Integumentary System

Integumentary System

The integumentary system includes the skin, hair, and nails. Its major roles are to protect the body, provide sensation, help regulate temperature, and allow sunlight to support vitamin D production.

Main Functions

• Protection: Skin helps keep bacteria and foreign material out of the body.
• Sensation: Receptors and nerves in the skin detect touch, deeper pressure, and pain.
• Temperature regulation: Blood vessels can widen to bring blood closer to the surface and release heat. Sweat also cools the body as it evaporates.
• Vitamin D production: Sunlight helps the body make vitamin D, which is needed for calcium and phosphorus to enter bones. Severe vitamin D deficiency can lead to rickets.

Skin Layers

From the outside inward, the video describes three main layers:

1. Epidermis

   • The outer layer. It has no capillaries, so nutrients reach its cells by diffusion from below.
   • New cells form near its base, move upward, and eventually die and shed.
   • A tattoo must reach below the epidermis to remain, since surface cells are continually replaced.

2. Dermis

   • Contains blood vessels, glands, nerves, and sensory receptors.
   • Sweat glands release sweat; sebaceous glands release oil that helps waterproof the skin and hair.
   • Receptors nearer the surface detect lighter touch, while deeper receptors detect stronger or deeper pressure. Pain receptors help warn of potential damage.

3. Hypodermis (subcutaneous layer)

   • Lies beneath the dermis and contains connective tissue and fat.
   • Also contains stem cells, macrophages, and elastic and reticular fibers. Elastic fibers help skin return to shape after being pulled.

Epidermal Strata

From the deepest layer to the surface:

• Stratum basale: Produces new cells through mitosis and anchors the epidermis to the dermis via its ridged structure.
• Stratum spinosum: Named for its spiny appearance under certain staining.
• Stratum granulosum: Cells become compressed as they move upward and begin to die.
• Stratum lucidum: Present in thick skin, such as the palms and soles; absent from thin skin.
• Stratum corneum: The outer layer of dead cells, which are gradually shed and replaced.

The video offers the phrase “Come, let’s get sunburned” as a memory aid, then reviews the layer initials as B-S-G-L-C, from bottom to top.

Pigmentation

• Melanocytes produce melanosomes containing melanin, which contributes to skin color.
• Melanin levels reflect differing balances between protection from sunlight and the body’s need to produce vitamin D.

Hair and Nails

• Hair grows from a follicle. Cells in the follicle’s matrix continually produce new cells; as they move upward, they die and form hair, which is rich in keratin.
• Nails also grow from a matrix. Their cells die as they form the keratin-rich nail. Tissue at the nail’s base forms the cuticle.
• Nails evolved from claws in other organisms and help humans handle tools.

Speaker and Source

• Speaker: Mr. Anderson (Paul Andersen, as identified in the video context)
• Video source: Bozeman Science