Epithelium & Glandular Tissue

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Function of Simple Squamous Epithelium (flat, thin cells)

Back 1

diffusion across the tissue, in & out of lumen

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Function of Simple Cuboidal Epithelium (cube shaped cells

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absorption, secretion, conduction involving various metabolic processes (covering, secretion)

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Simple Columnar Epithelium (height greater than width)

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absorption, secretion, conduction involving complex metabolic processes (protection, lubrication, absorption, secretion)

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Examples of simple squamous

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"lining of vessels (endothelium), serous lining of cavities; pericardium, pleura, peritoneum (mesothelium)" OR

–Endothelium (blood vessels)

–Mesothelium

–Alveoli (in lung)

–Loop of Henle and parietal layer of Bowman’s capsule in the kidney

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Examples of simple cuboidal

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"covering the ovary, thyroid" OR

•Covers the ovary (germinal epithelium)

•Interior surface of tympanic membrane

•Ducts of many glands•Tubules in the kidney

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Examples of simple columnar

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"lining of intestine, gallbladder" OR

•Lining of the stomach & intestines

•Larger glands & ducts

•Inner ear

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Examples of Pseudostratified Epithelium

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"lining of trachea, bronchi, nasal cavity" OR

–Respiratory system

–Middle ear

–Parts of male urethra

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Transitional

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•a specialized epithelium located in the urinary system

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Endothelium

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•simple squamous epithelium that lines blood vessels

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Mesothelium

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•A single layer of flattened cells; the layer lines serous cavities (peritoneum in abdominal cavity, pleura surrounding lungs, pericardialsac of heart

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Stratified Squamous keratinized Epithelium

Function and Examples

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•Protection against dry environments

•Lines dry surfaces exposed to continuous trauma

–Skin/epidermis (keratinized)

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Stratified Squamous non-keratinized

Epithelium

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•No protection against dry environments

•Lines wet surfaces exposed to trauma

–Mouth (non-keratinized)

–Esophagus (non-keratinized)

–Vagina (non-keratinized)

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Transitional Epithelium

Function and Examples

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•Highly elastic

•Lines surfaces exposed to continuous dissension

-Bladder

-Ureters

-renal calyces

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3 characteristics of Transitional Epithelium

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•Apical cells bulge slightly into lumen

•Some cells bi-nuceated

•Apical cell surface stains slightly more deeply pink(actin filaments)

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Composition of Basal Lamina

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•PAS positive

•Collagen type IV - for structural stability•

•Proteoglycans (heparan sulfate) – negatively charged (highly anionic), attracts cations & water,regulates movements of cations.

•Laminin, entactin & fibronectin – highly adhesive glycoproteins, act as a glue to bind variouscomponents of the basal lamina.

Front 16

Microvilli

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Small finger-likeprojections of the apical cell surface

Core of cytoplasm with actinfilaments

Increase surfacearea

Brush or striated border in lightmicroscopyInteractions of actinand myosin allow the contractionof microvilli (this aid the absorptive process)

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"Terminal Web" of Microvilli

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The filaments are anchored to themembrane and below they mesh into a network of filaments known as the “terminalweb”

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Function of terminal web

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This terminal web provides rigidity topermit the actin-myosin interaction

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Structure of Microvilli

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•Formed by actin filaments linked by connecting proteins.

•Actin filaments are attached to cytoplasmic microfilaments.

Covered by a glycocalyx

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Stereocilia

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- Non-motilelong processes of the apical surface - Modified microvilli

- Only found in the inner ear & theepididymis

- In the epididymisthey appear as long & sometimes branching microvilli

- In the innerear, they have a regular arrangement

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Function and type of Stereocilia

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- In the epididymis the stereocilia have absorptivefunctions

- In the inner ear (hair cells) the stereocilia have receptorfunctions

Front 22

Function of cilia

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Numerous in the respiratoryepithelium, where they sweep the mucusout from the lumen of respiratory tract (rapid forward beat and slow recoverystroke)

Front 23

Description of Cilia

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•Hair-likeappendages 0.2 µm in diameter with a bundle of parallel microtubules at theircore •Bendin coordinated, unidirectional wavesNumerousin epithelial cells of –respiratorytract,–maleand female reproductive tracts & –ependymalining cavities on CNS

Front 24

Structure of Cilia

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•Longcylindrical shaft

•Taperingtip

•Axoneme(motile machinery of the cilia)

•Basalbody (kynetosome) inthe apical cytoplasm

Front 25

Cilia & flagella both are covered by what?

