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They give rise to vitelline vessels and are the major site of red blood cell formation in the early embryo medicine 906 generic 250 mg mildronate with mastercard. Initially medicine zetia discount mildronate 250mg, the developing cranial portion of the neural tube lies dorsal and caudal to the oropharyngeal membrane symptoms prostate cancer cheap mildronate 250mg fast delivery. However symptoms 0f a mini stroke cheap 250 mg mildronate, overgrowth of the forebrain causes it to extend past the oropharyngeal membrane and overhang the cardiogenic area. Subsequent growth of the forebrain pushes the developing heart ventrally and caudally to a position in the presumptive thoracic region caudal to the oropharyngeal membrane and cranial to the septum transversum that will form the central tendon of the diaphragm. Gastrulation (answer a) is the process by which epiblast cells migrate to the primitive streak and become internalized to form the mesodermal and endodermal germ layers. Lateral folding (answer b) of the embryo forms the endoderm tube and surrounding concentric layering of mesoderm and ectoderm. Neurulation refers to formation of the neural tube from surface ectoderm (answer d). The fusion of the two endocardial heart tubes (answer e) occurs as lateral folding occurs. The fused tube will form the endocardium surrounded by the primordial myocardium derived from splanchnic mesoderm that will form the heart muscle (myocardium). During implantation, the syncytiotrophoblast invades the endometrium and erodes the maternal blood vessels. Maternal blood and nutrient glandular secretions fill the lacunae and bathe the projections of syncytiotrophoblast. Primary villi consist of syncytiotrophoblast with a core of cytotrophoblast cells. In secondary villi, the cytotrophoblast core is invaded by mesoderm and subsequently by umbilical blood vessels in tertiary villi. During the third through eighth weeks of embryonic life, organ systems are developing and are most susceptible to teratogens. During that time, each organ system has its own specific period of peak susceptibility. Exposure of the embryo to teratogens during the first 2 weeks of fetal life (answers a and b) generally induces spontaneous abortion and is, therefore, lethal. After the eighth week of intrauterine development (answers d and e), teratogenic exposure generally results in retardation of organ growth rather than in new structural or functional changes. Retinoic acid directs the polarity of development in the central nervous system, the axial skeleton (vertebral column), and probably the appendicular skeleton. Retinoic acid induces transcription of various combinations of homeobox genes, depending on tissue type and location (distance and direction from the source of retinoic acid). Exogenous sources of retinoic acid may induce the wrong sequence or combination of homeobox genes, leading to structural abnormalities in nervous and skeletal systems. The other organ systems listed are not as susceptible to vitamin A (answers a, b, c, and d). Duodenal and/or esophageal atresia result in an inability of the fetus to swallow amniotic fluid (answer c). The result is that normal recirculation of amniotic fluid through the embryo is greatly reduced or eliminated, causing an excess of amniotic fluid. Low volumes of amniotic fluid (oligohydramnios) are caused by rupture of the fetal membranes, bilateral agenesis of the kidneys (answer b), or obstructive uropathy (answer e, blockage of the calyces or ureters), which prevents urine from being added to the amniotic fluid. Hypoplasia of the lungs (answer d) and compression of the umbilical cord are associated with oligohydramnios, but do not cause it. The presence of adequate fluid in the uninflated lungs is essential for lung maturation, and growth factors in the amniotic fluid may also be important. Low levels of Embryology: Early and General Answers 91 amniotic fluid severely inhibit lung development. The formula for understanding the relationship between urine and amniotic fluid is: Less urine output = less amniotic fluid; less swallowing = more amniotic fluid. This first stage of neural tube development is followed by a reshaping phase, neurulation, and neural tube closure. The somatopleuric mesoderm (answer c) makes important contributions to the skin (dermis) and nonmuscle portions of the limbs. The hypoblast (answer e) is the thin layer of cells ventral to the epiblast; it is displaced by the epiblast cells, which form endoderm. The intermediate mesoderm is the origin of the urogenital systems and the adrenal cortex (answer a).

