ap chap 4

tissues

tissues

are groups of specialized cells and the extracellular substances surrounding them

histology

is the microscopic study of tissue structure

1. epithelial tissue

2. connective tissue

3. muscle tissue

4. nervous tissue

four primary tissue types;

epithelium

• is found virtually everywhere, both inside and outside the body.

• It is primarily a cellular tissue, meaning there is very little extracellular material between the cells.

• It forms the layers that cover the surfaces and line the hollow organs of our body

1. Mostly composed of cells

2. Covers body surfaces

3. Has an exposed surface

4. Attaches at the basal surface

5. Has specialized cell connections and matrix attachments

6. Is avascular

7. Is capable of regeneration

characteristics common to most types of epithelial tissue

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.

• It plays an important role in supporting and guiding cell migration during tissue repair.

lateral surface

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

1. Protecting underlying structures

2. Acting as a barrier

3. Permitting the passage of substances

4. Secreting substances

5. Absorbing substances.

The major functions of epithelia are

1. Simple epithelium

2. Stratified epithelium

3. Pseudostratified columnar epithelium

three major types of epithelium based on the number of cell layers

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

• this type of epithelium appears to be stratified but is not.

• It consists of one layer of cells, with all the cells attached to the basement membrane.

• There appear to be two or more layers of cells because some of the cells are tall and extend to the free surface, whereas others are shorter and do not extend to the free surface

1. squamous

2. cuboidal

3. columnar

three types of epithelium based on idealized shapes of the epithelial cells

squamous

cells are flat or scalelike

cuboidal

are cube-shaped—- about as wide as they are tall

columnar

cells tend to be taller than they are wide

Simple Squamous Epithelium’s structure

Single layer of flat, often hexagonal cells; the nuclei appear as bumps when viewed in cross section because the cells are so flat

simple squamous epithelium’s function

Diffusion, filtration, some secretion, and some protection against friction

simple squamous epithelium’s location

• Lining of blood vessels and the heart

• lymphatic vessels

• alveoli of the lungs

• portions of the kidney tubules

• lining of serous membranes of body cavities (pleural, pericardial, peritoneal)

simple cuboidal epithelium’s structure

single layer of cube-shaped cells; some cells have microvilli (kidney tubules) or cilia (terminal bronchioles of the lungs)

simple cuboidal epithelium’s function

secretion and absorption by cells of the kidney tubules; secretion by cells of glands and choroid plexuses; movement of particles embedded in mucus out of the terminal bronchioles by ciliated cells

simple cuboidal epithelium’s location

kidney tubules, glands and their ducts, choroid plexuses of the brain, lining of terminal bronchioles of the lungs, and surfaces of the ovaries

simple columnar epithelium’s structure

single layer of tall, narrow cells; some cells have cilia (bronchioles of lungs, auditory tubes, uterine tubes, and uterus) or microvilli (intestines)

simple columnar epithelium’s function

movement of particles out of the bronchioles of the lungs by ciliated cells; partially responsible for the movement of oocytes through the uterine tubes by ciliated cells; secretion by cells of the glands, the stomach, and the intestines; absorption by cells of the intestines

simple columnar epithelium’s location

glands and some ducts bronchioles of lungs, auditory, uterus, uterine tubes, stomach, intestines, gallbladder, bile ducts, and ventricles of the brain

pseudostratified columnar epithelium’s structure

• single layer of cells; some cells are tall and thin and reach the free surface, and others do not

• the nuclei of these cells are at different levels and appear stratified

• the cells are almost always ciliated and associated with goblet cells that secrete mucus onto the free surface

pseudostratified columnar epithelium’s function

synthesize and secrete mucus onto the free surface and move mucus that contains foreign particles over the surface of the free surface and from passages

pseudostratified columnar epithelium’s location

lining of nasal cavity, nasal sinuses, auditory tubes, pharynx, trachea, and bronchi of lungs

stratified squamous epithelium’s structure

• several layers of cells that are cuboidal in basal layer and progressively flattened toward the surface

