Cells and Tissues PDF

Cells and Tissues Dr. Jillian B. Danganan OBJECTIVES ´ Identify cell and tissue structure, types, and function ´ Describe the phases of cell cycle ´ Differentiate the processes of passive and active transport, pinocytosis, diffusion, phagocytosis and osmosis CELLS CELL ´ Smallest structural and...

Cells and Tissues Dr. Jillian B. Danganan OBJECTIVES ´ Identify cell and tissue structure, types, and function ´ Describe the phases of cell cycle ´ Differentiate the processes of passive and active transport, pinocytosis, diffusion, phagocytosis and osmosis CELLS CELL ´ Smallest structural and functional unit of living organisms, which can exist on its own ´ CELL THEORY ´ Cells are the basic unit of life. ´ All living things are made of cells. ´ Cells come from other cells. PARTS OF CELL PARTS OF CELL: NUCLEUS NUCLEUS ´ Command center of the cell ´ Contains the molecular machinery to replicate the DNA and to synthesize and process all types of RNA ´ Nuclear envelope - outer membrane continuous with the endoplasmic reticulum ´ Nucleoli - specialized regions of chromatin ´ Chromatin - mass of DNA and its associated protein PARTS OF CELL: PLASMA MEMBRANE PLASMA MEMBRANE ´ or Cell membrane ´ Functions as a selective barrier regulating the passage of materials into and out of the cell and facilitating the transport of specific molecules  PARTS OF CELL: PLASMA MEMBRANE CELL MEMBRANE JUNCTIONS ´ TIGHT JUNCTIONS ´ Most apical of the junctions ´ Seals two adjacent cells; Barrier to movement of proteins across membranes ´ DESMOSOMES (Anchoring junction) ´ Spot-like structures between cells ´ For tight intercellular adhesion ´ GAP JUNCTIONS (Communicating junction) ´ Provides medium for communication between cells ´ Bridge for sharing of small molecules between cells; For rapid intercellular communication ´ Cardiac and unitary smooth muscle ´ Connexons – functional unit; hexagonal shaped structures responsible for intercellular communication PARTS OF CELL: CYTOPLASM CYTOPLASM ´ Cellular material outside the nucleus and inside the plasma membrane ´ Site of most cellular activities ´ Parts ´ Cytosol ´ Inclusions ´ Organelles PARTS OF CELL: CYTOPLASM CYTOSOL AND INCLUSIONS ´ Cytosol - Semitransparent fluid that suspends the other elements ´ Inclusions ´ Contain accumulated metabolites or other substances ´ Have little or no metabolic activity ´ Not enclosed by membrane PARTS OF CELL: ORGANELLES MITOCHONDRIA ´ Rodlike, double-membrane structures; inner membrane folded into projections called cristae. ´ Also known as the ‘powerhouse’ of the cell ´ Major site for ATP synthesis à ATP provides the energy for all cellular work RIBOSOMES ´ Dense particles consisting of two subunits, each composed of ribosomal RNA and protein ´ Engage in protein synthesis  PARTS OF CELL: ORGANELLES ENDOPLASMIC RETICULUM ´ site for synthesis of proteins and lipids. ´ ROUGH ENDOPLASMIC RETICULUM ´ Site for synthesis of most membrane-bound proteins for secretion, incorporation into the plasma membrane, and as enzymes within lysosomes ´ SMOOTH ENDOPLASMIC RETICULUM ´ Lack bound polyribosomes ´ Site of lipid (phospholipids and steroids) synthesis and carbohydrate metabolism  PARTS OF CELL: ORGANELLES GOLGI APPARATUS ´ Stack of flattened membranous sacs ´ Completes post translational modifications of proteins produced in the RER ´ Packages, modifies, and segregates proteins for secretion from the cell, inclusion in lysosomes, or incorporation into