Histology

1. EPITHELIAL CELL SURFACE
SPECIALIZATION
Dr. Rabia Inam Gandapore
Assistant Professor
Head of Department Anatomy
(Dentistry-BKCD)
B.D.S (SBDC), M.Phil. Anatomy (KMU),
Dip. Implant (Sharjah, Bangkok, ACHERS) , CHPE
(KMU),CHR (KMU), Dip. Arts (Florence, Italy)

2. Teaching Methodology
 LGF (Long Group Format)
 SGF (Short Group Format)
 LGD (Long Group Discussion, Interactive discussion with the use of models or diagrams)
 SGD (Short Group)
 SDL (Self-Directed Learning)
 DSL (Directed-Self Learning)
 PBL (Problem- Based Learning)
 Online Teaching Method
 Role Play
 Demonstrations
 Laboratory
 Museum
 Library (Computed Assisted Learning or E-Learning)
 Assignments
 Video tutorial method

3. Goal/Aim (main objective)
 To help/facilitate/augment the students about the:
1. Describe the surface specialization of epithelia
2. Correlate their structure, with their location and function.

4. Specific Learning Objectives (cognitive)
At the end of the lecture the student will able to:
 Recognize the Histological features of :
Apical Domain: Microvilli, Cillia, Stereocillia
Lateral Domain
Basal Domain: Basal Lamina (Lamina Lucida, Lamina Densa),
Hemidesmosomes, Infoldings of Plasmalemma
 Sketch labeled diagram of Cell Surface Specialization

5. Psychomotor Objective: (Guided response)
 A student to draw labelled diagram of Cell Surface Specialization

6. Affective domain
 To be able to display a good code of conduct and moral values in the class.
 To cooperate with the teacher and in groups with the colleagues.
 To demonstrate a responsible behavior in the class and be punctual, regular, attentive and
on time in the class.
 To be able to perform well in the class under the guidance and supervision of the teacher.
 Study the topic before entering the class.
 Discuss among colleagues the topic under discussion in SGDs.
 Participate in group activities and museum classes and follow the rules.
 Volunteer to participate in psychomotor activities.
 Listen to the teacher's instructions carefully and follow the guidelines.
 Ask questions in the class by raising hand and avoid creating a disturbance.
 To be able to submit all assignments on time and get your sketch logbooks checked.

7. Lesson contents
Clinical chair side question: Students will be asked if they know what is the function of
Outline:
 Activity 1 The facilitator will explain the student's to describe the surface specialization of
epithelia
 Activity 2 The facilitator will ask the students to make a labeled diagram of the Correlate their
structure, with their location and function
 Activity 3 The facilitator will ask the students a few Multiple Choice Questions related to it with
flashcards.

8.  Students assessment: MCQs, Flashcards, Diagrams labeling.
 Learning resources: Langman’s T.W. Sadler, Laiq Hussain Siddiqui, Snell Clinical Anatomy, Netter’s
Atlas, BD Chaurasia’s Human anatomy, Internet sources links.

9. Polarity of Epithelial Cells
1. APICAL DOMAIN
2. LATERAL DOMAIN
3. BASAL DOMAIN

10. Polarity of Epithelial Cells
 Most epithelial cells polarized because
distinct morphological & biochemical
characteristics are associated with
different surfaces of these cells.
 3 domains related to surfaces of cell
1. Apical Domain
2. Lateral Domain
3. Basal Domain

12. Apical Domain
 MICRO-VILLI
 CILLIA
 STEREOCILLIA

13. Apical Domain
 Region of epithelial cell facing lumen of an enclosed
cavity or a tube
 Contains:
1. Ion channels
2. Carrier proteins
3. Hydrolytic enzymes
4. Aquaporins
(Channel-forming proteins helps in regulation of water
balance)
 It shows special structural modifications which enable
it to carry out its functions
1. Mirco-villi
2. Cilia
3. Stereocilia

14. 1. Micro-Villi
 Shape & Size: Small , Slender, Finger like projections
 Found: on free surface of epithelial cells
 LM: cannot be seen
 EM:
 are plasma membrane-covered cytoplasmic extensions
 Height:1-3µm
 Diameter: 0.1µm
 Each microvillus contains= central bundle 20-30 microfilaments (Actin) which are cross linked at regular intervals
by actin binding proteins
1. Facin
2. Fimbrin
 Microfilaments= are anchored to plasma membrane at top & sides of microvillus
 It extends down into the apical cytoplasm & become embedded in the terminal web within it the actin filaments
become associated with the molecules of spectrin & myosin-II

16. FILAMENTS IN MICROVILLI & TERMINAL WEB

17. Example:
1. Columnar epithelilal cell lining lumen surface of small
intestine and LM shows microvilli as striated border
2. Luminal surface of cells lining proximal convoluted
tubules of kidney and LM shows mircovilli appear as brush
border
Function:
 Absorptive function (oscillatory contractile movement of
microvilli)
 Increase in surface area of cells

