45 terms

Histology and Embryology

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Cells
smallest structure in the body, permit excitability, synthesis, membrane transport, and reproduction.

they are the building blocks of tissue in the body
Types of Cell Junctions
desmosomes-cell to cell attachment (Ex. ameloblasts and oral epithelium cells)

tight junctions- cells attach to each other by fusion of their cell membranes (ex. Odontoblasts)

gap junctions- contains a channel that runs between the cells for communication of cell electrical impulses and passage of molecules (Ex. some odontoblasts, allows them to coordinate their activity)

hemidesmosome- cell to noncellular surface, present in the junctional epithelial attachment of the tooth (Ex. stratified squamous epithelial tissue connects to connective tissue by cells connecting to the basal lamina)
Components of the cell
cytoplasm
organelles
inclusions
nucleus
specialization
differentiation- cells recognize each other and group together (cancer cells do not recognize each other)

Organization of chemicals

cells-->tissues-->organs-->organ systems
Cell membrane
aka: plasma membrane or plasmalemma, about 7 nanometers thick, selectively permeable because it controls the passage of materials in and out of the cell
Selective permeability characteristics
protects cell from external environment

permits entrance and exit of selected substrates

uses active transport, passive transport, or facilitated diffusion
Major component ratios of the cell membrane
3:2 protein to lipids
structure of cell membrane
trilaminar; bipolar membrane, central core of lipids between two layers of prottein
lipid bilayer of the cell membrane
contains phospolipids, hydrophilic ends face outward, hydrophobic ends face inwards towards each other.

Globular proteins: periperal proteins are attached to the surface and integral proteins fill the full width of the membrane.
Cytoplasm
traslucent, aqueous, homogenous gel enclosed in the cell by the cell membrane; organelles and inclusions are suspended in the cytoplasmic gel.
all metabolic activities of the cell occur in:
the cytoplasm
metabolic activities of the cell:
assimilations- digestions

synthesis- proteins, proteoglycans, and glycoproteins

transport medium- where all nutrients and metabolites are carried from one organelle to another

presence of enzymes and electrolytes- where specific metabolic reactions take pace, like glycolysis
nucleus
controls 2 main functions of cell:
1. chemical reactions- synthesizing activities; determines nutrient needs
2. stores genetic information

also has a membrane and contains nuclear matrix with chromosomes
chromosomes
store genetic information of cell, 46 in the human cell nucleus, visible only during cell division, when not in division chromosomes are in clumps called chromatin
nucleolus/nucleoli
round, dense structures that produce ribosomal ribonucleic acid (RNA) protein plus RNA;
Synthesis activities
Occurs at ribosomes and polyribosomes; ribosomes attached to ER make proteins that transfer out of cell, polyribosomes that float normally produce proteins used within the cell for metabolic purposes
3 types of RNA needed for protein synthesis
1.messenger mRNA- copies sort segments of DNA, the genetic code
2. tRNA- carrier of specific amino acids (building block of protein)
3. ribosomal rRNA- found floating freely in the cytoplasm
Inclusions
transitory, nonliving metabolic byproducts found in the cytoplasm of the cell

appear as lipid droplets, carbohydrate accumulations, or are engulfed in foreign substances
Lysosomes
membrane bound organelles responsible for the breakdown of foreign substances that are engulfed by the cell by the process of phagocytosis or pinocytosis

produced by Golgi complex,

spherical vesicles that contain hydrolytic enzymes

once cell forms a secondary vesicle through phagocytosis, it can remain as a residual body or be discharged outside the cell

Vitamins a and E and Zinc are important stabilizers of the lysosome membrane
Golgi Complex
consists of stacks of closely spaced membranous sacs, in which newly formed proteins are concentrated and prepared for export out of the cell

secretes a variety of proteins synthesize by the ER

major site of membrane formation and recycling

storage site for newly synthesized proteins

site for packaging and transporting many cell products (e.g. polysaccharides, proteins, and lipids)

synthesis site for lysosomes.

