pediagenosis: Reproductive
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Showing posts with label Reproductive. Show all posts
Showing posts with label Reproductive. Show all posts

Monday, September 20, 2021

TRAUMA

TRAUMA

TRAUMA

TRAUMA


Nonobstetric lacerations of the vaginal wall or introitus are most often the result of sexual trauma (consensual or otherwise). This may occur from intercourse (80%), saddle or water-skiing injury, sexual assault, or penetration by foreign objects. A rape injury, in particular, may be a potentially serious one, because it is often associated with psychological trauma (rape trauma syndrome), damage to adjacent vital organs, and even surgical shock. This is especially true when the injury occurs in a child. Inspection of the vestibule and vagina in such a case often reveals a jagged laceration, which has ruptured the hymen, torn the labia minora, and extended down the perineum toward the anus. Usually, the external genitalia are also badly damaged, with contusions and abrasions as far as the medial surfaces of the thighs. In more severely traumatized victims, the tears may compromise the integrity of the urethra, bladder, and rectum or breach the peritoneum. Such individuals may be brought into the hospital in a state of profound shock requiring immediate blood and fluid replacement before definitive surgical treatment can be instituted. In adults, common sites of lacerations are the vaginal wall, the lateral fornices, and the cul-de-sac. Rape injuries are dangerous in elderly, postmenopausal women who, because of vulvar and vaginal atrophy and the attendant increased fragility of the vaginal wall, are predisposed to more extensive damage. In younger women, the trauma to the vagina from rape is usually not so grave, although during pregnancy and in the immediate post-partum period, the tissues are vascular, delicate, and liable to injury.

TOXIC SHOCK SYNDROME

TOXIC SHOCK SYNDROME

TOXIC SHOCK SYNDROME

Toxic shock syndrome (TSS) is an uncommon, potentially life-threatening condition caused by toxins produced by an infection with Staphylococcus aureus. Toxic shock syndrome is rare, being seen in only 1 to 2/100,000 women 15 to 44 years old (last active surveillance done in 1987).

TOXIC SHOCK SYNDROME


Toxic shock syndrome requires infection by S. aureus and is associated with the use of super-absorbency tampons, or prolonged use of regular tampons, or barrier contraceptive devices. Although most commonly associated with prolonged tampon use, about 10% of TSS cases are associated with other conditions, including postoperative staphylococcal wound infections and nonsurgical focal infections. Postpartum cases (including transmission to the neonate) have been reported. Even the use of laminaria to dilate the cervix has been reported to be associated with rare cases. Overall, the prevalence of toxic shock syndrome appears to have declined with newer menstrual hygiene products and awareness of more appropriate use patterns.

VAGINITIS III—CHEMICAL, TRAUMATIC

VAGINITIS III—CHEMICAL, TRAUMATIC

VAGINITIS III—CHEMICAL, TRAUMATIC

VAGINITIS III—CHEMICAL, TRAUMATIC


Some vaginal inflammations, in addition to those due to direct bacterial invasion, are caused by the ill-advised introduction of foreign objects or substances. Vaginal douches and solutions have been used for a variety of gynecologic conditions, and an incalculable number of proprietary douche powders or fluids have been devised to alleviate or cure different types of real or perceived disturbances. Although it is doubtful that the brief contact of the vaginal epithelium with the materials contained in a commercial douche produces a salutary effect other than a cleansing one, the practice continues to be widespread. When homemade solutions or other agents are used, the risk is increased. The danger of such a procedure is the possibility of producing a chemical burn, with marked redness, swelling, and ulceration of the vaginal walls. Under these circumstances, a purulent exudate soon appears, and the patient suffers from intense local pain. Such accidents were particularly perilous when, during early pregnancy, various solutions were used to induce abortion. Even with the availability of elective pregnancy terminations, cases of this nature are still encountered. If the immediate damage has not been too severe, the inflammation may subside spontaneously or with mild palliative therapy, but if a necrotizing drug has been applied, adhesions may form that scar or occlude the vagina and cause dyspareunia.

