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Glands
In animals, a gland is a group of cells in an animal's body that synthesizes substances (such as hormones) for release into the bloodstream (endocrine gland) or into cavities inside the body or its outer surface (exocrine gland). Structure Development Every gland is formed by an ingrowth from an epithelial surface. This ingrowth may in the beginning possess a tubular structure, but in other instances glands may start as a solid column of cells which subsequently becomes tubulated. As growth proceeds, the column of cells may split or give off offshoots, in which case a compound gland is formed. In many glands, the number of branches is limited, in others (salivary, pancreas) a very large structure is finally formed by repeated growth and sub-division. As a rule, the branches do not unite with one another, but in one instance, the liver, this does occur when a reticulated compound gland is produced. In compound glands the more typical or secretory epithelium is found forming t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sweat Gland
Sweat glands, also known as sudoriferous or sudoriparous glands, , are small tubular structures of the skin that produce sweat. Sweat glands are a type of exocrine gland, which are glands that produce and secrete substances onto an epithelial surface by way of a duct. There are two main types of sweat glands that differ in their structure, function, secretory product, mechanism of excretion, anatomic distribution, and distribution across species: * Eccrine sweat glands are distributed almost all over the human body, in varying densities, with the highest density in palms and soles, then on the head, but much less on the trunk and the extremities. Its water-based secretion represents a primary form of cooling in humans. * Apocrine sweat glands are mostly limited to the axillae (armpits) and perineal area in humans. They are not significant for cooling in humans, but are the sole effective sweat glands in hoofed animals, such as the camels, donkeys, horses, and cattle. Ce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sebaceous Gland
A sebaceous gland is a microscopic exocrine gland in the skin that opens into a hair follicle to secrete an oily or waxy matter, called sebum, which lubricates the hair and skin of mammals. In humans, sebaceous glands occur in the greatest number on the face and scalp, but also on all parts of the skin except the palms of the hands and soles of the feet. In the eyelids, meibomian glands, also called tarsal glands, are a type of sebaceous gland that secrete a special type of sebum into tears. Surrounding the female nipple, areolar glands are specialized sebaceous glands for lubricating the nipple. Fordyce spots are benign, visible, sebaceous glands found usually on the lips, gums and inner cheeks, and genitals. Structure Location Sebaceous glands are found throughout all areas of the skin, except the palms of the hands and soles of the feet. There are two types of sebaceous glands, those connected to hair follicles and those that exist independently. Sebaceous gland ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adrenal Gland
The adrenal glands (also known as suprarenal glands) are endocrine glands that produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol. They are found above the kidneys. Each gland has an outer cortex which produces steroid hormones and an inner medulla. The adrenal cortex itself is divided into three main zones: the zona glomerulosa, the zona fasciculata and the zona reticularis. The adrenal cortex produces three main types of steroid hormones: mineralocorticoids, glucocorticoids, and androgens. Mineralocorticoids (such as aldosterone) produced in the zona glomerulosa help in the regulation of blood pressure and electrolyte balance. The glucocorticoids cortisol and cortisone are synthesized in the zona fasciculata; their functions include the regulation of metabolism and immune system suppression. The innermost layer of the cortex, the zona reticularis, produces androgens that are converted to fully functional sex hormones i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holocrine
Holocrine (from Ancient Greek ὅλος; ''hólos'', “whole, entire” + κρῑ́νω; ''krī́nō'', “to separate”) is a term used to classify the mode of secretion in exocrine glands in the study of histology. Holocrine secretions are produced in the cytoplasm of the cell and released by the rupture of the plasma membrane, which destroys the cell and results in the secretion of the product into the lumen. Holocrine gland secretion is the most damaging (to the cell itself and not to the host which begot the cell) type of secretion, with merocrine secretion being the least damaging and apocrine secretion falling in between. Examples of holocrine glands include the sebaceous glands of the skin and the meibomian glands of the eyelid An eyelid is a thin fold of skin that covers and protects an eye. The levator palpebrae superioris muscle retracts the eyelid, exposing the cornea to the outside, giving vision. This can be either voluntarily or involuntarily. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tubular Gland
Tubular glands are glands with a tube-like shape throughout their length, in contrast with alveolar glands, which have a saclike secretory portion. Tubular glands are further classified as one of the following types: Additional images See also * skin - glands in skin structure * hair follicles - for hair growth References Additional images File:Gray940.png, A diagrammatic sectional view of the skin (magnified). File:Gray1169.png, Vertical section of mucous membrane of human uterus The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the organ in the reproductive system of most female mammals, including humans that accommodates the embryonic and fetal development of one or more embryos until birth. The .... File:Skin.png, Skin Glands {{anatomy-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Submandibular Gland
The paired submandibular glands (historically known as submaxillary glands) are major salivary glands located beneath the floor of the mouth. They each weigh about 15 grams and contribute some 60–67% of unstimulated saliva secretion; on stimulation their contribution decreases in proportion as the parotid secretion rises to 50%. The average length of the normal human submandibular salivary gland is approximately 27mm, while the average width is approximately 14.3mm. Structure Lying superior to the digastric muscles, each submandibular gland is divided into superficial and deep lobes, which are separated by the mylohyoid muscle: * The superficial lobe comprises most of the gland, with the mylohyoid muscle runs under it * The deep lobe is the smaller part Secretions are delivered into the submandibular duct on the deep portion after which they hook around the posterior edge of the mylohyoid muscle and proceed on the superior surface laterally. The excretory ducts are then cros ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endocrine System
