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Development Of The Gonads
The development of the gonads is part of the prenatal development of the reproductive system and ultimately forms the testes in males and the ovaries in females. The gonads initially develop from the mesothelial layer of the peritoneum. The ovary is differentiated into a central part, the medulla, covered by a surface layer, the germinal epithelium. The immature ova originate from cells from the dorsal endoderm of the yolk sac. Once they have reached the gonadal ridge they are called oogonia. Development proceeds and the oogonia become fully surrounded by a layer of connective tissue cells (pre-granulosa cells). In this way, the rudiments of the ovarian follicles are formed. In the testis, a network of tubules fuse to create the seminiferous tubules. Via the rete testis, the seminiferous tubules become connected with outgrowths from the mesonephros, which form the efferent ducts of the testis. The descent of the testes consists of the opening of a connection from the testis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prenatal Development
Prenatal development () includes the development of the embryo and of the fetus during a viviparous animal's gestation. Prenatal development starts with fertilization, in the germinal stage of embryonic development, and continues in fetal development until birth. In human pregnancy, prenatal development is also called antenatal development. The development of the human embryo follows fertilization, and continues as fetal development. By the end of the tenth week of gestational age the embryo has acquired its basic form and is referred to as a fetus. The next period is that of fetal development where many organs become fully developed. This fetal period is described both topically (by organ) and chronologically (by time) with major occurrences being listed by gestational age. The very early stages of embryonic development are the same in all mammals, but later stages of development, and the length of gestation varies. Terminology In the human: Different terms are used to ... [...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] |
Ovary
The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the body. The ovaries also secrete hormones that play a role in the menstrual cycle and fertility. The ovary progresses through many stages beginning in the prenatal period through menopause. It is also an endocrine gland because of the various hormones that it secretes. Structure The ovaries are considered the female gonads. Each ovary is whitish in color and located alongside the lateral wall of the uterus in a region called the ovarian fossa. The ovarian fossa is the region that is bounded by the external iliac artery and in front of the ureter and the internal iliac artery. This area is about 4 cm x 3 cm x 2 cm in size.Daftary, Shirish; Chakravarti, Sudip (2011). Manual of Obstetrics, 3rd Edition. Elsevier. pp. 1-16. . The ovari ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Testis
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 caliper ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mesothelial
The mesothelium is a membrane composed of simple squamous epithelial cells of mesodermal origin, which forms the lining of several body cavities: the pleura (pleural cavity around the lungs), peritoneum (abdominopelvic cavity The abdominopelvic cavity is a body cavity that consists of the abdominal cavity and the pelvic cavity. The upper portion is the abdominal cavity, and it contains the stomach, liver, pancreas, spleen, gallbladder, kidneys, small intestine, and ... including the mesentery, omentum (other), omenta, falciform ligament and the perimetrium) and pericardium (around the heart). Mesothelial tissue also surrounds the male testis (as the tunica vaginalis) and occasionally the spermatic cord (in a patent processus vaginalis). Mesothelium that tunica (biology), covers the internal organs is called visceral mesothelium, while one that covers the surrounding body walls is called the :wikt:parietal, parietal mesothelium. The mesothelium that secretes serous ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gonad
A gonad, sex gland, or reproductive gland is a mixed gland that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gonad, the testicle, produces sperm in the form of spermatozoa. The female gonad, the ovary, produces egg cells. Both of these gametes are haploid cells. Some hermaphroditic animals have a type of gonad called an ovotestis. Evolution It is hard to find a common origin for gonads, but gonads most likely evolved independently several times. Regulation The gonads are controlled by luteinizing hormone and follicle-stimulating hormone, produced and secreted by gonadotropes or gonadotrophins in the anterior pituitary gland. This secretion is regulated by gonadotropin-releasing hormone produced in the hypothalamus. Development Gonads start developing as a common primordium (an organ in the earliest stage of development), in the form of genital ridges, which are only l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spermatogonia
A spermatogonium (plural: ''spermatogonia'') is an undifferentiated male germ cell. Spermatogonia undergo spermatogenesis to form mature spermatozoa in the seminiferous tubules of the testis. There are three subtypes of spermatogonia in humans: *Type A (dark) cells, with dark nuclei. These cells are reserve spermatogonial stem cells which do not usually undergo active mitosis. *Type A (pale) cells, with pale nuclei. These are the spermatogonial stem cells that undergo active mitosis. These cells divide to produce Type B cells. *Type B cells, which undergo growth and become primary spermatocytes. Anticancer drugs Anticancer drugs such as doxorubicin and vincristine can adversely affect male fertility by damaging the DNA of proliferative spermatogonial stem cells. Experimental exposure of rat undifferentiated spermatogonia to doxorubicin and vincristine indicated that these cells are able to respond to DNA damage by increasing their expression of DNA repair genes, and that this r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Allantois
