1. Unit 2

2.  Cells are primarily made of 4 elements: ◦ Carbon, oxygen, hydrogen, and nitrogen ◦ Water (H 2 O is the most abundant substance  Also contain small amounts of other elements: ◦ Calcium for blood clotting ◦ Iron for hemoglobin, which carries oxygen in blood ◦ Iodine makes thyroid hormone that controls metabolism ◦ Metals (calcium, sodium, potassium, etc.) can carry electrical charge  electrolytes that are essential for nerve impulses

3.  In multicellular organisms, cells can be specialized to perform specific tasks  However, all cells are able to perform the following functions: ◦ Metabolism ◦ Reproduction ◦ Irritability ◦ Mobility ◦ Grow ◦ Digestion ◦ Excretion

4.  Cubelike  Tilelike  Disk-shaped  Round spheres  Branching  Cylindrical

5.  Surrounds all cells  Contains salt and other materials  similar to sea water

6.  A cell’s structure greatly impacts its function ◦ Neurons (nerve cells) have long processes for receiving and transmitting messages and are covered with an extensive plasma membrane. ◦ Fat cells are large and spherical due to a large lipid droplet in their cytoplasm. ◦ Squamous epithelial cells are flat and fit together like tiles in order to protect the body. ◦ Skeletal muscle cells are elongated and filled with contractile filaments to help facilitate mobility.

7. Cell StructureLocationFunction Plasma membraneExternal boundary of the cellConfines cell contents; regulates entry and exit of minerals LysosomesScattered in cytoplasmDigest ingested materials and worn-out organelles MitochondriaScattered throughout the cellControl release of energy from foods; form ATP MicrovilliProjections of the plasma membrane Increase the membrane surface area Golgi apparatusNear the nucleus (in the cytoplasm) Packages proteins to be incorporated into the plasma membrane or lysosomes or exported from the cell Nucleus(Usually) center of the cellStorehouse of genetic information; directs cellular activities, including division CentriolesTwo rod-shaped bodies near the nucleus Direct formation of the mitotic spindle

8. Cell StructureLocationFunction NucleolusDark spherical body in the nucleus Storehouse/assembly site for ribosomes Smooth ERIn the cytoplasmSite of steroid synthesis and lipid metabolism Rough ERIn the cytoplasmTransports proteins (made on its ribosomes) to other sites in the cell; synthesizes membrane lipids RibosomesAttached to membrane systems or scattered in the cytoplasm Synthesize proteins ChromatinDispersed in the nucleusContains genetic material (DNA); coils during mitosis PeroxisomesScattered in cytoplasmDetoxify alcohol, hydrogen peroxide, etc. InclusionsDispersed in the cytoplasmProvide nutrients; represent cell waste, stored products, etc.

10.  Cells come together to form tissues, joined at cell junctions  Types of junctions: ◦ Tight junctions – impermeable, bind cells into leak-proof sheets. Adjacent plasma membranes fuse together tightly like a zipper. ◦ Desmosomes – anchoring junctions that prevent cells from being pulled apart. Button-like thickenings of adjacent plasma membranes, which are connected by fine protein filaments. ◦ Gap junctions – allow communication, chemical molecules can pass from one cell to another, neighboring cells are connected by connexons, hollow cylinders composed of protein.

11.  Epithelial – lining, covering, glandular  Connective – connects body parts  Muscle – able to contract (shorten)  Nervous – conduct electrochemical impulses from one part of the body to another  irritability and conductivity

12.  Cells fit closely together to form continuous sheets  Neighboring cells are bound together at cell junctions  Membranes always have one free (unattached) edge = apical surface  exposed to exterior OR cavity of internal organ  Lower surface rests on basement membrane, a structureless material secreted by the cells  Don’t have a blood supply of their own  rely on diffusion from capillaries

