Urinogenital System in Frog 1.pptx

Animal Physiology

1. Dr. G.D. Hande Urinogenital System in Frog

2. In vertebrates,  the organs concerned with reproduction and urinary excretion . The major structures of the reproductive system in males are the testes, sperm ducts, urethra, and penis; in females, they are the ovaries, fallopian tubes, uterus, and vagina. The urogenital system is  responsible for the formation, storage and elimination of urine and for reproductive activity . Many functions of the urogenital system are controlled by autonomic (parasympathetic and sympathetic) and somatic efferent pathways originating in the lumbosacral spinal cord.

3. The urinary and reproductive systems  are associated closely in frogs and are jointly referred to as the Urogenital system. It is primarily involved in assisting the frog in carrying out urine excretion and reproduction. The main excretory product of frogs is urea and hence frogs are ureotelic animals.

4. The urinogenital organs can be studied under the following heads: 1. Excretory System: The excretory system in both male and female frog is similar. The excretion is mainly carried out with the help of a pair of kidneys, a pair of ureters, a urinary bladder and cloaca . The term urogenital refers to something that has both urinary and genital origins. The word urogenital is used  because the urinary and reproductive systems in males merge .

5. Kidneys: Both the kidneys are elongated, compact, flattened and dark red in colour . These are found in the lymph spaces ( subvertebral lymph sinus) above the coelom attached on either side of vertebral column. In tadpole the kidneys are pronephros , whereas in adult these are mesonephros . These are covered ventrally by peritoneum.                                             

6. (ii) Ureters: From the outer smooth convex posterior side of each kidney arises a mesonephric or Wolffian duct or ureter which passes backwards to open into dorsal side of the cloaca . The openings of the ureters are placed over a separate papilla on the dorsal side of cloaca . In male frog the ureters dilate just posterior to the kidney to form a vesicula seminalis in which sperms are stored .

7. In male frog the ureters convey the sperms and urine, and, hence, are called urinogenital ducts. The ventral surface of each kidney has a yellow coloured adrenal or supra renal gland of endocrine function. To the anterior of each kidney are attached numerous finger-like fat bodies, a testis in male and ovary in female. Fat bodies are reserves for nourishment.

8. (iii) Urinary Bladder: It is large, thin-walled bilobed distensible structure. It also opens into the ventral wall of cloaca by a sphinctered aperture. Its aperture lies below and opposite to the openings of ureters. The inner surface of bladder is lined with a layer of epithelium about three cells thick. The middle layer of the bladder consists of a network of smooth muscle fibres and outside this layer is a thin sheet of connective tissue covered externally by the peritoneum .

9. (iv) Cloaca : It is a small, medium sac receiving the anus, urinogenital apertures and the opening of urinary bladder. Cloaca opens outside by a cloacal aperture placed at the posterior end of the body between the two hindlimbs .                                                                                       

10. Histology of Kidney: The kidneys are most of the red blood corpuscles. Each kidney is composed of a number of (about 2000) twisted renal or uriniferous tubules held together by connective tissue and richly supplied with blood vessels and their capillaries. Each renal or uriniferous tubule starts as a thin, double-walled ciliated cup, the Bowman’s capsule enclosing a bunch of blood capillaries, the glomerulus which receives blood from an afferent arteriole of the renal artery.

11. Uriniferous tubules are the functional units of kidney. These are lined with a glandular and at places with ciliated epithelium. From the glomerulus blood is collected by efferent arteriole which joins with a renal vein. The tubule gets the blood supply from the capillaries of efferent arteriole and renal portal vein. The Bowman’s capsule along with its glomerulus is called Malpighian body or corpuscle tubules.

12. Each tubule opens into the collecting tubule which runs transversely across the kidney towards the dorsal surface. In turn all the transverse collecting tubules open into a longitudinal Bidder’s canal lying towards the inner margin of kidney and towards outer margin into the ureter . Ventral ciliated funnel-shaped nephrostomes . They carry wastes from the coelom into renal veins in frog or in uriniferous tubules in tadpoles.

13. Physiology of Excretion: Due to continuous catabolic activities certain substances are formed which are harmful to body, hence, their elimination is very essential which is done by the kidneys. The blood brings these substances into the kidneys through the renal portal veins. Blood comes to glomeruli from afferent arterioles which have a wider lumen then the capillaries so that the blood in glomeruli is under high pressure which causes filtration of blood.

14. The glomerular filtrate does not contain corpuscles nor plasma proteins, it has plasma, wastes and crystalloids consisting of urea, inorganic salts, glucose and large quantities of water. The glomerular filtrate passes through the thin wall of the Bowman’s capsules into the lumen of uriniferous tubules and the filtered blood goes into renal vein through the efferent arteriole.

15. Female Urinogenital System: The excretory organs are the same in female frog as found in male frog, but they do not have any connection with the reproductive organs. The ureter does not dilate as vesicula seminalis and no ducts from ovaries open into the kidneys. The cloaca serves as a common passage for urinary and genital systems as in the male frog.

16. Urinogenital system of Frog – Male The structures of the urogenital system of frogs in males are: Kidney Urinary bladder Ureter Testis Bidders canal Vasa efferentia Cloaca

17. Kidney  – Kidneys are dark red and bean like structures, compact, occurring in a pair located posteriorly in the body cavity on both sides of the vertebral column. Each kidney consists of many functional and structural units – nephrons or uriniferous tubules. Urinary Bladder –  it is a thin walled structure present ventral to the rectum. It stores urine. Ureter   – the ureter or the urinogenital duct occur in pairs, projects from the kidney in the form of ureters in males. Testis –  These structures occur in a pair and are yellowish in appearance. These ovoid structures are located in the upper section of the kidneys by a double fold of the peritoneum known as mesorchium .

18. Bidder’s canal –  It is a canal into which the vasa efferentia opens into the kidneys. Eventually this canal meets the ureter . This structure is responsible for passing urine, ova, water and sperm. Vasa efferentia  – It emerges from the testis and are 10-12 in number. They pass through mesorchium and move into the kidneys. Cloaca –  It is a small chamber mediating to pass urine, faeces and sperms to the outside. The ureter and urinary bladder opens into the cloaca .

19. Urinogenital system of Frog – Female The structures of the urogenital system of frogs in females are : Kidney Urinary bladder Ureter Ovaries Oviduct Cloaca

20. The common structures in both male and female urogenital systems in frogs are kidneys, ureters and urinary bladder, their functionalities remain the same. Ovary –  It is a paired structure present close to kidneys. These yellow-colored structures are present on the outer side of the kidneys by a fold of peritoneum known as the mesovarium . Through the process of oogenesis , they produce ova. A mature female releases close to 2500-3000 ova at once. Oviduct –  These structures are paired and found on each side of the ovary. They are thin, large and coiled structures appearing white in color. These ducts open separately into the cloaca .

21. How is the blood supply to the Kidneys? Blood supply to the kidneys is through the renal portal veins and renal arteries. Majorly blood constitutes urea as the excretory product. The renal artery branches in the kidney and redivides forming the afferent arteriole having a diameter larger than the efferent branch. The renal veins on the other side carries away the detoxified blood from the kidneys. The renal portal veins branch into the kidney and these branches and the efferent arteriole unites forming a mesh of capillaries near the uriniferous tubules and ultimately together they form the renal venule .