1. Epithelial Tissue-II

2. 1. What type of tissue lines the bladder. a
1. What type of tissue lines the bladder? a. Simple squamous epithelium b. Simple cuboidal epithelium c. Simple columnar epithelium d. Stratified squamous epithelium e. Transitional epithelium
2. What type of tissue lines most ducts? a. Simple squamous epithelium b. Simple cuboidal epithelium c. Simple columnar epithelium d. Stratified squamous epithelium e. Transitional epithelium

3. 3. What type of epithelium is associated with goblet cells. a
3. What type of epithelium is associated with goblet cells? a. Simple squamous epithelium b. Simple cuboidal epithelium c. Simple columnar epithelium d. Stratified squamous epithelium e. Pseudostratified epithelium
4. What type of epithelial cells are as tall as they are wide? a. Simple b. Stratified c. Squamous d. Cuboidal e. Columnar

4. 5. What do you call the simple squamous epithelium that lines the blood vessels?
a. Epithelioid tissue b. Mesothelium c. Endothelium d. Transitional e. Pseudostratified

5. Surface Specializations
Microvilli
Stereovilli
Cilia
Basal infoldings

6. Microvilli Small finger-like projections of the apical cell surface
Core of cytoplasm with actin filaments
Increase surface area – most imp function
Brush or striated border in light microscopy
Interactions of actin and myosin allow the contraction of microvilli (this aid the absorptive process)
The filaments are anchored to the membrane and below they mesh into a network of filaments known as the “terminal web”
This terminal web provides rigidity to permit the actin-myosin interaction

7. Structure of Microvilli
Formed by actin filaments linked by connecting proteins.
Actin filaments are attached to cytoplasmic microfilaments.
Covered by a glycocalyx.
The microvilli also contain the brush border enzymes such as lactase and alkaline phosphatase

8. Microvilli
© Universidad Catolica de Chile

9. Microvilli ultrascructure

10. Microvilli ultrascructure

11. Stereocilia Non-motile long processes of the apical surface
Modified microvilli
Only found in the inner ear & the epididymis
In the epididymis they appear as long & sometimes branching microvilli
In the inner ear, they have a regular arrangement
In the epididymis the stereocilia have absorptive functions
In the inner ear (hair cells) the stereocilia have receptor functions
porin (protein responsible of permeability to solutes smaller than 5 kD)

12. Stereocilia – inner ear
porin (protein responsible of permeability to solutes smaller than 5 kD)

13. Stereocilia - epidydimis
porin (protein responsible of permeability to solutes smaller than 5 kD)
Epididymis had pseudostratified epithelium
© Brown University

14. Cilia
Numerous in the respiratory epithelium, where they sweep the mucus out from the lumen of respiratory tract (rapid forward beat and slow recovery stroke)
Also found in maculae and cristae of the inner ear and in the rods of the retina, where they serve as receptors

15. Structure of cilia nine + two microtubules _ axoneme
- organised from basal body

16. Function of cilia: undergo regular, synchronous movement
exhibit a rapid forward movement (effective stroke) followed by a slower return movement ( the recovery stroke)
movement is based on the longitudinal sliding of the microtubules in the peripheral doublets – through dynein arms and powered by ATPase

17. Cilia

18. Cilia

19. kartagener syndrome Symptoms
inherited via an autosomal recessive pattern. Symptoms result from defective cilia motility.
Symptoms
Immotile spermatozoa 
chronic upper and lower respiratory tract disease resulting from ineffective mucociliary clearance.
Situs invertus

20. Basal Infoldings Infoldings or pockets of basal cytoplasm
Proximal convoluted tubules of the kidney shows both microvilli and basal infoldings
Infoldings or pockets of basal cytoplasm
Method of increasing the surface area at base of the cell
Occurs in cells involved in fluid transport with rapid absorption and/or secretion of substances (kidney, serous units of salivary glands)
Can extend to lateral membranes
Basal infoldings and mitochondria is characteristic of epithelial cells that reabsorb electrolytes and fluids

21. Basal Infoldings
Characterized by the ubiquitous presence of Na+,K+ – ATPase
Generate the Na+, K+ gradient of the cell. Na+ is pumped out of the cell, and K+ is pumped into the cell by this ATP-dependent pump.

