Cells and Tissues

cells

are the structural units of all living things

plasma membrane

a fragile, transparent barrier that contains the cell contents and separates them from the surrounding environment

phospholipid bilayer

forms the basic “fabric” of the membrane

hydrophilic

“water loving” and are attracted to water

hydrophobic

“water fearing”, avoid water

nucleus

“headquarters,” or the control center of a cell

nucleoli

are sites where cell structures called ribosomes are assembled

cytoplasm

is the cellular material outside the nucleus and inside the plasma membrane

organelles

are specialized cellular compartments

Mitochondria

the “powerhouses” of the cell

Ribosomes

actual sites of protein synthesis in the cell

endoplasmic reticulum

is a system of fluid filled tunnels (or canals) that coil and twist through the cytoplasm

rough endoplasmic reticulum

it is studded with ribosomes

smooth endoplasmic reticulum

Plays no role in protein synthesis, because it lacks ribosomes. Instead it functions in lipid metabolism (cholesterol and phospholipid synthesis and breakdown) and detoxification of drugs and pesticides

Golgi Apparatus

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

Lysosomes

are membranous “bags” containing powerful digestive enzymes

Peroxisomes

are membranous sacs containing powerful oxidase enzymes that use molecular oxygen to detoxify a number of harmful or poisonous substances, including alcohol and formaldehyde

Cytoskeleton

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

Centrioles

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

Cilia

are whiplike cellular extensions that move substances along the cell surface

flagella

If the projections formed by the centrioles are substantially longer

Microvilli

are tiny, fingerlike extensions of the plasma membrane that project from an exposed cell surface

Mitosis

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

tissues

Groups of cells that are similar in structure and function

Epithelial tissue or epithelium

is the lining, covering, and glandular tissue of the body

Connective tissue

tissue that connects body parts

simple epithelium

one layer of cells

stratified epithelium

more than one cell layer

Simple squamous epithelium

is a single layer of thin squamous cells resting on a basement membrane. The cells fit closely together, much like floor tiles

Simple cuboidal epithelium

is common in glands and their associated small tubes called ducts (for example, the salivary glands and pancreas). It also forms the walls of the kidney tubules and covers the surface of the ovaries.

Simple columnar epithelium

is made up of a single layer of tall cells that fit closely together and whose nuclei appear to form a straight line

Pseudostratified Columnar Epithelium

some of its cells are shorter than others, and their nuclei appear at different heights above the basement membrane

Stratified squamous epithelium

is the most common stratified epithelium in the body

Stratified cuboidal epithelium

typically has just two cell layers with (at least) the surface cells being cuboidal in shape

stratified columnar epithelium

The surface cells are columnar cells, but its basal cells vary in size and shape.

Transitional epithelium

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

gland

consists of one or more cells that make and secrete a particular product

Endocrine glands

They are often called ductless glands. Their secretions (all hormones) diffuse directly into the blood vessels that weave through the glands

Exocrine glands

retain their ducts, and their secretions exit through the ducts to the epithelial surface

dense connective tissue

collagen fibers are the main matrix element, forms strong ropelike structures such as tendons and ligaments that withstand tension in one direction

loose connective tissues

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

Adipose tissue

commonly called fat

Reticular connective tissue

consists of a delicate network of interwoven reticular fibers associated with reticular cells, which resemble fibroblasts

Blood

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

Muscle tissues

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