Anatomy & Physiology Chapter 27 Reproductive System PDF

ANATOMY & PHYSIOLOGY Chapter 27 THE REPRODUCTIVE SYSTEM PowerPoint Image Slideshow REPRODUCTIVE SYSTEM Primary sex organs (gonads) = testes and ovaries Produce sex cells = (gametes) = egg/sperm Secrete steroid sex hormones Androgens (males) Estrogens and progeste...

ANATOMY & PHYSIOLOGY Chapter 27 THE REPRODUCTIVE SYSTEM PowerPoint Image Slideshow REPRODUCTIVE SYSTEM Primary sex organs (gonads) = testes and ovaries Produce sex cells = (gametes) = egg/sperm Secrete steroid sex hormones Androgens (males) Estrogens and progesterone (females) MALE REPRODUCTIVE SYSTEM THE TESTES Sperm are Produced in Seminiferous tubules Interstitial (Leydig) cells outside the seminiferous tubules produce testosterone EPIDIDYMIS Nonmotile sperm enter, pass slowly through, and become motile During ejaculation the epididymis contracts, expelling sperm into the ductus deferens URETHRA Conveys both urine and semen (at different times) ACCESSORY GLANDS: PROSTATE Encircles part of the urethra inferior to the bladder Secretes milky fluid: Contains citrate, enzymes, and prostate-specific antigen (PSA) Plays a role in the activation of sperm ACCESSORY GLANDS: SEMINAL VESICLES Produces viscous alkaline seminal fluid Fructose, coagulating enzyme (vesiculase) And prostaglandins 60-70% of the volume of semen Neutralizes female urogenital mucous. Provides energy for sperm BULBOURETHRAL GLANDS (COWPER’S GLANDS) Pea-sized glands inferior to the prostate Prior to ejaculation, produce thick, clear mucus Lubricates the glans penis Neutralizes traces of acidic urine in the urethra SEMEN(EJACULATE) Mixture of sperm and accessory gland secretions  GAMETOGENESIS Sequence of events that produces sperm or ova (gametes) Most body cells are diploid (2n) and contain 46 chromosomes Two sets of chromosomes (one maternal, one paternal) 23(n) pairs of homologous chromosomes 46(2n) total 23 from Mom, 23 from Dad GAMETOGENSIS Gametes are haploid (n) and contain 23 chromosomes 2n embryo n n n n n oocyte + n sperm n n oocyte  MEIOSIS 1 round of DNA replication Gamete formation involves meiosis 2x Nuclear division in the gonads in which the number of chromosomes is halved (from 2n to n) 1 round of DNA replication 2x 2x followed by 2 consecutive cell divisions (meiosis I and II) Produces four daughter cells Introduces genetic variation  MEIOSIS IN MORE DETAIL More detail https://commons.wikimedia.org/wiki/File:Meiosis_Stages.svg 2n 2x 2n By Rdbickel - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=49599354 https://en.wikipedia.org/wiki/Meiosis CRASH COURSE VIDEO FROM YOUTUBE Link https://youtu.be/qCLmR9-YY7o  SYNAPSIS (CROSSING OVER) Synapsis = process that allows for recombination of genes Homologous chromosomes pair up at Metaphase plate Form a structure called a tetrad by tangling together (like twister) Exchange sections of chromosomes CROSSING OVER Creates NEW COMBINATIONS of genes. recombination One of the advantages of sexual By Rdbickel - Own work, CC BY-SA 4.0, reproduction https://commons.wikimedia.org/w/index.php? curid=49599354 PRACTICE QUESTION How many times is DNA replicated in meiosis? A. 1 B. 2 C. 3 D. 4 PRACTICE QUESTION How many cell divisions are there in meiosis? A. 1 B. 2 C. 3 D. 4 PRACTICE QUESTION What is the benefit of crossing over? A. More genetic stability B. Generation of random positive mutations C. Creation of new genes D. New combinations of genes passed on to offspring  SPERMATOGENESIS Meiosis occurs in spermatogenesis. In meiosis, 4 daughter cells each with half the number of chromosomes of the parent cells are formed. Spermatogonia(stem cells) form spermatocytes(2n) Spermatocytes form spermatids(n) ROLE OF SUSTENTACULAR CELLS(SERTOLI CELLS) Surround developing cells Provide nutrients and signals to