1. Hair follicle

3. Papilla
• The papilla is a large structure at the base of
the hair follicle.
• The papilla is made up mainly of connective
tissue and a capillary loop.
• Cell division in the papilla is either rare or nonexistent.

5. Matrix
• Around the papilla is the hair matrix, a
collection of epithelial cells often interspersed
with the pigment-producing
cells, melanocytes.
• Cell division in the hair matrix produces the
cells that form the major structures of the hair
fiber and the inner root sheath.

7. • The hair matrix epithelium is one of the
fastest growing cell populations in the human
body, which is why some forms
of chemotherapy or radiotherapy, that kill
dividing cells, may lead to temporary hair loss.
• The papilla is usually ovoid or pear shaped.

9. • The matrix wraps completely around it, except
for a short stalk-like connection to the
surrounding connective tissue.
• This provides access for the capillary .

11. Root sheath
• The root sheath is composed of an external
and internal root sheath.
• The external root sheath appears empty with
cuboid cells when stained with H&E stain.
• The internal root sheath is composed of three
layers, Henle's layer, Huxley's layer, and an
internal cuticle that is continuous with the
outermost layer of the hair fiber.

21. • Lamellar corpuscles, or Pacinian corpuscles,
are nerve endings in the skin responsible for
sensitivity to vibration and pressure.
• The vibrational role may be used to detect
surface texture, e.g., rough vs. smooth.

22. • Hair fiber
• The hair fiber is composed of keratin.

23. arrector pili muscles
• These are small muscles attached to hair
follicles in mammals. Contraction of these
muscles causes the hairs to stand on end.
• Each arrector pili is composed of a bundle
of smooth muscle fibres which attach to
several follicles (a follicular unit), and is
innervated by the sympathetic branch of
the autonomic nervous system.

24. • The contraction of the muscle is therefore
involuntary - stresses such as cold, fear etc.
may stimulate the sympathetic nervous
system and thus cause contraction, but the
muscle is not under conscious control.

25. sebaceous glands
• These secrete an oily/waxy matter,
called sebum, to lubricate and waterproof the
skin and hair
• They are found in greatest abundance on
the face and scalp, though they are distributed
throughout all skin sites except the palms and
soles.

26. Sweat glands
• There are two main types of sweat glands:
• Eccrine sweat glands are distributed almost all
over the body, though their density varies
from region to region.
• Humans utilize eccrine sweat glands as a
primary form of cooling.

27. • Apocrine sweat glands are larger, have a
different secretion mechanism, and are mostly
limited to the axilla (armpits) and perianal
areas in humans.
• Although apocrine glands contribute little to
cooling in humans, they are the only effective
sweat glands in hoofed animals such as
the camel, donkey, horse, and cattle

28. • Apocrine is a term used to classify exocrine
glands in the study of histology.
• Cells which are classified as apocrine bud their
secretions off through the plasma membrane
producing membrane-bound vesicles in the
lumen.

29. • This method is also called decapitation
secretion.
• The apical portion of the secretory cell of the
gland pinches off and enters the lumen.

30. • Apocrine secretion is less damaging to the
gland than holocrine secretion (which
destroys a cell) but more damaging
than merocrine secretion (exocytosis).
• An example of true apocrine glands are
mammary glands, responsible for secreting
breast milk