information from other neurons.
                  • HYALINE CARTILAGE
                    1. Isogenous groups of chondrocytes
                    2. Chondrocyte
                    3. Interterritorial (Matrix)
                    4. Territorial (Matrix)
                    5. Capsular (Matrix)
                    6. Lacuna
                      • Histologically, hyaline cartilage has glass-like (transparent) matrix. Hence, it is called hyaline cartilage. It is the most abundant type of cartilage in the human body and is present at the following locations: Fetal skeleton, articular cartilages, nose cartilage, costal cartilages, laryngeal cartilages (thyroid, cricoid and arytenoids cartilages), trachea and bronchi, and developing bone (epiphyses). Moreover, it consists of cells (chondrocytes), ground substance, and fibers. Its functions include: maintaining patency of trachea and the main bronchi because of the firmness and providing smooth surface for the movements (articular cartilages). In the illustration, its matrix shows spaces called lacunae and shows three zones namely: Capsular, Territorial, and Interterritorial matrix.
                        1. Collagen Fibers
                        2. Nuclei of fibroblast
                          • Dense collagenous connective tissue is what makes up tendons and ligaments and consist of a higher density of collagen fibers. Its characteristics include: the presence of collagen fibers, (or fiber bundles), arranged in orderly fashion parallel to each other, Nuclei of some cells (mainly fibroblasts) are seen between the bundles of collagen and are elongated (elliptical), and the ground substance is less in amount.
                          • ELASTIC CARTILAGE
                            1. Elastic Fibers
                            2. Matrix
                            3. Chondrocytes in lacunae
                              • Elastic Cartilage is a type of cartilage that gives resilience, pliability, and elasticity to the organ. Freshly dissected elastic cartilage is yellowish in color; hence, it is also called yellow elastic cartilage. This type of cartilage is present in the pinna of external ear, walls of external acoustic meatus, auditory tube, epiglottis, tips of arytenoids, corniculate, and cuneiform cartilages of larynx. Histologically, fibrocartilage shows rows of chondrocytes embedded in matrix bundles of thick collagen fibers.
                              • FIBROCARTILAGE
                                1. Row of chondrocytes embedded in small quantity of matrix
                                2. Bundles of collagen fibers
                                  • Fibrocartilage is a combination of dense regular connective tissue and hyaline cartilage. It contains bundles of thick collagen fibers that give white color to cartilage. Hence, this cartilage is also called white fibrocartilage. This type of cartilage can be found in Intervertebral discs, pubic symphysis, articular disc of sternoclavicular and temporomandibular joints, menisci, glenoidal labrum, acetabular labrum, articular disc of wrist joint, and at the site of tendon attachment with bones (few places). For its function, it helps in shock absorption and in withstanding compression and shearing forces. In addition, the fibrocartilage consists of dense regular connective tissue with interspaced rows of chondrocytes.
                                  • TRANSITIONAL EPITHELIUM
                                    1. Superficial umbrella-shaped cells
                                    2. Transitional Epithelium (several layers of round nuclei)
                                      • Transitional Epithelium lines the major part of urinary passage; hence, it is also called urothelium. This type of tissue changes shape in response to stretching (stretchable epithelium). The transitional epithelium usually appears cuboidal when relaxed and squamous when stretched. This type of tissue is located in the renal pelvis and calyces of kidney, ureter, urinary bladder, and part of urethra. In addition, its function includes the following: (1) It provides ability of distension to urinary bladder and (2) acts as a barrier because of presence of occluding junctions and intramembranous plaques.
                                      • AREOLAR CONNECTIVE TISSUE
                                        1. Collagen Fibers
                                        2. Elastic Fibers
                                        3. Fibroblast
                                        4. Lymphocyte
                                          • Areolar connective tissue is also called as loose connective tissue. It consists of fibers, cells (such as fibroblasts, macrophages, plasma cells, fat cells, white blood cells, and so on), and ground substance. This type of tissue is found beneath the dermis layer and is also underneath the epithelial tissue of all the body systems that have external openings. It is also a component of the lamina propria of the digestive and respiratory tracts, the mucous membranes of reproductive and urinary system, the stroma of glands, and the hypodermis of the skin. It is also found in the mesentery which is surrounding the intestine. For its function, it connects and surrounds different organs in the human body, provides nutrition to the cells, and acts as a cushion to protect the organs from various external forces.

                                        you're currently offline

                                        New Report