4. EPITHELIAL CELLS

• Covering, lining, and protecting surfaces (eg, skin)

• Absorption (eg, the intestines)

• Secretion (eg, the parenchymal cells of glands)

• Contractility (eg, myoepithelial cells).

The principal functions of epithelial tissues are:

serous demilunes

Clumps of serous cells at the ends of some mucous tubules appear as crescent-shaped structures called _______________________

apical cytoplasm and plasmalemma

apocrine secretions are usually released as large lipid droplet that is usually discharged together with some of the _________________ and ___________________

lamina propria

serves to support the epithelium

lamina propria

provides nutrition and binds epithelia to underlying structures

lamina propria

identify the image

Papillae

small invagination's or irregularities in the connective tissue surface that increases area of contact between the connective tissue and the epithelial tissue

Basal pole

region of the cell contacting the connective tissue

adhesion

lamina propria has papillae that increases ____________

Apical pole

facing a space

Apical pole

project towards the external surface or the lumen of an organ which epithelia cover

Lateral surfaces

regions that adjoin the adjacent cells

Basement membrane

a felt-like sheet of extracellular material in the basal surface of epithelial cells

BASAL MEMBRANE

identify the image presented

1. basal lamina

2. reticular lamina

Two structures of basement membrane:

basal lamina

(Two structures of basement membrane)

network of fine fibrils

reticular lamina

(Two structures of basement membrane)

a more diffuse and fibrous layer

collagen

most abundant protein in the body

kidney stones

too much use of collagen will lead to _________________ due to high levels of oxalate

False

T or F

basal lamina can be observed in light microscopy

1. Laminin

2. Type IV collagen:

The macromolecular components of basal laminae:

Laminin

(The macromolecular components of basal laminae)

These are large glycoprotein molecules that self assemble to form a lace-like sheet immediately below the cells' basal poles where they are held in place by the transmembrane integrins.

Type IV collagen

(The macromolecular components of basal laminae)

Monomers of type IV collagen contain three polypeptide chains and self-assemble further to form a felt-like sheet associated with the laminin layer

entactin/nidogen ; perlecan

laminin and type IV collagen network are held together by adhesive glycoprotein ________________ and by ____________, a proteoglycan

– Type III collagen

– Type VII collagen

Diffuse meshwork of reticular laminae contains:

albumin

most abundant protein in the blood

basal lamina

"_____________" is used to denote the lamina densa and its adjacent layers and structures seen with the TEM

Basement membrane

"__________________" is used to denote the structures seen with the light microscope.

occluding junctions

a junction that seals to prevent the flow of materials between the cells is called ________________

adhesive or anchoring junctions

sites of adhesion is called

gap junctions

is a junction that channels for communication between adjacent cells

1. Zonula occludens

2. Zonula adherens (intermediate junction)

3. Macula adherens (desmosomes)

enumerate the three distinct zones of the junctional complex

Zonula occludens

(three distinct zones of the junctional complex)

• important in transporting epithelium

• maintaining the structural integrity of epithelium

Zonula adherens (intermediate junction)

(three distinct zones of the junctional complex)

• “terminal web”

• Serves as a site of insertion for the contractile microfilaments that form the core of the microvilli.

• Aid in contraction of microvilli

Macula adherens (desmosomes)

(three distinct zones of the junctional complex)

• Appears as dense dots or fusiform thickening of the cells

• Site of attachment of the cytoskeleton to the cell surface

• Sites of cell to cell adhesion

“terminal Bar”

In LM ; entire structure of junctional complex is called _______________

1

6 connexins = __ connexon

Nexus (gap junction)

• Concerned with cell to cell communication

• “communicating junction”

Connexions

_____________ are protein subunits that make up gap junction channels (nexus).

between osteocytes, smooth and cardiac muscles, neurons

nexus (gap junction) is present in

skeletal muscle, blood

nexus (gap junction) is absent in

Cx46 and Cx50

Which connexins are important in the lens of the eye?

cataract

Mutation of Cx46 and Cx50 can cause ____________

Cx26

Which connexin is commonly associated with congenital deafness or ear dysfunction?

Gap junction

Which junction is affected when connexins are defective?

Microvilli

Delicate vertical striations in a refractile border of columnar epithelium

Microvilli

Prominent in cells whose principal function is absorption

Striated border

Which border is found in the intestinal epithelium?

Brush border

Which border is found in the epithelial cells of the kidney?

microvilli

Small finger-like processes that increase the efficiency of absorption

Stereocilia

Which long, pyriform tuft of slender processes projects into the lumen from epididymis epithelial cells?

Basal infoldings

Which basal structure increases surface area at the base of a cell to promote absorption?

cilia ; Stereocilia

larger than microvilli = __________

longer than mIcrovilli = ——————

Primary cilium

Which type of cilia is enriched with receptors for signal transduction complexes?

