Cells And Tissues Wrong

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Are the structural units of all living things, from one-celled organisms such as amoebas to complex multicellular organisms such as humans, animals, and plants.

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cells

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4 concepts of the cell theory:

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• A cell is the basic structural and functional unit of living organisms. • The activity of an organism depends on the collective activities of its cells. • According to the principle of complementarity, the activities of cells are dictated by their structure (anatomy), which determines function (physiology). • Continuity of life has a cellular basis.

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3 main regions or parts

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a nucleus (nu′kle-us), a plasma membrane, and the cytoplasm (si′to-plazm″).

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It is the “headquarters,” or the control center of all cells.

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The Nucleus

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the nuclear envelope allows some but not all substances to pass through it, but substances pass through it much more freely than elsewhere because of its relatively large

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Nuclear envelope

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encloses a jellylike fluid called nucleoplasm (nu′kle-o-plazm″) in which other nuclear elements are suspended.

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Nuclear membrane

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The nucleus contains one or more small, dark staining, essentially round bodies called (nu-kle′o-li; “little nuclei”).

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Nucleoli

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It is formed when a cell is not dividing, its DNA is carefully wound around proteins called histones to form a loose network of “beads on a string”.

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Chromatin

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It is a fragile, transparent barrier that contains the cell contents and separates them from the surrounding environment. Its unique structure allows it to play a dynamic role in many cellular activities

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The Plasma Membrane

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The structure of the plasma membrane consists of two

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phospholipid (fat) layers arranged “tail to tail,” with cholesterol and floating proteins scattered among them.

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The proteins, some of which are free to move and bob in the lipid layer, form a constantly changing pattern or mosaic, hence the name of the model that describes the plasma membrane.

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Fluid Mosaic Model

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in the glycocalyx act as an adhesive or cellular glue

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Glycoproteins

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Cells are bound together in three ways:

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• Glycoproteins in the glycocalyx act as an adhesive or cellular glue. • Wavy contours of the membranes of adjacent cells fit together in a tongue-and-groove fashion

• Special cell membrane junctions are formed. These junctions vary structurally depending on their roles.

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Types of Cell Junctions:

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Tight junctions, Desmosomes, Gap Junctions

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are impermeable junctions that encircle the cells and bind them together into leakproof sheets.

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Tight junctions

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Are anchoring junctions scattered like rivets along the sides of adjacent cells

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Desmosomes

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communicating junctions. These junctions are commonly found in the heart and between embryonic cells.

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Gap Junctions

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is the cellular material outside the nucleus and inside the plasma membrane. ^It is the site of most cellular activities, it is the “factory floor” of the cell.

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The Cytoplasm

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Three Major Components:

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Cytosol, Inclusion, Organelles

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Is semitransparent fluid that suspends the other elements. Dissolved in the cytosol, which is largely water, are nutrients and a variety of other solutes (sol′yuˉ tz; dissolved substances).

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Cytosol

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Chemical substances that may or may not be present, depending on the specific cell type. Most inclusions are stored nutrients or cell products floating in the cytosol. It acts as a cellular “storage” where items are kept on hand until needed.

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Inclusion

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(or″gah-nelz′) “little organs”. Each type of organelle is specialized to carry out a specific function for the cell as a whole, much like the organs carry out specialized functions for the whole body.

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Organelles

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smooth endoplasmic reticulum, ribosome, lysoome, rough endoplasmic reticulum, mitochondrion, centrioles, peroxisome, golgi apparatus

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They are the “powerhouses” of the cell because it supplies most of the ATP. Cells, such as liver and muscle cells, use huge amounts of ATP and have hundreds of mitochondria.

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Mitochondria

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Are tiny, bilobed, dark bodies made of proteins and one variety of RNA called ribosomal RNA. Ribosomes are the actual sites of protein synthesis in the cell.

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Ribosomes

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Is a system of fluid-filled tunnels (or canals) that coil and twist through the cytoplasm. It is continuous with the nuclear envelope and accounts for about half of a ce ll’s membranes. It serves as a mini circulatory system for the cell because it provides a network of channels for carrying substances (primarily proteins) from one part of the cell to another

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Endoplasmic Reticulum

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2 Forms of Endoplasmic Reticulum

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Rough endoplasmic reticulum, Smooth endoplasmic reticulum

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All building materials of cellular membranes are formed either in it or on it. It is especially abundant in cells that make (synthesize) and export (secrete) proteins.

