CELL AND TISSUE STRUCTURE AND ORGANIZATION
- 1. CELLAND TISSUE STRUCTURE AND ORGANIZATION Niyati Arun Keni B Optometry (M Optometry)
- 4. Structural features of cell
- 5. Structure • Plasma Membrane : Divides two major fluid compartments ICF and ECF. Plays role in cellular communication.
- 6. • Cytoplasm: cellular material between the plasma membrane and the nucleus. It is the site of most cellular activities. Mitochondria : Rod like double membrane structure, inner membrane folded into projections called Cristae. Site of ATP synthesis(powerhouse of cell). Ribosomes : Dense particles consisting of two subunits, each composed of ribosomal RNA and proteins. Free or attached to rough ER. Site of protein synthesis.
- 7. Rough Endoplasmic Reticulum: Membranous system enclosing a cavity, the cistern, and coiling through the cytoplasm. Externally studded with ribosomes. External face synthesizes phospholipids. Smooth Endoplasmic reticulum : Membranous system of sacs and tubules ; free of ribosomes. Site of lipid and steroid (cholesterol) synthesis, lipid metabolism and drug detoxification.
- 8. Golgi apparatus: A stack of flattened membranes and associated vesicles close to the nucleus. Packages, modifies and segregates proteins for secretion from the cell, inclusion in lysosomes and incorporation into the plasma membrane. Lysosomes: Membranous sacs containing acid hydrolases. Sites of intracellular digestion.
- 9. Peroxisomes: Membranous sacs of catalase and oxidase enzymes. The enzymes detoxify a number of toxic substances. The most important enzyme, catalase, breaks down hydrogen peroxide. Microtubules: Cylindrical structures made of tubulin proteins. Support the cell and give it shape. Involved in intracellular and cellular movements. Form centrioles and cilia and flagella
- 10. Centrioles: Paired cylindrical bodies each composed of nine triplets of microtubules. Organize a microtubule network during mitosis (cell division) to form the spindle and asters. Form the bases of cilia and flagella.
- 11. Cellular Extensions The major cellular extensions are 1. Cilia 2. Flagellum 3. Microvilli
- 12. 1. Cilia : Short cell-surface projections; each cilium composed of nine pairs of microtubules surrounding a central pair. Coordinated movement creates a unidirectional current that propels substances across cell surfaces. 2. Flagellum: Like a cilium, but longer; only example in humans is the sperm tail. 3. Microvilli: Tubular extensions of the plasma membrane; contain a bundle of actin filaments. Increase surface area for absorption.
- 13. • Nucleus The nucleus is a spherical or oval-shaped structure that usually is the most prominent feature of a cell. Surrounded by the nuclear envelope; contains fluid nucleoplasm, nucleoli, and chromatin. Control center of the cell; responsible for transmitting genetic information and providing the instructions for protein synthesis. Structure of nucleus 1. The nuclear envelope 2. Nucleoplasm 3. Chromatin 4. The nucleolus
- 15. 1. Nuclear envelope: is a double-layered membrane perforated with pores, which control the flow of material going in and out of the nucleus. The outer layer is connected to the endoplasmic reticulum, communicating with the cytoplasm of the cell. The exchange of the large molecules (protein and RNA) between the nucleus and cytoplasm happens here. 2. Nucleoplasm : A jelly like (made mostly of water) matrix within the nucleus. All the other materials “float” inside. Helps the nucleus keep its shape and serves as the median for the transportation of important molecules within the nucleus
- 16. 3. Chromatin: Appears as a fine, unevenly stained network, but special techniques reveal it as a system of bumpy threads weaving through the nucleoplasm. – Chromatin is composed of approximately – 30% DNA, our genetic material – 60% globular histone proteins which package and regulate the DNA – 10% RNA chains, newly formed or forming 4. Chromosomes: Contains DNA in a condensed form attached to a histone protein. Chromatin is comprised of DNA.
- 17. Functions • The nucleus is often compared to the “command center,” as it controls all functions of the cell. • It is important in regulating the actions of the cells. • It plays an important part in creating the cell’s proteins. • It is involved in important processes dealing with DNA and other genetic molecules.
- 18. • Largest cell of the body ?
- 19. Cell Junctions • Contact points between the plasma membranes of tissue cells • 5 most common types: 1. Tight junctions - tightly stitched seams between cells. 2. Adherens junctions - consist of the transmembrane protein. 3. Desmosomes - protein attachments between adjacent cells. 4. 4. Hemidesmosomes - found in basal epithelial cells, connecting them to their underlying basement membrane. 5. 5. Gap junctions - narrow tunnels that directly connect the cytoplasm of two neighbouring cells, consisting of proteins called connexons.
