The mammary glands begin to develop in the embryos of cattle, sheep, horses from the skin epithelium and mesenchyme on the abdominal wall in the area from the umbilical cord to the pubic region, in the embryos of pigs and dogs - from the sternum to the pubic region. Epithelial cells multiply and longitudinal thickenings form on the skin on the right and left sides of the medial sternal groove and from the linea alba. These thickenings are called milky stripes or ridges. Later, in pre-fruits, milk lenses are clearly visible on the milk ridges in the form of rounded thickenings of the skin epithelium and underlying mesenchyme.
The number of mammary lenses is equal to the number of mammary gland lobes with nipples in a given animal species. In pre-fetuses and fetuses, parts of the mammary glands develop from mammary lenses.
The epithelium of milk lenses forms a cone-shaped outgrowth into the subcutaneous layer. At the end of this epithelial outgrowth, tree-like outgrowths of the epithelium arise. Around them a connective tissue framework is formed from reticular, loose and adipose connective tissue. A slit-like cavity of the nipple and milk cistern appear inside the epithelial flask. The center of the epithelial bulb rises together with the skin covering it and forms the nipple. The named parts of the mammary gland primordia are expressed in the fetal period of development in heifers at the fourth month, in pigs at the end of the second month. Subsequently, before birth, new epithelial tree-like growths grow. The amount of fatty, reticular, loose connective tissue increases.
In a newborn heifer, the udder has relatively developed nipples and an undeveloped body. Each lobe has a cistern and milk passages, from which cords come epithelial tissue, surrounded by loose connective, reticular, adipose tissue. At the site of future alveolar tubes there are microscopic thickenings of epithelial tissue.
Heifers aged 12-15 months have an udder body and teats; the udder body is relatively undeveloped. At the ends of the epithelial strands of the ducts, separate alveoli and alveolar tubes appear.
At 2-3 months of pregnancy, the number of alveoli and alveolar tubes in the lobules begins to increase. At 7-8 months of pregnancy, increased development and growth of the glandular tissue of the udder is noted. Before calving, the epithelium of new alveolar tubes multiplies, blood circulation in the udder increases, and colostrum secretion begins. The udder increases in volume, colostrum begins to be released, intensive secretion of which continues for a week after calving and is then replaced by milk secretion.
During the dry period (cessation of lactation before calving), the total volume of the udder decreases and a significant number of blood capillaries collapse. A significant part of the alveolar tubes and ducts is filled with leukocytes and a mass of cytoplasm of dying epithelial cells. They collapse inside and interlobular ducts. The thickness of the layers of loose, reticular and adipose tissue inside the lobes and lobules of the mammary gland increases 2-3 times. Before calving, blood circulation in the udder increases, the epithelium of the alveoli in the lobules regenerates, and the udder increases in volume. The secretion of colostrum begins.
In pigs after farrowing, those lobes of the mammary gland whose nipples are sucked by piglets develop and increase in volume, while the rest increase slightly.
Breed-specific structural features of the mammary glands are manifested in the volume, shape of the udder and the quantitative ratios of glandular and connective tissue within the lobes of the glands. In cows of beef breeds, which produce 800-1000 liters of milk per season, the udder of a primitive, flat or goat shape predominates; the glandular tissue in the lactating udder occupies half the mass of the lobe. In dairy cows with a milk yield of 3-5 thousand liters of milk per year, glandular tissue makes up 2/3-3/4 of the udder; a cup-shaped or bath-shaped udder predominates.
Lecture No. 15,16. Species features of the structure of the mammary gland. Mastitis of farm animals – 4 hours
Lecture outline:
Morphofunctional characteristics of the mammary gland Species features of the structure of the mammary gland in females Lactation Milk secretion and lactation, milk production. Udder examination
The mammary gland, udder - (uber, mamma, mastos) is a glandular organ consisting of lobes, each of which ends at the bottom with a nipple. Some cows have two, less often four additional lobes, usually poorly developed, lacking glandular tissue and a teat canal. The skin of the udder is covered with delicate sparse hair; on back surface In the udder they grow from bottom to top and to the sides, forming the so-called milk mirror. The shape and size of the milk mirror varies. The udder fits tightly to the ventral abdominal wall and is held in position by the suspensory ligament of the udder and fascia.
Components of the udder: glandular tissue, excretory ducts, interstitial connective tissue, blood vessels, lymphatic vessels and nerves. The right and left halves of the mammary gland are separated from one another by the suspensory ligament of the udder, which serves as a continuation of the yellow abdominal fascia. Under the skin is the superficial fascia of the mammary gland, covering each half of the udder. The superficial fascia is followed by its own fascia, covering the glandular part of the udder and giving branches (trabeculae) into the parenchyma, dividing it into quarters and individual small lobules; each lobule is surrounded by an interlobular connective tissue membrane.
The parenchyma of the udder consists of glandular alveoli and excretory ducts, which form an independent, separate system in each quarter of the udder. The alveoli are lined with secretory cells that produce milk. Small ducts depart from the alveoli, which unite to form the middle ducts. The areas of parenchyma with these ducts form independent lobules of the udder, surrounded by a more or less pronounced layer of interlobular connective tissue.
The middle ducts, heading down towards the nipple, merge and give rise to 12-50 wide excretory ducts - milk passages that flow into the cistern. Milk tank - the cavity of the nipple, sometimes extending upward into the parenchyma of the udder, serves as a reservoir for milk.
The nipples are conical, blunt-ended branches of the mammary gland. The nipple has a base that passes without sharp boundaries into the body of the udder lobe, an apex that freely hangs down, and a cylindrical part located between the apex and the base of the nipple.