• can be nonkeratinized or keratinized

nonkeratinized stratified squamous epithelium

the surface cells retain a nucleus and cytoplasm

keratinized stratified squamous epithelium

the cytoplasm of cells at the surface is replaced by a protein called keratin, and cells are dead

stratified squamous epithelium’s function

protects against abrasion, forms a barrier against infection, and reduces loss of water from the body

stratified squamous epithelium’s location

• keratinized— outer layer of the skin

• nonkeratinized— mouth, throat, larynx, esophagus, anus, vagina, inferior urethra, and corneas

transitional epithelium’s structure

stratified cells that appear cuboidal when the organ or tube is not stretched and squamous when the organ or tube is stretched by fluid

transitional epithelium’s function

accommodates fluctuations in the volume of fluid in an organ or a tube; protects against the caustic effects of urine

transitional epithelium’s location

lining of urinary bladder, ureters, and superior urethra

free surfaces of epithelial tissues

— are not in contact with other cells and can be smooth or folded. They may also have microvilli or cilia

smooth free surfaces

reduce friction; an example of such a surface is the tissue lining blood vessels.

endothelium

(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

microvilli

are stationary and are found in cells that absorb or secrete, such as the lining of the small intestine

cilia

• are not stationary—instead they can move, which allows them to remove from the respiratory airways mucus that contains foreign particles

• are also found on the free surfaces of the simple columnar epithelial cells of the uterus and uterine tubes, where the — help move mucus and oocytes

desmosomes

• Cell connection structures that mechanically bind epithelial cells together are called —

• — are found in epithelial tissues subjected to mechanical stress, such as the stratified squamous epithelium of the skin

hemidesmosomes

• while those that bind cells to the basement membrane are called —

• — are the anchors of epithelial tissues to the underlying basement membrane, preventing the movement of the tissue.

tight junctions

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

• — form a barrier to movement of molecules or ions between epithelial cells. In addition, — anchor cells together

adhesion belts

• Structures called — are found just below the tight junctions, and help the tight junctions anchor the epithelial cells to each other

• provides additional strength for the binding of cells together at locations of tight junctions

gap junctions

• Cell connection structures that allow for intercellular communication include —

• — consist of groups of channels that allow small molecules and ions to pass from one epithelial cell to an adjacent one.

• may coordinate movement of the cilia.

glands

• specialized secretory organs, called

• are composed of epithelium supported by a network of connective tissue

1. endocrine glands

2. exocrine glands

two major types of glands in the body:

endocrine glands

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

• These glands are associated with an extensive network of blood vessels, and their hormones are transported throughout the body by way of the blood.

duct

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

1. unicellular

2. simple

3. compound

three major categories of exocrine glands

unicellular gland

Some exocrine glands are composed of only a single cell, such as goblet cells

goblet cells

secretes mucus

simple glands

are multicellular glands that have a single, nonbranched duct

1. tubular

2. acinar

The secretory portions of the simple gland can be shaped in one of two ways

tubular

which is a straight, narrow tube the same width as the duct

acinar

a saclike structure whose width is greater than the width of the duct

1. simple tubular

2. simple branched tubular

3. simple acinar

4. simple branched acinar

different types of simple glands

simple tubular

—glands forming a straight tube with no branching of the secretory portion

simple branched tubular

—gland with several tubular secretory portions branching from the single duct

simple acinar

—glands with a single saclike secretory portion

simple branched acinar

—glands with several acinar secretory portions branching from the single duct

compound glands

• are multicellular glands that have several branched ducts

• the secretory portions can be either tubular or acinar, or a mixture of both.

compound tubular

—glands with multiple ducts, each with a narrow tubular secretory portion

compound acinar

—glands with multiple ducts, each with several saclike secretory portions

compound tubuloacinar

—glands with multiple ducts, each with several tubular and acinar secretory portions

1. merocrine

2. apocrine

3. holocrine

three modes of secretion by exocrine glands

merocrine secretion

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

• is used by goblet cells, temperature sensitive sweat glands, and the exocrine portion of the pancreas.

