Integumentary System Integumentary System consists of the Skin and its accessory organs

The skin may not typically be thought of as an organ, but it is made of tissues that work together as a single structure to perform unique and critical functions

Functions of the Integumentary System Protection Temperature regulation Sensations Storage of chemical compounds Excretion of wastes Synthesis of compounds (Vitamin D3)

The skin is made of multiple layers of cells and tissues, which are held to underlying structures by connective tissue Epidermis Dermis Hypodermis

Epidermis Lacks blood vessels (avascular)- gets all nutrients from blood supply in dermis Composed of: Stratified squamous epithelium Contains: the skin pigment Melanin

Dermis Thicker than the epidermis Composed of: Contains: Nervous Tissue Connective Tissue Muscle Tissue Epithelial Tissue Contains: Blood Vessels Touch receptors Accessory Organs

Dermis Contains Vasculature Provides blood supply/nutrients to all skin cells Plays role in thermo-regulation (vaso dialation/constriction)

The dermis contains many different touch receptors The dermis contains many different touch receptors. Different types of touch have different receptors.

Separates the epidermis and dermis Basement Membrane Separates the epidermis and dermis

Image shows cancer cell (green) crossing the basement membrane (red) Significance in health: The basement membrane must be broken down in order for cancer cells to invade surrounding tissue. Image shows cancer cell (green) crossing the basement membrane (red)

Hypodermis

Hypodermis Binds the skin to the underlying organs Composed of: loose connective tissue adipose tissues Contains: Major blood vessels

Burn classification based upon what layer(s) of tissue have been damaged

Epidermis Contains 5 layers! We are only concerned with 2 in this class ALIVE! Stratum Basale – Inner most layer Location of actively dividing epithelial cells and melanocytes DEAD! Stratum Corneum – Outer most layer Dead cells serve as protective barrier

Colored scanning electron micrograph (SEM) of human skin Stratum Corneum Stratum Basale Dermis

Keratin is a type of fibrous structural proteins. Keratinization Cells divide in Stratum Basale and push older cells up to surface. Cells starve and die as pushed away from dermis. Keratinization is the hardening process these cells undergo as they die. Keratin is a type of fibrous structural proteins.

The surface of your skin!

Keratinization Keratinization- the cementing of keratin fibers(cytoskeleton protein) in the dead cells. Constant shedding and replacement grows new EPIdermis every 25-45 days Calluses- Thickening of the Stratum Corneum due to rubbing and pressure

Calluses

Accessory Structures of the Skin

Melanin A dark pigment produced by melanocytes.

Vitiligo 

Melanocytes are located in the bottom layer of the epidermis

Why do you think a tan fades?

Melanin Absorbs UV radiation which protects the deeper tissues Tanning and dark skin color comes from melanocytes producing more melanin NOT due to more melanocytes

Hair Found on most skin surfaces Functions: Prevent heat loss Exceptions: Palms Soles of feet, Lips Nipples Parts of the genitalia Functions: Prevent heat loss Decrease sun exposure Touch receptors

Hair is a keratinous filament growing out of the epidermis Hair is a keratinous filament growing out of the epidermis. It is primarily made of dead, keratinized cells.

Hair follicles Follicles are the hair producing structures. Extend from the surface into the dermis Each hair develops from STRATUM BASALE cells in the base of the hair follicle Cells undergo keratinization and form into hair rather than a layer like skin

Arrector pili muscle- bundle of smooth muscle attached to each hair follicle -When the muscle contracts, hair within the follicle tends to stand on end -Emotional upset and cold can stimulate the arrector pili muscles to contract causing goose bumps

DON’T WORRY ABOUT ALL THIS! Just showing that hair is actually pretty complicated…

Nails Protective coverings Composed of keratinized stratified squamous epithelial cells. Arise from the epidermis. Look familiar?

Nails The nail forms at the nail root, which has a matrix of proliferating cells from the stratum basale that enables the nail to grow continuously

Nails As the nail develops, it slides forward over a layer of epithelium called the nail bed to which the nail remains attached

The nail bed is rich in blood vessels, making it appear pink, except at the base, where a thick layer of epithelium over the nail matrix forms a crescent-shaped region called the lunula (the “little moon”).

Sebacous Glands- produce an oil secretion called sebum A mixture of fatty material and cellular debris, secreted into the hair follicles Function: Helps keep the hair and skin soft, pliable and relatively waterproof.

Sudoriferous glands (sweat glands) Sweat is mostly water with small amounts of salt, urea and uric acid Location: Nearly all regions of the skin, most numerous in the palms and soles Located in deeper dermis or superficial subcutaneous layer. Structure: Gland consists of tiny tube (duct) that originates as a ball-shaped coil closed at its deepest end Coiled duct lined with sweat secreting epithelial cells Duct opens at the surface as a pore

Sudoriferous glands Two Types of Sudoriferous Glands: Apocrine Eccrine

Apocrine Eccrine Respond to: Emotional stress (emotionally upset, frightened or experiencing pain) Location: Numerous in the armpits and groin Development: Glands development stimulated by sex hormones Begin to function as an individual becomes sexually mature (puberty) Eccrine Elevated body temperatures Entire body Functional from birth

Sweat Glands- Eccrine and Apocrine Axillary, and pubic areas only. Develop during puberty Do not regulate body temp. Activated by stress and arousal. Empty onto hair follicle. Eccrine- More numerous, Ubiquitious, Used to regulate body temperature. Empty onto skin.

Diseases, Disorders, and Injuries of the Integumentary System

Acne What causes acne?

Acne Acne Body can produce an excess amount of sebum and dead skin cells These build up in the hair follicles and form a plug This creates an environment where bacteria (that we all have on our face) can thrive. The openings of the sweat glands aren't normally involved in acne

Acne is a skin disturbance that typically occurs on areas of the skin that are rich in sebaceous glands (face and back). Hormones, stimulate the release of sebum from sebaceous glands.

How is this child's skin different from yours?

Albinism Albinism is a complete or partial absence of pigment in the skin, hair and eyes Albinism results from inheriting a defective gene involved in the production of melanin.

How is this child's skin different from yours?

Defect in keritinization causes over shedding of cells Netherton Syndrome Defect in keritinization causes over shedding of cells

Skin Cancer Caused by UV radiation causing direct or indirect damage to DNA of the cells.

Xeroderma Pigmentosum Inherited genetic disorder in which the mechanisms which repair DNA after UV damage are deficient or absent. Leads to EXTREAME susceptibility to skin cancer.

WARNING! GRAPHIC CONTENT!