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Human Reproductive System

Extracts from this document...

Introduction

The Human Reproductive System Structures of the male reproductive system Bulb of penis The bulb of penis is the expanded posterior part of the corpus spongiosum of the penis. It lies in the interval between the crura of the penis. It contains slightly dilated and angulated portion of the urethra. Bulbourethral (Cowper's) gland The bulbourethral gland is pea-sized structures located on the sides of the urethra below the prostate gland. It produces a clear, slippery fluid that empties directly into the urethra. These fluids lubricate the urethra and neutralises any acidity that may be present due to residual drops of urine in the urethra. Corona The corona is a rounded projecting border that forms the circumference of the base of the glans. It is located behind the penis and overhangs a deep retroglancular sulcus Corpora cavernosum penis The corpus cavernosum penis is one of the pair of sponge-like regions of erectile tissue in the penis. It contains irregular spaces which are filled with blood during erection. These spaces are lined by endothelium and separated by connective tissue septa. Corpus spongiosum penis The corpus spongiosum penis is the median column of erectile tissue located between and ventral to the two corpora cavernosa penis. Posteriorly It expands into the bulb of penis and terminates as enlarged glans penis anteriorly. Ductus (vas) deferens The ductus deferens is a long muscular tube that travels from the epididymis into the pelvic cavity to just behind the bladder. It transports mature sperm to the urethra in preparation for ejaculation. Ejaculatory duct Ejaculatory duct is formed by the fusion of vas deferens and the seminal vesicles. They open into the urethra and mix sperm stored in the ampulla with fluids secreted by the seminal vesicles and transport these to the prostate. Epididymis The epididymis is a long, coiled tube that rests on the backside of each testicle. It transports and store sperm cells that are produced in the testes. ...read more.

Middle

* The corpus luteum secretes oestrogen and progesterone. Progesterone prepares the uterus for the implantation of the fertilized egg. * If coitus has taken place and conception occurs, the fertilised egg will travel through the fallopian tube to implant in the uterus. This event results in the female to be pregnant. * The egg passes through the uterus if not fertilised. This results in the lining of the uterus to break down and shed as it is not needed to support pregnancy. The next menstrual period then begins. Follicle stimulating hormone (FSH) is produced and secreted by gonadotropes in the anterior lobe of the pituitary glands. It regulates the development, growth, pubertal maturation and reproductive processes in males and females. It acts alongside with LH in reproduction. In females, FSH stimulates the growth and maturation of immature Graafian follicles. As the follicles grow, it releases inhibin which blocks the production of FSH. FSH levels fall in late follicular phase which is critical in selecting only the most advanced follicle to proceed to ovulation. It then slightly rises at the end of the luteal phase which is necessary to start the next ovulatory cycle. In males, FSH increases the production of androgen binding protein by the sertoli cell present in the testes which is necessary for spermatogenesis. Oestrogen is a family of complex hormones with similar characteristics. FSH stimulates the ovarian follicles to secrete oestrogen. LH stimulates the Graafian follicle to secret corpus luteum, which is an empty graafian follicle after ovulation transformed into a yellow body filled with cells containing yellow substance that in turn secretes oestrogen. Day 0-14 in the menstrual cycle is referred to as oestrogen phase. Oestrogen is also produced in smaller amounts by other organs such as liver, adrenal glands and breasts. These secondary sources are especially important in postmenopausal females. Oestrogen maintains the endometrium of the uterine wall during menstrual cycle. ...read more.

Conclusion

(b) Answer each question below in one sentence only. (i) What do you mean by a dominant follicle? Graafian follicle. (ii) What are gonadotropes? Gonadotropes are cells in the anterior pituitary gland, which produce the gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH). (iii) Where does FSH come from and what is its main effect on the ovary? FSH is synthesised and secreted by gonadotropes in the anterior pituitary gland and it stimulates the growth of immature Graafian follicles to maturation in the ovary. (iv) Where does LH come from and what is its main effect in the middle of a cycle? LH is synthesised and secreted by gonadotropes in the anterior pituitary gland and it triggers ovulation in the middle of a cycle. (v) Where does oestrogen come from and what does it do to the lining of the uterus in the menstrual cycle? The ovarian follicles in the ovary secrete oestrogen and it stimulates the growth of the lining of the uterus. (vi) Where in the ovary does progesterone come from and what does it do to the lining of the uterus? Progesterone is secreted by the corpus luteum in the ovary and it converts the lining of the uterus to its secretory stage to prepare the uterus for implantation. (vii) What happens when progesterone secretion stops at the end of a menstrual cycle? When progesterone secretion stops at the end of a menstrual cycle the lining of the uterus breaks down and menstrual bleeding occurs. (viii) State not less than 4 secondary sexual characteristics in the female caused by oestrogen. * Enlargement of breasts * Growth of body hair, including underarm and pubic hair * Vaginal and uterine growth * Widening of hips (ix) State not less than 4 secondary sexual characteristics in the male caused by testosterone. * Growth of facial hair * Enlargement of larynx and deepening of voice * Heavier skull and bone structure * Increased muscle mass and strength (x) What are "androgens"? Androgens are steroid hormones such as testosterone or androsterone that controls the development and maintenance of masculine characteristics. ...read more.

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There is a great deal of detail and information in this work, mostly presented in a very concise form. The topic is huge and the title would be better if focused on particular aspects of human reproduction. The first section which a just a list of parts with no accompanying diagrams is not terribly helpful. The structure could be improved by including all the information on a particular topic together.

Marked by teacher Adam Roberts 05/09/2013

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