DOCSLIB.ORG

Development of the Penis and Scrotum Reproductive System > Embryology > Embryology

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Development of the Penis and Scrotum Reproductive System > Embryology > Embryology Development of the Penis and Scrotum Reproductive System > Embryology > Embryology MALE EXTERNAL GENITALIA Includes the penis, penile urethra, and scrotum (which houses the testes). During gestation, development is heavily influenced by testosterone produced by the Leydig (aka, interstitial) cells of the testes. Weeks 3-4 • Period of undifferentiated primordial genitalia • The genital tubercle, which is the precursor to the penis, emerges. • Cloacal membrane is bordered by the primorida of the genital tubercle, and is surrounded by mesenchymal cells. • Anterior fusion of the primordia forms the definitive genital tubercle. — Posteriorly, the unfused portion gives rise to the urogenital (aka, genital) folds, which enclose the cloacal membrane. — Lateral to the folds the genital swellings (aka, labioscrotal swellings) arise. Weeks 7-12 The urorectal septum has reached the cloacal membrane and now forms the perineal body; male differentiation begins. • The perineal body divides the cloacal membrane into urogenital and anal membranes, which then rupture, forming the urogenital sinus and anus. • The genital tubercle enlarges and is now referred to as the phallus. • The urogenital folds are now the urethral folds, as they line the urethral groove. — The roof of the groove comprises an endodermal expansion. • Distally is the glans, and the glans plate, which is a solid endodermal remnant of the cloacal membrane. • The genital swellings are now the scrotal swellings. • Posteriorly, the perineum separates the urethral folds and groove from the anus. Week 12 The urethral folds and scrotal swellings fuse at the midline. • Fusion of the urethral folds forms the floor of the spongy urethra within the shaft of the penis. • Midline raphes reflect fusion of the tissues. • The surrounding mesenchyme will give rise to the erectile tissues and vasculature of the penis. • Formation of the glans portion of the urethra occurs separately, via canalization of the glans plate (the exact mechanism is uncertain). • At the midline, the raphe reflects the fusion of the urethral folds. 1 / 2 9 Months Folds are fully fused, and urethral opening is at the tip of the penis. The scrotal sac houses the testes. Clinical Correlation • Hypospadia — Incomplete fusion of the urethra leads to hypospadias, in which the urethral opening is displaced ventrally. Summary: Genital tubercle -> Shaft and glans of the penis Genital folds -> Floor of the spongy urethra Genital swellings -> Scrotum TESTICULAR DESCENT:  Week 7 The testes are originally located within the abdominal cavity, deep to the peritoneum (aka, retroperitoneal). • The caudal genital ligament attaches to the superior pole of the testes. • The gubernaculum anchors the inferior pole to the scrotal swelling, inferiorly. Week 12 The peritoneum begins to evaginates, forming the vaginal process as it grows towards and into the scrotal swelling. A* s it migrates, the vaginal process creates a cavity as it pushes through the abdominal wall layers, ultimately giving rise to the inguinal canals. 9 Months The testes have traveled through the inguinal canals to reach the scrotal sac; thus, in the mature form, the testes are external to the pelvic cavity. • Though the caudal genital ligament regresses, the gubernaculum persists to anchor the testis. - — The gubernaculum directs the testis during its migration through the inguinal canal to the scrotal sac; although the exact mechanisms are uncertain, shortening of the gubernaculum paired with growth of the abdominal organs (and, consequently, increased intra-abdominal pressure) likely facilitate testes descent. Clinical Correlation • Cryptorchidism — Failure of one or both testes to descend into the scrotal sac; if the testes remain undescended too long after birth, surgery may be required. Additional resources: - Li, Y., Sinclair, A., Cao, et al. Canalization of the Urethral Plate Precedes Fusion of the Urethral Folds during Male Penile Urethral Development: The Double Zipper Hypothesis. Journal of Urology: 193(4): 1353-1360 (2015). - Hadidi, A., Roessler, J., Coerdt, W. Development of the Human Male Urethra: A Histochemical Study on Human Embryos. Journal of Pediatric Surgery. 49: 1146-1152. (2014). - Cunha, G.R., Sinclair, A., Risbridger, G., Hutson, J. & Baskin, L.S. Current Understanding of Hypospadias: Relevance of Animal Models. Nature Reviews in Urology.(2015) doi: 10.1038/nrurol.2015.57. UC San Francisco: 898757. Retrieved from: http://escholarship.org/uc/item/60s7k7n0 February 15, 2017. - Singh, V. Textbook of Clinical Embryology. Elsevier Health Sciences. (2012). Powered by TCPDF (www.tcpdf.org) 2 / 2.
