EmbryologyLect5

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Published on August 4, 2007

Author: Malbern

Source: authorstream.com

Renal System Development:  Renal System Development ~12 weeks 10th week Development of Three Nephric SystemsCervical Nephrotomes & Mesonephroi:  Development of Three Nephric Systems Cervical Nephrotomes andamp; Mesonephroi Upper thoracic region to the third lumbar region Development of Three Nephric SystemsCervical Nephrotomes & Mesonephroi:  Development of Three Nephric Systems Cervical Nephrotomes andamp; Mesonephroi ~22 days 26 Days 6-10weeks-func andgt;10-regress. Mesonephric ducts in females regress and in males they persist to form parts of male genital duct system. Renal Corpuscle: Glomerulus andamp; Bowman’s capsule Mesonephric excretory unit: Renal corpuscle andamp; Nephric tubule Development of Three Nephric Systems.Mesonephroi & Metanephroi:  Development of Three Nephric Systems. Mesonephroi andamp; Metanephroi ~22 days Sacral Region Regress to the 1st three lumbar levels Mesonephric duct forming Reciprocal induction Collecting Duct System of the MetanephroiSequence of bifurcations.:  Collecting Duct System of the Metanephroi Sequence of bifurcations. Sequence of bifurcations:  Sequence of bifurcations ~22 days Sequence of bifurcations.:  Sequence of bifurcations. ~22 days 32nd Week 11 additional generations of bifurcations--andgt; 1-3 mil branches. 8 months Nephron Development:  Nephron Development ~22 days 9th week Contains neural crest derived neurons. They play a role in nephron induction. The neurons regulate blood flow and secretory function. Nephron Development:  Nephron Development 10th week 10weeks+--andgt;func: gl. filtrate to urine, but main func to produce amniotic fl. Definitive Kidney Architecture:  Definitive Kidney Architecture 5th-15th weeks Renal Pyramid (inner medulla) Contains the loops of Henle and collecting ducts . Contains the nephrons. Minor calyx Major calyx Pelvis Kidneys ascend from a sacral to lumbar location:  Kidneys ascend from a sacral to lumbar location ~22 days Movement of the Kidneys:  Movement of the Kidneys ~22 days Figure 8-6 Anomalies during kidney ascent:  Anomalies during kidney ascent ~22 days Inferior mesenteric artery The remainder of the urinary tract develops from the hingut endodermCloacal expansion and partition:  The remainder of the urinary tract develops from the hingut endoderm Cloacal expansion and partition 4th week 6th week Female Male Vestibule of Penile vagina urethra Membranous membranous urethra andamp; prostatic urethra Exstrophy of the mesonephric ducts and ureteric buds.:  Exstrophy of the mesonephric ducts and ureteric buds. 4-6 weeks -Endoderm grows over trigone -Splanchnopleuric mesoderm associated with the hindgut forms the smooth muscle of the bladder wall. * * * * * * * * Ureteric bud or metanephros induction defectsRenal agenesis:  Ureteric bud or metanephros induction defects Renal agenesis A. Defects in the inductive interaction between the ureteric bud and metanephric blastema may cause renal agenesis. B. Bilateral renal agenesis results in death. Unilateral renal agenesis results in hypertrophic kidney. C. 75% of the cases involving renal agenesis occur in males. D. Bilateral renal agenesis can also result in oligohydramnios, causing Potter’s syndrome (deformed limbs and facial defects. E. Unilateral renal agenesis is usually associated with heart defects and constrictions of the gastrointestinal tract. Genital System Development:  Genital System Development ~12 weeks 4-6 weeks The genital and urinary systems develop in close conjunctionPrimitive sex cord & Paramesonephric duct development:  The genital and urinary systems develop in close conjunction Primitive sex cord andamp; Paramesonephric duct development 5-6 weeks Third thoracic segment caudally to the posterior wall of the urogenital sinus (mullerian) Virtually identical male and female genital systems.:  Virtually identical male and female genital systems. At this point the sex cords have both a cortical and medullary region. After the 6th week these regions pursue different fates in the male and female. 6th week Basis of sex differentiationAutosomes and Sex Chromosomes:  Basis of sex differentiation Autosomes and Sex Chromosomes 1. There is a total complement of 46 chromosomes, 22 pairs consist of matching homologous chromosomes called autosomes. The 23rd pair are called the sex chromosomes because they determine the sex of the individual. 