Lactation– manifestation of a complex neurohumolar reaction of the whole organism to nerve impulses, coming from the receptors of the skin of the mammary gland during sucking or milking, as well as arising due to irritation of chemoreceptors blood vessels glands and other organs.
Milk secretion is inextricably linked with milk production without milk release (when milk or colostrum is not milked or sucked due to the death of the offspring). An important factor in lactation is irritation nerve endings located in the walls of blood vessels, mammary choirs and in the skin of the mammary gland. Irritation of the nerve endings of the skin of the mammary gland and especially the nipple (massage, milking, sucking) is transmitted through nerve pathways to the cerebral cortex. In response to these irritations, nerve impulses go from the center to the periphery to the mammary gland, as a working organ, in some cases inducing it to secretion and milk secretion, in others inhibiting these processes. Humoral factors also play an important role in milk secretion, which, acting on the chemoreceptors of the mammary gland, cause nervous excitement. It is transmitted along nerve pathways to the cerebral cortex, and from it nerve impulses go to the mammary gland, prompting it to secrete
All organs of the female’s body participate in the process of milk secretion and milk secretion, determining the specific individual properties of each cow’s milk. In addition to the ovary, pituitary gland and placenta, other endocrine glands (thyroid, adrenal glands, etc.) also affect lactation. External stimuli (visual, olfactory, auditory, tactile, gustatory) also have a positive or negative effect on the function of the mammary gland.
By the time of childbirth, the mammary gland enlarges and begins to produce colostrum-thick, viscous, yellowish-white liquid, which has a peculiar unpleasant, salty taste. Colostrum contains a significant amount of protein and salts, characteristic fat droplets (colostrum corpuscles). Colostrum contains less fat and sugar than regular milk. more iron, ten times more retinol (vitamin A) and ascorbic acid(vitamin C), three times more calciferol (vitamin D).
Colostrum contains a large number of disintegrated secretory cells. 7-10 days after birth, colostrum turns into regular milk, but it becomes suitable for cheese making only two weeks after birth.
The process of milk formation occurs in the alveoli. The process of secretion consists of the accumulation (formation) of cell secretions, the subsequent rejection of the accumulated secretion in the peripheral part of the cell and its passage into the lumen of the alveoli.
After birth, for 4-6 weeks (with proper milking or regular sucking), glandular tissue continues to develop and milk production increases. Then the reverse development of the mammary gland begins (involution), which consists of a gradual decrease in intensity and its function. After winter births with the transfer of cows to summer housing, an increase in their milk productivity is often observed, which is regarded by some experts as a natural manifestation of the two-vertex lactation line.
Milk yield- release of milk from the udder - occurs due to the movement of milk from upper sections udder downwards, mainly as a result of contraction of the myoepithelium and smooth muscles of the udder. Milk ejection is carried out by the combined activity of nervous and humoral systems. In the process of preparing the udder for milking, there is an increased flow of blood to the gland, ensuring the elasticity of the nipples. This condition is called udder erection. It provides a normal condition for milking or suckling. Milking, massage or sucking irritate the skin receptors of the udder, and in response to these irritations, impulses are received from the cerebral cortex, causing udder rigidity (tension of the contractile system of the udder), manifested in the contraction of myoepithelial cells of the alveoli, muscle layers medium and large milk passages, resulting in milk release. The nipple tanks are filled with milk. The entire udder becomes elastic, looks full and stretched.
Simultaneously with the formation of milk, it is absorbed components. This phenomenon is called reabsorption. When the udder is full, reabsorption increases. As milk is produced, the milk ducts expand due to relaxation of the muscles of the mammary gland. Typically, the udder is filled with milk within 12-14 hours. It is more or less uniform. Then, due to an increase in intraudder pressure, compression of the capillaries and irritation of the baroreceptors of milk production slows down, then stops, and the reabsorption process actively manifests itself. Timely release of the gland from secretion prevents this phenomenon.
Udder examination consists of collecting anamnesis, clinical examination of the animal, its mammary gland and checking the quality of milk.
When collecting anamnestic information, they strive to establish:
1) Time of last birth, duration of the dry period, stages of preparation for lactation, condition of the mammary gland before and after childbirth;
2) General condition of the body before and after childbirth, stage of the reproductive cycle, time of insemination, course of labor and the postpartum period;
3) The state of the region and farm in relation to livestock diseases in general and mammary gland disease in particular;
4) Diseases of the mammary gland noted in the animal in previous years;
5) Milk yield in previous years and in the last lactation period;
6) Method of milking and quality of milk, its color, smell, taste, change during boiling;
7) The time of illness of individual quarters of the udder, the quantity and quality of the secretion they secrete.
A clinical examination should begin with a routine examination of the animal, then examine the mammary gland by examining it, palpating it, test milking and determining the quality of the milk. The udder is examined from behind and from the side; at the same time pay attention to its shape, safety hairline, color of the skin; identify lesions, skin diseases or traces thereof.
By palpation, first of all, the temperature of individual areas of the mammary gland is determined in strict sequence by comparing the thermal sensation received by the back of the hand from symmetrically located points.
Treatment of animals with mastitis.
Restoring breast function is possible only with the normalization of complex neurovascular relationships and trophism.
Pathogenetic therapy of mastitis. To normalize neurovascular reactions, novocaine is used, which has an anesthetic factor that blocks the nerves of the mammary gland. Most effective method treatment is intraudermal injections of 100-150 ml of 0.5% novocaine solution with the addition of antibiotics at intervals of 12 hours (short novocaine blockade By). For injections, use a syringe connected by a rubber tube and a long injection needle (needle length 10-12 cm). The needle is inserted from behind between the base of the udder and the abdominal wall, retreating 1-2 cm from the midline towards the diseased half of the udder, and moving it towards the carpal joint of the same side to a depth of 8-12 cm. Inject 150-200 ml of 0.5% novocaine solution. By moving the needle in different directions, the solution is evenly distributed in the supra-uterine space.
