General Biology 1 1st Quarter Cell Types and Modifications PERFORMANCE TASK 2: ANIMAL TISSUES -Compare and contrast the structure and functions of each type of animal tissue -Explain what will happen if one type of cell malfunctions -Create a graphic organiser that summarises the structure and function of animal tissues ********************************************************************** I. Compare and contrast the structure and functions of each type of animal tissue 1. Epithelium: covers body surfaces, lines cavities, forms glands 2. Muscle: made up of contractile cells and is responsible for movement 3. Nerve: receives, transmits and integrates information from outside and inside the body to control the activities of the body 4. Connective: underlies or supports the other three basic tissues, both structurally and functionally FOUR MAJOR TYPES OF TISSUES: EPITHELIUM, NERVE, MUSCLE AND CONNECTIVE -There are some cell types that are separated by intercellular spaces. -However, there are many cell types that are jam packed by intercellular junctions. -INTERCELLULAR JUNCTIONS: structures that connect the cell membranes of animal cells -TYPES OF INTERCELLULAR JUNCTIONS 1. Tight Junctions -membranes converge and fuse; area of fusion wraps around the cell like a belt -typically binds thin sheetlike layers 2. Desmosomes -rivets or “spot welds” skin cells -connects adjacent cells -enables a ell to form a structural unit EPITHELIUM (EPITHELIAL TISSUE) -closely aggregated polyhedral cells; adheres to the connective tissue through the EXTRACELLULAR MATRIX (ECM) -lines and covers body surfaces and/or body cavities, forms glands -also secretes substances (glands; endocrine and exocrine) -4 major functions: protection, secretion, absorption, excretion GENERAL FUNCTIONS -Protection: forming a protective barrier -the epithelium forms a selective barrier between the external environment, internal cavities, fluid connective tissue (blood and lymph) and the underlying connective tissue. -SELECTIVE BARRIER: facilitates/regulate the entry/exit of q certain substances between the external environment and the connective tissue. -Regulates exchange of molecules between cells (selective diffusion and absorption); -Synthesis and secretion of glandular product -SECRETION: columnar epithelium of the stomach and the gastric glands GENERAL CHARACTERISTICS 1. Lack blood vessels 2. Epithelial cells are tightly packed; adheres to one another through the intercellular junction 3. Epithelial cells readily divide, this is to assure that injuries heal rapidly as new cells replace lost or damaged ones. CELL REGENERATION AND EPITHELIAL REPAIR 4. Epithelial cells are bound to adjacent cells by intercellular junctions -TYPES OF INTERCELLULAR JUNCTIONS 1. Tight/Occluding Junctions -membranes converge and fuse; area of fusion wraps around the cell like a belt -typically binds thin sheetlike layers -seal between adjacent cells -SUBSTANCES WON’T BE ABLE TO PASS 2. Adherent/Ancho ring Junction -rivets or “spot welds” skin cells -connects adjacent cells -enables a cell to form a structural unit -additional support for tight junctions DESMOSOMES AN EXAMPLE OF ANCHORING JUNCTION -does not cover the whole cell HEMIDESMOSOME AN EXAMPLE OF ANCHORING JUNCTION -cell to basement membrane 3. Gap Junctions -tubular channels that link the cytoplasm of adjacent cells for exchange of substances -two openings of a cell are connected -CELL TO CELL COMMUNICATION -phospholipid bilayer moves to align 5. LAMINA PROPRIA: connective tissue that underlies the epithelial lining (for digestive, urinary systems) -has PAPILLAE: small evaginations projecting from the CT TO ET (taste buds or covering of the skin) 6. Always has an APICAL CELL SURFACE exposed to the outside or internally to an open space. -APICAL CELL SURFACE; apical pole -increase surface area for absorption or to move substance along the epithelial surface. -microvilli, stereo cilia and cilia MICROVILLI: cylindrical projections extending from ACS; extends cell surface for absorption or secretion CILIA: hair-like projections; sweeps away foreign bodies and secretions; especially in trachea, bronchi branches and nasal cavity STEREO CILIA: longer than microvilli; facilitate absorption in epididymis and tubular deferens 7. POLARITY -BASAL POLE (Basal Region; where basement membrane is) : region of the cell contacting the ECM and CT; close to the CT; attaching ET to the basement membrane -APICAL POLE: region facing a space; lumen (apical cell surface) 8. BASEMENT MEMBRANE (ECM BASICALLY) -a thin, nonliving layer that anchors the epithelium to the underlying connective tissue -scaffold for rapid epithelial repair and regeneration -semi-permeable; all substances going in or out