HUMAN REPRODUCTION · Comparison Tables

1. Male vs Female Reproductive System

Organisation and principal roles
Feature	Male reproductive system	Female reproductive system
Primary sex organ	Pair of testes in the scrotum	Pair of ovaries in the pelvic cavity
Gamete produced	Sperm / spermatozoon	Ovum / secondary oocyte
Main ducts	Rete testis → vasa efferentia → epididymis → vas deferens → ejaculatory duct → urethra	Oviducts, uterus, cervix and vagina
Accessory glands / organs	Seminal vesicles, prostate and bulbourethral glands add seminal plasma	Uterus supports implantation and development; mammary glands nourish the newborn
Key hormones	Testosterone and inhibin from testes	Oestrogens, progesterone, inhibin and relaxin from ovaries / placenta

2. Spermatogenesis vs Oogenesis

Formation of male and female gametes
Point	Spermatogenesis	Oogenesis
Site	Seminiferous tubules of testes	Ovarian follicles
Begins	At puberty	During embryonic development
Stem cells	Spermatogonia (2n)	Oogonia (2n)
Meiosis I product	Two equal haploid secondary spermatocytes	Large secondary oocyte + small first polar body
Meiosis II product	Four spermatids that differentiate into spermatozoa	Completed only after sperm entry; ovum + second polar body
Cytokinesis	Equal	Unequal; cytoplasm is conserved in the ovum
Output per primary cell	Four functional sperm	One functional ovum

High-yieldSpermiogenesis converts spermatids into spermatozoa; spermiation releases spermatozoa from Sertoli cells into the lumen.

3. Sperm vs Ovum

Structure adapted to each gamete's role
Feature	Sperm	Ovum / secondary oocyte
Size and motility	Small, motile and flagellated	Large, non-motile, rich in cytoplasm
Main regions	Head, neck, middle piece and tail	Plasma membrane, zona pellucida and corona radiata
Special structures	Acrosome has enzymes for fertilisation; middle piece has mitochondria	Cortical reaction after sperm entry blocks polyspermy
Chromosomes	Haploid; carries X or Y chromosome	Haploid; always carries X chromosome
Contribution to zygote	Paternal genome and centriole	Maternal genome, cytoplasm and organelles

4. Ovarian Cycle vs Menstrual Cycle

Linked cyclic events in a 28-day cycle
Phase	Ovarian events	Uterine / menstrual events	Hormonal cue
Menstrual phase (day 1-5)	New follicles begin growth	Endometrium is shed if fertilisation did not occur	Fall in progesterone and oestrogen
Follicular / proliferative phase (day 6-13)	Follicles develop; one becomes dominant Graafian follicle	Endometrium regenerates and proliferates	FSH stimulates follicles; oestrogen rises
Ovulation (about day 14)	Secondary oocyte is released from Graafian follicle	Endometrium remains receptive	Mid-cycle LH surge
Luteal / secretory phase (day 15-28)	Ruptured follicle becomes corpus luteum	Endometrium becomes vascular and secretory	Progesterone predominates

5. Fertilisation, Implantation and Parturition

Major events from gamete fusion to birth
Event	Site / timing	Key outcome
Fertilisation	Ampullary-isthmic junction of oviduct	Haploid sperm and secondary oocyte fuse to form diploid zygote
Cleavage	During movement through oviduct	Zygote → 2, 4, 8, 16 blastomeres; 8-16 cell stage is morula
Blastocyst formation	Before uterine implantation	Outer trophoblast and inner cell mass differentiate
Implantation	Endometrium of uterus	Blastocyst embeds in uterine wall; pregnancy begins
Placenta	Maternal endometrium + embryonic chorionic villi	Exchange of nutrients, gases and wastes; endocrine support
Parturition	End of gestation	Foetal ejection reflex and oxytocin cause strong uterine contractions

Fertilisation→Morula→Blastocyst→Implantation→Placenta & foetus

6. Major Hormones in Human Reproduction

Source and action at a glance
Hormone	Main source	Core action
GnRH	Hypothalamus	Stimulates anterior pituitary release of FSH and LH
FSH	Anterior pituitary	Acts on Sertoli cells; stimulates follicular development in ovary
LH	Anterior pituitary	Acts on Leydig cells; triggers ovulation and corpus luteum formation
Testosterone	Leydig cells	Supports spermatogenesis and male secondary sexual characters
Oestrogens	Growing follicles / ovary	Female secondary sexual characters and endometrial proliferation
Progesterone	Corpus luteum; placenta	Maintains endometrium and supports pregnancy
hCG	Placenta	Maintains corpus luteum early in pregnancy; basis of pregnancy tests
Prolactin / oxytocin	Anterior / posterior pituitary	Milk synthesis / milk ejection and uterine contraction

7. Identical vs Fraternal Twins, and Lactation Terms

Frequently tested distinctions
Term	Origin / meaning	Key point
Identical twins	One zygote divides during early embryonic development	Genetically identical and usually same sex
Fraternal twins	Two ova are fertilised by two different sperm	Genetically as similar as ordinary siblings; may be different sexes
Lactogenesis	Milk production after parturition	Stimulated mainly by prolactin
Milk ejection	Release of milk from mammary glands	Infant suckling triggers oxytocin release
Colostrum	First milk after childbirth	Rich in antibodies, especially IgA, and important for newborn immunity