The epididymis (pronounced /ɛpɨˈdɪdɨmɪs/, plural: epididymides /ɛpɨˌdɪdɨˈmiːdiːz/) is part of the male Male refers to the sex of an organism, or part of an organism, which produces small mobile gametes, called spermatozoa. Each spermatozoon can fuse with a larger female gamete or ovum, in the process of fertilization. A male cannot reproduce sexually without access to at least one ovum from a female, but some organisms can reproduce both sexually reproductive system The reproductive system or genital system is a system of organs within an organism which work together for the purpose of reproduction. Many non-living substances such as fluids, hormones, and pheromones are also important accessories to the reproductive system. Unlike most organ systems, the sexes of differentiated species often have significant and is present in all male amniotes The amniotes are a group of tetrapod vertebrates that have a terrestrially adapted egg. They currently include mammals (synapsids), and sauropsids (reptiles and birds), as well as their fossil ancestors. Amniote embryos, whether laid as eggs or carried by the female, are protected and aided by several extensive membranes. In eutherian mammals (. It is a narrow, tightly-coiled tube connecting the efferent ducts from the rear of each testicle to its vas deferens The vas deferens , also called ductus deferens, (Latin: "carrying-away vessel"), is part of the male anatomy of many vertebrates; they transport sperm from the epididymis in anticipation of ejaculation. A similar, but probably non-homologous In evolutionary biology, homology refers to any similarity between characteristics of organisms that is due to their shared ancestry. The word homologous derives from the ancient Greek ομολογειν, 'to agree'. There are examples in different branches of biology. Anatomical structures that perform the same function in different biological, structure is found in cartilaginous fishes Chondrichthyes or cartilaginous fishes are jawed fish with paired fins, paired nares, scales, two-chambered hearts, and skeletons made of cartilage rather than bone. They are divided into two subclasses: Elasmobranchii (sharks, rays and skates) and Holocephali (chimaera, sometimes called ghost sharks, which are sometimes separated into their own.
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Regions
The epididymis can be divided into three main regions
- The head (Caput). The head of the epididymis receives spermatozoa via the efferent ducts of the mediastinum The mediastinum is a non-delineated group of structures in the thorax, surrounded by loose connective tissue. It is the central compartment of the thoracic cavity. It contains the heart, the great vessels of the heart, esophagus, trachea, phrenic nerve, cardiac nerve, thoracic duct, thymus, and lymph nodes of the central chest of the testis The testicle is the male generative gland in animals. It is characterized histologically Histology is the study of the microscopic anatomy of cells and tissues of plants and animals. It is performed by examining a thin slice (section) of tissue under a light microscope or electron microscope. The ability to visualize or differentially identify microscopic structures is frequently enhanced through the use of histological stains by a thin myoepithelium. The concentration of the sperm here is dilute.
- The body (Corpus)
- The tail (Cauda). This has a thicker myoepithelium than the head region, as it is involved in absorbing fluid to make the sperm more concentrated.
In reptiles, there is an additional canal between the testis and the head of the epididymis, which receives the various efferent ducts. This is, however, absent in all birds and mammals.[1]
Histology
The epididymis is covered by a pseudostratified epithelium A pseudostratified epithelium is a type of epithelium that, though comprising only a single layer of cells, has its cell nuclei positioned in a manner suggestive of stratified epithelia. As it rarely occurs as squamous or cuboidal epithelia, it is usually considered synonymous with the term pseudostratified columnar epithelium composed of short basal cells and tall principal cells with non-motile stereocilia Though their name is more similar to cilia, they are actually more closely related to microvilli, and some sources consider them to be a variant of microvilli rather than their own distinct type of structure. It is a long projection of cell membrane, similar in structure to microvillus (long microvilli Microvilli are microscopic cellular membrane protrusions that increase the surface area of cells, and are involved in a wide variety of functions, including absorption, secretion, cellular adhesion, and mechanotransduction). The epithelium Epithelium is a tissue composed of cells that line the cavities and surfaces of structures throughout the body. Many glands are also formed from epithelial tissue. It lies on top of connective tissue, and the two layers are separated by a basement membrane is separated by a basement membrane The basement membrane is a thin sheet of fibers that underlies the epithelium, which lines the cavities and surfaces of organs, or the endothelium, which lines the interior surface of blood vessels from the connective tissue Connective tissue is a form of fibrous tissue.. It is one of the four types of tissue in traditional classifications wall which has smooth muscle Smooth muscle is an involuntary non-striated muscle. It is divided into two sub-groups; the single-unit and multiunit smooth muscle. Within single-unit smooth muscle tissues, the autonomic nervous system innervates a single cell within a sheet or bundle and the action potential is propagated by gap junctions to neighboring cells such that the cells.
Role in storage of sperm and ejaculant
Spermatozoa formed in the testis enter the caput epididymis, progress to the corpus, and finally reach the cauda region, where they are stored. Sperm entering the caput epididymis are incomplete - they lack the ability to swim forward (motility Motility is a biological term which refers to the ability to move spontaneously and actively,as per our psych class... consuming energy in the process. Most animals are motile but the term applies to single-celled and simple multicellular organisms, as well as to some mechanisms of fluid flow in multicellular organs, in addition to animal) and to fertilize Fertilisation , is the fusion of gametes to produce a new organism. In animals, the process involves the fusion of an ovum with a sperm, which eventually leads to the development of an embryo. Depending on the animal species, the process can occur within the body of the female in internal fertilisation, or outside in the case of external an egg. During their transit in the epididymis, sperm undergo maturation processes necessary for them to acquire these functions.[2] Final maturation is completed in the female Female is the sex of an organism, or a part of an organism, which produces non-mobile ova (egg cells) reproductive tract (capacitation).
