UNIT 9 NOTES REPRODUCTIVE SYSTEM Why sexual reproduction? o continuity of the species o genetic variation

§ Gametes (egg or sperm) are produced in the primary sex organs or gonads (ovaries or testes) § Male and female parts originate from same tissues and same area of the abdomen

MALE REPRODUCTIVE SYSTEM

-scrotum = sac that testes are suspended in

• lined with smooth muscle to lift and drop testes • lifts to keep warm • drop, and lined with many sweat glands, to keep cool

-testes= male gonads containing (~250 m) tightly coiled seminiferous tubules = where sperm are produced by meiosis (spermatogenesis)

• have interstitial cells found between the seminiferous tubules → produce and release testosterone before puberty, the tubules are solid cords →become hollow and start to function with puberty

-epididymis - tightly coiled tubules (~5-6m long) just outside the testes where sperm mature -vas deferens - tube takes sperm from epididymis to urethra (through penis) = sperm is stored in beginning -seminal vesicles - between bladder and rectum – joins vas deferens - releases fluid containing:

1) nutrients for the sperm 2) prostaglandins = triggers uterus contractions possibly to aid in sperm’s movement

-prostate gland - just below bladder

- adds an alkaline buffer to protect sperm against acidity of vagina

-Cowper’s gland or bulbourethral gland (just below prostate) • adds lubrication for sperm → better movement

- semen = seminal fluid + sperm (seminal fluid made by seminal vesicle, prostate gland, and Cowper’s gland) -urethra = carries both urine and semen (during ejaculation, the bladder is closed off so no urine comes out)

-penis= made up of spongy erectile tissue which fills with blood when excited = transfers sperm to female

• Main difference between male and female systems o Males release gametes during sexual activity while females release only during a monthly cycle

 

Spermatogenesis= production of mature sperm cells -happens almost continuously in seminiferous tubules of testes Testosterone -hormone produced mainly by interstitial cells of the testes -responsible for primary and secondary sex characteristics

PRIMARY SECONDARY Development of vas deferens and other ducts Deepening of voice

Maturation of external genitalia Distribution of hair Sperm production Muscle growth

Control of Testosterone

GnRH= (gonadotropic releasing hormone) “turns on” LH and FSH  LH= stimulates testosterone production by interstitial cells FSH=increases spermatogenesis by seminiferous tubules

These hormones work by negative feedback

Acrosome  =  contains  enzymes  to  help  penetrate  the  egg  Mitochondria  (spiral)  to  provide  energy  for  tail  movement  Tail  –  swim  Nucleus  –  transmit  genetic  information    

 

 

FEMALE REPRODUCTIVE SYSTEM 2 functions:

1. Produce and deliver the female gamete (ovum = egg) 2. Provide environment for the developing fetus

-Ovaries= female gonad containing FOLLICLES (with immature eggs) at various stages of maturation

-born with ~ 2 million immature follicles – only a few hundred ever mature OOGENESIS= maturation of 1 follicle per month - After OVULATION (releasing the mature egg) the empty follicle is called a CORPUS LUTEUM - Release female hormones (estrogen and progesterone)

-Oviducts= (Fallopian Tubes) = extend from ovary to uterus for embryo transport

-have fingerlike projections called FIMBRIA that sweep across the ovary and sweep egg in -tube is lined with cilia that create a current to carry the egg to uterus -egg is fertilized here if sperm are present

-Uterus=muscular pear-shaped organ -normally size of a fist but during pregnancy stretches to watermelon size Uterus has 3 layers:

1. Inner is spongy endometrium full of blood →expelled during menstruation

2. Middle is thick smooth muscle – used to deliver baby, expel endometrium, assist passage of sperm 3. Outer is connective tissue – holds organ in place

-Cervix= bottom of uterus

-usually closed except to release endometrium, deliver baby, let sperm in -acts as a barrier to microbes → many WBC’s nearby

-Vagina = small muscular tube

-lining is folded and capable of being stretched during intercourse and birth

-Clitoris= small organ in front of urethra (related to glans of penis) -highly sensitive → enlarges during sexual arousal -Labia= (folds) protects external genitalia Estrogen Functions:

Primary sex characteristics Secondary sex characteristics Vagina and uterus grow Body hair Egg maturation Widening of pelvis and hips Onset of uterine cycle Breast enlargement Milk production when pregnant Fat layer beneath the skin

 

 

MENSTRUAL CYCLE (varies from 20-40 days in length) -refers to changes in the uterus =UTERINE CYCLE -menstrual flow phase = menstrual bleeding (loss of endometrium)

~days 1-5 -proliferative phase= remaining endometrium regenerates and thickens

~days 6-13 -secretory phase = endometrium continues to thicken and becomes highly vascularized ~days15 – 28 -running at the same time is the OVARIAN CYCLE - follicular phase – several follicles being to grow (only 1 matures) ~ days 1-13 -ovulatory phase – ovary wall ruptures and follicle is released ~ ovulation ~day 14 -luteal phase – corpus luteum (empty follicle) secretes hormones ~ days 15-28

1. Gonadotropic releasing hormone (GnRH) – activates anterior pituitary to secrete FSH & LH 2. FSH – stimulates follicle development 3. Estrogen – from ovaries, tells pituitary to stop FSH because follicles are maturing 4. LH –causes release of ovum (egg) = OVULATION and formation of the corpus luteum 5. Estrogen – stops LH secretion and prevents FSH release (because preparing for a baby)

- Secreted from corpus luteum 6. Progesterone – causes build-up of endometrium to prepare for baby

-Secreted from corpus luteum 7. Corpus luteum deteriorates →levels of estrogen and progesterone decrease → endometrium is shed =

MENSTRUATION

   

 

FERTILIZATION AND PREGNANCY -if fertilization occurs in fallopian tube/oviduct - development begins immediately -several days later (~ 7 days) the embryo implants in uterine wall →during implantation cells surrounding embryo release a hormone →HCG = human chorionic gonadotropin that prevents degeneration of corpus luteum and stimulates it to produce progesterone HCG is present in urine when pregnant = pregnancy test

- Thought that some women react to /allergic to HCG = morning sickness -placenta forms and continues to produce HCG, estrogen and progesterone 9 does 2 things:

1. Shuts off pituitary so no FSH or LH 2. Maintains endometrium so corpus luteum no longer needed

èSo, no menstruation

µSometimes the corpus luteum activity may decrease, or not enough HCG present = decrease progesterone causes breakdown of endometrium and loss of embryo – maybe mistaken for an unusual period. Oxytocin Role in Pregnancy -oxytocin is a hormone produced by hypothalamus and stored in posterior pituitary -released in blood upon nervous stimulation of hypothalamus -causes milk let-down by positive feedback – more the baby feeds→ more oxytocin →more milk produced -stimulates contractions of uterus during labour – positive feedback During labour: Increase estrogen $ Oxytocin receptors stimulated ← $

Oxytocin released $

Uterine contractions + feedback $ Fetus pushes on cervix