VAGINITIS II—VENEREAL INFECTIONS

VAGINITIS II—VENEREAL INFECTIONS

VAGINITIS II—VENEREAL INFECTIONS

VAGINITIS II—VENEREAL INFECTIONS


In clinical practice an occasional case is seen in which the differential diagnosis of a lesion in the lower genital tract involves the exclusion of syphilis. In the female, primary lesions occur more often on the external genitalia and less frequently in the vagina or on the cervix. If in the vagina, a chancre is most likely to be near the vestibule, with no predilection for anterior, posterior, or lateral walls. It has the characteristic raised, indurated border surrounding a shallow ulceration. Because the disease is often in the lower third of the vagina, associated inguinal lymphadenopathy may be present. Although routine serologic tests are frequently negative at this stage, dark-field examination should lead to the proper diagnosis, and a biopsy can rule out other granulomas, carcinoma, or various infections. The mucous patches of late syphilis also occur in the vagina as well as on the external genitalia. They are white, vesicular lesions, which may coalesce and break down to form shallow ulcers and are not to be confused with the firm, raised condylomata lata, which are also late manifestations of syphilis. At this stage, a positive serologic test should indicate the probable diagnosis; a dark-field examination of scrapings is usually positive for Treponema pallidum. The Venereal Disease Research Laboratory (VDRL) and rapid plasma reagin (RPR) tests are good screening tests and the fluorescent treponemal antibody absorption or microhemagglutination T. pal-lidum tests are specific treponemal antibody tests that are confirmatory or diagnostic. Screening for HIV infection should also be strongly considered.

VAGINITIS I—TRICHOMONAS, MONILIA, BACTERIAL VAGINOSIS

VAGINITIS I—TRICHOMONAS, MONILIA, BACTERIAL VAGINOSIS

VAGINITIS I—TRICHOMONAS, MONILIA, BACTERIAL VAGINOSIS

VAGINITIS I—TRICHOMONAS, MONILIA, BACTERIAL VAGINOSIS


The vaginal flora has many different types of bacteria, some of which, like lactobacilli, are necessary for normal vaginal metabolism and for maintenance of the vaginal pH at the normal level of 3.8 to 4.2. Also present in numbers, which may be altered by such conditions as age, debility, systemic disease, ovulation, menstruation, and pregnancy are a variety of potentially pathogenic organisms. Among these are streptococci, staphylococci, colon bacilli, and fungi.

IMPERFORATE HYMEN, HEMATOCOLPOS, FIBROUS HYMEN

IMPERFORATE HYMEN, HEMATOCOLPOS, FIBROUS HYMEN

IMPERFORATE HYMEN, HEMATOCOLPOS, FIBROUS HYMEN

IMPERFORATE HYMEN, HEMATOCOLPOS, FIBROUS HYMEN


An imperforate hymen is the most commonly encountered anomaly resulting from abnormalities in the development or canalization of the müllerian ducts. It is caused by failure of the endoderm of the urogenital sinus and the epithelium of the vaginal vestibule to fuse and perforate during embryonic development. In addition to primary amenorrhea and coital dysfunction, an imperforate hymen may also be associated with endometriosis, vaginal adenosis, infertility, chronic pelvic pain, long-term sexual dysfunction, and hematocolpos. The hymen, located at the junction of the vagina and the vestibule, is the product of the combined embryo- logic fusion of the urogenital sinus and the müllerian ducts. As the urogenital sinus advances upward like a diverticulum from the outside, it envelops the column of müllerian cells, which has already moved nearly four-fifths of the distance from the cervix down to the vestibule. The infoldings of the sinus at the point of union form the lateral walls of the hymen, but the posterior or dorsal portion is a composite of sinus cells externally and müllerian cells internally. The superficial epithelium of the hymen, as of the vagina and cervical portio vaginalis, is derived entirely from the epithelium of the urogenital sinus, which pushes up the vaginal tube and undergoes differentiation into the stratified squamous layer. The opening of the vagina may occur independently of the formation of the hymen.

