Integumentary system

The Integumentary System Includes the skin and accessory organs such as hair, nails and glands. 15 -16 % of body weight. Helps maintain homeostasis. Two main regions: Epidermis Dermis.

Functions of the Integumentary System Protects the body from physical trauma, invasion by pathogens and prevents water loss. Helps regulate body temperature. Contains sensory receptors, ie. touch, pain, pressure. Synthesizes chemicals such as melanin and vitamin D.

Characteristics of the Epidermis Thin, outermost layer of the skin. Made of stratified squamous epithelium. New epidermal cells derived from stem (basal) cells. Outer skin cells are dead and filled with keratin; form a waterproof barrier. Some cells convert cholesterol derivative to vitamin D.

Epidermal Pigments Produce skin color: CAROTENE: Yellow tones; some Asian skin. MELANIN: Darker skin tones. Freckles: Patches of melanin. HEMOGLOBIN: Reddish tones; fair-skinned.

Skin Cancer 2 of the 3 types that arise in the epidermis: BASAL CELL CARCINOMA: Most common yet least deadly. MELANOMA: Most deadly form of skin cancer; least common.

Characteristics of the Dermis The thick, inner layer of the skin. Made of dense fibrous connective tissue. Contains elastic and collagen fibers. Contains blood vessels, many sensory receptors and glands. SUBCUTANEOUS LAYER: Beneath the dermis made of loose connective and adipose tissue. Common site for injections.

Accessory Organs of the Skin NAILS: Derived from the epidermis; protective covering of finger tips. HAIR FOLLICLES: Derived from the dermis but grows from epidermal cells; protection and sensory functions. OIL GLANDS: Associated with hair; produce sebum that lubricates hair and skin as well as retards bacterial growth. SWEAT GLANDS: Derived from the dermis; help to regulate body temperature.

homeostasis

What is homeostasis? The ability to maintain a relatively constant internal environment in the body. The nervous and endocrine systems are key in maintaining homeostasis . Changes from the normal tolerance limits results in illness or even death.

All systems are important in maintaining homeostasis

Mechanisms for Maintaining Homeostasis NEGATIVE FEEDBACK: Keeps a variable close to a particular value/set point. Ex. Blood glucose levels are kept within a narrow range. POSITIVE FEEDBACK: Brings about an increasing change from a set point. Ex. Increasing fever from 98.6˚F

Negative Feedback The primary mechanism for maintaining homeostasis. Has two components: Sensor: Detects internal chance in environment. Control center: Brings about an effect to return conditions to normal. The output of the system resolves or corrects the original stimulus

An Example of Negative Feedback: Body Temperature

Positive feedback Mechanism for increasing the change of the internal environment in one direction. Ex. The secretion of oxytocin during birth to continually increase uterine contractions. Can be harmful such as when a fever is too high and continues to rise.