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Rough endoplasmic reticulum

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It communicates with the rough ER, but it plays no role in protein synthesis, because it lacks ribosomes. ^Instead, it functions in lipid metabolism (cholesterol and fat synthesis and breakdown) and detoxification of drugs and pesticides.

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Smooth endoplasmic reticulum

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It appears as a stack of flattened membranous sacs that are associated with swarms of tiny vesicles. It is generally found close to the ER and is the principal “traffic director” for cellular proteins. Its major function is to modify, package, and ship proteins (sent to it by the rough ER via transport vesicles) in specific ways, depending on their final destination.

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Golgi Apparatus

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Are membranous “bags” containing powerful digestive enzymes. It functions as cellular “stomachs.” Lysosomes are especially abundant in white blood cells called phagocytes, the cells that dispose of bacteria and cell debris.

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Lysosomes

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Are membranous sacs containing powerful oxidase (ok′s˘ı-dˉaz) enzymes that use molecular oxygen (O2) to detoxify a number of harmful or poisonous substances, including alcohol and formaldehyde. Their most important function is to “disarm” dangerous free radicals. Peroxisomes are especially numerous in liver and kidney cells, which are very active in detoxification

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Peroxisomes

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Are best known for their role in generating microtubules and also, for directing the formation of the mitotic spindle during cell division.

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Centrioles

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cell extentions parts

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cilia and flagella

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An elaborate network of protein structures extends throughout the cytoplasm. It acts as a cell’s “bones and muscles” by furnishing an internal framework that determines cell shape, supports other organelles, and provides the machinery for intracellular transport and various types of cellular movements.

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Cytoskeleton

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Are whiplike cellular extensions that move substances along the cell surface

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Cilia

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The projections formed by the centrioles are substantially longer. The only example of a flagellated cell in the human body is the sperm, which has a single propulsive flagellum called its tail.

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Flagella

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Cells that connect body parts

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Fibroblast, Erythrocyte (red blood cell)

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This cell has an elongated shape, like the cable-like fibers that it secretes. It has an abundant rough ER and a large Golgi apparatus to make and secrete the protein building blocks of these fibers.

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Fibroblast

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This cell carries oxygen in the blood. Its biconcave disc shape provides extra surface area for the uptake of oxygen and the cell, so it flows easily through the bloodstream.

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Erythrocyte (red blood cell)

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Cells that cover and line the body organs

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Epithelial cells

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The hexagonal shape of this cell is exactly like a “cell” in a honeycomb of a beehive. This shape allows epithelial cells to pack together in sheets.

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Epithelial cells

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Cells that move organs and body parts

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Skeletal, cardiac, and smooth muscle cells

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These cells are elongated and filled with abundant contractile filaments, so they can shorten forcefully and move the bones, pump blood, or change the size of internal organs to move substances around the body.

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Skeletal, cardiac, and smooth muscle cells

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Cells that stores nutrient

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Fat cells

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The huge spherical shape of a fat cell is produced by a large lipid droplet in its cytoplasm.

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Fat cells

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Cells that fight diseases

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White blood cells/macrophage

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This cell extends long pseudopods (“false feet”) to crawl through tissue to reach infection sites. The many lysosomes within the cell digest the infectious microorganisms (such as bacteria) that it “eats.”

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White blood cells/macrophage

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Cells that gather information and controls body functions.

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Nerve cell (neuron)

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This cell has long processes (extensions) for receiving messages and transmitting them to other structures in the body. The processes are covered with an extensive plasma membrane, and a plentiful rough ER synthesizes membrane components and signaling molecules called neurotransmitters

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Nerve cell (neuron)

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Cells of Reproduction

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Oocyte (female), Sperm (male)

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The largest cell in the body, this egg cell contains several copies of all organelles, for distribution to the daughter cells that arise when the fertilized egg divides to become an embryo

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Oocyte (female)

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This cell is long and streamlined, built for swimming to the egg for fertilization. Its flagellum acts as a motile whip to propel the sperm.

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Sperm (male)

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Most cells have the ability to metabolize (use nutrients to build new cell material, break down substances, and make ATP), digest foods, dispose of wastes, reproduce, grow, move, and respond to a stimulus (irritability).

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Cell Physiology

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The plasma membrane is a selectively permeable barrier. Selective permeability means that a barrier allows some substances to pass through it while excluding others. Thus, it allows nutrients to enter the cell but keeps many undesirable or unnecessary substances out.