CONGENITAL ANOMALIES

CONGENITAL ANOMALIES

CONGENITAL ANOMALIES

CONGENITAL ANOMALIES


The müllerian ducts first appear between the seventh and eighth weeks of embryonic life as invaginations of the coelomic epithelium overlying the genital folds. These ducts migrate caudally in the developing embryo, cross toward the midline, and fuse to form the anlage of the uterus, cervix, and upper three-quarters of the vagina. The unfused, cranial portions of the müllerian ducts develop into the fallopian tubes. The caudal fused column of cells moves further downward to join the urogenital sinus, which pushes in from the perineal surface. With the sloughing of the internal core of the cell column to form the vagina, the process is completed in 5 to 6 weeks, although full differentiation takes several weeks longer.

The majority of congenital anomalies of the uterus and vagina are caused by a failure of the müllerian ducts to fuse completely or to develop after fusion. The most extreme anomaly results from complete lack of union of the ducts as a result of inhibition in growth at a very early stage. (The HOX genes have been shown to play key roles in body patterning and organogenesis, and in particular during genital tract development.) The result of this failure of fusion in the adult is the complete absence of the uterus and vagina, but with a normal ovary (because it is derived from a different embryonic source). The fallopian tube may be well developed or rudimentary. The tube is connected near the midline to a small bulb of fibrous tissue attached anteriorly to the bladder peritoneum and posteriorly to the peritoneum of the rectosigmoid. This bulb, which has its counterpart on the opposite side, represents the abortive attempt to form a uterus and may occasionally contain an endometrial lining. Because the vagina is absent, drainage of menstrual flow is impossible, and blood is retained within the genital tract or must drain into the peritoneal cavity. The external genitalia and the vaginal vestibule are normally developed, distinguishing this condition from pseudohermaphroditism. Vaginal atresia is often unrecognized until the occurrence of amenorrhea after puberty or dyspareunia after marriage. Above the vestibular dimple, between bladder and rectum, a potential space filled with loose areolar connective tissue may be found, which can be opened surgically. The term Mayer-Rokitansky-Küster-Hauser syndrome is sometimes applied to these cases of vaginal atresia, usually with absent cervix and uterus.

A less extreme degree of failure in müllerian fusion leads to a double vagina. In such instances the ducts have fused incompletely and have progressed independently to maturity. In the perineal view, the longitudinal septum dividing the vaginal compartments extends outward from the vestibule separating the two cervices. A longitudinal section through the vagina shows the appearance of the same anomaly from above, each uterus having its own fallopian tube and ovary, and each theoretically fertile. The partial septate vagina is a milder degree of congenital malformation, which is caused by a failure of the core of solid müllerian epithelium to slough completely at its lowermost portion. The frequent occurrence of vaginal anomalies with other congenital malformations in the genitourinary tract results from their common embryonic heritage. The possibility of associated lesions in the upper urinary tracts should always be investigated.

Incomplete canalization of the müllerian tubercle and sinovaginal bulb can result in a transverse vaginal septum. These patients will have a normal-appearing introitus leading to a foreshortened blind vaginal pouch. After puberty, a large hematocolpos or hematometrium may result from this outflow obstruction. Partial septa have been reported in women exposed in utero to diethylstilbestrol (DES).


VAGINA—CYTOLOGY

VAGINA—CYTOLOGY

VAGINA—CYTOLOGY

VAGINA—CYTOLOGY


The superficial cells of the vaginal epithelium are under the influence of ovarian hormones, changing in character over the course of a woman’s lifetime and the phases of the reproductive cycle. These variations are largely dependent upon the amount of circulating estrogen.

