Reproductive System

Chapter 27

MALE REPRODUCTIVE SYSTEM

Male Reproductive Anatomy Overview

• Testes in scrotum• Epididymis• Vas deferens• Ejaculatory duct• Urethra (3 parts)• Seminal vesicles• Prostate• Bulbourethral glands

http://www.everydayhealth.com/mens-health-pictures/male-anatomy-and-the-reproductive-system.aspx , with illustrations by Catherine Delphia

Anatomical Structures• Scrotum (5)

– Superficial sac for testes = 3° lower than core• Requirement w/ sperm production

– Muscles facilitate• Dartos: smooth muscle wrinkles for insulation• Cremaster: ontracts w/ cold = pulled closer; hot = opposite

• Testes (1)– Two tunics

• Tunica vaginalis: outer from peritoneum• Tunica albuginea: inner fibrous layer that divides into lobules

– Seminiferous tubules where spermatogenesis occurs• Surrounded by testosterone producing interstitial cell• Converge at rete testes before epididymis

– Testicular cancer: most common in young; regular self-exam increases early detection

Anatomical Structures (cont.)

• Penis (2)– Root w/ free shaft ending in glans penis

• Foreskin (prepuce) covers; removed w/ circumcisition– 3 regions of erectile tissue

• Corpus spongiosum (1) surrounds urethra; forms glans• Corpora cavernosa (2)

• Epididymis (3)– Stores non-motile sperm till maturation

• ~ 20 days swimmers• Released w/ejaculation

– Stereocilia absorbs excess fluids and supplies nutrients

Anatomical Structures (cont.)

• Vas deferens– W/ blood, nerves, and lymph to testes = spermatic cord– Peristalsis propels sperm– Joins seminal vesicle ejaculatory duct (4)– Vasectomy: male sterilization technique: ~ 50% reversal

success• Urethra– Urinary and reproductive function– 3 parts (prostatic, membranous, and spongy)

Anatomical Structures (cont.)• Seminal vesicles

– ~60% semen– Viscous, alkaline solution, w/fructose (ATP) and prostaglandins (down cervical mucus

viscocity)• Prostate

– ~33% semen– Milky, acidic solution w/ citrate, enzymes, and specific antigens– Hypertrophy: difficulty urinating or having an erection– Prostatis: inflammation

• Bulbourethral gland– < 5%– Thick, alkaline mucus to neutralize traces of urine & lubricate

• Semen• Alkalinity ~ 7.3 – 7.7

– Neutralizes vagina– Survival < 48 hrs after ejaculation– Sterility: reduced production of sperm

Male Sexual Response: Erection

• PNS releases NO = penis engorges w/ blood– Relaxes penile tissue– Vasodilate vascular supply

• Corpora cavernosa compresses vein drainage to maintain

• Corpus spongiosum maintains urethral opening during ejaculation

• PNS signals bulbourethral secretions to lubricate glans

Male Sexual Response: Ejaculation

• Spinal reflex of SNS triggers• Climax/ orgasm– Bladder sphincter constricts urine retention– Contraction of ducts and accessory glands– Penile muscles rapidly contract to propel

• Resolution follows– Muscular and physiological relaxation– Latent period prevents consecutive erection

• Erectile dysfunction: inability to attain an erection

Gametogenesis

• Nuclear division reduces chromosome number to produce gametes– Humans w/ 23 pairs (46) homologous

chromosomes– Gametes w/23 chromosomes = haploid (n)– Gamete + gamete = fertilization = diploid (2n)– Occurs in gonads (testes and ovaries)

• 1 parent cell produces ‘4’ daughter cells

Meiosis• Phases mirror mitosis (pro-, meta-, ana-, telophase)• Replication of DNA prior to• Meiosis I

– Homologs synapse and crossing over occurs at chiasma (prophase I)– 1 cell 2 cells w/ ½ DNA amount

• Meiosis II– Chromatids separate– Resembles mitosis

• Introduces genetic variability• Nondisjunction w/ failure to separate in anaphase I or II

– Chromosomal number abnormalities

Spermatogenesis• Formation of sperm– ~ age 14 to death– ~400 million a day

• Spermatogonium (stem) divides into multiple primary spermatocytes (mitosis)

• Primary to secondary spermatocytes (meiosis I)• Secondary to spermatids (meiosis II) Spermiogenesis:

Spermatids to sperm (fig 27.8)– Circular cell to 3 distinct regions

• Head w/ acrosome (genetic), midpiece (metabolic), tail (locomotor)

Spermatogenesis (cont.)