Sheep are injected with a 0.25% solution of novocaine in a dose of 40-50 ml in the front, goats in the back of the udder. In sows, the nerves of each affected glandular lobe of the udder are blocked separately with a 0.25% solution of novocaine, 20-40 ml. If necessary, repeated blockades are carried out after 48-96 hours.
Positive results are obtained by introducing a 1% solution of novocaine into abdominal aorta by method. Good effect is obtained by administering 100-150 ml of a 1% solution of novocaine with an interval of 24-48 hours. Animals with serous mastitis recover in most cases after 2-3 days, with catarrhal - after 4-5, with fibrinous - after 6, with purulent catarrhal - after 5 and with hemorrhagic - after 6 days.
Often the course of the inflammatory process in the mammary gland is complicated by microorganisms that are the direct cause of mastitis. To select a more effective antibiotic, it is necessary to determine the type of pathogenic microflora and its sensitivity to the drug.
In the acute course of mastitis - serous, catarrhal, fibrinous or purulent - antibiotics (bicillin, penicillin, streptomycin, etc.) are administered intramuscularly at a dose of 3-5 thousand units per 1 kg of animal body weight.
Prevention of mastitis consists of a set of activities, which include:
Complete, balanced feeding and watering of animals;
Correct design and equipment of milking platforms;
Carefully selected milk devices for machine milking;
Complete release of the mammary gland during milking;
Maintain sanitary and hygienic conditions both when milking animals and in the premises where the animals are located;
Conduct monthly studies of dairy livestock for subclinical and clinical mastitis.
Milk represents white liquid contains small particles of fat, lactose, vitamins, and minerals. It is produced in the mammary glands of cows. The quality of milk depends on the animal’s nutrition, living conditions, age of the individual, and time of year. All the nutrients found in milk come from the blood. The anatomy of the cow's mammary gland contributes to the production of a healthy nutritious product that is necessary for both children and adults.
A cow's udder consists of 4 mammary glands. These are shares. They are interconnected, but each has a separate chamber. The lobes function independently of each other and end in the nipple. The anterior glands are smaller in volume than the hind glands, but in dairy cows all lobes are equal in volume.
The udder has a sheath of connective tissue covered with hairs. The fabric is gathered in elastic folds. They smooth out as the milk lobes fill with liquid. TO pelvic bones The udder is attached by connective tissue and ligaments. The basis of the mammary gland is glandular and adipose tissue:
The function of the udder is to produce milk and release it. The bowl capacity reaches 40 kg. When the ligaments are weakened, it sinks under weight or becomes deformed. Most often, changes are due to the age of the cow and the number of calvings.
Have no nipples sebaceous glands. During hot periods, cracks may appear on it. They cause pain to the cow when it comes into contact with grass or during milking. Nipples need care. After each milking they are lubricated with nourishing cream.
The shape of the udder varies among different breeds of cows. In dairy breeds, which are distinguished by good productive qualities, the gland has an elongated tubular shape. It is located along the abdominal cavity. Dairy-meat breeds most often have a cup-shaped udder. Its volume is large, indicating that the cow gives a lot of milk. In individuals of meat breeds, the glands are poorly developed: goat or primitive type of udder.
Speaking about the structure of the udder, it is necessary to describe the process of milk formation. The anatomy of the cow's mammary gland is such that milk production is associated with the reproductive organs. The alveoli begin to fill with fluid only under the influence of hormones, the level of which increases during pregnancy and after calving. Lactation is caused by prolactin, which is released by the anterior pituitary gland. The hormone stimulates the growth of the gland and prepares it for lactation. Lactocytes are present in the alveoli. These are the cells that produce milk from blood elements.
Fluid in the alveoli begins to be produced even before the calf is born. It is whitish in color, salty taste, viscous and thick. This is colostrum. After birth, a calf sucks out 1.5 kg of nutrient fluid in the first hours. He captures the nipple with his lips and thereby triggers the nerve impulse mechanism. The pituitary gland begins to secrete the hormone oxytocin. The hormone is captured by the receptors of the mammary gland, lactocytes begin to work and produce milk. The more often the nipple is irritated, the more milk is produced.
From the first days of lactation it is necessary to develop an udder. The cow is given a massage and all the milk is milked out, leaving the milk parts empty. After 4 hours they will fill with liquid again. It is recommended to milk cows every 6 hours. When the functioning of the mammary glands is normal, milking is carried out every 12 hours. If you exceed this period of time by 1-2 hours, the animal will have less milk. Over time, it will stop being produced.
The development of the mammary gland in cattle occurs before the 6th calving. After 9 calvings, milk production begins to decline. The cow is getting old. In dairy breeds, lactation can last until 13-16 calvings. Milk acquires its qualities and ceases to resemble colostrum 2 weeks after calving. The lactation period lasts 300 days. During this time, the animal can produce up to 16 thousand kg of milk.
Before you start milking a cow, you need to prepare both the room and the animal. The stall is cleaned and the manure is removed. The belly, legs, hooves and udder of the cow are washed. They approach the animal in such a way that she can see the milkmaid. An enamel bucket is used as a container for milk.
