Physiology Unit 4 REPRODUCTIVE PHSYIOLOGY

Gonads Gonads have 2 func7ons Gametogenesis Spermatogenesis Oogenesis Secrete steroid hormones Testosterone Estrogens (3 forms) Estradiol, produced by ovaries, placenta Progesterone

Sex Hormones Males Sex Hormones Androgens general masculinizing ac7ons Produced by adrenal cortex DHEA is an example Testosterone Produced by testes Maintains male reproduc7ve func7on Female Sex Hormones Estrogens Estradiol Primary form of estrogen produced Produced by ovaries and placenta Estrone Estriol Produced by ovaries and placenta Usually only in pregnant women Produced by the placenta Progesterone Produced by ovaries and placenta

Male Reproduc7ve Physiology Func7on of the testes Meiosis Forma7on of sperm Spermatogenesis Matura7on of sperm Emission, ejacula7on Expulsion of sperm Secre7on of male sex hormone Testosterone

Hormonal Control of the Testes Hypothalamus (Brain) Pulsa7le secre7ons of GnRH Every 90 minutes Anterior pituitary FSH and LH released by same cell type Also show pulsa7lity Testes Testosterone secre7on by Leydig cells s7mulated by LH

Sertoli Cells Ac7vated by FSH and testosterone Regulate the microenvironment of developing sperm Forms the blood- tes7s barrier Nourish developing sperm Secrete androgen binding protein (ABP) Maintains high concentra7on of testosterone in lumen of seminiferous tubules Prevents immune system from atacking developing sperm cells Phagocytosis of defec7ve sperm

Spermatogenesis Spermatogenesis takes 64 days Males produce 30 million sperm/day Differen7a7on requires extensive cellular remodeling

Puberty in Males Reproduc7ve organs mature and reproduc7on becomes possible 12-16 years of age in males First signs of puberty are due to increased secre7ons of adrenal androgens (ACTH controlled) All other developments in puberty reflect the increased ac7vity of the hypothalamic- anterior pituitary- gonadal axis

Puberty in Males Increased GnRH secre7on at puberty Increased secre7on of FSH, LH Testosterone Changes in accessory reproduc7ve organs Ducts, glands, penis Development of male secondary sexual characteris7cs Sex drive

Reflex Pathways for Erec7on Under res7ng condi7ons sympathe7c input dominant NE causes arteriole smooth muscle to contract Vasoconstric7on of blood vessels supplying blood to erec7le 7ssue During erec7on sympathe7c input is inhibited Neurons release NO NO causes arteriole smooth muscle relaxa7on Vasodila7on of blood vessels supplying blood to erec7le 7ssue

Ejacula7on Primarily a spinal reflex (spinal nerves S2, S3, S4) Divided into 2 stages 1. Sperm and glandular secre7ons into the urethra (emission) 2. Semen is expelled from the urethra (ejacula=on) Average volume 3 ml 300,000,000 sperm

Seminal Fluid Seminal Glands Seminal Glands (Vesicles) Produces majority of seminal fluid Produces a protein, semenogelen Semenogelen encases ejaculated sperm in a protec7ve gel to protect it from the acidic environment in the vagina Secre7ons contain fructose, nourishes sperm cells

Prostate Gland Seminal Fluid Prostate Gland Produces about 1/3 volume of seminal fluid Produces an alkaline fluid Produces Prostate Specific An7gen (PSA) PSA is a protease that cleaves semenogelen PSA is inhibited by high [zinc], present in semen Vagina has low [zinc], ac7vates PSA PSA cleaves semenogelen allowing the sperm to move freely Capacita7on

Female Reproduc7ve Physiology Func7ons of the ovaries Meiosis Forma7on of ova (eggs) Oogenesis Matura7on of the oocyte Ovula7on Expulsion of an oocyte Secre7on of female sex hormones Estrogens Progesterone

Oogenesis Early fetal development Oogonia undergo many rounds of mitosis 7 months gesta7on 6-7 million oogonia Mitosis ceases At birth 2-4 million oocytes remain (atresia: programmed cell death) At Puberty Ovaries become ac7ve 2-400,000 oocytes remain (atresia) Approximately 400 ova will be ovulated (atresia)