Load more

Recommended publications
  • 3 Embryology and Development
    BIOL 6505 − INTRODUCTION TO FETAL MEDICINE 3. EMBRYOLOGY AND DEVELOPMENT Arlet G. Kurkchubasche, M.D. INTRODUCTION Embryology – the field of study that pertains to the developing organism/human Basic embryology –usually taught in the chronologic sequence of events. These events are the basis for understanding the congenital anomalies that we encounter in the fetus, and help explain the relationships to other organ system concerns. Below is a synopsis of some of the critical steps in embryogenesis from the anatomic rather than molecular basis. These concepts will be more intuitive and evident in conjunction with diagrams and animated sequences. This text is a synopsis of material provided in Langman’s Medical Embryology, 9th ed. First week – ovulation to fertilization to implantation Fertilization restores 1) the diploid number of chromosomes, 2) determines the chromosomal sex and 3) initiates cleavage. Cleavage of the fertilized ovum results in mitotic divisions generating blastomeres that form a 16-cell morula. The dense morula develops a central cavity and now forms the blastocyst, which restructures into 2 components. The inner cell mass forms the embryoblast and outer cell mass the trophoblast. Consequences for fetal management: Variances in cleavage, i.e. splitting of the zygote at various stages/locations - leads to monozygotic twinning with various relationships of the fetal membranes. Cleavage at later weeks will lead to conjoined twinning. Second week: the week of twos – marked by bilaminar germ disc formation. Commences with blastocyst partially embedded in endometrial stroma Trophoblast forms – 1) cytotrophoblast – mitotic cells that coalesce to form 2) syncytiotrophoblast – erodes into maternal tissues, forms lacunae which are critical to development of the uteroplacental circulation.
    [Show full text]
  • Te2, Part Iii
    TERMINOLOGIA EMBRYOLOGICA Second Edition International Embryological Terminology FIPAT The Federative International Programme for Anatomical Terminology A programme of the International Federation of Associations of Anatomists (IFAA) TE2, PART III Contents Caput V: Organogenesis Chapter 5: Organogenesis (continued) Systema respiratorium Respiratory system Systema urinarium Urinary system Systemata genitalia Genital systems Coeloma Coelom Glandulae endocrinae Endocrine glands Systema cardiovasculare Cardiovascular system Systema lymphoideum Lymphoid system Bibliographic Reference Citation: FIPAT. Terminologia Embryologica. 2nd ed. FIPAT.library.dal.ca. Federative International Programme for Anatomical Terminology, February 2017 Published pending approval by the General Assembly at the next Congress of IFAA (2019) Creative Commons License: The publication of Terminologia Embryologica is under a Creative Commons Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0) license The individual terms in this terminology are within the public domain. Statements about terms being part of this international standard terminology should use the above bibliographic reference to cite this terminology. The unaltered PDF files of this terminology may be freely copied and distributed by users. IFAA member societies are authorized to publish translations of this terminology. Authors of other works that might be considered derivative should write to the Chair of FIPAT for permission to publish a derivative work. Caput V: ORGANOGENESIS Chapter 5: ORGANOGENESIS
    [Show full text]
  • Development of the Female Reproductive System
    Development of the female Reproductive System Dr. Susheela Rani Genital System •Gonads •Internal genitals •External genitals Determining sex – chronology of events •Determined Genetic sex at fertilization Gonadal sex •6th week Phenotypic sex •Differentiation of Behavioural Psyche - Preoptic and Median region Sex of Hypothalamus Genetic Sex Genetic sex of an embryo is determined at the time of fertilization, depending on whether the spermatocyte carries an X or a Y chromosome. The ‘Master’ Gene that determines Gender • SRY (Sex determining Region Y gene) • Has a testis-determining effect on the indifferent gonads. • Small gene (a single exon) • Localized on the shorter arm of the Y chromosome (Yp) • Gets expressed in the gonadal cells • Controls a whole number of further genes on the autosomes as well as on the X chromosome. • Causes development of Testes • Pseudo autosomal regions PAR1 and PAR 2 – Yellow • Heterochromatin – redundant DNA sequences – Pink • SRY – Region for Sex Determining Gene- Dark red • ZFY , Y linked Zinc Finger Protein – Orange • Spermatogenesis Genes in long arm – Azoospermia factor AZF • Telomeres – green • Centromeres - Blue It is not the number of gonosomes that is decisive for the gender, but rather the presence or absence of the Y-chromosome Aneuploidy and Euploidy of Gonosomes Karyotype Phenotypic Gonad Syndrome Fate Gender 45, XO Female Ovaries Turner’s Atrophy of Ovaries in the fetus 45, YO ------ ----- ----- Absence of X chromosome is lethal 46, XX Female Ovaries Normal Normal Development Woman 47, XXX Female
