Chapter 3

Cytology

the scientific study of cells

Cell theory

1. All organisms composed of cells and cell products
2. Cell is the simplest structural and functional unit of life 3. An organism’s structure and functions are due to
activities of cells
4. Cells come only from preexsting cells
5. Cells of all species exhibit biochemical similarities

squamous

a thin, flat, scaly shape, often with a bulge where the nucleus is, much like the shape of a fried egg “sunny side up”. These cells line the esophagus and air sacs (alveoli) of the lungs, and form the surface layer (epidermis) of the skin

Cubodial

squarish-looking in frontal sections and about equal in height and width; liver cells

comunar

distinctly taller than wide, such as the inner lining cells of the stomach and intestines

polygonal

having irregularly and angular shapes with four, five, or more sides, like the wax cells of a honeycomb. The densely packed cells of many glands are polygonal

stellate

having multiple pointed processes projecting from the body of a cell, giving it a somewhat starlike shape. The cell bodies of many nerve cells are stellate. Typically found in the nervous system

spheroidal to ovoid

round to oval, as in egg cells and white blood cells

discoidal

disc-shaped, as in red blood cells

fusiform

spindle-shaped; elongated, with a thick middle and tapered ends, as in smooth muscle cells

fibrous

long, slender, and threadlike, as in skeletal muscle cells and the axons (nerve fibers) of nerve cells

cytoplasm

the contents of a cell between its plasm membrane and its nuclear envelope, consisting of cytosol, organelles, inclusions, and the cytoskeleton

Transmission Electron Microscope

a microscope that uses an electron beam in place of light to form high-resolution, 2D images of ultrathin slices of cells or tissues; capable of extremely high magnification

Ultrastructure

a fine degree of detail extending even to the molecular level

empty magnification

if enlargement fails to reveal any more useful detail

scanning electron microscope

a microscope that uses an electron beam in place of light to form high resolution, 3D images of the surfaces of objects; capable of much higher magnifications than a light microscope

vascular corrosion cast

a technique for visualizing the blood vessels of an organ. The vessels are drained and flushed with saline, then carefully filled with resin. After the resin solidifies, the actual tissue is dissolved with a corrosive agent such as potassium hydroxide. This leaves only a resin cast of the vessels, which is then photographed with the SEM

plasma cell membrane

the membrane that encloses a cell and controls the traffic of molecules in and out of the cell

cytosol

a clear, featureless, gelatinous colloid in which the organelles and other internal structures of a cell are embedded

Intracellular fluid

the fluid contained in the cells; one of the body’s major fluid compartments

Extracellular fluid

any body fluid that is not contained in the cells; for example, blood, lymph, and tissue fluid

tissue (intertitual) fluid

pertaining to the extracellular spaces in a tissue; located between other structures, as in the interstitial cell of the testis and interstitial (extracellular) fluid of the other tissues

intracellular face

side that faces the cytoplasm

extracellular face

faces the outward side of cytoplasm

glycocalyx

a carbohydrate coating on the cell surface with multiple functions

Transmembrane protein

intergral protein that extends through a plasma membrane and contacts both the extracellular and intracellular fluid

peripheral protein

a protein of the plasma membrane that clings to its intracellular or extracellular surface but does not penetrate into the phospholipid bilayer

Receptors

are usually specific for one particular messenger

many of the chemical signals by which cells communicate cannot enter the target cell but bind to surface proteins

enzymes

carry out the final stages of starch and protein digestion in the small intestine, help produce second messenger, and break down hormones and other signaling molecules whose job is done, thus stopping them from excessively stimulating a cell

channel proteins

are passages that allow water and hydrophilic solutes to move through the membrane

leak channels

always open and allow materials to pass through continually

gates (gated channels)

open and close under different circumstances and allow solutes through at some times, but not others

ligand-gated channel

a channel protein in a plasma membrane that opens or closes when another chemical (ligand) binds to it, enabling the ligand to determine when substances can enter or leave the cell

voltage-gated channels

changes in electrical potential across the plasma membrane

mechanically gated channels

physical stress on a cell, such as stretch and pressure.

channelopathies

defects in channel proteins responsible for family of diseases

carriers

transmembrane proteins that bind to glucose, electrolytes, and other solutes and transfer them to the other side of the membrane

cell-identity markers

glycoproteins contribute to the glycocalyx, which acts like an identification tag that enables the immune system to tell which cells belong to one’s body and which are foreign invaders

cell-adhesion molecules

cells adhere to one another and to extracellular material through membrane proteins called cell-adhesion molecules (CAMs)

second messenger

a chemical that is produced within a cell or that enters a cell in response to the binding of a messenger to a membrane receptor, and that triggers a metabolic reaction in the cell

