anatomy bojrab ch 4

true or false: Individual body cells are specialized

Each type performs specific functions that maintain homeostasis

true

tissues

-Groups of cells similar in structure that perform common or related function

histology

-Study of tissues

4 basic tissue types

epithelial, connective, muscle, and nervous tissue

nervous tissue overview

internal communication

- brain

- spinal cord

- nerves

muscles tissues overview

contracts to cause movement

- skeletal muscles

- cardiac muscles

- smooth muscles

epithelial tissue overview

forms boundaries between different environments, protects, secretes, absorbs, filters

- lining of digestive tract organs

- glands

- skin surface (epidermis)

connective tissue overview

supports, protects, binds other tissues together

- bones

-tendons

-fat and other soft padding tissue

fixed

tissue is preserved with solvent to be viewed

sectioned

cut into slices thin enough to transmit light to electrons to be viewed

stained

to enhance contrast, although artifacts detract from what the sample looks like in living tissues

artifacts

distortions

light microscopy staining

colored dyes

Electron Microscopy staining

uses heavy metal salts

TEM

transmission electron microscopy, shows a section

SEM

scanning electron microscopy, shows a surface

epithelial tissue definition

is a sheet of cells that covers a body surface or lines a body cavities

2 main forms of epithelial tissue

covering and lining epithelia, glandular epithelia

Covering and lining epithelium

-forms the outer layer of skin, lines open cavities, and covers walls and organs of the ventral body cavity

▪Skin

▪Lining of urogenital, digestive, and respiratory systems

Glandular epithelium

-forms glands of the body

▪Salivary glands

functions of epithelial tissue

protection, absorption, filtration, excretion, secretion, and sensory reception

5 distinguishing characteristics of epithelial tissue

1.Polarity

2.Specialized contacts

3.Supported by connective tissue

4.Avascular but innervated

5.Regeneration

apical surface of epithelial tissue

-upper free side, is exposed to surface or cavity

▪Most apical surfaces are smooth, but some have specialized fingerlike projections called microvilli

basal surface of epithelial tissue

lower attached side, faces inwards toward body and attaches to basal lamina

basal lamina

▪an adhesive sheet that holds basal surface of epithelial cells to underlying cells

apical and basal layers of epithelial tissue (picture)

specialized contacts of epithelial tissue

-Epithelial tissues need to fit closely together

▪Many form continuous sheets

-Specialized contact points bind adjacent epithelial cells together

lateral contacts of epithelial tissue include...

tight junctions and desmosomes

true or fale: All epithelial sheets are supported by connective tissue

true

reticular lamina

deep to basal lamina, consists of network of collagen fibers

basement membrane

made up of basal and reticular lamina, reinforces epithelial sheet, resists stretching and tearing, defines epithelial boundary

cancer cells and the epithelium

•Cancerous epithelial cells are not contained by the basement membrane boundary like other cells

•They penetrate the boundary and invade underlying tissues, resulting in spread of cancer

epithelial cells are avascular but innervated

-No blood vessels are found in epithelial tissue

▪Must be nourished by diffusion from underlying connective tissues

-Epithelia are supplied by nerve fibers, however

regeneration of epithelial tissue

-Epithelial cells have high regenerative capacities

-Stimulated by loss of apical-basal polarity and broken lateral contacts

-Some cells are exposed to friction, some to hostile substances, resulting in damage

▪Must be replaced

▪Requires adequate nutrients and cell division

Classification of Epithelial Tissue

•All epithelial tissues have two names

-First name indicates number of cell layers

-Second name indicates shape of cells

Simple epithelia (name)

▪consists of a single cell layer

-Located where thin barrier is desirable

Stratified Epithelia (name)

▪consists of two or more cell layers

-Located in high-abrasion areas (example: lining of mouth)

squamous

flattened and scale-like

cuboidal

box-like, cube

columnar

tall, column-like

true or false- cell shape is named according to basal layer

false- In stratified epithelia, shape can vary in each layer, so cell shape is named according to the cell shape in apical layer

simple epithelia

involved in absorption, secretion, or filtration processes

simple squamous epithelium

Cells are flattened laterally, and cytoplasm is sparse

Function where rapid diffusion is priority

Example: kidney, lungs

Endothelium

simple squamous epithelia- lining of lymphatic vessels, blood vessels, and heart

Mesothelium

simple squamous epithelia- serous membranes in the ventral body cavity

simple cuboidal epithelium

-Single layer of cells

-Involved in secretion and absorption

-Forms walls of smallest ducts of glands and many kidney tubules

simple columnar epithelium

Single layer of tall, closely packed cells

Involved in absorption and secretion of mucus, enzymes, and other substances

Found in digestive tract, gallbladder, ducts of some glands, bronchi, and uterine tubes

simple columnar epithelium and mucus

Some cells have microvilli, and some have cilia

Some layers contain mucus-secreting goblet cells

Ciliated cells move mucus

Pseudostratified columnar epithelium

Cells vary in height and appear to be multi-layered and stratified, but tissue is in fact single-layered simple epithelium

Many cells are ciliated

Involved in secretion, particularly of mucus, and also in movement of mucus via ciliary sweeping action

Located mostly in upper respiratory tract, ducts of large glands, and tubules in testes

"Pseudo" means...?

false

stratified

-Involve two or more layers of cells

-New cells regenerate from below

▪Basal cells divide and migrate toward surface

-More durable than simple epithelia because protection is the major role

Stratified squamous epithelium

-Most widespread of stratified epithelia

-Free surface is squamous, with deeper cuboidal or columnar layers

-Located in areas of high wear and tear (example: skin)

