INTEGUMENTARY SYSTEM (1).pdf

Integumentary system is good 👍👍

1. INTEGUMENTARY
SYSTEM
By
Dr.S Divya
Assistant Professor
Dept. of Pharmacy Practice
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2. INTRODUCTION
The integumentary (in-inward; tegere-to cover) system is composed of the:
oskin,
ohair,
ooil and sweat glands,
onails, and
osensory receptors
The integumentary system contributes to homeostasis by protecting the body
and helping regulate body temperature
The integumentary system helps maintain a constant body temperature,
protects the body, and provides sensory information about the surrounding
environment.
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3. SKIN
Of all the body’s organs, none is more easily inspected or more exposed to
infection, disease, and injury than the skin.
Although its location makes it vulnerable to damage from trauma, sunlight,
microbes, and pollutants in the environment, the skin’s protective features
ward off such damage.
Because of its visibility, skin reflects our emotions (frowning, blushing) and
some aspects of normal physiology (such as sweating).
Changes in skin color may also indicate homeostatic imbalances in the body.
oFor example, the bluish skin color associated with hypoxia (oxygen
deficiency at the tissue level) is one sign of heart failure as well as other
disorders.
Dermatology(dermato-skin; logy-study of) is the medical specialty that
deals with the diagnosis and treatment of integumentary system disorders
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4. STRUCTURE OF SKIN
The skin (also known as the cutaneous membrane or integument) is the largest
organ in the body and covers the external surface of the body.
In adults, the skin covers an area of about 2 square meters (22 square feet) and
weighs 4.5–5 kg (10–11 lb), about 16% of total body weight.
It ranges in thickness from 0.5 mm (0.02 in.) on the eyelids to 4.0 mm (0.16 in.)
on the heels. However, over most of the body it is 1–2 mm (0.04–0.08 in.)
thick.
It includes glands, hair and nails.
There are two main layers of skin:
Epidermis (superficial, thinner portion,which is composed of epithelial
tissue)
Dermis (deeper, thicker connective tissue portion)
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5. Between the skin and
underlying structures is the
subcutaneous layer (also
called hypodermis)composed
of areolar tissue and adipose
(fat) tissue.
The subcutaneous layer serves
as a storage depot for fat and
contains large blood vessels
that supply the skin.
This region also contains
nerve endings called pacinian
(lamellated) corpuscles that
are sensitive to pressure
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Sectional view of skin

6. EPIDERMIS
The epidermis is composed of keratinized stratified squamous epithelium.
It contains four principal types of cells:
▪Keratinocytes
▪Melanocytes
▪Langerhans cells
▪Merkel cells
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7. I. Keratinocytes:
About 90% of epidermal cells are keratinocytes (keratino-horn like; cytes-
cells), which are arranged in four or five layers and produce the protein
keratin.
Keratin is a tough, fibrous protein that helps protect the skin and underlying
tissues from heat, microbes, and chemicals.
Keratinocytes also produce lamellar granules, which release a water-repellent
sealant that decreases water entry and loss and inhibits the entry of foreign
materials.
II. Melanocytes
About 8% of the epidermal cells are melanocytes (melano-black), which
develop from the ectoderm of a developing embryo and produce the pigment
melanin.
Their long, slender projections extend between the keratinocytes and transfer
melanin granules to them.
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8. Melanin is a yellow-red or brown-black pigment that contributes to skin color
and absorbs damaging ultraviolet (UV) light.
Once inside keratinocytes, the melanin granules cluster to form a protective
veil over the nucleus, on the side toward the skin surface. In this way, they
shield the nuclear DNA from damage by UV light.
Although their melanin granules effectively protect keratinocytes, melanocytes
themselves are particularly susceptible to damage by UV light.
III. Langerhans cells
Langerhans cells arise from red bone marrow and migrate to the epidermis,
where they constitute a small fraction of the epidermal cells.
They participate in immune responses mounted against microbes that invade
the skin, and are easily damaged by UV light.
