D3.1 Reproduction HL

Puberty hormones

• GnRH released by hypothalmaus to pituitroy which stimulates LH and FSH which act on gonands

• This happens during early teens

• Causes production of stereoids including oestradiol progestorne and testostroene

Changes during puberty

Girls:

• brests grow

• menstraul cycle begins

• acne

• pubic hair

• widening hips

Boys

• pubic hair

• acne

• growth of penis

• erections begin

• voice becomes deeper

Explain spermatogenesis

In seminifurous tubules

1. spermagonium undergies mitosis → primary speramocyte

2. primary spermaocyte undergoes meiosis 1 → two secondary spermaocytes

3. Two secondary spermaocytes undergo meiosis II → 4 spermatids

4. Spermatids differentiate with the help of sertolic cells (spermiogenesis) forming spermatozoa

Process of oogenesis

1. In fetal developemnt oogonium undergoes mitosis forming primary oocyte

2. primary occyte undergoes meiosis I but stops at anaphase and continues at puberty

3. Meiosis I produced secondary occyte and first polar body

4. Meiosis II only occurs after fertilziation forming a fertilzied egg and a second polar body

Spermatogenesis vs Oogenesis

Spermatogenesis:

• 4 spermatids

• begins at puberty ongoing

• everyday

• no polar bodies

• motile

• minimal cytoplams and organelles

Oogenesis

• one fertilized egg

• begins in fetus continues until menopause

• once a month

• forms polar bodies

• not motile

• contain cytoplams, organless and nutiernts

Preventing polyspermy

• after one spermatozon enters the egg cortical reaction begins

• cortical granules (vesicles) fuse with plamsa mebrane and release enzymes which make the zona pellucida impermable to anymore spermatozoa

Embryo developemnt

• ferilized egg moves down fallopian tubules dividing by mitosis

• when it reaches uterus it is a blastocyst

Blastocyst features:

• outer layer called throphoblast - helps form placenta, umbilical cord and embryonci membrane

• inner cell mass - gorups on interior which will beocme part of mebryo

• fluid filled cavity

Blastocyst will sink down into the endometrium lining → implantation

Pregnancy testing

• hCG is produced by trophoblast or placenta to maintain corpus lutheum so progestorone is secretd for highly vascular endometrium

• pregnancy test contain antibodies binded to an enzyme that changes colour

• If hCG is present it binds to the antibody and enzyme changes colour

Placenta

• exchange of nutrients and waste between fetus and mother

• Umbilical cord: Three vessels - two take fetal blood with waste while the other brings oxygenated nutrient rich blood from mtoher

• Placental villi- increases surface area for exchange

• placenta - only in mammals

Porgestorne in childbirth and pregnacy

• secretd first by corpus lutheum then placenta

• mainatins linign

• when decraesed secetion - indicates childrbith time

Positive feedback in childbirth

• decreased progestorne → relase of oxytocin from hypothalmus and secretd by pituitaoty

• Oxyoticn receptors in uterus signal first contraction

• Forst contraction signals for more oxytocin release

• Only positive feedback will stop when birth occurs

Hormone replcament therapy

WHen menopause occurs ovaries stop producing oestradiol and progesterone - can cause trouble sleeping, hot flushes

Some women take hromone replacemnt therapy → oestradiol

AT first they fought HRT leads to lower risk of CHD then to higher and now they say there is no correlation