The Reproductive Systems Chapter 23

Male Reproductive System Organs: testes, ducts, glands & supporting structures Ducts: epdidymis, ductus deferens, ejaculatory ducts & urethra Glands: seminal vesicles, prostate, bulbourethral glands Supporting structures include scrotum & penis

Figure 23.1

Scrotum Pouch that supports the testes Septum separates into separate sections for each testis Sperm requires temperatures 2-3 o C below body temperature allows raising and lowering testes to adjust temperature

Testes Paired oval glands Develop on embryo’s posterior wall and descend into scrotum –Starts in 7 th month lobules containing seminiferous tubules Lined with spermatogenic cells: spermatagonia & sertoli cells

Figure 23.2a

Figure 23.2b

Spermatogenesis Stages: meiosis I, Meiosis II, spermiogenesis Occurs in seminiferous tubules Cell types involved: spermatagonia, sertoli cells & interstitial cells (leydig cells) move through rete testes ->epididymis

Meiosis Cells have 23 pairs of chromosomes –diploid= paired homologous chromosomes Gametes are Haploid: –Unpaired chromosomes Meisosis is the process by which this can happen Required for gamete production

Spermatogenesis stages Takes ~65-75 days from first division to release Spermatogonium divides: mitosis –One cell is stem cell other differentiates into primary (1 o ) spermatocyte 1. Meiosis I. chromosomes replicate –Line up as pairs of homologous chromosomes –Chromosomes twist and some exchange of material between chromosomes can occur –Each homologous pair separates and a member moves to opposite end of cell  –After cell division each cell is haploid

Stages (cont.) The cells from meiosis I are : secondary spermatocytes –Each cell is haploid- has two copies of each chromatid Meiosis II: divide again- –One copy of each chromatid in each new cell Cells are: spermatids

Stages (cont.) Spermiogenesis- each spermatid develops into a sperm cell Process requires support of Sertoli cell –Often called “nurse cell”

Figure 23.3

Spermatozoa Structure ~300 million /day –Life time ~ 48 hrs in female tract Structure: Head, middle, tail tail- flagellum = motility Middle - mitochondria = energy Head-chromosomes + acrosomal cap acrosome-enzymes-> penetrating egg

Figure 23.4

Hormonal Control At Puberty- hypothalamus  GnRH  Pituitary  LH & FSH LH  Leydig cells  testosterone  Negative feedback to suppress LH & GnRH FSH + testosterone stimulate spermatogenesis Sertoli cells  inhibin  inhibits FSH release  optimum sperm production

Figure 23.5

Androgen Effects Prenatal- male pattern of development: –Male ducts, descent of testes, external genitals & brain regions Puberty: enlargement of organs, secondary characteristics: –Muscular & skeletal growth, hair patterns, thickening of skin Sexual function: sexual behavior, spermatogenesis & libido Stimulation of anabolism: stimulate protein synthesis & muscle & bone growth

Ducts- Sperm route Epdidymis  vas (ductus) deferens  ejaculatory duct (by seminal vesicles)  urethra in prostate pass bulbourethral glands (alkaline + mucus fluid)  penis and ejaculation

Figure 23.6

Accessory Glands Seminal vesicles- seminal fluid- –Fructose (sperm ATP production –+ alkalinity (neutralize acid in tracts) –+ prostaglandins-activation of sperm Prostate- surrounds upper urethra –Increases volume + adds antibiotics Bulbourethral glands: –More alkalinity + mucus fluid

Penis Contains urethra- root, body & glans penis –Passage for semen & urine Root- attached portion Body- 3 cylindrical masses  erectile –Dorsal – Corpora Cavernosa Penis –Midventral- Corpus Spongiosum penis- contains urethra Glans penis has external urethral oriface Uncircumcised glans covered by prepuce

Arousal & Ejaculation Parasympathetic impulses  erection –Dilation of penile arteries –Volume compresses veins so outflow is slowed Ejaculation is a Sympathetic reflex –Peristaltic contractions in ductus deferens, seminal vesicles, ejaculatory ducts & prostate  emission –Sphincter at urinary bladder closes –Forceful release of semen from urethra

Female Reproductive System Ovaries: paired organs- produce –secondary oocytes  ova (after fertilization) –Hormones: progesterone & estrogens –From same embryonic tissue as testes uterine (fallopian) tubes & uterus vagina External organs (vulva or pudendum)

Figure 23.6

Histological Structure Germinal epithelium- covers surface Ovarian cortex: connective tissue containing follicles Follicle; oocyte + surrounding cells –Surrounding cells nourish oocyte & produce hormones –Grows during maturation  Graafian follicle  ovulation Post ovulation  corpus luteum  –Progesterone, relaxin & inhibin