the plasma membrane  PARTS OF CELL: ORGANELLES LYSOSOME ´ Sites of intracellular digestion and turnover of cellular components ´ Membrane-limited vesicles that contains about 40 different hydrolytic enzymes and are particularly abundant in cells with phagocytic activity: Macrophages, Neutrophils PEROXISOMES ´ Spherical organelles enclosed by a single membrane and named for their enzymes producing and degrading hydrogen peroxide ´ Contain oxidase and catalase enzymes to detoxify a number of harmful or poisonous substances  PARTS OF CELL: ORGANELLES CYTOSKELETON ´ Determine the shapes of cells, play an important role in the movements of organelles and cytoplasmic vesicles, and also allow the movement of entire cells ´ Complex array of ´ Microfilaments ´ Intermediate filaments ´ Microtubules PARTS OF CELL: CELL EXTENSIONS CILIA ´ (+) microtubules ´ Long highly motile apical structures that are abundant on cuboidal or columnar cells of many epithelia FLAGELLA ´ Hairlike structure that acts primarily as an organelle of locomotion in the cells of many living organisms MICROVILLI ´ (+) actin filaments ´ Visible as brush (striated) borders in cells lining the small intestine ´ Increases cell surface area to facilitate absorption SPECIALIZED CELLS MEMBRANE TRANSPORT ´ Solution ´ Solute-Solvent ´ Intracellular fluid ´ Extracellular fluid ´ Interstitial fluid ´ Plasma volume ´ Selective permeability ´ Barrier allows some substances to pass through it while excluding others. ´ Allows nutrients to enter the cell but keeps many undesirable or unnecessary substances out. ´ Only for healthy, unharmed cells MEMBRANE TRANSPORT ´ Passive vs Active transport PASSIVE TRANSPORT: ´ Diffusion ´ Movement of solutes from high concentration to low concentration ´ May be simple or facilitated diffusion ´ Osmosis ´ Movement of water from low concentration to high concentration MEMBRANE TRANSPORT ´ Diffusion MEMBRANE TRANSPORT PASSIVE VS ACTIVE TRANSPORT ´ Active Transport ´ Movement of solutes from low concentration to high concentration ´ Moving uphill against the concentration gradient ´ Uses ATP ´ Na-K pump MEMBRANE TRANSPORT ´ Active Transport ´ Na-K pump MEMBRANE TRANSPORT VESICULAR TRANSPORT Exocytosis ´ Mechanism that cells use to actively secrete hormones, mucus, and other cell products or to eject certain cellular wastes Endocytosis ´ Includes those ATP-requiring processes that take up, or engulf, extracellular substances by enclosing them in a vesicle MEMBRANE TRANSPORT ´ Endocytosis CELL CYCLE ´ Interphase ´ Cell growth, DNA replication, preparing for cell division ´ Cell Division ´ Cell reproduces itself CELL CYCLE: INTERPHASE CELL CYCLE: MITOSIS Period of cell division Cell cycle phase that can be routinely distinguished with the light microscope Parent cell divides and each of the two daughter cells receives a chromosomal set identical to that of the parent cell Events of mitosis are subdivided into four major stages Prophase Metaphase Anaphase Telophase CELL CYCLE: MITOSIS Prophase Metaphase Anaphase Telophase CELL CYCLE: MITOSIS CENTRAL DOGMA BODY TISSUES BODY TISSUES ´ Groups of cells that are similar in structure and function ´ Human organs are composed of four basic tissue types: ´ Epithelial ´ Connective ´ Muscle ´ Nervous BODY TISSUES: EPITHELIAL TISSUE ´ Or epithelium ´ Lining, covering, and glandular tissue of the body ´ Epithelial functions ´ Protection - skin ´ Absorption – digestive system ´ Filtration – lining of respiratory