Integumentary System Study Guide: Skin, Nails and Hair

Introduction

Ever heard of the integumentary system? Don’t feel bad if the answer is no, most people haven’t either. Despite being the largest organ system in the human body, it’s not really talked about that much. Everybody loves the fun shiny ones like the nervous or cardiovascular systems, leaving our old pal integumentary hiding in the wings. It remains, however, our unsung hero. Not the one we deserve, but the one we need right now. Read on to find out why.

Lesson Objectives:

• Understand the different parts that make up the integumentary system.
• Briefly understand the functions of the integumentary system.

The Integumentary system:

The Integumentary System is a set of organs that form the outermost layer of the body. Functions of the integumentary system include vitamin D synthesis, sensory touch, temperature regulation, and more–but its primary function is to form a protective barrier between us and our environment, but that’s not where it ends. There are four parts that make up this system: the skin, hair, nails, and exocrine glands. Let’s talk about each of these below and elaborate on their structures and what functions they serve in the body.

Skin

Even though Skin is only a few millimeters thick, it’s actually the largest organ in the body (by like, a lot). The second largest organ in the body is the liver, and it weighs about 3 pounds. Skin, in comparison, weighs somewhere between 6 and 9 pounds, accounting for about 15% of our body weight on average!

The primary purpose of your skin is to form a protective barrier between your insides and the outside. It has 3 different layers to help it do so: the epidermis, the dermis, and the hypodermis. Take a look at the 3D model to visualize each layer as we go through them below.

• The Epidermis is the outermost layer of the skin that gives it a strong, protective covering. The epidermis has 5 layers: the basal cell layer, squamous cell layer, stratum granulosum, stratum lucidum, and stratum corneum.

• The Dermis is the layer of skin found beneath the epidermis. It contains nerve endings, sweat and oil glands, hair follicles, and blood vessels.

• The Hypodermis is the final, fatty layer of skin that lies between the dermis and your organs (it’s also sometimes referred to as subcutaneous tissue). Note how thick the hypodermis is compared to the dermis and epidermis.

The skin is pretty versatile as far as organs go. Besides serving a protective barrier, it has a bunch of other functions in the body, which we’ll briefly touch on below.

• UV Radiation Protection: the skin contains a pigment called melanin that reduces the harmful effects of UV rays (emphasis on reduces–they can still cause melanoma (skin cancer), blisters, and even first-degree burns in some cases, so keep wearing sunscreen!).

• Sensory Function: nerves found in the skin allow you to feel things like touch and temperature.

• Temperature Regulation: the blood vessels in the skin dilate when you’re warm to increase blood flow at the surface where heat can be released. Conversely, to conserve heat, they constrict when you’re cold.

• Vitamin D Production: when UV rays from sunlight hit your skin, they set off a chain chemical reaction that ends with the production of vitamin D.

• Immune organ–the skin serves as a physical barrier against bacterial infections, and has a series of innate and adaptive immune responses to fight infections should they arise. Additionally, it has something called skin immunity, which allows it to resist infections from pathogens.

Hair

Hair –you spend all this time washing it, conditioning it, cutting it, and brushing to keep it nice and healthy, but what does hair do for you? It’s not as much of a freeloader as you’d think. Hair is made up of protein called keratin and contains very small amounts of lipids (fats) and water. It consists of 3 main parts: the hair shaft, root, and follicle.

Source

• The Hair Shaft is visible from the outer layer of skin (remember what it’s called?). Even though it looks like they’re on the outside, they actually emerge from follicles found in the dermis.

• Hair grows from Follicles, sac-like pits located in the dermis. Follicles are made up of epithelial cells, the cells that line all of the organs of the integumentary system, forming a protective barrier.

• The Root, or hair bulb, is a soft, thickened bulb found at the base of a hair strand. It’s surrounded by the follicle and is attached to a tiny arrector pili muscle (which is what makes your hair stand up when you’re scared or cold!).

Now that we’ve gone over that, back to what hair does for you. It serves 3 main functions in your body that we’ll quickly go over below.

• Protection: think about how your hair protects your scalp from the sun on a hot day, or how your eyebrows keep sweat from dripping into your eyes, or how your nose hairs catch allergens to keep them out of your body.

• Body Temperature Regulation: when you’re cold, the arrector pili makes your hair stand up to trap a layer of air to add insulation.

• Sensory Function: each follicle is surrounded by a hair root plexus, a network of nerves that make your hair extremely sensitive to things like air movement or other disturbances in the environment (it’s even more sensitive than skin!).

Nails

We don’t know about you, but we could definitely use a manicure right now. But now is not the time to paint our nails, it’s time to talk about them. Nails are accessory structures to the skin, meaning they work alongside it to help it function. Nails consist of several pieces: the nail plate, nail bed, cuticle, nail folds, lunala, and matrix. Once again, check out the 3D model and see if you can identify each part of the nail as we go through them.

• The Nail Plate is the hard, exterior part of the nail (the part that you paint). It’s composed of keratin, a protein that makes them hard, yet flexible.

• The layer of skin found beneath the nail plate is called the Nail Bed.

• The Cuticle is the thin line of tissue located at the base of your nail, overlapping the nail plate.

• The folds of skin on the sides of the nail plate are called (aptly) Nail Folds. They help seal the edges of the nail to protect the underlying tissues from infection.

• The Lunala is the white colored half-moon shape at the base of your nail plate (remember its name by thinking of the moon, “la luna”).

• The Matrix of the nail is located underneath the cuticle and is not visible from the outside. It’s responsible for nail growth. As it generates new cells, the old ones are pushed forward to make room–which is what makes your nails grow!