    [Show full text]
  • Comparative Gene Expression Analysis of Genital Tubercle Development Reveals a Putative Appendicular Wnt7 Network for the Epidermal Differentiation
    Developmental Biology 344 (2010) 1071–1087 Contents lists available at ScienceDirect Developmental Biology journal homepage: www.elsevier.com/developmentalbiology Genomes & Developmental Control Comparative gene expression analysis of genital tubercle development reveals a putative appendicular Wnt7 network for the epidermal differentiation Han Sheng Chiu a, John C. Szucsik b, Kylie M. Georgas a, Julia L. Jones c, Bree A. Rumballe a, Dave Tang a, Sean M. Grimmond a, Alfor G. Lewis b, Bruce J. Aronow b,c, James L. Lessard b, Melissa H. Little a,⁎ a Institute for Molecular Bioscience, The University of Queensland, St. Lucia 4072, Australia b Division of Developmental Biology, Cincinnati Children's Hospital Research Foundation, Cincinnati, OH 45229, USA c Division of Biomedical Informatics, Cincinnati Children's Hospital Research Foundation, Cincinnati, OH 45229, USA article info abstract Article history: Here we describe the first detailed catalog of gene expression in the developing lower urinary tract (LUT), Received for publication 30 November 2009 including epithelial and mesenchymal portions of the developing bladder, urogenital sinus, urethra, and Revised 23 April 2010 genital tubercle (GT) at E13 and E14. Top compartment-specific genes implicated by the microarray data Accepted 15 May 2010 were validated using whole-mount in situ hybridization (ISH) over the entire LUT. To demonstrate the Available online 24 May 2010 potential of this resource to implicate developmentally critical features, we focused on gene expression Keywords: patterns and pathways in the sexually indeterminate, androgen-independent GT. GT expression patterns Genital tubercle development reinforced the proposed similarities between development of GT, limb, and craniofacial prominences. Lower urinary tract development Comparison of spatial expression patterns predicted a network of Wnt7a-associated GT-enriched epithelial Gene expression genes, including Gjb2, Dsc3, Krt5, and Sostdc1.
    [Show full text]
  • MR Imaging of Vaginal Morphology, Paravaginal Attachments and Ligaments
    MR imaging of vaginal morph:ingynious 05/06/15 10:09 Pagina 53 Original article MR imaging of vaginal morphology, paravaginal attachments and ligaments. Normal features VITTORIO PILONI Iniziativa Medica, Diagnostic Imaging Centre, Monselice (Padova), Italy Abstract: Aim: To define the MR appearance of the intact vaginal and paravaginal anatomy. Method: the pelvic MR examinations achieved with external coil of 25 nulliparous women (group A), mean age 31.3 range 28-35 years without pelvic floor dysfunctions, were compared with those of 8 women who had cesarean delivery (group B), mean age 34.1 range 31-40 years, for evidence of (a) vaginal morphology, length and axis inclination; (b) perineal body’s position with respect to the hymen plane; and (c) visibility of paravaginal attachments and lig- aments. Results: in both groups, axial MR images showed that the upper vagina had an horizontal, linear shape in over 91%; the middle vagi- na an H-shape or W-shape in 74% and 26%, respectively; and the lower vagina a U-shape in 82% of cases. Vaginal length, axis inclination and distance of perineal body to the hymen were not significantly different between the two groups (mean ± SD 77.3 ± 3.2 mm vs 74.3 ± 5.2 mm; 70.1 ± 4.8 degrees vs 74.04 ± 1.6 degrees; and +3.2 ± 2.4 mm vs + 2.4 ± 1.8 mm, in group A and B, respectively, P > 0.05). Overall, the lower third vaginal morphology was the less easily identifiable structure (visibility score, 2); the uterosacral ligaments and the parau- rethral ligaments were the most frequently depicted attachments (visibility score, 3 and 4, respectively); the distance of the perineal body to the hymen was the most consistent reference landmark (mean +3 mm, range -2 to + 5 mm, visibility score 4).