22. Basal infoldings

23. Basal infoldings

24. Question
In the figure below, A is a transmission electron micrograph, and B is a freeze-fracture preparation of a specific cellular structure.
Mutations in the proteins that constitute the intramembranous particles labeled in the freeze-fracture image below occur in humans.
Which of the following would one expect to occur in the presence of such mutations?
Next slide - picture

25. Question
In the figure below, A is a transmission electron micrograph, and B is a freeze-fracture preparation of a specific cellular structure.
Mutations in the proteins that constitute the intramembranous particles labeled in the freeze-fracture image below occur in humans.
Which of the following would one expect to occur in the presence of such mutations?
Next slide - picture

27. Choose the best response
Faster conduction of nerve impulses
Increased peristalsis in the small intestine
Cardiac arrhythmias
More rapid mobilization of glycogen to glucose in response to low blood sugar levels
Decreased adherence of epithelial cells to the basement membrane

28. Cell-cell, cell-matrix interactions :Junctional complex
Majority of cells linked to each other & surroundings (extracellular matrix)
Junctional complexes:
Barrier to fluid flow
Maintain apical / basolateral polarity in cells
Maintain cell shape
Cell to cell communication
Functional Classification
Occlusion (Zonula occludens)
Adhesion (Zonula adherens & desmosome)
Communicating (Gap junction)
Components:
Zonula occludens
Zonula adherens
Macula adherens (desmosomes)
Gap junction

30. Macula densa / adherens
Zonula occludens
Zonula adherens
Terminal web
Microvilli

31. Functions of junctional complexes
Zonula occludens,
which provides a tight seal between the epithelial cells.
Zonula adherens,
which interacts with actin which comprises the terminal web
Macula adherens (desmosome).
It forms a spot weld or rivet between the adjacent cells and resists shearing forces on the epithelium.

32. Zonula occludens E.g: Brain, GIT, Lungs, Testis, Retina
Surrounds the entire apical perimeter of adjacent cells
Formed by fusion of the outer leaflets of the cells’ plasma membranes
Transmembrane proteins attached directly to each other
occludin, claudins,
JAM (junctional adhesion molecule)
Prevents movement into the intercellular space
E.g: Brain, GIT, Lungs, Testis, Retina

33. Occluding Junctions (Zonula occludens or tight junctions)
Intestinal lumen

34. The sperms in the body are not exposed to the circulation as they are antigenically different from the somatic cells. Hence they need to be segregated by the blood-testis barrier which has ________________ between Sertoli cells.
Connexons
Zonula occludens
Macula adherens
Hemidesmosome
Zonula adherens
List other areas where there are tight junctions

35. Zonula Adherens
Intermediate junction, it is the area that surrounds the entire perimeter of epithelial cells
10-20 nm separation between the adjacent plasma membranes
Actin filaments: on each of its cytoplasmic surfaces; it is linked to a transmembrane protein called E-cadherin
E-cadherin dependent on Ca++ for promoting adhesion at this structurally supportive junction

36. Neural tube defects (NTD)
Zonula adherens
Neural tube defects (NTD)
In the apical part of the cells, the actin filament bundles contract, narrowing the cells at their apical ends. The position of the zonula adherens, forming a contractile ring around the circumference of the cell, coupled with the contractile nature of the actin microfilament bundles is ideal for regulating morphogenetic changes.

37. (Macula adherens) Desmosomes
Disk-shaped adhesive site - lateral membrane between epithelial cells.
Dense plaque of intracellular attachment proteins (desmoplakins), on the cytoplasmic surface of each opposing cell
Involved in cell-cell adhesion and are abundant in organs that undergo severe mechanical stress such as the skin
Keratin filaments (tonofilaments) loop into and out of the dense plaque from the cytoplasm
Desmogleins and desmocollins (cadherin family)

38. (Macula Adherens) Desmsomes
Rivets through the plasma membrane of adjacent cells.
Intermediate filaments (eg. keratin or desmin) attached to membrane
associated proteins that form a dense plaque on the cytoplasmic face
of the membrane. Cadherin molecules form actual anchor by attaching
to cytoplasmic plaque, extending through the membrane and binding
strongly to cadherins coming through the membrane of adjacent cell.