Figure 23.7

Oogenesis Begins before birth- –Oocytes not continually produced Meiosis I- start before birth & finish at puberty –during fetal development  form oogonia –Before birth some  primary oocytes –Monthly hormones  some to complete meiosis I Two uneven haploid cells= secondary oocyte & polar body (discarded)

Oogenesis (cont.) Secondary oocyte has most of cytosol Then begins meiosis 2 & stops Then ovulation  into uterine tube If fertilization then meiosis II is completed  ovum + 2 nd polar body Nuclei of sperm & ovum unite  Diploid zygote

Figure 23.8

Uterine Tubes Two tubes- extend laterally from uterus End in fringe  Fimbriae Fimbriae sweep secondary oocyte into tube Oocyte moved by cilia lining wall Zygote reaches uterus in ~7 days

Uterus Pathway for sperm & site of implantation Fundus -Dome-shaped area above tubes= Body – tapering central portion Cervix- narrow opening into vagina Uterine cavity- interior of body

Vagina extends from exterior to cervix Receptacles for penis and outlet for menstrual flow Fornix- recess surrounds cervix Acid environment- prevents bacterial growth Smooth muscular layer- adjusts for intercourse or birth Thin membrane fold can cover vaginal orifice = hymen

Figure 23.9

Perineum & vulva Perineum: Diamond-shaped area between thigh & buttocks of both males & females Vulva or pudendum = external genitalia Mons pubis- elevation of adipose tissue labia majora- extends back from mons pubis –Same fetal tissue as scrotum Labia minora- internal to majora

Perineum & vulva (cont.) Clitoris- small cylindrical mass of erectile tissue & nerves –Also contains prepuce & glans Vestibule: between labia minora External urethral oriface- anterior to vaginal oriface Paraurethral glands- either side of urethra –Same embryonic tissue as prostate –Secretes mucus Greater vestibular glands- adds to mucus –Camparable to bulbourethral glands

Figure 23.10

Mammary Glands Modified suduriferous glands Nipple- pigmented projection with openings Areola- surrounds nipple Internally lobes  lobules  alveoli = milk secreting glands –Matures at puberty Lactation = synthesis, secretion & ejection of milk

Figure 23.11

Female Reproductive Cycle days- cycles in both ovaries & uterus Ovarian cycle= maturation of follicle, ovulation & corpus luteum formation Uterine Cycle= menstrual cycle –controlled by hormones from ovary –Estrogens  growth of endometrium Progesterone supports endometrium for implantation Combine cycles = Reproductive cycle

Figure 23.12

Hormonal Regulation GnRH (hypothalamus) controls GnRH  FSH & LH FSH  follicle growth & estrogen secretion High estrogen  LH surge  ovulation LH supports corpus luteum  progesterone & estrogen secretion + relaxin & inhibin Inhibin  decreased FSH release

Hormones Estrogen: –Development & maintenance of reproductive structures & secondary characteristics –  protein synthesis & growth –Lower blood cholesterol level Progesterone maintains myometrium for implantation Relaxin= relaxes uterus- inhibits myometrium Inhibin- inhibits FSH release

Phases of Cycle Menstrual phase: ~1 st 5 days of cycle –Several Ovarian follicles enlarge –Decreased progesterone & estrogen  uterine arteries constrict  endometrium sloughs off Preovulatory- between menstruation & ovulation –Ovaries: follicles grow & secrete estrogen & inhibin  one dominates –Uterus: growth of new endometrium

Phases of Cycle (cont.) Ovulation –Release of 2 o oocyte with LH surge Postovulatory- –Ovaries: follicle collapses  corpus luteum (luteal phase) –If no fertilization   FSH & LH  corpus albicans & decreased Progesterone  menstruation

Phases of Cycle (cont.) If fertilization & division  human chorionic Gonadotrophin (hCG)  stimulates corpus luteum  secretion Uterus: Progesterone & estrogens  complete development of uterus for implantation

Figure 23.13

Birth Control Methods Surgical: vasectomy in males –ductus deferens segment removed Tubal ligation in females –Close uterine tubes Chemical interference –oral hormones, implants, injections, spermicide Blocking physically –IUD, condoms, cervical cap Timing –temperature, mucus charting, calendar Abortion

Aging Puberty- pulses of LH & FSH  Rise in sex steroids  –Growth & secondary characteristics –start of female reproductive cycle follicles become exhausted  Menopause –estrogen secretion declines  –lose feedback on pituitary  high FSH & LH  –Decline in estrogen supported functions In males- slower decline of function