Regents Biology

36.3 – The Integumentary System

Regents Biology

  The skin, hair, nails, and a variety of glands make up the integumentary system.

  The skin is the largest organ in the body.

Integumentary System

Regents Biology

Functions   serves as a barrier

against infection and injury

 helps to regulate body temperature

  removes waste products from the body

 provides protection against ultraviolet radiation from the sun

Regents Biology

The Skin  made up of two main

layers:

- epidermis (dead outer layer, living inner layer)

- dermis

 Beneath the dermis is a layer of fat (hypodermis) and loose connective tissue that insulates the body.

Regents Biology

Epidermis

Dermis

Hypodermis

Hair follicle Sweat pore

Nerves

Muscle

Sweat gland

Fat

Sebaceous gland

Hair Blood vessels

Regents Biology

  Cells in the inner (living) layer undergo rapid cell division, producing new cells that push older cells to the surface of the skin.

  Older cells flatten and their organelles disintegrate.

  Older cells make keratin (a fibrous protein). When these cells die, they form a waterproof covering on the skin’s surface.

  The epidermis also produces melanin (brown skin pigment).

Regents Biology

Regents Biology

The Dermis   inner layer of the skin

  contains collagen fibers, blood vessels, nerve endings, glands, sensory receptors, smooth muscles, and hair follicles

  contains two major types of glands (sweat glands and sebaceous (or oil) glands

Regents Biology

Cooling and Excretion   When sweat evaporates, it cools the body.   Sweat also gets rid of wastes from the blood, along

with water.   Sebaceous glands produce an oily secretion called

sebum.   Sebum spreads out along the surface of the skin and

helps to keep the skin flexible and waterproof.

Regents Biology

Hair and Nails

Regents Biology

Hair  Hair covers most body surfaces.

 Hair protects the scalp from ultraviolet light from the sun, provides insulation from the cold, and prevents dirt and other particles from entering the body.

  Hair is produced by hair follicles (tube-like pockets of epidermal cells).

  An individual hair is a column of cells that have filled with keratin and died.

Regents Biology

Nails  Nails grow from rapidly dividing cells in the nail root.

 The nail root is located near the tips of the fingers and toes.

 During cell division, cells fill with keratin and produce a plate-like nail that covers and protects the fingertips and toes.