integumentary notes

1. Integumentary
System

2. Table of Contents
Structure of Skin
Skin Color
Appendages of the Skin

3. Structure of Skin
The integumentary systemis the largest body
organ and is composed of the skin, hair, nails,
and glands.
The skin has three layers
namely;
Epidermis
Dermis
Hypodermis

4. Epidermis
Epidermis is the outer layer of the skin, defined as a
stratified squamous epithelium, primarily comprising
keratinocytes in progressive stages of differentiation
Epidermis regenerates newcellsevery28days
The Epidermis is Avascular(has no blood
vessels)
Primary function is to act as a physical
and biological barrier to the external
environment.

5. Layers of the Epidermis
Layers of Epidermis ;
Stratum corneum – Superficial layer, the stratum corneum
is the outermost strata of the epidermis. It is mostly dead
cells, filled with a protein substance called keratin.
Stratum lucidum – Layer that is present only in the soles
and palms
Stratum granulosum – Alayers of flattened keratinocytes
producing keratin

6. Layers of the Epidermis
Layers of Epidermis ;
Stratum spinosum – Cells contain thick bundles of
intermediate filaments made of pre-keratin.
Stratum Basale - Stratum Basale lies deepest part of
the cell layer of the epidermis close to the dermis.
Stem cells in this layer are constantly dividing, and
millions of new cells are produced daily; hence the
alternate name Stratum germinativum.

7. Structure of the Epidermis

8. Cells of Epidermis
Two Major types of epidermal cells:
Melanocytes and Keratinocytes
Melanocytes are found and contained in the deep, basal layer
( stratum germinativum) of the epidermis
Contains melanin, a pigment that gives color to the skin and
hair and protects the body from UV sunlight. Freckles and moles are
the result of the high concentration of melanin in one spot.
 Sunlight and hormones stimulate the melanosome to increase
production

9. Cells of Epidermis
Two Major types of epidermal cells:
Melanocytes and Keratinocytes
Keratinocytes are synthesized from epidermal cells in the
basal layer
As they keratinize, they move to the surface, where they
flatten and die to form the outer layer of the skin (Stratum
Corneum)
 Keratinocytes produce a fibrous protein, keratin, which is
vital to the skin’s protective barrier function.

10. Structure of the Epidermis
As new cells are produced, some
become epidermal cells, and others
maintain the population of stem cells
by continuing to divide. The daughter
cells destined to become epidermal
cells are pushed upward, away from
the source of nutrition, to become
part of the epidermal layers closer to
the skin surface. As they move away
from the dermis and become part of
the more superficial layers, the
stratum spinosum and then the
stratum granulosum, they become
flatter and increasingly keratinized.
How it works?

11. Dermis
Dermis is the connective tissue below the epidermis.
Unlike the epidermis, the dermis is very vascular.
It contains the lymphatics, nerves, nerve
endings, blood vessels, sebaceous and
sweat glands, elastic fibers, and hair
follicles.
The primary role of the dermis is to sustain
and support the epidermis.

12. Dermis
Divided into two layers: Upper thin Papillary layer
and a deeper, thicker Reticular layer
The papillary layer is folded into ridges which extend into the
upper epidermal layer. These exposed surface ridges form
congenital patterns called fingerprints and footprints.
The reticular layer is the deepest skin layer. It contains
irregular connective tissue, as well as blood vessels, sweet
and oil glands, and deep pressure receptors called lamellar
corpuscles.

13. Dermis
The dermis is abundantly supplied with blood vessels that
play a role in maintaining body temperature homeostasis.

14. Subcutaneous Tissue
The subcutaneous tissue or hypodermis lies deep
the dermis, it is often discussed with the skin
because it attaches the skin to underlying tissues
such as muscle and bone.
The subcutaneoustissue containsloose
connectivetissue andfat cellsthat provide
insulation.
The subcutaneoustissue isnot apart of the
skin.

15. Skin Color
Three pigments contribute to skin color: melanin,
carotene, and hemoglobin.
Melanin- brown- black , red-yellow pigment
Carotene- Yellow-orange pigments
Hemoglobin- Red color of oxygenated blood

16. Melanin
Melanin- is made in the skin and is the primary
pigment that determines the skin color.
The sunlight exposure stimulates melanocytes
to produce more melanin pigment, resulting in
tanning of the skin.
People who produce a lot of melanin tend to
have brown-toned skin, whereas people with
less melanin are light skinned

17. Melanin
As the melanocytes produce melanin, it accumulates
in their cytoplasm in membrane-bound granules called
melanosomes. These granules then move to the ends
of the melanocytes’ spidery arms, where they are
taken up by nearby keratinocytes. Inside the
keratinocytes, the melanin forms a pigment umbrella
over the superficial, or “sunny,” side of their nuclei and
shields their genetic material (DNA) from the
damaging effects of UV radiation in sunlight

18. Carotene
Carotene is an orange-yellow pigment plentiful
in carrots and other orange, deep yellow, or
leafy green vegetables.
The people who eat large amounts of
carotene-rich foods, the skin tends to take on a
yellow-orange cast,

19. Hemoglobin
Hemoglobin is the pigment in red blood cells.
In light-skinned people, the crimson color of
oxygen-rich hemoglobin in the bloody supply
flusher through the transparent cell layers
above and gives the skin a rosy glow.