must pass through the epithelium -made up of basal lamina and reticular lamina CLASSIFICATION OF EPITHELIUM -classified according to the number of cell layers and shape -according to the number of layers: 1. Simple: only one cell layer 2. Stratified: two or more layers of cells (the shape and height of the cells vary in each layer, however, only the surface layer is used in classification -according to cell shape 1. Cuboidal: cube shaped; width, height, and depth are approx. the same; nucleus = large 2. Columnar: elongated; when height exceed the width; nucleus = elongated 3. Squamous: thin, flattened cells; with of the cell is greater than the height; nucleus = flattened -can also be classified according to the special features it possesses 1. Pseudostratified Epithelium 2. Transitional Epithelium 3. Glandular Epithelium SIMPLE EPITHELIA 1. Simple Squamous -single layer of flattened cells; nuclei = broad and thin -substances pass easily -common at sites of diffusion and filtration -lining of vessels (endothelium), covers serous lining of cavities, mesothelium—pericardium (heart), peritoneum (abdominal cavity), pleura (lungs, thoracic cavity) -facilitates movement of viscera (meso), active transport by pinocytosis (meso and endo), secretion of active molecules (meso) 2. Simple Cuboidal -singe layer of cube-shaped cells; nuclei = centrally located -Covering of thyroid and ovary, lines of kidney tubules, and ducts of certain glands 3. Simple Columnar -single layer of elongated cells; specialised for absorption (MICROVILLI); nuclei = near basement membrane -GOBLET CELLS = scattered throughout, secretes mucus—protective fluid—to ACS -can be ciliated or non-ciliated CILIATED SIMPLE COLUMNAR EPITHELIA -cilia moves constantly -in the female repro system, it aid in moving the egg through the fallopian tubes to the uterus NON-CILIATED SIMPLE COLUMNAR -lines uterus and portions of digestive tract—stomach and intestines -secretes digestive fluids and absorbs nutrients from digested food; protection, lubrication, absorption, and secretion STRATIFIED EPITHELIA -many layers of cells; thick 1. Stratified Squamous -multiple layers of flattened cells -epidermis = keratinized, prevents water loss -as cells mature, they are pushed outward, accumulate KERATIN -due to the accumulation of keratin, cells harden and die -oral cavity, esophagus, vagina and anal canal = not keratinized 2. Stratified Cuboidal -two or three layers of cuboidal cells -provides more protection -larger ducts of certain glands, ovaries & seminiferous tubules -secretion and protection 3. Stratified Columnar -multiple layers of elongated cells, basal layers are cuboidal -male urethra and pharynx, conjunctiva -protection 4. Transitional Epithelia (UROTHELIUM) -protection, distensibility -bladder, ureters, renal calyces—excretory system -forms a barrier that prevents contents of the urinary tract from diffusing back into the internal environment -umbrella cells PSEUDOSTRATIFIED COLUMNAR EPITHELIA -single layer, elongated cells; nucleus is levels in different levels, all are still attached to BM/BL, not all reaches ACS -found in lining of respiratory passages -protection, secretions, movement of mucus and substances SECRETORY EPITHELIA GLANDULAR EPITHELIA -Glands: produces and secretes macromolecules -EXOCRINE & ENDOCRINE GLANDS -Exocrine: secretes substances onto a tissue or surfaces -one epithelial cell = unicellular -multicellular gland = simple or compound glands -Simple: communicates w/ surface via duct—doesn’t branch -Compound: duct branches repeatedly -Classified according to shape -Tubular: epithelial-lined tubes -Alveolar/Acinar Glands: form saclike dilations -Endocrine: secretes substances onto bloodstream or tissue fluid; no ducts -TYPES OF GLANDULAR SECRETIONS 1. Apocrine: loses small portions of glandular cell 2. Holocrine: releases entire cell, disintegrates—releasing secretion 3. Merocrine: exocytosis (vesicle fusion to the cell membrane then diffuses secretion through it) CONNECTIVE TISSUES GENERAL CHARACTERISTICS -connective tissue cells are farther apart than epithelial cells -has an abundance of extracellular matrix -EXTRACELLULAR MATRIX: made up of protein fibres (collagen and ground substance (proteins) -GROUND SUBSTANCE: binds, supports and provides a channel in which substances may be exchanged between the blood and cells of the tissue; allows diffusion of small molecules -Highly hydrated, transparent -also acts as a lubricant and barrier to invaders -connective tissue cells usually divide -connective tissues are usually nourished and have good blood supplies; medium for diffusion of nutrients and waste products -there are flexible and rigid connective tissues -ARISES/STARTS FROM MESENCHYME (animal