the integumentary system

1. The Integumentary
System

2. Learning Outcomes
At the end of the lecture, the students should
be able to
1. Name the two distinct layers of the skin
2. Identify the major structures found in the
skin
3. Describe the structure and growth of hair and
nails
4. Describe the functions of the integumentary
system.

3. General Considerations
Definition:
– The integumentary system consists of the skin and
other structures such as glands, hairs and nails.
– Skin: the outer or external covering of the body
comprised of two parts—a superficial epidermis and a
deeper dermis
Surface area:
– Largest organ in the body with a surface area of 1.5–
2.0 m2 in an adult
– Surface area can be roughly estimated by the ‘rule of
nines’

4. RULE OF NINE

5. Structure of the Skin
The skin is made up of two distinct layers:
epidermis and dermis

6. Epidermis
The most superficial layer of the skin
Is avascular
Composed of keratinized stratified squamous
epithelium
Varies in thickness in different areas
Made up of 4distinct cell types and 5 layers of tissues

7. EPIDERMIS

8. Cells in the epidermis:
- keratinoytes
- melanocytes
- Merkel cells
- Langerhans’ cells

9. most abundant
- produce keratin (fibrous protein)
- protective; waterproofing the skin
- continuous mitosis
- form in the deepest layer called the
stratum basale
- cells push their way up to the surface
where they are dead cells filled with
keratin; will slough off. Regenerates every
25-45 days.(average 40 days)
Outer layer of dead skin cells called cuticle
1- Keratinocytes

10. 2- Melanocytes:
- cells produce brownish/black pigment
called melanin. (8% of epidermal cells)
- stratum basale
- branching processes (dendrites)
- melanin are transported along dendrites of
the melanocytes to keratinocytes.
- melanin accumulates on the superficial
aspect of the keratinocyte shielding its
nucleus from harmful UV light.
- lack of melanin: albino

12. 3- Merkel cells:
- stratum basale
- attach to keratinocytes by desmosomes
- make contact with a sensory neuron ending
called a Merkel disc (touch).
4- Langerhans’ cells:
- star-shaped cells arising from bone marrow that
migrate to epidermis.
- epidermal dendritic cells (macrophages)
- interact with a WBC called a T- helper cell
- easily damaged by UV light.

14. Epidermis

15. Epidermis
 Layers of the epidermis (deepest to most superficial):
– Stratum basale (basal or germinal layer)
– Stratum spinosum (spinous layer)
– Stratum granulosum
(granular cell layer)
– Stratum lucidum
(translucent layer;
usually absent in
thin skin)
– Stratum corneum
(horny layer)

16. 1- Stratum corneum (horny layer)
- layer has many rows of dead cells filled with
keratin
- continuously shed and replaced (desquamation)
- effective barrier against light, heat and bacteria
- 20-30 cell layers thick
- dandruff and flakes
- 18kg of skin flakes
in a lifetime

17. 2- Stratum lucidum
- seen in thick skin of the palms and soles of feet.
- 3-5 rows of clear flat dead cells

18. 3- Stratum granulosum
- 3-5 rows of flattened cells
- nuclei of cells flatten out
- organelles disintegrate ,cells eventually die
- keratohyalin granules (darkly stained)
accumulate
- lamellated granules secrete glycolipids into
extracellular spaces to slow water loss in the
epidermis

19. 4- Stratum spinosum: “spiny layer”
- 8-10 rows of polyhedral (many sided) cells
- appearance of prickly spines
- melanin granules and Langerhans’ cell
are the majority

20. 5- Stratum basale: deepest epidermal layer
- attached to dermis
- single row of cells
- mostly columnar keratinocytes
- with rapid mitotic division
- stratum germinativum
- contain merkel cells and
melanocytes 10-25%

21. Stratum corneum
Stratum lucidum
Stratum
spinosum
Stratum
granulosum
Stratum
basale

22. Skin color
Colour of skin is determined by special cells
called melanocytes
 melanocytes produced pigment melanin present
within epidermis
Level of oxygenation of hemoglobin and amount
of blood circulating in the dermis – give the skin
pink color
Bile pigment in blood and carotenes in
subcutaneous fat give skin yellowish color .
Race is determined by amount of melanin

23. Dermis
Deep vascular layer of the skin
Made up of connective tissue containing
collagenous and elastic fibres
Blood vessels, lymphatics, nerves, hairs, nails
and glands are found in this layer
Fibroblasts, macrophages and mast cells are
the main cells

25. Layers of Dermis
 Papillary layer—has fingerlike projections called
dermal papillae that form the basis for
fingerprints and footprints
- contain pain receptors and touch receptors
(Meissner’s corpuscles)
Reticular layer—composed of dense connective
tissue, bundles of collagen and networks of
elastic fibres. Occupied by adipose tissue, hair
follicles, nerves, sebaceous glands and ducts of
the sweat glands

26. Human Anatomy, 3rd edition
Prentice Hall, © 2001
Fingerprints

27. The structure in Dermis
• blood vessels
• Lymph vessels
• Sebaceous glands
• Sweat glands and
their ducts
• Hair roots,follicles
and shaft
• Sensory Nerves
ending
• The arrectors
pilorum (pili)

28. Hairs
composed of dead columns of keratinized
cells.
distributed all over the body, except the
palms, soles, dorsal surface of distal
phalanges, umbilicus, glans penis, inner
surface of prepuce, labia minora and inner
surface of labia majora
Length, thickness and colour vary in
different parts of the body

29. Hair Structure
–Shaft
• Superficial portion
–Root
• Below the surface
–Cuticle
• Outermost layer of hair
–Hair develops in follicles
• Downward continuation of epidermis

30. Hair Structure

31. Hairs
Diagrammatic section of the skin showing hair, sebaceous glands,
arrector pili muscle and sweat gland

32. Hair follicle surrounds the root.
Bulb is the enlargement at the end of the follicle.
- Also houses the germinal layer
Papilla (nipple like) is located in the bulb and is where
the blood supply nourishes the hair.