tract ´ Secretion - glands  BODY TISSUES: EPITHELIAL TISSUE HALLMARKS OF EPITHELIUM ´ Epithelial cells fit closely together à continuous sheets (specialized cell junctions) ´ Membrane have apical surface (one free surface or edge) – exposed to the body’s exterior or to the cavity ´ One edge is anchored – basement membrane - material secreted by both the epithelial cells and the connective tissue cells deep to the epithelium ´ Epithelial are avascular – no blood supply ´ If well nourished, regenerate easily  BODY TISSUES: EPITHELIAL TISSUE CLASSIFICATION ´ Number of cell layers ´ Simple – one layer of cells ´ Stratified – more than one layer ´ Shape of the cells ´ Squamous - flattened ´ Cuboidal – cube-shaped ´ Columnar – column-shaped BODY TISSUES: EPITHELIAL TISSUE  BODY TISSUES: EPITHELIAL TISSUE SIMPLE SQUAMOUS ´ Single layer of flattened cells with flat nuclei ´ Distribution ´ Endothelium: lines luminal surface of heart and blood vessels ´ Mesothelium: lines serous cavities ´ Functions ´ Filtration or gas exchange ´ Absorption ´ Secretion of biologically active molecules  BODY TISSUES: EPITHELIAL TISSUE SIMPLE CUBOIDAL ´ Single layer of squared-shaped cells with spherical nuclei ´ Distribution ´ Epithelium of ovaries ´ Collecting tubules (kidneys) ´ Some ducts of salivary glands and pancreas ´ Functions ´ Covering ´ Secretion  BODY TISSUES: EPITHELIAL TISSUE SIMPLE COLUMNAR ´ Single layer of cells that are taller than wide with elongated nuclei ´ Often with specialized structures on apical surface (cilia, microvilli) ´ Distribution ´ Colon (with goblet cell) and small intestine (with microvilli and goblet cells) ´ Fallopian tubes (with surface cilia) ´ Respiratory tract (with pseudostratification) ´ Vas deferens ´ Gallbladder ´ Functions ´ Protection ´ Lubrication ´ Absorption ´ Secretion  BODY TISSUES: EPITHELIAL TISSUE STRATIFIED SQUAMOUS ´ Two or more layers of flattened cells ´ Most common stratified epithelium in the body ´ Distribution ´ Surface of the skin, mouth, esophagus (abuse/friction) ´ Keratinized stratified squamous (dry) ´ No nucleus and metabolically inactive ´ With keratin filaments ´ Seen in epidermis ´ Prevents water loss, protection ´ Nonkeratinized stratified squamous (moist) ´ Surface cell with nucleus and metabolically active ´ In moist internal cavities (i.e. outer covering of cornea, mouth, esophagus, larynx, vagina) ´ Protection, secretion, prevention of water loss  BODY TISSUES: EPITHELIAL TISSUE STRATIFIED CUBOIDAL ´ Two or more layers with the surface cells being cuboidal in shape ´ Relatively rare histologic types of epithelia ´ Distribution ´ Lines the excretory ducts of salivary and sweat glands and ovarian follicles ´ Function ´ Protection and secretion  BODY TISSUES: EPITHELIAL TISSUE STRATIFIED COLUMNAR ´ Two or more layers with the surface cells being columnar cells, but its basal cells vary in size and shape ´ Relatively rare histologic types of epithelia ´ Distribution ´ Lines the conjunctivae ´ Male urethra, anus, pharynx ´ Function ´ Protection and secretion  BODY TISSUES: EPITHELIAL TISSUE PSEUDOSTRATIFIED COLUMNAR EPITHELIUM ´ Irregular cells that are all attached to the basement membrane but give a stratified appearance because their nuclei are at different levels and not all reach free surface ´ Distribution ´ Respiratory tract (e.g. trachea, bronchi, nasal cavities) ´ Function ´ Heavily ciliated to transport mucus-trapped particles  BODY TISSUES: EPITHELIAL TISSUE TRANSITIONAL ´ Highly modified, stratified with round dome-shaped superficial cells called umbrella cells – vary in appearance ´ Surface rounded cells flatten and elongate when the bladder fills with urine. ´ Distribution ´ Urinary tract, from kidneys to the proximal part of the urethra ´ Function ´ Specialized for distensibility  BODY TISSUES: EPITHELIAL TISSUE GLANDULAR EPITHELIUM ´ Specialized form of epithelia otherwise known as “glands” ´ One or more cells that make and secrete a particular product ´ Function and Distribution ´ Synthesis, storage, and release of substances ´ Lipids (adrenal glands, sebaceous glands) ´ Proteins (pancreas, mammary glands) ´ Complexes of carbohydrate-protein (salivary glands) ´ Sweat glands ´ Can be divided: Exocrine and Endocrine glands  BODY TISSUES: EPITHELIAL TISSUE GLANDULAR EPITHELIUM ´ Endocrine glands ´ No ducts, ductless glands ´ Secretions diffuse directly into the blood vessels ´ Thyroid, adrenals, pituitary ´ Exocrine glands ´ Retain their ducts ´ Secretions exit through the ducts to the epithelial surface ´ Sweat glands, oil glands BODY TISSUES: EPITHELIAL TISSUE BODY TISSUES: EPITHELIAL TISSUE  BODY TISSUES: CONNECTIVE TISSUE CONNECTIVE TISSUE ´ Most abundant and widely distributed of the tissue types ´ Provides a matrix that supports and physically connects other tissues and cells to form the organs of the body ´ Interstitial fluid of CT gives metabolic support to cells as medium for diffusion of nutrients and waste products  BODY TISSUES: CONNECTIVE TISSUE HALLMARKS OF CONNECTIVE TISSUE ´ Variations in blood supply – well vascularized ´ EXCEPT tendons, ligaments and cartilage ´ Extracellular matrix ´ Nonliving substance outside the cell ´ Produced by the connective tissue cells and then secreted to their exterior ´ Composed of ground substance and fibers  BODY TISSUES: CONNECTIVE TISSUE EXTRACELLULAR MATRIX Ground substance ´ Water with complex mixture of three major kinds of macromolecules: ´ Glycosaminoglycans (GAGs) ´ Proteoglycans ´ Multiadhesive glycoproteins ´ Acts as both lubricant and a barrier Fibers ´ Fibrous components of CT are elongated structures formed from proteins that polymerize after secretion from fibroblasts ´ 3 main types of fibers: (“CoReLa”) ´ Collagen Fibers – high tensile strength; formed by proteins of the collagen family ´ Reticular Fibers – internal skeleton; formed by proteins of the collagen family ´ Elastic Fibers - ability to stretch and recoil; composed mainly of elastin protein  BODY TISSUES: CONNECTIVE TISSUE TYPES OF CONNECTIVE TISSUE ´ Loose connective tissue ´ Dense connective tissue ´ Bone ´ Cartilage ´ Blood  BODY TISSUES: CONNECTIVE TISSUE TYPES OF CONNECTIVE TISSUE ´ Broadly classified as “loose” or “dense” terms that refer to the amount of collagen present. ´ “loose” – less collagen ´ “dense” – more collagen ´ Loose connective tissue - softer and have more cells and fewer fibers ´ Dense connective tissue  BODY TISSUES: CONNECTIVE TISSUE LOOSE CONNECTIVE TISSUE ´ Areolar ´ Most widely distributed connective tissue variety in the body ´ Soft, pliable, “cobwebby” tissue that cushions and protects the body organs it wraps ´ Lamina propria - soft layer of areolar connective tissue which underlies all mucous membranes ´ Adipose ´ Reticular  BODY TISSUES: CONNECTIVE TISSUE LOOSE CONNECTIVE TISSUE ´ Areolar ´ Adipose ´ Connective tissue in which fat-storing cells or adipocytes predominate ´ Adipocyte - glistening droplet of oil occupies most of a