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Cilia & flagella both covered by plasma membrane

Front 26

Cilia & flagella description of movement

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Movement of cilia & flagella result form sliding of outer microtubule doublets relative to one another & powered by motor activity of axonemal dynein.

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Basal Infoldings

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- Infoldings or pockets of basal cytoplasm - - -

- Method of increasingthe surface area at base of the cell

- Occurs in cellsinvolved in fluid transport with rapid absorption and/orsecretion of substances (kidney, serous units of salivary glands)

- Can extend to lateralmembranes

Front 28

What structure shows both microvilli and basal inholdings

Back 28

Proximal convoluted tubules of thekidney shows both microvilli and basal infoldings

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What are the basal infoldings and mitochondria characteristics of?

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Basal infoldingsand mitochondria is characteristic of epithelial cells that reabsorb electrolytes andfluids

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Transitions of Epithelia

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- Areas where one epithelium ends & other begins

- Very vulnerable (neoplasms, infections)

- Cervix of uterus, gastroesophageal junction, ano-rectaljunction

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Labile Cells

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•Continuously dividing

•Stem cells = common example of labile cells

•Examples:

-Surface epithelial cells

-Hematopoietic cells

-Lymphoid cells

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What are labile cells vulnerable of and why?

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Due to their high mitotic rate, labilecells are vulnerable to mutation and malignancies

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Stable Cells

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•Also known as quiescent cells

•Normally they have a low level of replication

•Can rapidly divide in response to stimuli

•Cells that make up glandular organs is an example of stable cells

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Permanent Cells description and example

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•Unable to divide

•Can increase in size and accelerate their function

•Examples: Brain Renal corpuscles Cardiac muscle

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Permanent cells are very resistant to what?

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Very resistant to neoplasia

Front 36

Cell Adaptations:

Atrophy

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•Atrophy – decrease in size and in number

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Cell Adaptations:

Hypertrophy

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•Hypertrophy – increase in size

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Cell Adaptations:

Hyperplasia

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•Hyperplasia – increase in number (excludes tumor formation)

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Cell Adaptations:

Metaplasia

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– transformation of one tissue into another (acquired)

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Cell Adaptations:

•Heteroplasia

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– development of elements not normal for the actual tissue; tissue malposition (hamartoma)

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Cell Adaptations:

•Neoplasia

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– uncontrolled and progressive new growth of tissue (I.e., tumor formation)

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Cell Adaptations:

•Dysplasia

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– cytological term. Its like a variation of the normal somatic cell itself. changes are reversible if the factors causing it are removed. Dysplastic cells are the earliest form of pre-cancerous lesion

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Cell Adaptations:

•Anaplasia - is dedifferentiation. maturedifferentiated cell goes back to resemble its progenitor cell/ parent cell.Anaplasia is an advanced cancer

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is dedifferentiation. maturedifferentiated cell goes back to resemble its progenitor cell/ parent cell.Anaplasia is an advanced cancer

Front 44

Glandsclassified by structure

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•(A)Unicellular

–Individual secretory cells

–Only unicellular glands aregoblet cells

•They secrete mucin

•They are scattered amongrespiratory and GIT Stain positive for PAS

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Four types of Glandular Tissue

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- endocrine

- paracrine

- autocrine

- juxtacrine

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Location of Goblet Cells

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•Basallysituated nucleuswith a well developed RER.

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Functions of Goblet Cells

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• Functions of mucus:

•Protective function in the respiratory tract – trapping of dust & microorganisms.

•Protects intestinal wall from autodigestion by digestive enzymes.

•Lubricates the passage of feces in the large intestine.

