Integumentary System

Ms.Anum Khalid

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Objectives

At the end of this presentation the students will be able to:

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• Elaborate anatomy and physiology of integumentery system.
• Explain related structures like hairs, nails and sweat glands and their types.
• Describe functions of integumentery system.

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Introduction

• Integument means outside layer/coat
• An outside layer that is separating and protecting the internal human structure from the outside environment
• The human integumentary system is the biggest organ of the body.
• It comprises almost 16% of the human body weight.

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Skin layers

• Skin has three main layers
• The epidermis, the outermost layer of skin, provides a waterproof barrier.
• The dermis, beneath the epidermis, contains tough connective tissue, hair follicles, and sweat glands. Thicker layer of skin.
• The deeper subcutaneous tissue (hypodermis) is made of fat and connective tissue

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Epidermis (outermost layer)

• It is the most superficial layer of the skin and is composed of epithelium. It has no direct blood supply, the epidermis relies on nutrients in the interstitial fluid that have diffused from the capillaries located in the dermis.

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Epidermis (outermost layer)�

FIVE SUB-LAYERS

• Stratum Corneum
• Stratum lucidum
• Stratum Granulosum
• Stratum Spinosum
• Stratum Basale

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FOUR TYPE OF CELLS

• Keratinoytes
• Melanocytes
• Merkel cells
• Langerhans’ cells

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This is the outside layer composed of mainly five sub�layers and four type of cells

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Layers of epidermis

• Stratum Corneum:

The most superficial layer of the epidermis and exposed to the outside environment. There are many cells which are tightly packed together. This allows the skin to be tough and waterproof. This layer is important in the prevention of invasion from foreign things, such as bacteria etc.

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It is present between granulosum and the stratum corneum. It is a tough layer and is found in thickened skin, including the palms of the hand and soles of the feet.

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• Stratum Granulosum:

The stratum granulosum is composed of 3 to 4 layers of cells. Keratinocytes migrating from the underlying stratum spinosum become known as granular cells in this layer.

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Stratum lucidum:

Spiny layer, consist on 8-10 rows of polyhedral (many sided) cells. As the cells multiply in the stratum germinativum, they are pushed upward into the stratum spinosum. This layer of cells, in addition to keratinocytes, contains Langerhans cells, which are involved in defense mechanisms.

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• Stratum basale

Also called the stratum germinativum. This layer is the deepest layer of the epidermis, in which many cells are active and dividing.

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Stratum spinosum:

Stratum basale conti…..

• The stratum basale is separated from the next layer – the dermis . Epidermal ridges which are folds that extend into the dermis increase friction and surface area, providing a better, more secure grip of objects. The shapes of the ridges are genetically determined and unique to an individual; they do not change with time. For this reason, fingerprints can be used for identification.

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Cells of epidermis

• Keratinocytes: Keratinocytes make up 90% of the epidermis. Produce Keratin which helps protect the skin from heat, microorganisms, and chemicals in the environment. It is also work as a water proofing protein and also the major protector substance also it gives hair, nails, and skin their hardness.

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Conti……

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• Melanocytes: Produce melanin(in stratum basale) which is a pigment giving us the colour of our skin and hair. The melanin pigment protects the skin from the harmful effects of ultraviolet (UV) radiation. Exposure to UV rays stimulates that produce melanin.

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• Merkel cells: It present in stratum basale. It associated with sensory nerve endings. They are associated with slowly adapting (SA1) somatosensory nerve fibers.

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• Langerhans’ cells: Star like shaped cells

functions like macrophage by engulfing bacteria, foreign particles, and damaged cells that occur in this layer.

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Dermis

• It is the second layer made up of dense irregular connective tissue mostly made up of collagen and elastin in interwoven pattern.
• It contains blood and lymph vessels, nerves, and other structures, such as hair follicles and sweat glands.  Having two layers papillary and reticular.

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PAPILLARY LAYER

The papillary layer of the dermis is loose connective tissue. This superficial layer of the dermis projects into the stratum basale of the epidermis to form finger-like dermal papillae.  This layer also contains lymphatic capillaries, nerve fibers, and touch receptors called the Meissner corpuscles.�

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Integumentary system

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RETICULAR LAYER

• It is dense irregular connective tissue which gives the dermis its strength.
• Remember, the epidermis is the strongest layer of the SKIN, but the reticular layer of the dermis is the strongest layer of the DERMIS.
• This layer has lots of collagen and elastin (elastic fibers)
• Stretch marks are caused from tiny tears in the collagen of the dermis.

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Hypodermis

• Hypodermis is also called the subcutaneous layer or superficial fascia
• “Hypodermis” (Greek) = below the skin
• “Subcutaneous” (Latin) = below the skin
• Composed of fibroblasts, adipose tissue[fat tissue] and macrophages. Fatty tissue which stores fats (areolar tissue and adipose cells).