39. Blistering disease (genetic defects in
desmosomal proteins )
Pemphigus vulgaris or
Pemphigus foliaceus
Bullous pemphigoid

40. Communicating junction: gap junction
Epithelium, CNS, cardiac muscle, smooth muscle
Couple adjacent cells metabolically and electrically
Plaque-like entity composed of CONNEXONS (connexins) which are arranged radially around a central channel
Exact alignment produces a junction where cell-to-cell permit passage of ions and small molecules

41. Gap junctions
Protienaceous tubes that connect adjacent cells. These tubes allow
Material to pass from one cell to next without having to pass through
plasma membranes of cells.
Dissolved substances (eg. Ions, glucose) can pass easily.

43. Hemidesmosomes One-half of a desmosomes
Mediate adhesion of the epithelial cells to the underlying matrix
Present on basal surface of basal cells: tracheal epithelium, stratified squamous epithelium, myoepithelial cells
Dense cytoplasmic plaque linked via transmembrane receptor proteins (integrins) to laminins in the basal lamina
Filaments from basal lamina extend into the underlying connective tissue
Keratin filaments in the cell terminate in the hemidesmosome plaque

44. Hemidesmsomes
Points of contact between cell and the extracellular matrix.
Intermediate filaments of the cytoskeleton are inserted into
disc shaped electron dense attachment plaque on the
inside of the cell membrane.

45. Antibodies against hemidesmosome results in Bullous pemphigoid

48. Question
A mother brings her son to the pediatrics clinic. The child rapidly developed extensive blistering of the skin shortly after birth.
He has painful erosions of the oral mucosa and has refused ingestion.
He has also had a history of recurrent infections, with sepsis, on one occasion. Antigen mapping of a skin biopsy shows a split within the lamina lucida of the epidermal basement membrane, and junctional epidermolysis bullosa (JEB) was the diagnosis.
In which specific layer of the accompanying electron micrograph (next slide) would you expect to see the disruption?

49. Question
A mother brings her son to the pediatrics clinic. The child rapidly developed extensive blistering of the skin shortly after birth.
He has painful erosions of the oral mucosa and has refused ingestion.
He has also had a history of recurrent infections, with sepsis, on one occasion. Antigen mapping of a skin biopsy shows a split within the lamina lucida of the epidermal basement membrane, and junctional epidermolysis bullosa (JEB) was the diagnosis.
In which specific layer of the accompanying electron micrograph (next slide) would you expect to see the disruption?

50. Epidermolysis bullosa - blistering of skin

52. Epidermolysis bullosa - blistering of skin
Epidermolysis bullosa simplex the mutation in the genes producing keratin, a fibrous protein in the top layer of skin.
Junctional epidermolysis bullosa the mutation in the genes involved in the formation of thread-like fibers (hemidesmosomes) that attach your epidermis to your basement membrane. Characterized by blister formation within the lamina lucida of the basement membrane zone
Dystrophic epidermolysis bullosa the faulty genes are involved in the production of a type of collagen, a protein in the fibers that attach your epidermis to your dermis. As a result, the fibers are either missing or nonfunctional.

53. Basal Epithelial Surface Junction
Basal Lamina: type IV collagen, laminin, entactin, heparan sulphate
Lamina lucida/lamina densa
Basal lamina + reticular lamina = basement membrane
Basal Membrane infoldings: in ion transport epithelia (kidney)
Deep invagination that compartmentalize mitochondria

54. Basal Laminae
Sheets of extracellular material under the basal surface of epithelial cells, around nerves, muscle and other cells
Very important in epithelial polarization and stability
Meshwork of interwoven 4 nm filaments
Mainly made up of proteoglycans, laminin and type IV collagen
Lamina lucida – 50 nm immediately beneath epithelium
Lamina densa – 50 nm facing the underlying connective tissue
Support the epithelium and also functions as a passive molecular sieve or ultrafilter

57. Basal Laminae
Contains also type VII collagen plus anchoring plaques (more developed in epithelia exposed to mechanical stress)
PAS positive due to its richness in carbohydrates
If basal lamina is destroyed (trauma, infections, burns), the epithelium will not be repaired but substituted with an scar (connective tissue)

58. Composition of Basal Lamina
Collagen type IV - for structural stability
Proteoglycans (heparan sulfate) – negatively charged (highly anionic), attracts cations & water, regulates movements of cations.
Laminin– highly adhesive glycoproteins, bridge between cells and type IV collagen.
entactin & fibronectin – highly adhesive glycoproteins, bridge between laminin and type IV collagen.
- 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.