Hormonal Regulation• Hypothalamus: GnRH AP: FSH/LH testes (review)

– FSH: indirect spermatogensis stimuli by maintaining high [testosterone]

– LH: prods seminiferous tubules to produce testosterone• Spermatogenesis push

• High [testosterone] effects other targets– Maturation of sex organs– Development/ maintenance of 2° sex characteristics– Stimulates sex drive– Inhibits GnRH

• Inhibin up w/ increase [sperm] inhibits FSH/LH release

FEMALE REPRODUCTIVE SYSTEM

Female Reproductive Anatomy Overview

• Ovaries• Uterine tubes• Uterus• Vagina• External

genitalia• Mammary

glands

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Anatomical Structures

• Ovaries– Held in place by ligaments (ovarian, broad, and

mesovarium)– Two tunics

• Germinal epithelium: cuboidal cells of peritoneum• Tunica albuginea: inner fibrous layer

– Contain sac-like follicles w/ oocytes• Uterine tubes (Oviducts)– Fimbriae ‘sweep’ ovulated 2° oocyte into infundibulum to

ampulla for fertilization– Ectopic pregnancy: fertilization outside uterine tube– Pelvic inflammatory disease: bacterial infection

Anatomical Structures (cont.)• Uterus

– 3 walled organ (peri-, myo-, and endometrium)– 3 regions (fundus, body, cervix)

• Isthmus, cervical canal, external and internal os– Endometrial layers

• Stratum functionalis: cylic changes w/ ovarian hormones; sloughed ~ every 28days• Stratum basalis: forms new functionalis; unresponsive to ovarian hormones

– Cervical cancer– Prolapse: uterus sinks to external vagina from muscle weakening

• Vagina– 3 layers (fibroelastic adventitia, smooth muscularis, strat. squam. mucosa w/

rugae)– Passageway for birthing and menses– Acidic environment impairs sperm mobility and resist bacteria

Anatomical Structures (cont.)• External Genitalia

– Mons pubis– Labia majora and minora– Clitoris

• Glans and prepuce• Corpora cavernosa only

– Vestibule• Vestibular glands lubricate and moisten

• Mammary glands– Present in males & females, but fxn in females only– Stimulated by PRL and oxytocin– Areola w/sebaceous glands (minimize chapping) and nipple– Suspensory ligaments naturally support– Milk in lobules from alveoli cells to lactiferous duct and collects in lactiferous sinus

in nipple w/ nursing

Oogenesis• Formation of ova (egg)

– Fetus to birth and puberty to menopause– 7 million to 2 million and 250, 000 to < 500

• Oogonia (stem) divide into multiple primary oocytes in primordial follicles (mitosis)

• Primary start meiosis, but stall at prophase I (birth)• LH surge activates multiple, but only 1 finish meiosis I

– First polar body– Secondary oocyte stalls at metaphase II before ovulation

• Fertilization completes meiosis II– One ovum (functional)– Second polar body

Oogenesis (cont.)

Comparing Gametogenesis

Oogenesis• Mitotic division completed

at birth

• 1 functional ova and 3 polar bodies (degenerate)

• 1 ova per cycle (~ 28 days)

Spermatogenesis• Mitotic division puberty to

death

• 4 functional sperm

• Continuous production

Ovarian Cycle

• Maturation of ova events– Typically 28 days– 21 – 40 more common

• Follicular phase (variable)– Follicle grows– Day 1 to 14

• Luteal phase (constant)– Corpus luteum activity– Day 14 -28

• Ovulation is midcycle

Follicular Phase• Primordial to primary follicle

– Outer sim. squa outer sim. cub. • Primary to secondary follicle

– Sim. cub strat. squam (granulosa cells)– Granulosa and thecal cells secrete estrogen– Zona pellucida encapsulates oocyte– Antrum forms

• Secondary to vesicular follicle– Growing antrum isolates granulosa corona radiata– Bulges at surface for ovulation

• Fraternal vs. identical twins– Meiosis I completed

• Fig 27.18

Luteal Phase

• Corpus luteum formed after ovulation– Antrum w/ blood– Granulosa cells increase size– Progesterone (some estrogen) secretion starts

• ~ 10 days till degeneration– Scar, corpus albicans, results– Pregnancy prevents • Hormone secretion as bridge w/ placenta (~3 months)

Ovarian Cycle Hormonal Control• GnRH LH and FSH estrogen and progesterone

– Estrogen inhibits GnRH (childhood)– Hypothalamus less responsive approaching puberty– Adult pattern reached = menarche

• Day 1: GnRH stimulates LH and FSH release– Stimulate follicle growth, development, and estrogen release– Rising estrogen

• Inhibits LH and FSH release• High levels produce LH surge primary to secondary oocyte

• Day 14: LH surge triggers ovulation– Corpus luteum formation (estrogen, progesterone, and inhibin)– Inhibit LH and FSH

• Days 26 – 28: ovarian hormones drop– LH and FSH NOT inhibited– Cycle repeats

• Fig 27.19

Uterine Cycle• Cyclical changing of endometrium

– FH and FSH govern– Linked w/ ovarian cycle

• Days 1 – 5– Menses, ‘sloughing off’ of endometrium – Ovarian hormones low; LH and FSH rising

• Days 6 - 14– Proliferative phase rebuilds endometrium– Estrogen increases cervical mucus thins

• Days 15 -28– Secretory phase preps uterus for embryo– Progesterone increase creates cervical plug from cervical mucus

Ovarian and Uterine Cycles

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