Oogenesis If the egg is fer7lized, then meiosis II occurs in the fallopian tube Ovum retains almost all of the cytoplasm 2nd polar body released, again much smaller than ovum Meiosis II completed ager fer7liza7on

Granulosa Cells Primary cells of the follicle Have receptors for FSH Regulate the microenvironment in which the ovum develops Secrete estrogen (estradiol) Produce one or more factors that act on primary oocytes that maintain them in meio7c arrest Follicle grows by mitosis of the granulosa cells Secrete fluid that forms and fills the antrum

Follicle Development 1. Throughout infancy and early childhood The progression/growth of some primordial follicles occurs 2. At the beginning of the each menstrual cycle 10-25 of those follicles begin to develop into larger follicles 3. About one week into the cycle Only one dominant follicle will develop into a Graafian follicle Non- dominant follicles enlarge and undergo atresia The eggs within the degenera7ng follicles die

Follicle Development

Ovula7on Triggered by LH Follicle bulges out from the surface of the ovary as it enlarges (1.5 cm) Ovula7on occurs when the thin walls of the follicle and the ovary rupture A Graafian follicle ruptures and expels: Secondary oocyte Zona pellucida (sperm cell binding) Corona radiata (2 or 3 layers of granulosa cells)

Corpus Luteum The follicle collapses ager the discharge the the follicular fluid and the egg Granulosa cells enlarge forming the corpus luteum Secretes estrogen, progesterone If implanta7on does not occur, the corpus luteum reaches is maximum size within 10 days, then degenerates (apoptosis) to form the corpus albicans

Hormonal Control of Ovaries Hypothalamus Pulsa7le secre7ons of GnRH Frequency and amplitude of these pulses during a 24 hour period change over the course of the menstrual cycle Anterior pituitary FSH and LH Ovaries Estrogen Progesterone

Ovarian Cycle

Puberty in Females Average age of onset of puberty is 10-12 Increased secre7on of GnRH results in an increasing levels of estrogen Development of secondary sexual characteris7cs and the onset of the menstrual cycle Increasing levels of lep=n Secreted by adipocytes S7mulates secre7on of GnRH

Menstrual Cycle Menstrual Phase Day 1 is the first day of menstrual flow Endometrium degenerates Prolifera7ve Phase End of menstrua7on to ovula7on Secretory Phase Ovula7on to the onset of the next menstrual phase Changes in uterus caused by estrogen and progesterone

Pregnancy Introduc7on of sperm must occur between 5 days before and 1 day ager ovula7on Sperm viable for 4-6 days Egg viable for 1-2 days

Sperm Capacita7on Sperm cells cannot fer7lize the egg un7l they have resided in the female tract for several hours Acted on by secre7ons of the female reproduc7ve tract called capacita=on Changes in the patern of tail movement allow sperm to propel forward in strong surges Sperm s plasma membrane becomes altered so that it may fuse with the plasma membrane of the ovum

Only 100-200 sperm reach the egg Many sperm bind to the zona pellucida Zona pellucida proteins act as receptors for sperm surface proteins Binding triggers the acrosome reac=on Vesicles containing diges7ve enzymes released from sperm and digest the zona pellucida Fer7liza7on

Implanta7on and Placenta Forma7on Trophoblast cells (fetal cells) produce human chorionic gonadotropin (hcg) Maintenance of corpus luteum (prevents menstrua5on) Promotes angiogenesis in uterine vasculature Blocks immune/macrophage ac7on from mother on foreign, invading placental cells Blood 7ters double every day un7l 10 th week 10th week Decline in hcg Placenta becomes secretory 5th- 6th week Secretes progesterone (maintains endometrium)

Placental Exchange of Molecules No mixing of maternal and fetal blood Diffusion O 2 & CO 2 Nutrient molecules & waste products High metabolic rate in placenta U7lizes 1/3 maternal oxygen & glucose Rate of protein synthesis exceeds liver

Hormonal Changes During Pregnancy