dividing cells Dispose of excess cytoplasm sloughed off during spermiogenesis Tight junction Developing sperm ROLE OF SUSTENTACULAR CELLS Tight junctions form a blood-testis barrier Prevents sperm antigens from escaping into the blood where they would activate the immune system Because sperm are not formed until puberty, they are absent during immune system development, and would not be recognized as “self” Tight junction Developing sperm HYPOTHALAMUS PITUITARY GONADAL (HPG) AXIS 1. Hypothalamus releases gonadotropin- releasing hormone (GnRH) 2 2. GnRH stimulates the anterior pituitary to secrete FSH and LH  HPG AXIS 3. LH stimulates interstitial cells to release testosterone 4. FSH causes sustentacular 6 cells to release androgen- 2 binding protein (ABP), which binds testosterone 5. Testosterone stimulates spermatogenesis 5 6. Inhibin/test provide negative feedback 4 3 And keeps LH/FSH @ proper level FEMALE REPRODUCTIVE SYSTEM OOGENESIS Production of female gametes, Oocytes Takes place in ovaries An oocyte is contained within the structure called a follicle in the ovary.  OOGENESIS Begins in the fetal period Oogonia (2n ovarian stem cells) multiply by mitosis and store nutrients Oogonia all develop into primary oocytes Females are born with all the Oocytes they will need!! Primary oocytes begin meiosis but stall in prophase I (no division)  OOGENESIS After puberty, a few primary oocytes are activated each month. Only one primary oocytes is selected each month to resume meiosis I Ovulation triggers completion of meiosis I –results in Secondary oocyte First polar body  OOGENESIS The second meiotic division (meiosis II) takes place just after ovulation. The secondary oocyte is arrested in metaphase II when ovulated If penetrated by sperm the secondary oocyte completes meiosis II, yielding Ovum (the functional gamete) Second polar body FOLLICULAR DEVELOPMENT Primordial follicle: are present in female newborns. Primary follicle: Secondary follicle Vesicular (teriary)-prior to ovlulation Fluid-filled antrum forms; follicle bulges from ovary surface OVULATION Ejection of the oocyte Corpus luteum develops from ruptured follicle after ovulation PRACTICE QUESTION The stem cell for spermatogenesis is a ______________. A. Spermatid B. Spermatocyte C. Spermatogonium PRACTICE QUESTION At birth ovaries will always have all the _____________ that they will need. A. Oogonia B. Primary oocytes C. Secondary oocytes D. Ova FEMALE MENSTRUAL CYCLE Ovarian Cycle Events in the ovary Controlled by Pituitary Gonadotropins Release of Ovarian Hormones Uterine Cycle Changes in Uterine Endometrium Controlled by Ovarian Hormones OVARIAN CYCLE Follicular phase: period of follicle growth (days 1–14) promoted by Follicle Stimulating Hormone(FSH) Ovulation occurs midcycle Triggered by Luteinizing Hormone(LH) Luteal phase: period of corpus luteum activity (days 14–28) promoted by LH Corpus luteum secretes progesterone LUTEAL PHASE If no pregnancy, the corpus luteum degenerates into a corpus albicans in 10 days If pregnancy occurs, corpus luteum produces progesterone until the placenta takes over at about 3 months ESTABLISHING THE CYCLE During childhood, until puberty Ovaries secrete small amounts of estrogens Estrogen inhibits release of GnRH At puberty Leptin from adipose tissue decreases the estrogen inhibition Lean athletes – late menarche GnRH, FSH, and LH are released In about four years, an adult cyclic pattern is achieved and menarche occurs UTERINE (MENSTRUAL) CYCLE Cyclic changes in endometrium in response to ovarian hormones Three phases 1. Days 1–5: menstrual phase 2. Days 6–14: proliferative (preovulatory) phase 3. Days 15–28: secretory (postovulatory) phase (constant 14-day length)  UTERINE CYCLE Proliferative phase Higher estrogen levels prompt generation of new