Their role in the immune response is to help other cells of the immune system
recognize an invading microbe and destroy it.
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9. IV. Merkel cells
Merkel cells are the least numerous of the epidermal cells.
They are located in the deepest layer of the epidermis, where they contact the
flattened process of a sensory neuron (nerve cell), a structure called a Merkel
(tactile) disc.
Merkel cells and their associated Merkel discs detect touch sensations
Layers of Epidermis
In most regions of the body the epidermis has fourstrata or layers:
ostratum basale
ostratum spinosum
ostratum granulosum,
ostratum corneum (thin skin)
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10. Where exposure to friction is greatest, such as in the fingertips, palms, and
soles, the epidermis has fivelayers:
ostratum basale
ostratum spinosum
ostratum granulosum
ostratum lucidum
ostratum corneum (thick skin)
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Layers and cell types in epidermis

12. Stratum basale:
Deepest layer, composed of a single row of cuboidal or columnar
keratinocytes that contain scattered tonofilaments(intermediate filaments).
Stem cells undergo cell division to produce new keratinocytes.
Melanocytes and Merkel cells associated with Merkel discs are scattered
among the keratinocytes
The stratum basaleis also known as the stratum germinativum to indicate its
role in forming new cells.
Stratum spinosum: (spinos-thorn like)
Eight to ten rows of many-sided keratinocytes with bundles of tonofilaments.
This arrangement provides both strength and flexibility to the skin.
It includes arm like processes of melanocytes and Langerhans cells.
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13. Stratum granulosum:
Stratum granulosum (granulos-little grains) contains three to five rows of
flattened keratinocytes, in which organelles are beginning to apoptosis
(programmed cell death)
A distinctive feature of cells in this layer is the presence of darkly staining
granules of a protein calledkeratohyalin, which converts tonofilaments into
keratin,
The keratinocytes also contain lamellar granules, which release a lipid-rich,
water-repellent secretion.
The lipid rich secretion acts as a water-repellent sealant, retarding loss and entry
of water and entry of foreign materials.
Stratum lucidum
The stratum lucidum (lucid-clear) is present only in the thick skin of areas such
as the fingertips, palms, and soles.
It consists of three to five layers of flattened clear, dead keratinocytes that
contain large amounts of keratin and thickened plasma membranes.
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14. Stratum Corneum :
The stratum corneum (corne-horn or horny) consists on average of 25 to 30 layers of flattened
dead keratinocytes.
These cells are continuously shed and replaced by cells from the deeper strata.
The interior of the cells contains mostly keratin.
Between the cells are lipids from lamellar granules that help make this layer an effective water-
repellent barrier.
Its multiple layers of dead cells also help to protect deeper layers from injury and microbial
invasion.
*Keratinization
Newly formed cells in the stratum basaleare slowly pushed to the surface.
As the cells move from one epidermal layer to the next, they accumulate more and more keratin,
a process called keratinization. Then they undergo apoptosis.
Eventually the keratinized cells slough off and are replaced by underlying cells that in turn
become keratinized.
The whole process takes about four weeks in an average epidermis of 0.1 mm (0.004 in.)
thickness
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15. DERMIS
The second, deeper part of the skin, the dermis, is composed of a strong
connective tissue containing collagen and elastic fibers.
This woven network of fibers has great tensile strength (resists pulling or
stretching forces). The dermis also has the ability to stretch and recoil easily.
The few cells present in the dermis include predominantly fibroblasts, with some
macrophages, and a few adipocytes near its boundary with the subcutaneous
layer.
Blood vessels, nerves, glands, and hair follicles (epithelial invaginations of the
epidermis) are embedded in the dermal layer.
The dermis is essential to the survival of the epidermis, and these adjacent layers
form many important structural and functional relations.
Based on its tissue structure, the dermis can be divided into a superficial
papillary region and a deeper reticular region
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16. ➢Papillary region
The superficial portion of the dermis and makes up about one-fifth of the
thickness of the dermis.