G protein

a protein of the plasma membrane that is activated by a membrane receptor and, in turn, opens an ion channel or activates an intracellular physiological response; important in linking ligand - receptor binding to second-messenger systems

adenylate cyclase

an enzyme of the plasma membrane that makes cyclic adenosine monophosphate by removing two phosphate groups from ATP; important in the activation of the cAMP second-messenger system

cyclic AMP (cAMP)

a cyclic molecule produced from ATP by the enzymatic removal of two phosphate groups; serves as a second messenger in many hormone and neurotransmitter actions

kinase

any enzyme that adds an inorganic phosphate group to another organic molecule. Also called a phosphokinase

microvillus

an outgrowth of the plasma membrane that increases the surface area of a cell and functions in absorption and some sensory processes; distinguished from cilia and flagella by its smaller size and lack of an axoneme

brush border

a fringe of micovilli on the apical surface of an epitherlial cell, serving to enhance surface area and promote absorption

axoneme

the central core of a cilium or flagellum, composed of microtubules; these are arranged in a circular array of nine microtubule pairs, and in flagella and mobile cilia, another microtubule pair at the center of the circle

micortubules

array of thin protein cylinders

dyein

a motor protein involved in the beating of cilia and flagella and in the movement of molecules and organelles within cells, as in retrograde transport in a nerve fiber

pseudopod

a temporary cytoplasmic extension of a cell used for locomotion and phagocytosis

macrophages

tissue cells derived from certain white blood cells

cytoskeleton

a system of protein microfilaments, intermediate filaments, and microtubules in a cell, serving in a physical support, cellular movement, and the routing of molecules and organelles to their destination within the cell

microfilaments (thin filaments)

made of a protein called actin. Widespread throught the cell but especially concentrated in a fibrous mat

terminal web

fibrous mat on the cytoplasmic side of the plasma membrane

intermediate filaments

thicker and stiffer than microfilaments. Gives the cell its shape, resist stress, and form junctions that attach cells to their neighbors

microtubule

an intracellular cylinder composed of the protein tubulin, forming centrioles, the axonemes of cilia and flagella, and part of the cytoskeleton

tublin

long chain of globular proteins

centrosome

hold organelles in place, form bundles that maintain cell shape and rigidity, and act like monorail tracks for motor proteins carrying organelles and macromolecules to specific destinations in the cell

organelles

any structure within a cell that carries out one of its metabolic roles; an intracellular structure other than the cytoskeleton and inclusions

membranous organelles

organelles surrounded by membranes

nucleus

a cell organelle containing DNA and surrounded by a double membrane

annuclear

having no nucleus

nuclear envelope

a pair of membranes enclosing the nucleus of a cell, with prominent pores allowing traffic of molecules between the nucleoplasm and cytoplasm

nuclear pore complex

ring of proteins

nuclear lamina

narrow but densely fibrous zone composed of a web of intermeidate filaments.

nucleoplasm

material in the nucleus

chromatin

filamentous material in the interphase nucleus, composed of DNA and associated proteins

nucleoli

dark-staining masses

endoplasmic reticulum

an extensive system of interconnected cytoplasmic tubules or channels; classified as rough ER or smooth ER depending on the presence or absence of ribosomes on its membrane

cistern

a fluid-filled space or sac, such as the cisterna chyli of the lymphoid system and cistern of the endoplasmic reticulum and golgi complex

rough endoplasmic reticulum

the cisterns are parallel, flattened sacs covered with granules

smooth endoplasmic reticulum

the cisterns are more tubular, branch more extensively, and lack of ribosomes

ribosomes

a granule found free in the cytoplasm or attached to the rough endoplasmic reticulum or nuclear envelope composed of ribosomal RNA and enzymes

golgi complex

an organelle composed of several parallel cisterns, somewhat like a stack of saucers, that modifies and packages newly synthesized proteins and synthesizes and carbohydrates

golgi vesicles

a membrane-bounded vesicle pinched from the golgi complex, containing its chemical product; may be retained in the cell as a lysosome or become a secretory vesicle that releases the produce by exocytosis

secretory vesicles

store a cell product for later use

lysosome

a membrane-bounded organelle containing a mixture of enzymes with a variety of intracellular and extracellular roles in digesting foreign matter, pathogens, and expired organelles

autolysis

digestion of cells by their own internal enzymes

peroxisomes

resemble lysosomes but contain different enzymes. Produced by a collaboration between the endoplasmic reticulum and mitochondria and by fission of preexisting peroxisomes.

proteasome

protein disposal; hollow, cylindrical complexes of proteins located in both the cytoplasm and nucleus

mitochondria

organelles specialized for synthesizing ATP

crista

an anatomical crest, such as the crista galli of hte ethmoid bone or the crista of a mitochondrion

matrix

the extracellular material of a tissue; the fluid within a mitochondrion containing enzymes of the citric acid cycle

centriole

an organelle composed of a short cylinder of nine triplet of microtubules, usually paired with another centriole perpendicular to it

centrosome

clear patch of cytoplasm, containing a pair of mutually perpendicular centrioles

inlcusion

any visible object in the cytoplasm of a cell other than an organelle or cytoskeletal element; usually a foreign body or a stored cell product

cystic fibrosis

hereditary disease in which cells make chloride pumps, but fail to install them in the plasma membrane

inclusions

any visible object in the cytoplasm of a cell other than an organelle or cytoskeletal element; usually a foreign body or a stored cell product, such as a virus, dust particle, lipid droplet, glycogen granule, or pigment