- 20. General principles of cell physiology 1. Cell division and growth. Cells need to grow and divide over time. Mitosis and meiosis are the two most common types of cell division. Mitosis produces two identical daughter cells, while meiosis makes four different daughter cells with half the DNA. 2. Cellular metabolism. All living things need energy or fuel to live, and metabolism helps them accomplish this. Most cells use either cellular respiration, which are a series of chemical processes. 3. Cellular communication. Living cells often need to communicate and spread information throughout an organism. They can use receptors or ligands, gap junctions or plasmodesmata to communicate. 4. Cellular transport. Cell transport moves materials across a cell membrane. This can be active or passive transport. 5. Cellular motility. Motility allows cells to move from one location to another. They may swim, crawl, glide or use other methods.
- 21. Tissue Organization It is a collection of cells which have similar structure. Function together to carry out specialized activities. • Tissue develop from three primary germs layers: Ectoderm, Mesoderm and Endoderm • Histology Branch of science that deals with the study of tissues.
- 22. Types of Tissues Tissues Epithelial Body surfaces, hollow organs, body cavities, duct and forms glands Connective Protects, supports and binds organs. Stores energy as fat, provides energy Muscular Generates the physical force needed to make body structures to move and generate body heat Nervous Detect changes in body and responds by generating nerve impulses
- 23. Epithelial Tissue • Cells are closely packed without any intercellular spaces • It refers to the sheets of cells that cover exterior surfaces of the body, line internal body cavities, and form the lining of internal and many external surfaces of organs and forms certain glands.
- 24. Functions 1. Role of defense and protect body organs. 2. Secret gastric juice in stomach. 3. Absorb digested food in intestine. 4. Removes waste as sweat in skin.
- 26. Simple Epithelial Tissue • It consist of a singe layer of identical cells. • Found on absorptive or secretary surfaces. • Divided into 3 main types: 1. Simple squamous epithelium 2. Simple Cuboidal epithelium 3. Simple Columnar epithelium
- 28. Stratified Epithelial Tissue • Consists of several layers of cells of various shapes. • Continual cell division in the lower layers pushes the cell above the nearer and nearer to the surface where they are shed. • Basement membrane is usually absent. • Main function is to protect the underlying structure from mechanical wear and tear.
- 29. • Keratinized squamous epithelium - It is the type of striated squamous epithelium in which the cells have a tough layer of keratin in the apical segment of cells and several layers deep to it. - Keratin is a tough, fibrous intracellular protein that helps protect skin and underlying tissues from heat, microbes, and chemicals. Sites : Skin, Hairs and Nails. Function: Provides protection against dehydration and other mechanical stress.
- 30. • Non-keratinized stratified squamous epithelium - Non-keratinized stratified squamous epithelium is the epithelium in which the cells do not have a lot of keratin deposits within them, but rather are moisturized by mucus from the salivary or the mucus glands. Sites: Lining of the mouth, Vagina, conjunctiva of eye. Function: Produce some amount of mucus to keep the surface moist.
- 32. • Transitional Epithelium - It is composed of several layers of pear shaped cells which are very elastic and have the capacity of dividing themselves. Sites: Lines several parts of the urinary tract including the bladder. Function: 1. Enabling tissues to contract and expand. 2. Serving as an effective permeability barrier, especially in the urinary system. 3. Stretching significantly to accommodate changes in organ volume. 4. Acting as a barrier between the lumen and the bloodstream.
- 33. Connective Tissue • It binds the cells and organs of the body together and functions in the protection, support, and integration of all parts of the body. • Some examples include fat, bones, and tendons. • 3 types 1. Connective tissue proper 2. Fluid connective tissue 3. Supporting connective tissue
- 34. Connective Tissue proper cells • Fibroblasts: most abundant type; produce fibers and ground substance. -Function=> Active in tissue repair • Macrophages: these cells “eat” or phagocytize damaged cells or pathogens. Release chemicals that mobilize the immune system. • Fat cells or adipocytes: contain large droplets of lipids (fat) • Mast Cells: found near blood vessels; have vesicles filled with chemicals released to defend the body after injury/infection.
- 35. Fibers of Connective Tissue • Collagen fibers: Most common type; long, straight, unbranched- Strong and flexible. • Elastic fibers: contain protein Elastin. They are branched, wavy and stretchy. • Reticular fibers: least common type; thin, branched and interwoven like a web.