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Membrane Transport

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The fluid environment on both sides of the plasma membrane is an example of a

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solution

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Components or substances present in smaller amounts are called

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solutes

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(collectively, the nucleoplasm and the cytosol) is a solution containing small amounts of gases (oxygen and carbon dioxide), nutrients, and salts, dissolved in water.

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Intracellular fluid

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the fluid that continuously bathes the exterior of our cells.

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Extracellular fluid - or interstitial fluid

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3 types of solutions

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Isotonic, hypertonic, hypotonic

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solutions (such as 5 percent glucose and 0.9 percent saline) have the same solute and water concentrations as cells do. Isotonic solutions cause no visible changes in cells, and when such solutions are infused into the bloodstream, red blood cells (RBCs) retain their normal size and disclike shape.

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Isotonic (i″so-ton′ik - “same tonicity”)

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a solution that contains more solutes, or dissolved substances, than there are inside the cells—the cells begin to shrink. This is because water is in higher conc

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hypertonic (hi″per-ton′ik) solution

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When a solution contains fewer solutes (and therefore more water) than the cell does, it is

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hypotonic (hi″po-ton′ik)

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is the process by which molecules (and ions) move away from areas where they are more concentrated (more numerous) to areas where they are less concentrated (with fewer of them).

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Diffusion

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is the process by which water and solutes are forced through a membrane (or capillary wall) by fluid, or hydrostatic, pressure.

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Filtration

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Osmosis into and out of cells is occurring all the time as water moves down its concentration gradient. The movement of water across the membrane occurs quickly. Anyone administering an IV (intravenous, into the vein) solution must use the correct solution to protect the patient’s cells from lifethreatening dehydration or rupture.

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Osmosis

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2 most important active processes:

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Passive Processes, Active Processes

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substances are transported across the membrane without any energy input from the cell.

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Passive Processes

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the cell providesthe metabolic energy (ATP) that drivesthe transport process

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Active Processes

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t require protein carriers that interact specifically and reversibly with the substances to be transported across the membrane

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Active transport

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pump alternately carries sodium ions (Na+) out of and potassium ions (K+) into the cell. It uses ATP to energize its protein carriers, which are called solute pumps.

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sodium-potassium (Na+-K+)

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It involves help from ATP to fuse or separate membrane vesicles and the cell membrane, moves substances into or out of cells “in bulk” without their actually crossing the plasma membrane directly.

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Vesicular transport

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is the mechanism that cells use to actively secrete hormones, mucus, and other cell products or to eject certain cellular wastes

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Exocytosis

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Includes those ATP-requiring processes that take up, or engulf, extracellular substances by enclosing them in a vehicle.

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Endocytosis

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The function of cell division is to produce more cells for growth and repair processes

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Cell Division

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is the process of dividing a nucleusinto two daughter nuclei with exactly the same genes as the “mother” nucleus.

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Mitosis

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in which the cell grows and carries on its usual metabolic activities.

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Interphase

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The centrioles separate from each other and begin to move toward opposite sides of the cell, directing the assembly of a mitotic spindle (composed of microtubules) between them as they move.

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Prophase

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In this short stage, the chromosomes line up at the metaphase plate (the center of the spindle midway between the centrioles) so that a straight line of chromosomes is seen.

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Metaphase

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During anaphase, the centromeres that have held the chromatids together split. This careful division of sister chromatids ensures that each daughter cell gets one copy of every chromosome.

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Anaphase

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Telophase is essentially prophase in reverse. The chromosomes at opposite ends of the cell uncoil to become threadlike chromatin again. The spindle breaks down and disappears, a nuclear envelope forms around each chromatin mass, and nucleoli appear in each of the daughter nuclei.

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Telophase

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the division of the cytoplasm, usually begins during late anaphase and completes during telophase.

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Cytokinesis

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Groups of cells that are similar in structure and function.

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Tissues

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4 primary tissue types

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epithelial (covering), Connective (support), nervous (control), and muscle tissues (movement).

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Epithelial Tissue:

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• Epithelial cells fit closely together to form continuous sheets. • The membranes always have one free (unattached) surface or edge. • The anchored (basal) surface of epithelium rests on a basement membrane, a structureless material secreted by both the epithelial cells and the connective tissue cells deep to the epithelium. • Epithelial tissues have no blood supply of their own (that is, they are avascular) and depend on diffusion from the capillaries in the underlying connective tissue for food and oxygen. • If well nourished, epithelial cells regenerate easily

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Classification of Epithelia:

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Simple Epithelia, Simple Columnar epithelium, Stratified Epithelia

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The simple epithelia are most concerned with absorption, secretion, and filtration. Because simple epithelia are usually very thin, protection is not one of their specialties.