2. XX individuals are genetically female. XY individuals are genetically male. Subsequent phases of sexual development are controlled by both the sex chromosome genes and by the hormones and factors encoded by the autosomes. 3. The sex-determining region of the Y chromosome (SRY) encodes a transcription factor that controls the choice between the male and female developmental paths. Basis of sex differentiationAutosomes and Sex Chromosomes:  Basis of sex differentiation Autosomes and Sex Chromosomes 4. Male development is triggered when SRY is expressed in the sex cords during the indifferent phase. 5. Thus the male pathway is actively induced. Slide22:  Figure 10-13 Male genital (internal) DevelopmentSertoli cell differentiation in the medullary sex cords:  Male genital (internal) Development Sertoli cell differentiation in the medullary sex cords ~7th week Male genital (internal) DevelopmentAnti-Mullerian hormone (AMH) secretion by Sertoli cells:  Male genital (internal) Development Anti-Mullerian hormone (AMH) secretion by Sertoli cells ~8-12th week Ductuli efferentes Sertoli Cells (reminant of inferior mesonephric tubules) (reminant of cranial end of mesonephric duct) Male genital (internal) DevelopmentDifferentiation of the mesonephric ducts of the male:  Male genital (internal) Development Differentiation of the mesonephric ducts of the male ~10th-12th week Male genital (internal) DevelopmentDifferentiation of the accessory glands of the male urethra:  Male genital (internal) Development Differentiation of the accessory glands of the male urethra ~10th-12th weeks Female genital (internal) developmentAbsence of a Y chromosome:  Female genital (internal) development Absence of a Y chromosome Female genital (internal) developmentAbsence of AMH in the female embryo:  Female genital (internal) development Absence of AMH in the female embryo Female genital (internal) developmentAbsence of AMH in the female embryo:  Female genital (internal) development Absence of AMH in the female embryo Female genital (internal) developmentAbsence of AMH in the female embryo:  Female genital (internal) development Absence of AMH in the female embryo External genitalia developmentMale and Female external genitalia develop from the same primordia:  External genitalia development Male and Female external genitalia develop from the same primordia or urethral fold External genitalia is similar in male and female embryos through the 12th week. External genitalia development.Male external genitalia.:  External genitalia development. Male external genitalia. 12 weeks 14 weeks External genitalia developmentFemale external genitalia:  External genitalia development Female external genitalia 7th week 3rd month The gubernaculum controls the descent of the testes and ovariesThe descent of the testes:  The gubernaculum controls the descent of the testes and ovaries The descent of the testes The gubernaculum controls the descent of the testes and ovariesThe descent of the testes:  The gubernaculum controls the descent of the testes and ovaries The descent of the testes The gubernaculum controls the descent of the testes and ovariesThe descent of the testes:  The gubernaculum controls the descent of the testes and ovaries The descent of the testes The gubernaculum controls the descent of the testes and ovarieThe descent of the ovaries:  The gubernaculum controls the descent of the testes and ovarie The descent of the ovaries Abnormal dev of the genital system:  Abnormal dev of the genital system Testicular Feminization Syndrome--andgt; the androgen receptors are abnormal or lacking, resulting in the formation of a blind-ending vagina (Male genotype, Female external phenotype, no ovaries). Since the testes are still present and AMH is produced, the paramesonephric ducts regress (Thus no superior vagina, uterus, or fallopian tubes). Abnormal dev of the genital system:  Abnormal dev of the genital system True hermaphrodites--andgt; have both ovarian and testicular tissue. The gonads are usually a composite ovotestes containing both seminiferous tubules and follicles. Or an individual may have an ovary on one side and a testes on the other side. Most true hermaphrodites are reared as males since a phallus is usually present at birth.

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