The cow loves affection, you need to stroke her and talk to her in a calm voice. To keep the animal calm, it is tied to a turnstile. The tail is lightly grabbed with a whip to the leg. In order for the pituitary gland to release oxytocin into the body and milk production to begin, it is necessary to massage the cow. This is a kind of imitation of the actions of a calf when feeding, which taps the udder of the nurse with its head. Perform diagonal and horizontal stroking, circular movements with hands along massage lines. At this time, fluid from the alveoli enters the canals, the cistern and the nipple canal. As soon as the nipple has become hard and increased in size, the milking process begins.
The nipple is lightly grabbed into the fist: large and index fingers located at the base of the nipple, at the same level. The little finger is located at the exit of the nipple canaliculus. The remaining fingers hold the body of the nipple strictly vertical. Squeeze the base of the nipple and squeeze the milk out of the tubule with your fingers.
The first drops are poured into a clean mug. The color of the milk is determined: whether there are any foreign impurities. With the first portion, bacteria and dirt come out of the teat if the cow is not washed well. The rest of the milk is milked into a container. After making the first cycle of movements with your fingers, wait until the nipple is full again. This usually takes 2-3 seconds. In a similar way, all 4 lobes of the udder are freed from milk.
When milking by machine, the apparatus is mounted on a turnstile, and milking cups are attached to the teats. The device creates a vacuum: the milk comes out of the tubules into the container. The cow also needs to be prepared for the process.
The operator must monitor the pressure in the equipment. Standard operating pressure 47 kPa. With low pressure, the milking process takes a long time. It's not effective. With increased pressure, the glasses will compress the cow's teat too much, causing her pain. No air should get into the glass. It will block the milk supply.
One of frequent illnesses udder - mastitis. It can develop with improper care for the animal, in case of gland injuries, in case of non-compliance with milking rules. This is a streptococcal infection. Pathogens enter through the outlet in the nipple, through cracks and wounds. Symptoms vary depending on the type of mastitis. Sometimes it is asymptomatic. The disease can only be recognized after milk testing.
To prevent the development of the disease, colostrum is taken for analysis in the first days after calving. Research is carried out in laboratory or at home conditions. For home testing, a rapid test is used. A 5% solution of dimastin is added to milk: it is purchased in pharmacies. If the color of the milk has not changed, then there are no streptococci in it. Even with slight changes in the shade of milk, additional tests are carried out in laboratories.
Cow mammary gland anatomy
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The milk productivity of a cow depends on many various factors, such as breed, age and health of the animal, lactation period, etc. Not less important has the shape and size of the mammary glands of a cow, the presence of visible milk ducts on them. By appearance mammary gland, an experienced specialist in animal husbandry can determine whether a cow has a high milk yield or belongs to the meat category with low milk productivity.
Location and structure of the udder
A cow's mammary glands are called the udder. The udder is divided into four mammary glands, forming the right and left parts. The parts are divided among themselves by a central partition. In turn, each half is formed by two lobes in which ducts for removing milk are located. The lobes end in nipples and they do not communicate with each other in any way. This structural feature must be taken into account when milking cows. An important point is to release all parts of the udder from milk, since it will not be able to get from one to another.
The udder is located in the pelvic region of the cow and is firmly attached to connective tissue and a whole set of suspensory ligaments. The supporting partition separating the right and left parts of the udder becomes less strong as the cow ages and the udder tends to sag.
Tissues that form a cow's udder
Three types of tissues are involved in the structure of the udder. These are glandular, adipose and connective tissue.
Glandular tissue is formed by many tiny follicles called alveoli. Their inner part covered with cells that produce milk. Flowing from the alveoli, milk passes through thin ducts that connect into canals. From the milk canals it enters the large milk passages, and then into the ducts communicating with the milk tanks. The tanks themselves end in a nipple with a channel located in the middle for removing milk. To prevent the uncontrolled flow of milk, this channel has a ring of muscles at the end, called the sphincter. During milking, the sphincter releases the contraction and allows milk to be extracted.
Adipose and connective tissues perform protective functions for the alveoli. Connective tissue makes up a kind of support apparatus, it is located directly around the glandular tissue, protecting it from adverse external influence. It is literally penetrated by many lymphatic and blood vessels, nerve endings that transmit to the central nervous system various irritations. It is the connective tissue that divides the udder into separate parts.
1 - nipple; 2 - milk ducts; 3 - nerves; 4 - sphincter; 5 - milk tank;
6 - connective tissue; 7 - alveoli; 8 - vein; 9 - artery.
Rice. Structure of a cow's udder
On the outside, the entire surface of the udder is covered with elastic skin with short soft hairs. In mature cows with high milk yields, this skin is thin and smooth.
Milk formation process
To run this complex process Just like milk production in a cow’s body, in addition to the functioning of the mammary gland itself, the functioning of other systems and organs is also necessary. Thus, nutrients delivered to the cow’s udder through the pudendal artery and vein take an active part in milk production. Blood circulation through blood vessels and capillaries occurs both from the base of the udder to the nipples, and from one part of the udder to the other. The movement of fluid through the udder is facilitated by the lymphatic system. At the base of the udder on each side there are lymph glands, to which it supplies liquid.
The hormone prolactin, which is released into the blood and causes increased milk production, is important for the amount of milk. Warm touching of the teats or the calf sucking on them irritates the nerve endings located at the tips of the udder. This also releases a hormone that promotes milk production.
It is worth noting that milk-producing cells in the alveoli also synthesize proteins and fats from nutrients that come with the blood.
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Structure of a cow's udder
A cow's udder is a mammary gland. It consists of four lobes - quarters: two anterior and two posterior. The lobes of the udder do not communicate with each other, and therefore milk from one lobe cannot flow into the others. Each lobe of the udder has its own teat.
The left and right halves of the udder are separated by an elastic septum, which not only separates the mammary gland, but also supports it. In older cows it weakens, and therefore the udder becomes droopier with age.
