THE INTEGUMENTARY SYSTEM

Composed of: Skin Nerves Hair Pigment Sweat glands Muscles Oil glands Nails Nerves Hair Muscles Blood vessels Fat

Skin Functions Protects deeper tissues from: Mechanical damage Chemical damage Bacterial damage Thermal damage Ultraviolet radiation Desiccation

Skin Functions Aids in heat regulation Aids in the removal of certain waste products: urea and uric acid (in sweat) Identifies contact with an object or pain Synthesizes vitamin D

Skin Structure EPIDERMIS Made up of 5 external layer of epithelial tissue. Often keratinized (meaning it contains a water-proof protein called keratin) Made up of epithelial cells, melanocytes, and keratinocytes The visible part.

Skin Structure DERMIS Is referred to as the “true skin” Made up of two types of connective tissue The superficial papillary layer made up of a loose arrangement of collagen and elastic fibers. The deep reticular layer made up of densely packed collagen fibers with some elastic fibers. Has large supply of: blood vessels, sensory receptors (called corpuscles), and oil/sweat glands

HYPODERMIS Deep to the dermis Composed mostly of adipose tissue The amount of fat varies depending on the body part. Lots of fat: soles of feet, palms, lower back Little fat: eyelids, anterior wrist, top of foot

Skin Structure

Melanin Pigment (melanin) produced by melanocytes Melanocytes found in the epidermis Amount of melanin produced depends upon genetics and exposure to sunlight

Skin Color is attributed to: Melanin Yellow, brown or black pigments Carotene Orange-yellow pigment from some vegetables Hemoglobin Red coloring from blood cells in dermis capillaries Oxygen content determines the extent of red coloring

Freckles and moles are areas of melanin concentrations. Melanin within cells migrates to the cell surface that is exposed to sunlight and “shades” the nucleus from UV light. Excessive sun exposure breaks down melanin and can lead to genetic mutation (cancer).

The Glands of the Integument Sebaceous glands Sudoriferous glands Ceruminous glands

Sebaceous Glands Produce oil Serves as a lubricant for skin Kills bacteria on skin surface Have ducts that empty into hair follicles Glands become active at puberty

Skin Appendages Sudoriferous glands Produce sweat Widely distributed in skin Function Helps dissipate excess heat Excretes waste products Acidic nature inhibits bacteria growth Odor is from associated bacteria

Two types of Sudoriferous glands 1. Eccrine glands sweat is released via a duct to a pore on the skin surface most common sweat gland makes the “clean” sweat Sweat Composition 99% water some metabolic wastes

sweat ducts empty into hair follicles 2. Apocrine glands sweat ducts empty into hair follicles found in axillary and genital areas makes the “smelly” sweat Sweat composition water, proteins, and fatty acids. Glands become active at puberty.

Nerves We have two different types of sense receptors in the dermis. The ones closest to the epidermis are called Meissner’s corpuscles. They identify temperature change, and when you come into contact with an object. They sometimes have free nerve endings that detect pain.

These nerves are for identifying texture, pressure, and vibrations. The sense receptors that are deeper in the dermis are called Pacinian corpuscles. These nerves are for identifying texture, pressure, and vibrations. Pacinian corpuscle

Blood Vessels The dermal layer is the only vascular portion of the integument. When it is hot, the blood vessels dilate allowing body heat to be released to the skin surface. When it is cold, the blood vessels constrict holding in the body heat.

Hair Produced by a cluster of cells called a hair bulb. Hair strands consists of hard, keratinized epithelial cells The hair follicle is basically an indentation of the epidermis into the dermis. It forms a “pocket” lined with cells that protect the hair as it grows.

Melanocytes surround the hair bulb and give hair its color. The hair root is the part of the hair that is implanted in the skin. The hair shaft is the portion of the hair that we see.

Integumentary Muscles Attached to the hair follicle is a muscle called the arrector pilli. When this muscle contracts, it causes goose-bumps and makes the hair stand up. This smooth muscle contracts involuntarily and helps to keep us warm.

Appendages of the Skin Nails Scale-like modifications of the epidermis Heavily keratinized Lack of pigment makes them colorless, yet the body is pinkish due to blood vessels in the nail bed.

Nail Structures Free edge – the distal end of the finger nail Body – central area; protects the nail bed Root of nail – where growth originates; embedded deep to the proximal cuticle Lunula – white, crescent area on the proximal end of the nail Cuticle – proximal nail fold that projects onto the nail body Nail Bed – the area of tissue underneath the nail.

Nail Structures