also site for production of large carbohydrate molecules
Mitochondria
power house of the cell, provides energy by oxidation of nutrients

cristae (inner matrix) gives the organelle more working surface area

transforms chemical energy bonds of nutrients into ATP adenosine triphosphate

a single cell may contain 50-2500 mitochondria depending on the cell's energy needs
Endoplasmic reticulum
found throughout cytoplasm, two types (Granular of rough-endoplasmic reticulum: contains ribosomes on the cytoplasmic side of membrane: site of protein synthesis. Agranular of smooth surfaced- no ribosomes present, site of steroid synthesis

functions to synthesize, circulate, and package intracellular and extracellular materials
Filaments and Tubules
Thread like structures approximately 7-10 nm thick,

thicker filaments act as filaments seen in muscle and perform contractile functions

microfilaments act as a support system for the cell cytoskeleton

bundles of microfilaments form tonofibrils and become part of the attachment apparatus (desmosomes) between cells
Microtubules
20-27nm wide, delicate, found in cells undergoing mitosis.
centrioles
cylindrical structures composed of microtubule like components, function in cell replication and the formation of cellular extensions
Internal environment and homeostasis
extracellular fluid- circulates outside and between cells, must be regulated exactly

intracellular fluid- located inside the cell

homeostasis- the delicate balance maintained between extracellular and intracellular fluid
Transport through the cell membrane: Diffusion
Continuous movement of molecules among one another in liquids or gas, moves from region of high concentration to low concentration (the diffusion gradient), will eventually equal out,

factors that effect diffusion are temperature, concentration, distance of cell membrane, substance solubility to liquids

oxygen, CO2 and alcohol are lipid soluble and diffuse quickly, water is not
Facilitated diffusion
involves the use of carrier substance to transport a non-lipid soluble substance across the cell membrane

does not involve use of energy
diffusion through pores
substances must be less than 0.8nm to pass through pores

pores lined with Ca ions, so positive elements are repelled

antidiuretic hormone can reduce pore size.
Osmosis
process of net diffusion of water through a semi-permeable membrane caused by a concentration difference
osmotoic pressure
pressure that develops in a solution as a result of the net osmosis into that solution, affected by the number of dissolved particles per unit volume of fluid.
isotonic solution
when placed on outside of cell, will not cause osmosis
hypertonic solution
when placed on outside of cell, will cause osmosis out of the cell and lead to crenation, shrinking of the cell
hypotonic solution
when place on outside of cell will cause osmosis into the cell and lead to cell lysis *(hypo-explode)*
Active transport
process used when large quantities of a substance are needed inside of the cell and only a small amount of the substance is present in the extracellular fluid

requires energy, pumps against concentration gradient

keeps sodium extracellular and potassium intracellular, important for transmission of nerve impulses

*think you want bananas inside tummy but not sodium.*

used on almost all monosaccharides
Phagocytosis
movement of solid particle into the cell through invagination around a particle with the cell membrane
Pinocytosis
same process as phagocytosis but with fluid instead of particles.
Cell replication
Mitosis and Meiosis
Mitosis
process of cell replication

interphase- genetic material of chromosomes replicates

prophase- chromosomes coil and contract, consists of chromatids held together by centromeres, nuclear envelope disappears, the centriole divides, and the two centrioles move to opposite poles of the cell, spindle fibers develop

metaphase- chromatids line up t the center, spindle fibers attach to centromeres, the centromere replicate, separating the chromatids

anaphase-spindle fibers pull the new chromosomes to opposite poles of the cell

telophase-a nuclear membrane forms around each set of chromosomes, centrioles replica in each cell`
What has been associated with the calcification of dental tissues?
Mitochondria
4 types of tissue
epithelial
connective
muscle
nerve
epithelial cells
forms surface epithelium and glandular tissue

rest on underlying connective tissue, consists of cells and cell junctions

protection, absorption, secretion
classification of epithelial cells by shape
cuboidal, columnar, squamous
classification of epithelial cells by layers
one layer: simple

several layers: stratified
classification of epithelial cells by
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