The lower rectum drains along the inferior rectal lymphatics and then along both internal and external pudendal lymphatic channels symptoms lyme disease generic mildronate 250mg fast delivery. The result may be varices of the pampiniform plexus on the left side with reduced fertility symptoms constipation discount mildronate 500mg visa. Emissary veins connect with the dural sinuses with potential for vascular spread of infection through the calvaria shakira medicine purchase 250mg mildronate free shipping. From either full adduction or abduction the the eye is then moved in a second direction treatment low blood pressure generic 500mg mildronate fast delivery. When fully adducted raising the eye above the horizon tests the inferior oblique muscle. When fully abduced, raising the eye above the horizon tests the superior rectus muscle. Temporal lobe herniation (from tumor, hematoma, or edema) compresses the oculomotor nerve within the tentorial notch, causing a dilated pupil that is unresponsive to light. It may be anesthetized by directing a needle posteriorly through the buccal wall just lateral to the pterygomandibular raphe. A 29-year-old woman (gravida 3, para 2) gave birth to a healthy baby after 38 weeks of gestation and delivered the intact placenta spontaneously. The pregnancy was complicated by preeclampsia, but fetal monitoring and ultrasound were normal throughout gestation. The predominant structures shown in the accompanying photomicrograph of the placenta are derived from which of the following A married couple, with diagnosed 6-year-long infertility, presents to the fertility clinic. A spermocytogram, confirmed by electron microscopy, reveals that the husband produces all spermatozoa with rounded heads, a condition known as globozoospermia. Loss of decapacitation factors Retention of the developing spermatids from Sertoli cells Maturation of lytic enzymes Mitotic activity Meiotic divisions 3. Which of the following is required for continuation of the second meiotic division to produce the haploid ovum A hamster egg penetration assay was performed in which hamster eggs are collected and their zona pellucidae are enzymatically removed prior to mixing with sperm. Sperm formation, maturation and penetration Addition of cholesterol to the sperm plasma membrane A decrease in the fluidity of the sperm plasma membrane Sequestration of acrosomal enzymes Capacitation, acrosome reaction and penetration Embryology: Early and General 73 5. The oocyte of a mature follicle will be induced to undergo the first meiotic division as a result of which of the following hormonal stimuli Following intercourse, which of the following is responsible for the prevention of polyspermy Resumption of the first meiotic division Resumption of the second meiotic division Capacitation the zona reaction the release of enzymes from the sperm acrosome 7. Oogonia reach their maximum number at which of the following stages of human development Five months of fetal life Birth Puberty (12 to 14 years of age) Adolescence (16 to 20 years of age) Early adulthood (21 to 26 years of age) 8. Approximately how much time is required for the return of viable sperm to the epididymis Implantation of the conceptus at which site in the accompanying diagram of the female reproductive system is most likely to result in excessive, perhaps fatal, vaginal bleeding immediately prior to parturition Cells that form the three primitive germ layers are derived from which of the following In the developing human embryo/fetus, most of the internal organs begin to form in which month The primitive uteroplacental circulation is functionally established during which period of embryonic/fetal development Hypoblast Epiblastic cells that undergo gastrulation Mesoderm Endoderm Nongastrulated epiblast 14.

This tendency was particularly pronounced among the post-Korean War generation that constituted a majority of the South Korean population bad medicine 1 buy generic mildronate 250 mg line. The unpopular Chun regime and its constitutional framework was brought down in 1987 largely by the student agitation that beset the regime shinee symptoms purchase mildronate 500 mg free shipping. Student activists set the tone and agenda of the society as a whole because the government and the governmentcontrolled press had lost their credibility symptoms nausea fatigue cheap mildronate 500 mg with mastercard. The opposition parties worked with the students symptoms vaginitis buy 500mg mildronate visa, although they disagreed on the ultimate aim the politicians wanted reform, while the students demanded revolution. The opposition politicians wanted constitutional reform to replace the existing system of electing the president through the handpicked electoral college with direct popular election. The students attacked not only the military leaders in power but also the entire socio-political and economic establishment. They argued that the basic cause for the political and social malaise in South Korea was "American imperialism," which they believed had dominated South Korea ever since it was liberated from Japan - in 1945. In their view, "American imperialism" buttressed the military dictatorship and the exploitative capitalist system; the strug- gle against the military dictatorship inseparable. This position and American imperialism was was the same argument that North Korea had been advancing since 1946, but a more important source of intellectual persuasion came from the revisionist school of histori- ography that swept United States academia during the 1970s. United States participation in the Korean War and the subsequent stationing of United States forces in South Korea satisfied such a need, according to this perspective. For the revisionists, it was irrelevant that the United States had decided to abandon Korea in September-October 1947, or that the United States had withdrawn its occupation forces from South Korea in 1949. The fact that the United States had interjected itself into the Korean War in 1950, and that it continued to station its troops in South Korea after the war, was evidence enough. The inquisitive students had long viewed the onesided anticommunist propaganda emanating from official and established sources as stifling particularly ical and as leaving too logical many questions unanswered. The new arguments sounded and convincing, to the streets when some of the revisionists took liberty with histor- evidence. Increasing numbers of students took denounce the military dictatorship and American imperialism. Initially, the public was apathetic to the confrontation between the student demonstrators and government, but the daily fracas on the streets and the never-ending smell of tear gas aroused their ire. President Chun attempted to squash the opposition by issuing a declaration on April 13, 1987, to suspend the 'wasteful debate" about constitutional reform until a new government was installed at the end of his seven-year term. Chun wanted to have his successor "elected" by his handpicked supporters; the public greeted the declaration with universal outrage. A number of books treat Korea in the modern era, although most of them emphasize the political aspect of the society. For the government under see and Policies in Diviand the EcoRepublic of Korea by Edward S. When the war ended in 1945, the great majority of the people living in the southern half of the Korean Peninsula were poor peasants. The Japanese colonial regime from 1910 to 1945 had promoted modernization of the economy and society. The poverty and distress of the South Koreans were deepened by the Korean War of 1950-53 when numerous people died and cities and towns were devastated. During the next four decades, however, South Korea evolved into a dynamic, industrial society. By 1990 educational and public health standards were high, most people lived in urban areas, and a complex structure of social classes had emerged that resembled the social structures of developed Western countries or Japan. The country also was making substantial progress in its evolution from a military dictatorship similar to that of many Third World regimes to pact on most Koreans inasmuch as the ization a democratic, pluralistic political system. Colonial occupation, war, and the tragedy of national division fostered abrupt social changes. Rapid economic growth engendered profound changes in values and human relationships. Confucian and neo-Confucian ideas and institutions, which flourished during the Choson Dynasty - (1392-1910), continued to have an important impact in 1990.