It consists of areolar connective tissue with thin collagen and fine elastic
fibers.
Its surface area is greatly increased by dermal papillae, small, fingerlike
structures that project into the undersurface of the epidermis.
Some dermal papillae also contain tactile receptors called Meissner
corpuscles or corpuscles of touch, nerve endings that are sensitive to
touch, and free nerve endings, dendrites that lack any apparent structural
specialization.
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17. ➢Reticular region
The reticular region, which is attached to the subcutaneous layer, consists
of dense irregular connective tissue containing fibroblasts, bundles of
collagen, and some coarse elastic fibers.
The collagen fibers in the reticular region interlace in a netlike manner.
A few adipose cells, hair follicles, nerves, sebaceous (oil) glands, and
sudoriferous (sweat) glands occupy the spaces between fibers.
The combination of collagen and elastic fibers in the reticular region
provides the skin with strength, extensibility (ability to stretch), and
elasticity (ability to return to original shape after stretching)
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18. ACCESSORY STRUCTURES OF SKIN
Accessory structures of the skin are: hair, skin glands, and nails, which develop
from the embryonic epidermis.
HAIR:
❑Hairs, or pili, are present on most skin surfaces except the palms, palmar
surfaces of the fingers, the soles, and plantar surfaces of the feet.
❑In adults, hair usually is most heavily distributed across the scalp, in the
eyebrows, in the axillae (armpits), and around the external genitalia.
❑Hair on the head guards the scalp from injury and the sun’s rays. It also
decreases heat loss from the scalp.
❑Eyebrows and eyelashes protect the eyes from foreign particles, as does hair in
the nostrils and in the external ear canal.
❑Touch receptors (hair root plexuses) associated with hair follicles are activated
whenever a hair is moved even slightly. Thus, hairs also function in sensing
light touch.
❑Hairs are growths of epidermis composed of dead, keratinized epidermal cells.
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20. SKIN GLANDS:
The glands are epithelial cells that secrete a substance.
Several kinds of exocrine glands are associated with the skin: sebaceous (oil)
glands, sudoriferous (sweat) glands, and ceruminous glands.
Mammary glands, which are specialized sudoriferous glands that secrete
milk.
Sebaceous glands (sebace-greasy) or oil glands are simple, branched acinar
glands.
Sebaceous glands secrete an oily substance called sebum, a mixture of
triglycerides, cholesterol, proteins, and inorganic salts. Sebum coats the
surface of hairs and helps keep them from drying and becoming brittle.
These glandsarepresentin some locations, such as the lips, glans penis, labia
minora, and tarsal glands of the eyelids, skin of the breasts, face, neck, and
superior chest
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21. Sudoriferous glands: There are three to four million sweat glands, or sudoriferous
glands ( sudor-sweat; ferous-bearing).
The cells of these glands release sweat, or perspiration, into hair follicles or
onto the skin surface through pores.
Sweat glands are divided into two main types, eccrine and apocrine, based on
their structure, location, and type of secretion.
Eccrinesweat glands (eccrine-secreting outwardly), also known asmerocrine
sweat glands, are simple, coiled tubular glands that are much more common
than apocrine sweat glands. These are especially present in the skin of the
forehead, palms, and soles
Apocrinesweat glands (apo-separated from) are also simple, coiled tubular
glands. They are found mainly in the skin of the axilla (armpit), groin, areolae
(pigmented areas around the nipples) of the breasts, and bearded regions of the
face in adult males
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22. Ceruminous Glands are modified sweat glands in the external ear, called
ceruminous glands (cer-wax), produce a waxy lubricating, yellow colored
secretion called cerumen
Cerumen, together with hairs in the external auditory canal, provides a
sticky barrier that impedes the entrance of foreign bodies and insects.
NAILS:
Nails are plates of tightly packed, hard, dead, keratinized epidermal cells
that form a clear, solid covering over the dorsal surfaces of the distal
portions of the digits.
