GAMATOGENESIS- production of gamates
SPERMATOGENESIS-processing sperm, occurs in testes
OOGENESIS-producing ova, occurs in ovaries
HUMAN MALE REPRODUCTIVE SYSTEM
-sperm are produced in the SEMINIFEROUS TUBULE in the testes
-mature in the EPIDIDYMIS
-seminiferous tubule are packed with cells undergoing spermatogenesis
-SERTOLI CELLS found in the seminifurous tubule support, nourish and regulate spermatogenesis
-when male become sexually aroused , sperm form the the epididymis will enter ejaculatory duct
-through VAS DEFERENS and the released through urethra in the semen
-SEMEN is thick fluid containing sperm
-secretion from seminal vesicles , prostate gland , bulbourethral gland
-seminal vesicle secrete fluid containing nutrients for the sperm and prostaglandins which stimulate smooth muscle contractions along the male and female reproductive tracts
-PROSTATE GLAND secretes an alkaline fluid which activates or increase the motility of sperm
-the fluid also contain an antibiotic called SEMINALPLASMIN which prevents urinary tract infections
-BULBOURETHAL GLAND ( LOWER PROSTATE ) , produce mucus secretions which has a lubricating effect and cleanses the urethra of acidic residues of urine
pathway -epididymis - vas deferens - urethra - penis
SPERMATOGENESIS IN HUMAN MALE
-initially primordial germ cells in the embryonic testes undergo mitosis and differentiate into stem cells
-stem cells then divide through mitosis to form spermatogonia
-spermatogonia then undergoes mitosis to produce many diploid spermatogonia
-spermatogonia grow and enlarge into diploid primary spermatocytes
-the primary spermatocyte undergo meiosis 1 to form two haploid secondary spermatocytes with 23 chromosomes each
then the secondary spermatocytes undergoes meiosis 2 to produce 4 haploids spermatids
-spermatids then differentiate into haploid sperms
STRUCTURE OF SPERM
-head contains a nucleus with a membranous sac above it called the acrosome
-acrosome contains hydrolytic enzymes which breaks down the outer layers surrounding an egg during fertilisation
-it takes 2 hrs for sperm to reach ovum with the help of contractions of the female uterus
HUMAN FEMALE REPRODUCTIVE SYSTEM
-OVARIES produce one secondary oocyte each month alternately
-also produce oesteogen and progesterone during the ovarian cycle
-during ovulation, SECONDARY OOCYTE is released from an ovary and is swept into the fallopion tube by the action of the fimbriae
-if fertilisation occurs, it takes place in the fallopian tube
-the fertilised zygote is then propelled towards the uterus by the beating of the cilia and the muscle contractions of the fallopian tube walls
-uterus is a thick walled muscular organ and its narrow end is called cervix
-bacteria which live in the vagina create an acidic medium and protects against pathogenic bacteria
OOGENESIS
-oogenesis continues when the female become sexually mature
-at puberty , FSH stimulate a group of follicle to continue growth and development
-usually only one follicle matures fully when it completes meiosis 1 to form two cells with 23 chromosomes, one cell is called secondary oocyte and the other is called first polar body
-secondary oocyte is larger and receive almost all the cytoplasm
-the first polar body may disintegrate or may divide again to form two haploid second polar bodies
-the secondary oocyte begins meiosis 2 but stop at metaphase 2
-during ovulation , the secondary oocyte leaves the ovary and enters the fallopian tube where sperms may be present
-if no sperm are present , the secondary oocyte eventually disintegrates without completing meiosis
FERTILISATION
-fusion of haploid nucleus of sperm and haploid nucleus of ovum to form zygote
-ovum remain fertile for 24 hours while sperm remain for few days
-fertilisation only possible when intercourse take place on the day or few days before ovulation
-if the female has regular 28 days menstrual cycle and copulation takes place on the day of 12 to 16
-fertilisation is mostly like to occur
-once sperm enter the uterus , uterine contraction will help to transport them
-sperm are mobile due to presence of tail
-secretion of the female reproduction system not only provide a moist environment
-also bring about changes to sperm motility
-sperm can only fertilise the egg if they undergo these changes
-this process is called CAPACITATION
-in humans, capacitaiton occur the first six hours after sperms enter the reproductive tract
FERTILISATION PROCESS
1. acrosome of the sperm releases enzyme that digest a path through the follicle cells
2. after capacitation , sperm are able to swim more vigorously and release chemicals to penetrate the oocyte
3. contact of sperm with the zona pellucida ( thick transparent jelly layer of an oocyte ) triggers the acrosome reaction
4. acrosomal enzyme digest the zona pellucida and the sperm reaches the surface of the secondary oocyte
5. the sperm head fuses with the microvilli of the secondary oocyte and penetrates the cytoplasm
6. crotical granules in the egg@ lysosomes immediately releases enzyme as soon as the sperm has penetrated
7. the enzyme cause the zona pellucida to thicken and herden forming a fertilisation membrane
8. after the sperm enters the cytoplasm of the secondary oocyte , meiosis 2 resume and ovum and second polar body is formed , the second polar body degenerates immediately
9. sperm nucleus and ovum nucleus swells to form a pronucleus
10. both this nuclei fuse to form zygote
11. this process takes about 4 to 6 hrs
During ovulation, the oestrogen level is high and the cervical mucus is thin which permits the sperms to swim easily up the female reproductive tract
Progesterone level rises and the cervical mucus become think and sticky . This block the entry of sperm as well as bacteria
IMPLANTATION
1. after several days , zygote moves into the uterus as it divides into a hollow fluid filled ball called blastula
2. when it makes contact with the wall of the uterus , the blastula becomes blastocyt
3. cells that form on outer layer of the blastocyst are called trophoblast cells
4. trophoblast cells enable the blastocyst to invade the endometrium by producing proteolytic enzyme that can dissolve tissue
5. this allows the blastocyst burrow deep into the endometrial wall to receive nourishment from the endometrial gland
6. the blastocyst becomes firmly embedded among the glands and blood vessels lining the uterus
7. the trophoblast now called the chorion continues to develop a blood circulation and expand together with the maternal blood vessels to form the placenta
8. the implanted blastocyst develops into a foetus and secretes HUMAN CHORIONIC GONADOTROPIN which prevents the autolysis ofcorpus luteum
9. hence the secretion of progesterone and oestrogen from the corpus luteum continue for the first few months of pregnancy
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