The Pacinian corpuscle functions as a mechanoreceptor that is sensitive to pressure and deep touch. It is located in the dermis, especially in areas like the palms and soles that need sensitivity to deep pressure. The Pacinian corpuscle has concentric layers of connective tissue separated by a gel-like substance, surrounding an unmyelinated nerve ending enclosed in a capsule. This structure allows it to respond to and detect deep pressure or mechanical stimuli on the skin.

1. Your God is only Allah, than Whom there is no other
God. He embraceth all things in His knowledge. TAHA, 98
‫ع‬ِ‫س‬َ‫و‬ َۚ‫و‬ُ‫ه‬ َّ‫َل‬ِ‫إ‬ َ‫ه‬ٰ‫ـ‬َ‫ل‬ِ‫إ‬ ٓ َ‫َل‬ ‫ى‬ِ‫ذ‬َّ‫ل‬‫ٱ‬ ُ َّ‫ٱَّلل‬ ُ‫م‬ُ‫ك‬ُ‫ه‬ٰ‫ـ‬َ‫ل‬ِ‫إ‬ ٓ‫ا‬َ‫م‬َّ‫ن‬ِ‫إ‬ََ
‫ا‬ ً۬‫م‬ۡ‫ل‬ِ‫ع‬ ٍ‫ء‬ ۡ‫َى‬‫ش‬ َّ‫ل‬ُ‫ڪ‬

2. • Histology of the
Integumentary System
Dr. Saima Masood

3. INTEGUMENTARY SYSTEM
• SKIN
• Outer Body covering
heaviest organ
• Accessory structures:
• hair
• nails
• glands
• hooves
• claws

4. Functions of skin
Protection
Synthesizes vitamin D
with UV
Regulates body heat
Prevents unnecessary
water loss
Sensory reception
(nerve endings)
Temperature sensor
SECRETION & EXCRETION

5. –Mammary glands
–Sebaceous glands
–Sweat glands

6. CAMOUFLAGE

7. SPECIES & SEX RECOGNITION

8. FIGHTING STRUCTURES

12. STRATUM BASALE
• Deepest layer of the epidermis
• The single row of cells nearest the dermal boundary
• Germinal layer
– Source of KERATINO-CYTES
– A reserve layer in constant mitosis
– desmosomes.
– hemidesmosomes
• EM—keratin filaments abundant in the cytoplasm, also have
many free ribosomes.

13. LM of Stratum Basale

15. STRATUM SPINOSUM
•Irregularly polyhedral cells.
•Cells still alive and can divide if
necessary.
•Layer is 2-10 cells deep; varies
from place to place
•“Prickle cell” appearance results
from attachments at desmosome.

16. Stratum Spinosum-EM
– EM—increase in number of desmosomes with
increased cytoplasmic bundles (tonofibrils)
• Membrane coating granules (MCG)/Lamellar Granules
appear in the cytoplasm of keratinocytes in upper
layers of stratum spinosum.
– First appear near the golgi Apparatus

17. EM of stratum spinosum

19. STRATUM
GRANULOSUM
• LM structure:
• Third layer.
• Large Basophilic cells
• Several layers of flattened cells.
• EM sructure:
• Non-membrane bounded Keratohyalin granules.
• profilaggrin
• Filaggrin Keratinization
• Lamellar granules(coating plasma lemma)

20. EM- St.Granulosum
– EM—KHGs are large, irregularly shaped not
bounded by cell membrane, MCGs more
numerous, migrate to periphery.
• So have both keratohyalin granules AND MCGs.
• Lipids and Hydrolytic Enzymes.

21. LM stratum granulosum

22. Stratum lucidum
Clear Layer:
– LM—nuclei not evident in flattened cells with
pale if any staining
– EM—organization of keratin filaments more
regular.