18. MICROVILLI & STRIATED BORDER

19. MICROVILLI & BRUSH BORDER

20. 2. Cilia (Kinicillia)
 Hair like processes, Motile
 Found on free surface of epithelial cells specialized for
transport of fluid or film of mucus over epithelial surface
 Called kino-cilia due to TO-&-FRO oscillatory movement
 LM: visible
Length= 5-10µm
Diameter= 0.2µm
 Location: Human body fond on
1. Respiratory tract: on tall cells of pseudo-stratified columnar
epithelium of conducting part of RT
2. Uterine tube: Simple columnar lining UT
3. Internal Ear: Neuro-epithelial cells (Hair-cells) of sensory
regions (Maculae & Cristae)

21. CILIATED CELLS & NON-CILIATED GOBLET CELLS

22. CILIATED CELLS & NON-CILIATED GOBLET CELLS

23. CILIATED CELLS & NON-CILIATED GOBLET CELLS
MV=Microvillus; B=Basal body;

26.  EM: Shaft (Free part of each cilium) contains a core complex or
axoneme that’s enclosed by a plasma membrane which at the base of the
cilium becomes continuous with plasma membrane of the cell from which
the cilium arises
 Axoneme consists of longitudinal microtubules arranged in 9+2 pattern
 9 doublet micro-tubules surrounding central microtubules are
separated from each other; enclosed within thin central sheath
 Each 9 double micro-tubules consists of 2 members designated A & B
1. Micro-tubule A: is complete & its wall consists of 13 proto-filaments.
2. Micro-tubules B: wall of has 10 protofilaments & share 3 proto-filaments
of wall of micro-tubule A

28. Basal body
9+2

30.  Adjacent doublets are linked to eachother by thin
protein bridges called Nexins
 A microtubule of 9 doublets is connected to central
sheath by a Radial spoke that is composed of an
electric protein.
 Outer surface of A microtubule are present tiny hook-
like arms, which are made up of motor protein dynein
 When activated by ATP, these dynein arms make
temporary cross-bridges with microtubules B of
adjacent doublet. This results in ciliary movement by
sliding of doublets relative to each other

31.  Microtubules extend from tip of
cilium to its base, which is known as
basal body & is located inside free
surface of cell
 Basal body has same structure as
that of a centriole
 Centriole: has a wall of circularly
arranged 9 triplet microtubules, but
no central microtubules (9+0
pattern)
 Cilium joins a basal body, 2 central
microtubules of axoneme of cilium
terminates at base & peripheral 9
doublets become continuous with 9
triplets micro-tubules of basal body

32. Functions
 Kinocilia beats rapidly in specific direction
 Each kinocilium stiffens during more rapid forward or effective
stroke & bends during slower recovery stroke
 Successive cilia in each row begin their beat in sequence so that
each is slightly more advanced in its movement than cilium behind it
in that row.
 This sequential activation of cilia results in the formation of waves
that sweeps slowly over the epithelial surface resulting in propulsion
of a layer of
1. Mucus
2. Fluid
3. Particulate matter
4. Ovum over the epithelium
 Kinocilia of hair cells of vestibular apparatus of ear perform
function of transduction of mechincal stimuli into electrical impulses

33. 3. Stereo-cilia (Stereo-villi)
 Stereo= Solid , non motile
 LM: Thin, Hair like structure in contact with
each other forming small tufts
 Resemble cilia but different due to their
incapability to exhibit movements in living
cells
 EM: long microvilli containing central
bundle of microfilaments
 Long , flexible and wind around each other
towards tip (tuft appearance)
 Length= 30µm

34. Example:
1. Lining duct of epididymis
2. Vas deferens
3. Neuroepithelial & sustentacular cells of taste buds
4. Internal Ear-Neuroepithelial cells (hair cells) of
maculae, cristae & organ of corti
Functions
1. Increase surface area
2. Re-absorptive process
3. Nerve signal generation

35. STEREOCILIA
IN EPIDIDYMIS

36. Hair cell stereocilia inside ear

37. Lateral Domain

38. Lateral Domain
 Epithelial tissues= closely packed cells, hence,
lateral domain of each epithelial cell lies in close
contact with lateral domain of neighboring cells.
 Functions:
1. Cell adhesion: dependent on 3 factors
a. Presence of cadherins (adhesive glycoproteins)
b. Presence of invaginations & evaginations
c. Presence of adhering & occluding cell junctions.
2. Cell Communication: Gap junctions (nexus)
between cell to cell communication

42. Basal Domain
 BASAL LAMINA (LAMINA LUCCIDA, LAMINA DENSA)
 HEMIDESMOSOMES
 INFOLDINGS OF PLASMALEMMA

43. Basal Domain
 Characterized by:
1. Basal Lamina (Basement membrane): Thin layer of extracellular material ,
located between epithelial cells & underlying connective tissue.
2. Hemidesmosomes: are junctions that anchor epithelial cell to basal lamina
3. Infoldings of plasmalemma: feature of epithelial cells involved in ion
transport. cells show multiple infoldings of basal plasma membrane with
vertically oriented mitochondria giving striated appearance to basal regions
under LM
Function
a. Increase surface area
b. Increase number of mitochondria that helps in active transport of ions
Example:
1. Proximal & Distal convoluted tubules of kidney
2. Ducts of salivary glands called striated ducts

45. Functions of Epithelium

46. Functions
 Protection
 Secretion
 Absorption
 Excretion
 Transport
 Sensory Reception

47. Thank You
ANY QUESTIONS?