    [Show full text]
  • Cranial Cavitry
    Embryology Endo, Energy, and Repro 2017-2018 EMBRYOLOGY OF THE REPRODUCTIVE SYSTEM Janine Prange-Kiel, Ph.D. Office: L1.106, Phone: 83117 Email: [email protected] LEARNING OBJECTIVES: • Name the structures in kidney development that contribute to the development of the reproductive organs. • Predict how the presence or absence of the Y chromosome and the expression of the SRY gene would influence the development of the gonads. • Predict how the presence or absence of testosterone, dihydrotestosterone, and anit- Mullerian hormone would influence the development of the genital ducts and indifferent primordia of the external genitalia. I. Introduction In general, the function of the genital (reproductive) system in males and females is the formation, nurture, and transport of germ cells. In females, an additional function is to provide the proper milieu for the fetal development after conception. Like the urinary system, the genital system derives from intermediate mesoderm. The development of these two systems is tightly interwoven as structures that develop as parts of the urinary system gain function in the genital system. In the adult, the sexual organs differ between males and females. The early genital system, however, is similar in both sexes, and the sexual differentiation of this initially indifferent, bipotential system starts only in the seventh week of embryonic development. The details on how sexual differentiation is determined will be discussed below, but it is worth mentioning here that irregularities in this process result in disorders of sexual differentiation (DSDs). DSDs occur in approximately 1 in 4,500 live births and will be discussed in a separate lecture.
    [Show full text]
  • Urinary System Intermediate Mesoderm
    Urinary System Intermediate mesoderm lateral mesoderm: somite ectoderm neural NOTE: Intermediate mesoderm splanchnic groove somatic is situated between somites and lateral mesoderm (somatic and splanchnic mesoderm bordering the coelom). All mesoderm is derived from the primary mesen- intermediate mesoderm endoderm chyme that migrated through the notochord coelom (becomes urogenital ridge) primitive streak. Intermediate mesoderm (plus adjacent mesothelium lining the coelom) forms a urogenital ridge, which consists of a laterally-positioned nephrogenic cord (that forms kidneys & ureter) and a medially-positioned gonadal ridge (for ovary/testis & female/male genital tract formation). Thus urinary & genital systems have a common embryonic origin; also, they share common ducts. NOTE: Urine production essentially requires an increased capillary surface area (glomeruli), epithelial tubules to collect plasma filtrate and extract desirable constituents, and a duct system to convey urine away from the body. Kidneys Bilateraly, three kid- mesonephric duct neys develop from the neph- metanephros pronephros rogenic cord. They develop mesonephric tubules chronologically in cranial- mesonephros caudal sequence, and are designated pro—, meso—, Nephrogenic Cord (left) and meta—, respectively. cloaca The pronephros and mesonephros develop similarly: the nephrogenic cord undergoes seg- mentation, segments become tubules, tubules drain into a duct & eventually tubules disintegrate. spinal ganglion 1] Pronephros—consists of (7-8) primitive tubules and a pronephric duct that grows caudally and terminates in the cloaca. The tubules soon degenerate, but the pronephric duct persists as the neural tube mesonephric duct. (The pronephros is not functional, somite except in sheep.) notochord mesonephric NOTE tubule The mesonephros is the functional kidney for fish and am- aorta phibians. The metanephros is the functional kidney body of reptiles, birds, & mammals.
