Integumentary System Overview

Study Notes

Integumentary System

The Integumentary System is comprised of skin, hair, nails, and glands.
Integument means covering.
The system protects the body from abrasion and ultraviolet light, prevents water loss, and keeps microorganisms out.
The Integumentary System contains sensory receptors for heat, pain, cold, touch, and pressure.
When exposed to UV light, the skin produces vitamin D, which regulates calcium homeostasis.
Blood flow and sweat glands help regulate body temperature.
Waste products are secreted through the Integumentary System.

### Skin Layers

The skin is made of two main layers: the epidermis and dermis.
The epidermis is the most superficial layer, made of epithelial tissue, and provides protection.
The dermis is a layer of dense connective tissue, ten to twenty times thicker than the epidermis, and provides structural strength.
The subcutaneous tissue, not part of the skin, connects it to underlying muscles or bones.

Epidermis

The epidermis is stratified squamous epithelium.
New cells are produced by mitosis in the deepest layers.
Epidermal cells prevent water loss and abrasion.
The outermost cells of the epidermis protect underlying cells.
The deepest cells of the epidermis replace cells lost from the surface.
As epidermal cells move toward the surface, they change shape and chemical composition.
This movement is called keratinization.
During keratinization, cells fill with the protein keratin, making them more rigid and durable.
As keratinization progresses, cells die and form a layer of dead, rigid cells that resist abrasion and act as a permeability barrier.

Epidermal Layers

The layers of the epidermis are called strata.
Stratum Basale consists of cuboidal or columnar cells that divide mitotically every 19 days.
- One daughter cell becomes a new stratum basale and continues dividing.
- The other daughter cell is pushed toward the surface, taking about 40-56 days.
- As cells move to the surface, changes in the cell create intermediate strata.
Stratum Spinosum consists of flattened cells that accumulate lipid-filled vesicles called lamellar bodies.
Stratum Granulosum consists of flat, diamond-shaped cells.
- Cells in the stratum granulosum accumulate more keratin and release lamellar body contents into the extracellular space.
- The cells' nuclei degenerate and they die, giving the layer a grainy appearance.
Stratum Lucidum is a thin, clear zone found only in thick skin (areas subject to friction and pressure, like palms, soles of feet, and fingertips).
Stratum Corneum is the most superficial layer of the epidermis.
- Composed of dead squamous cells filled with keratin, providing structural strength.
- Stratum corneum cells are coated with lipids released from lamellar bodies, acting as a waterproofing material, preventing fluid loss.
- The stratum corneum is made up of 25 or more layers of dead squamous cells joined by desmosomes.
- Excessive sloughing of stratum corneum cells from the scalp is called dandruff.
- In areas subjected to friction, the number of layers in the stratum corneum increases, producing a thickened area called a callus.
- The stratum corneum can thicken to form a cone-shaped structure called a corn.

Description

Explore the structure and functions of the Integumentary System, including its components like skin, hair, nails, and glands. Learn about the layers of skin, how they protect the body, and their role in sensory reception and temperature regulation.