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.

• Release of the fatty portion of milk by mammary glands occurs through — as does secretion of earwax.

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.

sebaceous glands

— in the skin release sebum (oil) through holocrine secretion, which can help explain the appearance of blackheads

connective tissue

• is a diverse primary tissue type that makes up part of every organ in the body.

• — differs from the other three tissue types in that it consists of cells separated from each other by abundant extracellular matrix

• —- is diverse in both structure and function.

1. enclosing and separating other tissues

2. connecting tissues to one another

3. supporting and moving parts of the body

4. storing compounds

5. cushioning and insulating

6. transporting

7. protecting

Functions of Connective Tissue

tendons

are strong cables, or bands, of connective tissue that attach muscles to bone,

ligaments

are connective tissue bands that hold bones together

blasts

create the matrix

cytes

maintain it

clasts

break it down for remodeling

macrophanges

are large white blood cells that are capable of moving about and ingesting foreign substances, including microorganisms in the connective tissue.

mast cells

are nonmotile cells that release chemicals, such as histamine, that promote inflammation.

1. protein fibers

2. ground substance

3. fluid

extracellular matrix of connective tissue has three major components:

1. collagen fibers

2. reticular fibers

3. elastic fibers

Three types of protein fibers——help form most connective tissues

collagen fibers

which resemble microscopic ropes, are very flexible but resist stretching

reticular fibers

are very fine, short collagen fibers that branch to form a supporting network.

elastic fibers

• have the ability to return to their original shape after being stretched or compressed, giving tissue an elastic quality.

• This tissue stretches like a rubber band in response to force and recoils when relaxed.

ground substance

consists of nonfibrous molecules. It is the “shapeless” background against which the collagen fibers are seen through the microscope.

proteoglycans

• are large molecules that consist of a protein core attached to many long polysaccharides.

• the amount of fluid in the matrix is correlated with the type and quantity of ground substance molecules.

• — trap large quantities of water between the polysaccharides, which allows them to return to their original shape when compressed or deformed

1. embryonic connective tissue

2. adult connective tissue

two main types of connective tissue

1. connective tissue proper

2. supporting connective tissue

3. fluid connective tissue

Adult connective tissue consists of three types:

loose connective tissue

consists of relatively few protein fibers that form a lacy network, with numerous spaces filled with ground substance and fluid.

1. areolar

2. adipose

3. reticular

Three subdivisions of loose connective tissue

areolar connective tissue

The extracellular matrix of — primarily consists of collagen fibers and a few elastic

fibroblasts

• The most common cells in loose connective tissue are the—

• are responsible for producing the matrix

adipose connective tissue

• consists of adipocytes, or fat cells, which contain large amounts of lipids for energy storage.

• Unlike other connective tissue types, — is composed of large cells and a small amount of extracellular matrix, which consists of loosely arranged collagen and reticular fibers with some scattered elastic fibers

• also pads and protects parts of the body and acts as a thermal insulator.

reticular connective tissue

• forms the framework of lymphatic tissue, such as in the spleen and lymph nodes, as well as in bone marrow and the liver

• Fine network of reticular fibers irregularly arranged

• Provides a superstructure for lymphatic and hemopoietic tissue

dense connective tissue

has a relatively large number of protein fibers that form thick bundles and fill nearly all of the extracellular space. These protein fibers are produced by fibroblasts

dense collagenous connective tissue

• has an extracellular matrix consisting mostly of collagen fibers

• Structures made up of —- include tendons, which attach muscle to bone; many ligaments, which attach bones to other bones; and much of the dermis, which is the connective tissue of the skin.

• — also forms many capsules that surround organs, such as the liver and kidneys

dense regular

In tendons and ligaments, the collagen fibers are oriented in the same direction, and so the tissue is called