The udder consists of glandular, adipose and connective tissue, each of which performs its own functions. The formation of milk occurs in glandular tissue, which consists of a large number of tiny bubbles - alveoli. Inner surface The alveoli are lined with cells in which milk is formed. The milk accumulated in the alveoli enters the smallest milk ducts, which connect into milk canals, which enlarge as they merge and form the milk ducts. Through even wider milk ducts, milk flows into four milk tanks. Each cistern ends in the mammillary section of the cistern. In the nipple there is an outlet channel, which at the end has a circular muscle - a sphincter, which prevents the spontaneous removal of milk out. During milking, the sphincter relaxes, allowing milk to be extracted from the udder.
By the time of milking, the tanks contain up to 25% of the milk accumulated in the udder, and the rest is in the ducts and alveoli. If a catheter, which is a hollow tube, is inserted into the udder nipple, the cisternal milk will spontaneously flow out. However, complete emptying of the udder can only be achieved through milking.
The connective tissue in the udder is located around the glandular tissue, performing a supporting function and protecting the udder from the adverse effects of the external environment.
The udder has many sensitive nerve endings that transmit signals of irritation to the central nervous system, for example, the start of milking, etc.
The outside of the udder is covered with elastic skin with sparse short hair. Therefore, it is easily damaged under adverse environmental influences, poor care, dampness and drafts in the room, and rapid movement of cows, which can cause mastitis. High-yielding cows have thinner and more elastic udder skin. By this sign one can judge the productive qualities of a cow.
Before milking, the udder falls and many folds form on it, especially on the back side. This is the so-called udder reserve, the severity of which can be used to judge the capacity of the mammary gland.
Young cows have a more developed capacitive udder system, which should be taken into account when organizing their milking. The growth and development of glandular tissue continues until the 6th -7th lactation, and then, as the body ages, the glandular tissue is gradually replaced by connective tissue, as a result of which productivity decreases.
The formation of milk is a complex physiological process in which not only the mammary gland participates, but also other organs and systems. To produce milk, nutrients supplied to the udder through the blood are used. In turn, nutrients enter the blood from digestive system. Therefore, for a highly productive cow it is very important good development digestive organs.
To produce 1 liter of milk, 400-500 liters of blood must pass through the udder. Therefore, the cow must have a circulatory system capable of constant hard work.
Regulates the formation of milk by the nervous and hormonal systems. From the glands internal secretion The pituitary gland plays a leading role, releasing hormones into the blood, in particular prolactin, which causes milk secretion.
Irritation of the nerve endings of the nipples during milking or sucking activates the pituitary gland, which helps to increase milk secretion.
Milk is secreted in the mammary gland. Epithelial cells lining the cavity of the alveoli synthesize the main components of milk: proteins, fats and milk sugar- lactose from nutrients supplied with the blood. During the synthesis process they undergo significant changes. Thus, the protein casein, except milk, is not found anywhere in nature.
Vitamins, mineral salts, hormones and enzymes enter the plasma from the animal’s blood in finished form. However, in this case, secretory cells perform not a passive, but an active role, working selectively. Therefore, the concentration of these substances in milk and blood is different. For example, in cow's milk, compared to blood plasma, there is 14 times more calcium, 9 times more potassium, 10 times less phosphorus, and 7 times less sodium.
Nevertheless, great importance for the formation of milk, it has the quantity and quality of “precursors”, that is, substances from which the components of milk are formed.
In lactating cows, milk is continuously produced in the udder. First, milk fills the cavities of the alveoli, the excretory ducts, then the larger ducts and, lastly, the milk tanks. As milk accumulates in the udder due to a decrease in smooth muscle tone, the contractile force of muscle fibers weakens. As a result, until a certain period, a significant increase in pressure in the udder does not occur and conditions for milk accumulation are maintained. Filling of all cavities of the udder occurs within 10 - 12 hours, then internal pressure begins to rise, the blood vessels are compressed, which leads to a gradual decrease in the secretory activity of the mammary gland. If a cow is not milked for 14 - 16 hours, the pressure in the udder will increase so much that milk secretion will completely stop. If after this the cow is not milked, then the reverse process begins - the absorption of milk components.
Therefore, to maintain a high intensity of milk production, regular removal of milk from the udder is necessary. Skipping milking or an excessively long interval between milkings inhibit milk production and lead to a decrease in milk yield.
To prevent the udder from overflowing with milk between milkings, it must be sufficiently capacious. Udder capacity can be increased by appropriately preparing heifers for calving.
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MAMMARY GLAND
Udder - uber - mammary gland of a cow. Located in the caudal part of the ventral surface of the abdomen (Fig. 138). The udder, except for the nipples, is covered with hairy skin. The skin of the nipples is free of hair, sebaceous and sweat glands. The epidermis covering the skin of the nipples is thickened.
The hair flows on the skin of the udder are directed from the abdominal wall to the lobes of the udder and caudally from them. On the skin of the udder located between the thighs, a supra-udperal area is distinguished - regio sup-ramammaria (milk mirror - planum lactiferum), limited by the lines of meeting of two streams of short hair: a stream of hair on the caudal surface of the udder, directed dorsally, and a stream of hair on the skin of the thigh area, directed ventromedially .
The skin of the udder is smooth before milking; after milking, it forms vertical folds.
Under the skin is the superficial fascia in the form of a whitish thin durable plate of dense connective tissue. It covers the udder and passes dorsally into the superficial fascia of the abdominal wall. Under the superficial fascia lies the connective tissue membrane of the udder lobes. It is connected to layers of connective tissue inside the udder lobes. The layers of connective tissue inside the udder lobes are called stroma - stroma glandula mamaria.
