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By C. Sulfock. McMurry University.

Embryonic males and females promethazine 25mg with mastercard, though genetically distinguishable 25 mg promethazine with visa, are morphologically identical (Figure 28 buy promethazine 25mg mastercard. Bipotential gonads discount 25 mg promethazine with amex, or gonads that can develop into male or female sexual organs buy promethazine 25 mg on line, are connected to a central cavity called the cloaca via Müllerian ducts and Wolffian ducts. The Müllerian ducts become the uterine tubes and uterus, and the cloaca divides and develops into a vagina, a urethra, and a rectum. The Fetal Circulatory System During prenatal development, the fetal circulatory system is integrated with the placenta via the umbilical cord so that the fetus receives both oxygen and nutrients from the placenta. However, after childbirth, the umbilical cord is severed, and the newborn’s circulatory system must be reconfigured. When the heart first forms in the embryo, it exists as two parallel tubes derived from mesoderm and lined with endothelium, which then fuse together. As the embryo develops into a fetus, the tube-shaped heart folds and further differentiates into the four chambers present in a mature heart. Unlike a mature cardiovascular system, however, the fetal cardiovascular system also includes circulatory shortcuts, or shunts. A shunt is an anatomical (or sometimes surgical) diversion that allows blood flow to bypass immature organs such as the lungs and liver until childbirth. The liver receives just a trickle of blood, which is all that it needs in its immature, semifunctional state. Blood flows from the inferior vena cava to the right atrium, mixing with fetal venous blood along the way. The fetal circulation therefore bypasses the lungs by shifting some of the blood through the foramen ovale, a shunt that directly connects the right and left atria and avoids the pulmonary trunk altogether. Most of the rest of the blood is pumped to the right ventricle, and from there, into the pulmonary trunk, which splits into pulmonary arteries. However, a shunt within the pulmonary artery, the ductus arteriosus, diverts a portion of this blood into the aorta. This ensures that only a small volume of oxygenated blood passes through the immature pulmonary circuit, which has only minor metabolic requirements. Blood vessels of uninflated lungs have high resistance to flow, a condition that encourages blood to flow to the aorta, which presents much lower resistance. The oxygenated blood moves through the foramen ovale into the left atrium, where it mixes with the now deoxygenated blood returning from the pulmonary circuit. Some of this blood moves through the coronary arteries into the myocardium, and some moves through the carotid arteries to the brain. The descending aorta carries partially oxygenated and partially deoxygenated blood into the lower regions of the body. The deoxygenated blood collects waste as it circulates through the fetal body and returns to the umbilical cord. Thus, the two umbilical arteries carry blood low in oxygen and high in carbon dioxide and fetal wastes. Oxygen and nutrients from the mother diffuse into the placenta and from there into the fetal blood, and the process repeats. The bone marrow begins to take over the process of erythrocyte production—a task that the liver performed during the embryonic period. The excretory system is also developing: the kidneys are well-formed, and meconium, or fetal feces, begins to accumulate in the intestines. During approximately weeks 16–20, as the fetus grows and limb movements become more powerful, the mother may begin to feel quickening, or fetal movements. However, space restrictions limit these movements and typically force the growing fetus into the “fetal position,” with the arms crossed and the legs bent at the knees. Sebaceous glands coat the skin with a waxy, protective substance called vernix caseosa that protects and moisturizes the skin and may provide lubrication during childbirth. A silky hair called lanugo also covers the skin during weeks 17–20, but it is shed as the fetus continues to grow. Developmental weeks 21–30 are characterized by rapid weight gain, which is important for maintaining a stable body temperature after birth. The bone marrow completely takes over erythrocyte synthesis, and the axons of the spinal cord begin to be myelinated, or coated in the electrically insulating glial cell sheaths that are necessary for efficient nervous system functioning. The lungs begin producing surfactant, a substance that reduces surface tension in the lungs and assists proper lung expansion after birth. The fetus at 30 weeks measures 28 cm (11 in) from crown to rump and exhibits the approximate body proportions of a full-term newborn, but still is much leaner.

