The skin is the largest organ of the body and has several important functions including protection, regulation, sensation, and synthesis. The skin helps diagnose some diseases based on its appearance and has some medico-legal functions. There are two main types of skin: thick and thin. Thick skin is found on the palms, soles, and tips of fingers and toes, while thin skin is found all over the body. Thick skin contains two main layers, the epidermis and dermis. The epidermis contains five layers of keratinized stratified squamous epithelium composed mainly of keratinocytes.

2. The SKINThe SKIN
Dr. Samar AskerDr. Samar Asker

3. The largest organ in
the body

4. Protection
Regulation
Excretion
Synthesis
Receive sensation
Medico legal
functions

5. Diagnose
some diseases
as :
 Measles
 anemia
 Jaundice
 chicken pox.

6. Types of the skin
 Thick skin
Palm, sole, tips of
Fingers& toes
 Thin skin
All over the body

8. Thick skin
Formed of
epidermis
& dermis.
The epidermis
keratiniezed
str.sq.epith
formed of.
Keratinocytes & non
Keratinocytes

9. The Keratinocytes:
85% of cells of
epidermis form
keratin 5 layers .
1
2
3
4
5
•Basal layer
together with
Spinous layer are
called malpighian
layer

10. Basal cell layer or Germinal l.
LM:
•Single layer of columnar cells resting
on clear wavy basement membrane .
Have basal oval nucleus & basophilic
Cytoplasm.
•The nuclei show mitotic figures for
renewal which take place every 2-4
weeks mostly at night
.

11. EM:
•Cells are joined
together by
“desmosomes”
• to the basement
membrane by
“hemidesmosomes”.
•Rich in ribosomes
and polysomes

12. •Melanocytes
•Merkels
cells are
present in
this layer.

13. Spinous layer or Prickle cell l.
LM:
•4-8 layers of polyhedral cells
with central and rounded
nuclei.
•They have spine-like
processes indicating sites of
desmosomes as cells shrink
during preparation.

14. EM:
•The cells are joined by
“desmosomes” & have
interdegitating cell membrane.
•The superficial cells contain
membrane bound (coated)
lamellar granules.
•Langerhans cells are
present in this layer