WEEK-3-CELLS-AND-TISSUES_081736.pdf

Cells and Tissues The Cell  A cell is the basic structural and functional unit of living organisms. So, when you define cell properties, you are in fact defining the properties of life. The activity of an organism depends on the...

Cells and Tissues The Cell  A cell is the basic structural and functional unit of living organisms. So, when you define cell properties, you are in fact defining the properties of life. The activity of an organism depends on the collective activities of its cells. Cell Theory According to the principle of complementarity, the activities of cells are dictated by their structure (anatomy), which determines function (physiology). Continuity of life has a cellular basis. The Cell I. Nucleus  Nuclear Envelope/ Nuclear Membrane- Double membrane barrier. Parts of the Nucleoplasm- jelly like fluid of the Nucleus nucleus in which nuclear elements are suspended. Nucleolus- site where ribosomes are assembled. Chromatin- scattered throughout the nucleus (when cell is not dividing). Chromosomes- dense rodlike bodies (when cell is dividing). II. Plasma Membrane III. Cytoplasm  Cytosol- semitransparent fluid that suspends the other elements. 3 Major Components of Inclusions- stored nutrients or cell products floating in the cytosol. the Cytoplasm - also known as Cellular Pantry Organelles- “little organs” are specialized cellular compartments that are metabolic machinery of the cell. Organelles  All cells exhibit irritability (the ability to respond to Cell Physiology stimuli), digest foods, excrete wastes, and are able to reproduce, grow, move, and metabolize.  Cell Physiology: Membrane Transport A.) Passive processes: Diffusion and Filtration Diffusion is the movement of a substance from an area of its higher concentration to an area of its lower concentration. It occurs because of kinetic energy of the molecules themselves; no ATP is required. The diffusion of dissolved solutes through the plasma membrane is simple diffusion. The diffusion of water across the plasma membrane is osmosis. Diffusion that requires a protein channel or carrier is facilitated diffusion. Filtration is the movement of substances through a membrane from an area of high hydrostatic pressure to an area of lower fluid pressure. In the body, the driving force of filtration is blood pressure. B.) Active processes (active transport and vesicular transport) use energy (ATP) provided by the cell. In active transport, substances are moved across the membrane against an electrical or a concentration gradient by proteins called solute pumps. This accounts for the transport of amino acids, some sugars, and most ions. The two types of ATP-activated vesicular transport are exocytosis and endocytosis. Exocytosis moves secretions and other substances out of cells; a membrane-bounded vesicle fuses with the plasma membrane, ruptures, and ejects its contents to the cell exterior. Endocytosis, in which particles are taken up by enclosure in a plasma membrane sac, includes phagocytosis (uptake of solid particles), pinocytosis (uptake of fluids), and the highly selective receptor- mediated endocytosis. In the latter, membrane receptors bind with and internalize only selected target molecules.  Interphase- the longer phase of the cell cycle; metabolic phase. Cell Cell Division: Mitosis and Cytokinesis Division Mitosis- the process of dividing a nucleus into two daughter nuclei with exactly the same genes as the “mother” nucleus. Cytokinesis- division of the cytoplasm, which begins when mitosis is nearly completed. Mitosis: Prophase Chromatin fibers become coiled into chromosomes, with each chromosome having two chromatids joined at a centromere The centrioles separate from each other and begin to move toward opposite sides of the cell, directing the assembly of a mitotic spindle (composed of microtubules) between them as they move. By the end of prophase, the nuclear envelope and the nucleoli have broken down and temporarily disappeared, and the chromosomes have attached randomly to the spindle fibers by their centromeres. Mitosis: Metaphase Metaphase: the chromosomes line up at the metaphase plate. Mitosis: Anaphase Anaphase: The chromatids (now called chromosomes again) begin to move slowly apart, drawn toward opposite ends of the cell. This careful division of sister chromatids ensures that each daughter cell gets one copy of every chromosome. Mitosis: Telophase and Cytokinesis The chromosomes at opposite ends of the cell uncoil to become threadlike chromatin again. The spindle breaks down and disappears, a nuclear envelope forms around each chromatin mass, and nucleoli appear in each of the daughter nuclei. Formation of cleavage furrow over the midline of the spindle Cytokinesis usually begins during late anaphase and completes during telophase. Body Tissues  Epithelial Tissue Four Primary Connective Tissue Tissue Types Nervous Tissue Muscle Tissue  Epithelial Tissue Covering