tissue, origin of connective tissue) GENERAL FUNCTIONS -bind structure; provides a matrix that supports and physically connects other tissues and cells -serves as framework -provide support and protection of tissues and organs -fill spaces -produce blood cells -protect against infections -help repair tissue damage MAJOR CELL TYPES 1. Fixed Cells -are cells that resides in the connective tissue for an extended or long period of time -e.g. mast cells and fibroblasts 2. Wandering Cells -usually just moves through or appears temporarily in connective tissues, usually in response to an infection or injury -e.g macrophages COMPOSITION OF THE CONNECTIVE TISSUE 1. Fibroblasts -most common type of fixed cell; key cell -large, star-shaped -produce fibers (collagenous, elastic and reticular) by the secretion of proteins into the ECM of the connective tissue -FIBROBLAST VS. FIBROCYTE -FIBROBLAST = ACTIVE CELL, BIG NUCLEUS -FIBROCYTE = INACTIVE CELL, SMALL NUCLEUS 2. Macrophages -also called histiocytes, started out as white blood cells (monocyte) -plays a vital role in immunity -are scavenger cells; phagocytosis -engulfs foreign bodies within the tissue 3. Mast Cells / Basophilic Leukocytes -usually near blood vessels in skin & tissue lining -releases substances crucial to tissue repair, immunity and inflammatory response; SEE HEPARIN AND HISTAMINE -secretes HEPARIN, a compound that prevents blood clotting or thrombosis -also secretes HISTAMINE, a substance that activates reactions related to allergies and inflammation. SEE ANTIHISTAMINE 4. Plasma Cells -antibody secreting cells abundant in inflamed tissues -ANTIBODY = tells macrophages which bacteria, etc are foreign bodies 5. Leukocytes (White blood cells) -different kinds; differs in their function -EOSINOPHILIC = defence against parasites; modulation of allergic/vasoactive reactions -NEUTROPHILIC = phagocytosis of bacteria 6. Adipocytes -cytoplasm is storage of neutral fats (lipid) for insulation -fat cells of adipose tissue -CUSHION AND INSULATION OF SKIN AND ORGANS 7. Lymphocytes -immune/defence functions CONNECTIVE TISSUE FIBERS = formed from proteins that polymerize after secretion from fibroblasts 1. Collagenous Fibers -thick threads of the protein COLLAGEN -flexible but only slightly elastic -have great tensile strength; can resist pulling force -important component in ligaments and tendons 2. Elastic Fibers -composed of springlike protein called ELASTIN -ELASTIN for elasticity -easily stretched or deformed but can assume its original lengths when tension or force is removed -body parts normally subjected to stretching 3. Reticular Fibers -thin collagen fibres -form supportive network within tissues CLASSIFICATION OF CONNECTIVE TISSUES *only tissues written in bold are to be studied* 1. Connective Tissue Proper (the tissue itself) 1. Loose Connective Tissue: little collagen fibres more ground sub -Areolar Tissue -cells are mainly fibroblasts -binds the skin to the underlying organs and fills spaces between muscles -usually underlies epithelial tissue, its blood vessels nourish the epithelium -abundant ground substance -Adipose Tissue -fat -when adipocytes (cells) store fat in their cytoplasm, and they are abundant, they form the adipose tissue -around the kidneys, behind they eyeballs, on the surface of the heart -Reticular Tissue -composed of 3D network of collagenous fibres -provides framework for certain organs (liver, spleen) 2. Dense Connective Tissue: abundant in collagen fibres -Dense Regular -consists of many densely packed, thick, collagenous fibres -binds body parts such as ligaments and tendons -blood supply is poor = slow tissue repair -strong, enables tissue to withstand pulling forces -Dense Irregular -thicker, interwoven, more randomly organised -allows the tissue to sustain tension exerted in many directions -is found in the dermis (inner skin layer) -little ground substance, abundant in collagen fibres -Elastic -found in the attachments between bones of the spinal column 2. Specialised Connective Tissues -Cartilage -rigid connective tissue -tough, resilient -supports certain soft tissues and provides cushion, low friction surfaces in joints -Chondrocytes (cells) in lacunae (cavity where they are situated) -Avascular (no blood vessels), get their nutrients from perichondrium (CT that envelopes cartilage if not joint) -Hyaline Cartilage: -Hyalos = glass, semitransparent in fresh state -most common -fine collagenous fibers -important in development and growth of plants -found in respi. passages, ends of ribs, movable joints -provides smooth, low friction surfaces in joints, structural support for RT -Elastic Cartilage -more flexible vs. hyaline -abundant in elastic fibers -framework for external ear, epiglottis, parts