20. Hemoglobin
Cyanosis- when hemoglobin is poorly
oxygenated, both blood and the skin of light-
skinned people appear blue.

21. Emotion and skin color
Emotion may also influence skin color
Redness or Erythema – reddened skin may indicate
embarrassment, fever, hypertension, inflammation, or allergy.
Jaundice or yellow cast – an abnormal yellow tone usually
signifies liver disorder.
Bruises- the black-and-blue marks of bruising reveal sites where
blood has escaped from the circulation and has clotted in the
tissue spaces.The clotted blood masses are called hematoma.
Blanching or Pallor- Under certain types of emotional stress.

22. Appendages of Skin
-Cutaneous Glands
-Hair and hair follicles
-Nails
Appendages of the skin include:

23. Cutaneous Glands
Cutaneous Glands are all exocrine glands that
release their secretions to the skin surface via ducts.
Sebaceous glands secrete sebum, which is
emptied into the hair follicles.
Sebaceous glands are found all over the
body except palms of the hand and soles of the
feet.
Two major types of glands associated with the skin is
the Sebaceous Glands and Sweat Glands

24. Sebaceous Glands
Sebaceous glands also called oil glands
Sebaceous glands’product is called Sebum It is a
mixture of oily substance which act as a lubricant to
keep skin soft and moist and prevent hair from
becoming brittle. It also contains chemicals that kill
bacteria in the skin.
Sebaceous glands are more active when androgens
(male sex hormones) are produced.

25. Sebaceous Glands
---When sebaceous gland ducts are blocked by
sebum, acne appears on the skin surface. Acne is
an active infection of the sebaceous glands. If the
accumulated material oxidizes and dries, it
darkens, forming a blackhead. If the material
does not dry or darken, a whitehead forms. Acne
can be mild or extremely severe, leading to
permanent scarring.

26. Sweat Glands
Sweat Glands has two types namely Eccrine
and Apocrine.
Eccrine glands are far more numerous and are
found all over the body.
Eccrine glands produces- Sweat, , a clear
secretion that is primarily water plus some salts
,vitamin C, traces of metabolic wastes and lactic
acid.
Eccrine glands are important in body-heat
regulation.

27. Sweat Glands
Apocrine glands are largely confined to the
axillary (armpit) and genital areas of the body.
 There is a secretion in the apocrine glands that contains fatty
acids and proteins, as well as all the substances present in
eccrine sweat. May have milky or yellowish color. The secretion
is odorless, but when bacteria that live on skin use its protein
and fats as a source of nutrients, it can take on a musky,
sometimes unpleasant odor.

28. Hair
Hair is a flexible epithelial structure. The part of the
hair enclosed in the hair follicle is called the root,
and the part projecting from the surface of the scalp
or skin is called the shaft.
A hair forms by division of the
well-nourished stratum Basale
epithelial cells in the matrix
(growth zone) of the hair bulb at
the deep end of the follicle.

29. Hair Follicle
Hair follicles are actually compound structures. The
inner epithelial root sheath is composed of epithelial
tissue and forms the hair
Arrector pili- connect each side
of the hair follicle to the dermal
tissue. When these muscles
contract the hair is pulled
upright, dimpling the skin surface
with “goose bumps.”

30. Nails
Nails are simply scale-like modifications of the epidermis
which have been heavily keratinized. The stratum
Basale (site of growth) extends below the nail bed.
Their lack of melanin makes them colorless.
Each nail has a free edge, a body
and a root (embedded in the
skin).The borders of the nail are
overlapped by folds of skin called
nail folds.

31. Nails
The stratum basale of the epidermis extends beneath the nail
as the nail bed. Its thickened proximal area, called the nail
matrix, is responsible for nail growth. As the matrix produces
nail cells, they become heavily keratinized and die. Thus, nails,
like hairs, are mostly nonliving material..

32. Review Questions
1.) What are the three concentric regions of a hair shaft, from the outside in? cuticle, cortex, medulla
2.) What is serbum? Oily secretion of the sebacceous glands
3.) How do secretions of apocrine glands differ from those of the eccrine sweat glands?
-Both are dilute salt solutions containg vitamins and wastes.Apocrine secretion also contains proteins and fatty acids
4.) When a factory worker caught his finger in a machine, the engine nail,plus the nail matrix and bed, was torn off. Will his
nail grow back? Why or Why not?
-No, the nail won't re-grow because the growth region is torn off.
5.) Why do no skin cancers develop from stratum corneum cells?
-Because stratum corneum cells are dead
6.) What change in aging skin accounts for wrinkles and cold intolerance in older adults?
-Loss of subcutaneous fat