Ch. 4 The Tissue Levels of Organization

Question 1

What is a tissue?

Answer 1

a group of cells that usually have a common origin in an embryo and function together to carry out specialized activities

Question 2

Histology is

Answer 2

the science that deals with the study of tissues

Question 3

Pathologist

Answer 3

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

Question 4

Biopsy

Answer 4

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

Question 5

The 4 basic tissue types are

Answer 5

Nervous, Epithelial, Connective, and Muscular

Question 6

Nervous Tissue

Answer 6

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

Question 7

Epithelial Tissue

Answer 7

covers the body surface and lines body cavities, hollow organs, and ducts; also form glands

Question 8

Connective Tissue

Answer 8

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

Question 9

Muscular Tissue

Answer 9

composed of specialized cells for contraction and generation of force (movement); generates heat

Question 10

The tissues of the body develop from 3 primary germ layers:

Answer 10

Endoderm, Mesoderm, and Ectoderm

• Epithelial tissues arise from ALL 3
• C.T. and Muscular tissue from mesoderm
• Nervous tissue from ectoderm

Question 11

Cell Junctions are

Answer 11

points of contact between the plasma membranes of tissue cells

Question 12

Cell junctions have 3 functions

Answer 12

1. Form fluid-tight seals between cells
2. Anchor cells together or to extracellular material
3. Act as channels (which allow ions to and molecules to pass from cell to cell within a tissue)

Question 13

There are 5 different types of cell junctions

Answer 13

tight junctions, adhering junctions, desmosomes, hemidesmosomes, and gap junctions

Question 14

Tight Junctions

Answer 14

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

Question 15

Adhering Junctions

Answer 15

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

Question 16

Desmosomes

Answer 16

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

Question 17

Hemidesmosomes

Answer 17

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

Question 18

Gap Junctions

Answer 18

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

Question 19

Comparison of Epithelial Tissue and Connective Tissue

Answer 19

• 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)

Question 20

Why are epithelial and connective tissues found adjacent to each other?

Answer 20

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