    [Show full text]
  • The Derivatives of Three-Layered Embryo (Germ Layers)
    HUMANHUMAN EMBRYOLOGYEMBRYOLOGY Department of Histology and Embryology Jilin University ChapterChapter 22 GeneralGeneral EmbryologyEmbryology FourthFourth week:week: TheThe derivativesderivatives ofof trilaminartrilaminar germgerm discdisc Dorsal side of the germ disc. At the beginning of the third week of development, the ectodermal germ layer has the shape of a disc that is broader in the cephalic than the caudal region. Cross section shows formation of trilaminar germ disc Primitive pit Drawing of a sagittal section through a 17-day embryo. The most cranial portion of the definitive notochord has formed. ectoderm Schematic view showing the definitive notochord. horizon =ectoderm hillside fields =neural plate mountain peaks =neural folds Cave sinks into mountain =neural tube valley =neural groove 7.1 Derivatives of the Ectodermal Germ Layer 1) Formation of neural tube Notochord induces the overlying ectoderm to thicken and form the neural plate. Cross section Animation of formation of neural plate When notochord is forming, primitive streak is shorten. At meanwhile, neural plate is induced to form cephalic to caudal end, following formation of notochord. By the end of 3rd week, neural folds and neural groove are formed. Neural folds fuse in the midline, beginning in cervical region and Cross section proceeding cranially and caudally. Neural tube is formed & invade into the embryo body. A. Dorsal view of a human embryo at approximately day 22. B. Dorsal view of a human embryo at approximately day 23. The nervous system is in connection with the amniotic cavity through the cranial and caudal neuropores. Cranial/anterior neuropore Neural fold heart Neural groove endoderm caudal/posterior neuropore A.
    [Show full text]
  • Reproductionreview
    REPRODUCTIONREVIEW Cryptorchidism in common eutherian mammals R P Amann and D N R Veeramachaneni Animal Reproduction and Biotechnology Laboratory, Colorado State University, Fort Collins, Colorado 80523-1683, USA Correspondence should be addressed to R P Amann; Email: [email protected] Abstract Cryptorchidism is failure of one or both testes to descend into the scrotum. Primary fault lies in the testis. We provide a unifying cross-species interpretation of testis descent and urge the use of precise terminology. After differentiation, a testis is relocated to the scrotum in three sequential phases: abdominal translocation, holding a testis near the internal inguinal ring as the abdominal cavity expands away, along with slight downward migration; transinguinal migration, moving a cauda epididymidis and testis through the abdominal wall; and inguinoscrotal migration, moving a s.c. cauda epididymidis and testis to the bottom of the scrotum. The gubernaculum enlarges under stimulation of insulin-like peptide 3, to anchor the testis in place during gradual abdominal translocation. Concurrently, testosterone masculinizes the genitofemoral nerve. Cylindrical downward growth of the peritoneal lining into the gubernaculum forms the vaginal process, cremaster muscle(s) develop within the gubernaculum, and the cranial suspensory ligament regresses (testosterone not obligatory for latter). Transinguinal migration of a testis is rapid, apparently mediated by intra-abdominal pressure. Testosterone is not obligatory for correct inguinoscrotal migration of testes. However, normally testosterone stimulates growth of the vaginal process, secretion of calcitonin gene-related peptide by the genitofemoral nerve to provide directional guidance to the gubernaculum, and then regression of the gubernaculum and constriction of the inguinal canal. Cryptorchidism is more common in companion animals, pigs, or humans (2–12%) than in cattle or sheep (%1%).
