The document discusses the anatomy and physiology of the hair and skin, including the three main layers of the skin - epidermis, dermis, and subcutis. It describes the structure and functions of hair follicles, sebaceous glands, sweat glands, and melanocytes. Additionally, it outlines the three stages of hair growth - anagen, catagen, and telogen - and lists the major functions of the skin like protection, temperature regulation, secretion, and absorption.

1. Anatomy and Physiology of the Hair
and Skin

2. Learning Objectives
1.) Name the layers of the epidermis.
2.) Name appendages within the dermis.
3.) List the major functions of the skin.
4.) Name components of the pilosebaceous unit.
5.) Name the three stages of hair growth.

3. Integumentary system
The skin and its accessory organs
Sebaceous glands
Sudoriferous glands
Sensory perceptors
Hair
Nails

4. Pilosebaceous unit
The hair follicle and its appendages
Internal and external root sheaths
Hair shaft
Dermal papilla
Sebaceous gland
Arrector pili muscle

5. Overall Look at Skin
Body’s largest organ
Up to 20 square feet on the average person
Made of epithelial tissue and connective tissue
Epithelial – forms thin protective layer
Connective – binds, protects, cushions, & supports
3 main layers
Epidermis
Dermis
Subcutis or subcutaneous layer

6. Epidermis
“Horny Zone” Cells divide in the lowest
Stratum Corneum layer
Migrate up to replace dead
Stratum Lucidum
cells that have been shed
Stratum Granulosum As they move up, they are
“Germinal Zone” filled with keratin to protect
Stratum Spinosum against invasion
(keratinization)
Stratum Germinativum

7. Stratum Corneum
A.K.A – “horny layer”
Outermost layer of dead skin cells
Constantly shedding
Mostly bound by sebum
Sebum – fatty or oily secretion of sebaceous gland; serves as
lubrication

8. Stratum Lucidum
Below stratum corneum
Cells allow light to pass through them
Only present in palms of hands and soles of feet, where
epidermis is thickest
Purpose unknown

9. Stratum Granulosum
AKA – “granular layer”
Cells are living
As cells are pushed upward, lose nuclei and die
Gives skin opaque appearance
Varies in thickness
Persistent friction and pressure cause areas to thicken for
protection and form calluses

10. Stratum Spinosum
AKA – “Prickle cell layer”
Made of living cells
Attached to each other by prickly shaped fibers

11. Stratum Germinativum
Lowest layer of epidermis
Mitosis (cell division) occurs here
Cells migrate up, replacing dead skin cells that have been
shed
Desquamation (exfoliating dead skin cells) takes about 28
days
Stratum mucosum – single cell layer

12. Stratum Germinativum
Contains melanocytes
UV rays react with amino acid tyrosine found in melanocytes to
produce melanin
Melanin
Dark pigment gives skin color and protects dermis from UV
radiation and sun damage

13. Skin Color
Skin color depends on melanin
People have same number of melanocytes
Dark skin – melanocytes are more active, producing more
melanin

14. Dermis
Living layer or “true skin”
Made of dense connective tissue
Divided into two layers
 Papillary layer
 Reticular layer

15. Papillary layer
Made of fibers called papillae
 Connects epidermis and dermis
Superficial capillaries looped around papillae
Nerve endings sensitive to touch
This layer forms the connective tissue sheath around hair
follicles.

16. Reticular Layer
Thickest layer of skin
Dense bundles of collagen fibers
Fibers are denser closer to papillary layer and thin as they near the
fatty subcutaneous tissue
Appendages
Arrector pili muscles
Blood vessels
Fat cells
Hair follicles
Lymph vessels
Nerve endings
Sebaceous glands
Sudoriferous glands

17. Blood Supply
Arteries and veins circulate into the dermis and branch into
smaller capillaries at the hair follicles, the hair papillae, and
glands
Transports oxygen-rich blood and nutrients essential for:
Growth
Reproduction
Tissue repair

18. Lymph Supply
Lymph glands produce lymph
Contains waste products, salts, nitrogenous wastes
Carried through vessels to lymph nodes and fluid is filtered for
excretion

19. Sudoriferous Glands
Sweat glands
Found deep in dermis
Tubular ducts going to pores in epidermis
Two kinds of sweat glands:
 Apocrine
 Eccrine

20. Types of Sudoriferous Glands
Apocrine
 Found in genital area and armpits (axillae)
 Create body odor
 Believed to excrete pheromones
Eccrine
 Found all over body
 Increased numbers on forehead, palms, soles of feet