This is appositional growth without a cartilage intermediate (intramembranous ossification) treatment 5th metatarsal shaft fracture purchase mildronate 250mg mastercard. It is one of the best examples of intramembranous ossification medications not to mix buy mildronate 500 mg amex, even though it occurs in the development of a long bone red carpet treatment buy mildronate 500 mg without prescription. The action of osteoblasts is to deposit bone matrix and secrete alkaline phosphatase; they do not proliferate in either the primary or the secondary ossification centers symptoms ruptured ovarian cyst buy mildronate 500mg with amex. This role is particularly important in the articular cartilages, which receive pressure during joint movement and are required to resist strong compressive forces. They possess a large anionic charge because of the presence of sulfate, hydroxyl, and carboxyl groups within the glycosaminoglycans, which join to form proteoglycan subunits by linking with a core protein (answer c). The proteoglycan subunits (monomers) subsequently form an aggregate by linking noncovalently to hyaluronic acid (answer c). The negative charge of the glycosaminoglycans facilitates the binding of cations (answer b) and the transport of electrolytes and water within the matrix. This is an important aspect of cartilage metabolism because the chondrocytes depend on diffusion to obtain nutrients or to dispose of waste products. The zone shown is the region of chondrocyte Specialized Connective Tissues: Bone and Cartilage Answers 207 hypertrophy, and the cells synthesize alkaline phosphatase, which calcifies the cartilage matrix. This secretion results in the eventual death of these cells that depend on diffusion to obtain oxygen and nutrients from the matrix. During development of the long bones of the body, specific zones are established, as a cartilage model of a long bone is converted to mature bone. The zones from the epiphysis toward the center of the shaft (diaphysis) are as follows: resting zone, proliferative zone, hypertrophy zone, and zone of calcified cartilage that is used as the scaffolding for the deposition of bone. The periosteal bud represents the ingrowth of blood vessels (angiogenesis) bringing, bone marrow precursors and osteoprogenitor cells into the diaphysis. Bone is formed by the action of osteoblasts forming type I collagen, noncollagenous proteins. Cyclins are synthesized by cells passing through the cell cycle, cells in the proliferative zone (answer a); acid phosphatase (answer b) is synthesized by osteoclasts; and type I collagen and osteocalcin (answers d and e) are synthesized by osteoblasts. Osteoclasts function by release of lytic enzymes and protons (derived from carbonic acid) into the calcified matrix beneath the ruffled border and not through a grinding action (answer a). The bone compartment around the ruffled border of the osteoclast is, therefore, analogous to a secondary lysosome in function, albeit extracellular. Osteoclasts use protons derived from carbonic acid, catalyzed by carbonic anydrase, in similar fashion to parietal cells of the stomach. The electron micrograph illustrates the typical ultrastructure of an osteoclast with its distinctive ruffled border. The arrowhead in the electron micrograph 208 Anatomy, Histology, and Cell Biology indicates collagen within the degraded bone matrix. The plasmalemma of the osteoclast adjacent to the resorbing bone surface is thrown into folds and villous-like processes with tips that reach and even enter the bone surface (ruffled border). The osteoclast is attached to the bone surface, and the resorption area is sealed off by the presence of contractile proteins in the cytoplasm lateral to the site of the ruffled border. Vitamin D receptors are also present on osteoblasts and absent from the plasma membrane of osteoclasts (answer c). In the presence of high Ca2+, calcitonin is synthesized and released from C (interfollicular, parafollicular) cells of the thyroid, which decreases ruffled-border activity. However, calcitonin measurements are an important tool in the diagnosis of medullary thyroid carcinoma, a malignancy of thyroid cells. Calcitonin is also used as a nasal spray for osteoporosis when patients cannot tolerate bisphosphonates. They function by inhibiting osteoclastic activity through apoptosis of osteoclasts. Deposition of rheumatoid factor can be pathogenic and leads to inflammatory destruction of the joint surface. Alteration of the synovial membrane results in the formation of a pannus, or inflammatory, hypertrophic synovial villus.