and lining epithelium covers all free body surfaces, both inside and out, and contains versatile cells. Functions of Epithelial Tissue ✓-Protection ✓-Absorption ✓-Filtration ✓-Secretion Characteristics of Epithelial Tissue Epithelial cells fit closely together to form continuous sheets with the help of cell junctions. The membranes always have one free (unattached) surface or edge, the Apical Surface. Basal Surface rests on a Basement Membrane. Epithelial tissues have no blood supply of their own. Epithelial cells regenerate themselves easily. Classification of Epithelia Based on number of cell layers -Simple Epithelium -Stratified Epithelium Based on cell shape -Squamous Cells -Cuboidal Cells -Columnar Cells Types of Epithelial Tissue  Connective Tissue It is the most abundant and widely distributed of the tissue types. Functions of Connective Tissue - Protection - Supporting - Binding together other body tissues. Characteristics of Connective Tissue Variation in blood supply Extracellular Matrix - produced by the connective tissue cells and then secreted to their exterior. - 2 main elements: ground substance fibers Types of Connective Tissue Bone Cartilage Dense Connective Tissue Loose Connective Tissue -Areolar Connective Tissue -Adipose Connective Tissue -Reticular Connective Tissue Blood  Bone Osseous Tissue Composed of osteocytes sitting in cavities called lacunae. These pits are surrounded by layers of a very hard matrix that contains calcium salts in addition to large numbers of collagen fibers Has an exceptional ability to protect and support other body organs  Cartilage Less hard and more flexible than bone Its major cell type is chondrocytes Types of Cartilage Hyaline cartilage- has abundant collagen fibers hidden by a rubbery matrix with a glassy, blue-white appearance. Fibrocartilage- Highly compressible; collagen fibers are in thick bundles, tightly packed, and run in parallel. Elastic cartilage- Shares many similarities with hyaline cartilage; Matrix is very light staining; Elastic fibers create a dark-staining network around the lacunae  Dense Connective Tissue Dense Fibrous Tissue Collagen fibers are the main matrix element Crowded between the collagen fibers are rows of fibroblasts that manufacture the building blocks of the fibers. Forms strong, ropelike structures such as Tendons and Ligaments. Tendons- attach skeletal muscles to bones Ligaments- connect bones to bones at joints  Loose Connective Tissue Softer and have more cells and fewer fibers than any other connective tissue type except blood. 3 MAIN TYPES: - Areolar Connective Tissue - Adipose Connective Tissue - Reticular Connective Tissue Areolar Connective Tissue most widely distributed connective tissue variety in the body a soft, pliable, “cobwebby” tissue that cushions and protects the body organs it wraps. Adipose Connective Tissue Fat It is an areolar tissue in which adipose (fat) cells predominate. A glistening droplet of oil occupies most of a fat cell’s volume and compresses the nucleus, displacing it to one side. Insulates the body and protects it from bumps and extremes of both heat and cold.  Blood Vascular Tissue It is considered a connective tissue because it consists of blood cells surrounded by a nonliving, fluid matrix called blood plasma. The “fibers” of blood are soluble proteins that become visible only during blood clotting. Transport vehicle for the cardiovascular system, carrying nutrients, wastes, respiratory gases, etc.  Muscle Tissue Highly specialized to contract, or shorten, which generates the force required to produce movement. 3 Types of Muscle Tissue - Skeletal Muscle Tissue - Cardiac Muscle Tissue - Smooth Muscle Tissue Skeletal Muscle Attached to Skeleton Can be controlled voluntarily The cells of skeletal muscle are long, cylindrical, and multinucleate, and they have obvious striations. Cardiac Muscle is found only in the heart wall As it contracts, the heart acts as a pump to propel blood through the blood vessels. Involuntary control Has striations, but cardiac cells have only a single nucleus and are relatively short, branching cells that fit tightly together (like clasped fingers) at junctions called intercalated discs. Smooth Muscle found in the walls of hollow organs such as the stomach, uterus, and blood vessels. As smooth muscle in its walls contracts, the cavity of an organ alternately becomes smaller or enlarges so that substances are mixed and/or propelled through the organ along a specific pathway. Nervous Tissue For internal communication and control. irritability and conductivity are their two major functional characteristics Neurons and supporting cells form the brain, spinal cord, and nerves  Tissue Injury Inflammation Granulation tissue forms Tissue repair: Regeneration and Fibrosis - Regeneration- replacement of destroyed tissue by the same kind of cells. - Fibrosis- involves repair by dense (fibrous) connective tissue, by the formation of scar tissue.