Motile cilia

Which type of cilia is found only in epithelia, abundant on the apical surface of cuboidal or columnar cells

Cilia

Function to propel fluid or coating of mucus towards the exterior

1. Covering (lining) epithelia

2. Secretory (glandular) epithelia

Main Groups of Epithelia

1. Simple

2. Pseudostratified

3. Stratified

(Classification of Covering Epithelia)

number of cell layers

1. Squamous

2. Cuboidal

3. Columnar

4. transitional

(Classification of Covering Epithelia)

cell morphology

Simple Squamous Epithelium

• Very thin, flat cells

• Mosaic pattern

I. Simple Squamous Epithelium

• Attenuated cytoplasm with central bulging nucleus.

Endothelium

Which epithelium lines blood vessels and lymph vessels and the cavities of the heart?

Mesothelium

Which epithelium lines the serous cavities like pleura, pericardium, peritoneum, tunica vaginalis testis

Mesenchymal

Which epithelium lines the interior chamber of the eye, , perilymph spaces of the internal ear, subdural and subarachnoid spaces.

Flattened cells

Which epithelium consists of flattened cells lining the pulmonary alveoli and bowman’s capsule

–Facilitates the movement of the viscera (mesothelium)

–Active transport by pinocytosis (mesothelium and endothelium)

–Secretion of biologically active molecule

Main Functions of Simple Squamous Epithelium

Simple Cuboidal Epithelium

• Row of square or rectangular profile

Simple Cuboidal Epithelium

• a classification of epithelial tissue wherein the nuclei tend to aligned at the same level in all of the cells, “box-like”, “cube-like”

Simple Cuboidal Epithelium

Which epithelium covers the surface of the ovary?

Simple Cuboidal Epithelium

Which epithelium covers the surface of the Thyroid follicles?

Simple Cuboidal Epithelium

Which epithelium covers the surface of the choroid plexus?

Simple Cuboidal Epithelium

Which epithelium is found in the pigmented layer of the retina?

– Covering

– secretion

Main Function of Simple Cuboidal Epithelium

Simple Columnar Epithelium

• a classification of epithelial tissue wherein the membrane composed of cylindrical cells possessing an appreciable height aside from length and width.

Simple Columnar Epithelium

• a classification of epithelial tissue wherein the nuclei are at the same level and situated nearer to the basal surface than the apical surface.

Simple plain tall columnar epithelial

which of epithelium is composed of mucosa of the stomach, small and large intestine, gallbladder, bigger ducts of glands

Simple plain low columnar epithelial

which of epithelium is composed of smaller ducts of glands, some excretory tubules of kidney

– Protection

– Lubrication

– absorption

– secretion

Main Function of Simple Columnar Epithelium

Keratinized stratified squamous epithelium

Which epithelium shows cells that become irregular and flattened as keratin accumulates?

Keratinized stratified squamous epithelium

Which epithelium has cells that become hardened and cornified toward the surface?

Keratinized stratified squamous epithelium

Which epithelium undergoes progressive removal of cells near the skin surface?

Keratinized stratified squamous epithelium

Which epithelium consists of thin, metabolically inactive packets of keratin-lacking nuclei

– Protection

– Prevents water los

Main Function of keratinized stratified squamous epithelium

epidermis

where is keratinized stratified squamous epithelium mostly distributed in the body?

Non-keratinized stratified squamous epithelium

Which epithelium lines wet cavities where loss of water is not a problem?

Non-keratinized stratified squamous epithelium

Which epithelium is found in the inner most surface of the body?

Non-keratinized stratified squamous epithelium

Which epithelium has flattened cells of the surface layer that contain much less keratin, retaining their nuclei and metabolic function

– Protection

– Secretion

– Prevents water loss

Main Function of non-keratinized stratified squamous epithelium

– Mouth

– Esophagus

– Larynx

– Vagina

– Anal canal

what parts of the body is lined by non-keratinized stratified squamous epithelium

– Excretory ducts of salivary and sweat glands

– Developing ovarian follicles

what parts of the body is lined by Stratified Cuboidal Epithelia

– Protection

– Secretion

Main function of Stratified Cuboidal Epithelia

– Conjuctiva

what parts of the body is lined by Stratified Columnar Epithelia

– Protection

– secretion

Main Function of Stratified Columnar Epithelia

Transitional epithelium (urothelium)

Which epithelium has a thin basal lamina and lines distensible organs?

Transitional epithelium (urothelium)

Which epithelium appears very thin when the organ is distended and thicker when collapsed?

Transitional epithelium

Which epithelium consists of many layers in the contracted stage?

One or two rows of basal cells

In contracted urothelium, what is the deepest layer composed of?

– Bladder

– Ureter

– Rena calyces

Example of Distribution of Transitional (Urothelium) Epithelia

– Protection

– Distensibility

Main Function of Transitional (Urothelium) Epithelia

Pseudostratified Epithelia

Appears to be composed of several layers of cell when in reality, there is only one layer