Recycling of synaptic vesicle membrane occurs at the presynaptic membrane in conjunction with neurotransmitter release by exocytosis medications similar buspar safe 500mg mildronate. Neurotransmitter release is induced by membrane depolarization symptoms rotator cuff injury mildronate 250 mg for sale, leading to transient opening of calcium channels followed by calcium influx 5 medications related to the lymphatic system order mildronate 250mg with amex. Transmission from neuron to neuron occurs by chemical transmission in the Nervous System Answers 249 form of neurotransmitter release symptoms 0f kidney stones discount 500mg mildronate. The neurotransmitter (from the synaptic vesicles) crosses the synaptic cleft (between the pre- and postsynaptic membranes) and interacts with receptors on the postsynaptic membrane (answer b), which results in changes in the permeability of this membrane (answer c). Numerous mitochondria and synaptic vesicles are typically found on the presynaptic side of the synapse. On autopsy, plaques are found that contain lymphocytes and monocytes in infiltrates around small veins in what is known as perivascular cuffing. The main identifying feature on histopathological examination is the paucity of oligodendrocytes. In myasthenia gravis, the postsynaptic muscle membrane is smooth and lacks the normal folded shape. The edrophonium chloride (tensilon) test uses a rapid acting and degrading acetylcholine esterase inhibitor. The physician injects the tensilon and then looks for rapid relief of the symptoms, particularly the eyelids and the diplopia. Other structures labeled in the electron micrograph are: A = nucleus, B = mitochondria, C = myofilaments, and D = nerve terminal. Myeloblast Proerythroblast Metamyelocyte Myelocyte Promyelocyte Cardiovascular System, Blood, and Bone Marrow 253 153. A newborn girl presents with a mutation in the erythropoietin receptor gene which leads to primary familial erythrocytosis (familial polycythemia). During the 5th to 9th months of fetal development, the primary effect was on red blood cell production in which of the following A 64-year-old man presents with splenomegaly, lymphadenopathy, persistent fever, night sweats, and weight loss. Organs such as the brain and thymus have a more effective bloodbarrier because their blood capillaries are of which of the following types Continuous type with few vesicles Fenestrated type with diaphragms Fenestrated type without diaphragms Discontinuous type with diaphragms Discontinuous type without diaphragms 156. On cardiac catheterization there is occlusion of the left anterior descending and the origin of the right coronary artery. Proliferation of smooth muscle cells Formation of an intimal plaque Attraction of platelets to collagen microfibrils Adventitial proliferation Injury to the endothelium 254 Anatomy, Histology, and Cell Biology 157. His lower limbs appear cold, pale, and discolored, and he has a sore on the skin of his left calf. In this patient, which of the following functions would be primarily affected in the blood vessel from the lower extremity shown in the accompanying transmission electron micrograph Adaptation to systolic pressure Distribution of blood within an organ Blood flow from the aorta to specific organs Return of lymphocytes to the blood Return of venous blood to the heart Cardiovascular System, Blood, and Bone Marrow 255 158. Her fresh blood is drawn and centrifuged in the presence of heparin as an anticoagulant to obtain a hematocrit. Serum, packed erythrocytes, and leukocytes Leukocytes, erythrocytes, and serum proteins Plasma, buffy coat, and packed erythrocytes Fibrinogen, platelets, buffy coat, and erythrocytes Albumin, plasma lipoproteins, and erythrocytes 159. Decreased clotting time Normal blood count Abnormal bruising Hypercoagulation Light menstrual periods 256 Anatomy, Histology, and Cell Biology 160. A 47-year-old man presents to his family physician complaining of unusual thirst, increased frequency of urination, dizziness, blurred vision, and numbness in his left foot. Over time, which of the following describes the changes that may occur in the structure labeled "A" in the accompanying light micrograph Loss of beta cells Arteriosclerosis Progressive decrease in nerve conduction velocity Altered smooth muscle glucose transporter function Altered lymphatic flow Cardiovascular System, Blood, and Bone Marrow 257 161.