1. Salman Bin Abdulaziz university
Skin appendages
Dr. Salman Bin Dayel, M.D
College of Medicine
Salman Bin Abdulaziz university

2. Skin appendages: Hair follicles Sebaceous glands Eccrine sweat glands
Apocrine sweat glands
The nails

3. The Hair:

4. Biology Of Hair: Functions of hair: (1) Psychological importance.
(2) Scalp hair excellent protection from actinic damage.
(3) involved in sensory reception .
(4) play a role in epidermal homeostasis, wound healing, skin tumorigenesis.

5. Embryology: * The first hair follicles form at 9 weeks' gestation.
* they are distributed mainly in the
(1) eyebrows, (2) upper lip, (3) chin.
* The rest of the follicles begin to develop at 4 to 5 months gestation in a cephalo caudal direction .

6. Anatomy of hair follicle:
(1) The outer root sheath: most peripheral cellular compartments of follicle .
(2) Companion layer:
 between ORS & henle layer of IRS.
(3) Inner root sheath(IRS):
1- Henle layer.  outer most .
2- Huxley layer.  it is the major component of IRS.
3- cuticle of IRS.  inner most & adjacent to hair shaft..
(4) Hair shaft: Innermost part of hair.
1- cuticle.
2- cortex.
3 - medulla.

8. Hair Cycle:

9. The Hair Cycle: anagen (growth stage) :
* Length of the hair depend on anagen phase .
* Length of anagen vary depend on body site as follow:
Scalp  2-6 years.
Upper lip  4-14 weeks
Arms  6-12 weeks.
Legs  weeks.

10. (2) Catagen (degenerative stage):
the follicle enter into catagen which show changes that are associated with programmed cell death and apoptosis.
catagen lasting only about 2 weeks.

11. (3) Telogen (resting stage):
* The inner root sheath is totally absent from the telogen follicle.
Telogen period last for 1-3 months on human scalp.

12. 85-90 % of scalp hair follicles are anagen,
At any one time,
85-90 % of scalp hair follicles are anagen,
13 % are in telogen,
less than 1 % are in catagen.

13. Hair Pigmentation:
Only when hair grows (anagen stage), because follicular melanocytes are active only in anagen stage.
The pigment is located in the cortex of the hair shaft.

14. Types of Hair:
(1) lanugo hair: soft, fine hair that covers much of the fetus and is shed during st weeks of life.
(2) Vellus hair (follicle): very short, non pigmented,
No medulla,
absence of arrector pili muscle,
Less than 1cm length.
(3) Terminal hair: large, pigmented & medulated.
Grow more than 1 cm.

16. Distribution of Hair
Hair follicles are distributed throught body except : palms , soles , and portion of genitalia ( called Glabrous Skin )
The Highest Density on the Scalp
Total number ~ (mostly vellus)
Number of scalp hair follicles ~ ( Blondes: + 20% ,Redheads: – 20% )

18. Biology of The Nails

19. Anatomy of the Nail: The nail cosist of: (1) A horny 'dead' product
(the nail plate).
(2) Four specialized epithelia:
 the proximal nail fold.
 the nail matrix.
 the nail bed.
 the hyponychium.

21. The nails functions: (1) aesthetic appearance of the hands.
(2) Protecting the distal phalanges.
(3) Enhancing tactile discrimination and the capacity to pick up small thing
(4) Use for scratching and grooming.

22. Nail Plate:
* it is a fully keratinized structure that is continuously produced throughout life.
* is firmly attached to the nail bed.
* At the tip of the digit, the nail plate separates from the underlying tissues at the hyponychium.

23. The lunula: * whitish, half moon–shaped area, on proximal parts of the fingernails.
*The most loose part of attachment to nail bed.

25. Cuticle:
* It is formed by horny layer of proximal nail fold.
* It is firmly attached to superficial nail plate & prevent separation of plate from nail fold.
Nail Matrix:
is a specialized thick epithelial structure that lies above the midportion of the distal phalanx.
it consists of a proximal (dorsal) & a distal (ventral) portion.

26. Nail Bed:
* extends from the distal margin of the lunula to the onychodermal band.
* it is completely visible through the nail plate.
The nail bed epithelium is so adherent to the nail plate

27. Nail Growth : 3 mm per month for fingernails
The nail plate grows continuously during life.
Fingernails grow faster than toenails, mean growth
3 mm per month for fingernails
1 mm per month for toenails.
Complete replacement of the nail requires: fingernail 100 to 180 days (6 months)
toenail 12 – 18 months.

29. Factors influence nail growth:

30. Biology of Sweat Glands

31. Eccrine sweat glands:
---> 2 to 4 million glands distributed over entire body.
---> highest density of eccrines on palm & soles. (620/cm2)
---> less on back (64/cm2).
--->Failure of Eccrine sweating: can lead to heat exhaustion, heat stroke, and death.

33. Apocrine Sweat Gland:
Found mainly  axillae , periumbilical , nipples & anogenital.
* It consist of 1) secretory portion : located in deeper dermis.
2)stretched duct: open into upper portion of follicular canal
* Its secretion is controlled by adrenergic nerves.

35. Sebaceous Glands: Distribution is almost associated with hair follicle
Sebaceous glands are located throughout
the entire body except:
1-palms, soles,
3-dorsa of the feet, lower lip.
They are largest and most numerous
on the face, chest, back, and
upper outer arms.

36. Sebaceous follicle consist of :
(1) Keratinized follicular infundibulum (3) sebaceous gland.
(2) The hair (4) sebaceous duct.

37. Thank you