Evolution of Urinogenital Ducts.pptx

The urinary system includes the kidneys and the ducts that carry away their product, urine. The genital system includes the gonads and their ducts that carry away the products they form, sperm or eggs. Embryologically, urinary and reproductive organs arise from the same or
adjacent tissues and maintain close anatomical association
throughout the organism’s life.

1. Succession of Kidneys and Evolution of Urino -Genital Ducts Dr. Manju Bhaskar Assistant Professor Department of Zoology D. B. S. College Govind Nagar Kanpur Uttar Pradesh India

2. Kidneys are built in accordance with a basic pattern consist of Glomeruli Renal Tubule A Pair Longitudinal Duct

3. Larval fishes Earliest vertebrate kidneys probably extended the entire length of the body cavity and had external glomeruli that drained the coelomic fluid.

4. Basic Components of Craniate Kidney External Glomeruli : most primitive glomeruli are suspended in the coelom surrounded by coelomic fluid, which swept into peritoneal funnel, nephrostome . eg embryos and larvae. Internal Glomeruli : glomeruli in adults are embedded in the dorsal body wall and ensheathed by Bowman’s capsule, the capsular cavity collects the glomerular filtrate which passes into renal tubule.

5. Renal tubule originates from embryonic nephrogenic mesoderm, lies lateral to mesodermal somites and extends the length of embryonic trunk from behind the head to cloaca

6. Pronephros The earliest embryonic tubules arise from the cephalic end of nephrogenic mesoderm. Tubules are segmental, one pair at each segment. In anamniotes they have association with external glomerulus. No of pronephric tubules : 3 in larval frog, 7 in human embryos, 12 in chicks. The distal end of first several pronephric tubule unite end to end and establishes an opening into cloaca. This is pronephric duct.

7. Pronephric tubules are temporary, they loose their connection with dorsal aorta and regress. Pronephric duct does not regress. Although pronephric tubules develop in all craniates, they function only in embryonic ray finned fishes and in larval agnathans, dipnoans and amphibians . In amniote embryos they are vestigial or lost.

8. Mesonephros Pronephric duct act as inductor, additional tubules develop in nephrogenic mesoderm behind the pronephric region and establish an entrance into the existing pronephric duct. Fishes, amphibian and nonavian reptiles have open nephrostome that usually close later in development. Mesonephros become functional throughout life in fishes and amphibians . Functional embryonic kidney of amniotes .

9. Some of the anterior mesonephros tubules in male fishes and amphibians become utilized to transport sperm from the testis to mesonephric duct via substance of kidney. Mesonephric tubules are vasa efferentia . The region of adult male kidney is preempted for sperm transport and known as sexual kidney, coiled part of mesonephric duct is known as epididymis. Accessory urinary duct supplement or even replace mesonephric duct as carrier of urine.

10. During mesonephros establishment, when last mesonephric tubules formed, earliest tubules already regressed. 15.12 During the time of mesonephros functioning, a new kidney metanephros is organizing, when metanephros is able to function, mesonephros regresses.

11. Metanephros Metanephros organizes from the caudal end of nephrogenic mesoderm which becomes displaced cephalad and laterad during development. Differentiation of metanephric kidney commences when a hollow metanephric bud sprouts from the caudal end of the mesonephric duct. The hollow stalk connecting the metanephros with embryonic mesonephric duct becomes ureter . Urinary channels form within the kidney and open into common collecting tubules. Meanwhile ‘S’ shaped renal tubules grows and encapsulates glomerulus to form renal corpuscle and other end form collecting tubule. Renal pelvis collects urine from common collecting tubules.

12. Mesonephric duct Female : Gartner’s duct Male : Vas deferens Muellerian duct Female : Reproductive tract Male : Portions are retained

13. Reproductive Organs The reproductive system includes the gonads, their products, hormones and gametes, and the ducts that transport gametes. Gonads have two major functions : Produce gametes Synthesize steroidal hormones Hormones requires for differentiation, growth and maintenance of accessory sex organs (reproductive ducts and their glands), secondary sex characteristics.

14. Gonads arise as genital ridge Thickening in the splanchnic mesoderm Indifferent gonad Gonads of both sex contain germ cells (sperm or ova) In females germ cells resides in cortex In males germ cells resides in medulla

15. Testes and Male Genital Ducts Germinal epithelium lines the seminiferous tubules where sperms are formed. Vasa efferentia are mesonephric tubules which conduct sperm to spermatic duct. In most craniates with mesonephric ducts carry both sperm and urine. Hagfishes, lampreys, some jawed fishes and urodeles lack seminiferous tubules. Germinal epithelium may be on the surface of the testis or deep within and primordial germ cells migrate into cyst like seminiferous ampullae . After breeding season cyst collapse.

16. In some fishes, a new sperm duct replace the mesonephric duct as a carrier of sperm, marginal canal . Other fishes, amphibians, reptiles to humans, the embryonic mesonephric duct remains in adult males to carry sperm known as vas deferens.

17. Female Genital Tract

18. Female genital tract consist of paired muscular and glandular oviducts that commence at an ostium, open to coelom, leads to neck to oviducal funnel. Oviducts end in cloaca or a subdivision of it. Any differences along the length of the tract are in the degree of regional specializations that support species specific functions such as collecting egg from coelom, coating them with protective or nutrient substances, temporarily housing eggs, embryos or larvae and maintaining them until the eggs are shed or young are delivered. In craniates other than ray finned fishes, the female duct system differentiates from a pair of embryonic Muellerian duct.