The udder is divided into right and left halves. Between them, along the median sagittal plane, is the suspensory ligament of the udder - ligamentum suspensorium uberis made of elastic connective tissue. It is a continuation of the yellow (abdominal) fascia of the abdomen and an essential part of the suspensory apparatus of the udder - the apparatus suspensorius mammarium, which attaches the udder to the wall of the abdomen. At the site of the ligament at the bottom of the udder, the middle groove of the udder is clearly marked - sulcus intermammarius. Each half of the udder consists of two main lobes: the anterior and posterior. There may be additional underdeveloped lobes, most often caudal.
In the udder there is a base - basis uberis, located on the wall of the abdomen; body - corpus uberis; nipples - papilla. Most cows have an udder with four teats. Cows of a number of breeds have udders with 6 teats, for example, 30-40% of Simmental breed cows have 6 teats, with four teats and, accordingly, these lobes well developed, and two teats and their lobes underdeveloped.
Rice. 138. Cow's udder
The nipple is divided into a base, a body and a tip.
It is customary to distinguish the udder of the following main forms (Fig. 139);
1) cup-shaped - the body of the udder is rounded, the height is significant, the teats are widely spaced, the udder lobes are well developed and differ slightly from each other in size;
2) bath-shaped - the lobes are well developed, the body is of considerable height, elongated, the anterior edge of the udder is close to the center umbilical region, the length of the udder is 15-20% greater than the diameter of the udder;
3) flat - differs from cup-shaped by its smaller body height;
4) goat - characterized by a cone-shaped body, nipples close in location, the height of the rear lobes significantly exceeds the height of the small anterior lobes;
Rice. 139. Udder shape
5) “primitive” - small in size with small nipples close together.
A good udder of high-milk cows, corresponding to mechanical milking, has a tub-shaped or cup-shaped shape with cylindrical teats. The dimensions of such an udder are significant, for example, the circumference is 120-130 cm, the height is 25-30, the length of the nipples is 5-7, their diameter is 2-3 cm.
The glandular parts of the udder that produce milk. In the cells between the layers of whitish connective tissue (stroma) there are yellowish lobules of glandular tissue (parenchyma) of the mammary gland - lobuli glandule mammariae. Their size is 0.7-0.8 mm3. Blood, lymphatic vessels, and nerve fibers pass and branch through the layers of connective tissue. The lobules contain alveoli with a diameter of 50-350 microns and ducts (tubes).
In the walls of the alveoli (Fig. 140) and inside the lobular ducts there are single-layer glandular epithelium, secreting milk, and myoepithelial cells, by the contraction of which the alveoli and ducts are compressed, and the milk passes into the excretory lobular ducts.
Rice. 140. Milk alveoli and ducts
The system that removes milk consists of: a) milk ducts - ductus lactiferi of various diameters and structures; b) milk sinus - sinus lactiferi (milk tank). The following types of milk ducts are designated by location and structure: intralobular; interlobular; milk ducts visible to the naked eye. Their walls contain smooth muscle fibers, milk ducts, formed from the fusion of the milk ducts. In the milk sinus there is a glandular part (above the nipple) - pars glandularis, into which large milk ducts (passages) with a diameter of 5-15 mm open and a nipple part - pars papillaris, located inside the nipple. The internal rice part of the cistern is lined with mucous membrane, forming longitudinal and oblique folds and papillae. At the border of the suprapapillary and mammillary parts of the cistern there is a circular fold of the mucous membrane - plica anularis. The volume of the milk tank is larger in cows with high milk yields and smaller in cows with low milk yields. The excretory system ends with the nipple duct (canal) - ductus (canalis) papillaris, 5-15 mm long. The nipple duct is located at the tip of the nipple, and there is an internal opening into which milk flows from the tank, and an external nipple opening - ostia papillaria. The internal opening is covered with folds of the mucous membrane. In the wall of the nipple tip there are smooth ring-shaped muscles that form the nipple sphincter around the nipple duct - n. sphincter papille.
- 57.00 KbSpecific features of the structure and function of the mammary gland in females of various animal species
BREAST PATHOLOGY
The mammary gland, like the genitals, must be considered as an organ in natural conditions functioning only during the suckling period; it evolves in connection with childbirth and involutions when the offspring can already exist without mother’s milk. IN natural conditions after that comes new pregnancy, and in production, lactation is combined with pregnancy based on economic feasibility. The mammary gland is an organ that produces an essential food product (colostrum) for the newborn and milk. Therefore after brief description Anatomy and physiology of the mammary gland, we outline the main provisions of the doctrine of the forms of agalactia (lack of milk) and hypogalactia (lack of milk).
BRIEF MORPHOFUNCTIONAL CHARACTERISTICS OF THE UDDER
The mammary gland, udder, is a glandular organ consisting of four quarters; each of them ends at the bottom with a nipple. Some cows have two, less often four additional quarters, usually poorly developed, lacking glandular tissue and a teat canal. The skin of the udder is covered with delicate sparse hair; on the back surface of the udder they grow from bottom to top and to the sides, forming the so-called milk mirror. The shape and size of the milk mirror varies. The udder fits tightly to the ventral abdominal wall and is held in position by the suspensory ligament of the udder and fascia.
Components of the udder: glandular tissue, excretory ducts, interstitial connective tissue, blood vessels, lymphatic vessels and nerves. The right and left halves of the mammary gland are separated from one another by the suspensory ligament of the udder, which serves as a continuation of the yellow abdominal fascia. Under the skin is the superficial fascia of the mammary gland, covering each half of the udder. The superficial fascia is followed by its own fascia, covering the glandular part of the udder and giving branches (trabeculae) into the parenchyma, dividing it into quarters and individual small lobules; each lobule is surrounded by an interlobular connective tissue membrane.
