The Reproductive System and Development Ch. 31,32,33

Organs of the male reproductive Introduction Testes –Structure –Spermatogenesis Formation of sperm

Spermatogenesis

Male internal accessory organs Epididymus –Coiled tube near testis Vas deferens –Muscular tube that empties into urethra. Seminal vesicle –Secretes fructose to nourish sperms –Prostaglandin to cause female reproductive system tubes to contract to help convey sperm to egg Prostate gland –Located at base of bladder –Alkaline fluid Bulbourethral glands –mucus Semen

Male external reproductive organs Scrotum –Holds testes away from body Penis –Conveys sperm into the female body

Hormonal control of male reproductive function Hypothalamic and pituitary hormones –Hypothalamus - Gonadotropin releasing hormone –Anterior pituitary – Luteinizing hormone Follicle stimulating hormone

Organs of the female reproductive system The organs produce /maintain egg cells, transport site of fertilization, and provide favorable environment for embryo Ovaries – primary gonads –Structure – solid, ovoid, lateral pelvic cavity –Medulla – connective tissue and blood vessels, nerves. –Cortex - follicles Primordial follicles – prenatal –Millions –Primary oocyte and follicular cells Oogenesis – oocytes begin meiosis, process halts and resumes at puberty Follicle maturation – at puberty, FSH – follicle maturation Ovulation – will be relased throughout a woman’s life. –If not fertilized, it will degerate.

Female internal accessory organs Uterine tubes – oviducts –Suspended by ligament –Lead to uterus Infundibulum – expanded section of uterine tube –Fimbrae – on margins Uterus – houses developing embryo Vagina – muscular tube –From uterus to outside –Path through which sperm and baby travel during birth

Female external reproductive organs Labia majora – enclose and protect other reproductive organs Labia minora-vascular Clitoris – anterior end of vulva Vestibule – glands secrete mucus

Hormonal control of female reproductive function Female sex hormones –From hypothalamus –Gonadotropic releasing hormone (secreted around 10 years of age) –Anterior pituitary hormones FSH – stimulates ovaries to secrete estrogen (Secondary sex characteristics – breast development, increased adipose tissue)and progesterone (triggers uterine changes during menstrual cycle.) LH – triggers ovulation

Hormones and the menstrual cycle

Female reproductive cycle Monthly changes in uterine lining – menstrual flow – shedding of the lining Fsh – starts menstrual cycle Lh – mid cycle surge in LH triggers ovulation More estrogen/progesterone secreted If pregnancy does not occur, uterine lining is shed Menopause – when cycles cease – middle age Cause – aging of the ovaries when follicles no longer mature

Mammary glands Accessory organs within the breast - Produce and secrete milk Location: Anterior thorax Infants nurse to cause the milk to let down into the ducts of the breast.

Birth Control Vasectomy/tubal ligation – considered permanent (can be reversed)

Other birth control Mechanical barrier –Condom, diaphragm, cervical cap Chemical barrier –Spermicides –More effective with mechanical barrier Oral contraceptives (birth control pills) –Contain estrogen Injectable contraception- intramuscular injection of Depo-Provera – suppress release of oocyte for 3 months. Contraceptive implants – progesterone containing capsules or rods inserted under skin – may work for 5 years Intrauterine devices – IUD. Solid object inserted into uterus – interferes with implantation.

Pregnancy Presence of developing offspring in uterus – result of fertilization Transport of Sex Cells –Upper one third of uterine tubes –Thin uterine secretions Fertilization –Sperm erode corona radiata and zona pellucida - one sperm cell penetrates egg membrane –Changes in egg membrane prevent additional sperm from entering –Result in a diploid zygote

Prenatal Period Early Embryonic Development –Undergo series of mitotic divisions called Cleavage –Dividing mass of cells - Morula –Blastocyst when implanted –Embryo – first 8 weeks of development –Fetus – after 8 weeks

Hormonal changes during pregnancy Human chorionic gonadotropin secreted during blastocyst stage –Maintains corpus luteum and uterine lining Aldosterone –Promotes fluid retention Parathyroid hormone –Maintains high calcium level

Embryonic Stage of Development Weeks 2-8 Placenta development Internal organ development Facial feature development

Week 2 Embryonic disk development –Germ layers Ectoderm - nervous system and sensory organs, epidermis, linings of mouth and anal canal Mesoderm - muscle, bone, marrow, blood, lymphatic vessels, reproductive organs, kidneys, linings of cavities Endoderm - linings of digestive and respiratory tract, urinary bladder and urethra –Yolk sac development - blood cell formation and stem cells –Week 3 - allontois forms - forms blood cells and becomes umbilical arteries and veins

Week 4 Heart beating Head and jaw Limb buds Gas and nutrient exchange through placenta

Week 8 Amnion develops - amniotic fluid Umbilical cord Embryo is 30 millimeters in length and all systems are formed

Fetal Stage of development 8th week Rapid Growth and change in proportions Bones begin to ossify 5th month - mother feels movement - lanugo and sebum cover skin Final trimester - brain cells and organs mature 40 weeks - parturition - birth

Birth process

Postnatal Period Changes in mother: –Production and secretion of milk Prolactin no longer inhibited after birth First milk – colostrum –Watery fluid rich in proteins and antibodies Milk let down triggered by oxytocin Human milk is the best possible food for babies –Hormonal changes – depression (post-partum)

Neonatal period of development Changes in infant Birth - 4 weeks –First breath – must be forceful to inflate lungs for first time –Surfactant in full term newborn reduces surface tension Live off fat for 2-3 days –Susceptible to dehydration – homeostatic mechanism of kidneys not yet fully functioning Changes in fetal circulation –Umbilical vessels constrict, several holes close, between heart and liver bypass. –Occur during first fifteen minutes after birth, but it may take longer for foramen ovale to close between right and left parts of the heart. (foramen ovale bypassed lungs during prenatal development.)