The integumentary system consists of the skin, hair, nails, and glands. The skin is the largest organ and has two main layers - the epidermis and dermis. The epidermis is made of keratinized epithelial tissue and contains keratinocytes, melanocytes, Langerhans cells, and Merkel cells. The dermis is made of connective tissue. Hair, nails, sebaceous glands, and sweat glands are accessory structures that develop from the epidermis and serve protective and temperature regulating functions. The integumentary system maintains body temperature, protects the internal organs, and detects sensations.

1. INTEGUMENTARY SYSTEM
Presented by:-
HIMIKA RATHI

2. INTRODUCTION
• The integumentary system is composed of the skin, hair, oil
and sweat glands, nails, and sensory receptors.
• The integumentary system helps maintain a constant body
temperature, protects the body, and provides sensory
information about the surrounding environment.

4. STRUCTURE OF SKIN
• The skin (also known as the cutaneous membrane or integument)
covers the external surface of the body and is the largest organ of the
body in both surface area and weight.
• Structurally, the skin consists of two main parts.
• The superficial, thinner portion which is composed of epithelial tissue,
is the epidermis.
• The deeper, thicker connective tissue portion is the dermis.

5. EPIDERMIS
• The epidermis is composed of keratinized stratified squamous
epithelium.
• It contains four principal types of cells: keratinocytes, melanocytes,
Langerhans cells, and Merkel cells
• About 90% of epidermal cells are keratinocytes, 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.

6. EPIDERMIS
• About 8% of the epidermal cells are melanocytes, which produces the
pigment melanin.
• Their long, slender projections extend between the keratinocytes and
transfer melanin granules to them.
• Melanin is a yellow-red or brown-black pigment that contributes to
skin color and absorbs damaging ultraviolet (UV) light.

8. EPIDERMIS
• 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.

9. EPIDERMIS
• 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.

11. EPIDERMIS
• In most regions of the body the epidermis has four strata or layers—
• Stratum basale
• Stratum spinosum
• Stratum granulosum and
• a thin stratum corneum

13. Stratum basale
• The deepest layer of the epidermis is the stratum basale, composed of
a single row of cuboidal or columnar keratinocytes.
Stratum spinosum
• Superficial to the stratum basale is the stratum spinosum, arranged in 8
to 10 layers of many-sided keratinocytes fitting closely together.
Stratum Granulosum
• At about the middle of the epidermis, the stratum granulosum consists
of three to five layers of flattened keratinocytes.

14. Stratum Lucidum
• The stratum lucidum is present only in the thick skin of areas such as
the fingertips, palms, and soles.
Stratum Corneum
• The stratum corneum consists on average of 25 to 30 layers of
flattened dead keratinocytes.

15. Dermis
• The second, deeper part of the skin, the dermis, is composed of a
strong connective tissue containing collagen and elastic fibers.
• The dermis also has the ability to stretch and recoil easily.
• Leather, which we use for belts, shoes, baseball gloves, and
basketballs, is the dried and treated dermis of other animals.
• Based on its tissue structure, the dermis can be divided into a
superficial papillary region and a deeper reticular region.

16. • The papillary region makes up about one-fifth of the thickness of the
total layer. It consists of areolar connective tissue containing thin
collagen and fine elastic fibers.
• 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 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).

17. Accessory structures of the skin
• Accessory structures of the skin—hair, skin glands, and nails—
develop from the embryonic epidermis.
• They have a host of important functions.
• For example, hair and nails protect the body, and sweat glands help
regulate body temperature.

18. 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.
• Although the protection it offers is limited, 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.

19. Anatomy of a Hair
• The shaft is the superficial portion of the hair, which projects above
the surface of the skin.
• The root is the portion of the hair deep to the shaft that penetrates into
the dermis, and sometimes into the subcutaneous layer.
• The shaft and root of the hair both consist of three concentric layers of
cells: medulla, cortex, and cuticle of the hair.
• Cuticle of the hair, the outermost layer, consists of a single layer of
thin, flat cells that are the most heavily keratinized

20. Anatomy of a Hair
• Surrounding the root of the hair is the hair follicle, which is made up
of an external root sheath and an internal root sheath, together referred
to as an epithelial root sheath.
• The dense dermis surrounding the hair follicle is called the dermal root
sheath.
• The base of each hair follicle and its surrounding dermal root sheath is
an onion-shaped structure, the bulb.

21. 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.
• The nail body (plate) is the visible portion of the nail.
• The free edge is the part of the nail body that may extend past the
distal end of the digit. The free edge is white because there are no
underlying capillaries.

22. Nails
• The nail root is the portion of the nail that is buried in a fold of skin.
• The whitish, crescent-shaped area of the proximal end of the nail body
is called the lunula.
• The proximal portion of the epithelium deep to the nail root is the nail
matrix, where cells divide by mitosis to produce growth.

24. Skin Glands
• Two types of Skin Glands are present:
1) Sebaceous (Oil) Glands
2) Sudoriferous (Sweat) Glands

25. Sebaceous (Oil) Glands
• Sebaceous glands or oil glands are simple, branched acinar glands.
• They are connected to hair follicles.
• The secreting portion of a sebaceous gland lies in the dermis and
usually opens into the neck of a hair follicle.
• 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. Sebum also prevents excessive evaporation of water
from the skin, keeps the skin soft.

26. Sudoriferous Glands
• There are three to four million sweat glands, or sudoriferous glands.
• 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.
• Eccrine sweat glands , also known as merocrine sweat glands, are
simple, coiled tubular glands that are much more common than
apocrine sweat glands

27. Sudoriferous Glands
• They are distributed throughout the skin of most regions of the body,
especially in the skin of the forehead, palms, and soles.
• Eccrine sweat glands are not present, however, in the margins of the
lips, nail beds of the fingers and toes,and eardrums.
• The secretory portion of eccrine sweat glands is located mostly in the
deep dermis (sometimes in the upper subcutaneous layer)

28. Sudoriferous Glands
• The sweat produced by eccrine sweat glands (about 600 mL per day)
consists of water, ions (mostly Na and Cl), urea, uric acid, ammonia,
amino acids, glucose, and lactic acid.
• The main function of eccrine sweat glands is to help regulate body
temperature through evaporation.

29. Sudoriferous Glands
• Apocrine sweat glands are also simple, coiled tubular glands.
• Eccrine sweat glands start to function soon after birth, but apocrine
sweat glands do not begin to function until puberty.
• Apocrine sweat contains the same components as eccrine sweat plus
lipids and proteins.

30. Ceruminous Glands
• Modified sweat glands in the external ear, called ceruminous glands,
produce a waxy lubricating secretion.
• The combined secretion of the ceruminous and sebaceous glands is a
yellowish material called cerumen, or earwax.
• Cerumen also waterproofs the canal and prevents bacteria and fungi
from entering cells.

31. Function of Skin
• Thermoregulation
• Blood reservoir
• Protection
• Cutaneous sensations
• Excretion
• Synthesis of vitamin D

32. 32