Histology of skin

1. Histology of Integumentary
System
Faseeh

2. INTEGUMENTARY SYSTEM
• The skin or cutis covers the entire outer
surface of the body.
• Structurally, the skin consists of two layers
which differ in
– Function
– Histological appearance
– Embryonic origin

3. outer layer or epidermis
• formed by an epithelium and is of ectodermal
origin
– Stratified squamous keratinized epithelium
– Two Types of cells
• Keratinocyte
• Non-Keratinocytes
• Five structurally different layers can be identified:
1. stratum basale
2. stratum spinosum
3. stratum granulosum
4. stratum lucidum
5. stratum corneum

4. • Stratum Basale (stratum germinativum)
– deepest layer of the epidermis (closest to the
dermis)
– single layer of columnar or cuboidal cells which
rest on the basement membrane.
• stratum spinosum
– cells become irregularly polygonal.
– cells are often separated by narrow, translucent
clefts.
– clefts are spanned by spine-like extensions of the
cells (hence the name of the layer and of its cells:
spinous cells), which interconnect the cells of this
layer.

5. • stratum granulosum
– cytoplasm of the cells contains numerous fine grains,
keratohyalin granules.
– consists, in thick skin, of a few layers of flattened cells.
Only one layer may be visible in thin skin.
• stratum lucidum
– consists of several layers of flattened eosinphilic dead
cells.
– only seen in thick skin.
• stratum corneum
– cells are completely filled with keratin filaments.
– The protection of the body by the epidermis is essentially
due to the functional features of the stratum corneum

9. Dermis
• The dermis is the thick layer of connective tissue
to which the epidermis is attached.
• The dermis may be divided into two sub-layers
(without a sharp boundary)
• papillary layer
– Thinner compare to Reticular layer
– comparatively cell-rich connective tissue, which fills
the hollows at the deep surface (dermal papillae) of
the epidermis.
– Capillaries are frequent. Collagen fibres appear finer
than in the reticular layer.

10. • Reticular layer
– Thicker compare to Papillary layer
– Appears denser and contains fewer cells.
– Thick collagen fibres (5-10 µm) often aggregate
into bundles.
– The fibres form an interlacing network, although
their predominant direction is parallel to the
surface of the skin.
Dermis

13. Epidermal Appendages
• Epidermal appendages are intradermal
epithelial structures lined with epithelial cells
with the potential for division and
differentiation.
• Epidermal appendages include the following:
– Sebaceous glands
– Sweat glands
– Hair

14. Hair
• Hair follicles are complex structures
formed by the epidermis .
• They are found over the entire surface
of the body except the soles of the
feet, palms and external genitalia.
• Hairs are made of dead keratinised
cells.
• The two regions of a hair are:
– the shaft
• It is the portion of the hair that projects
from the surface of the skin.
– the root
• It is the portion of the hair embedded in the
skin. It extends from the epidermal surface
into the dermis but in the scalp, it can
extend into the hypodermis.

15. Hair
• The hair (shaft and root) is made of three tubes
that fit into each other. The three tubes are made
of keratinised cells.
– The outer tube is the cuticle
– The middle tube is the cortex
– The inner tube is the medulla
• The base of this hair follicle expends forming the
hair bulb.
• Associated with each hair follicle is a tiny band of
smooth muscle: the arrector pili. This band of
smooth muscle is attached at one end to the
papillary layer of the dermis and at the other to
the connective tissue root sheath of the follicle.

20. SEBACEOUS GLANDS
• Sebaceous glands are embedded in
the dermis over most of the body
surface, except the thick, hairless
(glabrous) skin of the palms and
soles.
• Sebaceous glands are branched
acinar glands with several acini
converging at a short duct which
empties into the upper portion of a
hair follicle.
• The acini consist of a basal cells,
undifferentiated flattened epithelial
cells.
• differentiated and distinctly large,
lipid-producing sebocytes.

22. Sweat Glands
• Sweat glands are epithelial derivatives
embedded in the dermis which open to the
skin surface or into hair follicle.
• Two types
– Eccrine sweat glands
– Apocrine sweat glands

23. • Difference between Eccrine &
Apocrine Sweat gland
• Difference between Secretory and
Excretory (ducts) Units of Sweat
glands
For Answer see details in Chapter
Integumentary System

27. Online Resource Material Links
• http://emedicine.medscape.com/article/1294
744-overview#a1
• http://www.zoology.ubc.ca/~biomania/tutoria
l/skin/outanc19.htm
• http://www.lab.anhb.uwa.edu.au/mb140/cor
epages/integumentary/integum.htm
• http://www.histology.leeds.ac.uk/skin/skin_la
yers.php