I tomorrow quis test on topic of reproduction in humans fully
My class is 12 th
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BSE Class 12 Biology Revision Notes Chapter 3 Human Reproduction
Humans are sexually reproducing and viviparous. The reproductive events in humans include formation of gametes (gametogenesis), i.e., sperms in males and ovum in females, transfer of sperms into the female genital tract (insemination) and fusion of male and female gametes (fertilisation) leading to formation of zygote. This is followed by formation and development of blastocyst and its attachment to the uterine wall (implantation), embryonic development (gestation) and delivery of the baby (parturition)
The Male Reproductive System: It cChapteronsists of:
a) Primary sex organs i.e. a pair of testes suspended in a scrotum.
b) Secondary sex organs i.e. a pair of ducts each differentiated into rete testis, vasa efferentia, epididymis and vas deferens, ejaculatory duct and the associated glands
c) External genitalia
The testes are situated outside the abdominal cavity in a pouch called scrotum, which help in maintaining the low temperature of testes necessary for spermatogenesis.
Each testes has about 250 testicular lobules and each lobule contain highly coiled seminiferous tubules in which sperms are produced. Each seminiferous tubules is lined by two types of cells, spermatogonia ( male germ cell) and Sertoli cells.
Leydig cells or interstitial cells present around the seminiferous tubules synthesize and secrete androgen hormone.
Human Reproduction Class 12 Notes Biology
Ejaculatory duct store and transport the sperm from testes to outside through urethra which originate from urinary bladder and extend through penis to its external opening urethral meatus.
The penis is male external genitalia. The enlarged end of penis is called the glans penis is covered by a loose fold of skin called foreskin.
Male accessary glands include paired seminal vesicles, prostrate and paired bulbourethral glands. Secretion of these glands forms the seminal plasma which contains fructose, calcium and enzymes. The secretion of bulbourethral glands also helps in lubrication of the penis.
The Female Reproductive System: It consists of :
a)The primary sex organ that is a pair of ovaries
b)Secondary sex organs- the duct system consisting of a pair of fallopian tube , a uterus , cervix and vagina
c)External genitalia
d)Mammary glands
Ovaries are primary female sex organ that produce the female gamete and several steroid hormones. Each ovary is covered by thin epithelium which encloses the ovarian stroma, which is divided into a peripheral cortex and an inner medulla.
Fallopian tube extends from periphery of ovary to the uterus. The part closer to ovary is a funnel shaped structure called infundibulum having finger like projection called fimbriae.
Infundibulum leads to ampulla and join with uterus with isthmus. Uterus is pear shaped structure also called womb.
Uterus open vagina through a narrow cervix. The cavity of cervix (cervical canal) along with vagina forms the birth canal.
The wall of uterus has three layers of tissue:Human Reproduction Class 12 Notes Biology
I. Perimetrium- external membrane.
II. Myometrium – middle thick layer of smooth muscles which exhibit strong contraction during delivery of baby.
III. Endometrium – line the uterine wall and undergo cyclic changes during menstrual cycle.
Female external genitalia includes
Mons pubis – cushion of fatty tissues covered by skin and pubic hair.
Labia majora- fleshy fold that surround the vaginal opening.
Labia manora – paired fold of tissue under labia majora.
The opening of vagina is often partially covered by a membrane called hymen. The tiny finger like projection present at the upper junction of two labia manora above the urethral opening is called clitoris.
Mammary glands are paired structures that contain glandular tissues and variable fats. Each glandular tissue contains 15-20 mammary lobes containing alveoli that secrete milk. Mammary ducts join to form mammary ampulla.
Gametogenesis: The process of formation of male and female gametes in testes and ovary respectively is called gametogenesis.It is of two types:
1. Spermatogenesis in males
2. Oogenesis in females
Spermatogenesis- in testes immature, male germ cells (spermatogonia) produce sperm by spermatogenesis that begin at puberty.
The spermatogonia present at the inner side of seminiferous tubules multiply by mitotic division and increase in number. Each spematogonium contain 46 chromosomes.
Spermatogonia forms spermatocyte that undergo meiotic division to reproduce secondary spermatocytes having 23 chromosomes.
The spermatids are transformed into spermatozoa by the process called spermiogenesis. The sperm heads remain embedded in sertoli cells and are released from seminiferous tubules by the process of spermiation.