Glands of human external secretion
All secretion organs that are in the body produce biologically active substances. The latter are used inside or out. Glands of external secretion are characterized by the fact that their secret through the ducts goes to the surface of the body. They regulate intraspecific (or interspecific) relationships.
The glands of external secretion include sweat, sebaceous, those that are responsible for producing tears. They join the milk and gonads. Also, organs such as the liver, pancreas (as well as the organs of secretion of the stomach, intestines) fall into this category. The morphological classification of the external secretion glands is as follows: they differ in shape from tubular, alveolar, and mixed organs (alveolar-tubular). Branching underlies the section on simple and complex (branched). Depending on the chemical composition of secreted secretion, exocrine glands are mucous, protein, sebaceous, mixed.There is also a separation of these organs, which is based on the method of secretion secretion: apocrine (partially the cell is destroyed), merocrin (the gland cell remains), holocrine (the glandular cells are completely destroyed). Each external secretion gland (table below) produces a specific secret.Substances that produce glands
|Name glands||Secret produced|
|Sexual||Seminal fluid, eggs, female sexual secretion|
|Glands of the stomach||Hydrochloric acid, pepsin, mucus|
|Intestinal glands||Intestinal juice|
These external secretion glands have a tubular appearance, they are not branched. On the human body are placed almost everywhere.The exception is the lips, the surface of the genitals. The approximate amount of sweat glands is up to 5 million. Their ends are curled up, the sweat duct goes out through the pores. The secret that stands out in their operation is sweat. 98% of its content is water, the rest is mineral salts.During the day, a person produces about 0.5 liters of sweat. The main task performed by these exocrine glands is thermoregulation. There are apocrine and eccrine secretion organs. The former are large in size, their ducts emerge mainly in places of the greatest hair growth (under the arms, in the groin). They do not take part in thermoregulation, but they react to stressful situations and determine the smell of the secret. The latter are much smaller, they are evenly distributed throughout the body. It is these external secretion glands that maintain a stable body temperature.
Such secretion organs are branched alveolar glands. They are located almost the entire surface of the body. There are no them on the feet and palms. There are places where their number is much higher than in other areas. This is the area of the forehead, chin, that part of the head on which the hair grows, as well as the back. Sebaceous secretion organs are placed at a distance of 0.5 mm from the skin surface. Often their ducts open into hair follicles. The secret that stands out is sebum. It forms about 20 g per day.This substance is used for natural lubrication of hair, skin, giving them elasticity. Another important feature of sebum is its bactericidal ability. Also, this secret is involved in regulating the amount of water that evaporates, prevents the penetration into the skin of some microorganisms.
This organ is located at the outer edge of the eye. Consists of orbital and palpebral parts. They are divided by the tendon of the muscle, which lifts the upper eyelid. The lacrimal glands are alveolar-tubular type. The ducts extend into the conjunctival sac. The substance that secrete such external secretion glands is a tear. Its composition is as follows: water, mineral salts, proteins, lysozyme, urea. During the day, produced 1 ml of tear fluid. If a person is emotionally shocked, cries a lot, then its amount increases to 10 ml. The main function of tears is washing the eyes. This is a cleansing effect, getting rid of small objects (for example, fine sand). In addition, the eyeball is constantly moistened. With age, the number of allocated tears decreases, often people complain of discomfort and dryness.
In the oral cavity of the person are the salivary glands (small, huge). The large include the parotid, sublingual, which are located in the lower jaw. Small organs of secretion are located in the mouth, pharynx and near the upper respiratory tract. The parotid gland has the largest dimensions, its weight is within 30 g. Small ones usually have dimensions of no more than 5 mm. By structure, these are alveolar or alveolar-tubular formations. These glands consist of the body, as well as the excretory duct. The secreted secret is saliva. Its composition includes 99% water, also there are enzymes, mucus, immunoglobulin. The main function of the salivary glands is the primary processing of food. Thanks to their secret, it is wetted, splitting of complex molecules into simpler ones occurs. Even saliva cleans the mouth and teeth, has a bactericidal effect.