VULVA AND VAGINA HISTOLOGY

VULVA AND VAGINA HISTOLOGY

VULVA AND VAGINA HISTOLOGY

VULVA AND VAGINA HISTOLOGY


The vagina is lined by squamous epithelium and capable of dilation and constriction as a result of the action of its supporting muscles and erectile tissue. The three principal layers are easily recognized in the cross section through the vaginal wall. The epithelial surface is composed of stratified squamous epithelium divided into basal cell, transitional cell, and spinal or prickle cell layers, also referred to as basalis, intraepithelial, and functionalis. The superficial cells contain keratin but normally show no gross cornification in women of reproductive age. The epithelium is slightly thicker than the corresponding structure in the cervix and sends more and larger papillae into the underlying connective tissue, giving the basement membrane an undulating outline. These papillae are more numerous on the posterior wall and near the vaginal orifice. Beneath the epithelium, which has a thickness of 150 to 200 m, a dense connective tissue layer known as the lamina propria is supported by elastic fibers crossing from the epithelium to the underlying muscle. These elastic fibers, here and throughout the pelvis, are critical to pelvic support and function. The lamina propria becomes less dense as it approaches the muscle, and in this area it contains a network of large, thin-walled veins, giving it the appearance of erectile tissue. The smooth muscle beneath this layer is divided into internal circular and external longitudinal groups, the latter being thicker and stronger and continuous with the superficial muscle bundles of the uterus. No dividing membrane or fascia separates these two interlacing muscle groups. The adventitial coat of the vagina is a thin, firm, fibrous layer arising from the visceral or endopelvic fascia. In this fascia and in the connective tissue between it and the muscle runs another large network of veins and, in addition, a rich nerve supply. The Bartholin gland is situated just lateral to the vaginal vestibule and appears in cross section as a collection of small mucus-secreting glands lined by a single layer of columnar epithelial cells with basally placed nuclei. Occasionally, the columnar epithelium is stratified. The small glands tend to be oval and symmetric and are supported in a loose, vascular connective tissue. The main Bartholin duct is lined by columnar epithelium as it runs upward along the side of the vagina, but as it nears its opening in the midportion of the lateral wall of the vestibule, the epithelium takes on the stratified squamous characteristics of the vaginal epithelium. This transition accounts for the fact that malignant tumors of Bartholin gland may be of either the adenomatous or the squamous type.

FEMALE URETHRA

FEMALE URETHRA

FEMALE URETHRA

FEMALE URETHRA


The urethra, situated at the lowest portion of the bladder and passing downward and forward beneath the symphysis, varies from 3 to 5 cm in length and averages about 6 mm in diameter. The angle formed by the internal urethral orifice and the bladder at the bladder neck and surrounded by the intrinsic sphincter is critical to maintaining normal urinary continence; to with-stand the hydrostatic pressure of the bladder, this area is further supported by the fascia and tensing muscles of the pelvic diaphragm. Its mucosal surface is thrown into longitudinal folds by the constricting action of the external supporting structures. The most prominent of these longitudinal folds, situated on the posterior aspect of the urethra, is sometimes referred to as the urethral crest. The endopelvic fascia that covers the bladder is continuous over the entire urethra just below the mucosal layer, and contiguous to it is a thin layer of erectile tissue formed by the cavernous venous plexus. The muscular coats that surround the bladder also cover the urethra but become thinner as it passes down-ward toward the external meatus. The upper two-thirds of the urethra lie behind the symphysis pubis and are referred to as the intrapelvic urethra. It is this portion that passes through the musculofascial attachments forming the interlevator cleft. The perineal portion extends from the superior fascia of the urogenital diaphragm to the meatus. As it passes through the urogenital diaphragm, the urethra is surrounded by the sphincter urethrae membranaceae, the homologue of the muscle of the same name in the male but a far weaker and less important structure. Near the external meatus, the urethra is adjacent to the upper ends of the vestibular bulbs and the surrounding bulbocavernosus muscles. At its meatus, the urethra lies in the anterior vaginal wall between the folds of the labia minora 2 to 3 cm below the clitoris. Along its entire length, but especially in its perineal portion, the urethra is perforated by the openings of numerous small periurethral glands, the homologues of the prostatic ducts in the male.