of larynx -flexible shape and support of soft tissues -Fibrocartilage -combinations of hyaline and small amounts of dense CT -tough tissue, many collagenous fibres -serves as a shock absorber; cushions bones, tensile strength -intervertebral discs, insertions of tendons -Bone -most rigid connective tissue; due to mineral salts -abundant in collagenous fibres -supports body structures, protect vital structures, attachment for muscles -containes bone (red) marrow = rbc’s, stores and releases inorganic chemicals -osteocyte, osteoclast, osteoblast, osteon, lacunae, lamellae, canaliculi -Bone cells = osteocytes, located in lacunae which forms circles around central canals -Osteocytes transports nutrients and wastes through minute tubes called canaliculi -osteocblasts become osteocytes when they are surrounded by bone matrix -Blood -cells are suspended in matrix called PLASMA -cells = rbc’s (erythrocytes); transports gases, wbc’s (leukocytes) fights infection, platelets (thrombocytes) initiates thrombosis (blood clotting) MUSCLE TISSUES GENERAL CHARACTERISTICS -are contractile; can shorten and thicken; contract and relax -with the ability to contract, muscle cells pull, making body parts move (within organs systems) -muscle cells = muscle fibres bc elongated -composed of myosin and actin; responsible for muscle contraction -SATELLITE CELLS: MUCSCLE REPAIR -Originated/arises from myoblasts TYPES OF MUSCLE TISSUES 1. Skeletal Muscle Tissue 1. Forms muscles that usually attach to bones, elongated fibres 2. Moves the head, torso, limbs and enables us to make facial expressions, sing, chew, swallow, breathe. VOLUNTARY 3. HAS STRIATIONS. 4. bundles of long, multinucleated cells 2. Smooth Muscle Tissue 1. Called smooth because they lack striations (light and dark cross markings) 2. Cannot be simulated to contract by conscious effort. SLOW INVOLUNTARY 3. Moves food, empties urinary bladder, constricts blood vessels 4. Found in the uterus, urinary bladder, intestines, stomach 3. Cardiac Muscle Tissue 1. Only in the heart, CARDIAC NGA EH 2. Its cells are interconnected, branching, elongated (often branched) 3. INTERCALATED DISC: where cells touch each other 4. INVOLUNTARY, can continue to function even without nerve impulses 5. HAS STRIATIONS **THE PROCESS OF MUSCLE CONTRACTION** NERVE TISSUES GENERAL CHARACTERISTICS -found in the brain, spinal cord, CENTRAL AND PERIPHERAL NERVOUS SYSTEM -elongated cells with extremely fine processes -transmission, receiving, generating, and integrating nerve impulses -TWO KINDS -NEURONS sense changes and respond by transmitting nerve impulses to other neurons or to muscles or glands -coordinate and regulate body activities -GLIAL CELLS = support protection, neural nutrition NEUROGLIA: phagocytosis, carry and bind components of the nervous tissue, supply needed nutrients for growth to neurons from blood vessels. Plays a role in cell-to-cell communications. SMALLER THAN NEURONS. NEURON (FUNTIONAL UNIT) THREE MAIN PARTS 1. Cell Body (perikaryon/soma): nucleus and organelles 2. Dendrites: elongated processes; receive stimuli from other neurons at a site called synapse (spaces between neurons) 3. Axon: single long process; generate and conduct nerve impulses to other cells TYPES OF NEURONS ACCORDING TO AXON PLACEMENT 1. Multipolar Neuron: numerous branched dendrites on one side of cell body, axon on the other 2. Bipolar Neuron: axon and dendrites stem from two polars of cell body 3. Unipolar Neuron: one axon, stemming from one side of cell body 4. Anaxonic Neuron: axons and dendrites stem from all around the cell body TYPES OF NEURONS ACCORDING TO 1. Sensory Neurons - afferent 2. Motor Neurons - efferent = response to stimuli 3. Interneurons - establishes FUNCTIONAL CLASSIFICATION = receives stimuli from receptors sends impulses to effector organs in relationships among other neurons SYNAPSE -sites where nerve impulses are transmitted -transmission is unidirectional (presynaptic cell to postsynaptic cell) TYPES OF SYNAPSES GLIAL CELLS 1. Oligodendrocytes - form myelin sheaths that insulate the axons in the CNS and facilitate nerve impulses 2. Astrocytes - structural and metabolic support of neurons in the CNS especially in synapses; neuronal development, replicates to occupy space of dying neurons 3. Ependymal Cell - aid in production and movement of cerebrospinal fluid ; lines ventricles of brain and central canal of spinal cord 4. Microglia - phagocytic cell in the CNS; defense and immune-related activities; SEE MACROPHAGE *OLIGODENDROCYTES, ASTROCYTES, EPENDYMAL CELLS, MICROGLIA = CNS 5. Schwann Cell - myelin production, electrical insulation in the PNS 6. Satellite Cell - structural and metabolic support for neuronal cell bodies in the PNS