The parenchyma of the udder consists of glandular alveoli and excretory ducts, forming an independent, separate system in each quarter of the udder. The alveoli are lined with secretory cells that produce milk. Each alveolus and the duct extending from it are externally entwined with stellate cells (myoepithelium) and their processes. When stellate cells contract, they squeeze the contents of the alveoli into the ducts. Small ducts depart from the alveoli, which unite to form the middle ducts. The areas of parenchyma with these ducts form independent lobules of the udder, surrounded by a more or less pronounced layer of interlobular connective tissue.
The middle ducts, heading down towards the nipple, merge and give rise to 12-50 wide excretory ducts - milk passages flowing into the cistern. Milk tank - the cavity of the nipple, sometimes extending upward into the parenchyma of the udder, serves as a reservoir for milk.
The nipples are conical, bluntly ending branches of the mammary gland. The nipple has a base that passes without sharp boundaries into the body of the udder lobe, an apex that freely hangs down, and a cylindrical part located between the apex and the base of the nipple. The length of the nipples, depending on the age, breed and milk production of the cow, varies from 4 to 10 cm. The wall of the nipple is made of skin, connective tissue and mucous membranes. The skin does not contain hair, sebaceous or sweat glands, at the apex it passes into the mucous membrane of the nipple canal, connecting the cavity of the cistern with the external environment. The connective tissue layer of the nipple wall has bundles of smooth muscle fibers that form plexuses running in different directions. At the apex of the nipple, the muscle fibers are collected into a clearly defined circular layer - the sphincter of the nipple canal. Its length is 5-10 mm, diameter 2.5-3 mm. The lumen of the nipple canal is closed by a contracted sphincter and small longitudinal folds of the canal shell tightly adjacent to each other, forming a rosette on the side of the cistern, which is important for tightness. 0.8 - 1 liter of blood, and during lactation - 4 liters or more.
Arterial system of the cow's udder. You should pay attention to the following features of the blood supply to the udder: perineal arteries branch on its posterior surface; there are anastomoses between the arteries of the right and left halves of the udder; The perineal vein carries blood from the genitals to the udder. The latter fact is of great importance for explaining cases of udder disease with damage to the genital organs, as well as the endocrine influence of sex hormones on the udder.
The udder is very rich in blood vessels; arterial and venous capillaries form a dense network around each alveoli. The intensity of blood supply to the udder depends on its functional state.
The venous system of the udder is more developed than the arterial system. There are a large number of additional venous vessels, often anastomosing with each other and with the veins of the adjacent quarter. There are also anastomoses between the veins of the right and left halves of the udder.
Venous blood flows from the udder through three paired vessels:
1) along the external pudendal vein, running together with the external pudendal artery;
2) along the subcutaneous abdominal mammary vein, which, heading forward, stands out well under the skin with its convolutions and penetrates through the mammary well into abdominal cavity, where it flows into the internal ore vein;
3) along the internal pudendal vein.
Venous trunks, mainly superficial, form a large number of convolutions and ampulla-shaped extensions, mainly at the base of the nipple, which gives the udder tuberosity. The circular venous plexus, located at the border of the cistern and parenchyma, can close the lumen of the cistern when overfilled with blood.
The lymphatic system of the udder originates from the lymphatic slits and spaces located around the alveoli. From here, the lymph collects in the interlobular lymphatic vessels, passes through the lymph nodes into the lymphatic cistern, and from there along the thoracic duct into the vena cava. Rich Network lymphatic vessels The skin of the udder begins in small stems at the base of the nipple. They form a large number of anastomoses between themselves and the deep lymphatic vessels of the corresponding quarter, uniting in each lobe into independent trunks, separately flowing into the suprauterine lymph nodes the size of a hazelnut or a pigeon egg. The suprauterine lymph nodes are located at the base of the posterior lobes of the udder. From each node, lymph is carried out by two large lymphatic vessels or bundles of vessels. One of the efferent vessels goes to the perineum and unites here with the lymphatic system of the rectum and external genitalia; another vessel goes into groin area, to the inguinal lymph nodes. In addition to the main lymphatic vessels, there are a number of small ones that densely penetrate the parenchyma of the gland.
The degree of lymph circulation in the mammary gland in lactating animals is directly dependent on the level of milk production. In dry cows it is approximately 6 times less than in milk cows (I.K. Medvedev).
The innervation of the udder is carried out by branches and, finally, branches from the dense nerve plexuses surrounding the vessels of the udder. The nerve fibers of the parenchyma form dense plexuses around the alveoli and lobules of the gland. Clearly distinguishable nerve trunks go, accompanying the vessels of the cistern and milk ducts, to the milk cistern and nipple, where they end in the skin of the nipple and in the mucous membrane of the cistern. Irritation of receptors located in the thickness of the udder tissue affects blood circulation, respiration, digestion and reproductive system animal.
The pituitary gland reacts by increasing or decreasing the release of hormones under the influence of visual, auditory and olfactory perceptions.
The mammary gland of sheep and goats consists of two
halves, clearly demarcated by the inter-udder furrow. In structure and function, the mammary gland of these animals does not differ significantly from that of a cow. It should be noted only the conical shape of the nipples and the strong sagging gland in the goat, which causes frequent mechanical damage to the udder. The innervation of the udder is carried out by branches of the lumbolateral nerves, arising from the first and second lumbar nerves, passing along the abdominal wall of the corresponding side and branching in the skin and parenchyma of the udder. In sheep, the nipples are short, the udder lobes are rounded, the teat canals are somewhat longer (up to 1 cm) and narrower (this is important to consider during catheterization).