    [Show full text]
  • Genital System • Anatomically, the Genital System Is Subdivided Into
    Genital system • Anatomically, the genital system is subdivided into: 1- sex glands ( Testis and Ovary). 2- duct system ( male or female duct system) 3- external genitalia ( scrotum and penis in male, vulva in female) . • Embryollogically, from the time of fertilization the sex of the embryo can be determined genetically (male XY and female XX). • In early stage of development the sex of embryo cannot be differentiated anatomically or histologically, this stage is termed indifferent stage. • Later on ,sex hormones induce differentiation into male or female and in the same time the structure of the other sex degenerate. Indifferent Stage:- • In this stage the sex of the embryo cannot be differentiated anatomically or histologically. • This stage includes development of : - - gonads. - duct system - external genitalia. A- Gonads 1. Due to enlargement of mesonephros, it bulges ventrolaterally into the coelum forming a longitudinal urogenital ridge. 2. This ridge subdivided longitudinally into a lateral urinary ridge and medial genital ridge. 2. The genital (gonadal) ridge or gonad results from proliferation of celomatic epithelium. 3. This celomatic epithelium forms sex cord which project in the underlying mesenchyme . 4. The primordial germ cells which are located between the endodermal cells of the yolk sac, migrate through the mesentery of the hind gut to be located in the sex cord of the gonads. 5. Therefore the gonad has three types of cells: -Primordial germ cells. -celomatic cells -mesenchymal cells. B- Duct system • Both male and female embryos have initially two pairs of genital ducts: Mesonephric and Paramesonephric. 1. Mesonephric (Wolffian) duct: • The Mesonephric duct and tubules remain after degeneration of mesonephros forming the male duct system.
    [Show full text]
  • Transverse Plane Through the Scrotum and Inguinal Canal
    UNDERSTANDING THE CRYPTORCHID Transverse Plane through the This section is designed to make the procedure of castration and Scrotum and Inguinal Canal crytorchidectomy easier to understand. Some oversimplification of the embryology of the testis and the assumption that readers are familiar with anatomical and developmental terminology is required for brevity. The following is not intended to be a detailed discussion of the embryology of male development in the horse, but a simplified version pointing out some important factors in the surgical anatomy of cryptorchid castrations. For more detailed information, please refer to the selected bibliography at the end of this section. Anatomy and Anatomical Terminology The word “cryptorchid” is used to describe any testis that is not in the scrotum. There are three types of cryptorchids. 1. Inguinal 2. Abdominal 3. Incomplete In the normal juvenile or adult male horse the testis is found in the scrotum. A peritoneal process, the “vaginal tunic” (or just “the Note that the tunic and the peritoneal tunic”) passes through the inguinal canal and surrounds the blood lining are one continuous structure. and nerve supply to the testis, as well as the vas deferens, and surrounds testis and epididymis in the scrotum. (The blood vessels are branches of the testicular artery and vein, which leave the caudal aorta and vena cava in the dorsal lumbar region, near the kidneys.) The inguinal canal in the horse is relatively longer than in other species and runs between a deep and a superficial hole in the body wall. These are called the “internal inguinal ring” and the “external inguinal ring”, respectively.
    [Show full text]
  • Development of the Human Penis and Clitoris
    Differentiation xxx (xxxx) xxx–xxx Contents lists available at ScienceDirect Differentiation journal homepage: www.elsevier.com/locate/diff ☆ Development of the human penis and clitoris ⁎ ⁎⁎ Laurence Baskin , Joel Shen, Adriane Sinclair , Mei Cao, Xin Liu1, Ge Liu1, Dylan Isaacson, Maya Overland, Yi Li, Gerald R. Cunha UCSF, USA ARTICLE INFO ABSTRACT Keywords: The human penis and clitoris develop from the ambisexual genital tubercle. To compare and contrast the de- Development velopment of human penis and clitoris, we used macroscopic photography, optical projection tomography, light Human sheet microscopy, scanning electron microscopy, histology and immunohistochemistry. The human genital tu- Penis bercle differentiates into a penis under the influence of androgens forming a tubular urethra that develops by Clitoris canalization of the urethral plate to form a wide diamond-shaped urethral groove (opening zipper) whose edges Canalization and fusion (urethral folds) fuse in the midline (closing zipper). In contrast, in females, without the influence of androgens, the vestibular plate (homologue of the urethral plate) undergoes canalization to form a wide vestibular groove whose edges (vestibular folds) remain unfused, ultimately forming the labia minora defining the vaginal ves- tibule. The neurovascular anatomy is similar in both the developing human penis and clitoris and is the key to successful surgical reconstructions. 1. Introduction literature, in recent years we have recognized that the mouse is not the ideal model for normal human penile development and hypospadias for Male and female external genitalia play an essential role in human a host of reasons (Cunha et al., 2015; Liu et al., 2018b; Sinclair et al., reproduction, and disorders of structure and function of male and fe- 2016).
    [Show full text]