Friday, June 18, 2021

SCROTAL SKIN DISEASES I: CHEMICAL AND INFECTIOUS

SCROTAL SKIN DISEASES I: CHEMICAL AND INFECTIOUS


SCROTAL SKIN DISEASES I: CHEMICAL AND INFECTIOUS

SCROTAL SKIN DISEASES I: CHEMICAL AND INFECTIOUS
Many skin diseases of infectious, allergic, or metabolic origin can involve the scrotum. Among many yeasts, molds, and fungi, only a few are infectious and are termed dermatophytes (“skin fungi”). Skin fungi live only on the dead layer of keratin protein on the skin surface. They rarely invade deeper and cannot live on mucous membranes. Infections by the fungus tinea cruris (ring-worm) are very common in the groin and scrotum. It involves desquamation of the scrotal skin and contiguous surfaces of the inner thighs and itches (“jock itch”). Tinea begins with fused, superficial, reddish-brown, well-defined scaly patches, which extend and coalesce into large, symmetrical, inflamed areas. The margins of the lesions are characteristically distinct. The initial lesion may become macerated and infected and is painful and itches. Sweating, tight clothing or obesity favor development and recurrence of this fungal infection, derived mainly from the genera Trichophyton and Microsporum. These same organisms cause tinea pedis or “athlete’s foot.”

Wednesday, May 5, 2021

Circulatory System: Blood Vessels

Circulatory System: Blood Vessels


Circulatory System: Blood Vessels
Time period: day 18 to birth
Vasculogenesis
Vasculogenesis is the formation of new blood vessels from cells that were not blood vessels before. As if by magic, blood cells and vessels appear in the early embryo. In fact, mesodermal cells are induced to differentiate into haemangioblasts, which further differentiate into both haematopoietic stem cells and angioblasts.
Haematopoietic stem cells will form all the blood cell types, and angioblasts will build the blood vessels. Separate sites of vasculogenesis may merge to form a network of blood vessels, or new vessels may grow from existing vessels by angiogenesis. When the liver forms it will be the primary source of new haematopoietic stem cells during development.

Angiogenesis
Angiogenesis is the development of new blood vessels from existing vessels. Endothelial cells detach and proliferate to form new capillaries. This process is under the influence of various chemical and mechanical factors. Although important in growth this also occurs in wound healing and tumour growth, and as such angiogenesis has become a target for anti‐cancer drugs.
Circulatory System: Blood Vessels, Angiogenesis, Primitive circulation, Aortic arches, Ductus arteriosus, Coronary arteries

Primitive circulation
Near the end of the third week blood islands form through vasculogenesis on either side of the cardiogenic field and the notochord (see Chapter 27). They merge, creating two lateral vessels called the dorsal aortae (Figure 29.1). These blood vessels receive blood from three pairs of veins, including the vitelline veins of the yolk sac (a site of blood vessel formation external to the embryo), the cardinal veins and the umbilical veins (Figure 29.1).
Circulation System: Changes At Birth