33. Hair
Dark hair: mostly melanin
Blond and red hair: melanin with iron .
Gray hair: loss of pigment
White hair: air bubbles in the medullary hair shaft.
Vellus hair: fine hair
Terminal hair : coarser hair; axillary and pubic
region.
Grow in response to sex hormones
Hirsutism: excessive hairiness: increase androgens

34. Functions of Hair
–Protection
–Thermoregulation
–Sensory to fear and cold
–Minor role in humans

35. Arrector pili (pl. pilorum) is smooth muscle located in
the dermis and is attached to the side of the hair
shaft.
the muscle are stimulated by sympathetic nerve fibre
in respond to fear and cold- fright, cold and emotions
will contract muscle and pull hair in vertical position.
Causing “Goose bumps”.

37. Glands:
Two types of glands exist in the integument.
- Sebaceous glands (oil glands)
- Sudoriferous glands (sweat glands)
Sebaceous glands: (holocrine glands)
- connected to hair follicle
- not found on palms and soles of feet
- secretes sebum (fats, cholesterol and
proteins
- keep hair from drying out, keeps skin moist
- whiteheads, blackheads and acne

38. Sebaceous Glands

40. Sebaceous Glands
Distributed all over the dermis of the skin except
palms and soles
Abundant in scalp, face, and apertures of nose,
ears, mouth and anus
Secretes - sebum that is oily in nature:
– Keeps the hair soft and pliable
– Provides some waterproofing for skin
– Acts as a bactericidal/fungicidal agent
– Prevents drying and cracking of the skin

42. Sweat Glands
Two types: eccrine and apocrine
1. Eccrine sweat glands:
– Found in almost every part of the skin except for the
margins of lips, nail beds of fingers and toes
– Single tube having a highly coiled secretory part and
a straight duct
– Produce thin watery secretion
– Help in regulation of the body temperature and
excreting body salt

43. The Skin with Sweat Glands

44. Sweat Glands
Apocrine glands:
– Distributed primarily to the skin of the axilla,
eyelids,pubic region and areola of the breasts
– Cerruminous glands that produce earwax are
modified apocrine glands
– Simple branched tubular glands
– Produce a more viscous secretion with a
characteristic odour

46. Nails
 Hardened keratin plates
which make solid
coverings over the
dorsal surfaces of the
terminal portions of
fingers and toes
Structure of a nail:
A. Finger nail viewed from above
B. Cross-section of the finger nail and nail bed

47. Nails:
- Produced by cells in the epidermis
- Nail plate (body): visible portion
- Nail root: located under cuticle
- Lunula: half moon crescent shaped
white portion under cuticle
- Nail bed: located under nail plate
- Hypoxia: decreace. oxygen in blood,
nail bed will turn blue- cyanosis

49. Nail Structure

50. Nerve endings:
- Exteroceptors (stimulus outside of body)
- Pacinian (lamellated) corpuscles: deep
pressure and stretch
- Meissner’s (tactile) corpuscles: light
touch, vibration and discriminative
touch.
- hair root plexus
- free (naked) nerve endings: nociceptors
(pain) and thermoreceptors ( hot –
deep and cold- surface)
- Ruffini’s corpuscles: deep pressure

51. • Hypodermis
- called subcutaneous, Sub-Q or superficial
fascia
- anchors skin to underlying structures
- contains adipose tissue and blood vessels
- common site for injection

52. Functions of the Skin
–Protection
–Temperature regulation
–Sensations
–Excretion of wastes
–Blood reservoir
–Synthesis of compounds

53. 1- Protection
- Physical barrier - protects underlying tissues from
injury, UV light and bacterial invasion.
- Mechanical protection- is part non specific
immunity (skin, tears and saliva).
2- Regulation of body temperature
- high temperature or strenuous exercise; sweat is
evaporated from the skin surface to cool it down.
- vasodilation (increases blood flow) and
vasoconstriction (decrease in blood flow) regulates
body temp.

54. Regulation of body temperature

55. Regulation of body temperature
36-37.2⁰C

56. 3-Sensation
- nerve endings and receptor cells that detect
stimuli to temp., pain, pressure and touch.

57. 4- Excretion
- sweat removes water and small amounts of salt,
uric acid and ammonia from the body surface
5- Blood reservoir
- dermis has an extensive network of blood vessels
carrying 8-10% of total blood flow in a resting adult.
6- Synthesis of Vitamin D (cholecalciferol)
-UV rays in sunlight stimulate the production of Vit.
D. Enzymes in the kidney and liver modify and
convert to final form; calcitriol (most active form of
Vit. D.)
Calcitriol aids in absorption of calcium from foods
and is considered a hormone.

58. Regulation of body temperature

59. conclusion
–Combination of 4 main tissues:
• Epithelial – outer layer
• Connective – underlies dermis
• Smooth Muscle – goose bumps
• Nervous – sensory receptors

60. Epidermis and Dermis
–Epidermis is avascular (no blood
vessels)
–Dermis is highly vascular (has blood
vessels)
–Epidermis receives nourishment from
dermis
–Cells far away from nourishment die