Sweat gland

Your skin has tiny parts that make sweat.

These parts help you stay cool. They make water come out of your skin. This helps when you are hot.

Some parts are all over your body. They are mostly on your hands and feet. These parts make clear, salty water. This water helps your body stay at the right heat.

Other parts are only in a few spots. You have them in your armpits. These parts make a thicker liquid. They do not help you cool down.

Small parts in your ears make wax. Other parts help make milk. These are special kinds of sweat parts too.

Your body uses these parts to stay healthy. It is a smart way to work.

Your skin has tiny tubes called sweat glands.

These glands make sweat to help your body. There are two main kinds of sweat glands.

One kind is called eccrine glands. These are found almost everywhere on your body. You have many on your palms and soles. They make a clear, salty liquid. This liquid is mostly water. When the water dries on your skin, it helps you cool down. This is a key way humans stay at a safe heat.

The other kind is called apocrine glands. These are mostly in your armpits. They are larger than eccrine glands. They make a thicker, oily liquid. This liquid does not help you cool down. Instead, it can lead to body odor when bacteria on your skin break it down. These glands start working when you reach puberty.

Some glands are very special. For example, glands in your ears make ear wax.

Other glands help make milk. Your body uses these parts to stay healthy and keep working well.

Your skin is home to tiny, tube-like structures called sweat glands.

These glands are a type of exocrine gland. This means they make substances and send them to the surface of your skin through a small path called a duct. Sweat glands are very important for keeping your body healthy. They help you stay cool when you are hot. They also help your body get rid of extra water and salts.

There are two main types of these glands in humans. The first type is called eccrine glands. These are found almost everywhere on your body. You have the most of them on your palms and the soles of your feet. They make a clear liquid that is mostly water. When this water evaporates, it cools your skin down. This is a primary way humans manage their body heat.

The second type is called apocrine glands. These are mostly found in your armpits and other specific areas. They are larger than eccrine glands. Instead of opening to the skin, they empty into a hair follicle. These glands make a thicker, oily liquid. This liquid does not help you cool down like the other kind does. Instead, it can provide food for bacteria on your skin. When bacteria break down this liquid, it creates a strong smell.

Scientists have studied these glands for a long time. Marcello Malpighi first identified the pores of the eccrine glands. Later, Johannes Purkinjé discovered the sweat glands themselves in 1833. In 1887, Louis-Antoine Ranvier separated them into different kinds. He looked at how they secreted their liquids. By 1917, researchers had divided them into the apocrine and eccrine groups we know today.

Different parts of your body have different amounts of these glands. For example, your palms have about 370 glands in every square centimeter. Your forehead has much fewer, with about 175 per square centimeter. Your back and legs have the least, with only 60 to 80 per square centimeter. Some glands are even modified to do special jobs. Glands in your ears make ear wax, and glands in your eyelids help your eyes.

Sweat glands, also known as sudoriferous glands, are small tubular structures located within the skin.

They belong to a category called exocrine glands. These glands produce specific substances and secrete them onto an epithelial surface through a path called a duct. In humans, these glands are vital for maintaining homeostasis. They help regulate body temperature and provide a route for excreting water and electrolytes.

Every sweat gland follows a specific mechanical process to function. The structure begins with a secretory unit, often called a secretory coil or base. This coil is set deep within the lower dermis or hypodermis. The entire gland is surrounded by adipose tissue, which is body fat. To move the sweat, contractile myoepithelial cells surround the secretory coils. When these cells contract, they facilitate the excretion of the product through the duct. The very end of the duct that opens to the skin is called the acrosyringium.

There are two primary types of sweat glands: eccrine and apocrine. Eccrine glands are distributed almost everywhere on the human body. They have the highest density on the palms and soles, followed by the head. These glands produce a clear, water-based secretion known as sensible perspiration. This liquid is 98% to 99% water and contains electrolytes like sodium chloride. Its main job is thermoregulation through evaporative cooling.

Apocrine glands differ significantly in structure and location. In humans, they are mostly limited to the axillae, or armpits, and the perineal area. These glands are larger than eccrine glands and secrete into the pilary canal of a hair follicle. Their secretion is thicker, oily, and contains proteins, lipids, and steroids. Unlike eccrine sweat, apocrine sweat is not used for cooling in humans. Instead, it contains pheromone-like compounds. When bacteria on the skin decompose this secretion, it creates an acrid odor.

Scientists have spent centuries mapping these tiny structures. The Italian physiologist Marcello Malpighi first identified the pores of eccrine glands. Later, the Czech physiologist Johannes Purkinjé discovered the glands themselves in 1833. In 1844, Karl Krause investigated how gland density changes across different body regions. In 1887, Louis-Antoine Ranvier classified glands by their secretion types. Finally, in 1917, the distinction between apocrine and eccrine glands was fully established.

Sweat gland density varies greatly depending on the body part. According to Henry Gray's estimates, the palms have roughly 370 glands per square centimeter. The back of the hand has about 200 glands per square centimeter. The forehead contains approximately 175 glands per square centimeter. Areas like the breast, abdomen, and forearm have about 155 glands per square centimeter. The back and legs have the lowest density, with only 60 to 80 glands per square centimeter.

Some glands are actually modified versions of the apocrine type. Ceruminous glands are located near the ear canals and produce cerumen, or earwax. Mammary glands use apocrine secretion to produce milk. Ciliary glands in the eyelids are also modified apocrine glands.

Furthermore, some glands are classified as apoeccrine. These are found in the armpits and perianal region. They are intermediate in size between eccrine and apocrine glands. They can comprise up to 50% of all glands in the armpit area. They secrete a thin, watery sweat and are sensitive to cholinergic activity.