13.  Named for cells at the free surface, not those at basement membrane ◦ Simple epithelium = one layer of cells ◦ Stratified epithelium = more than one cell layer ◦ Squamous cells = flattened ◦ Cuboidal = cube-shaped ◦ Columnar = shaped like columns

14.  Single layer of thin squamous cells resting on a basement membrane  Fit closely together, like floor tiles  Usually found where filtration occurs or where substances are exchanged through rapid diffusion  Example: Air sacs of lungs and walls of capillaries

15.  Single layer of cuboidal cells resting on a basement membrane  Common in glands and their ducts  Forms walls of kidney tubules and covers surface of ovaries

16.  Single layer of tall cells that fit closely together  Line the entire length of the digestive tract from stomach to anus

17.  All of the cells rest on a basement membrane, however, some appear shorter than others  False impression of stratification  Lines the respiratory tract

18.  Consists of several layers of squamous cells  Most common stratified epithelium in the body  Outer portion of skin, esophagus

19.  Usually only two layers of cells that are cuboidal or columnar in shape  Fairly rare in the body, found mainly in the ducts of large glands

20.  Highly modified, stratified squamous epithelium that forms the lining of only a few organs  Urinary bladder, ureters, part of urethra  all part of urinary system

21.  Glands make and secrete a particular product  Endocrine glands – “ductless” glands  secrete directly into blood stream  Exocrine glands – secrete through ducts to the epithelial surface

22.  Connects body parts  Most abundant and widely distributed of tissues  Most have a good blood supply, but there are some exceptions, such as tendons, ligaments, and cartilages  Extracellular matrix – nonliving substance found outside of the cells

23.  Osseous tissue  bone cells sitting in cavities called lacunae and surrounded by layers of a very hard matrix that contains calcium salts and collagen fibers  Very hard  protects and supports body

24.  Less hard and more flexible than bone  Hyaline cartilage = abundant collagen fibers hidden by a rubbery matrix; forms larynx, attaches ribs to sternum, and covers ends of bones where they form joints  Fibrocartilage = cushionlike discs between vertebrae of spinal column  Elastic cartilage = found where a structure with elasticity is desired, such as the external ear

25.  Collagen fibers = main matrix element  Fibroblasts = fiber-forming cells located between collagen fibers  Forms strong, ropelike structures such as tendons (attach skeletal muscles to bones) and ligaments (connect bones to bones)

26.  Softer, more cells, fewer fibers  Areolar tissue – cushions and protects body organs, helps hold them together and in place, acts as a sponge and soaks up excess fluid  Adipose tissue – “fat,” forms subcutaneous tissue beneath the skin, insulates body and protects some organs, acts as fuel if needed  Reticular connective tissue – delicate network of interwoven fibers that helps support many free blood cells in lymphoid organs

27.  Blood is considered a connective tissue because it consists of blood cells surrounded by a nonliving, fluid matrix called plasma  The “fibers” are soluble protein molecules visible during clotting  Carries nutrients, wastes, respiratory gases, and many other substances

28.  Specialized to contract, or shorten  Three types: ◦ Skeletal ◦ Cardiac ◦ Smooth

29.  Packaged by connective tissue sheets into organs called skeletal muscles  These muscles can be controlled voluntarily  When they contract, they pull on bones or skin  Cells are long, cylindrical, and multinucleate  Obvious striations (stripes)

30.  Found only in the heart  Has striations like skeletal muscle, but the cells only have one nucleus  Branching cells fit tightly together like clasped fingers at junctions called intercalated disks  Contain gap junctions that allow ions to pass freely from cell to cell, resulting in rapid conduction of the electrical impulses  Involuntary control

31.  No striations  Cells have a single nucleus and are spindle shaped  Found in the walls of hollow organs, such as the stomach, bladder, uterus, and blood vessels  Smooth muscle contractions help propel substances through an organ  Involuntary contractions

32.  Neurons – cells that receive and send electrochemical signals from one part of the body to another  Cytoplasm is drawn out into long extensions, which allows a single neuron to conduct an impulse over long distances