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Mesonephric Tubules
Mesonephric tubules are genital ridges that are next to the mesonephros. In males, some of the mesonephric kidney tubules, instead of being used to filter blood like the rest, "grow" over to the developing testes, penetrate them, and become connected to the seminiferous tubules of the testes. They also form the epididymis and the paradidymis. The spermatozoon, sperm differentiate inside the seminiferous tubules, then swim down these tubes, then through these special mesonephric tubules, and go down inside Wolffian duct, to the coelom and finally to the organ the animal uses to transport sperm into females. In females, it gives rise to the epoophoron and the paroöphoron. References External links * * http://www.uoguelph.ca/zoology/devobio/210labs/kidney2.html Embryology of urogenital system {{Developmental-biology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mesonephros
The mesonephros ( el, middle kidney) is one of three excretory system, excretory organs that develop in vertebrates. It serves as the main excretory organ of aquatic vertebrates and as a temporary kidney in reptiles, birds, and mammals. The mesonephros is included in the Wolffian body after Caspar Friedrich Wolff who described it in 1759. (The Wolffian body is composed of: mesonephros + paramesonephrotic blastema) Structure The mesonephros acts as a structure similar to the human kidney, kidney that, in humans, functions between the sixth and tenth weeks of embryological life. Despite the similarity in structure, function, and terminology, however, the mesonephric nephrons do not form any part of the mature kidney or nephrons. In humans, the mesonephros consists of units which are similar in structure and function to nephrons of the adult kidney. Each of these consists of a glomerulus, a tuft of capillary, capillaries which arises from lateral branches of dorsal aorta and drains i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Testes
A testicle or testis (plural testes) is the male reproductive gland or gonad in all bilaterians, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testosterone. Testosterone release is controlled by the anterior pituitary luteinizing hormone, whereas sperm production is controlled both by the anterior pituitary follicle-stimulating hormone and gonadal testosterone. Structure Appearance Males have two testicles of similar size contained within the scrotum, which is an extension of the abdominal wall. Scrotal asymmetry, in which one testicle extends farther down into the scrotum than the other, is common. This is because of the differences in the vasculature's anatomy. For 85% of men, the right testis hangs lower than the left one. Measurement and volume The volume of the testicle can be estimated by palpating it and comparing it to ellipsoids of known sizes. Another method is to use cali ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seminiferous Tubules
Seminiferous tubules are located within the testes, and are the specific location of meiosis, and the subsequent creation of male gametes, namely spermatozoa. Structure The epithelium of the tubule consists of a type of sustentacular cells known as Sertoli cells, which are tall, columnar type cells that line the tubule. In between the Sertoli cells are spermatogenic cells, which differentiate through meiosis to sperm cells. Sertoli cells function to nourish the developing sperm cells. They secrete androgen-binding protein, a binding protein which increases the concentration of testosterone. There are two types: convoluted and straight, convoluted toward the lateral side, and straight as the tubule comes medially to form ducts that will exit the testis. The seminiferous tubules are formed from the testis cords that develop from the primitive gonadal cords, formed from the gonadal ridge. Function Spermatogenesis, the process for producing spermatozoa, takes place in the semin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epididymis
The epididymis (; plural: epididymides or ) is a tube that connects a testicle to a vas deferens in the male reproductive system. It is a single, narrow, tightly-coiled tube in adult humans, in length. It serves as an interconnection between the multiple efferent ducts at the rear of a testicle (proximally), and the vas deferens (distally). Anatomy The epididymis is situated posterior and somewhat lateral to the testis. The epididymis is invested completely by the tunica vaginalis (which is continuous with the tunica vaginalis covering the testis). The epididymis can be divided into three main regions: * The head ( la, caput). The head of the epididymis receives spermatozoa via the efferent ducts of the mediastinium of the testis at the superior pole of the testis. The head is characterized histologically by a thick epithelium with long stereocilia (described below) and a little smooth muscle. It is involved in absorbing fluid to make the sperm more concentrated. The concentrat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paradidymis
