Anatomy CH.2
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- Robert Hooke 1635-1703
- 1665- saw small \"pore-like\" openings in cork and call them \"cells\" contemporary of Newton
- Anton von Leeuwenhoek 1632-1723
- 1674-1st person to see living cell (observed algae in water) living things are composed of cells
- Mathias Sheldon 1804-1881
- plant cells Cell Theory
- Theodore Schwaan 1810-1882
- animal cells Cell Theory
- The Cell Theory 1839
- Schleiden and Schwaan all organisms are composed of one or more cells cells are only produced by the division of pre-existing cells cells are the smallest units that perform all vital functions (basic units of life and structure
- Rudolf Virchow 1821-1902
- human cells (tumors) \"Omnis cellula e cellulae\" 1858 -every cells originates from other existing cells like it\"
- Two Types of Cells
- Sex and Somatic
- Sex cells
- germs cells that are derived from the testes (spermatozoa) or ovary (oocytes) germs cells (sperm and ovum)
- Somatic Cells
- all the remaining cells or cell types in the body (blood, bone, muscle, nerve, connective tissue)
- Microscopy
- study of internal structure and function of individual cells
- Light Microscopy
- uses transmitted light to permit magnifcation--up to 1000x
- Electron Microscopy
- uses a focused beam of electrons to examine cell ultrastructure up to 1000x smaller than seen with light microscopy 100,000x magnification
- The Cell\'s Environment/ Cellular Anatomy
- plasmalemma/cell membrane/plasma membrane cytoplasm extracellular fluid phospholipid bilayer
- Plasmalemma/cell membrane/plasma membrane --cellular anatomy
- on edge of cell, a thin membrane that separates the extracellular space from the inside of cell thin and delicate composed of phospholipids, proteins, glycolipids, and cholesterol
- Cytoplasm --cellular anatomy
- fluid medium inside the cell
- Extracellular Fluid --cellular anatomy
- watery medium where cells float high in sodium ions cations: Sodium, Potassium, Calcium anions: chloride, bicarbonate
- phospholipid bilayer --cellular anatomy
- contains proteins, glycolipids, and cholesterol
- 2 proteins in plasma membrane
- integral and peripheral
- integral proteins
- embedded in the phospholipid bilayer
- peripheral proteins
- associated with either the outside of the inside layers of the plasma membrane
- Functions of Cell Membrane
- separates intracellular fluid from extracellular fluid controls entry and exit of substances--permeability
- Permeability
- ease with which dissolved materials can cross a membrane passive and active
- Passive permeability -transport mechanisms -process
- without expending cellular energy: simple diffusion: movement from high to low concentration osmosis: diffusion of water from high to low filtration: movement across a membrane of solutes/dissolved nutrients by hydrostatic forces facilitated diffusion: special carrier proteins transport larger molecules (proteins)
- Active Transport -permeability
- requires cellular energy--adenosine may have carrier mechanism--pumps endocytosis and exocytosis 1st part of cell to be affected by changes in the extracellular fluid gives tissue a stable structure
- endocytosis
- packaging of extracellular materials into a vesicle for transportation into the cell -all required energy -pinocytosis: cell drinking (fluid) -phagocytosis: cell eating (particulate matter) -receptor-mediated endocytosis: specific molecules are brought in the cytosol
- exocytosis
- removal or release of intracellular materials from cell
- receptor-mediated endocytosis
- specific target molecules called ligands bind to receptors, generally glycoproteins, in the membrane surface -this creates a more specific and enhanced internalization during endocytosis
- Cytoplasm
- combination of intracellular fluid (cytosol) limited by the plasma membrance and in which are dispersed organelles (small organs)
- Cytosol
- intracellular fluid -high in potassium, proteins, amino acids, and lipids -low in carbohydrates, NaCl, calcium, and Mg -inclusion bodies
- Organelles
- structures in cell 1. non-membranous 2. membranous
- Nonmembranous Organelles
- not enclosed by a membrane; always in contact with cytosol EX. cytoskeleton elements, microvilli, centrioles, cilia, flagella, ribosomes
- Cytoskeleton
- gives the cell strength and flexibility Parts: microfilaments, microtubules, intermediate filaments, thick filaments
- microfilaments
- smallest in diameter (6-8 nm) double-stranded linear helical array mainly actin anchors to the cell membrane forms dense netowrk with cell membrane can cause movement of cell when interacting with myosin
- microtubules
- largest in diameter (20-20nm) nonbranching long hollow cylinders -gives strength and rigidity to the cell -responsible for changing shape of cell -can attach to organelle to give it structure -mechanism for cell movement
- intermediate filaments
- medium in size (8-10nm) rope-like fibers -stabilize position of organelles -provides strength
- microvilli