The camel's mammary gland has four lobes; like a cow, it is divided into right and left halves. The nipples are short (reminiscent of the nipples of a “kumys” mare). The forequarters are less developed than the hind quarters. Milk productivity depends on the breed of the animal and ranges from 15-20 liters per day. The duration of the lactation period reaches 16-18 months.
The mare's mammary gland is covered with delicate hairless skin. During the dry period, the gland decreases so much that it almost merges with the skin of the abdomen, and reduced, tightened nipples protrude on its folds in the form of laterally flattened elevations. The gland is inactive and well demarcated from the abdominal wall, to which it is suspended on a branch of the yellow abdominal fascia - the suspensory ligament, which penetrates between the halves of the udder and passes into the fascia of the mammary gland. Each half of the udder is divided into front and rear quarters, indistinguishable from the outside, having independent and separate systems of alveoli and excretory ducts, opening at the base of the nipple into two or three small cone-shaped tanks. The cisterns communicate with the external environment through independent channels, and on each nipple there are therefore two (rarely three) openings of the nipple canals, corresponding to the anterior and posterior glands. The blood supply to the gland is carried out through arteries and veins. The mammary gland of a pig consists of 8-16 (rarely 20) glandular lobes (mammary hills), symmetrically located on the sides of the white line from the pubic bones to the sternum; Sometimes the number of shares is odd. Each lobe is composed of a group of glands, the ducts of which flow into two, rarely three, small cisterns. At the top of the nipple, two, rarely three, nipple canals open. During the dry period, the lobes of the gland are pulled towards the abdominal wall and merge with it. By the time of birth, the mammary gland is secreted in the form of two powerful bars with more or less evenly developed lobes.
The dog's mammary gland consists of 10 glandular lobes located on the ventral abdominal wall. There are no milk tanks. As their lumen increases, the milk ducts unite into 6-12 large milk ducts, which open as independent ducts at the apex of the nipple; therefore, when the secretion is squeezed out of the gland, milk first appears on the surface of the nipple in the form of several small droplets, gradually merging into a common large drop. Each nipple serves its own system of alveoli and excretory ducts of the mammary gland.
During lactation, areas of the milk ducts located in the nipple can expand and take the form of small cisterns (milk sinuses).
The cat's mammary gland consists of 8 glandular lobes, located, like in a dog, on the ventral abdominal wall. The milk ducts, merging and not forming a cistern, open on the surface of the nipple with two holes.
The mammary gland of a rabbit is formed by 8 glandular lobes.
Function of the mammary gland. The mammary gland performs the function of lactation, which consists of two independent and interdependent processes: milk formation and milk output. Lactation is a manifestation of a complex non-humoral reaction of the whole organism to nerve impulses coming from receptors in the skin of the mammary gland during sucking or milking, as well as arising as a result of irritation of chemo-receptors located in the walls of the blood vessels of the gland and other organs by substances formed in the body females during certain periods of life (childbirth, pregnancy). Hormones involved in the lactation process include estrogens, progesterone, prolactin, somatotropic, thyroid-tropic, adrenocorticotropic, oxytocin, thyroxine, triiodothyronine, thyrocalcitonin, glucocorticoids, mineralocorticoids, adrenaline, norepinephrine, parathyroid hormone , insulin and glucocorticoid.
The function of the udder is closely related to functional state genital organs. In a castrated immature female, the mammary gland does not develop due to the lack of estrogens. After transplanting an ovary into a castrated male, his mammary gland develops and even lactates. Subcutaneous administration of estrogens to infantile animals causes the growth of the milk ducts, and when the action of estrogens is combined with progesterone, the alveoli also grow. In the second half of pregnancy, the ovary and placenta secrete a large amount of estrogens, which cause the growth of the milk ducts and alveoli. Progesterone prepares the gland for secretion. Towards the end of pregnancy, the anterior lobe of the pituitary gland secretes the hormone prolactin, as a result of which milk is formed, i.e., secretion occurs, and the posterior lobe of the pituitary gland produces oxytocin, which causes milk secretion.
Milk formation (milk secretion) is inextricably linked with milk secretion. Without milk release (when colostrum and milk are not milked or not sucked due to the death of the offspring), as well as when milk is continuously released (for example, when a milk catheter is constantly inserted into the nipple canal or with penetrating wounds of the nipple), the formation of milk stops. Important factor lactation - irritation of nerve endings located in the walls of blood vessels, milk ducts and in the skin of the mammary gland. Irritation of the nerve endings of the skin of the mammary gland and especially the nipple (massage, milking, sucking) is transmitted along the nerve pathways to the cerebral cortex. In response to these irritations, nerve impulses go from the center to the periphery to the mammary gland as a working organ, in some cases inducing it to secretion and milk secretion, in others inhibiting these processes. Humoral factors also play an important role in milk secretion, which, acting on the chemoreceptors of the mammary gland, cause nervous excitement. It is transmitted along nerve pathways to the cerebral cortex, and from it nerve impulses go to the mammary gland, prompting it to secrete.
Description
The mammary gland, like the genitals, must be considered as an organ that, under natural conditions, functions only during the suckling period; it evolves in connection with childbirth and involutions when the offspring can already exist without mother’s milk. Under natural conditions, this is followed by a new pregnancy, and in production, lactation is combined with pregnancy based on economic feasibility. The mammary gland is an organ that produces an essential food product (colostrum) for the newborn and milk. Therefore, after a brief description of the anatomy and physiology of the mammary gland, we outline the main provisions of the doctrine of the forms of agalactia (lack of milk) and hypogalactia (low milk production).
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