During ejaculation, sperm flow from the lower portion of the epididymis (which functions as a storage reservoir). They have not been activated by products from the prostate gland, and they are unable to swim, but are transported via the peristaltic Peristalsis is a radially symmetrical contraction of muscles which propagates in a wave down the muscular tube. In humans, peristalsis is found in the contraction of smooth muscles to propel contents through the digestive tract. Earthworms use a similar mechanism to drive their locomotion. The word is derived from New Latin and comes from the action of muscle Muscle is the contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to produce force and cause motion. Muscles can cause layers within the vas deferens The vas deferens , also called ductus deferens, (Latin: "carrying-away vessel"), is part of the male anatomy of many vertebrates; they transport sperm from the epididymis in anticipation of ejaculation, and are mixed with the diluting fluids of the seminal vesicles The seminal vesicles or vesicular glands are a pair of simple tubular glands posteroinferior to the urinary bladder of male mammals and other accessory glands prior to ejaculation (forming semen).
The epididymis possesses numerous, long atypical microvilli Microvilli are microscopic cellular membrane protrusions that increase the surface area of cells, and are involved in a wide variety of functions, including absorption, secretion, cellular adhesion, and mechanotransduction. These processes are often called stereocillia; this is incorrect, as they neither contain the microtubular structures of cilia A cilium is an organelle found in eukaryotic cells. Cilia are slender protuberances that project from the much larger cell body nor function like cilia.[3]
Pathology
An inflammation of the epididymis is called epididymitis Epididymitis is a medical condition in which there is inflammation of the epididymis . This condition may be mildly to very painful, and the scrotum (sac containing the testicles) may become red, warm and swollen. It may be acute (of sudden onset) or rarely chronic.
Embryology and vestigial structures
A Gartner's duct Gartner's duct is a potential embryological remnant in human female development of the mesonephric ducts in the development of the urinary and reproductive organs is a homologous In evolutionary biology, homology refers to any similarity between characteristics of organisms that is due to their shared ancestry. The word homologous derives from the ancient Greek ομολογειν, 'to agree'. There are examples in different branches of biology. Anatomical structures that perform the same function in different biological remnant in the female.
In the embryo An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination. In humans, it is called an embryo until about eight weeks after fertilization (i.e. ten weeks LMP), and from then it is instead called a fetus, the epididymis develops from tissue that once formed the mesonephros, a primitive kidney The kidneys are paired organs with several functions. They are seen in many types of animals, including vertebrates and some invertebrates. They are an essential part of the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid-base balance, and regulation of blood pressure. They serve the found in many aquatic vertebrates. Persistence of the cranial end of the mesonephric duct will leave behind a remnant called the appendix of the epididymis. In addition, some mesonephric tubules can persist as the paradidymis, a small body caudal to the efferent ductules.
Epididymectomy
This is the surgical removal of the Epididymis carried out under local anaesthesia. This is most often performed to relieve pain associated post-Vasectomy.
Gallery
Notes
- ^ Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp. 394–395. ISBN The International Standard Book Number is a unique numeric commercial book identifier based upon the 9-digit Standard Book Numbering (SBN) code created by Gordon Foster, now Emeritus Professor of Statistics at Trinity College, Dublin, for the booksellers and stationers W.H. Smith and others in 1966 0-03-910284-X.
- ^ Jones R (1999). "To store or mature spermatozoa? The primary role of the epididymis". Int J Androl 22 (2): 57–67. doi A digital object identifier is a character string used to uniquely identify an electronic document or other object. Metadata about the object is stored in association with the DOI name and this metadata may include a location, such as a URL, where the object can be found. The DOI for a document is permanent, whereas its location and other metadata:10.1046/j.1365-2605.1999.00151.x. PMID A PMID is a unique number assigned to each PubMed citation of life sciences and biomedical scientific journal articles. The related Pubmed Central archive may additionally assign a separate number, a PMCID (PubMed Central Identifier), normally written with a PMC prefix 10194636. abstract
- ^ Stevens, Alan; Lowe, James N. (2005). Human histology. Philadelphia: Elsevier Mosby. ISBN The International Standard Book Number is a unique numeric commercial book identifier based upon the 9-digit Standard Book Numbering (SBN) code created by Gordon Foster, now Emeritus Professor of Statistics at Trinity College, Dublin, for the booksellers and stationers W.H. Smith and others in 1966 978-0-323-03663-4.
External links
- Histology at BU Boston University is a private research university located in Boston, Massachusetts. The university is affiliated with the United Methodist Church, but describes itself as nonsectarian. With more than 4,000 faculty members and more than 31,000 students, Boston University is one of the largest private universities in the United States and one of 16903loa
- inguinalregion at The Anatomy Lesson by Wesley Norman (Georgetown University Georgetown University is a Jesuit private university located in Georgetown, Washington, DC. Father John Carroll founded the school in 1789, though its roots extend back to 1634. While the school struggled financially in its early years, Georgetown expanded into a branched university after the American Civil War under the leadership of university) (testes)
Categories: Male reproductive system
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