human reproduction

Question 1

list components of male reproductive system

Answer 1

1. pair of testes
2. accessory glands
3. accessory ducts
4. external genitalia

Question 2

explain structure of testes

Answer 2

• situated within a pouch called scrotum outside abdominal cavity
• each testis w dense covering has 250 compartments-testicular lobules
• each lobule contains 1-3 highly coiled seminiferous tubules in which sperms are produced
• each tubule is lined w spermatogonia and sertoli cells-male germ cells undergo meiotic divisions to produce sperm and sertoli cells provide nutrition
• regions outside tubules contain blood vessels and leydig/interstitial cells that synthesise and secrete androgens

Question 3

list accessory ducts

Answer 3

1. rete testis
2. vasa efferentia
3. epididymis
4. vas deferens

Question 4

list glands and their functions

Answer 4

1. paired seminal vesicles
2. prostate
3. bulbourethral-secretions help in lubrication of penis
   -> secretions of all glsnds constitute seminal plasma which is rich in fructose, calcium, and certain enzymes.

Question 5

EXPLAIN SPERMATOGENESIS

Answer 5

1. spermatogonia multiply by mitosis
2. some spermatogonia called primary spermatocytes undergo meiosis 1 and produces two haploid secondary spermatocytes
3. the secondary spermatocytes then undergo meiosis 2 and produce 4 haploid spermatids.
4. the spermatids are transofrmed into spermatozoa(sperms) by spermiogenesis
5. after spermiogenesis, their heads are embedded in sertoli cells until theyre released from seminiferous tubules by spermiation process.

Question 6

when and how is spermatogenesis initiated

Answer 6

1. hypothalamic homrone-gonadotrophin releasing hormone increases and acts at anteriror pituitary stimulatign secretion of LH and FSH
2. LH acts on leydig cells and stimulate synthesis and secretion
3. androgens which in turn stimulate spermatogenesis
4. FSH acts on sertoli cells and stimulates secretion of some factors which help in spermatogenesis

Question 7

oogenesis

Answer 7

1. foetal stage-7 million oogonia in each ovary
2. 5 months old-2 million oogonia
3. at birth, oogonia enter prophase-1 of meiosis-1 and get arrested at that stage as primary oocytes which then get surrounded by a layer of granulosa cells and is called primary follicle.
4. at puberty-60k-70k primary follicles, get surroudned by additional layers of granulosa cells and are called secondary follicles.
5. secondary follicles transform into tertiary follicles characterised by a fluid filled cavity called antrum.
6. at this stage, the primary oocyte i ntertiary follicle grows in size and completes meiosis 1 thus resulting in formation of secondary oocyte and first polar body.
7. tertiary follicle matures into graafian follicle and secondary oocyte forms a new layer zona pellucida around it.
8. ovulation-graafian follicle ruptures to release ovum(secondary oocyte).

Question 8

fertilisation

Answer 8

1. sperm comes in contact with zona pellucida and induces changes in the membrane that block entry of other sperms.
2. enters the cytoplasm thru zp and plasmamembrane and induces completion of meisois 2 resulting in formation of ootid(haploid ovum) and second polar body.
3. ootid and haploid sperm fuse to form zygote

Question 9

endocrine hormones of placenta

Answer 9

1. human chorionic gonadotropin
2. human placentalk lactogen
3. estrogens
4. progestogens
5. later phase- relaxin.

Question 9

implantation

Answer 9

1. ampulla-zygote
2. throughout isthmus-the zygote moves undergoing mitotic division called cleavage towards uterus and forms 2,4,8,16 daughter cells called blastomeres.
3. embryo with 8 to 16 blastomeres is morula.
4. morula continues to divide and transforms into blastocyst in which the blastomeres are arranged in an outer layer called trophoblast and inner cell mass attached to trophoblast.
5. trophoblast then gets attached to endometriuem and inner cell mass gets differentiated as embryo.
6. after attachment, the uterine cells rapidly divide and cover the blastocyst thus, the blastocyst becomes embedded in the enodmetrium of the uterus.

Question 10

why are production of other hormones increased several folds

Answer 10

increased production of these hormones is essential for supporting the fetal growth, metabolic changes in the mother, and maintenance of pregnancy.

Question 11

mammary gland

Answer 11

• paired structures containing glandular tissue and fat
• glandular tissue divided into 15-20 mammary lobes containing clusters of cells called alveoli in their lumens secreting milk
• alveoli open into mammary tubules
• tubules of each lobe join to form mammary ducts
• several mammary ducts join to form mammary ampulla which is connected to lactiferous duct.

Question 12

embryonic development

Answer 12

1. After one month-embryo heart is formed
2. By the end of second month, the foetus develops limbs and digits.
3. by the end of first trimester, most of the major organ systems are formed, limbs and external genital organs.
4. by fifth month, first movements of the foetus and appearance of hair on head.
5. by the end of second trimester, body is covered with fine hair, eyelids separate and eyelashes are formed.

Question 13

Parturition

Answer 13

• induced by a complex neuroendocrinemechanism
  1. the signals for parturition usually originate from the fully developed foetus and the placenta which induce mild uterine contractions called foetal ejection reflex.
  2. This triggers release of oxytocin from the maternal pitutitary.
  3. Oxytocine acts on the uterine muscle and causes stronger uterine contractiosn which in turns stimulates further secretion of oxytocin.
  4. the stimulatory reflex between the uterine contraction and oxytocin secretion continues resulting in stronger and stronger contractions.