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Simple Epithelia

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is made up of a single layer of tall cells that fit closely together. Goblet cells [intestinal mucosal epithelial cells that serve as the primary site for nutrient digestion and mucosal absorption], which produce a lubricating mucus.

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Simple Columnar epithelium

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Stratified epithelia consist of two or more cell layers. Being considerably more durable than the simple epithelia, these epithelia function primarily in protection.

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Stratified Epithelia

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This type of epithelium usually forms membranes where filtration or exchange of substances by rapid diffusion occurs. (i.e., air sacs of the lungs (called alveoli), walls of capillaries, and the interstitial fluid.

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Simple Squamous epithelium

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common in glands and their associated small tubes called ducts(i.e., the salivary glands, pancreas, walls of the kidney tubules, and covers the surface of the ovaries.).

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Simple Cuboidal epithelium

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- is the most common stratified epithelium in the body. It usually consists of many cell layers.

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Stratified Squamous epithelium

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Both of these epithelia are fairly rare in the body, found mainly in the ducts of large glands.

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Stratified Cuboidal and Stratified Columnar epithelium

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is a highly modified, stratified squamous epithelium that forms the lining of only a few organs—the urinary bladder, the ureters, and part of the urethra.

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Transitional epithelium

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All of its cells rest on a basement membrane but some of its cells are shorter than others, and their nuclei appear at different heights above the basement membrane.

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Pseudostratified Columnar epithelium

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A gland consists of one or more cells that make and secrete a particular product. A secretion typically contains protein molecules in an aqueous (water-based) fluid

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Glandular epithelium

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often called ductless glands. Their secretions (all hormones) diffuse directly into the blood vessels that weave through the glands. Examples of endocrine glands include the thyroid, adrenals, and pituitary

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Endocrine

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retain their ducts, and their secretions exit through the ducts to the epithelial surface. Exocrine glands, which include the sweat and oil glands, liver, and pancreas, are both internal and external.

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Exocrine

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perform many functions, but they are primarily involved in protecting, supporting, and binding together other body tissues.

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Connective Tissue

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sometimes called osseous (os′e-us) tissue, is composed of osteocytes (os′te-o-sıˉtz; bone cells) sitting in cavities called lacunae (lah-ku′ne; “pits”).

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Bone

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Most widespread is hyaline (hi′ah-lin) cartilage, which has abundant collagen fibers hidden by a rubbery matrix with a glassy (hyalin = glass), blue-white appearance. It forms the trachea, or windpipe, attaches the ribs to the breastbone, and covers bone ends at joints.

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Cartilage

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Dense connective tissue forms strong, ropelike structures such as tendons and ligaments. Tendons attach skeletal muscles to bones; ligaments connect bones to bones at joints.

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Dense Connective tissue

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Are softer and have more cells and fewer fibers than any other connective tissue type except blood.

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Loose Connective tissue

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also protects some organs individually—the kidneys are surrounded by a capsule of fat, and adipose tissue cushions the eyeballs in their sockets.

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Adipose tissue

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or vascular tissue. Is considered a connective tissue because it consists of blood cells surrounded by a nonliving, fluid matrix called blood plasma

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Blood

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are highly specialized to contract, or shorten, which generates the force required produce movement.

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Muscle Tissue

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is found only in the heart wall.

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Cardiac Muscles

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tissue is packaged by connective tissue sheets into organs called skeletal muscles, which are attached to the skeleton.

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Skeletal Muscles

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Smooth muscle is found in the walls of hollow organs such as the stomach, uterus, and blood vessels.

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Smooth Muscles

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All neurons receive and conduct electrochemical impulses from one part of the body to another; thus, irritability and conductivity are their two major functional characteristics

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Nervous Tissue

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When tissue injury does occur, it stimulates the body’s inflammatory and immune responses, and the healing process begins almost immediately.

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Tissue Repair (Wound Healing)

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is a general (nonspecific) body response that attempts to prevent further injury.

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Inflammation

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in contrast, is extremely specific and mounts a vigorous attack against recognized invaders, including bacteria, viruses, and toxins

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The immune response