- 36. Connective Tissue Proper Types Loose Connective Tissue or Areolar tissue “packing material of the body” Fill spaces between organs, provide cushioning, and support epithelia, anchor blood vessels and nerves, store lipids. Dense Connective Tissue Fibrous(Tendons, ligaments and fasciae) and Elastic(Large blood vessel walls, the trachea and bronchi and the lung)
- 37. Fluid Connective Tissue Types Blood Lymph • It contain cells in a watery matrix. • Unlike other connective tissues, the proteins are dissolved in the matrix and do not form insoluble fibers. 1. Blood- A fluid Connective Tissue: Consists of- Red blood cells: transport Oxygen(O2) White blood cells: fight infection Platelets: clot blood 2. Lymph- A fluid Connective Tissue: It forms as interstitial fluid ( fluid within the body’s tissue) enters small passageways , or Lymphatic vessels that eventually return it to the cardiovascular system.
- 38. Supporting Connective Tissue • It includes : 1. Cartilage – Cells are sparse and lie embedded in matrix reinforced by collagen and elastic fibers. 3 major types: Hyaline, Elastic-fibro, Fibrous A. Hyaline Cartilage: It is a smooth bluish white tissues. The chondrocytes are arranged in small groups within cell nests and matrix is solid and smooth. Functions- Provides flexibility, support and smooth surfaces for movements at joints. Sites- End of long bones, forming the parts of larynx, trachea and bronchi.
- 39. B. Elastic : Contains large amount of elastin fibers in the chondrin. It’s highly flexible. Site- The pinna of lobe of the ear, epiglottis
- 40. C. FibroCartilage : It consists of white collagen fibres in a matrix similar to that of hyaline cartilage with the cells widely dispersed. It is a tough, slightly flexible, supporting tissue. Site- Pads between intervertebral disc and between pubic bones
- 41. 2. Bone (Osseus tissue) - Matrix consists of little ground substance containing collagen fibers . It is calcified with calcium compounds. Strong and resistant to shattering. Contain osteocytes( bone cells) found in lacunae. Lacunae are found surrounding blood vessels . Cytoplasmic extensions from osteocytes reach blood vessels- form a network called the canaliculi. Types: A. Spongy Bone- spongy or fine honey comb like appearance B. Compact bone- solid of dense appearance
- 43. Muscular Tissue • It is made up of muscle cells (Muscle fibers) which unite to form muscle. • It contracts and relaxes rhythmically. Types Skeletal Muscle Tissue Cardiac Muscle Tissue Smooth Muscle Tissue
- 45. Skeletal Muscle Tissue • Skeletal muscle tissue is composed of long cells called muscle fibers that have a striated appearance. • Muscle fibers are organized into bundles supplied by blood vessels and innervated by motor neurons. • Function: Skeletal muscles attach to and move bones by contracting and relaxing in response to voluntary messages from the nervous system.
- 47. Smooth Muscle Tissue • It is also described as non-straited or involuntary(not under conscious control). • It is found in the walls of hollow organs. • The arrangement of cells within smooth muscle tissue allows for contraction and relaxation with great elasticity. Functions : 1. The smooth muscle in the walls of organs like the urinary bladder and the uterus allow those organs to expand and relax as needed. 2. The smooth muscle of the alimentary canal (the digestive tract) facilitates the peristaltic waves that move swallowed food and nutrients. 3. In the eye smooth muscle changes the shape of the lens to bring objects into focus. 4. Artery walls include smooth muscle that relaxes and contracts to move blood through the body
- 49. Cardiac Muscle Tissue • The heart wall is composed of three layers. • The middle layer, the myocardium, is responsible for the heart’s pumping action. • Cardiac muscle, found only in the myocardium, contracts in response to signals from the cardiac conduction system to make the heart beat. • Cardiac muscle is made from cells called cardiocytes. Like skeletal muscle cells cardiocytes have a striated appearance, but their overall structure is shorter and thicker. • Function: Cardiocytes are branched, allowing them to connect with several other cardiocytes, forming a network that facilitates coordinated contraction.
- 51. Nervous Tissue • These types of tissues are found in nervous system. • Functions : 1. Irritability – The capacity to react to various physical and chemical agents. 2. Conductivity – The ability to transmit the resulting reaction from one point to another. Types Non excitable cells Neurons Excitable cells Neuroglia
- 53. Neuron • It is also known as Neurone or nerve cell is an electrically excitable cell that receives, processes and transmits information through electrical and chemical signals. • It is the working unit of nervous system. • It consist of cell body with cytoplasmic extensions- dendrites, axon and pole
- 55. Neuroglia • It forms the support structure of nervous tissues, insulating and protecting neurons. • They are astrocytes, oligodendrocytes, microglia and ependymal cells.
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