Ch. 4 The Tissue Levels of Organization Flashcards
What is a tissue?
a group of cells that usually have a common origin in an embryo and function together to carry out specialized activities
Histology is
the science that deals with the study of tissues
Pathologist
a physician who examines cells and tissues to help other physicians make accurate diagnoses; they also examine the tissue for any changes that might indicate a disease
Biopsy
the removal of a sample of living tissue for microscopic examination; it is used to help diagnose disorders and discover the cause of unexplained infections and inflammations, especially cancer
The 4 basic tissue types are
Nervous, Epithelial, Connective, and Muscular
Nervous Tissue
detects changes inside and outside of the body and responds by producing electrical signals (action potentials>nerve impulses) that activate muscular contractions and glandular secretions
Epithelial Tissue
covers the body surface and lines body cavities, hollow organs, and ducts; also form glands
Connective Tissue
Protects and supports the body and its organs by binding organs together; storing energy reserves as fat; and helping to provide the body with immunity to disease-causing organisms
Muscular Tissue
composed of specialized cells for contraction and generation of force (movement); generates heat
The tissues of the body develop from 3 primary germ layers:
Endoderm, Mesoderm, and Ectoderm
- Epithelial tissues arise from ALL 3
- C.T. and Muscular tissue from mesoderm
- Nervous tissue from ectoderm
Cell Junctions are
points of contact between the plasma membranes of tissue cells
Cell junctions have 3 functions
- Form fluid-tight seals between cells
- Anchor cells together or to extracellular material
- Act as channels (which allow ions to and molecules to pass from cell to cell within a tissue)
There are 5 different types of cell junctions
tight junctions, adhering junctions, desmosomes, hemidesmosomes, and gap junctions
Tight Junctions
weblike strands of transmembrane proteins that fuse together the outer surfaces of adjacent plasma membranes to seal off passageways between adjacent cells
-These seals are common among epithelial cells that line the stomach, intestines, and urinary bladder
Adhering Junctions
a dense layer of proteins on the inside of the plasma membrane that attaches both to membrane proteins and to microfilaments of the cytoskeleton
- These junctions are made up of plaque and anchor cells together
- transmembrane glycoproteins called Caderins join the cells (it forms the belt-like plaque)
Function: They help epithelia surfaces resist separation during various contractile activities like when food moves through the intestines
Desmosomes
Contain plaque and have transmembrane glycoproteins (cadherins) that extend into the intercellular space between adjacent cell membranes and attach cells to one another; link cytoskeletons of cells together
- unlike adhering junctions, the plaque of desmosomes does NOT attach to microfilaments
They are common among cells that make up the epidermis and cardiac muscle cells in the heart ; prevent them from separating under tension and cardiac muscle cells from pulling apart during contraction
Hemidesmosomes
They connect cells to extracellular material such as the basement membrane. On the inside, integrins (transmembrane glycoproteins) attach to the protein keratin and on the outside the integrins attach to the protein called laminin
Gap Junctions
allow cells in a tissue to rapidly communicate through connexons (a transmembrane protein channel that connects cells together)
Ions and small molecules can diffuse through the cystol of one cell to another, but not large molecules
They are present in areas such as the nervous system, contraction of muscles in the heart, gastrointestinal tract, and uterus. They are also present in a developing embryo
Comparison of Epithelial Tissue and Connective Tissue
- ET and CT differ in the number of cells in relation to the extracellular matrix (substance between the cells)
2. ET has no blood vessels, unlike CT
3. ET almost always forms surface layers and is not covered by another tissue (with exception of the epithelial lining of blood vessels where blood constantly passes over the epithelium)
Why are epithelial and connective tissues found adjacent to each other?
because ET lacks blood vessels and forms surfaces, it is always found immediately adjacent to blood vessel-rich CT, which enables it to make exchanges with blood necessary for the delivery of oxygen and nutrients and the removal of wastes that are critical processes for its survival and function
