The Reproductive System

Similarities and differences between males and females, but same goal: new life Primary sex organs: gonads Testes in males Ovaries in females These produce the gametes (sex cells) Sperm in males Ovum (egg) in females Endocrine function also: secretion of hormones Accessory sex organs Internal glands and ducts External genitalia

Male reproductive system Testes (singular testis) or testicles: the gonads In embryo, first develop in posterior abdominal wall, then migrate Internal body temp too hot for viable sperm Temp cooler in the scrotum because of superficial position

Spermatogenesis: sperm formation in the testes Cross section of seminiferous tubule Begins at puberty 400 million sperm/day For baby not to end up with twice as many chromosomes as the parents, the sperm (as well as the egg) needs to have only half (1n) the # of chromosomes (1 of each of the 23) (2n means 2 of each chromosome, one from each parent, totaling 23 pairs = 46 chromosomes) Three stages: Formation of spermatocytes Meiosis Spermiogenesis

Sperm can swim only after they have left the testis Process of spermatogenesis is controlled by two hormones FSH (follicle stimulating hormones) from anterior pituitary Testosterone primary male hormone produces by testes *

Sperm are ejaculated from the epididymus Not directly from the testes Vas deferens* (or ductus deferens) 45cm (18”) Stores and transports sperm during ejaculation Runs superiorly from scrotum within spermatic cord, through inguinal canal and enters pelvis *

The Prostate Size & shape of a chestnut Encircles 1st part of urethra Contribute to semen (milky fluid and enzymes) PSA measured as indicator of prostate cancer (“prostate specific antigen”) Prevents urine and sperm from travelling at the same time!

The Female Reproductive System Production of gametes (ova, or eggs) Preparation for support of developing embryo during pregnancy Cyclic changes: menstrual cycle Averages 28 days Complex interplay between hormones and organs: at level of brain, ovaries and uterus

Gonads: the ovaries Paired, almond-shaped, flanking the uterus in lateral wall of true pelvis 3 x 1.5 x 1 cm in size Posterior view

Anterior view

Structure of ovary Outer cortex houses developing gametes the oocytes, within follicles

The Ovarian Cycle Follicular phase 1st approx 14 days but variable Egg develops in a follicle Stimulated by follicle stimulating hormone Estrogen produced Ovulation Egg released from follicle (leutinizing hormone surge) Egg in abdominal cavity Picked up by fallopian tube Luteal phase Post-ovulatory phase 14 days Produces progesterone as well as estrogen Progesterone stimulates uterus to be ready for baby If no pregnancy, corpus luteum degenerates and you have menstruation

Ovulation Signal for ovulation is Lutenizing hormone surge Ovarian wall ruptures and egg released,

Oogenesis Generation of eggs Look at the diagram Notice how meiosis makes eggs Notice how the egg develops in the ovary

Fallopian (uterine) tubes, AKA oviducts Fimbriae (fingers) pick up egg Beating cilia and muscular peristalsis propel egg to uterus ____Fallopian tubes__ Fimbriae * Enlargement of mucosa layer showing ciliated columnar epithelium Cross section through entire tube PID

The Uterus (womb) In pelvis anterior to rectum and posterosuperior to bladder Hollow, thick-walled organ Receives Retains Nourishes fertilized egg=embryo Uterus is pear-shaped (before babies)

The Uterine Wall* Three basic layers Perimetrium: outer serous membrane Myometrium: middle muscle Endometrium: inner mucosal lining *

Pituitary hormones * Ovarian hormones Time: one cycle (approx 28 d.) Pituitary hormones FSH: follicle stimulating hormone LH: luteinizing hormone Ovarian hormones Estrogen Progesterone ovulation * Follicular phase Luteal phase

(inhibin: inhibits pituitary secretion of FSH)

Mammary glands (breasts) Modified sweat glands Both sexes but function (normally) only in lactating female Produce milk to nourish baby

Conception After ejaculation into the vagina, sperm swim to meet an egg Sperm live 5-7 days (need cervical mucus) Eggs live about 12-24 hours, so conception only occurs during this short window Fertilization occurs in the fallopian tube Fertilization occurs at the moment the chromosomes from the male and female gametes unite

Initial days Cleavage (cell division) Blastocyst stage by day 4: now in uterus

Implantation 6-9 days post conception - burrows into endometrium Blastocyst floats for 2 days: “hatches” by digesting zona enough to squeeze out 6-9 days post conception - burrows into endometrium

The “Placental Barrier” Sugars, fats and oxygen diffuse from mother’s blood to fetus Urea and CO2 diffuse from fetus to mother Maternal antibodies actively transported across placenta Some resistance to disease (passive immunity) Most bacteria are blocked Many viruses can pass including rubella, chickenpox, mono, sometimes HIV Many drugs and toxins pass including alcohol, heroin, mercury Placental secretion of hormones Progesterone and HCG (human chorionic gonadotropin, the hormone tested for pregnancy): maintain the uterus Estrogens and CRH (corticotropin releasing hormone): promote labor