Each nail consists of a nail body, a free edge, and a nail root.
Functionally, nails help us grasp and manipulate small objects in various
ways, provide protection against trauma to the ends of the digits, and allow
us to scratch various parts of the body.
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24. FUNCTIONS OF SKIN
The numerous functions of the integumentary system (mainly the skin) include
thermoregulation, storage of blood, protection, cutaneous sensations, excretion
and absorption, and synthesis of vitaminD.
Thermoregulation
Thermoregulation is the homeostatic regulation of body temperature.
The skin contributes to thermoregulation in two ways:
oby liberating sweat at its surface and
oby adjusting the flow of blood in the dermis.
In response to high environmental temperature or heat produced by exercise,
sweat production from eccrine sweat glands increases; the evaporation of
sweat from the skin surface helps lower body temperature.
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25. In addition, blood vessels in the dermis of the skin dilate (become wider);
consequently, more blood flows through the dermis, which increases the
amount of heat loss from the body.
In response to low environmental temperature, production of sweat from
eccrine sweat glands is decreased, which helps conserve heat.
Also, the blood vessels in the dermis of the skin constrict (become narrow),
which decreases blood flow through the skin and reduces heat loss from the
body.
Blood Reservoir
The dermis houses an extensive network of blood vessels that carry 8–10%
of the total blood flow in a resting adult. For this reason, the skin acts as a
blood reservoir.
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26. Protection
The skin provides protection to the body in various ways:
Keratin protects underlying tissues from microbes, abrasion, heat, and
chemicals and the tightly interlocked keratinocytes resist invasion by
microbes.
Lipids released by lamellar granules inhibit evaporation of water from the skin
surface, thus guarding against dehydration; they also retard entry of water
across the skin surface during showers and swims.
The oily sebum from the sebaceous glands keeps skin and hairs from drying
out and contains bactericidal chemicals that kill surface bacteria.
The acidic pH of perspiration retards the growth of some microbes.
The pigment melanin helps shield against the damaging effects of ultraviolet
light.
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27. Epidermal Langerhans cells alert the immune system to the presence of
potentially harmful microbial invaders by recognizing and processing them.
Macrophages in the dermis phagocytize bacteria and viruses.
Cutaneous Sensations
Cutaneous sensations are sensations that arise in the skin, including tactile
sensations—touch, pressure, vibration, and tickling; as well as thermal
sensations such as warmth and coolness.
Another cutaneous sensation, pain, usually is an indication of impending or
actual tissue damage.
There is a wide variety of nerve endings and receptors distributed throughout
the skin, including the tactile discs of the epidermis, the corpuscles of touch in
the dermis, and hair root plexuses around each hair follicle
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28. Excretion and Absorption
The skin normally has a small role in excretion, the elimination of substances
from the body, and absorption, the passage of materials from the external
environment into body cells
Despite the almost waterproof nature of the stratum corneum, about 400 mL
of water evaporates through it daily.
Besides removing water and heat from the body, sweat also is the vehicle for
excretion of small amounts of salts, carbon dioxide, and two organic
molecules that result from the breakdown of proteins—ammonia and urea.
The absorption of water-soluble substances through the skin is negligible, but
certain lipid-soluble materials do penetrate the skin.
These include fat-soluble vitamins (A, D, E, and K), certain drugs, and the
gases oxygen and carbon dioxide.
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29. Synthesis of Vitamin D
Synthesis of vitamin D requires activation of a precursor molecule in
the skin by ultraviolet (UV) rays in sunlight.
Enzymes in the liver and kidneys then modify the activated molecule,
finally producing calcitriol, the most active form of vitamin D.
Calcitriol is a hormone that aids in the absorption of calcium in foods
from the gastrointestinal tract into the blood.
Only a small amount of exposure to UV light (about 10 to 15 minutes
at least twice a week) is required for vitamin D synthesis.
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