The allantois (plural ''allantoides'' or ''allantoises'') is a hollow sac-like structure filled with clear fluid that forms part of a developing amniote's conceptus (which consists of all embryonic and extraembryonic tissues). It helps the embryo exchange gases and handle liquid waste. The allantois, along with the amnion, chorion, and yolk sac (other extraembryonic membranes), identify humans and other mammals, birds, and other reptiles as amniotes. Fish and amphibians are anamniotes, and lack the allantois. In mammals the extraembryonic membranes are known as the fetal membranes. Function This sac-like structure, whose name is the New Latin equivalent of "sausage" (in reference to its shape when first formed) is primarily involved in nutrition and excretion, and is webbed with blood vessels. The function of the allantois is to collect liquid waste from the embryo, as well as to exchange gases used by the embryo. In mammals In mammals excluding egg-laying monotremes, the all ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Germ Cell
Germ or germs may refer to: Science * Germ (microorganism), an informal word for a pathogen * Germ cell, cell that gives rise to the gametes of an organism that reproduces sexually * Germ layer, a primary layer of cells that forms during embryonic development * Cereal germ, the reproductive part of a cereal grain * Tooth germ, an aggregation of cells that eventually forms a tooth * Germ theory of disease, which states that some diseases are caused by microorganisms * Germ (mathematics), an object in a topological space that captures local properties Art and media Music * Germs (band), an American punk rock band * Germ (musician), a stage name of Tim Wright * Germ (rapper), an American rapper affiliated with Suicideboys and Pouya * "Germs" (song), by "Weird Al" Yankovic * ''The Germ'' (album), by Victim's Family Others * "Germs" (''Invader Zim''), an episode of ''Invader Zim'' * ''The Germ'' (periodical), a British art magazine published in 1850 * The Germs (comics) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Indirect Inguinal Hernia
An inguinal hernia is a hernia (protrusion) of abdominal cavity, abdominal-cavity contents through the inguinal canal. Symptoms, which may include pain or discomfort especially with or following coughing, exercise, or bowel movements, are absent in about a third of patients. Symptoms often get worse throughout the day and improve when lying down. A bulging area may occur that becomes larger when bearing down. Inguinal hernias occur more often on the right than left side. The main concern is strangulation, where the Circulatory system, blood supply to part of the intestine is blocked. This usually produces severe pain and tenderness of the area. Risk factors for the development of a hernia include: Tobacco smoking, smoking, chronic obstructive pulmonary disease, obesity, pregnancy, peritoneal dialysis, collagen vascular disease, and previous open appendectomy, among others. Predisposition to hernias is Genetic predisposition, genetic and they occur more often in certain families. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scrotum
The scrotum or scrotal sac is an anatomical male reproductive structure located at the base of the penis that consists of a suspended dual-chambered sac of skin and smooth muscle. It is present in most terrestrial male mammals. The scrotum contains the external spermatic fascia, testes, epididymis, and ductus deferens. It is a distention of the perineum and carries some abdominal tissues into its cavity including the testicular artery, testicular vein, and pampiniform plexus. The perineal raphe is a small, vertical, slightly raised ridge of scrotal skin under which is found the scrotal septum. It appears as a thin longitudinal line that runs front to back over the entire scrotum. In humans and some other mammals the scrotum becomes covered with pubic hair at puberty. The scrotum will usually tighten during penile erection and when exposed to cold temperatures. One testis is typically lower than the other to avoid compression in the event of an impact. The scrotum is biologicall ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gubernaculum
The paired gubernacula (from Ancient Greek κυβερνάω = pilot, steer) also called the caudal genital ligament, are embryonic structures which begin as undifferentiated mesenchyme attaching to the caudal end of the gonads (testes in males and ovaries in females). Structure The gubernaculum is present only during the development of the reproductive system. It is later replaced by distinct vestiges in males and females.The gubernaculum arises in the upper abdomen from the lower end of the gonadal ridge and helps guide the testis in its descent to the inguinal region. Males * The upper part of the gubernaculum degenerates. * The lower part persists as the gubernaculum testis ("scrotal ligament"). This ligament secures the testis to the most inferior portion of the scrotum, tethering it in place and limiting the degree to which the testis can move within the scrotum. * Cryptorchidism (undescended testes) are observed in ''INSL3''-null male mice. This implicates INSL3 as a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