23. STRATUM LUCIDUM
• Not always present
• Thick skin.
• Hairless regions.
• Clear lucent band

24. STRATUM CORNEUM
• From Latin, cornus = “horn”
• Cells can no longer divide.
• LM_
• cells flattened and scale like.
EM-
Filling with keratin fibers and “keratohyaline granules”
– -Appear clear
– No nucleus No cytoplasmic organelles.
• Stratum Disjunctum
• No of layers varies among species and body regions.

26. • The outermost layer of the
stratum corneum
• Sloughing and desquamating
dead cells
• Large animals may lose up to 1
kg per day of skin cells
• “Dandruff” is produced here!
“STRATUM DISJUNCTUM”

28. • Epidermal ridges or pegs
• Dermal Papilla

29. Epidermal pegs & Dermal papilla

30. MELANOCYTES
• Source of MELANIN
• Of neural crest origin
• Location:
_ have spherical nucleus and Typical organelles.
NOT part of keratinizing system
– Less than 10% of the stratum basale.
– Two types of melanin_ Eumelanin & Pheomelanin.
– Contains unique pathway with TYROSINASE.
– Tyrosine DOPA dopaquinone
Melanin

31. MELANOCYTE
Extensive branching
processes
Produces melanin and
releases it in packets
Packets are engulfed by
keratinocytes:
“crinophagy”
Melanin carried up to
surface and lost in
sloughing

33. Melanocytes
• Where do they originate from?
• How do they deliver melanosomes? What is
the process called?
• What are melanosomes?

34. Langerhans Cells
• Macrophage of the skin
• Most frequent in the stratum spinosum
• Langerhans cells (LC) are dendritic,
antigenpresenting cells (APC), function as the
“outermost arm” of the immune system.
• .

35. Langerhans cell
constitute 2-8%
History:
•Paul Langerhans in 1868.
•In 1961,ultra-structural characteristics - Birbeck.et.al.
•The Birbeck„s granule serves as element for
morphological identification of the LCs.

36. Origin:
•From bone marrow

37. •The Birbeck granules seem to be specific markers of LCs.
•Based on electron microscopy, two types of LCs:

38. Location

39. Merkel cell/Tactile Epitheliod cell
folded nucleus, a clear, organelle-rich cytoplasm with
peripheral protrusions among the epithelial cells, few
desmosomal attachments
found in basal and spinous layer of epithelium.
History:
In 1875, Friedrich Sigmund Merkel, in base
of the epidermis of
skin called -touch cells.

41. Merkel cells (contd.)
• MCs differ from other non-keratinocytes – not
dendritic.
• High numbers in the lip, anterior hard palate
and gingiva.
• In oral mucosa in recognition of particle size
and texture during mastication.

42. DERMIS

45. • Tactile corpuscles (or Meissner's corpuscles)
are a type of mechanoreceptor.
• They are a type of nerve ending in
the skin that is responsible for sensitivity to
light touch.
• They are distributed on various areas of
the skin, but concentrated in areas especially
sensitive to light touch, such as
the fingers and lips.

47. The Pacinian corpuscle.
Located in the dermis of the skin, especially in the palm
of the hands, fingers and the underside of the feet; also
found in joints and tendons and the external genitalia.
Called a mechanoreceptor responding to mechanical
stimuli; sensitive to pressure i.e. something pushing hard
on the skin.
Example of a
simple receptor

48. Concentric layers of connective
tissue separated by a viscous gel
surround the un-myelinated end of
the dendron of a sensory neurone
enclosed in a capsule (in section it
looks like a section through an
onion bulb). Normally round in
section when at rest.
Structure of a Pacinian corpuscle
Read the article.
Summarise how the Pacinian corpsucle functions as a
sensory receptor.

52. • Arrector pili muscle: consists of smooth
muscle. Contraction leads to erection of hair
shaft and can cause "gooseflesh".
• Lower portion: hair bulb - papilla and matrix.
Melanocytes located in the matrix produce
hair color.

53. • The dermal papilla consists of a specialized
group of fibroblasts and has an inductive
action on the epidermis promoting
proliferation and differentiation.

55. *Dermal papillae
*Dermis layers

59. LM of Stratum lucidum and stratum corneum

61. Sebaceous glands