March 24 Lecture - March 24, 2009 The Reproductive System...

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March 24, 2009 The Reproductive System Embryonic Development of the Reproductive System - Gender of individual is determined at the moment of conception - Sex of individual cannot be observed until several weeks later o The only way that it may be determined is by sampling some cells and doing a chromosome smear to look for XY or XX chromosome - It is not until the 6 th week of development that genitalia begins to take shape o Still undifferentiated, and cannot determine whether they are male or female - By the 7 th week, the genital tubercule has developed and forms a cylindrical shape known as the phallus o The phallus develops a bulb-like swelling at its end This is known as the glans o The genital ridges or labial-strobal swellings appear at the base of the phallus - It is not until about the 8 th week of development that there is some differentiation which begins to take place o If male The phallus elongates into the penis . The two genital ridges will fuse at the midline and give rise to the scrotum o If female The phallus undergoes a modification to form the clitoris The labial-scrotal swellings will retain their original position and form the labia majora of the adult female - At about 2 ½ to 3 months of age the differentiation between reproductive organs is evident The Male Reproductive System - Structures o Testes: Abreviation for testicle o Epididymus o Vas deferens (ductus deferens) Will join with the urethra o Accesory glands Seminal vesicles Prostate gland Ejaculatory duct Bulbourethral glands (Cowper’s glands) o In males, the urethra is shared between the urinary and reproductive system The Testes - Begins development early in embryonic life - Initially, they are located in the abdominal cavity and throughout the process of development they will undergo migration downward
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- At about the 8 th month of gestation, the testes descend through the inguinal canal and descend into the scrotum - In cases where the testes fail to descend o If both testes → cryptorchidism Results in infertility Not irreversibile if condition is recognized before puberty can be surgically corrected If procedure is delayed after puberty chances of maintaining fertility is low as the testes will begin to atrophy in the abdominal cavitiy - In the scrotum, the testes are kept at a temperature that is approximately 2-4 o C lower temperature to the body o This is believed to increase the vitality and motility of the sperm within the testes - The testes is covered by a thick membranous capsule known as the tunica albuginea - The interior of the testes reveals many individual lobes (approximately 200-400 lobes/compartments) o Each lobe contains 1-3 tightly coiled tubules, referred to as the seminiferous tubules In the seminiferous tubules , there are two different types of cells present Spermatogonial cells : cells which are involved in the production of spermatozoa (germ cells) Sustentacular cells : or cells of Sertoli
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This note was uploaded on 10/23/2011 for the course BIOL 2125 taught by Professor Dr.park during the Winter '02 term at A.T. Still University.

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March 24 Lecture - March 24, 2009 The Reproductive System...

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