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Simple Gland

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•Has a single duct does notdivide on its way to the gland

•Secretory region may be divided (not ducts)

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Compound Glands

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•Duct divides one or moretimes before reaching the cells

•Secretory region may also be divided

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Characteristicsof secretory cell types

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•Basophilic cytoplasm –peptide secretion

•Nucleus vesicular /pale,with large amount of heterochromatin

•Prominent nucleolus &Golgi apparatus

•May show granularity

Front 51

Eccrine/ Merocrine

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•No loss of cytoplasm in theprocess of secretion

•Cell shape cuboidal to columnar

•Most exocrine and allendocrine glands

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Examples of Eccrine/ Merocrine

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•E.g: Sweat glands thoughout the body

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Apocrine

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•Loss of some cytoplasm inthe process

•Apical region pinches off& degenerates

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Examples of Apocrine

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•E.g. Goblet cells, ceruminous glands of external ear, lipid droplets from mammary gland

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Holocrine

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•Entire cell dies to form asecretion by degeneration of cytoplasm

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Examples of Holocrine

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•E.g. Sebaceous glands, tarsal (Meibomian) glands in the eyelid.

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SerousSecreting Cell

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•Cells secrete a proteinrich watery fluid.

•Spherical basal nucleus

•Abundant basilar RER &Golgi body (supra nuclear).

•Secretorygranules in the apical region – zymogengranules (secretions in inactive form).

Front 58

Examples of Serous Secreting Cell

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•E.g: gastric chief cells, paneth cells, salivary serous cells

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Myoepithelial Cells

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•Many exocrine glands have stellate or spindle shaped myoepithelial cells that surround the gland acini.

•Cytoplasm contains contractile filaments.•

•Contraction helps to propel secretory products towards the exterior.

•They are innervated bynerves in the salivary glands

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Location of Myoepithelial Cells

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•Lie between the secretory cell & the basal lamina

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Components of the exocrine gland

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1.Main excretory – stratified cuboidal epithelium

2.Intralobular ducts (originate from secretory units called acini)

- Striated and intercalated ducts

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Striated duct

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–lined by cuboidal to columnar cells.

–contain infoldings of basal plasma membrane (striations).

–many mitochondria present in the basal part for active ion transport.

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Intercalated duct

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–lined by ,low cuboidal cells (add bicarbonates to the saliva)

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Striated ducts

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•Striatedducts concentrate the secretory product.

•Pumpwater and ions across the duct epithelium, from the duct lumen and intointerstitial fluid.

•Ultrastructurally,striated duct cells have extensive infoldings of the basal membrane.Thesefolds are closely associated with mitochondria that provide ATP for the membrane pumps.

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How did the striated ducts get their name?

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• Inlight microscopy, the basal folds and mitochondria are sometimes visible asbasal striations, hence the name striated duct.

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What is the saliva type of Parotid and Von Ebner's (on the tongue)

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Saliva type: serous

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What is the saliva type of Sublingual?

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Mostly mucous

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What is the saliva type of submandibular?

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Mixed, more serous than mucous

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What is the saliva type of "most minor"

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Mucous

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Functions of epithelium

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•Transcellular transport

•Diffusion of oxygen and carbon dioxide

•Carrier protein-mediated transport: Amino Acids, glucose

•Absorption: endo/pinocytosis

•Secretion: exocytosis

•Protection

Vesicle-mediated transport: IgA

Front 71

Whats the Epithelium Vesicle-mediated transport?

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IgA

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What type of permeability does the epithelium have?

Back 72

Selective permeability: tight junction

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Eight Main Characteristics of Epithelium

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1. Restson a basement membrane.

2.Little intercellular space.

3.Avascular. **exception (inner ear)

4.Derived from all three germ layers.

5. Canundergo metaplasia.

6. Polarity.

7. Ableto regenerate.

8.Nuclei tend to conform to shape of cells.

Front 74

Whats the exception to the Epithelium being avascular?

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Avascular epithelium, with the exception of the stria vascularis of the inner ear, contains no blood or lymph vessels.

Front 75

All components of Basal Lamina are secreted by what cells? And what is the exception?

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- All components are secreted by the epithelial cells except fibronectin which is secreted by fibroblasts

- Basal lamina is also secreted by muscle cells, adipose cells & Schwann cells –External lamina.