The term paradidymis (organ of Giraldés) is applied to a small collection of convoluted tubules, situated in front of the lower part of the spermatic cord, above the head of the epididymis. These tubes are lined with columnar ciliated epithelium, and probably represent the remains of a part of the Wolffian body, like the epididymis, but are functionless and vestigial. The Wolffian body operates as a kidney (mesonephros The mesonephros ( el, middle kidney) is one of three excretory system, excretory organs that develop in vertebrates. It serves as the main excretory organ of aquatic vertebrates and as a temporary kidney in reptiles, birds, and mammals. The mesone ...) in fishes and amphibians, but the corresponding tissue is co-opted to form parts of the male reproductive system in other classes of vertebrate. The paradidymis represents a remnant of an unused, atrophied part of the Wolffian body. References {{Authority control Scrotum ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spermatozoon
A spermatozoon (; also spelled spermatozoön; ; ) is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote. (A zygote is a single cell, with a complete set of chromosomes, that normally develops into an embryo.) Sperm cells contribute approximately half of the nuclear genetic information to the diploid offspring (excluding, in most cases, mitochondrial DNA). In mammals, the sex of the offspring is determined by the sperm cell: a spermatozoon bearing an X chromosome will lead to a female (XX) offspring, while one bearing a Y chromosome will lead to a male (XY) offspring. Sperm cells were first observed in Antonie van Leeuwenhoek's laboratory in 1677. Mammalian spermatozoon structure, function, and size Humans The human sperm cell is the reproductive cell in males and will only survive in warm environments; once it leaves the male body the sperm's survival likelihood is reduced and it may die, thereby dec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wolffian Duct
The mesonephric duct (also known as the Wolffian duct, archinephric duct, Leydig's duct or nephric duct) is a paired organ that forms during the embryonic development of humans and other mammals and gives rise to male reproductive organs. Structure The mesonephric duct connects the primitive kidney, the '' mesonephros'', to the cloaca. It also serves as the primordium for male urogenital structures including the epididymis, vas deferens, and seminal vesicles. Development In both male and female the mesonephric duct develops into the trigone of urinary bladder, a part of the bladder wall, but the sexes differentiate in other ways during development of the urinary and reproductive organs. Male In a male, it develops into a system of connected organs between the efferent ducts of the testis and the prostate, namely the epididymis, the vas deferens, and the seminal vesicle. The prostate forms from the urogenital sinus and the efferent ducts form from the meso ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coelom
The coelom (or celom) is the main body cavity in most animals and is positioned inside the body to surround and contain the digestive tract and other organs. In some animals, it is lined with mesothelium. In other animals, such as molluscs, it remains undifferentiated. In the past, and for practical purposes, coelom characteristics have been used to classify bilaterian animal phyla into informal groups. Etymology The term ''coelom'' derives from the Ancient Greek word (), meaning 'cavity'. Structure Development The coelom is the mesodermally lined cavity between the gut and the outer body wall. During the development of the embryo, coelom formation begins in the gastrulation stage. The developing digestive tube of an embryo forms as a blind pouch called the archenteron. In Protostomes, the coelom forms by a process known as schizocoely. The archenteron initially forms, and the mesoderm splits into two layers: the first attaches to the body wall or ectoderm, forming ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epoophoron
The epoophoron or epoöphoron (also called organ of RosenmüllerJ. C. Rosenmüller. De ovariis embryonum et foetuum humanorum. 1802. or the parovarium) is a remnant of the mesonephric tubules that can be found next to the ovary and fallopian tube. Anatomy It may contain 10–15 transverse small ducts or tubules that lead to the Gartner’s duct (also longitudinal duct of epoophoron) that represents the caudal remnant of the mesonephric duct and passes through the broad ligament and the lateral wall of the cervix and vagina. The epoophoron is a homologue to the epididymis in the male. While the epoophoron is located in the lateral portion of the mesosalpinx and mesovarium, the paroophoron (residual remnant of that part of the mesonephric duct that forms the paradidymis in the male) lies more medially in the mesosalpinx. Histology It has a unique histological profile. Clinical significance Clinically the organ may give rise to a local paraovarian cyst or adenoma. See also * L ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paroöphoron
The paroophoron (of Johnson) consists of a few scattered rudimentary tubules, best seen in the child, situated in the broad ligament between the epoöphoron and the uterus. Named for the Welsh anatomist David Johnson who originally described the structure at the University of Wales, Aberystwyth. It is a remnant of the mesonephric tubules. See also * Epoophoron The epoophoron or epoöphoron (also called organ of RosenmüllerJ. C. Rosenmüller. De ovariis embryonum et foetuum humanorum. 1802. or the parovarium) is a remnant of the mesonephric tubules that can be found next to the ovary and fallopian tube ... References External links * * Mammal female reproductive system {{genitourinary-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