Circulation System: Changes At Birth


Circulation System: Changes At Birth
Time period: birth (38 weeks)
Foetal blood circulation
Dramatic and clinically significant changes occur to the circulatory and respiratory systems at birth. Here, we look at changes primarily of the circulatory system and how these changes prepare the baby for life outside the uterus.
If we were to follow the flow of oxygenated blood in the foetus from the placenta (Figure 31.1), we would start in the umbilical vein and track the blood moving towards the liver. Here, half the blood enters the liver itself and half is redirected by the ductus venosus directly into the inferior vena cava, bypassing the liver.
The blood remains well oxygenated and continues to the right atrium, from which it may pass into the right ventricle in the expected manner or directly into the left atrium via the foramen ovale (Figure 31.2). Blood within the left atrium passes to the left ventricle and then into the aorta.
Blood entering the right atrium from the superior vena cava and the coronary sinus is relatively poorly oxygenated. The small amount of blood that returns from the lungs to the left atrium is also poorly oxygenated. Mixing of this blood with the well‐oxygenated blood from the ductus venosus reduces the oxygen saturation somewhat.
Blood within the right ventricle will leave the heart within the pulmonary artery, but most of that blood will pass through the ductus arteriosus and into the descending aorta. Almost all of the well‐oxygenated blood that entered the right side of the heart has avoided entering the pulmonary circulation of the lungs, and has instead passed to the developing brain and other parts of the body (Figure 31.3).
Circulation System: Changes At Birth, Foetal blood circulation, Ductus venosus, Ductus arteriosus, Foramen ovale,

Ductus venosus
The umbilical arteries constrict after birth, preventing blood loss from the neonate. The umbilical cord is not cut and clipped immediately after birth, however, allowing blood to pass from the placenta back to the neonatal circulation through the umbilical vein.
Respiratory System

Respiratory System


Respiratory System
Time period: day 28 to childhood
Introduction
The development of the respiratory system is continuous from the fourth week, when the respiratory diverticulum appears, to term. The 24‐week potential viability of a foetus (approximately 50% chance of survival) is partly because at this stage the lungs have developed enough to oxygenate the blood. Limiters to oxygenation include the surface area available to gaseous exchange, the vascularisation of those tissues of gaseous exchange and the action of surfactant in reducing the surface tension of fluids within the lungs.
Development of the respiratory system includes not only the lungs, but also the conducting pathways, including the trachea, bronchi and bronchioles. Lung development can be described in five stages: embryonic, pseudoglandular, canalicular, saccular and alveolar.
Although not in use as gas exchange organs in utero, the lungs have a role in the production of some amniotic fluid.
Respiratory System, Lung bud, Respiratory tree, Alveoli,

Lung bud
The development of the respiratory system begins with the growth of an endodermal bud from the ventral wall of the developing gut tube in the fourth week (Figure 32.1).
Digestive System: Gastrointestinal Tract

Digestive System: Gastrointestinal Tract


Digestive System: Gastrointestinal Tract
Time period: days 21–50
Induction of the tube
The gut tube forms when the yolk sac is pulled into the embryo and pinched off (see Figure 20.2) as the flat germ layers of the early embryo fold laterally and cephalocaudally (head to tail). Consequently, it has an endodermal lining throughout with a minor exception towards the caudal end. Epithelium forms from the endoderm layer and other structures are derived from the mesoderm.
Initially, the tube is closed at both ends, although the middle remains in contact with the yolk sac through the vitelline duct (or stalk) even as the yolk sac shrinks (Figure 33.1).
The cranial end will become the mouth and is sealed by the buccopharyngeal membrane, which will break in the fourth week, opening the gut tube to the amniotic cavity. The caudal end will become the anus and is sealed by the cloacal membrane, which will break during the seventh week.
Buds develop along the length of the tube that will form a variety of gastrointestinal and respiratory structures (see Chapter 34).
Digestive System: Gastrointestinal Tract, Mesenteries, Story of the hindgut and the cloaca, Twists of the midgut

Divisions of the gut tube
The gut is divided into foregut, midgut and hindgut sections by the region of the gut tube that remains linked to the yolk sac and by the anterior branches from the aorta that supply blood to each part (Figure 33.2).

Saturday, April 24, 2021

Associated Organs

Associated Organs


Associated Organs
Time period: day 21 to birth
Introduction
In Chapter 33 we looked at the development of the gastrointestinal tract as a tube and mentioned a number of buds that sprout from the tube and its associated mesenchyme. These develop into a number of organs (Figure 34.1).

