Kharkov National Medical University Department of Histology, cytology and embryology GENERAL HISTOLOGY Study of Tissues Epithelia and Glands MUSCLE The Tissue is The group of similar cells having: common embryonic origin common function common structure 3 4 Basic Tissues 4 Epithelial Tissue covers surfaces, lines hollow organs, forms glands Connective Tissue supports and feeds structures provides immunity to disease Muscle Tissue produces movement Nerve Tissue conducts nerve impulses 4 Epithelial Tissue FITURES: Closely packed cells that form sheets (of single or multiple layers) which are attached to a basement membrane Polarity. Epithelial cells have an apical (free) surface, which is exposed to body cavity, or exterior of body, and a basal surface Cell junctions are plentiful Epithelia are avascular, blood vessels are located in the underlying connective tissue Epithelia have a high capacity for renewal (high mitotic rate) Embryonic origin : 7 Germ layers of the embryo endoderm mesoderm ectoderm Epithelial functions: protection secretion digestion absorption excretion transportation sensory reception Epithelial Tissues and Their Basement Membrane The Polarity of Epithelial Cells Cells are connected with each other with junctions: Tight junctions Desmosomes Hemidesmosomes Gap junctions Intercellular junctions CLASSIFICATION OF E. Cell layers Simple epithelia Single cell layer Stratified epithelia Two or more cell layers Simple Squamous E. Single layer of flat cells lines blood vessels (endothelium), closed body cavities (mesothelium) very thin --- controls diffusion, osmosis Simple Cuboidal E. Single layer of cube-shaped cells. - Kidneys, glands Simple Columnar E. Goblet cells secrete mucus lubricate GI, reproductive and urinary systems Microvilli = fingerlike projections of cell membrane Absorption Pseudostratified Columnar E. Single cell layer All cells attach to basement membrane but not all reach free surface Nuclei at varying depths - Respiratory system Stratified Squamous E. Several cell layers thick Surface cells flat Keratinized = surface cells dead and filled with keratin Skin Nonkeratinized = all cells are living Cornea, oral 19 Example of Stratified Squamous Section of vagina Stratified Cuboidal E. Surface cells cuboidal Only in sweat gland ducts & male urethra Stratified Columnar E. Surface cells columnar Rare (very large ducts & part of male urethra) Multilayered Surface cells varying in shape from round to flat if stretched - urinary tract Transitional E. GLANDULAR E. A gland consists of one or more cells that produce and secrete a product (secretion) There are two types depending on how the cells release the substances they produce: Exocrine glands and endocrine glands Endocrine glands called “ductless glands” discharge their secretions into the blood. These secretions are hormones, which regulate some body functions. (study later) Exocrine glands secrete into ducts. Their secretions include mucus, sweat, oil, ear wax and digestive enzymes. Unicellular Gland: Goblet cell Goblet Shaped In epithelia of intestinal and respiratory tracts Produce mucin Protects and lubricates Exocrine glands Exocrine glands Multicellular Glands Two parts: Excretory duct (branched - compound, unbranched – simple) Secretory unit (secretory portion, end piece) (branched, unbranched); (tubular, alveolar (acinar) A Structural Classification of Exocrine Glands Mechanisms of Glandular Secretion Shina ALagia 2005 34 II. Muscle tissue Cells that shorten Provide us with motion, posture and heat Types of muscle skeletal muscle striated cardiac muscle smooth muscle Why do MUSCLES contract? Muscle cells have contractile proteins - actin and myosin, and some another … 36 Smooth Muscle Spindle shaped cells with a single central nuclei Walls of hollow organs (blood vessels, GI tract, bladder) Involuntary and nonstriated Contraction Can remain in a state of contraction for long periods. Contraction is usually slow. Origin Smooth muscle cells arise from mesenchyme. Regeneration Very good regenerates. 39 Skeletal Muscle Cells are long cylinders (fiber – symplastum) with many peripheral nuclei Visible light and dark banding (striated) Voluntary control SKELETAL MUSCLE Cross and Longitudinal Why do MUSCLES contract? Actin and myosin form special organelles – myofibrils, responsible for muscle contraction MF has "bands“ : I-band - actin filaments, A-band - myosin filaments which overlap with actin filaments, MF consists of units – sarcomeres Each sarcomere shotens – the fiber contracts 42 Mechanism of contraction Sliding filaments model From Z to Z is sarcomere Types of fibers: red and white Red contain large amounts of myoglobin and mitochondria. Contraction is slow. Back muscles, posture. Resistant to fatigue. White contain less myoglobin. ATPase activity is high, contraction is fast. Muscles of our fingers. Origin of skeletal muscle Originate from the paraxial mesoderm - myotome. Regeneration by Satellite cells Satellite cells are small cells are closely apposed to muscle fibers within the basal lamina which surrounds the muscle fiber. Cardiac Muscle Cells are branched cylinders with one central nuclei Involuntary and striated Communicate with each other by intercalated discs and anastomoses Cardiac muscle cells: 3 types: Contractile, Conducting Secretory Excitation in cardiac muscle is provided by: Conducting myocytes Or Purkinje fibres contain fewer myofibrils than contractile. Purkinje fibres CARDIAC MUSCLE Regeneration – intracellular Or By connective tissue replacement Comparison of 3 types skeletal muscle cardiac muscle smooth muscle Shape long cylindrical short cylindrical spindle Nucleus many one(maybe2) one at periphery at center at center Cross-striation obvious dim none Special structure triad intercalated disk dense pact, body Nerve system cerebrospinal cerebrospinal autonomic autonomic The End image2.png image3.jpeg image4.jpeg image5.jpeg image6.jpeg image7.jpeg image8.jpeg image9.jpeg image10.jpeg image11.jpeg image12.jpeg image13.jpeg image14.jpeg image15.jpeg image16.jpeg image17.jpeg image18.jpeg image19.jpeg image20.jpeg image21.jpeg image22.jpeg image23.jpeg image24.jpeg image25.jpeg image26.jpeg image27.jpeg image28.jpeg image29.png image30.gif image31.jpeg image32.png image33.jpeg image34.jpeg image35.jpeg