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Undescended Ovaries reasonably rare gonad abnormality purchase 25mg promethazine with visa, often detected following clinical assessment of fertility problems and may also be associated with other uterine malformations (unicornuate uterus) discount promethazine 25 mg line. Due to the relative positions of the male (external) and female (internal) gonads and the pathways for their movement 25 mg promethazine sale, failure of gonad descent is more apparent and common in male cryptorchidism than female undescended ovaries generic 25 mg promethazine mastercard. Hydrocele Male Hydrocele is a fluid-filled cavity of either testis or spermatic cord generic promethazine 25mg visa, where peritoneal fluid passes into a patent processus vaginalis. Female Hydrocele is a similar, but rarer, fluid-filled cavity occuring in the female as a pouch of peritoneum extending into the labium majorum (canal of Nuck). Tract Abnormalities Many different forms Uterine: associated with other anomolies, unicornuate uterus Vagina: agenesis, atresia Ductus Deferens: Unilateral or bilateral absence, failure of mesonephric duct to differentiate Uterine Duplication (uterus didelphys, double uterus, uterus didelphis) A Uterine abnormalities rare uterine developmental abnormality where the paramesonephric ducts (Mullerian ducts) completely fail to fuse generating two separate uterus parts each connected to the cervix and having an ovary each. External Genitalia - Hypospadia Unicornate uterus most common penis abnormality (1 in 300) from a failure of male urogenital folds to fuse in various regions and resulting in a proximally displaced urethral meatus. The cause is unknown, but suggested to involve many factors either indivdually or in combination including: familial inheritance, low birth weight, assisted reproductive technology, advanced maternal age, paternal subfertility and endocrine-disrupting chemicals. Movies Urogenital Sinus Urogenital Septum Trigone Renal Nephron Uterus Female External Male External Testis Descent References Textbooks Before We Are Born (5th ed. Portions of the ear appear very early in development as specialized region (otic placode) on the embryo surface that sinks into the mesenchyme to form a vesicle (otic vesicle = otocyst) that form the inner ear. This region connects centrally to the nervous system and peripherally through specialized bones to the external ear (auricle). This organisation develops different sources forming the 3 ear parts: inner ear (otic placode, otocyst), middle ear (1st pharyngeal pouch and 1st and 2nd arch mesenchyme), and outer ear (1st pharyngeal cleft and 6 surface hillocks). This complex origin, organisation, and timecourse means that abnormal development of any one system can impact upon the development of hearing. Recent research suggests that all sensory placodes may arise from common panplacodal primordium origin around the neural plate, and then differentiate to eventually have different developmental fates. Other species have a number of additional placodes which form other sensory structures (fish, lateral line receptor). Note that their initial postion on the developing head is significantly different to their final position in the future sensory system. Otic Placode stage 13/14 embryo (shown below) the otic placode has sunk from Stage 14 sensory placodes the surface ectoderm to form a hollow epithelial ball, the otocyst, which now lies beneath the surface surrounded by mesenchyme (mesoderm). The epithelia of this ball varies in thickness and has begun to distort, it will eventually form the inner ear membranous labyrinth. Lens Placode lies on the surface, adjacent to the outpocketing of the nervous system (which will for the retina) and will form the lens. These placodes fold inwards forming a depression, then pinch off entirely from the surface forming a fluid-filled sac or vesicle (otic vesicle, otocyst). Stage 13 otocyst The vesicle sinks into the head mesenchyme some of which closely surrounds the otocyst forming the otic capsule. The otocyst finally lies close to the early developing hindbrain (rhombencephalon) and the developing vestibulo-cochlear-facial ganglion complex. The newborn external ear structure and position is an easily accessible diagnostic tool for potential abnormalities or further clinical screening. In the horizontal plane the meatus is boot-shaped with a narrow neck and the 10 weeks sole of the meatal plug spreading widely to form the future tympanic membrane medially. Disc-like plug innermost surface in contact with the 13 weeks primordial malleus, contributes to the formation of the tympanic membrane. Connects middle ear cavity to nasopharynx portion of pharynx Functions Ventilation - pressure equalization in the middle ear Clearance - allow fluid drainage from the middle ear Tube is Eustacian tube angle changes normally closed and opened by muscles At birth shorter (17-18 mm), narrower and runs almost horizontal Tube is opened by a single muscle, tensor palati muscle Adult longer (twice as long), wider and runs at approximately 45 degrees to the horizontal. Tube is opened by two separate muscles, tensor palati and levator palati Abnormalities Inner - common cavity, severe cochlear hypoplasia Middle - rare and can be part of first arch syndrome, Malleus, Incus and Stapes Fixation Cholesteatoma- Epithelium trapped within skull base in development, erosion of bones: temporal bone, middle ear, mastoid Outer - Several genetic effects and syndromes, Environmental Effects Outer Ear Abnormalities Microtia - abnormally small external ear Preauricular sinus - occurs in 0. Results show that a unilateral conductive hearing loss, in either infancy or adulthood, impairs binaural hearing both during and after the hearing loss. Show scant evidence for adaptation to the plug and demonstrate a recovery from the impairment that occurs over a period of several months after restoration of normal peripheral function. Anatomical description of the opening end of the uterine tube lying above the ovary and the enlarged initial segmeny of the semicircular canals of the inner ear vestibular system. It connects the basal turn of the cochlea perilymphatic space with the subarachnoid space of the posterior cranial cavity. Hes - (hairy and enhancer of split) family of factors, which has been shown to be a general negative regulator of neurogenesis {Zheng, 2000 #1936}. Hindbrain - Invaginate - Incus - (anvil) auditory ossicle inner phalangeal cells inner pillar cells - organ of Corti cells arranged in rows and form a boundary between the single row of inner hair cells and three rows of outer hair cells.

