4.1 Tissues & Histology + 4.2 Epithelial Tissue (+ Image Occlusion)

Tissues

________ are groups of specialized cells and the extracellular substances surrounding them.

Histology

_________ is the microscopic study of tissue structure.

epithelial, connective, muscle, nervous

The four primary tissue types, from which all organs of the body are formed, are (1) __________ tissue, (2) __________ tissue, (3) ______ tissue, and (4) _______ tissue.

Epithelium

__________ forms the layers that cover the surfaces and line the hollow organs of our body.

cells

Epithelial tissue consists almost entirely of _____, with very little extracellular matrix between them.

body surfaces

Epithelial tissue covers _____________ and forms glands that are derived developmentally from _____________.

outside environment, hollow organs

Because epithelial tissues form coverings and linings, one surface of their cells is in direct contact with either the ___________________ or the contents of our _____________.

free surface

The surface that is exposed is called the ____________, or apical (A-pi-kal) surface.

basal surface

The surface of the cells that is anchored in place is called the _____________.

basement membrane

The basal surface is held in place through attachment to a nonliving material that is somewhat like mortar for brick. This material is called the _________________ and is composed of specialized extracellular material secreted by the epithelial cells.

lateral surface

Between the epithelial cells is the _______________, where the epithelial cells are attached to each other.

specialized cell connections

Adjacent epithelial cells are attached to each other by __________________________ and they are specially anchored to the extracellular matrix of the basement membrane.

blood vessels

Because of the close connections among the epithelial cells, there are no _____________ found among the epithelial cells.

diffuse

In fact, the blood vessels don't penetrate the basement membrane. Instead, they lie just underneath the basement membrane, and nutrients and gases _______ out of the blood toward the epithelial cells.

closest

Thus, the most metabolically active cells are _______ to the basement membrane.

replace

Epithelial tissue has the ability to _______ damaged cells with new epithelial cells.

stem cells

Undifferentiated cells (__________) continuously divide and produce new cells.

underlying structures

Epithelia protects _____________________

moving through it (prevents)

Epithelium prevents many substances from _________________

move through it (allows)

Epithelium also allows many substances to _______________

secrets substances

Epithelia _________________, such as in sweat glands, mucous glands, and the enzyme-secreting portion of the pancreas

carrier proteins

The cell membranes of certain epithelial tissues contain ________________ that regulate the absorption of materials

number (classification), shape

Epithelial tissues are classified primarily according to the ______ of cell layers and the _____ of the superficial cells.

Simple

______ epithelium consists of a single layer of cells, with each cell extending from the basement membrane to the free surface.

Stratified

__________ epithelium consists of more than one layer of cells, but only the deepest layer of cells attaches to the basement membrane.

Pseudostratified columnar

_______________________ epithelium appears to be statified, but consists of one layer of cells all attached to the basement membrane

Squamous

________ cells are flat or scalelike

Cuboidal

________ cells are cube-shaped, about as wide as they are tall

Columnar

________ cells tend to be taller than they are wide

number (naming), shape (naming)

An epithelium is typically given two names, the first indicating the ______ of layers and the second indicating the _____

Simple squamous (description)

________________ epithelium is a single layer of thin, flat cells. Some substances easily pass through this thin layer of cells, but other substances do not.

Simple cuboidal (description)

_______________ epithelium is a single layer of cubelike cells that carry out active transport, facilitated diffusion, or secretion.

Simple columnar (description)

________________ epithelium is a single layer of tall, thin cells. The large size of these cells enables them to perform complex functions.

Stratified squamous (description)

___________________ epithelium forms a thick epithelium because it consists of several layers of cells

Transitional

____________ epithelium (also called urothelium) is a special type of stratified epithelium that can stretch

five or more, flatten

In the unstretched state, transitional epithelium consists of ____________ layers of cuboidal or columnar cells. As transitional epithelium is stretched, the cells _______, and the number of cell layers decreases.

urinary bladder

Transitional epithelium lines structures in the urinary system that expand, such as the _______________.

Simple squamous (function)

________________ epithelium is best adapted for areas of the body where filtration and diffusion are common.

Simple cuboidal (function)

_______________ epithelium, due to the larger volume of these cells, has a greater secretory capacity than simple squamous epithelium.

Simple columnar (comparison)

________________ epithelial cells are much taller than those of cuboidal epithelium.

Stratified squamous (barrier)

___________________ epithelium forms a thick barrier, which can be as many as 30-40 cells thick.

free surfaces

The _____________ of epithelial tissues are not in contact with other cells and can be smooth or folded.

endothelium

Smooth free surfaces reduce friction; an example of such a surface is the tissue lining blood vessels. This kind of tissue is a specialized type of simple squamous epithelium called ___________

Folded

______ free surfaces have increased surface area.

desmosomes

Cell connection structures that mechanically bind epithelial cells together are called __________

hemidesmosomes

Cell connection structures that bind cells to the basement membrane are called ______________

Tight junctions

_______________ are cell connection structures that (1) form barriers and (2) anchor cells to each other.

adhesion belts

Structures called ______________ are found just below the tight junctions and help the tight junctions anchor the epithelial cells to each other.

gap junctions

Cell connection structures that allow for intercellular communication include ____________.

Glands

______ are composed of epithelium supported by a network of connective tissue.

endocrine, exocrine

There are two major types of glands in the body, _________ and ________ glands.

Endocrine (definition)

_________ glands produce chemicals called hormones and are often termed ductless glands based on their structure and mode of secretion.

blood vessels, blood

Endocrine glands are associated with an extensive network of _____________, and their hormones are transported throughout the body by way of the _____.

Exocrine

________ glands produce a wide variety of products, such as saliva, sweat, and digestive tract secretions.

ducts

Exocrine gland secretions enter _____, which are continuous with the epithelial tissue surface. At the appropriate location, the secretions exit onto the free surface of the target organ's tissue.

structure, secretion

Exocrine glands are primarily categorized on the basis of their _________, but they are also separated on the basis of their mode of _________

duct

The ____ refers to the tube in contact with the epithelial tissue free surface, which transports the secreted material.

secretory

The __________ portion of the gland is found deeper in the epithelium and is composed of the cells responsible for producing the secreted material.

unicellular, simple, compound

The three major categories of exocrine glands are ___________, ______, and ________

goblet cells

Some exocrine glands are composed of only a single cell, such as ____________ that secret mucus

Simple (gland type)

______ glands are multicellular glands that have a single, nonbranched duct

tubular, acinar

The secretory portions of the gland can be shaped in one of two ways: (1) _______, which is a straight, narrow tube the same width as the duct, or (2) ______, a saclike structure whose width is greater than the width of the duct.

Compound

________ glands are multicellular glands that have several branched ducts.

Merocrine

_________ secretion is the release of secretory products through exocytosis and is the most common.

Apocrine

________ secretion is the release of secretory products when a portion of the free surface of the epithelial cell pinches off, releasing cytoplasmic contents. The remainder of the cell is repaired.

Holocrine

_________ secretion is the release of secretory products through shedding of entire cells. Once the secretory products have accumulated in the epithelial cell, the cell disintegrates and becomes part of the secretion. Deeper cells in the gland replace lost cells.