fat cell’s volume and compresses the nucleus, displacing it to one side ´ Functions: ´ Storage depots for neutral fats, chiefly triglycerides ´ Protects some organs (i.e. kidneys, eyeballs) ´ Thermal insulator of body ´ Reticular  BODY TISSUES: CONNECTIVE TISSUE LOOSE CONNECTIVE TISSUE ´ Areolar ´ Adipose ´ Reticular ´ Delicate network of interwoven reticular fibers associated with reticular cells, which resemble fibroblasts ´ It forms the stroma or internal framework of an organ ´ Bone marrow, lymph node, spleen BODY TISSUES: CONNECTIVE TISSUE DENSE CONNECTIVE TISSUE ´ Collagen fibers are the main matrix element ´ The abundance of collagen protects organs and strengthens them structurally ´ Has similar components as loose connective tissue but with fewer cells ´ TYPES: ´ Dense irregular connective tissue ´ Bundles of collagen fibers appear randomly interwoven, with no definite orientation ´ Ex: Deep dermis layer of skin, capsules of most organs ´ Dense regular connective tissue ´ Consists mostly of type I collagen bundles and fibroblast aligned in parallel à for great resistance to prolonged/repeated stress from the same direction ´ Examples: ´ Tendons - cords connecting muscles to bones ´ Aponeuroses – sheet like tendons ´ Ligaments – connect bones to bones at joints  BODY TISSUES: CONNECTIVE TISSUE BONE ´ aka osseus tissue – composed of osteocytes (or bone cells) ´ Specialized connective tissue composed of extracellular bone matrix ´ Function: ´ Protects vital organs ´ Encloses internal cavities containing bone marrow where blood cells are produced ´ Reservoir of calcium, phosphate, and other ions ´ Participates in skeletal muscle contraction and bodily movements ´ Components ´ Osteocytes ´ Osteoblast ´ Osteoclasts ´ Haversian canal - or osteons – functional unit of bones BODY TISSUES: CONNECTIVE TISSUE CARTILAGE ´ Less hard and more flexible than bone ´ Tough, durable form of connective tissue ECM with high concentration of GAGs and proteoglycans, interacting with collagen and elastic fibers ´ Chondrocytes – cartilage cells ´ Synthesize and maintain all ECM components and are located in matrix cavities called lacunae ´ Function: ´ Provides cushioning and sliding regions, within skeletal joints ´ Guides development and growth of long bones, both before and after birth BODY TISSUES: CONNECTIVE TISSUE TYPES OF CARTILAGE ´ Hyaline Cartilage ´ Most common of the three types ´ Has abundant collagen fibers hidden by a rubbery matrix with a glassy, blue-white appearance ´ Location: ´ Articular surfaces of movable joints ´ Walls of larger respiratory passages (nose, larynx, trachea, bronchi) ´ Ventral ends of ribs, where they articulate with the sternum ´ Epiphyseal plates of long bones, where it makes possible longitudinal bone growth ´ Elastic Cartilage ´ Fibrocartilage BODY TISSUES: CONNECTIVE TISSUE TYPES OF CARTILAGE ´ Hyaline Cartilage ´ Elastic Cartilage ´ Essentially similar to hyaline cartilage except that it contains an abundant network of elastic fibers ´ More flexible than hyaline cartilage ´ Found in structures with elasticity ´ Elastic cartilage is found in the: ´ Auricle of the ear ´ Walls of the external auditory canals ´ Epiglottis ´ Auditory (Eustachian) tuibe ´ Upper respiratory tract ´ Fibrocartilage BODY TISSUES: CONNECTIVE TISSUE TYPES OF CARTILAGE ´ Hyaline Cartilage ´ Elastic Cartilage ´ Fibrocartilage ´ Essentially mixture of hyaline cartilage and dense connective tissue ´ It is found in: ´ Intervertebral