19. Cyclostomes ovary lack oviducts, eggs are shed into coelom From coelom ova reach to cloaca (lamprey) or anus (hagfish) through secondary pores In elasmobranchs ovaries are initially paired, but in some only one may develop

20. Muellerian duct develop in both, but do not perisist in males. The Muellerian duct of Elasmobranchs and Amphibians arise by longitudinal splitting of the pronephric duct and their ostia develop from one or several pronephric nephrostomes . In other craniates, each Muellerian duct arise as longitudinal groove in the coelomic epithelium parallel to mesonephric duct, which becomes tube like structure.

21. The Mullerian duct or oviduct has 4 regions Funnel : it collects eggs shed from the ovary, anterior end of paired oviducts may fuse into single funnel Shell gland : it stores sperm in most elasmobranchs, secretes albumen and mucus. In oviparous species, the shell gland produces the egg case as well. In viviparous species, may be indistinguishable. Isthmus : it connects shell gland to uterus. Uterus : Nutritionally supports embryos. Oviducts may join before they enter the cloaca, or they may enter separately. The genital ducts of chimaeras are similar to those of sharks, except the oviducts always share a common funnel and each oviduct opens separately into the cloaca.

22. The Muellerian duct of female sharks’s give rise to an oviduct that develops a shell gland and uterus

23. The lining of amphibian oviduct are richly supplied with glands that secrete several layers of protective jelly envelops around each egg as it moves down the tube. Female tract of reptiles and monotremes mammals conform closely to the basic pattern. only one of the two embryonic Muellerian duct may differentiate (crocodile and most birds). Albumen gland line part of the oviduct and usually a shell gland anterior to cloaca. Albumen secreting area in fowl is known as magnum, shell gland is a uterus and short glandular and muscular segment at the base of entrance to the cloaca is vagina

24. Therian mammals In other craniates , paired muellerian ducts in mammals give rise to female genital tract commencing with the ostium of the oviduct. Muellerian duct of eutherian mammals unite at their caudal ends to one degree or another. The tract of eutherian mammals consist of two oviducts, a uterus with or without horns ( cornu ) and a vagina. Oviducts are short and small in diameter ( microlecithal egg), more or less convulated . Oviducal funnel has a fringed border.

25. In some teleosts , such as salmonids, eggs released from the ovaries fill the body cavity. Eventually they reach short, funnel-like remnants of the oviducts situated at the posterior part of the coelom. However, in many teleosts , the oviducts regress entirely, leaving egg transport to new ovarian ducts Most teleost fishes lay eggs, but some bear live young. Among these viviparous teleosts , maternal tissues may nourish the embryo

26. Tetrapod Amphibian ovaries are paired, hollow structures that usually show a prominent cortex covered by germinal epithelium. The genital ducts of female amphibians are usually simple and consistent. The archinephric ducts serve the Opisthonephric kidneys; the oviducts (Müllerian ducts) serve the ovaries.

27. Amniotes In amniotes, remnants of the mesonephros may persist in larval stages, but adults have metanephric kidneys drained exclusively by new paired ducts, the ureters (metanephric ducts). In females, the archinephric ducts are rudimentary. The oviducts (Müllerian ducts) persist in their roles of transporting ova from the ovaries and supporting the embryo while it is in transit. The tubular oviducts (Müllerian ducts) of amniotes often have prominent sheets of smooth muscle within their walls and a lumen lined by a secretory mucosa. In oviparous amniotes, a shell gland may be prominent; in viviparous amniotes the uterus may be distinct

28. Uterus The uterus is the terminal portion of the oviduct. Shelled eggs waiting to be laid or embryos completing their development are held within the uterus. In eutherian mammals and a few other vertebrates, the walls of the uterus and extraembryonic membranes of the embryo establish a close vascular association through a placenta. Nutrients and oxygen are transported to the developing embryo, and carbon dioxide is given up to the maternal circulation via the placenta.

29. Uteri : Four types Duplex : The muellerian duct of marsupials are paired all the way to urino -genital sinus (subdivision of claoca ). Marsupials have two completely separate uteri and two vagina. Eg . Kangaroos Bipartite : a uterus with two horns may have totally separate passageways within the body of the uterus, but share a single cervix. Eg ruminants, cats horses. Bicornuate : the uteri of eutherian mammals exhibit varying degree of fusion distally (no partition in fused portion, middle to post. part fused) eg. Dogs, pigs, elephants, whale Simplex : maximum fusion occurs in muellerian duct, in which fusion commences at the ends of short oviduct and there are no uterine horns eg primates (human )

30. Bicornuate : the uteri of eutherian mammals exhibit varying degree of fusion distally (no partition in fused portion, middle to post. part fused) eg. Dogs, pigs, elephants, whale Simplex : maximum fusion occurs in muellerian duct, in which fusion commences at the ends of short oviduct and there are no uterine horns eg primates (human )

31. References Kenneth V. Kardong : Vertebrates : Comparative anatomy, Function, Evolution Vth edition, McGraw-Hill Primis

32. Thank You