Digestive System: Associated Organs

Lung bud
As the oesophagus develops and elongates during week 4 the respiratory diverticulum buds off from its ventral wall (Figure 34.1). To create two separate tubes a septum forms between the respiratory bud and the oesophagus called the tracheoesophageal septum (see Figure 32.1). This creates the oesophagus dorsally and the respiratory primordium ventrally (see Chapter 32).
Congenital Anomalies

Congenital Anomalies


Congenital Anomalies
Time period: birth
Facial abnormalities
A relatively common congenital abnormality is cleft lip and/or cleft palate which affects around 1 in 600–700 live births and has a collection of defects.
Cleft lip (cheiloschisis) can be incomplete (affects upper lip only) or complete (continues into the nose) and unilateral (Figure 35.1) or bilateral. It is caused by the incomplete fusion of the medial nasal prominence with the maxillary process (Figure 35.2). When these fuse normally they form the intermaxillary segment, which goes on to become the primary (soft) palate.
The secondary (hard) palate forms from outgrowths of the maxillary process called the palatine shelves. Failure of these shelves to fuse or ascend to a horizontal position causes cleft palate (palatoschisis). In very severe cases the cleft can continue into the upper jaw. Cleft palate is often accompanied by cleft lip (complete), but not always (incomplete; Figure 35.3), and can also be unilateral or bilateral.
A cleft lip is generally diagnosed at the 20‐week anomaly scan, whereas cleft palates are diagnosed after birth. Cleft lips require surgical intervention before 3 months, whereas cleft palate surgery should happen before the child reaches 12 months old. Cleft lip and palate can affect feeding and speech, but also hearing. To aid prevention of cleft lip and palate maternal dietary folic acid is recommended (see also spina bifida, Chapter 17).
Digestive System: Congenital Anomalies

Foregut abnormalities
Abnormalities in development of the foregut can include stenosis and atresia at various points along its length, and hypertrophy of the pylorus of the stomach. Depending upon the point of restriction projectile vomiting can be a symptom, and the presence or absence of bile in the vomit can help diagnose the location.
Urinary System

Urinary System


Urinary System
Time period: day 21 to birth
Introduction
The development of the urinary system is closely linked with that of the reproductive system. They both develop from the intermediate mesoderm, which extends on either side of the aorta and forms a condensation of cells in the abdomen called the urogenital ridge. The ridge has two parts: the nephrogenic cord and the gonadal ridge (see Figure 38.2).

Urinary System

Kidneys
Three structures involved in kidney development grow from intermediate mesoderm in an anterior to posterior sequence, termed the pronephros, mesonephros and metanephros.
The pronephros appears in the third week in the neck region of the embryo and disappears a week later. In humans this is a primitive, non‐functional kidney that c ial nephrons joined to an unbranched nephric duct.

Tuesday, April 20, 2021

Gonads

Gonads


Gonads
Time period: day 30 to postnatal development
Introduction
In the chapter on renal development (see Chapter 36) we talked about the development of the gonadal ridge from intermediate mesoderm, an important source of cells for the reproductive system and the location for the beginning of the development of the gonads.

Reproductive System: Gonads

Gonads
Gonads are formed from three sources of cells: the intermediate mesoderm, the mesodermal epithelium that lines the developing urogenital ridge and germ cells.

Thursday, April 15, 2021

Endocrine System

Endocrine System


Endocrine System
Time period: day 24 to birth
Introduction
The glands of the endocrine system begin to form during the embryonic period and continue to mature during the foetal period. Functional development can be detected by the presence of the various hormones in the foetal blood, generally in the second trimester of pregnancy.
The development of the gonads, pancreas, kidneys and placenta are covered elsewhere in this book.
Endocrine System, Pituitary gland, Hypothalamus, Pineal body, Adrenal glands, Thyroid gland, Parathyroid glands,

Pituitary gland
Also known as the hypophysis, the pituitary gland develops from two sources. An out pocketing of oral ectoderm appears in week 3 in front of the buccopharyngeal membrane (Figure 39.1). This forms the hypophysial diverticulum (or Rathke’s pouch), which will become the anterior lobe.

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