Aside from being a fantastic canvas on which to express yourself with nail polish, your nails pretty much serve two main functions:

• Protection: they provide a hard, exterior shell to protect your fingers and toes from injuries and trauma.

• Sensory Enhancement: your nails assist your sense of touch and enhance sensation (try brushing something using just your nail to test it out!).

Exocrine Glands

Exocrine Glands pretty much do it all. They make sweat, tears, saliva, milk, and digestive juices (a delightful cocktail of fluids) which they release either into or out of the body. There are tons of these glands all over you, but since we’re talking about the integumentary system, we’ll focus on just four–the sudoriferous glands, sebaceous glands, ceruminous glands, and mammary glands.

• The Sudoriferous Glands, or sweat glands, excrete sweat through tiny openings in your skin’s surface called sweat pores. This sweaty secretion cools the body’s internal temperature through condensation when exposed to high levels of heat.

• The tubular glands found in the dermis are the Sebaceous Glands. They release an oily substance called sebum into the hair follicle to protect and lubricate the hair shaft, keeping it soft and malleable. They also release sebum from pores over the rest of your body, including your face. When sebum, dead skin cells, and bacteria build up too much in a pore, they create a blackhead.

• The Ceruminous Glands are located in the ear canal. They work in conjunction with the sebaceous glands to produce ear wax (yet another lovely substance created by the exocrine glands). Ear wax protects your body against the entry of harmful foreign agents like bacteria and fungi.

• There are two Mammary Glands located on the interior of each side of the chest wall. Their primary function is to provide breast milk after the birth of a child. You might be surprised to know that both females and males have mammary glands, but the ones in males are underdeveloped.

💡 Summary

• The Integumentary System is a set of organs that form the outermost layer of the body. It is composed of 4 parts: the skin, hair, nails, and exocrine glands.

• The skin is the largest organ in the human body composed of 3 layers: the epidermis, dermis, and hypodermis.

• The epidermis is the outermost layer of the skin and it gives it a strong, protective covering. The dermis is the layer beneath the epidermis containing sweat and oil glands, hair follicles, and blood vessels. The hypodermis is the thick, fatty layer beneath the dermis.

• The primary functions of the skin are to form a protective barrier between the internal body and external environment, protect against UV radiation, allow us to feel touch and temperature, produce vitamin D, and serve as a part of the immune system.

• Hair is made primarily of keratin and consists of 3 parts: the hair shaft, follicle, and root.

• The hair shaft is visible from the outside and emerges from the follicles, sac-like pits formed by epithelial cells. The root is surrounded by the follicle and is attached to an arrector pili muscle.

• The primary functions of hair are protection, body temperature regulation, and sensory function.

• Nails are accessory organs of the skin. They are composed of a nail plate, nail bed, cuticle, nail folds, lunula, and matrix.

• The nail plate is the hard yet flexible exterior of the nail. The layer of skin beneath the nail plate is the nail bed. The cuticle is a thin line of tissue that overlaps with the base of the nail plate. The nail folds seal the edges of the nail plate and protect underlying tissue from infection. The lunula is the half-moon shape at the base of the nail plate. The matrix is located underneath the cuticle and is where nails grow from.

• The primary functions of nails are protection and sensory enhancement.

• Exocrine glands produce and release different substances into and out of your body. There are four types of exocrine glands in the integumentary system: the sudoriferous, sebaceous, ceruminous, and mammary glands.

• Sudoriferous glands excrete sweat through the pores and help cool the body. Sebaceous glands release sebum into the hair follicle to protect and lubricate the hair shaft. The ceruminous glands are located in the ear canal and work with the sebaceous glands to produce earwax. The mammary glands excrete milk and are found on both sides of the chest wall.

FAQs

1. What are the four parts of the integumentary system?

The skin, hair, nails, and exocrine glands.

2. What are the three layers of skin?

The epidermis, dermis, and hypodermis.

3. What is the primary function of your skin?

To form a protective barrier between your internal and external environment.

4. What parts of the integumentary system helps regulate body temperature?

The skin, hair, and exocrine glands.

5. What is the name of the white, half-moon shape at the base of your nail?

The lunala.

6. What are the primary functions of nails?

Protection and sensory enhancement.

7. What glands are also known as the sweat glands?

The sudoriferous glands.

8. What are the three parts that make up hair?

The hair shaft, follicle, and root.

9. What two glands work together to produce earwax?

The ceruminous and sebaceous glands.

10. Where is the matrix of the nail found?

Beneath the cuticle.

Bonus: …what color should we paint our nails?

We hope you enjoyed studying this lesson and learned something cool about the Integumentary System! Join our Discord community to get any questions you may have answered and to engage with other students just like you! Don’t forget to download our App to experience our fun, VR classrooms – we promise, it makes studying much more fun!😎

Continue your learning journey by learning about more organs

1. Respiratory Organs Study Guide
2. Male Reproductive Organs Study Guide
3. Digestive System Organs Study Guide
4. Female Reproductive System Guide

Sources:

1. Christiansen, Sherry. “The Integumentary System: Your Skin, Hair, Nails, and Glands.” Verywell Health, 10 Mar. 2021 www.verywellhealth.com/the-integumentary-system-anatomy-and-function-5114485. Accessed 25 Oct. 2021.

2. Kim, Joyce Y., and Harry Dao. “Physiology, Integument.” PubMed, StatPearls Publishing, 2020, www.ncbi.nlm.nih.gov/books/NB

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