What is The Integumentary System?

Despite its understated significance, the Integumentary system is often overshadowed by it more popular counterparts like the Nervous, Cardiovascular, and Respiratory systems

By Amirali Banani

Source: https://makeagif.com/gif/introduction-to-the-integumentary-system-animated-tutorial-complete-anatomy-_uwIjj

The Integumentary System entails the skin and the structures that develop from it, including hair, nails and glands. The skin covers the entire surface of the body and performs many important functions such as protection, regulation of body temperature, sensing the environment, excretion, and the synthesis of vitamin D. It is also considered the immune system’s first line of defense against microbes and other hazards.

Functions of The Integumentary System

Protection

The skin provides a physical barrier between the underlying tissues and the external environment.

Credit: Eucerin

Thanks to this physical barrier, microbes can not enter the body, and internal organs are protected (at least to some extent) from ultraviolet rays from the sun, chemicals, abrasion, and dehydration. Specifically, the skin contains secretions that kill pathogens and the pigment melanin serves as a chemical defense against UV light that can cause damage to skin cells and underlying structures.

Excretion

The production of perspiration by sweat glands in the skin removes small amounts of organic wastes, salts, and water.

Credit: Mayo Clinic Foundation for Medical Education and Research

Temperature Regulation

During periods of excessive heat production by the body, the secretion of perspiration and its evaporation from the body surface helps lower body temperature.

The skin also regulates the flow of blood close to the body’s surface.

Sensory Perception

Skin contains sensitive nerve endings and receptors that detect stimuli associated with touch, pressure, temperature, and pain.

The layers of the skin with the sensory nerve, which allows for sensory perception, at the bottom. | Credit: Johns Hopkins Medicine

Synthesis of Vitamin D

Exposure to ultraviolet radiation converts precursor molecules in the skin into vitamin D.

Vitamin D molecular structure (Source: https://commons.wikimedia.org/wiki/User:NEUROtiker)

Layers of The Skin

The skin consists of 2 major layers: the Epidermis and the Dermis.

Epidermis

The thinner, outermost primary layer of skin that is made up of stratified squamous epithelium. Cells found in the innermost layers of the epidermis undergo mitosis which enables the skin to repair itself.

As cells produced in deep layers of the epidermis move up toward the surface, they are filled with a tough, waterproof protein called keratin and eventually flake off. Meanwhile, the pigment layer produces the brown pigment melanin which is responsible for protecting us from UV radiation.

Credit: Cleveland Clinic

Dermis

The thicker, inner layer that’s composed of dense fibrous connective tissue. The upper regions of the dermis contain projections known as the dermal papillae that produce fingerprints. The deeper areas are filled with collagenous fibres which provide toughness to the skin and with elastic fibers which enable the skin to stretch. The dermis contains nerves, muscles, hair follicles, and blood vessels

Hair

A hair shaft and its accompanying structures (such as the arrector pili muscle) in the skin. | Source: https://training.seer.cancer.gov/melanoma/anatomy/

Consists of keratinized epidermal cells that are formed at the base of a hair follicle. An arrector pili muscle is attached to the side of each hair follicle; it produces “goose bumps” which cause the hair to stand straight up when you are cold or scared.

Glands

The glands associated with the skin are the sebaceous (oil) and sudoriferous (sweat) glands, as shown below.

A cross-section of the skin showing the structures of the sweat (sudoriferous) and oil (sebaceous) glands. | Source: www.a2magazine.co.za

Nails

Protect the dorsal surface of the ends of the fingers and toes. Nails are formed from layers of heavily keratinized epidermal cells.

Receptors

Specialized nerve endings make it possible for the skin to act as a sense organ. These receptors include Meissner’s corpuscles, which detect light touch, and Pacinian corpuscles, which sense vibrations and deep pressure.

Meissner’s and Pacinian corpuscles in the skin. (Source: https://opentextbc.ca/biology/chapter/17-2-somatosensation/)

Temperature Regulation

Normal human body temperature is 37 degrees C (98.6 degrees F). Body heat is produced as a by-product of cellular respiration. When heat loss is excessive, blood vessels in the dermis are constricted to reduce heat loss. Under conditions of extreme heat loss, spontaneous, weak muscle contractions (shivering) produce additional heat.

https://jackwestin.com/resources/mcat-content/skin-system/functions-in-thermoregulation

When heat production is excessive, blood vessels in the dermis dilate to help facilitate heat loss. The body also perspires because evaporating water absorbs heat energy and carries it to the surrounding environment away from the body

Before heading out, I’m going to leave you with one last thing to learn and memorize! If you’re studying the skin and trying to learn the layers of the epidermis in order from most to least superficial, then use this acronym:

Come! Let’s Get Sun Burned! (C.L.G.S.B.)

Stratum Corneum —Stratum Lucidum — Stratum Granulosum — Stratum Spinosum — Stratum Basale

I hope you learned a thing or two about the integumentary system today!

Until next time,

- AB