- small finger-like projections on cell membranes -all have similar length -increase surface area -involved in cells whose function is absorption -contain actin filaments -microfilaments inside anchor them to dense network do not move, do not branch -found in gut
- Cilia
- non-branching, motile cell processes -not as dense as microvilli -longer in length than microvilli -beat or sway to move secretions and fluids over or across surface of cell -9+2 arrangement of microtubules that beat or sway -found in respiratory tract nonmembranous
- Centrioles
- paired structures important in cell division for organizing tubules that exert traction on chromosomes -composed of nine pairs of triplets (3 microtubules) -arranged at right angles to each other nonmembranous
- Flagellum
- resemble cilia, but are much longer and more powerful -primarily found on spermatozoa in various stages of maturation; so they move cells, not material over the cell nonmembranous
- Ribosomes
- small, dense granular structures -contain mainly RNA -manufacture proteins -either free or fixed
- Two formations of ribosomes
- free: present in cytoplasm as a string-like formation, called polyribosomes (ploysomes) -make proteins for use inside the cell fixed: make protein for use outside the cell -associated with cisternae of the rER
- Membranous organelles
- surrounded by lipid membrane; isolated from cytosol -allows organelle to manufacture or store secretions EX. mitochondria, nucleus, endoplasmis reticulum, Golgi apparatus, lysosomes
- Mitochondria
- -has double membrane and inner folds (cristae) -number of mitochondria depends on the cell\'s energy demands -responsible for producing 95percent of the ATP within a cell -can migrate from one region to another -have their own DNA (genome) -increase their numbers by division and make their own structural proteins (have their own ribosomes) -evolved from aerobic bacteria -present in all cells except RBC and terminal skin cells
- Nucleus
- control center of cell operations -determines structural and function characteristics of cell by controlling what proteins are made and in what quantity -in eukaryotic cells, not in bacteria -surrounded by nuclear envelope -communicates with cytoplasm via nuclear pores -nucleolus: nuclear organelles that synthesize RNA -nucleoplasm: contents of nucleus; contains chromosomes (DNA, 23 pairs) membranous
- 2 critical cellular operations done by the Nucleus
- Transcription: using DNA to make mRNA segments Translation: mRNA segments move into the cytoplasm at ribosomes to serve as a code to synthesize new proteins
- Endoplasmic Reticulum
- network of intracellular membranes that from tube-like chambers called cisternae RER: rough, has ribosomes for transport\' protein secreting cells SER: smooth, synthesis of lipids and carbs (no ribosomes); making cholesterol or steroid-like compounds membranous
- 4 Functions of Endoplasmic Reticulum
- -synthesis of carbs, lipids, proteins -storage of synthesized molecules -transport of molecules -detoxification
- Golgi Apparatus
- series of membranous plates- cisternae that give rise to lysosomes and secretory vesicles membranous
- Functions of Golgi Apparatus
- -package material for lysosomes (that contain hydrolytic enzymes) -create membrane segments -form secretory vesicles that are tagged and excreted from the cell via exocytosis -synthesize and package secretions -package special enzymes
- transport vesicles
- carry packaged secretions of RER to Golgi apparatus -fuse with surface membrane of Golgi apparatus and empty into cisternae
- secretory vesicles
- formed by Golgi apparatus membrane -fuse with cell membrane and discharge their contents into extracellular fluid--exocytosis
- Lysosomes
- vesicles from Golgi apparatus that remain in the cell\'s cytoplasm -filled with hydrolytic enzymes -endocytotic vesicles fuse with lysosomes to eventually metabolize material taken into cell membranous
- 3 Functions of Lysosomes
- 1. removes bacteria and organic debris from cytoplasm and isolate it into vesicles 2. contains digestive enzymes 3. releases nutrient components into cytosol and expels waste by exoccytosis
- 3 types of Intercellular Attachments--Cell Junctions
- occluding, anchoring, communicating
- Occluding Junctions
- represent a seal between 2 cells zonula occludens: block passage of water and other substances between 2 cells (aka tight junction)
- Anchoring Junctions
- zonula adherens: more like a sheet between cells; longer macula adherens: spot-weld, strong, resist stretching and twisting (aka desosome)
- Communicating Junctions
- Gap junction: allows for passage of small molecules (aka electrical, nexus)
- Zonula occludens
- blocks the passage of water or other substances from passing between cells occluding junction
- Zonula adherens
- -provide lateral adhesion between epithelial cells -interact with actin filaments within the cell anchoring junction
- Macula adherens
- -complex structure that involves dense proteins at the intercellular space -reinforced with network of intermediate filaments anchoring junction
- Gap junction (electrical or nexus)
- -permit the direct passage of signaling molecules (ions) between cells -narrow channels connect adjacent cells communicating junction