-Keratinized cells found in skin; nonkeratinized cells are found in moist linings

Stratified cuboidal epithelium

-Quite rare

-Found in some sweat and mammary glands

-Typically, only two cell layers thick

Stratified columnar epithelium

-Also, very limited distribution in body

-Small amounts found in pharynx, in male urethra, and lining some glandular ducts

▪Usually occurs at transition areas between two other types of epithelia

▪Only apical layer is columnar

transitional epithelium

-Forms lining of hollow urinary organs

▪Found in bladder, ureters, and urethra

-Basal layer cells are cuboidal or columnar

-Ability of cells to change shape when stretched allows for increased flow of urine and, in the case of bladder, more storage space

gland

One or more cells that make and secrete an aqueous fluid called a secretion

how are glands classified?

site of product release, relative number of cells forming the gland

endocrine gland meaning

▪ductless glands that produce hormones

exocrine gland meaning

▪secrete products onto body surfaces or into body cavities

-Example: sweat glands

example of unicellular gland

goblet cells

example of multicellular gland

salivary

endocrine glands

-Ductless glands

▪Secretions are not released into a duct; are released into surrounding interstitial fluid, which is picked up by circulatory system

-Secrete (by exocytosis) hormones

-Target organs respond in some characteristic way

hormones

messenger chemicals that travel through lymph or blood to their specific target organs

exocrine glands

-Secretions are released onto body surfaces, such as skin, or into body cavities

-More numerous than endocrine glands

-Secrete products into ducts

-Can be:

▪Unicellular

▪Multicellular

examples of exocrine glands

mucous, sweat, oil, and salivary glands

important unicellular gland

mucous cells and goblet cells, found in epithelial linings of intestinal and respiratory tracts and produce mucin

mucin

a sugar-protein that can dissolve in water to form mucus, a slimy protective, lubricating coating

multicellular exocrine glands

-Multicellular exocrine glands are composed of a duct and a secretory unit

-Usually surrounded by supportive connective tissue that supplies blood and nerve fibers to gland

▪Connective tissue can form capsule around gland, extend into gland, and divide it into lobes

how are multicellular exocrine glands classified?

structure and mode of secretion

Simple exocrine glands versus. compound glands structure

Structure- Simple exocrine glands have unbranched ducts versus. compound glands have branched ducts

3 forms of secretory units

tubular, alveolar, tubuloalveolar

tubular

-if the secretory cells form tubes

alveolar

-if the secretory cells form sacs

Tubuloalveolar

have both types of secretory units

merocrine

▪secrete products by exocytosis as secretions are produced

-Most common and does not alter secretory cells

examples of merocrine

most sweat glands, pancreas, salivary glands

holocrine

-accumulate products within until rupture

-Replaced by division of underlying cells

examples of holocrine

-sebaceous (oil) glands

apocrine

▪accumulate products within, but only apex ruptures

-Cell repairs damage and repeats

-Controversy if present in humans

examples of apocrine

-Mammary glands are closest example, but most scientists classify mammary glands as merocrine glands

what is the most abundant and widely distributed of the primary tissues?

connective tissue

major functions of connective tissue

binding and support, protecting, insulating, storing reserve fuel, transporting substances within the body (blood)

4 main classes of connective tissue

connective tissue proper

cartilage

bone

blood

connective tissue proper subclases

loose connective tissue (areolar, adipose, reticular)

dense connective tissue (regular, irregular, elastic)

connective tissue proper components

cells: fibroblasts, fibrocytes, defense cells, adipocytes

matrix: gel- like ground substance, all three fiber types (collagen, reticular, elastic)

connective tissue proper general features

Six different types; vary in density and types of fibers

Functions as a binding tissue

Resists mechanical stress, particularly tension

Provides reservoir for water and salts

Energy (fat) storage

cartilage subclasses

Hyaline cartilage, elastic cartilage, and fibrocartilage.

cartilage components

cells: chondroblasts (found in growing cartilage), chondrocytes

matrix: gel-like ground substance, fibers (collagen and elastic fibers in some)

cartilage general features

Resists compression because of the large amounts of water held in the matrix

Functions to cushion and support body structures

Avascular (lacks blood vessels)

bone tissue subclasses

compact bone and spongy bone

bone tissue components

cell: osteoblasts, osteocytes

matrix: Gel-like ground substance calcified with inorganic salts, fibers (collagen)

bone tissue general features

Hard tissue that resists both compression and tension

Functions in support

blood components

cells: red blood cells/erythrocytes, white blood cells/leukocytes, platelets

matrix: plasma

blood general features

-a fluid tissue

- functions to carry O2, CO2, nutrients, wastes, and other substances (such as hormones)

Two characteristics make connective tissues different from other primary tissues:

extracellular matrix and common origin

extracellular matrix of connective tissue

-Extracellular matrix of nonliving portion of connective tissues in which the living cells are suspended in

▪Supports cells so they can bear weight, withstand tension, endure abuse

▪All other primary tissues are composed mainly of cells, not extracellular matrix

common origin of connective tissue

arise from mesenchyme (embryonic tissue)

3 main components of all connective tissues

ground substance, fibers, cells

true or false: Cells and fibers together make up the extracellular matrix

false- Ground substance and fibers together make up the extracellular matrix

true or false: Composition and arrangement of these three elements vary considerably in different types of connective tissues

true