21. Sebaceous Glands
Found all over skin
Most often appendages to the hair follicles and open into the
shafts of the follicles
Produce waxy, oily substance called sebum which lubricates
skin
 Most active during puberty

22. Nerve Endings
Carry impulses to the brain
Found at various levels, various shapes, depending on
purpose
Most superficial are responsible for touch
Close to surface is pain receptor
 Below that are receptors for heat and cold
Deeper in dermis are pressure receptors

23. Hair
 AKA – pilosebaceous unit
 Found all over body except palms of hands and soles of feet
 Most is invisible to naked eye
Denser on head and limbs, after puberty in groin area and
axillae (armpits)
 Hair growth influenced by hormones and genetic inheritance

24. Subcutaneous Layer
Located at base of dermis
Layer of fatty tissue
AKA – subcutis; adipose tissue
Separates dermis from muscles and helps skin to move over
them
Contains arteries, veins, lymph, nerve endings, fat cells

25. Structure of Hair – Follicular Canal and
Sheaths
Follicular canal –
depression in the
skin that houses the
hair
External root sheath
– inner side of canal

26. Hair Shaft
Lined with epidermal tissue extends through dermis into
subcutaneous tissue
Epidermal cells produce follicle and hair matrix
Base of follicle widens into hair follicle bulb
Bulb – where hair grows; contains hair matrix which is where cell
division occurs
Hair matrix produces the hair and external and internal root sheath

27. Internal Root Sheath
Innermost layer of the
follicle
Can sometimes see on
tweezed hair
 Looks like clump of
petroleum jelly
Protects hair up as far as
sebaceous gland

28. Dermal Papilla and Papillae
Dermal papilla – located at base of bulb
 Layer of dermal tissue that attaches itself to the epidermis with
papillae
Papillae contain blood vessels – needed for nutrients and
hormones for growth

29. Arrector Pili Muscle
Attaches to the underside of the hair at the dermal papilla
and the hair shaft
Responsible for lifting the hair, trapping a layer of air on the
skin’s surface
 assisting in heat regulation
 fear and cold stimulate contraction
 causes “goose bumps”

30. Sebaceous Gland
Attached to hair follicle and opens into shaft
Secretes sebum
 Lubricates hair to prevent dryness and breakage
 Lubricates epidermis to prevent dryness and to prevent
bacteria and germs from entering

31. Layers of the Hair
3 layers compose the hair:
1.) Cuticle
2.) Cortex
3.) Medulla

32. Cuticle
Outermost layer
Purpose: protect inner layers of the hair

33. Cortex
Below the cuticle
Contains pigment that gives hair its color
Gives hair its strength and elasticity

34. Medulla
Innermost layer
AKA – pith or marrow
Fine hair lacks medulla
Can be found in all wavy hair
General rule: curlier the hair, the stronger the medulla

35. 3 Types of Hair
1.) Lanugo
2.) Vellus
3.) Terminal

36. Lanugo
AKA – fetal hair
Soft, downy hair on fetuses in utero and infants at birth,
covering bodies and scalp
May contain pigment, light or dark
Sheds a few weeks after birth
Permanent hair begins to grow in

37. Vellus – “peach fuzz”
Confused with lanugo; difference is vellus is present through
adulthood
Fine, short, often no pigment or medulla
Women believed to have 55% more vellus hair than men

38. Terminal
Longer, coarser hair that covers scalp, arms, legs, groin area,
axillae, and on faces, chests, and backs of men
Hair follicles can produce vellus or terminal hair.
Affected by:
Age
Genetics
Health
Hormonal changes of puberty, pregnancy, and
menopause

39. Stages of Hair Growth
1.) Growing - Anagen
2.) Transitional - Catagen
3.) Resting – Telogen
**ACT

40. Anagen: The Growing Phase
Hair follicle at its deepest
Hair matrix active, surrounding the dermal papilla
Can be affected by health of the individual
Once hair reaches full length it can remain there, depending
on location, for varying amounts of time.

41. Catagen: The Transitional Phase
Follicle separates from dermal papilla and shrinks to 1/3 of
size
Thin cord of epidermal tissue attaching follicle to dermal
papilla retracts upward with the dermal papilla
Shortest hair growth stage

42. Telogen: The Resting Stage
Follicle is 1/3 of original size
Base looks like club
Bulb is usually white
Dermal papilla is separated from hair follicle and attached by
thin cord of epidermal cells; will be released by end of phase

43. Hair Growth
Incomplete science
Things we know:
Hair grows faster in the summer
Good health improve hair growth
Young people experience more hair growth
Increase in number of telogen hairs during illness, after
childbirth, and when experiencing stress.