On the pectoral muscles of the human body are paired glands - milk. They are altered sweat ducts, consist of adipose tissue, in which there are milk ducts. They are present in both men and women, however, in representatives of the stronger sex in a certain period they cease to develop. Puberty in girls provokes their further growth.The main function performed by the mammary glands is to produce a secret (milk) for feeding the newborn.
This type of secretion organs refers to a mixed type (they function as a gland of internal and external secretion). On the one hand, they release certain hormones that go directly into the blood, on the other - they form germ cells (sperm, eggs). In the female body, the sex glands are represented by the ovaries. They are small in size (approximately 3 * 2 * 1.5 cm), covered with cubic epithelium. Inside are the follicles. They regularly ripen, burst, and thus the egg appears, ready for fertilization. In men, germ cells are formed in the testes. The gland consists of a set of lobules in which the seed canals are located. Procreation is the main task that such external secretion glands perform. The table below contains information about hormones produced by the sex organs of secretion.Sex hormones
|Gland type||The hormone that is produced|
|Ovary||Estrogen, progesterone, weak androgens|
|Seed plants||Testosterone, a small amount of progestin, estrogen|
One of the largest glands in the human body is the liver. Her weight is one and a half kilograms. It is located in the abdominal cavity on the right side. The color of such an external secretion human gland is burgundy, the consistency is rather soft, but dense. This organ is quite complex, it is surrounded by nerve endings and blood vessels. Its structure is as follows: the right and left lobes (the first is large in comparison with the second), the posterior surface (it is formed by the square and tailed lobes). The secret secreted by the liver is bile. The functions of this gland are varied. First of all, bile helps to digest fats. It is produced in the body up to 1 liter, but this secret enters the digestive organs as needed. And before that accumulates in the gallbladder. In addition, the liver is the main filter of our body. Thanks to her, all toxins and poisons are neutralized and do not enter the blood. It is worth noting that iron is especially sensitive to the effects of nicotine and alcohol.
This organ is located behind the stomach.It has an oblong appearance, its weight is 80 g, and its length reaches 25 cm.The head, body, tail are the main components of the gland. It is the second largest (after the liver). External secretion of the pancreas - pancreatic juice. It contains such enzymes: lipase, amylase, trypsin, renin. They play an important role in the digestive process, helping to break down fat, protein and carbohydrate molecules. This gland is also responsible for insulin production, thus regulating the level of sugar.
Glands of the stomach
The stomach is one of the main organs of digestion. Its volume in the normal state is about 500 ml. When filled with food, it can increase by 2 times (sometimes even up to 4 liters). This is where the primary processing of food. Glands of the stomach are located in its mucosa. In the body and the bottom of the organ are the fundic glands. They consist of this type of cells: main, occlusive, additional. The former are responsible for producing pepsinogen, the latter for hydrochloric acid, and the latter for mucus. The cardiac glands are located in the cardiac part of the stomach (mainly responsible for the production of mucus).The pyloric secretion glands produce little. Gastric juice in its composition has hydrochloric acid, sulfates, compounds of sodium, calcium. The amount of secretion that these glands are capable of producing reaches 2 liters. On average, food is in the stomach for 2 hours. During this time, it is partially digested.
The small intestine has the appearance of a long tube, consists of the duodenal, jejunum and ileum. In the intestine, the digestive process goes through its main stage. It is there that the hydrolysis of the main substances occurs. This is done through intestinal juice, which is produced by the Brunner and Liberkun glands. They are located around the perimeter of the intestine. The first type of gland helps to convert the acidic food mass into alkaline. In addition, they produce mucin, which protects the intestinal walls from damage. The liberkun glands produce digestive substances. Their secret contains about 20 enzymes that help complete digestion. In the intestine, it occurs in three stages: band, parietal, membrane. In humans, up to 3 liters of intestinal juice can be released.