discs ´ Attachments of certain ligaments ´ Pubic symphysis ´ Serves as very tough, yet cushioning support tissue for bone BODY TISSUES: CONNECTIVE TISSUE BLOOD ´ Vascular tissue ´ Consists of blood cells surrounded by a nonliving, fluid matrix called blood plasma ´ “fibers” - soluble proteins that become visible only during blood clotting ´ Functions: ´ Carrying nutrients, wastes, respiratory gases, white blood cells, and many other substances throughout the body BODY TISSUES: MUSCLE TISSUE MUSCLE TISSUE ´ Highly specialized to contract or shorten which generates the force required to produce movement ´ Contraction of muscle tissue is caused by sliding interaction of thick myosin filaments along thin actin filaments ´ Generate forced for contraction which drives movement within organ systems, of blood, and of body ´ TYPES: ´ Skeletal muscle ´ Cardiac muscle ´ Smooth muscle BODY TISSUES: MUSCLE TISSUE TYPES OF MUSCLE: ´ Skeletal muscle ´ AKA Striated muscle ´ Very long, multinucleated, cylindrical ´ WITH cross-striations (stripes) ´ Attached to skeleton for quick, forceful, voluntary contractions ´ Cardiac muscle ´ Smooth muscle BODY TISSUES: MUSCLE TISSUE TYPES OF MUSCLE: ´ Skeletal muscle ´ Cardiac muscle ´ Found only in the heart wall ´ Striated banding pattern but with only one nucleus, centrally located ´ Intercalated discs - represent the interfaces between adjacent cells and consist of many junctional complexes ´ Contains desmosomes and gap junctions ´ Smooth muscle BODY TISSUES: MUSCLE TISSUE TYPES OF MUSCLE: ´ Skeletal muscle ´ Cardiac muscle ´ Smooth muscle BODY TISSUES: MUSCLE TISSUE TYPES OF MUSCLE: ´ Skeletal muscle ´ Cardiac muscle ´ Smooth muscle ´ Aka visceral muscle ´ No striations are visible ´ Elongated (fusiform or spindle-shaped), tapering, and nonstriated cells ´ Major component of blood vessels and of the digestive, respiratory, urinary, and reproductive tracts and their associated organs ´ All cells are linked by numerous gap junctions à allow all the smooth muscle to contract synchronously or in a coordinated manner BODY TISSUES: MUSCLE TISSUE BODY TISSUES: NERVOUS TISSUE NERVOUS TISSUE ´ Neurons/Neurolemma ´ “Neurolemma” = cell membrane ´ Functional unit of the nervous system ´ Receive and conduct electrochemical impulses from one part of the body to another ´ Parts ´ Cell body - Contains the nucleus ´ Axon - Transmit impulses AWAY the cell body ´ Dendrites - Principal signal reception and processing sites ´ Neuroglia/Glial cells ´ Support neuronal survival and activities ´ 10 times more abundant than neurons BODY TISSUES: NERVOUS TISSUE NERVOUS TISSUE ´ Neuroglia/Glial cells BODY TISSUES BODY TISSUE ´ Epithelial tissue ´ Based on number of cell layer and shape of cells ´ Connective tissue ´ Loose (Areolar, Adipose, Reticular) ´ Dense (Regular vs Irregular) ´ Bone ´ Cartilage (Hyaline, Elastic, Fibrocartilage) ´ Blood ´ Muscle tissue ´ Skeletal ´ Cardiac ´ Smooth ´ Nervous tissue REVIEW ´ Cell and its parts ´ Nucleus ´ Plasma membrane ´ Cytoplasm ´ Membrane transport ´ Cell cycle ´ Central dogma ´ Body tissue and types ´ Epithelial tissue ´ Connective tissue ´ Muscle tissue ´ Nervous tissue REFERENCES Mann, ML. (2023). Histology handout. Topnotch Medical Board Prep Histology Handout. Marieb, Elaine N. Et al. (2018). Essentials of Human Anatomy and Physiology (12th ed); Singapore: Pearson Education South Asia Mescher, A.L. (2021) Junqueira's Basic Histology Text & Atlas. 16th Edition, McGraw Hill.