44. Functions of the Skin
Largest sensory organ
Multiple functions:
Protection
Heat regulation
Excretion – discharging waste material
Secretion – producing and discharging substances from glands
Absorption – uptake of one substance into another
Sensation
Synthesis of Vitamin D
Hair plays important role in these functions.

45. Protection
Skin protects the body against the environment and invasion
of bacteria.
Skin is usually NOT sterile and is covered by bacteria
 Noninvading and nonpathogenic bacteria
Built-in protective aid, ACID MANTLE

46. Acid Mantle
pH of 5 to 5.6
Created by the combined activity of sweat and sebaceous
glands
Perspiration is acidic and acts as bactericide (inhibits growth of
bacteria)
NOT TRUE of areas of higher perspiration (groin and axillae),
skin is softer and less acidity in excessive perspiration

47. Protection continued
When organism does invade skin, reactions (inflammation,
swelling, welts) occur.
Leucocytes are released and destroy the invading organism.
Reactions help to prevent spread of infection to surrounding
tissue.

48. Protection continued
Horny layer acts as barrier
Skin is waterproof (thanks in part to sebum)
Sebum prevents drying and cracking → prevents bacteria and
germs from entering
When intact, skin prevents harmful fluids from entering and
prevents water, blood, and lymph from leaving.

49. Protection continued
Stratum germinativum protects by containing melanocytes which
produce melanin
Melanin – the body’s own sunscreen which protects from harmful UV
radiation
Dark skin get better protection, few incidences of skin cancer

50. Protection continued
Adipose tissue – cushions the body from falls, protects
against minor trauma, and provides source of energy

51. Protection by Lymphatic System
Lymphatic fluid and lymphocytes are produced in lymph
nodes.
Lymphocytes transported through lymph vessels
Engulf bacteria
Carried back to lymph nodes
Filtered and drained of waste products

52. Heat Regulation
Healthy body temperature of 98°F or 37°C
Skin helps body to adjust and maintain a safe temperature
Evaporation
Perspiration
Radiation
Insulation

53. Heat Regulation – Evaporation and
Perspiration
Evaporation of perspiration produces cooling (AKA
thermoregulation).

54. Heat Regulation - Radiation
Radiation from constriction or dilation of capillaries affect
body temperature.
Dilation (expansion) causes surface heat of body to be reduced
through radiation. Causes flushed appearance.
Constriction (contraction) slows blood flow, preserving heat.
Gives skin bluish tint.

55. Heat Regulation - Insulation
Arrector pili muscle contracts, lifts hair, trapping a layer of
insulating air on skin’s surface. (Air is the best insulator!)
Sebum lubricates hair, preventing it from breaking; allows
hair to do its job.
Adipose tissue acts as effective insulator, keeping body
warm.

56. Secretion and Excretion
Sebaceous glands – secrete sebum, skin’s natural lubricant
Sudoriferous glands – excrete salt, urea, and other waste
material during perspiration.

57. Sensation
Experience heat, cold, pain, pressure
Damage to nerves can leave the skin numb, once tissue has
healed.

58. Absorption and Penetration
Skin can absorb oil- and fat-based substances
Pharmaceutical creams and lotions penetrate the dermis and
absorb into the blood supply
Require medical guidance and physicians’ prescriptions to be
obtained

59. Absorption and Penetration
Cosmoceuticals contain NO drugs or medications but could
cause drug reactions.
May have deeper absorption qualities than over-the-counter
cosmetics.
Obtained from and require professional guidance of
dermatologist, plastic surgeon, or skin-care professional.

60. 1.) What are the three main layers of the
skin?
Epidermis, dermis, and subcutis or subcutaneous layer.

61. 2.) Into which two zones is the epidermis
divided?
Horny zone and germinal zone.

62. 3.) Name two layers of the epidermis.
Stratum corneum,
stratum lucidum,
stratum granulosum,
stratum spinosum,
stratum germinativum.

63. 4.) In which layer are melanocytes found?
Stratum germinativum

64. 5.) What are the two layers of the dermis?
Papillary layer and reticular layer

65. 6.) What is a sudorific gland?
A sweat gland, or gland that excretes salt, urea, and other waste
material.

66. 8.) Where is the hair matrix?
In the hair follicle bulb

67. 9.) What are the three stages of hair
growth?
Anagen, catagen, and telogen

68. 10.) Name at least five functions of the
skin.
Protection, heat regulation, excretion, secretion, absorption,
sensation, synthesis of Vitamin D.