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Severe back pain is the presenting symptom as well as malaise buy promethazine 25mg cheap, fever promethazine 25mg fast delivery, neck stiffness and headache cheap promethazine 25mg with visa. Complications can include spinal cord compression as a result of vascular thrombosis generic 25 mg promethazine otc, infarction and irreversible paraplegia purchase 25mg promethazine. This is relatively rare and due to direct extension from infections of paranasal sinuses or skull and fractures of skull. Symptoms include local pain and tenderness, fever, chills, headache, neck stiffness. Complications include thrombophlebitis that may lead to superficial cerebral infarction and seizures. Patient age is most important factor in absolute attack rate and host susceptibility to bacterial meningitis. Over 70% of bacterial cases occur in children under 5 years; about 20% of cases occur in people over 70 years old. Most commonly encountered causative organisms according to patient age Neonates – Group B streptococci; E. Complications: Hydrocephalus; subdural effusion; cystic loculation of subarachnoid fluid; cranial nerve damage, especially deafness; focal neurological deficits; psychomotor retardation D. Brain abscesses are rare and are due to contiguous spread (most commonly from sinusitis, otitis, mastoiditis) or from blood- borne infection (vegetative endocarditis, pulmonary disease, especially bronchiectasis, intravenous drug abuse, congenital heart disease). Abscesses are often multiple; often in middle cerebral artery territory and have a predilection for the gray/white junction. Acanthamoeba, Naegleria, Trypanosoma and Toxoplasma cause diffuse meningoencephalitis; cerebral malaria (Plasmodium falciparum) lodges in capillaries resulting in petechial hemorrhages and angiitis Larger parasites obstruct larger blood vessels and/or migrate into cerebral parenchyma. Infected immuno-competent hosts may experience a transient parasitemia and lymphadenopathy, or may be entirely symptom free. It is felt that in immunocompromised patients, reactivation of the encysted organisms in the brain gives rise to toxoplasma encephalitis. Gross pathology: Toxoplasma infection tends to localize around ventricles in the basal ganglia and thalamus and at the junction of gray and white matter where it may cause focal abscesses. These small foci of infection will eventually evolve into abscesses with a central necrotic zone containing few identifiable organisms; and intermediate zone with vascular congestion, neutrophilic infiltration and numerous tachyzoites; and peripherally, a zone with relatively little inflammation but numerous encysted organisms. The fetus is infected via the placenta during maternal infection, and consequences are worst if the st nd infection occurs during the latter part of the 1 or entire 2 trimerster. Affected infants are often premature with jaundice, enlarged spleen and liver, chorioretinitis, microphthalmus. Microscopically there is necrotizing cerebritis, diffusely scattered foci of coagulative necrosis followed by calcification, meningeal inflammatory exudate. Hydrocephaly may occur as a result of periaqueductal inflammation, repair and aqueductal stenosis. Frequently both parenchyma and meninges are affected, and the condition is often referred to as meningoencephalitis. The ultimate diagnosis, however, depends on the isolation of the virus and/or correlation with positive serological tests. Infiltration by Inflammatory Cells: This is usually the most conspicuous histologic abnormality. Hyperplasia and Proliferation of Microglia: Seen throughout the brain and particularly in the cortex and basal ganglia. The microglia hypertrophy to form "rod cells" and these subsequently acquire long and slightly convoluted nuclei. They are most active in and around destroyed tissue where many become converted to lipid phagocytes (foam cells). Neuronophagia: This refers to phagocytosis of an injured neuron by a dense mass of hypertrophied microglia often obscuring the dead cell. However, in acute infections such as in polio, polymorphonuclear leukocytes are the cells involved in neuronophagia. Microglial Nodules and Gliomesenchymal nodules: Are often used synonymously to describe clusters of hypertrophied microglia admixed with other mononuclear cells not specifically related to nerve cells and occurring mainly in the white matter. It should be remembered that both neuronophagia and the microglial nodules, although frequently observed in viral encephalitidies, are by no means specific since both phenomena can occur in hypoxic brain damage. Astrocytic Proliferation: In acute encephalitis, enlarged astrocytes with plump cytoplasm are usually restricted to regions of tissue destruction.

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