60. How are cells held to basal lamina?
Hemidesmosomes
Actin Actin binding proteins (vinculin, talin, α actinin)
Integrins (transmembrane pr)
Laminin, fibronectin, entactin
Type VII collagen to underlying connective tissue

61. Histological Structure of base membrane
three layers
lamina lucida or lamina rarae – abuts the epithelium; electron lucent
lamina densa – electron dense; thickest component; often referred to as basal lamina
reticular lamina ( lamina fibroreticularis)

62. GLANDS Are cells or aggregation of cells whose function is secretion.
Exocrine glands release the secretory product via a system of ducts that opens upon one of the surfaces of the body which are in contact with the external world (skin, gastrointestinal tract etc.).
Endocrine glands release their secretory product (typically hormones) into the spaces between the secretory cells (extracellular space) from which it enters the bloodstream.

63. Cord endocrine gland e.g pituitary gland
Follicular endocrine gland e.g thyroid gland

64. Simple tubular-large intestine( crypt of leiberkuhn) and uterine gland.
Simple branched tubular- pyloric gland of the stomach
Simple coiled tubular – sweat glands

65. Simple tubular

66. Coiled tubular

67. compound tubular

68. Secretory Mechanisms
The secretory cells can release their secretory products by one of three mechanisms.
Merocrine secretion corresponds to the process of exocytosis. Vesicles open onto the surface of the cell, and the secretory product is discharged from the cell without any further loss of cell substance.

69. When the cells release their secretory products, the membranes of secretory granules fuse to the cells membrane, and the granule contents spill out of the cell in a process called EXOCYTOSIS.

70. Apocrine secretion designates a mechanism in which part of the apical cytoplasm of the cells is lost together with the secretory product.
This mechanism is used by apocrine sweat glands, the mammary glands and the prostate.
Holocrine secretion designates the breakdown and discharge of the entire secretory cell. It is only seen in the sebaceous glands of the skin.

71. Cellular Adaptations Atrophy – decrease in size and in number
Decrease in size and number of cells
Hypertrophy
Increase in size (volume) of individual cells
Hyperplasia
an increase in number of cells in a tissue or organ, excluding tumor formation, in which the bulk of the part or organ may be increased
Metaplasia
abnormal transformation of an adult, fully differentiated tissue of one kind into a differentiated tissue of another kind; an acquired condition, in contrast to heteroplasia
Heteroplasia
Development of cytologic and histologic elements that are not normal for the organ or part in question, as the growth of bone in a site where there is normally fibrous connective tissue.
Malposition of tissue or a part that is otherwise normal, as a ureter that develops at the lower pole of a kidney
Neoplasia
[neo- + G. plasis, a molding]
The pathologic process that results in the formation and growth of a neoplasm
neoplasm(nŽ‚÷-plazm) [neo- + G. plasma, thing formed] =new growth; tumor
an abnormal tissue that grows by cellular proliferation more rapidly than normal and continues to grow after the stimuli that initiated the new growth cease. Neoplasms show partial or complete lack of structural organization and functional coordination with the normal tissue, and usually form a distinct mass of tissue which may be either benign (benign tumor) or malignant (cancer).
Dysplasia
Abnormal function and shape of tissue
Atrophy – decrease in size and in number
Hypertrophy – increase in size
Hyperplasia – increase in number (excludes tumor formation)
Heteroplasia – development of elements not normal for the actual tissue; tissue malposition (hamartoma)
Neoplasia – uncontrolled and progressive new growth of tissue (I.e., tumor formation)
Dysplasia – cytological term, maturation abnormality

72. Hypertrophy vs atrophy

73. Hyperplasia and hamartoma

74. Metaplasia Transformation of one tissue into another (acquired)
Chronic cigarette smokers
pseudostratified ciliated epithelium transformed to stratified squamous epithelium in bronchi
Chronic Vitamin A deficiency
epithelium of bronchi and urinary bladder replaced by stratified squamous epithelium
Chronic acid exposure, or reflux esophagitis
epithelium of esophagus replaced by simple columnar with mucin secreting cells (similar to stomach)

75. Innervation:
Most epithelial tissues Receive a rich supply of sensory nerve endings from nerve plexuses in the lamina propria.
Renewal of epithelial cells:
Epithelial cells are labile structures whose cells are renewed continuosly by means of mitotic active.
Renewal rate is variable??????