functional layer, increase the synthesis of progesterone receptors in endometrium, which leads to thickening the endometrium. Glands enlarge and spiral arteries increase in number  UTERINE CYCLE Secretory phase Progesterone levels rise, causing The uterine lining to stop thickening and become more receptive to implantation. Glandular secretion of nutrient-rich secretions, such as glycogen Formation of the cervical mucus plug UTERINE CYCLE If fertilization does not occur Corpus luteum degenerates Progesterone and estrogen levels fall Endometrial cells begin to die Menses If fertilization Placenta produces HCG(human chorionic gonadotropin) that maintains the corpus luteum, and progesterone levels stay high. HORMONE: OVERVIEW Ovarian Hormones Estrogen – follicles, corpus luteum Progesterone – corpus luteum Pituitary Hormones Luteinizing Hormone Follicle Stimulation hormone ESTABLISHING THE CYCLE During childhood, until puberty Ovaries secrete small amounts of estrogens Estrogen inhibits release of GnRH At puberty Leptin from adipose tissue decreases the estrogen inhibition Lean athletes – late menarche GnRH, FSH, and LH are released In about four years, an adult cyclic pattern is achieved, and menarche occurs  HORMONAL INTERACTIONS DURING A 28-DAY OVARIAN CYCLE Day 1: Estrogen and Progesterone are low Slight rise in LH and FSH promoting follicular growth HORMONAL INTERACTIONS DURING A 28-DAY OVARIAN CYCLE Estrogen starts to rise Rise in Estrogen triggers rise in LH, which surges around day 12. Elevated estrogen (days 7-14) promotes endometrial proliferation  Rise in estrogen causes Sudden LH surge at day 12 Effects of LH surge Triggers ovulation!!! Completion of meiosis I Transforms ruptured follicle into corpus luteum HORMONAL INTERACTIONS DURING A 28-DAY OVARIAN CYCLE Functions of corpus luteum Produces progesterone, and estrogen Days 14-26 LH and FSH levels decline due to increase in progesterone Days 26–28: if fertilization does not occur, Corpus luteum degenerates. Progesterone declines and endometrium degrades HORMONE REVIEW!!!!! YOU NEED TO KNOW Estrogen – promotes thickening of endometrium - causes surge in LH on Day 14 Progesterone – promotes uterine secretions maintains endometrium causes decrease in LH FSH – stimulates ABP production in sertoli cells Promotes follicular development LH – trigger for ovulation and corpus luteum formation Testosterone production in males Testosterone – spermatogenesis Inhibin – negative feedback in males lowers GnRH BRIEF SUMMARY The full story is even MORE complicated than what I have shown you! PRACTICE QUESTION Which of the following would happen if fertilization does not occur at the end of the uterine cycle? A. Corpus luteum produces HCG (human chorionic gonadotropin) hormone. B. Progesterone and estrogen levels fall leading to menstruation. C. Endometrial cells thickened D. Luteinizing hormone and follicle stimulation hormone are released. PRACTICE QUESTION What hormone maintains the endometrium during the secretory phase? A. Estrogen B. Progesterone C. Luteinizing hormone MAMMARY GLANDS Are glands made up of fat, connective tissue, and glandular tissue that produces milk. In adult females, the breast contains 15–25 lobes of glandular tissue that radiate from the nipple. Each lobe has lobules that contain glandular units that produce milk. Areola: pigmented skin surrounding the nipple Suspensory ligaments: attach the breast to underlying muscle BREAST CANCER Usually arises from the epithelial cells of small ducts Risk factors include: Early onset of menstruation and late menopause No pregnancies or first pregnancy late in life Family history of breast cancer 10% are due to hereditary defects, including mutations to the genes BRCA1 and BRCA2 Risk factors still not a good predictor of occurrence