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Structures included

Skin and its appendages which are

• Nail
• Hair
• Sebaceous glands
• Sweat glands

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Nails

• Nails are hard keratinized plates on the dorsal surfaces of the tips of toes and fingers
• Fingernails and toenails are made of a tough protective protein called keratin.
• Consist on body, Lunula &

cuticle.

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Cont…

Function

• A healthy finger nail has the function of protecting the distal phalanx, the fingertip, and the surrounding soft tissues from injuries.

Growth

• The growing part of the nail is under the skin at the nail's proximal end under the epidermis, which is the only living part of a nail. This is why cutting a nail too short can be quite painful.

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• In mammals, the growth rate of nails is related to the length of the terminal phalanges (outermost finger bones). Thus, in humans, the nail of the index finger grows faster than that of the little finger; and fingernails grow up to four times faster than toenails. In humans, nails grow at an average rate of 3 mm (0.12 inch) in a month. 

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Anatomy of Nail

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Hairs

• Hairs grow out of follicles
• Follicles are invaginations of epidermis into dermis
• A smooth muscle called pilomotor or arrector pili is attached to each hair follicle due to which hair follicle upright during fear or when stimulated by cold or emotion.
• The muscle are simulated by sympathetic nerve fiber in response to fear and cold.(involuntary contraction of skeleton muscle.

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Hair composed of dead columns of keratinized cells. Consists on;;;

- shaft: is the superficial portion of hair

- root: below the surface in the dermis

Shaft and root are composed of three layers: inner medulla, middle cortex and outer cuticle.

Inner medulla has 2-3 rows of polyhedral cells where pigment is located

Cortex is major portion of shaft

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Glands in skin

• There are two types of gland present in integument. Sebaceous and sweat glands
• Sebaceous glands are attached to the hair follicle in the dermis which make sebum.
• Sebum is an oily material which is required for maintaining the flexibility of hair as they grow.
• There are no sebaceous glands in the palms and soles

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• The function of sebum is to prevent drying of skin & hair. Too much sebum may trap the bacteria within hair follicles and creates small infection
• Blockage of sebaceous glands may lead to skin problems like acnes due to infection of blocked glands with bacteria.

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Sweat glands

• Sweat gland are coiled tubular glands that are surrounded by a network of capillaries. Located in the dermis, they discharge secretions directly onto the surface of the skin or the hair follicles.
• There are two types of sweat glands,

eccrine/ merocrine and apocrine.

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are located over the entire body. There are approximately 2–5 million of these glands, with the forehead, palms, and soles having the highest number. The main function of sweat is to cool the surface of the skin and, thereby, reduce the body temperature

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Eccrine sweat glands

are located in the armpits, around the nipples, in a bearded region (in men), and in the groin area. They start to secrete at puberty and produce a cloudy, sticky secretion, with a characteristic odor. The secretion is a potential nutrient for microorganisms and the action of bacteria on this secretion tends to intensify the odor.

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Apocrine sweat glands

• Other than these two glands, Mammary glands(milk production) and Ceruminous glands(which secrete cerumen or earwax present in auditory canal…..Ear protection) are also present in skin.

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Functions of skin

Skin has so many functions in which main function are:

• Protection
• Regulation of body temperature
• Formation of vitamin D
• Sensation
• Absorption and Excretion

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Protection

• First defense mechanism…..
• Physical protection ……
• Invasion, microbes, heat, chemical. trauma.…….etc

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Regulation of body temperature

• Control is achieved mainly by thermo receptors in the hypothalamus.
• Heat produce in the body and lost in environment………..balance for normal temperature.

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Formation of vitamin D

• Excessive exposure to sun is harmful but some is useful which play an important part in the synthesis of vitamin D (fat soluble) in which the important one is vitamin D3 (cholecalciferol) …..this vitamin work in intestine to absorb calcium and phosphate.

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Sensation

• Sensory receptors consist of nerve endings in the dermis that are sensitive to touch, pressure, temperature or pain. Stimulation generates nerve impulses in sensory nerves that are transmitted to the cerebral cortex. Some areas have more sensory receptors than others causing them to be especially sensitive, e.g. the lips and fingertips.

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Excretion

• The skin is a minor excretory organ for some substances including: Sodium chloride in sweat and excess sweating may lead to abnormally low blood sodium levels, Urea, especially when kidney function is impaired.

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• Other functions like use of medication (absorption through skin), presence of normal flora, environmental/sourrounding sensation like pain, etc, reflection of emotion (facial expression), beauty of any human being/appearnce.

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References

• Kalyani Premkumar, The Massage Connection. Anatomy & physiology, 2nd edition (Lippincott
• Ross & Wilson, Anatomy & physiology for nurses.
• www.google.com

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