CHAPTER 5

TISSUE

used to describe a group of cells functioning together in the body

HISTOLOGY

The microscopic study of tissue appearance, organization, and function

PATHOLOGY

the changes that occur during the course of disease.

EPITHELIAL TISSUE

are sheets of cells that cover exterior surfaces of the body, line internal cavities and passageways, and form certain glands.

CONNECTIVE TISSUE

our most diverse category of tissue, binds the cells and organs of the body together and functions in the protection, support, and integration of all parts of the body.

MUSCLE TISSUE

is contractile; it provides movement, whether that means moving the skeleton, as in walking, or moving the blood through the body as the heart muscle contracts.

NERVOUS TISSUE

is capable of short- and long-distance communication throughout the body.

EXTRACELLULAR MATRIX (ECM)

is a network of substances that surround and support the cells in a tissue. ECM varies widely from one tissue to another in order to best support the functions of the tissue.

COLLAGEN

is the most abundant protein in the human body. ______ subunits are added together to create long, tough fibers that weave together to form the structure of the ECM. _______ can be thought of like leather—tough and protective, but flexible and allowing movement.

PROTEOGLYCANS

are large, negatively-charged molecules that are a combination of carbohydrate and protein. Their negative charge attracts Na+ and water molecules to the ECM.

-the ECM takes on a gel-like consistency.

Cellular Connections

The degree to which cells touch and interact varies from tissue to tissue. In locations where cells are close to each other they can often be connected.

TIGHT JUNCTION

which fuses the membranes of two neighboring cells together tightly so that there is no extracellular space between them, which blocks the movement of substances through the extracellular space between the cells.

DESMOSOMES and HEMIDESMOSOMES

are two types of anchoring junction, which are cell junctions that help stabilize cells structurally.

ANCHORING JUNCTIONS

provide strong and flexible connections.

DESMOSOMES

unite two neighboring cells structurally.

HEMIDESMOSOMES

which look like half a desmosome, link cells to the extracellular matrix.

GAP JUNCTIONS

forms an intercellular passageway between the membranes of adjacent cells to facilitate the movement of small molecules and ions among the cytoplasm of adjacent cells.

These junctions allow electrical and metabolic coupling of adjacent cells, which coordinates function in large groups of cells.

ENDOTHELIUM

For these “inside” structures, the epithelial tissue lining them is called ______ (plural = endothelia).

APICAL SIDE

is exposed to the external environment or an internal space

BASAL SURFACE

is the only side of the tissue facing the ECM.

BASEMENT MEMBRANE

The specialized ECM that supports and anchors the basal epithelium

LAMINA LUCIDA

a mixture of glycoproteins and collagen that provides the immediate attachment site for the epithelium

LAMINA DENSA

which has a denser and more structural weave of tough collagen fibers.

AVASCULAR

meaning that they have no

blood vessels.

LUMEN

In enclosed spaces that are lined with epithelia, the enclosed space is called a ______

EPITHELIAL CELLS

are polarized, in that their apical and basal membranes may have different surroundings, but also in the composition of their membranes and the distribution of organelles between their basal and apical surfaces. Whereas certain organelles are closer to the basal sides, other organelles are near the apical surface.

PSEUDOSTRATIFIED

(pseudo- = “false”) describes an epithelial tissue with a single layer of irregularly-shaped cells that give the appearance of more than one layer when sectioned for viewing under the microscope

TRANSITIONAL

describes a form of specialized stratified epithelium that is found in the urinary bladder. Because the tissue is very stretchy, the shape of the cells can vary depending on how the tissue is stretched

SIMPLE EPITHELIUM

The shape of the cells in the single cell layer of simple epithelium reflects the functioning of those cells.

SIMPLE SQUAMOUS EPITHELIUM

have the appearance of a fried egg. Squamous cell nuclei tend to be flat and horizontal, mirroring the form of the cell.

-because of the thinness of the cell, is present where rapid passage of chemical compounds is observed.

SIMPLE CUBOIDAL EPITHELIUM

• the nucleus of the boxlike cells appears round and is generally located near the center of the cell.

• are typically found in places of transport, such as in the lining of the ducts of glands.

SIMPLE COLUMNAR EPITHELIUM

• the nucleus of the tall column-like cells tends to be elongated and located in the basal end of the cells. This epithelium is typically active in the absorption and secretion of molecules.

• forms the lining of some sections of the digestive system and parts of the reproductive tract

PSEUDOSTRATIFIED COLUMNAR EPITHELIUM

• is a type of epithelium that appears to be stratified, but instead consists of a single layer of irregularly-shaped and differently-sized columnar cells.

• nuclei of neighboring cells appear at different levels rather than clustered in the basal end.

GOBLET CELLS

These mucus-secreting cells are technically unicellular exocrine glands interspersed between the columnar epithelial cells of mucous membranes

STRATIFIED EPITHELIUM

• consist of multiple stacked layers of cells.

• These types of epithelia are found in places where the apical surface is subject to more friction, and the multiple cell layers protect the underlying tissue from wear and tear.

STRATIFIED SQUAMOS EPITHELIUM

is by far the most common type of stratified epithelium in the human body.

TRANSITIONAL EPITHELIUM

is a specialized stratified epithelium found in the urinary bladder and the tubes that lead to it

GLAND

is a structure that synthesizes and secretes chemicals.

INSIDE

is a sterile place where no bacteria

are found

OUTSIDE

is those spaces continuous with the outside world, including the lining of the gut.

ENDOCRINE GLAND

if it secretes within the body and bloodstream,

EXOCRINE GLAND

• if it secretes onto an epithelium to the outside of the body

• release their contents through a duct that leads to the epithelial surface.

UNICELLULAR GLANDS

are single cells such as goblet cells scattered among the epithelial cells.

MULTICELLULAR GLANDS

consist of a single layer of epithelial cells that folds into the deeper tissues below.