Apocrine glands: structure, functions and location

2024 Author: Priscilla Miln | [email protected]. Last modified: 2023-12-16 00:21

Animals, like humans, have secretory glands in the body. They differ somewhat in structure and their functions. For example, both humans and animals have apocrine sweat glands. However, in dogs or cats, it is impossible to see the sweat coming out. In this article, we look at the structure, location, and function of the apocrine glands in cats and dogs.

Structure of glands

Apocrine glands are sweat glands that perform a secretory function. The appearance of the sweat glands is quite simple, but the contribution made to the work of the body is very large. They are tubular and not branched, at the ends they have secretory sections that go deep into the dermis. Accumulations of those very end sections form dense tangles in the layers of the skin.

The cells that make up the end sections are of two types: cubic (glandular) and process (myoepithelial). It is the process cells that regulate secretion from the ducts. They cover with their processesduct and, contracting, advance the secret along the duct.

The end section of the sweat glands looks different in cats and dogs. For the former, it is a tangle, while for the latter it is tortuous.

Types of sweat glands

It is customary to distinguish between eccrine (merocrine) and apocrine glands. The former are mainly localized on those areas of the skin where there are no hairs and their derivatives. With their help, the secret is allocated directly to the stratum corneum.

And the apocrine glands, on the contrary, are associated with the hairy areas of the skin. Their ducts exit into the hair follicles, which in turn are located slightly above the sebaceous glands. In addition, the secretion of the apocrine glands is very rich in proteins.

Human sweat glands

The human body is dominated by small eccrine glands, since the body is not covered with much hair. They secrete watery sweat. It plays an important role in thermoregulation. The intensity of the work of the eccrine sweat glands depends on many factors, including the ambient temperature and the emotional factor.

The sweating system is regulated by the endocrine and nervous systems. The main role in regulation is played by the brain and spinal cord. In tetrapods, this type of gland is localized on the paw pads. Because dogs don't sweat the way humans do, it's commonly believed that they lack apocrine sweat glands. However, this opinion is erroneous.

Sweating in dogs

Because the body of most dogs is covered with thickhair, then they are dominated by large apocrine glands, which are associated with hair follicles. These glands are also predominant in most mammals.

In the secret of animals, the content of organic substances is increased. In particular, the secret of dogs is thicker and more odorous. It, in turn, mixes with the secretion of the sebaceous glands and forms a natural grease in the skin of animals.

Apocrine glands in dogs are located in certain areas of the body, unlike eccrine glands. Another distinctive feature of this type of glands is that they begin to perform their functions only after the puberty of the individual. The apocrine glands include the glands of the eyelids and those that secrete earwax.

Despite the fact that dogs and other animals with dense hair cover have almost no thermoregulation, their excretory system works at full capacity. In particular, sweating becomes more abundant in case of illness of the animal. In this case, their body tries to get rid of harmful substances.

The figure shows the skin glands of dogs: 1 - apocrine gland, 2 - eccrine, 3 - sebaceous.

Skin glands of cats

In cats, the excretory system is very similar to that of a dog. They have sebaceous, sweat and mammary glands. The former help make the coat water-repellent. Perhaps that is why many cats and cats do not like water procedures.

As we already mentioned, the glands that produce liquid sweat, like in humans, in cats are located only on the pads of their paws. The function of thermoregulation is performed by milk sweatglands. They secrete a liquid similar to milk. However, the cooling of the body is still small. The most important thing this liquid does is smell. Animals use this to mark their territory. They simply rub against something, leaving a scent mark on the object.

Glandular diseases

The named glands have their own diseases. For example, an apocrine cyst. This is a benign tumor-like pathology, which is a cavity filled with contents. Inflammation of the apocrine glands is expressed by adenomas and adenocarcinomas. They can affect the glands themselves or the cells that make them up.

Usually these pathologies are not common among young cats and dogs. But they strike older animals with an enviable frequency. For example, German Shepherds and Golden Retrievers are most susceptible to apocrine tumors. Among cats, the Siamese breed is most likely to develop carcinomas.

Adenomas in dogs

Externally, an apocrine cyst looks like a subcutaneous nodule that rises above the surface of the skin and contains fluid. Its size can vary from 0.5 to 3 cm. Their most frequent localization is on the head of the animal. Cysts may feel hard and firm to the touch, and may also be bluish in color.

Dogs can also develop carcinomas, which are mainly found in cats. These are usually solitary tumors that are very similar to adenomas. That is why it is importantthe question remains of correct differential diagnosis, and hence treatment.

In tetrapods, the most common locations for adenomas and other inflammations of the sweat glands are the head, neck, torso and paws.

Carcinomas in cats

In representatives of the Persian and Himalayan breeds, tumor formations of the apocrine glands often appear on the eyelids. They are small in size - from 2 to 10 mm. As we already mentioned, adenomas and carcinomas can be very similar in appearance, which in turn makes it difficult to diagnose and select the right treatment. However, it should be kept in mind that carcinomas look more solid and inflamed. In addition, they may be riddled with ulcers and suppuration.

Tumors are the same as in dogs, mostly solitary. Outwardly, they resemble subcutaneous compacted balls of small size and bluish color. Carcinomas can be located anywhere on the animal's body. Adenomas can also appear in cats, but they are localized to a greater extent in the head area.

Apocrine metaplasia of the breast

Inflammatory diseases of the mammary glands are bred into a separate class. Since it is in cats that they perform the important function of thermoregulation and limiting their territory, you need to be able to recognize the onset of the disease in time in order to avoid sad consequences. However, do not forget that dogs are also susceptible to this pathology.

The causes of the development of breast tumors may be the following factors:

1. Age. In dogs, neoplasms appear most often in the period from 7 to 10 years. The older the animal, the less likely it is to develop tumors. In cats, the situation is the opposite. In their case, the disease is more likely to develop in older animals.
2. Castration and sterilization. The sooner these procedures are carried out, the less likely the occurrence of tumors. However, it should be borne in mind that previous pregnancies do not affect the incidence and risk of the disease. Moreover, veterinarians claim that intermittent delivery and feeding of the litter with milk is a kind of prevention of the development of mammary tumors in both dogs and cats.
3. Suppression of estrus. The use of various hormonal drugs, which are based on progesterone, increase the likelihood of mastopathy. Although these tumors are benign, they are still classified as precancerous and should be avoided.
4. Gender. Typically, breast cancer is predominantly a problem in female cats and dogs. However, males can also develop neoplasms. But they will be of a slightly different nature, since males do not have mammary glands, but have a mammary gland. It also has ducts in its structure, which can be prone to the formation of tumors.