The endocrine system is a messenger system comprising feedback loops of the hormones released by internal glands of an organism directly into the circulatory system, regulating distant target organs. In vertebrates, the hypothalamus is the neural control center for all endocrine systems. In humans, the major endocrine glands are the thyroid gland and the adrenal glands. The study of the endocrine system and its disorders is known as endocrinology. Glands that signal each other in sequence are often referred to as an axis, such as the hypothalamic-pituitary-adrenal axis. In addition to the specialized endocrine organs mentioned above, many other organs that are part of other body systems have secondary endocrine functions, including bone, kidneys, liver, heart and gonads. For example, the kidney secretes the endocrine hormone erythropoietin. Hormones can be amino acid complexes, steroids, eicosanoids, leukotrienes, or prostaglandins. The endocrine system can be contrasted to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apocrine
Apocrine () glands are a type of exocrine gland, which are themselves a type of gland, i.e. a group of cells specialized for the release of secretions. Exocrine glands secrete by one of three means: holocrine, merocrine and apocrine. In apocrine secretion, secretory cells accumulate material at their apical ends, and this material then buds off from the cells, forming extracellular vesicles. The secretory cells therefore lose part of their cytoplasm in the process of secretion. An example of true apocrine glands is the mammary glands, responsible for secreting breast milk. Apocrine glands are also found in the anogenital region and axillae. Apocrine secretion is less damaging to the gland than holocrine secretion (which destroys a cell) but more damaging than merocrine secretion (exocytosis). Apocrine metaplasia Apocrine metaplasia is a reversible transformation of cells to an apocrine phenotype. It is common in the breast in the context of fibrocystic change. It is seen in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epithelium
Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellular matrix. Epithelial tissues line the outer surfaces of organs and blood vessels throughout the body, as well as the inner surfaces of cavities in many internal organs. An example is the epidermis, the outermost layer of the skin. There are three principal shapes of epithelial cell: squamous (scaly), columnar, and cuboidal. These can be arranged in a singular layer of cells as simple epithelium, either squamous, columnar, or cuboidal, or in layers of two or more cells deep as stratified (layered), or ''compound'', either squamous, columnar or cuboidal. In some tissues, a layer of columnar cells may appear to be stratified due to the placement of the nuclei. This sort of tissue is called pseudostratified. All glands are made up of epi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Duct (anatomy)
In anatomy and physiology, a duct is a circumscribed channel leading from an exocrine gland or organ. Types of ducts Examples include: Duct system As ducts travel from the acinus which generates the fluid to the target, the ducts become larger and the epithelium becomes thicker. The parts of the system are classified as follows: Some sources consider "lobar" ducts to be the same as "interlobar ducts", while others consider lobar ducts to be larger and more distal from the acinus. For sources that make the distinction, the interlobar ducts are more likely to classified with simple columnar epithelium (or pseudostratified epithelium), reserving the stratified columnar for the lobar ducts. File:Gray1025.png, Section of submaxillary gland of kitten. Duct semidiagrammatic. X 200. File:Gray1173.png, Section of portion of mamma. Intercalated duct The intercalated duct, also called intercalary duct (ducts of Boll), is the portion of an exocrine gland leading directly f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alveolar Gland
Alveolar glands, also called saccular glands are glands with a saclike secretory portion, in conrast with tubular glands. They typically have an enlarged lumen (cavity), hence the name: they have a shape similar to alveoli, the very small air sacs in the lungs. Some sources draw a clear distinction between acinar and alveolar glands, based upon the size of the lumen. A further complication in the case of the alveolar glands may occur in the form of still smaller saccular diverticuli growing out from the main sacculi. The term "racemose gland" is used to describe a "compound alveolar gland" or "compound acinar gland." Branched alveolar glands are classified as follows: Additional images File:Gray897.png, Alveoli of lacrimal gland. File:Gray1026.png, Human submaxillary gland. At the right is a group of mucous alveoli, at the left a group of serous alveoli. File:Gray1173.png, Section of portion of mamma. See also * Acinus An acinus (; plural, acini; adjective, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endocrine Vs
The endocrine system is a messenger system comprising feedback loops of the hormones released by internal glands of an organism directly into the circulatory system, regulating distant target organs. In vertebrates, the hypothalamus is the neural control center for all endocrine systems. In humans, the major endocrine glands are the thyroid gland and the adrenal glands. The study of the endocrine system and its disorders is known as endocrinology. Glands that signal each other in sequence are often referred to as an axis, such as the hypothalamic-pituitary-adrenal axis. In addition to the specialized endocrine organs mentioned above, many other organs that are part of other body systems have secondary endocrine functions, including bone, kidneys, liver, heart and gonads. For example, the kidney secretes the endocrine hormone erythropoietin. Hormones can be amino acid complexes, steroids, eicosanoids, leukotrienes, or prostaglandins. The endocrine system can be contrasted to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
